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Marine species exhibit a multitude of biological rhythms, in accordance with their complex ecosystem governed by sun, earth and moon trajectories. Because of the inclination of the earth's axis, the high Arctic ecosystem is characterized by several months of permanent illumination during the polar day. The persistence of biological rhythms in this photic context remains unclear. Yet, this information is crucial for the understanding of polar ecosystems functioning, as well as to predict the impact of future climate changes. Particularly, the impact of extreme photoperiods on recent invasive species remains largely unknown. Here, we investigate how environmental cycles shape the behavior of a re-emerging polar resident, the mussel Mytilus sp. during polar day (17 April to 26 August 2020; Svalbard, Ny-Ålesund, 78°56E N, 11°56E E). Our results show that in the high Arctic polar day, mussels' behavior is shaped by both the photoperiod and the diel sun trajectories above the horizon. In addition, mussels also exhibit tidal, semi-lunar, and lunar rhythms of valve opening amplitude. We argue that these rhythms may have ecosystems functioning implications, and that the mussels' ability to deal with drastic light regimes may explain their northward expansion and new resettlement in high Arctic., Author(s): Alexandre Le Moal [sup.1] , Laura Payton [sup.1] [sup.2] , Hector Andrade [sup.3] , Lionel Camus [sup.4] , Carl Ballantine [sup.4] , Pierre Ciret [sup.1] [sup.2] , Damien Tran [...]

In vertebrate somitogenesis, the expression of segmentation clock genes oscillates and the oscillation is synchronized over nearby cells. Both experimental and theoretical studies have shown that the synchronization among cells is realized by intercellular interaction via Delta-Notch signaling. However, the following questions emerge: (i) During somitogenesis, dynamic rearrangement of relative cell positions is observed in the posterior presomitic mesoderm. Can a synchronized state be stably sustained under random cell movement? (ii) Experimental studies have reported that the synchronization of cells can be recovered in about 10 or fewer oscillation cycles after the complete loss of synchrony. However, such a quick recovery of synchronization is not possible according to previous theoretical models. In this paper, we first show by numerical modeling that synchronized oscillation can be sustained under random cell movement. We also find that for initial perturbation, the synchronization of cells is recovered much faster and it is for a wider range of reaction parameters than the case without cell movement. When the posterior presomitic mesoderm is rectangular, faster synchronization is achieved if ceils exchange their locations more with neighbors located along the longer side of the domain. Finally, we discuss that the enhancement of synchronization by random cell movement occurs in several different models for the oscillation of segmentation clock genes. zebrafish | somitogenesis | Delta-Notch | mathematical models doi/ 10.1073/pnas.0907122107

Hoogerwerf WA, Shahinian VB, Cornelissen G, Halberg F, Bostwick J, Timm J, Bartell PA, Cassone VM. Rhythmic changes in colonic motility are regulated by period genes. Am J Physiol Gastrointest Liver Physiol 298: G143-G150, 2010. First published November 19, 2009; doi: 10.1152/ajpgi.00402.2009.--Human bowel movements usually occur during the day and seldom during the night, suggesting a role for a biological clock in the regulation of colonic motility. Research has unveiled molecular and physiological mechanisms for biological clock function in the brain; less is known about peripheral rhythmicity. This study aimed to determine whether clock genes such as period I (per1) and period2 (per2) modulate rhythmic changes in colonic motility. Organ bath studies, intracolonic pressure measurements, and stool studies were used to examine measures of colonic motility in wild-type and per1per2 double-knockout mice. To further examine the mechanism underlying rhythmic changes in circular muscle contractility, additional studies were completed in neuronal nitric oxide synthase (nNOS) knockout mice. Intracolonic pressure changes and stool output in vivo, and colonic circular muscle contractility ex vivo, are rhythmic with greatest activity at the start of night in nocturnal wild-type mice. In contrast, rhythmicity in these measures was absent in perlper2 double-knockout mice. Rhythmicity was also abolished in colonic circular muscle contractility of wild-type mice in the presence of [N.sup.[omega]]-nitro-L-arginine methyl ester and in nNOS knockout mice. These findings suggest that rhythms in colonic motility are regulated by both clock genes and a nNOS-mediated inhibitory process and suggest a connection between these two mechanisms. biological rhythms; clock genes; circadian; nNOS doi: 10.1152/ajpgi.00402.2009

