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Compelling evidence exists indicating that developmental programming influences ageing. Programming alters life-course phenotype in multiple organs, predisposing to diseases such as diabetes, obesity and cardiovascular disease that shorten lifespan. This review describes studies in rodents, the most commonly studied species, addressing interactions of programming challenges with ageing. We first consider ageing and programming of insulin function that has been clearly shown to decrease with age. It is important to evaluate ageing in pancreatic islets isolated from other systems. Studies discussed show premature pancreatic islet ageing resulting from both maternal under- and overnutrition. New ways to determine programming of adipose tissue and effects on fat storage are explored. Oxidative stress is a major factor that regulates ageing in tissues. Oxidative stress is discussed in relation to reproductive and cardiovascular ageing. Premature ageing is associated with both low and high glucocorticoid function. Both over and undernutrition have offspring sex-specific programming effects on life-course glucocorticoid concentrations. Evidence is provided that maternal age at conception affects offspring endocrine and metabolism ageing. Finally, the importance of matching foetal nutrition and energy availability with composition and energy content in the post-weaning diet is demonstrated. This mismatch can lead to a greatly shortened lifespan. General principles are discussed throughout. For example, sexual dimorphism of age-related outcomes can be marked. Accelerated ageing occurs early in life. Improving knowledge on programming ageing interactions will improve health span as well as lifespan. Finally, there are considerable similarities in outcomes programmed by maternal undernutrition and overnutrition., (© 2021 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd.)

Accumulating evidence has shown that lymphocytes modulate behaviour and cognition by direct interactions with the central nervous system. Studies have shown that reconstitution by adoptive transfer of lymphocytes from wild type into immune-deficient mice restores a number of neurobehavioural deficits observed in these models. Moreover, it has been shown that these effects are mostly mediated by T lymphocytes. Studies of adoptive transfer thus far have employed adult mice, but whether lymphocytes may also modulate behaviour during development remains unknown. In this study, neonate lymphocyte-deficient Rag2 -/- mice were reconstituted within 48 hours after birth with lymphoid cells from transgenic donors expressing green fluorescent protein, allowing for their identification in various tissues in recipient mice while retaining all functional aspects. Adolescent Rag2 -/- and reconstituted Rag2 -/- along with C57BL/6J wild-type mice underwent a series of behavioural tests, including open field, social interaction and sucrose preference tests. At 12 weeks, they were evaluated in the Morris water maze (MWM). Reconstituted mice showed changes in almost all aspects of behaviour that were assessed, with a remarkable complete rescue of impaired social behaviour displayed by adolescent Rag2 -/- mice. Consistent with previous reports in adult mice, neonatal reconstitution in Rag2 -/- mice restored spatial memory in the MWM. The presence of donor lymphocytes in the brain of neonatally reconstituted Rag2 -/- mice was confirmed at various developmental points. These findings provide evidence that lymphocytes colonize the brain during post-natal development and modulate behaviour across the lifespan supporting a role for adaptive immunity during brain maturation., (© 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Background: Supplemental oxygen is necessary in the respiratory support of very preterm infants, but it may contribute to bronchopulmonary dysplasia and an increased risk of poor lung function in later life. It is well established that hyperoxia can inhibit alveolarization, but effects on the developing conducting airways, which are important determinants of lung function, are poorly understood. It is possible that prolonged exposure of the immature lung to hyperoxic gas alters the development of small conducting airways (bronchioles), and that these effects may persist throughout life., Objectives: To examine the effects of neonatal inhalation of hyperoxic gas on the bronchiolar walls in adulthood., Methods: Neonatal mice (C57BL/6J) born at term inhaled 65% O2 from birth until postnatal day 7; thereafter, they were raised in room air until 10 months postnatal age (P10mo), which is advanced adulthood. Age-matched controls inhaled room air from birth. We investigated small conducting airways with a diameter between 105-310 µm., Results: At P10mo, bronchiolar walls of hyperoxia-exposed mice contained ∼18% more smooth muscle than controls (p < 0.05), although there was no effect on bronchiolar epithelium or collagen. Neonatal hyperoxia resulted in significantly fewer bronchiolar-alveolar attachments at P10mo (p < 0.05); this was accompanied by persistent simplification of the lung parenchyma, as indicated by greater mean linear intercept and less parenchymal tissue (p < 0.05)., Conclusions: Neonatal exposure to hyperoxia induces remodeling of the bronchiolar walls and loss of bronchiolar-alveolar attachments in adulthood, both of which could contribute to impaired lung function and airway hyper-reactivity., (© 2013 S. Karger AG, Basel.)

Apnea, the temporary cessation of respiratory airflow, is a common cause of intermittent hypoxia (IH) in premature infants. We hypothesized that IH elicits a stress response and alters glucose homeostasis in the neonatal rat. Rat pups were studied on postnatal day (PD) 2, 8, 10, 12, and 14. Pups were exposed to normoxia (control) or six cycles consisting of 30-s exposures to hypoxia (FiO2 = 3%) over a 60-min period. Blood samples were obtained at baseline, after the third cycle (~30 min), and after the sixth cycle (~60 min). Tissue samples were collected following the sixth cycle. Plasma ACTH, corticosterone, glucose, and insulin were analyzed at all ages. Hypothalamic, pituitary, and adrenal mRNA expression was evaluated by quantitative PCR in PD2, PD8, and PD12 pups. Exposure to IH elicited significant increases in plasma ACTH and corticosterone at all ages studied. The largest increase in corticosterone occurred in PD2 pups, despite only a very small increase in plasma ACTH. This ACTH-independent increase in corticosterone in PD2 pups was associated with increases in adrenal Ldlr and Star mRNA expression. Additionally, IH caused hyperglycemia and hyperinsulinemia at all ages. We conclude that IH elicits a significant pituitary-adrenal response and significantly alters glucose homeostasis. Furthermore, the quantitative and qualitative characteristics of these responses depend on developmental age.

Senescence could depress prenatal and postnatal capacities of mothers to invest in offspring. Longitudinal observations on the blue-footed booby (Sula nebouxii) revealed a quadratic effect of female age on fledgling production and cohort differences in rate of reproductive decline. By swapping clutches between females of different ages, we tested whether reproductive senescence is due to decline in egg quality or capacity to care. As laying mothers aged, egg size, ulna length of 5-day-old chicks, and ulna growth of second chicks up to age 30 days declined, and as rearing mothers aged, ulna growth and cellular mediated immune response of second chicks diminished. Oddly, senescent females (>11 years) produced more fledglings when rearing offspring of middle-aged females (8-11 years) than when rearing offspring of senescent or young females. Thus, senescence reduced egg quality and rearing capacities, and reproductive success of senescent mothers depended on prenatal effects associated with the age of the laying mother. Reproductive senescence of boobies may involve constraints on resources allocated to reproduction as well as adaptive adjustment of provision and care according to offspring value, implying that negative effects of senescence on offspring survival can be ameliorated by plasticity in postlaying or postnatal care.

The processing of odour mixtures by young organisms is poorly understood. Recently, the perception of an AB mixture, known to engage configural perception in adult humans, was suggested also to be partially configural in newborn rabbits. In particular, pups did not respond to AB after they had learned A or B. However, two alternative hypotheses might be suggested to explain this result: the presence in the mixture of a novel odorant that inhibits the response to the learned stimulus, and the unevenness of the sensory and cognitive processes engaged during the conditioning and the behavioural testing. We conducted four experiments to explore these alternative hypotheses. In experiment 1, the learning of A or B ended in responses to mixtures including a novel odorant (AC or BC). Experiment 2 pointed to the absence of overshadowing. Therefore, a novelty effect cannot explain the non-response to AB after the learning of A or B. In experiment 3, pups having learned A or B in AC or BC did not respond to AB. However, they generalized odour information acquired in AB to AC or BC in experiment 4. Thus, the balancing of the perceptual tasks between the conditioning and retention test does not enhance the response to the AB mixture. To sum up, the present experiments give concrete support to the partially configural perception of specific odour mixtures by newborn rabbits.

