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Ibuprofen is an effective pharmacological intervention for closure of a patent ductus arteriosus in preterm infants, and is an alternative to surgical ligation; however it is not certain whether ibuprofen treatment is associated with adverse effects on the brain. Therefore, this study examined neuropathological outcomes of ibuprofen therapy for a patent ductus arteriosus. Fetal baboons were delivered at 125-days of gestation (dg, term ~185dg) by caesarean section, given surfactant and ventilated for 14-days with positive pressure ventilation. Baboons were randomly allocated to receive either ibuprofen (PPV + ibuprofen, n=8) or no therapy (PPV, n=5). Animals were euthanased on day 14 and brains assessed for cerebral growth, development and neuropathology. Body and brain weights, the total volume of the brain and the surface folding index (measure of brain growth) were not different (p>0.05) between PPV + ibuprofen-treated and PPV animals. There was no difference (p>0.05) in the number of myelin basic protein-immunoreactive oligodendrocytes, glial fibrillary acid protein-immunoreactive astrocytes or Iba1-immunoreactive macrophages/microglia in the forebrain. No overt cerebellar alterations were observed in either group. Ibuprofen treatment for patent ductus arteriosus closure in the preterm baboon neonate is not associated with any increased risk of neuropathology or alterations to brain growth and development.

Chronic placental insufficiency (CPI) has the potential to affect fetal brain development and to cause brain injury. Our aim was to determine the effects of exposure to CPI during late gestation on brain and retinal structure and brain neurotrophin expression 8 weeks after birth. Six fetal sheep were exposed to CPI, induced by umbilico-placental embolization, from 120 days of gestation until term (approximately 147 days) such that fetal arterial oxygen saturation (SaO2) was reduced by approximately 50%. Nine untreated animals served as controls. During CPI, fetal arterial PO2, SaO2, pH, and growth were reduced (p0.05); these animals remained small at 8 weeks after birth. Structural abnormalities were present in the brains and retinae of all CPI-exposed lambs. There was a reduction in retinal width and in the number of retinal tyrosine hydroxylase-immunoreactive dopaminergic amacrine cells (p0.05). In the dorsal hippocampus the combined width of strata oriens and pyramidale was significantly reduced (p0.05). In the cerebellum there was a significant reduction (p = 0.05) in cerebellar cross-sectional area, most notably in the inner granule cell layer, and a reduction (p0.05) in immunoreactivity for the cytoskeletal protein neurofilament-200 in the white matter. Gliosis was present in either the cerebral white matter or cerebellum in all animals and degeneration was seen around blood vessels in 4/6 umbilico-placental embolization animals. There were reductions in brain-derived neurotrophic factor immunoreactivity in the hippocampus (p0.05) and tyrosine kinase B immunoreactivity in the cerebellum (p0.05). This study shows that late gestational CPI affects morphology and neurotrophin expression of the postnatal brain. These alterations in the brain can apparently persist from fetal life or become established after birth; some changes that were present in the fetus at term did not persist into postnatal life.

Our aim was to test the hypothesis that the fetal brainstem is relatively spared, compared to other brain regions, from hypoxia-induced damage. We have used established experimental models of acute and chronic intrauterine compromise in sheep to mimic conditions that can arise in human pregnancy. The acute insult was 12 h of placental insufficiency induced by restricted utero-placental blood flow at 90 days of gestation (term approximately 147 days). Five weeks after this insult (n=7 fetuses) there was no overt damage to the brainstem nor were there alterations to the blood vessel morphology, volume of the medulla or of medullary nuclei compared to controls (n=8). This regimen is known to have significant effects on the forebrain and cerebellum. The chronic insult was induced in five fetuses via embolisation of the umbilico-placental circulation from 120 to 140 days of gestation. An additional three fetuses were found to be spontaneously hypoxemic (SH) immediately after surgery. At 140 days, in brainstems of all chronically hypoxemic fetuses compared to controls (n=8), there was an increase (P