Phase-amplitude cross-frequency coupling (CFC) between theta (4-12 Hz) and gamma (30-100 Hz) oscillations occurs frequently in the hippocampus. However, it still remains unclear whether theta--gamma coupling has any functional significance. To address this issue, we studied CFC in local field potential oscillations recorded from the CA3 region of the dorsal hippocampus of rats as they learned to associate items with their spatial context. During the course of learning, the amplitude of the low gamma subband (30-60 Hz) became more strongly modulated by theta phase in CA3, and higher levels of theta--gamma modulation were maintained throughout overtraining sessions. Furthermore, the strength of theta--gamma coupling was directly correlated with the increase in performance accuracy during learning sessions. These findings suggest a role for hippocampal theta--gamma coupling in memory recall. associative memory | brain rhythms | local field potential doi/10.1073/pnas.0911331106

Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans. Am J Physiol Cell Physiol 297: C1071-C1081, 2009. First published September 9, 2009; doi:10.1152/ajpcell.00284.2009.--In Caenorhabditis elegans, oscillations of intestinal pH contribute to the rhythmic defecation behavior, but the acid-base transport mechanisms that facilitate proton movement are not well understood. Here, we demonstrate that VHA-6, an intestine-specific a-subunit of the [H.sup.+]-[K.sup.+]-ATPase complex (V-ATPase), resides in the apical membrane of the intestinal epithelial cells and is required for luminal acidification. Disruption of the vha-6 gene led to early developmental arrest; the arrest phenotype could be complemented by expression of a fluorescently labeled vha-6 transgene. To study the contribution of vha-6 to pH homeostasis in larval worms, we used a partial reduction of function through postembryonic single-generation RNA interference. We demonstrate that the inability to fully acidify the intestinal lumen coincides with a defect in pH recovery of the intestinal epithelial cells, suggesting that VHA-6 is essential for proton pumping following defecation. Moreover, intestinal dipeptide accumulation and fat storage are compromised by the loss of VHA-6, suggesting that luminal acidification promotes nutrient uptake in worms, as well as in mammals. Since acidified intracellular vesicles and autofluorescent storage granules are indistinguishable between the vha-6 mutant and controls, it is likely that the nutrient-restricted phenotype is due to a loss of plasma membrane V-ATPase activity specifically. These data establish a simple genetic model for proton pump-driven acidification. Since defecation occurs at 45-s intervals in worms, this model represents an opportunity to study acute regulation of V-ATPase activity on a short time scale and may be useful in the study of alternative treatments for acid-peptic disorders. biorhythm; nematode; proton doi: 10.1152/ajpcell.00284.2009.

We examine foraging behavior of coastal black bears (Ursus americanus kermodei) during different light regimes on a salmon stream in British Columbia, Canada (2000-2002). Bears (maximum 7 simultaneously) were primarily active during daylight near the onset of the salmon spawning run and shifted to twilight and darkness as the spawning run progressed. Overall time budget included search and pursuit (58%), handling and ingestion (38%), and agonistic interactions with other bears (4%). Scavenging was greatest during daylight (19%) and lowest during darkness (3%). Bears were most efficient at capturing live salmon when standing (35.4% success) followed by running (20.5%) and walking (15.2%). Highest capture efficiency occurred during twilight (33.6%) compared with daylight (26.5%) and darkness (24.7%). Capture rate ranged from 1 to 3 salmon per hour per bear. Our results suggest that bears increased their total salmon intake by alternate use of visual and auditory cues during daylight and darkness. Key words: darkness, foraging efficiency, Oncorhynchus, sensory modes, twilight, Ursus