Previously, we reported that the hypoxic ventilatory response (HVR) in rats was weakest at postnatal day (P) P13, concomitant with neurochemical changes in respiratory nuclei. A major determinant of minute ventilation (Ve) is reportedly the metabolic rate [O(2) consumption (Vo(2)) and CO(2) production (Vco(2))]. The present study aimed at testing our hypothesis that daily metabolic rates changed in parallel with ventilation during development and that a weak HVR at P13 was attributable mainly to an inadequate metabolic rate in hypoxia. Ventilation and metabolic rates were monitored daily in P0-P21 rats. We found that 1) ventilation and metabolic rates were not always correlated, and Ve/Vo(2) and Ve/Vco(2) ratios were not constant during development; 2) metabolic rate and Ve/Vo(2) and Ve/Vco(2) ratios at P0-P1 were significantly different from the remaining first postnatal week in normoxia and hypoxia; 3) at P13, metabolic rates and Ve/Vo(2) and Ve/Vco(2) ratios abruptly increased in normoxia and were compromised in acute hypoxia, unlike more stable trends during the remaining second and third postnatal weeks; and 4) the respiratory quotient (Vco(2)/Vo(2)) was quite stable in normoxia and fluctuated slightly in hypoxia from P0 to P21. Thus our data revealed heretofore unsuspected metabolic adjustments at P0-P1 and P13. At P0-P1, ventilation and metabolic rates were uncorrelated, whereas at P13, they were closely correlated under normoxia and hypoxia. The findings further strengthened the existence of a critical period of respiratory development around P13, when multiple physiological and neurochemical adjustments occur simultaneously.

Recent studies indicate that the infant rat has high affinity for ethanol ingestion and marked sensitivity to the drug's reinforcing effects [Spear, N.E., Molina, J.C. Fetal or infantile exposure to ethanol promotes ethanol ingestion in adolescence and adulthood: a theoretical review. Alcohol Clin Exp Res 2005; 29: 909-29.]. A novel operant technique was developed to analyze reinforcing effects of ethanol delivery during the third postnatal week. The impact of this ethanol-reinforcement experience upon subsequent ethanol consumption during adolescence (postnatal weeks 5-6) was also examined. In Experiment 1, pups (postnatal days 14-17) were given an explicit contingency between nose-poking behavior and intraoral delivery of either water or 3.75% v/v ethanol (paired groups). Yoked controls (pups receiving either reinforcer independently of their behavior) were also included. Paired subjects reinforced with ethanol exhibited rapid and robust operant conditioning leading to blood ethanol concentrations in the 25-48 mg% range. In Experiment 2, a higher ethanol concentration (7.5% v/v) provided significant reinforcement. During adolescence, animals originally reinforced with 3.75% v/v ethanol exhibited greater ingestion of ethanol than control animals without prior ethanol reinforcement. These results indicate that, without extensive initiation to ethanol, infant rats rapidly learn to gain access to ethanol and that this experience has a significant impact upon later ethanol intake patterns.

Rationale: The endocannabinoid system plays a crucial role in the control of emotionality and recent clinical findings have shown that heavy prenatal exposure to cannabis is significantly associated with self-reported anxiety symptoms in exposed children. However, the long-term neurobehavioral consequences of in utero exposure to low-moderate doses of cannabinoid compounds have never been investigated., Objective: The objective of this study was to investigate whether perinatal exposure to moderate doses of the active constituent of cannabis, the CB(1) cannabinoid receptor agonist delta-9-tetrahydrocannabinol (THC), influences the emotional reactivity of rat offspring., Methods: Primiparous Wistar rats were treated during pregnancy and lactation with doses of THC equivalent to the current estimates of moderate cannabis consumption in humans (2.5-5 mg kg(-1), per os, from gestational day 15 to postnatal day 9). The emotional reactivity of infant, adolescent, and adult offspring was investigated using the isolation-induced ultrasonic vocalization, social interaction, and elevated plus-maze tests, respectively., Results: Perinatal THC treatment did not affect parameters of reproduction; however, at the dose of 5 mg kg(-1), it increased the number of ultrasounds emitted by rat pups removed from the nest, inhibited social interaction and play behavior in the adolescent offspring, and induced an anxiogenic-like profile in the adult offspring tested in the elevated plus-maze test., Conclusion: These results suggest that the endocannabinoid system is involved in the control of emotionality since early developmental stages. Thus, even moderate doses of cannabinoid compounds, when administered during the perinatal period, can have profound consequences for brain maturation, leading to long-lasting neurodevelopmental alterations.

Exposure to ethanol during development induces severe brain damage resulting in a number of CNS dysfunctions including microencephaly and mental retardation in humans and in laboratory animals. The most vulnerable period to ethanol neurotoxicity coincides with the peak of brain growth spurt. Recently, neurotrophic factors and/or their signal transduction pathways have been reported as a potential relevant target for the developmental neurotoxicity of ethanol. The present studies were designed to investigate the effects of ethanol given in various developmental phases during the brain growth spurt in rats. Rat pups were assigned to the three treatment groups and treated with 5 g/kg of ethanol for three days, on postnatal days (PND) 2-4, 6-8 or 13-15. Whole brain weights were reduced only in the PND 6-8 group concurrently with the reduction of GDNF mRNA in cortex in this group. BDNF mRNA expression was reduced in both the PND 6-8 and 13-15 groups, while mRNA expressions of NT-3 and NGF were unchanged in all three groups. Phospho-Akt level was mostly reduced in the PND 6-8 group. Both phospho-MAPK and p-70S6 kinase levels were decreased in all groups whereas no changes were observed in either phospho-PKCzeta or CREB level. The phosphorylation of Akt was immediately inhibited after single administration of ethanol, and its inhibition was correlated with variations in blood ethanol concentration. These findings suggest that GDNF and the phosphorylation of Akt play a possible key role in the ethanol-induced developmental neurotoxicity.

Study Objectives: Previous investigators have suggested that quiet sleep (QS) in rats develops rapidly upon the emergence of cortical delta activity around postnatal day (P)11 and that the presence of "half-activated" active sleep (AS) suggests that infant sleep is initially disorganized. To address these issues, we examined the temporal organization of sleep states during the second postnatal week in rats as delta activity emerges., Design: Subjects were P9, P11, and P13 Sprague-Dawley rats. Electroencephalogram and nuchal electromyogram electrodes were implanted, and data were recorded at thermoneutrality for 2 hours., Results: At all ages, using electromyogram and behavioral criteria, QS (defined as nuchal atonia and behavioral quiescence) dominated the first third of each sleep period, whereas AS (defined as nuchal atonia accompanied by myoclonic twitching) dominated the last third. When delta activity, which was first detected at P11, could be added to the definition of QS, gross assessments of sleep-state organization were not altered, although it was now possible to identify brief periods of QS interposed between periods of AS. No evidence of "half-activated" AS was found. Finally, "slow activity transients" were detected and were primarily associated with QS; their rate of occurrence declined as delta activity emerged., Conclusions: When delta activity emerges at P11, it integrates smoothly with periods of QS, as defined using electromyogram and behavioral criteria alone. Delta activity helps to refine estimates of QS duration but does not reflect a significant alteration of sleep-state organization. Rather, this organization is expressed much earlier in ontogeny as fluctuations in muscle tone and associated phasic motor activity.

To assess how early can estrogens induce female mating behaviors, rat pups 8-29 days old (D8-D29, respectively) were injected twice daily with estradiol benzoate (E) or oil (O) followed by progesterone (P) or oil, and then observed for the estrogen-dependent ear wiggling (EW) and lordosis in response to natural stimulation from male rats. In female pups treated with E + E + P, the incidence of EW appeared as early as D13 and increased gradually to reach maximum at D18, when all pups tested showed EW. EW also occurred in E + E + O females, but never in O + O + P females or in any E + E + P male. Lordosis in E + E + P, as well as E + E + O, female pups occurred later, starting at D15. O + O + P females or E + E + P males never display lordosis. To explore the possibilities that the age and gender differences are due to distribution and/or function of estrogen receptor-alpha (ERalpha) or progesterone receptor (PR), separate pups were used for immunocytochemical (ICC) staining of these receptors in the hypothalamic ventromedial nucleus (VMN). There was no age difference in female pups in the density of ERalpha or the induction of PR between D11/D12, when no sexual behavior was observed, and D19/D20, when almost all pups tested performed the behaviors. There were gender differences: male pups had less ERalpha than females at D19/D20, though not at D11/D12, and did not respond to E in the induction of PR in the VMN. These results show that ERs and their signaling systems in the VMN of rat pups are functional at least after D11 but only in females, and that the gender differences appeared to be due to differences in the molecular biology of ERalpha.