Umbilical cord occlusion causes fetal hypoxemia which can result in brain injury including damage to cerebral white matter. Excessive glutamate release may be involved in the damage process. This study examined the relation between extracellular glutamate levels in the cerebral white matter of the ovine fetus during and after intermittent umbilical cord occlusion and the degree of resultant fetal brain injury. Fetal sheep underwent surgery for chronic catheterisation and implantation of an intra-cerebral microdialysis probe at 130 days of gestation (term approximately 147 days). Four days after surgery (day 1), seven fetuses were subjected to 5x2 min umbilical cord occlusions, and on the following day (day 2) they were subjected to either 4 or 5x4 min umbilical cord occlusions; seven fetuses served as controls. Microdialysis samples were collected before, during and after the umbilical cord occlusions to determine extracellular glutamate levels in the cerebral white matter. Fetal blood gas status was measured and the fetal electrocorticogram was recorded continuously. During the periods of umbilical cord occlusions on both days 1 and 2, fetal arterial oxygen saturation, arterial partial pressure of oxygen and arterial pH decreased (P0.05) while arterial partial pressure of carbon dioxide increased (P0.05). All fetuses showed episodes of isoelectric electrocortical activity during umbilical cord occlusions on both days 1 and 2. In fetuses with patent microdialysis probes there were marked increases of glutamate efflux in the cerebral white matter following umbilical cord occlusion. Fetal brains were removed at autopsy on day 5 and subjected to histological assessment. Brain damage was observed in all fetuses exposed to cord occlusion, particularly in the periventricular white matter, with the most extensive damage occurring in the fetuses with the greatest increases in glutamate levels. We conclude that, in the unanesthetised fetus in utero, glutamatergic processes are associated with umbilical cord occlusion-induced brain damage in the cerebral white matter.

Very low birth weight and growth-restricted infants have an increased risk of auditory impairments. It is uncertain whether these impairments are related to adverse pre-, peri- or postnatal events. We aimed to determine whether a period of chronic placental insufficiency (CPI) in the guinea pig results in long-term alterations to auditory function. Near mid-gestation, CPI was induced via unilateral ligation of the uterine artery. At 8 weeks of age, auditory brainstem responses (ABRs) were recorded in response to unilateral acoustic stimulation in prenatally-compromised (PC, n=8) and control animals (n=8). Stimuli consisted of 100 micros clicks, presented at 33 pulses per second (pps) and tone pip stimuli at frequencies of 2, 4, 8, 16 and 32 kHz. To examine temporal response properties, click stimuli were also presented at rates of 66, 132 and 200 pps. Normal ABR waveforms were elicited by both click and tone pip stimuli in all animals. Moreover, there was no difference between control and PC animals in stimulus detection thresholds across the frequencies examined. Using high rate click stimuli, PC animals demonstrated a significant increase in both the latency of wave III (normalised to 33 pps) and the wave I-III inter-peak interval compared to the controls. We hypothesise that these functional changes reflect alterations in myelination of the auditory brainstem and/or changes in synaptic efficacy. The results suggest subtle deficits in neural conduction in the PC guinea pig at maturity, and may have implications for speech perception abilities of low birth weight or prenatally affected infants.

Premature infants now have an improved chance of survival, but the impact of respiratory therapies on the brain, particularly the cerebellum, remains unclear. We examined the effects of early nasal continuous positive airway pressure (EnCPAP) ventilation and delayed (Dn) CPAP on the development of the cerebellum in prematurely delivered baboons. The baboons were delivered at 125 +/- 2days of gestation and ventilated for 28 days with either EnCPAP commencing at 24 hours (n = 5) or DnCPAP commencing at 5 days (n = 5). Gestational controls (n = 4) were delivered at 153 days. Cerebella were assessed histologically, and an ontogeny study (90 days to term) was performed to establish values for key cerebellar developmental indicators. Cerebellar weight was reduced in DnCPAP but not EnCPAP animals versus controls; cerebellar/total brain weight ratio was increased in EnCPAP (p0.05) versus control and DnCPAP animals. There was no overt damage in the cerebella of any animals, but a microstructural alteration index based on morphological developmental parameters and microglial immunoreactivity was increased in both prematurely delivered cohorts versus controls (p0.001) and was higher in DnCPAP than EnCPAP animals (p0.05). These results indicate that respiratory regimens can influence cerebellar development and that early compared with delayed extubation to nCPAP seems to be beneficial.

A patent ductus arteriosus (PDA) alters pulmonary mechanics and regional blood flow in the preterm infant. Its significance with respect to brain injury and brain development are unclear. We evaluated the effects of surgical ductal ligation on the preterm baboon brain. Baboons were delivered at 125 d of gestation (dg, term approximately 185 dg) and ventilated for 14 d (n = 12). The PDA was ligated 6 d after delivery (n = 7) or left untreated (n = 5). Animals were euthanized at 139 dg and brains compared histologically with gestational control fetuses (n = 7) at 140 dg. Brain and body weights were reduced (p < 0.05) in both groups of ventilated preterm animals; however, the brain to body weight ratio was increased (p < 0.01) in ligated, but not unligated newborns compared with gestational controls. No overt lesions were observed in either premature newborn group. Astrocyte density in the neocortex and hippocampus were greatest in the unligated newborns (p < 0.01). Myelination and oligodendrocytes were reduced (p < 0.05) in both premature newborn groups. The brain growth and development index was reduced, and the damage index was increased in prematurely delivered baboons. Surgical ligation of the PDA does not increase the incidence of brain injury and may be beneficial if the PDA is contributing to persistent pulmonary and hemodynamic instability.