It is well known that fatty acid biosynthesis in leaves is closely related to photosynthesis; although a residual synthesis is also detected at night. But less known is the effect of the day-night cycle in fatty acid biosynthesis in heterotrophic tissues such as developing seeds. Through the use of radioactive precursors, we detected variations in the metabolism of fatty acids and lipids during the day--night period in sunflower (Helianthus annuus L.) seeds. These oscillations have been observed both in the fatty acids bound to triacylglycerols and in polar lipids, indicating a fine regulation of the lipids biosynthetic activities in sunflower developing seeds. Additionally, in the triacylglycerol fraction, periodic variations were observed in the oleic and linoleic acids content as a consequence of qualitative variations in the biosynthetic machinery during the day--night period related to temperature changes. Analyzing the rate of oleic acid desaturation, we observed a significant increase in activity in the middle of the night, indicative of the importance of nocturnal desaturation. Similar variations were also observed in the stearoyl-acyl carrier protein (ACP) desaturase activity. This study has shown the variation in the lipid biosynthetic capacity in sunflower developing seeds during the day--night cycle--including control over individual enzymes such as the stearoyl-ACP desaturase--and the influence of diurnal and nocturnal temperatures in the quality (oleic/linoleic ratio) of the oil.

Understanding how nutrients affect gene expression will help us to understand the mechanisms controlling plant growth and development as a function of nutrient availability. Nitrate has been shown to serve as a signal for the control of gene expression in Arabidopsis. There is also evidence, on a gene-by-gene basis, that downstream products of nitrogen (N) assimilation such as glutamate (Glu) or glutamine (Gin) might serve as signals of organic N status that in turn regulate gene expression. To identify genome-wide responses to such organic N signals, Arabidopsis seedlings were transiently treated with ammonium nitrate in the presence or absence of MSX, an inhibitor of glutamine synthetase, resulting in a block of Glu/GIn synthesis. Genes that responded to organic N were identified as those whose response to ammonium nitrate treatment was blocked in the presence of MSX. We showed that some genes previously identified to be regulated by nitrate are under the control of an organic N-metabolite. Using an integrated network model of molecular interactions, we uncovered a subnetwork regulated by organic N that included CCA1 and target genes involved in N-assimilation. We validated some of the predicted interactions and showed that regulation of the master clock control gene CCA1 by Glu or a Glu-derived metabolite in turn regulates the expression of key N-assimilatory genes. Phase response curve analysis shows that distinct N-metabolites can advance or delay the CCA1 phase. Regulation of CCA 1 by organic N signals may represent a novel input mechanism for N-nutrients to affect plant circadian clock function. circadian | gene networks | glutamate | metabolism

The timing of puberty is a critical life history trait of short-lived species; spring-born individuals mature rapidly and breed in the season of birth, whereas young born in mid-to late summer delay puberty until the next spring. The cues that govern the transition from rapid to delayed maturation in natural populations remain unknown. To identify ecologically relevant photoperiod cues that control timing of puberty, we monitored nine cohorts of female Siberian hamsters (Phodopus sungorus) born every 2 wk from 4 wk before to 12 wk after the summer solstice in a simulated natural photoperiod (SNP). Hamsters born by the summer solstice underwent rapid somatic growth and achieved puberty that summer; among females born 2-4 wk after the solstice, some delayed puberty by many weeks, whereas others manifested early puberty. Hamsters born 6 or more weeks after the solstice generally delayed puberty until the following spring. The transition from accelerated to delayed pubertal development in the SNP occurred at day lengths that induce early puberty when presented as static photoperiods. Despite differences in timing of birth and timing of puberty, fall and subsequent spring seasonal events occurred at similar calendar dates in all cohorts. We found no evidence that prenatal photoperiod history influenced postnatal development of female hamsters. Considered together with a parallel study on males, the present findings point to sex differences in responsiveness to natural photoperiod variations. In both sexes, incrementally changing photoperiods exert a strong organizing effect on seasonal rhythms. Phodopus sungorus; seasonality; sex differences; critical day length doi: 10.1152/ajpregu.00216.2007