Organotypic cultures of rat cortex were used to test the hypotheses that nerve growth factor (NGF) is neuroprotective for immature cortical neurons and that ethanol abolishes this neuroprotection in a developmental stage-dependent manner. Samples were obtained on gestational day (G) 16 or postnatal day (P) 3 and cultured with ethanol (0 or 400 mg/dl) and NGF (0 or 30 ng/ml) for 72 h. Dying neurons were identified as exhibiting terminal nick-end labeling, immunoreactivity for activated caspase 3, or condensed nuclear chromatin. Two cortical compartments were examined in fetal tissue: a superficial, cell-sparse marginal zone (MZ) and a cell-dense cortical plate (CP). At P3, the CP was subdivided into a cell-dense upper cortical plate (UCP) and a less densely packed lower cortical plate (LCP). Neuronal death in the MZ was affected by neither NGF nor ethanol at both ages. In the fetal CP, NGF did not affect the incidence of cell death, but ethanol increased it. Treatment with NGF caused an upregulation of the expression of Neg, a gene known to be affected by NGF and ethanol. NGF did not ameliorate the ethanol-induced death. In pups, ethanol increased the amount of death in the LCP. NGF did protect against this death. Neither ethanol nor NGF altered the incidence of cell death in the UCP. The laminar-dependent neuroprotection did not correlate with expression of NGF receptors or Neg. Thus, NGF can be protective against the neurotoxic effect of ethanol in the neonatal brain. This effect is site selective and time dependent and it targets postmigratory, differentiating neurons.

The effects of chronic administration of pentylenetetrazole (PTZ) during early ontogenesis (from postnatal day 14) on the dynamics of age-related changes in electrophysiological characteristics of rat hippocampal slices were studied. Unlike the situation in adult animals, convulsive activity did not develop in rat pups in response to repeated injections. Comparison of the amplitude characteristics of total monosynaptic responses of neurons in hippocampal field CA1 to application of single and paired (separated by 70 msec) stimulation of Schäffer collaterals during the period of maximally intense hippocampal synaptogenesis (at weeks 2-3 of postnatal development) revealed no significant differences between the control group (administration of isotonic saline) and the group given PTZ. The level of suppression of facilitation in paired-pulse stimulation with a short interstimulus interval (15 msec) was significantly less in hippocampal slices from rat pups from the PTZ group. However, as compared with the passive control, the direction of rearrangements in the two experimental group was essentially the same. Nonetheless, regular administration of PTZ during the period of maximally intense hippocampal maturation affected the development of its characteristics. This was not only apparent as a deficiency of inhibitory processes. Increases in the intensity of test stimuli applied to hippocampal slices from PTZ-treated rat pups at 27-48 days of age led to relatively lower response amplitudes as compared with those seen in hippocampal slices from control (given isotonic saline) rats of the same age. The level of facilitation in paired-pulse stimulation with an interstimulus interval of 70 msec showed no difference, decreasing to similar extents in both groups as compared with the passive control group. In addition, hippocampal slices from the PTZ group showed significant decreases in the magnitude of long-term potentiation. Changes occurring in the hippocampus after regular administration of PTZ did not correlate with the development of convulsive activity. The only significant relationship involving the intensity of convulsions was with the increase (compared with the normal for age) in the amplitudes of responses to minimal-intensity test stimuli.

Reasons for Performing Study: Conformational traits are important in breeding, since they may be indicative for performance ability and susceptibility to injuries., Objectives: To study whether certain desired conformational traits of foals are related to lateralised behaviour while foraging and to the development of uneven feet., Methods: Twenty-four Warmblood foals, born and raised at the same location, were studied for a year. Foraging behaviour was observed by means of weekly 10 min scan-sampling for 8 h. A preference test (PT) was developed to serve as a standardised tool to determine laterality. The foals were evaluated at age 3, 15, 27 and 55 weeks. The PT and distal limb conformation were used to study the relation between overall body conformation, laterality and the development of uneven feet. Pressure measurements were used to determine the loading patterns under the feet., Results: About 50% of the foals developed a significant preference to protract the same limb systematically while grazing, which resulted in uneven feet and subsequently uneven loading patterns. Foals with relatively long limbs and small heads were predisposed to develop laterality and, consequently unevenness., Conclusions: Conformational traits may stimulate the development of laterality and therefore indirectly cause uneven feet.

Hypoxia-ischemia (HI) is associated with premature birth, and injury during term birth. Many infants experiencing HI later show disruptions of language, with research suggesting that rapid auditory processing (RAP) deficits (i.e., impairment in the ability to discriminate rapidly changing acoustic signals), play a causal role in language problems. We recently bridged these lines of research by showing RAP deficits in rats with unilateral-HI injury induced on postnatal days 1, 7, or 10 (P1, P7, or P10. While robust RAP deficits were found in HI animals, it was suggested that our within-age sample size did not provide sufficient power to detect age-at-injury differences within the pooled HI group. The current study sought to examine differences in neuropathology and behavior following unilateral-HI injury on P1 versus P7 in rats. Ages chosen for HI induction reflect differential stages of neurodevelopmental maturity, and subsequent regional differences in vulnerability to reduced blood flow/oxygen (modeling age-related differences in premature/term HI injury). Results showed that during the juvenile period, both P1 and P7 HI groups exhibited significant RAP deficits, but deficits in the P1 HI group resolved with repeated testing (compared to shams), while P7 HI animals showed lasting deficits in RAP and spatial learning/memory through adulthood. The current findings are in accord with evidence that HI injury during different stages of developmental maturity (age-at-injury) leads to differential neuropathologies, and provide the novel observation that in rats, P1 versus P7 induced pathologies are associated with different patterns of auditory processing and learning/memory deficits across the lifespan.

Pregnancy rate, calving interval, birth weight, weaning weight, and quarterly BCS were collected for 5 consecutive years on 454 fall-calving multiparous British crossbred cattle (3 to 10 yr of age) to evaluate associations of age with BCS and production parameters. Body weight and BCS were collected pre-calving, prebreeding, at weaning, and midway through the second trimester of pregnancy (August). Body condition score was correlated with age during all seasons (P < 0.01). At calving, breeding, and in August, 3-yr-old cows had the lowest BW and BCS, whereas 8-yr-old cows had the greatest. At weaning, these values were maximal in 10-yr-old cows. Pregnancy rate was near 80% up to 9 yr of age but decreased to 57% in 10-yr-old cows. The relationship of pregnancy rate with age appears to be correlated with the BCS decrease at breeding in the older cows, supported by the fact that inclusion of BCS at breeding in the statistical model eliminated the effect of age on pregnancy rate (P = 0.42). Calving interval was longer in 3-yr-old cows compared with 4- to 9-yr-old cows (P = 0.02); however, among older cows, there was little change in the calving interval. Birth weight reached a maximum at 8 yr of age (35 +/- 0.9 kg) and a minimum in 3-yr-old cows (32 +/- 0.7 kg). Birth weights of calves born to both 3- and 4-yr-old cows were lower than for those born to 5-, 6-, 7-, or 8-yr-old cows (P < 0.05). Ten-year-old cows weaned lighter calves (205-d adjusted weaning weight) than younger dams. Furthermore, 3-yr-old cows weaned calves 9 +/- 2.1 and 14 +/- 2.4 kg lighter than 4- and 5-yr-old cows, respectively (P < 0.001). Interpretation of the age analyses of calving interval, birth weight, and weaning weight was independent of the inclusion of BCS in the model. This study documents the effects of age on calving interval, birth weight, and weaning weight that are independent of BCS.

Hypoxia-ischemia (HI) injury in neonatal animals leads to selective regional loss of neurons including CA1 and CA3 pyramidal neurons of the hippocampus as well as nonlethal pathologies. Glutamate-receptor over-activation and Ca2+ influx are involved in these neonatal changes. We examined glutamate-evoked Ca2+ responses in neonatal (PN 7-13) and young adult (PN 21-27) CA1 pyramidal neurons in acute slices from rats. In neonates, transient exposure to glutamate produced large Ca2+ increases throughout neurons, including distal dendrites (primary Ca2+ responses). Repeated exposures resulted in sustained Ca2+ increases in apical dendrites (secondary Ca2+ responses) that were independent of continued glutamate exposure. These responses propagated and invaded the soma, resulting in irrecoverably high Ca2+ elevations. In neurons from adults, identical glutamate exposure evoked primary Ca2+ responses only in somata and proximal apical dendrites. Repeated glutamate exposures in the adult neurons also led to secondary Ca2+ responses, but they arose in the peri-somatic region and then spread outward to distal apical dendrites, again without recovery. More stimuli were required to initiate secondary responses in neurons from adult versus neonates. Block of GABAA receptors in adults caused the primary and secondary responses to revert to the spatial pattern seen in the neonates and greatly increased their vulnerability to glutamate. These findings suggest that neurodegenerative secondary Ca2+ events may be important determinants of susceptibility to HI injury in the developing CNS and that immature CA1 neurons may be more susceptible to excitotoxic injury due at least in part to insufficient development of GABAergic inputs to their dendrites.