Prenatal hypoxia affects neuronal survival and process outgrowth. Brain-derived neurotrophic factor, which influences neural growth, is decreased in these conditions. We tested whether addition of brain-derived neurotrophic factor enhances growth of neurons cultured from guinea pig fetuses (n=7) compromised by chronic placental insufficiency from 30-52 days gestation (term approximately 67 days). Cultures were prepared from the olfactory bulb, hippocampus and cerebellum. Compared with controls (n=7), chronic placental insufficiency resulted in reduced total neurite length in olfactory bulb cultures. Brain-derived neurotrophic factor treatment for 5 days increased the total olfactory neurite length and somal size and number of primary neurites in all cultures from both control and compromised animals. Thus, brain-derived neurotrophic factor can influence the growth of compromised fetal neurons supporting its therapeutic use following chronic placental insufficiency.

The aim of this study was to determine the effects of foetal growth restriction on the retina after birth. Foetal growth restriction (FGR) was induced via umbilico-placental embolization (UPE) in ewes from 120 days of pregnancy until term (term approximately 147 days); controls were not exposed to UPE. Lambs were delivered and raised until 2 years of age when retinas were collected and processed for structural and neurochemical analysis. The foetuses exposed to UPE were hypoxemic and at birth were growth restricted. In 2-year-old FGR sheep, the total thickness of the retina and the number of tyrosine hydroxylase immunoreactive dopaminergic amacrine cells were reduced compared to controls (P < 0.05). It is concluded that restricted foetal growth leads to long-term structural and neurochemical changes in the retina. Of particular interest are the alterations to dopaminergic amacrine cell numbers, as alterations in this population may affect contrast sensitivity and have implications for the alterations in vision observed in very low birthweight infants.

Intrauterine growth restriction is a risk factor for neurological and behavioural deficits in children although the precise underlying biological correlate for this is unclear. The present study shows that animals with intrauterine growth restriction, induced by a period of reduced placental blood flow during the second half of pregnancy, demonstrate reduced numbers of neurons in the hippocampus and the cerebellum in conjunction with retarded dendritic and axonal growth within these structures. Intrauterine growth restriction was induced at 30 days gestational age by unilateral uterine artery ligation in pregnant guinea-pigs. At one week of age, the total number of CA1 pyramidal neurons in the hippocampus and the Purkinje neurons in the cerebellum were determined using the combined fractionator/optical disector technique. The Cavalieri Principle was used to determine the volume of specific regions within the hippocampus and cerebellum. The body weight of animals that were classified as intrauterine growth-restricted was reduced by 42% (n=8) compared with control animals (n=8, P

Very low birth weight (VLBW) and fetal growth restriction are associated with increased risks of long-term visual impairments, including alterations to contrast sensitivity, a parameter mediated in part by dopaminergic amacrine cells. This study was conducted to determine whether chronic placental insufficiency (CPI), sufficient to cause growth restriction, results in neurochemical alterations to retinal interneurons, specifically amacrine and horizontal cell populations near term.CPI was induced just before midgestation (term approximately 67 days of gestation, dg) in guinea pigs through unilateral ligation of the uterine artery. Growth-restricted (GR, n = 32) and control (n = 29) fetuses were euthanized at 60 dg and retinas prepared for analysis of amacrine cell populations by using antibodies to calbindin, calretinin, cholineacetyltransferase (ChAT), gamma-amino-butyric acid (GABA), dopamine beta-hydroxylase (D beta H), tyrosine hydroxylase (TH, dopaminergic), and NADPH-diaphorase histochemistry (nitrergic). Calbindin immunoreactivity (IR) was also used to identify horizontal cells. HPLC was used to assess concentrations of catecholamines and Western blot analysis to detect total TH levels.In GR compared with control fetuses the total number of TH-IR amacrine (P0.02) and calbindin-IR horizontal (P0.05) cells was reduced; however, there were no differences in the number of the ChAT, calbindin, calretinin, GABAergic, or nitrergic amacrine cell populations. HPLC revealed a reduction in the concentration of dopamine (P0.05) and noradrenaline (P0.05), and Western blot analysis revealed a reduction in TH in the retinas of GR compared with control fetuses (P0.05).CPI results in alterations to specific populations of retinal neurons. Such effects could contribute to visual impairments reported for VLBW children.