Many social interactions rely upon mutual information exchange: one member of a pair changes in response to the other while at the same time producing actions that alter the behavior of the other. However, little is known about how such social processes are integrated in the brain. Here, we used a specially designed dual-electroencephalogram system and the conceptual framework of coordination dynamics to identify neural signatures of effective, real-time coordination between people and its breakdown or absence. High-resolution spectral analysis of electrical brain activity before and during visually mediated social coordination revealed a marked depression in occipital alpha and rolandic mu rhythms during social interaction that was independent of whether behavior was coordinated or not. In contrast, a pair of oscillatory components ([phi.sub.1] and [phi.sub.2]) located above right centroparietal cortex distinguished effective from ineffective coordination: increase of [phi.sub.1] favored independent behavior and increase of [phi.sub.2] favored coordinated behavior. The topography of the phi complex is consistent with neuroanatomical sources within the human mirror neuron system. A plausible mechanism is that the phi complex reflects the influence of the other on a person's ongoing behavior, with [phi.sub.1] expressing the inhibition of the human mirror neuron system and [phi.sub.2] its enhancement. brain oscillations | electroencephalography | mirror neuron system | phi rhythm | coordination dynamics

Accuracy in cellular function has to be achieved despite random fluctuations (noise) in the concentrations of different molecular constituents inside and outside the cell. The circadian oscillator in cyanobacteria is an example of resilience to noise. This resilience could be either the consequence of intercellular communication or the intrinsic property of the built-in biochemical network. Here we investigate the intercellular coupling hypothesis. A short theoretical depiction of interacting noisy phase oscillators, confirmed by numerical simulations, allows us to discriminate the effect of coupling from noise. Experimentally, by studying the phase of concurrent populations of different initial phases, we evaluate a very small upper limit of the intercellular coupling strength. In addition, in situ entrainment experiments confirm our ability to detect a coupling of the circadian oscillator to an external force and to describe explicitly the dynamic change of the mean phase. We demonstrate, therefore, that the cyanobacterial clock stability is a built-in property as the intercellular coupling effect is negligible. biological clock | bioluminescence | dynamics | synechoccocus

The diurnal variation in the incidence of myocardial infarction and stroke may reflect an influence of the molecular clock and/or the time dependence of exposure to environmental stress. The circadian variation in blood pressure and heart rate is disrupted in mice, Bmal[1.sup.-/-], [Clock.sup.mut], and Npas[2.sup.mut], in which core clock genes are deleted or mutated. Although Bmal1 deletion abolishes the 24-h frequency in cardiovascular rhythms, a shorter ultradian rhythm remains. Sympathoadrenal function is disrupted in these mice, which reflects control of enzymes relevant to both synthesis (phenylethanolamine N-methyl transferase) and disposition (monoamine oxidase B and catechoI-O-methyl transferase) of catecholamines by the clock. Both timing and disruption or mutation of clock genes modulate the magnitude of both the sympathoadrenal and pressor but not the adrenocortical response to stress. Despite diurnal variation of catecholamines and corticosteroids, they are regulated differentially by the molecular clock. Furthermore, the clock may influence the time-dependent incidence of cardiovascular events by controlling the integration of selective asynchronous stress responses with an underlying circadian rhythm in cardiovascular function. catecholamine | clock