1. Foraging behaviours of the Australian sea lion (Neophoca cinerea) reflect an animal working hard to exploit benthic habitats. Lactating females demonstrate almost continuous diving, maximize bottom time, exhibit elevated field metabolism and frequently exceed their calculated aerobic dive limit. Given that larger animals have disproportionately greater diving capabilities, we wanted to examine how pups and juveniles forage successfully. 2. Time/depth recorders were deployed on pups, juveniles and adult females at Seal Bay Conservation Park, Kangaroo Island, South Australia. Ten different mother/pup pairs were equipped at three stages of development (6, 15 and 23 months) to record the diving behaviours of 51 (nine instruments failed) animals. 3. Dive depth and duration increased with age. However, development was slow. At 6 months, pups demonstrated minimal diving activity and the mean depth for 23-month-old juveniles was only 44 +/- 4 m, or 62% of adult mean depth. 4. Although pups and juveniles did not reach adult depths or durations, dive records for young sea lions indicate benthic diving with mean bottom times (2.0 +/- 0.2 min) similar to those of females (2.1 +/- 0.2 min). This was accomplished by spending higher proportions of each dive and total time at sea on or near the bottom than adults. Immature sea lions also spent a higher percentage of time at sea diving. 5. Juveniles may have to work harder because they are weaned before reaching full diving capability. For benthic foragers, reduced diving ability limits available foraging habitat. Furthermore, as juveniles appear to operate close to their physiological maximum, they would have a difficult time increasing foraging effort in response to reductions in prey. Although benthic prey are less influenced by seasonal fluctuations and oceanographic perturbations than epipelagic prey, demersal fishery trawls may impact juvenile survival by disrupting habitat and removing larger size classes of prey. These issues may be an important factor as to why the Australian sea lion population is currently at risk.

The objective of this study was to establish the age at which mink kits develop functional homoeothermy. The investigation was based on the hypothesis that in this species with very immature neonates, late development of homoeothermy may be an adaptation to economize with energy. Measurements of heat production (HE) by means of indirect calorimetry lasting 3 h were performed on neonatal kits and kits from 1 to 54 days of age. Both single kits and groups of 4-5 huddling kits were kept at 15 degrees C (L) or 30 degrees C (H) [from 35 days onwards at 25 degrees C (H)]. Animals were weighed before and after the experiments and evaporative water losses (EWL) were calculated. When exposed to L temperature, single kits responded with a very low HE until 29 days of age, and groups of kits until 14 days of age. It was not until they reached an age of approximately 6 weeks that single kits showed a clear thermoregulatory response to the L temperature by increased HE, whereas groups of kits showed increased HE from 29th day onwards. When kept at H temperature, HE was low initially, but all kits showed elevated HE at 8 days of age, and the metabolic rate was similar for single kits and kits huddling in groups. Evaporative water losses was higher among single than among groups of kits and slightly lower but more variable for animals at L than at H temperature. It was concluded that mink kits develop functional homoeothermy at an age of close to 6 weeks and that the failure of very young kits to thermoregulate is an adaptation mechanism in order to economise with their very limited body energy reserves.

The hemodynamic conditions of aorta are relatively uniform prenatally and become more heterogeneous postnatally. Our objective was to quantify the heterogeneity of geometry and mechanical properties during growth and development. To accomplish this objective, we obtained a systematic set of data on the geometry and mechanical properties along the length of mouse aorta during postnatal development. C57BL/6 mice of ages 1-33 days were studied. The ascending aorta was cannulated in situ and preconditioned with several cyclic changes in pressure. We investigated the axial variations of geometry (diameter and length) and mechanical properties (stress-stain relation, elastic modulus and compliance) of the mouse aorta from the aortic valve to the common iliac. Our results show that the arterial blood pressure of mice increased from approximately 30 to 80 mmHg during the first 2 wk of life. The stretch ratio, diameter, wall (intima-media) thickness, and total lumen volume of mouse aorta increased with age. The aorta was transformed from a cylindrical tube at birth to a tapered structure during growth. Furthermore, we found the mechanical properties were fairly uniform along the length of the aorta at birth and become more nonuniform with age. We conclude that the rapid change of blood pressure and blood flow after birth alter the geometric and mechanical properties differentially along the length of the aorta. Hence, the axial nonuniformity of the aorta increases as the organ becomes more specialized during growth and development.

The inhibitory transmitters glycine and GABA undergo a developmental shift from depolarizing to hyperpolarizing action (D/H-shift). To analyse this shift in functionally related nuclei of the rat superior olivary complex (SOC), we employed voltage-sensitive dye recordings in auditory brainstem slices. Complementarily, we analysed single neurons in gramicidin perforated-patch recordings. Our results show a differential timing of the D/H-shift in the four SOC nuclei analysed. In the medial superior olive (MSO), the shift occurred at postnatal day (P) 5-9. In the superior paraolivary nucleus (SPN), it occurred between embryonic day (E) 18 and P1. No D/H-shift was observed in the medial nucleus of the trapezoid body (MNTB) until P10. This is in line with the finding that most of the patched MNTB neurons displayed glycine-induced depolarizations between P0-9. While no regional differences regarding the D/H-shift were found within the MSO, SPN, and MNTB, we observed such differences in the lateral superior olive (LSO). All LSO regions showed a D/H-shift at P4-5. However, in the high-frequency regions, hyperpolarizations were large already at P6, yet amplitudes of this size were not present until P8 in the low-frequency regions, suggesting a delayed development in the latter regions. Our physiological results demonstrate that D/H-shifts in SOC nuclei are staggered in time and occur over a period of almost two weeks. Membrane-associated immunoreactivity of the Cl- outward transporter KCC2 was found in every SOC nucleus already at times when glycine was still depolarizing. This implies that the mere presence of KCC2 does not correlate with functional Cl- outward transport.

Glutamate is a classical excitotoxin of the central nervous system (CNS), but extensive work demonstrates neuroprotective roles of this neurotransmitter in developing CNS. Mechanisms of glutamate-mediated neuroprotection are still under scrutiny. In this study, we investigated mediators of glutamate-induced neuroprotection, and tested whether this neurotransmitter controls programmed cell death in the developing retina. The protective effect of N-methyl-d-aspartate (NMDA) upon differentiating cells of retinal explants was completely blocked by a neutralizing antibody to brain-derived neurotrophic factor (BDNF), but not by an antibody to neurotrophin-4 (NT-4). Consistently, chronic activation of NMDA receptor increased the expression of BDNF and trkB mRNA, as well as BDNF protein content, but did not change the content of NT-4 mRNA in retinal tissue. Furthermore, we showed that in vivo inactivation of NMDA receptor by intraperitoneal injections of MK-801 increased natural cell death of specific cell populations of the post-natal retina. Our results show that chronic activation of NMDA receptors in vitro induces a BDNF-dependent neuroprotective state in differentiating retinal cells, and that NMDA receptor activation controls programmed cell death of developing retinal neurons in vivo.

Effects of maternal deprivation (MD) with different conditions were examined on the circadian rhythms in plasma corticosterone and locomotor activity in adult rats under ad libitum and restricted daily feeding (RF), in which rats had free access to food for 2 h for 3 weeks. Three different types of MD were performed from postnatal day 1 (P1) to day 6 (P6); MD for 12 h/day (MD12), for 3 h/day in the morning (MD3am) and in the afternoon (MD3pm). Under ad libitum feeding, corticosterone levels at 08:00 h and 24:00 h were significantly increased in MD12 rats. A similar increase was detected in MD3am rats, but not in MD3pm rats. Under the RF, corticosterone levels at 08:00 h, 24:00 h, and 04:00 h were significantly increased in MD12 rats. Similar elevations were detected in MD3am rats, but not in MD3pm rats. Furthermore, prefeeding locomotor activities under the RF increased significantly in MD12 rats. A similar increase was observed in MD3am rats, but not in MD3pm rats. Keeping ambient temperature and humidity at 37 degrees C and 70-80% during MD attenuated the effects of MD on the corticosterone rhythmicities under RF as well as ad lib feeding. It is concluded that MD in the early postnatal period influences the expressions of circadian rhythms in plasma corticosterone and locomotor activity in adult rats. Not only the length but also the time of day of MD seems to be critical for these effects. Ambient temperature and/or humidity are suggested to be one of the factors by which MD exerts its effect.