Time-delay circuitries in which a transcription factor processes independent input parameters can modulate NF-[kappa]B activation, manage quorum-sensing cross-talk, and control the circadian clock. We have constructed a synthetic mammalian gene network that processes four different input signals to control either immediate or time-delayed transcription of specific target genes. BirA-mediated ligation of biotin to a biotinylation signal-containing VP16 transactivation domain triggers heterodimerization of chimeric VP16 to a streptavidin-linked tetracycline repressor (TetR). At increasing biotin concentrations up to 20 nM, TetR-specific promoters are gradually activated (off to on, input signal 1), are maximally induced at concentrations between 20 nM and 10 [micro]M, and are adjustably shut off at biotin levels exceeding 10 [micro]M (on to off, input signal 2). These specific expression characteristics with a discrete biotin concentration window emulate a biotin-triggered bandpass filter. Removal of biotin from the culture environment (input signal 3) results in time-delayed transgene expression until the intracellular biotinylated VP16 pool is degraded. Because the TetR component of the chimeric transactivator retains its tetracycline responsiveness, addition of this antibiotic (input signal 4) overrides biotin control and immediately shuts off target gene expression. Biotin-responsive immediate, bandpass filter, and time-delay transcription characteristics were predicted by a computational model and have been validated in standard cultivation settings or biopharmaceutical manufacturing scenarios using trangenic CHO-K1 cell derivatives and have been confirmed in mice. Synthetic gene circuitries provide insight into structure-function correlations of native signaling networks and foster advances in gene therapy and biopharmaceutical manufacturing. biological circuit | biopharmaceutical manufacturing | gene switch | synthetic biology | biotin

Over the past generation, aging and female reproduction have been lodged within the gendered and gendering debates regarding women's involvement in the workforce and demographic shifts toward delayed parenting that culminate in discourses on the 'biological clock'. Technological solutions to the biological clock, specifically in vitro fertilization, have led to clinical attempts to assess 'ovarian reserve', or qualitative and quantitative changes in the ovary that correlate with aging and with successful infertility treatment. Rupturing the longstanding historical connections between menstruation and female reproductive capacity by specifically focusing on the aging of a woman's eggs, the clinical designation of 'diminished ovarian reserve' has come to imply that a woman has 'old eggs'. This is associated in practitioners' and patients' minds with the eclipse of a woman's reproductive potential and with hidden harbingers of menopause. In an ethnographic interview study of 79 couples in the US who conceived after using donor oocytes, we found that women voiced two different narratives that described their experience and attitudes when confronted with an apparent age-related decline in their fertility. The 'eleventh-hour mom' narrative was voiced by women who initially tried to become pregnant with their own eggs and turned to donated oocytes as a second-choice option, whereas the 'miracle mom' narrative was expressed by women who were generally older, some of whom had entered infertility treatment hoping to conceive with their own eggs, but some who knew from the outset that it was not going to be possible. Through their narratives women not only embodied and made meaningful 'diminished ovarian reserve' in varying ways that connect with cultural, social, structural/organizational, symbolic and physical aspects of aging, they reproduced the sociobiological project of the biological clock, but rooted this social project in the metaphor of 'old eggs' rather than menopause. Keywords: Infertility; Age; Donor egg; Biological clock; US

KaiA, KaiB, and KaiC clock proteins from cyanobacteria and ATP are sufficient to reconstitute the KaiC phosphorylation rhythm in vitro, whereas almost all gene promoters are under the control of the circadian clock. The mechanism by which the KaiC phosphorylation cycle drives global transcription rhythms is unknown. Here, we report that RpaA, a potential DNA-binding protein that acts as a cognate response regulator of the KaiC-interacting kinase SasA, mediates between KaiC phosphorylation and global transcription rhythms. Circadian transcription was severely attenuated in sasA (Synechococcus adaptive sensor A)- and rpaA (regulator of phycobilisome-associated)-mutant cells, and the phosphotransfer activity from SasA to RpaA changed dramatically depending on the circadian state of a coexisting Kai protein complex in vitro. We propose a model in which the SasA-RpaA two-component system mediates time signals from the enzymatic oscillator to drive genome-wide transcription rhythms in cyanobacteria. Moreover, our results indicate the presence of secondary output pathways from the clock to transcription control, suggesting that multiple pathways ensure a genome-wide circadian system. biological clock | response regulator | phosphorelay | Synechococcus

Role of histone-modifying enzymes on developmental timing of Dictyostelium is presented.

Abstract The authors report the results of their study aimed at investigating the consequence of targeted ablation of ventral lateral neurons (L[N.sub.v]s--neurons regulating eclosion and locomotor activity rhythms) and genetic [...]

Links between neonatal biological rhythms and the emergence of interaction rhythms were examined in 3 groups (N = 71): high-risk preterms (HR; birth weight < 1,000 g), low-risk preterms (LR; birth weight = 1,700-1,850 g), and full-term (FT) infants. Once a week for premature infants and on the 2nd day for FT infants, sleep-wake cyclicity was extracted from 4-hr observations and cardiac vagal tone was measured. At term age, infant orientation was tested with the Neonatal Behavior Assessment Scale. At 3 months, arousal modulation and emotion regulation were assessed, and mother-infant synchrony was computed from microanalysis of face-to-face interactions using time-series analysis. Sleep-wake amplitudes showed a developmental leap at 31 weeks gestation, followed by a shift in vagal tone at 34 weeks gestation. At term, differences among FT, LR, and HR infants were observed for biological rhythms in a linear-decline pattern. Sleep-wake cyclicity, vagal tone, newborn orientation, and arousal modulation were each uniquely predictive of mother-infant synchrony. The organization of physiological oscillators appears to lay the foundation for the infant's capacity to partake in a temporally matched social dialogue. Keywords: mother-infant synchrony, sleep-wake cyclicity, vagal tone, premature infants, arousal

Pituitary growth hormone (GH)-secreting cells regulate growth and metabolism in animals and humans. To secrete highly ordered GH pulses (up to 1,000-fold rise in hormone levels in vivo), the pituitary GH cell population needs to mount coordinated responses to GH secretagogues, yet GH cells display an apparently heterogeneous scattered distribution in 2D histological studies. To address this paradox, we analyzed in 3D both positioning and signaling of GH cells using reconstructive, two-photon excitation microscopy to image the entire pituitary in GH-EGFP transgenic mice. Our results unveiled a homologous continuum of GH cells connected by adherens junctions that wired the whole gland and exhibited the three primary features of biological networks: robustness of architecture across lifespan, modularity correlated with pituitary GH contents and body growth, and connectivity with spatially stereotyped motifs of cell synchronization coordinating cell activity. These findings change our view of GH cells, from a collection of dispersed cells to a geometrically connected homotypic network of cells whose local morphology and connectivity can vary, to alter the timing of cellular responses to promote more coordinated pulsatile secretion. This large-scale 3D view of cell functioning provides a powerful approach to identify and understand other networks of endocrine cells that are thought to be scattered in situ. Many dispersed endocrine systems exhibit pulsatile outputs. We suggest that cell positioning and associated cell-cell connection mechanisms will be critical parameters that determine how well such systems can deliver a coordinated secretory pulse of hormone to their target tissues. biological rhythms | endocrinology | systems biology | connectivity | calcium

Abstract 'Splitting' of circadian activity rhythms in Syrian hamsters maintained in constant light appears to be the consequence of a reorganized SCN, with left and right halves oscillating in antiphase; [...]

Biological rhythms with lunar components are common in nature. In the sea, the moon's gravitational pull on earth is the principal cause of the tides, which normally reach maximum amplitudes every new and full moon. Many populations synchronize spawning to this time. Some choose either the new or the full moon, implying that moonlight is important; but one lunar phase usually has higher tides than the other, and many species select the phase with the higher tide to improve the offshore transport of their progeny. However, tidal dominance by one lunar phase is not constant; it switches between new and full moon every seven months. We tested the influence of this 14-month 'syzygy inequality cycle' (SIC) on lunar synchrony by sampling 11 populations of intertidal crabs at two locations in East Africa for 21 months. Eight populations synchronized larval release with the SIC. Tidal cues were more important than moonlight in entraining the reproductive rhythm, although two populations synchronized spawning to the new moon. SIC synchrony increased with population shore level, because only the higher lunar tide permitted topshore spawning. Top-shore species therefore have a restricted lunar choice. SIC synchrony could be common, given that it occurs in most marine environments. Key words: crabs; reproductive rhythm; reproductive synchrony; synodic cycle; tidal rhythm; tropics; Uca.