Data were collected prospectively on parameters related to first calving on 18 farms located in Northeastern Pennsylvania. This project was designed to study possible residual effects of calf management practices and events occurring during the first 16 wk of life on age, BW, skeletal growth, and body condition score at first calving. Multiple imputation method for handling missing data was incorporated in these analyses. This method has the advantage over ad hoc single imputations because the appropriate error structure is maintained. Much similarity was found between the multiple imputation method and a traditional mixed model analysis, except that some estimates from the multiple imputation method seemed more logical in their effects on the parameter measured. Factors related to increased age at first calving were increased difficulty of delivery, antibiotic treatment of sick calves, increased amount of milk or milk replacer fed before weaning, reduced quality of forage fed to weaned calves, maximum humidity, mean daily temperature, and maximum ammonia levels in calf housing areas. Body weight at calving tended to increase with parity of the dam, increased amount of grain fed to calves, increased ammonia levels, and increased mean temperature of the calf housing area. Body condition score at calving tended to be positively influenced by delivery score at first calving, dam parity, and milk or milk replacer dry matter intake. Withers height at calving was positively affected by treatment of animals with antibiotics and increased mean temperature in the calf area. This study demonstrated that nutrition, housing, and management factors that affect health and growth of calves have long-term effects on the animal at least through first calving.

The aim of the present study was to investigate the effects of neonatal excitotoxic lesions of the medial prefrontal cortex (mPFC) on social play, social behavior unrelated to play, and self-grooming in juvenile and adult rats. We additionally examined the behavioral effects of chronic pubertal treatment with the cannabinoid agonist WIN 55,212-2 (WIN) in order to test the hypothesis that early lesions render the brain vulnerable to cannabinoid intake in later life. Neonatal mPFC lesions and pubertal WIN treatment disrupted social play, social behavior, and self-grooming in juvenile and adult rats. Additionally, we observed more social play behaviors during light cycle in WIN-treated than in vehicle-treated rats. Notably, the combination of surgery and WIN treatment disrupted social behavior in lesioned and sham-lesioned rats. The present data indicate that the mPFC is important for adequate juvenile response selection in the context of social play and might be involved in the development of adult social and nonsocial behavior. Moreover, our data add further evidence for an involvement of the cannabinoid system in anxiety and social behavior. Additive effects of neonatal surgery-induced stress or cortical lesions in combination with pubertal cannabinoid administration are also shown. The disturbances of social and nonsocial behavior in rats are comparable to symptoms of early frontal cortex damage, as well as neurodevelopmental disorders in humans, such as schizophrenia and autism. Therefore, we propose the combination of neonatal cortical lesions with chronic cannabinoid administration during puberty as an animal model for studying neuronal mechanisms of impaired social functioning in neuropsychiatric disorders.

Ectopic testicular xenografting can be used to investigate spermatogenesis and as an alternative means for generating transgenic spermatozoa in many species. Improving the efficiency of spermatogenesis in xenografted testicular tissue will aid in the application of using this approach. The present study was conducted to evaluate age-related differences in the establishment of spermatogenesis in grafted testicular tissue from bulls between 2 and 16 wk of life. Testicular tissue was ectopically xenografted under the skin on the backs of castrated nude mice and subsequently evaluated for growth, testosterone production, and establishment of spermatogenesis 24 wk after grafting. The greatest weight increases occurred in donor tissue from calves of the ages 2, 4, and 8 wk compared with the ages of 12 and 16 wk. Recipient mouse serum testosterone concentration was at normal physiological levels 24 wk after grafting and no significant differences were detected between recipients grafted with testicular tissue from bull calves of different ages. The development of germ cells to elongated spermatids were observed in seminiferous tubules of grafts from donor calves of the ages 4, 8, 12, and 16 wk but not observed in grafts from 2-wk donors, which contained round spermatids as the most advanced germ cell stage. Grafts from 8-wk donors contained a significantly higher (10-fold) average percentage of seminiferous tubules with elongated spermatids than all other donor ages. These data demonstrate differences in the ability of testicular tissue from donor animals of different ages to establish spermatogenesis following ectopic testicular xenografting.

Individual olfactory bulb mitral/tufted cells respond preferentially to groups of molecularly similar odorants. Bulbar interneurons such as periglomerular and granule cells are thought to influence mitral/tufted odorant receptive fields through mechanisms such as lateral inhibition. The mitralgranule cell circuit is also important in the generation of the odor-evoked fast oscillations seen in the olfactory bulb local field potentials and hypothesized to be an important indicator of odor quality coding. Infant rats, however, lack a majority of these inhibitory interneurons until the second week of life. It is unclear if these developmental differences affect olfactory bulb odor coding or behavioral odor discrimination. The following experiments are aimed at better understanding odor coding and behavioral odor discrimination in the developing olfactory system. Single-unit recordings from mitral/tufted cells and local field-potential recordings from both the olfactory bulb and anterior piriform cortex were performed in freely breathing urethane-anesthetized rats (postnatal day 7 to adult). Age-dependent behavioral odor discrimination to a homologous series of ethyl esters was also examined using a cross-habituation paradigm. Odorants were equated in all experiments for concentration (150 ppm) using a flow dilution olfactometer. In concordance with the reduced interneuron population, local field potentials in neonates lacked detectable odor-evoked gamma-frequency oscillations that were observed in mature animals. However, mitral/tufted cell odorant receptive fields and behavioral odor discrimination did not significantly change, despite known substantial changes in local circuitry and neuronal populations, over the age range examined. The results suggest that high-frequency local field-potential oscillations do not reflect processes critical for simple odor discrimination.

To address the hypothesis that maturation enhances endothelial vasodilator function in cerebral arteries, relaxant responses to ADP and A-23187 were determined in ovine carotid and cerebral arteries harvested from 25 newborn lambs (3-7 days) and 23 adult sheep. Maturation significantly increased pD(2) values for A-23187 (newborn range: 4.9 +/- 0.3 to 5.4 +/- 0.3; adult range: 6.0 +/- 0.2 to 7.1 +/- 0.2) and the maximal vasodilator response to A-23187 by 10-18%. In contrast, maturation decreased maximum responses to ADP by 5-25% with no change in pD(2). The magnitudes of endothelium-dependent relaxation were not affected by 10 microM indomethacin but were virtually abolished by 100 microM N(G)-nitro-L-arginine methyl ester/L-nitro arginine, indicating that nitric oxide (NO) is the primary endothelium-dependent vasodilator in these arteries. Maturation also modestly decreased endothelial NO synthase (eNOS) abundance in both carotid (32%) and cerebral (26%) arteries. Together, these findings reinforce the view that receptor coupling to endothelial activation is tightly regulated and may offset underlying changes in maximal endothelial vasodilator capacity. This capacity, in turn, appears to increase with postnatal age despite major growth and expansion of endothelial cell size and vascular wall volume. In ovine cerebral arteries, endothelial vasodilator capacity appears completely dependent on eNOS activity but not on cyclooxygenase activity. In turn, eNOS activity appears to be postnatally regulated by mechanisms independent of changes in eNOS abundance alone.

The nitric oxide (NO)/cGMP pathway plays a key role in the regulation of pulmonary vascular tone during the transition from the fetal to the neonatal circulation, and it is impaired in pathophysiological conditions such as pulmonary hypertension. In the present study, we have analyzed the changes in the function and expression of soluble guanylyl cyclase (sGC) in pulmonary arteries during early postnatal maturation in isolated third-branch pulmonary arteries from newborn (3-18 h of age) and 2-wk-old piglets. The expression of sGC beta(1)-subunit in pulmonary arteries increased with postnatal age both at the level of mRNA and protein. The catalytic region of porcine sGC beta(1) was sequenced, showing a 92% homology with the human sequence. This age-dependent increase in sGC expression correlated with increased vasorelaxant responses to the physiological sGC activator NO and to the exogenous sGC activator YC-1, but not to the membrane-permeable cGMP analog 8-bromoguanosine 3',5'-cyclic monophosphate. In conclusion, an increased expression of sGC in pulmonary conduit arteries from 2-wk-old compared with newborn piglets explains, at least partly, the age-dependent increase in the vasorelaxant response of NO and other activators of sGC.