Light is the most important factor controlling circadian systems in response to day-night cycles. In order to better understand the regulation of circadian rhythms by light in Synechococcus elongatus PCC 7942, we screened for mutants with defective phase shifting in response to dark pulses. Using a 5-h dark-pulse protocol, we identified a mutation in kaiC that we termed prl, for phase response 1. In the prl mutant, a 5-h dark pulse failed to shift the phase of the circadian rhythm, while the same pulse caused a 10-h phase shift in wild-type cells. The rhythm in accumulation of KaiC was abolished in the pr1 mutant, and the rhythmicity of KaiC phosphorylation was reduced. Additionally, the prl mutant was defective in mediating the feedback inhibition of kaiBC. Finally, overexpression of mutant KaiC led to a reduced phase shift compared to that for wild-type KaiC. Thus, KaiC appears to play a role in resetting the cellular clock in addition to its documented role in the feedback regulation of circadian rhythms.

Abstract Parathyroid gland secretory activity exhibits seasonal and circadian fluctuations, which are in synchrony with changes in serum calcium, phosphate, and bone turnover. In addition, an ultradian rhythm exists, which [...]

Byline: O. S. Glazachev (1), S. Ya. Klassina (2) Abstract: The effects of local (nasolabial triangle) rhythmical thermal influences synchronized with the breathing rhythm on the functional state were studied. When thermal stimuli were weak, the functional state of subjects was determined by the perception and identification of the stimuli. The [alpha] rhythm dominated in the EEG, and the autonomic status of the subjects did not differ much from the baseline. With increasing intensity of the thermal stimuli, the natural mechanisms of self-regulation were triggered, parasympathetic effects on the heart increased, and slow (I, and I) waves appeared in the EEG. Thermal stimuli with a high intensity caused a psychophysiological state similar to that of altered consciousness. The EEG was characterized by dominance of I waves, and the autonomic activity involved an increased parasympathetic component, the functional activity was reduced, and the subjects noted somnolence and a feeling of heaviness and warmth in the limbs. Author Affiliation: (1) Sechenov Moscow Medical Academy, Moscow, Russia (2) Anokhin Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow, 103009, Russia Article History: Registration Date: 26/12/2004

Byline: E. V. Karnaukhova (1), A. V. Karnaukhov (1) Abstract: A linear regression model has been constructed for estimating human biological age, with the parameters of heart rhythmic activity being used as biological markers. One of the advantages of using these parameters as biological markers of aging is the possibility to measure a number of parameters for an individual subject in a brief (6--7 min) procedure of rhythmogram recording. This makes the collection of data for a statistically reliable sample much easier, increases the accuracy of the model, and permits its use along with other methods for mass examinations of a population and for control of the effects of drugs and food additives. The model may be extended and supplemented with other biological markers in order to improve the approximation of biological age. Author Affiliation: (1) Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow oblast, 142292, Russia Article History: Registration Date: 28/12/2004

Byline: N. A. Agadzhanyan (1), M. I. Panina (2), G. S. Kozupitsa (2), O. S. Sergeev (2) Abstract: Detailed analysis of the subjective sensations of 135 healthy subjects during 20- to -30 min voluntary hyperventilation was performed. The hyperventilation levels (V .sub.EI = 20 l/min, V .sub.EII = 30 l/min, V .sub.EIII = 40 l/min) were chosen so that manifestations of paroxysms of hyperventilation syndrome (HVS) of different severity were simulated. Regular features in the time course of development of HVS symptoms were revealed: (1) specific peripheral subjective sensations and symptoms changed consistently, being peculiar sensory equivalents (correlates) of hyperventilation-related changes in gaseous metabolism and acid-base balance (2) sensations and symptoms of central origin developed in waves, with considerable individual variations in manifestation and emotional hue and were closely correlated with changes in systemic hemodynamics and brain circulation disorders. Author Affiliation: (1) Russian University of Peoples' Friendship, Moscow, Russia (2) State Medical University, Russia Article History: Registration Date: 16/01/2005