We report here a systematic investigation of the dynamics, regulation and distribution of spontaneous waves in the rabbit retina during the course of wave development prior to eye opening. Three major findings were obtained in this longitudinal study. (1) Spontaneous retinal waves underwent three developmental stages, each of which displayed distinct wave dynamics, pharmacology and mechanism of generation and regulation. Stage I waves emerged prior to synaptogenesis and appeared as frequent, fast propagating waves that did not form spatial boundaries between waves. These waves could be inhibited by blockers of gap junctions and adenosine receptors, but not by nicotinic antagonists. Stage I waves lasted about one day (around embryonic day 22) and then switched rapidly to stage II, resulting in slower and less frequent waves that could be blocked by nicotinic antagonists and had a characteristic postwave refractory period and spatial boundaries between adjacent waves. Immediately after the transition from stage I to stage II, the waves could be reverted back to stage I by blocking nicotinic receptors, indicating the presence of mutually compensatory mechanisms for wave generation. Stage III waves emerged around postnatal day 3-4 (P3-4), and they were mediated by glutamtergic and muscarinic interactions. With age, these waves became weaker, more localized and less frequent. Spontaneous waves were rarely detected after P7. (2) GABA strongly modulated the wave dynamics in a stage- and receptor type-dependent manner. At stage I, endogenous GABAB activation downregulated the waves. The GABAB modulation disappeared during stage II and was replaced by a strong GABA(A/C)-mediated inhibition at stage III. Blocking GABA(A/C) receptors not only dramatically enhanced spontaneous stage III waves, but also induced propagating waves in >P7 retinas that did not show spontaneous waves, indicating a role of GABA inhibition in the disappearance of spontaneous waves. (3) Spontaneous retinal waves were found in both the inner and outer retina at all three stages. The waves in the outer retina (ventricular zone) also showed stage-dependent pharmacology and dynamics. Together, the results revealed a multistaged developmental sequence and stage-dependent dynamics, pharmacology and regulation of spontaneous retinal waves in the mammalian retina. The presence of retinal waves during multiple developmental stages and in multiple retinal layers suggests that the waves are a general developmental phenomenon with diverse functions.

The incidence of childhood cancer is increasing. One of the most common cancers for children under 15 years of age, gliomas for example, has been reported to have increased in incidence over the last 20 years by approximately 40%. The rising trend of childhood cancer in brain may be associated with environmental exposure to genotoxins and susceptibility to mutation in early development. To investigate age-dependent mutagenic sensitivity of brain tissue to genotoxins, the Big Blue mouse model was utilized in this study. Groups of five male mice were treated with a single dose of 120 mg/kg ENU transplacentally at three days before birth (prenatal), eight days (neonate) or eighteen weeks (adult) after birth. The animals were sacrificed six weeks after the treatment. The mutant frequencies and types of mutations in the brain cII gene from ENU-treated and concurrent control mice were determined. A significant increase in mutant frequencies over control was found in the prenatal and neonatal groups whereas there was no significant difference between the adult group and its control. Molecular analysis of the mutants also indicated that the mutational spectra from the ENU-treated mice were age-dependent. The percentage of A:T --> T:A transversion, the typical type of mutation induced by ENU, was inversely related to the treatment age, whereas G:C --> A:T transition was the main type of mutation in the adult group, the same as the control. These results demonstrate a differential mutagenic effect of ENU on the mouse brain depending on the stages of development and suggest an enhanced susceptibility of brain cancer hazard for perinatal exposure to genotoxicants.

To understand normal cloacal developmental processes, serial sagittal sections of mouse embryos were made every 6 hrs from embryonic day 11.5 (E11.5) to E13.5. During cloacal development to form the urogenital sinus and anorectal canal, fusion of the urorectal septum with the cloacal membrane was not observed, and the ventral and dorsal parts of the cloaca were continuously connected by the canal until disappearance of the cloacal membrane to open the vestibule formed by the urogenital sinus and anorectal canal to the outside at E13.5. Ventral shifting of the dorsal part of the cloaca was observed until E12.5. The dorsal part was transformed in accordance with ventral shifting. In addition, apoptosis was seen to occur around the dorsal part. However, from E12.25, apoptotic cells are observed in a linear arrangement in the urorectal septum just ventral to the peritoneal cavity. Interestingly, extension of this line reaches the area of the cloacal membrane disintegrated by apoptosis. The present findings suggest that in the early stages (until E12.0), distribution of apoptosis in mesenchyme around the dorsal part of the cloaca might be strongly related to the transformation and ventral shifting of this part. Conversely, the apoptosis pattern in urorectal septum mesenchyme in later stages (from E12.0) might be involved in transformation of the urorectal septum and disintegration of the cloacal membrane.

Background: Sensitivity to several ethanol effects increases during ontogeny, perhaps in part because of a notable decline in acute tolerance. In contrast, rapid tolerance to ethanol-induced sedation emerges slowly during ontogeny. This study tested the hypothesis that ontogenetic differences in glutamate and/or gamma-aminobutyric acid systems influence tolerance expression., Methods: Sprague-Dawley rats at postnatal day (P)26 or P70 received (+)MK-801, muscimol, or saline before ethanol (3.5 or 4.5 g/kg) or saline on day 1 and ethanol only on day 2. Loss of and time to regain the righting reflex and blood alcohol levels at recovery were recorded. The presence of acute tolerance was indicated as a positive slope of the linear regression of blood alcohol levels at recovery versus ethanol dose. Rapid tolerance was estimated on day 2 by comparing animals given ethanol only on day 2 with those given ethanol on both days., Results: Acute tolerance on day 1 only was observed at P26; this was disrupted by (+)MK-801 but not muscimol. Evidence for acute tolerance also emerged in adults on day 2. Whereas both drugs increased ethanol sedation at both ages, they did not facilitate ontogenetic expression of rapid tolerance: rapid tolerance was not evident at P26 regardless of pretreatment when indexed in terms of recovery time., Conclusions: These data provide further evidence for an ontogenetic dissociation in the expression of acute and rapid tolerance to ethanol-induced sedation. Pharmacological attenuation of the expression of acute tolerance was sufficient but not necessary to delay recovery of righting after ethanol. The greater propensity of young animals to develop acute tolerance, seemingly modulated in part by NMDA receptors, may contribute to their relative resistance to ethanol, although other factors, including pharmacokinetic factors, also contribute to their more rapid recovery from ethanol sedation., (Copyright 2004 Research Society on Alcoholism)

A study was undertaken to investigate the changes of plasma non-esterified fatty acids (NEFA), glucose and alpha-amino nitrogen and their relationship with age, body weight (BW) and plasma growth hormone (GH) in growing buffaloes. For the purpose, six growing female Murrah buffalo calves of 6-8 months of age were selected on the basis of their BW and fed according to Kearl standard (Nutrient Requirements of Ruminants in Developing Countries, International Feedstuffs Institute, Utah State University, Utah, USA, 1982, p. 89) for growing buffaloes (target growth rate 500 g/day) to meet energy and protein requirement of the animals. Blood samples collected at fortnight intervals for 1 year were analysed for plasma NEFA, glucose, alpha-amino nitrogen and GH. The animals were also weighed at fortnight intervals. Plasma NEFA and glucose levels were found to decrease (p < 0.01) with age. Unlike plasma NEFA and glucose, plasma alpha-amino nitrogen level increased (p < 0.01) as the buffaloes become older. Plasma NEFA and glucose concentrations in growing buffaloes were found to be positively correlated with plasma GH (r = 0.379 and 0.420 respectively), but these were non-significant (p > 0.01). However, plasma NEFA and glucose showed a good correlation (p < 0.01; r = 0.780 and 0.652 respectively) with plasma GH per 100 kg live weight. Plasma alpha-amino nitrogen exhibited non-significant (p > 0.01) negative correlation (r = -0.295) with plasma GH but a negative correlation (p < 0.01; r = -0.641) with GH per 100 kg BW. So, plasma metabolites showed a definite pattern of change during growth and these have a significant (p < 0.01) correlation with plasma GH per 100 kg BW than GH., (Copyright 2004 Blackwell Verlag, Berlin)

Several countries have approved universal folic acid (FA) fortification to prevent neural tube defects and/or high homocysteine levels; this has led to a chronic intake of FA. Traditionally, the vitamin is considered to be safe and nontoxic, except for the potential masking of vitamin B-12 deficiency. Recent reports from our laboratories showed several effects of high-dose folate supplementation in rats. In this work, we compared the effect of FA on the liver of weanling (3 wk) and aged (18 mo) male rats fed either a diet supplemented with 40 mg FA/kg diet or a control diet (1 mg FA/kg diet) for 4 wk. FA supplementation did not alter serum aspartate aminotransferase, alanine aminotransferase, urea, glucose oxidase, total bilirubin, or uric acid. Routine histological staining as well as immunohistochemistry with proliferating cell nuclear antibody for dividing cells, and cytokeratin-8 against bile ductal cells, showed that aged, supplemented rats had the same number of hepatocytes as both control and supplemented weanling rats, and tended to have more (17%, P = 0.07) hepatocytes than aged, control rats. Moreover, the bile duct cells of aged, control rats proliferated and transformed into cholestatic rosettes at a higher frequency than in aged, supplemented rats. The morphology of the liver in weanling rats was similar in both diet groups, and comparable to the supplemented, aged rats, thus indicating that a high intake of FA improves normal liver morphology in livers of aged rats.

We have determined postnatal development and age-related changes in the distribution of neuronal nitric oxide synthase (nNOS) in the visual system including superior colliculus (SC), dorsal nucleus of lateral geniculate body (dLGB) and visual cortex of rats. In SC, the number and intensity of immunoreactive cells were increased until postnatal day 21 (P21), and were comparably decreased during the following days. Both neurons and neuropil were intensely stained in dLGB at P21, and the staining intensity was decreased in aged rats. The number of nNOS-immunoreactive cells was increased from P7 to P28 and was decreased in aged rats. The first demonstration of different staining patterns in SC, dLGB and visual cortex during the postnatal days and aging suggests that NO may mediate both postnatal refinement and age-associated visual deficits in some brain regions.

We evaluated hepatic CYP3A activity during development in male and female rats and the effect of neonatal exposure of 17beta-estradiol and tamoxifen. In untreated and olive oil-treated (control) rats, hepatic CYP3A activities evaluated by erythromycin metabolism in vitro increased several-fold from age 2 to 9 weeks in males. In contrast, activity in females remained at a low and constant level from 2 to 15 weeks. Exposure of 17beta-estradiol to neonates at a dose of 10 micromol/kg daily for 3 days on day 1-3 (approximately) or 4-6 (approximately) after birth significantly increased hepatic CYP3A activity during the developmental period in both males and females, and a greater influence was observed in females exposed during days 4-6 (approximately). Pubertal exposure of 17beta-estradiol (7-weeks old, 10 micromol/kg daily for 3 days) also increased hepatic CYP3A activity, but only in females. Neonatal exposure to tamoxifen (10 micromol/kg daily for 3 days) showed no appreciable effect in either males or females. In conclusion, a marked sex-difference was observed in hepatic CYP3A activity, and exposure of 17beta-estradiol to neonates increased hepatic CYP3A activity during the developmental period, especially in female rats.

We have prepared fresh pituitary gland slices from adult and, for the first time, from newborn mice to assess modulation of secretory activity via voltage-activated Ca(2+) channels (VACCs). Currents through VACCs and membrane capacitance have been measured with the whole-cell patch-clamp technique. Melanotrophs in newborns were significantly larger than in adults. In both newborn and adult melanotrophs activation of VACCs triggered exocytosis. All pharmacologically isolated VACC types contributed equally to the secretory activity. However, the relative proportion of VACCs differed between newborns and adults. In newborn cells L-type channels dominated and, in addition, an exclusive expression of a toxin-resistant R-type-like current was found. The expression of L-type VACCs was up-regulated by the increased oestrogen levels observed in females, and was even more emphasized in the cells of pregnant females and oestrogen-treated adult male mice. We suggest a general mechanism modulating endocrine secretion in the presence of oestrogen and particularly higher sensitivity to treatments with L-type channel blockers during high oestrogen physiological states.

To identify new and differentially expressed genes in rat fetal liver epithelial stem/progenitor cells during their proliferation, lineage commitment, and differentiation, we used a high throughput method-mouse complementary DNA (cDNA) microarrays-for analysis of gene expression. The gene expression pattern of rat hepatic cells was studied during their differentiation in vivo: from embryonic day (ED) 13 until adulthood. The differentially regulated genes were grouped into two clusters: a cluster of up-regulated genes comprised of 281 clones and a cluster of down-regulated genes comprised of 230 members. The expression of the latter increased abruptly between ED 16 and ED 17. Many of the overexpressed genes from the first cluster fall into distinct, differentially expressed functional groups: genes related to development, morphogenesis, and differentiation; calcium- and phospholipid-binding proteins and signal transducers; and cell adhesion, migration, and matrix proteins. Several other functional groups of genes that are initially down-regulated, then increase during development, also emerged: genes related to inflammation, blood coagulation, detoxification, serum proteins, amino acids, lipids, and carbohydrate metabolism. Twenty-eight genes overexpressed in fetal liver that were not detected in adult liver are suggested as potential markers for identification of liver progenitor cells. In conclusion, our data show that the gene expression program of fetal hepatoblasts differs profoundly from that of adult hepatocytes and that it is regulated in a specific manner with a major switch at ED 16 to 17, marking a dramatic change in the gene expression program during the transition of fetal liver progenitor cells from an undifferentiated to a differentiated state. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).

In both vertebrates and invertebrates, the elaboration of locomotion, and its neural control by the central nervous system, are extremely flexible. This is due not only to the network properties of relevant sets of central neurons, but also to the active participation of mutually co-operative central and peripheral loops of neural projections and activity. In this chapter, we describe experiments in which the above concepts have been advanced by comparing locomotor properties in the adult vs. neonatal rat preparation. Data obtained from the in vivo vs. in vitro preparation, and swimming vs. walking behavior, suggest that the locomotor pattern progressively exhibited after birth corresponds to successive steps in the maturation of locomotor networks. Our work emphasises that during the late pre- and early postnatal period, three distinct neural entities--segmental sensory input, descending pathways, and motoneurons--play a key role in the maturation of locomotion and its neural control. We propose that the neonatal rat preparation is an excellent model for studying the conversion from immature to adult locomotion. Some neural controls are more clearly demonstrable in the developing animal preparation than in the adult because the latter exhibits an array of complex and redundant adaptive mechanisms.

On the basis of evidence showing that instantaneous heart rate (IHR) of chick hatchlings responds to exposure to altered ambient temperature (Ta; Tazawa H, Moriya K, Tamura A, and Akiyama R. Comp Biochem Physiol A 131A: 797-803, 2002), we elucidate here the developmental timeline for the homeothermic response of HR in newly hatched chicks (days 0-7) maintained at room temperature ( approximately 24-27 degrees C). Hatchlings were exposed to Ta of 25, 35, and 25 degrees C for 1-h periods, respectively, and IHR was measured together with skin temperature (Ts) during this warming and cooling bout. Early 0-day-old (0 day) chicks responded to warming and cooling exposures with various changes in HR baseline. In newly hatched chicks (0-7 h old), HR baseline was elevated during warming (Delta126 beats/min, n = 13) and declined during cooling (-Delta94 beats/min). With progress of development on day 0, the elevation of HR baseline during warming decreased and advanced 0-day chicks tended to decrease HR baseline during warming rather than increase HR. The more developed 1- to 7-day-old chicks exhibited the expected homeothermic decrease in HR during warming. The diurnal variations of HR responses during warming and cooling on the first day of post-egg life indicate that pronounced development of thermoregulatory competence occurs during the day of hatching (day 0). The response of IHR fluctuations to altered Ta was observed in the form of low- and high-frequency oscillations. High-frequency oscillations corresponding to respiratory sinus arrhythmia developed as the hatchlings aged. There was a significant increase in the number of chicks exhibiting both low- and high-frequency oscillations that depended on age and the development of thermoregulatory competence of hatchlings.

During development, retinal ganglion cells undergo conspicuous structural remodeling as they gradually attain their mature morphology and connectivity. Alterations in their dendritic organization and in their axonal projections can also be achieved following early insult to their targets or their afferents. Other retinal cell types are thought not to display this same degree of developmental plasticity. The present review will consider the evidence, drawn largely from recent experimental studies in the carnivore retina, that photoreceptors also undergo structural remodeling, extending their terminals transiently into inner plexiform layer before retracting to the outer plexiform layer. The determinants of this transient targeting to the inner plexiform layer are considered, and the role of cholinergic amacrine cells is discussed. The factors triggering this retraction are also considered, including the concurrent maturational changes in outer segment formation and in the differentiation of the outer plexiform layer. These results provide new insight into the life history of the photoreceptor cell and its connectivity, and suggest a transient role for the photoreceptors in the circuitry of the inner retina during early development, prior to the onset of phototransduction.

The retinal synaptic network continues its development after birth in mammals. Recent studies show that postnatal development of retinal circuitry depends on visual stimulation. We sought to determine whether there is a time period during which the retina shows evidence of increased plasticity. We examined the effects of light deprivation on the retinal light response of mouse retina using electroretinogram (ERG) measurements. Our results showed that dark rearing mice from birth to postnatal day (P) 30, 60, and 90 suppressed the amplitudes of oscillatory potentials (OPs) and the magnitudes of suppression were age independent. In addition, dark-rearing-produced suppression of OP amplitudes can be completely reversed in both young and adult mice by returning them to cyclic light/dark conditions for 1 to 2 weeks. However, the recovery time course was age dependent with younger animals needing a longer time to achieve a full recovery. Furthermore, dark rearing of P60 mice raised under cyclic light/dark conditions for 30 days resulted in a similar magnitude of suppression of OP amplitudes as in age-matched mice dark reared from birth. These findings demonstrate that both the normal developmental changes and the maintenance of mature inner retinal light response in adult animals require visual stimulation. These results indicate a degree of activity-dependent plasticity in mouse retina that has not been previously described.

The objective of this study is to investigate the relative contributions of maturation to the dynamic behavior of respiration during ontogeny in the neonate. The phrenic neurogram, an output of the respiratory network, was recorded during eupnea at three postnatal ages (3-7, 12-19, and 26-31 days) in decerebrate piglets. The inter-breath interval (IBI) time series were reconstructed from phrenic neurograms for each piglet and analyzed using the approximate entropy (ApEn) method. The mean values of the approximate entropy were high during the first seven days of the postnatal age [1.02 +/- 0.02 (standard error)] and decreased for the 12-19 days (0.67 +/- 0.008) and increased during subsequent maturation [the 26-31 days age group (0.92 +/- 0.015)]. The mean approximate entropy values for the 3-7 days age group was significantly different from those of the 12-19 days age groups (p < 0.05) using the nonparametric statistical test. The complexity values for the 3-7 days age group were slightly higher than those of the 26-31 days age group, but these differences were not statistically significant (p > 0.05). Therefore, these findings suggest that a decrease in the complexity values is unique to the 12-19 days age groups. This could be due to a reduction in the number of dendritic terminals per cell for the 12-19 days age groups. The results of these preliminary experiments also indicate that the behavior of the respiratory pattern generator in the neonate fluctuates during the early maturation period.

Background and Aims: Daily nutrient intake and growth of male Sprague-Dawley (SD) rats fed compositionally different diets were monitored over 114 weeks to determine whether rats fed ad libitum (AL) or diet restricted (DR) followed normal growth parameters. A second objective was to evaluate the usefulness of the American Institutes of Nutrition's AIN-93M (maintenance formulation) diet for aging and DR studies., Methods: Rats were fed NIH-31 cereal-based diet AL, or a vitamin-fortified modification of the NIH-31 diet at 10, 25, or 40% DR. Other SD rats were fed AIN-93M diet AL or 31% DR; daily nutrient intake and growth response were reported., Results: At all intervals up to 36 weeks of age, rats fed AL the NIH-31 diet consumed significantly (p<0.001) more than rats fed AL the AIN-93M diet, and required more diet per unit of gain than AIN-93M AL rats. However, body weight (BW) gain in rats AL-fed the AIN-93M diet demonstrated that energy components were more efficiently metabolized than in those fed the NIH-31 diet. Whereas diet restriction decreased BW, the rate of maturation, i.e., the rate of reaching a mature BW, increased as intake level decreased. Growth response showed all growth curves were normal, but intake level effects on mature BW and maturation rate differed significantly (p<0.001). Curves for rats AL- and DR-fed the AIN-93M diets were similar to those of rats AL- and DR-fed NIH-31 diet formulations, suggesting that diets adequately met growth requirements and supported normal growth parameters of male SD rats when fed AL or DR., Conclusions: A modification in the AIN-93M energy components to reduce total calories and an evaluation of other nutrient profiles could improve its usefulness as a maintenance and aging diet.

We previously applied an intrinsic optical imaging technique to the in vivo rat spinal cord, and showed its feasibility for analyzing neural functions. Three- to 7-week-old postnatal and adult (>10-week-old) rats were anesthetized and laminectomy was performed between C5 and Th1 to expose the dorsal surface of the cervical spinal cord. Optical reflectance changes in response to simultaneous stimulation of the median and ulnar nerves were recorded from the spinal cord at a depth corresponding to the dorsal horn (substantia gelatinosa), using a differential video acquisition system. The shape and extent of the area of the evoked optical signals varied during postnatal development. In 3- to 4-week-old rats, the response area was small and ellipsoidal, and constrictions between spinal segments were not clear. As postnatal ages proceeded, the area expanded in a rostrocaudal direction, and the constrictions became clear. In adult rats, the response area exhibited a segmental pattern. At all ages, the optical responses showed trial-to-trial variations. A semiquantitative analysis of the variations in one spinal segment showed that the variations in a mediolateral direction appeared to decrease slightly with development, although statistical differences were insignificant between ages. The dynamical changes in optical response patterns were discussed in relation to postnatal maturation of neural functions in the spinal cord.

Previously, we reported that cytochrome oxidase (CO) activity in the rat pre-Bötzinger complex (PBC) exhibited a plateau on postnatal days (P) 3-4 and a prominent decrease on P12 (Liu and Wong-Riley, J Appl Physiol 92: 923-934, 2002). These changes were correlated with a concomitant reduction in the expression of glutamate and N-methyl-d-aspartate receptor subunit 1 and an increase in GABA, GABAB, glycine receptor, and glutamate receptor 2. To determine whether changes were limited to the PBC, the present study aimed at examining the expression of CO in a number of brain stem nuclei, with or without known respiratory functions from P0 to P21 in rats: the ventrolateral subnucleus of the solitary tract nucleus, nucleus ambiguus, hypoglossal nucleus, nucleus raphe obscurus, dorsal motor nucleus of the vagus nerve, medial accessory olivary nucleus, spinal nucleus of the trigeminal nerve, and medial vestibular nucleus (MVe). Results indicated that, in all of the brain stem nuclei examined, CO activity exhibited a general increase with age from P0 to P21, with MVe having the slowest rise. Notably, in all of the nuclei examined except for MVe, there was a plateau or decrease at P3-P4 and a prominent rise-fall-rise pattern at P11-P13, similar to that observed in the PBC. In addition, there was a fall-rise-fall pattern at P15-P17 in these nuclei, instead of a plateau pattern in the PBC. Our data suggest that the two postnatal periods with reduced CO activity, P3-P4 and especially P12, may represent common sensitive periods for most of the brain stem nuclei with known or suspected respiratory control functions.

Further knowledge of feline physiology and neonatology is needed because the number of cats being kept as pets and used as experimental animals has increased. Few studies have been published on feline sequential electrocardiography. This study was conducted to determine the values of normal waves, complexes, and intervals of the electrocardiogram in clinically healthy feline neonates. Serial electrocardiography was performed in 15 female and 15 male neonates at 30 days of age. Parameters analyzed were heart rate and rhythm, duration and amplitude of electrocardiographic waves, duration of intervals, and the electrical axis of the heart. The results did not show differences between males and females. During the neonates' first 30 days of life, migration of the electrical axis from right to left was observed. There was a progressive increase in the R wave amplitude, while the S wave amplitude showed a progressive decrease. A sinus heart rhythm was predominant in the feline neonates.

The lancehead snakes Bothrops asper and Bothrops atrox inflict 70-90% of the 3000 bites reported every year in Colombia. In this work, the venoms of B. atrox from Meta (Villavicencio, 33 specimens) and B. asper from Antioquia (San Carlos, 45 specimens), all of them born in captivity, were obtained at different ages (0-6 months; 1, 2 and 3-years old) and compared in terms of their pharmacological and immunochemical characteristics. A conspicuous ontogenetic variability was observed in venom samples from both species. Venoms from newborn and juvenile specimens showed higher lethal, hemorrhagic, edema-forming and coagulant activities, whereas venoms from 3-year old specimens showed higher indirect hemolytic, i.e. phospholipase A2 activity, being more significant in the case of B. asper. SDS-polyacrylamide gel electrophoresis of whole venom for both species evidenced a predominance of high mol. mass bands in the venoms from specimens of <1 year of age, with a change towards bands having lower mol. mass as snakes aged. Gel filtration chromatography showed five peaks in the venoms of B. asper of <6 months and in those from 3-year old specimens. Venom of adult specimens showed a higher number of peaks with indirect hemolytic activity than venom of newborn specimens. Polyvalent antivenom produced in Costa Rica recognized all the bands of both venoms from specimens at all ages tested, when assayed by Western blotting.