Extensive research has demonstrated that shiftwork produces deleterious effects on health because of the desynchrony it induces in the biological clock. The problem is even more crucial for older workers who present, in addition, various decrements in their cognitive functioning, particularly on attention and memory. The present study assessed whether age was related to task complexity as a function of time of day and time-on-task in a rapid rotating work-rest schedule. 24 subjects (12 juniors: 20-30 years and 12 seniors: 50-60 years) performed either a simple task (visual discrimination) or a complex task (descending subtraction) on three different moments of the day simulating the main shifts (morning, evening, and night). Analysis indicated that an age effect was only present on the more complex task, which was demanding in attentional resources and memory load. Seniors had no deficit in performance on the simple task compared to juniors. The effect of time of day was restricted to the simple task for both age groups. However, some differential strategies appear to distinguish juniors and seniors, specifically on accuracy during the night, suggesting that subjects of different ages cope with cognitive tasks in different ways and that perhaps some adverse effects apparently associated with aging could be counteracted by efficient strategies, but not others.

There is pronounced seasonal plasticity in the morphology of the neural circuits that regulate song behavior in adult songbirds, primarily in response to changes in plasma testosterone (T) levels. Most song nuclei have androgen receptors. Afferent input from the telencephalic nucleus HVc (also known as the 'high vocal center') is necessary for seasonal growth of the direct efferent target nuclei RA and area X. We asked here whether T-stimulated growth of HVc is sufficient to induce growth of its efferent nuclei. Intracerebral T implants were placed unilaterally near HVc or RA in photosensitive adult male white-crowned sparrows for one month. The T implant near HVc produced significant growth of the ipsilateral (but not contralateral) HVc, RA, and area X, and increased neuronal number in the ipsilateral HVc. The T implant near RA did not produce selective growth of ipsilateral RA, HVc, or area X. Intracerebral T implants did not elevate plasma T levels, nor did they stimulate growth of two peripheral androgen sensitive targets, the syrinx and the cloacal protuberance. These results suggest that seasonal growth of the adult song circuits results from T acting directly on HVc, which then stimulates the growth of RA and area X transynaptically.

During a 2 y study (February 1993-January 1995) I searched a total of 519.4 km of canal and levee banks in 304.4 h to study Florida kingsnake (Lampropeltis getula floridana) activity. I gathered and compared data on seasonal activity patterns of two populations in southern peninsular Florida, around Lake Okeechobee and southern Dade County. Snakes from both populations exhibited two activity peaks, one in spring and one in fall. The highest frequency of encounters was in March and April during the peak of the breeding season. During this time males were encountered more often than females, possibly because they are actively searching for mates. Encounter rates are constrained by temperature rather than precipitation. The majority of snakes were found in the open aboveground between 24 C to 29 C, with the highest frequency at 27 C. At lower and higher temperatures encounter rates decreased as snakes may retreat into refugia. Adults were encountered more often than juveniles. Adults are primarily diurnal, whereas juveniles exhibit crepuscular and nocturnal behaviors. An apparent ontogenetic shift in diel activity occurred at approximately 90 cm SVL, where secretive juveniles gradually become more diurnal.

Byline: S. A. Kotel'nikov (1), A. D. Nozdrachev (2), M. M. Odinak (1), E. B. Shustov (1), I. Yu. Kovalenko (3), V. Yu. Davydenko (1) Abstract: Physiological mechanisms of cardiac rhythm variability (CRV) are reviewed. The results of original experiments are discussed together with the history of the problem and data available from the literature. Special emphasis is placed on the spectral analysis of cardiac rhythm. Various mechanisms of the generation of periodic and aperiodic components of CRV are considered. Although the variability of cardiac rhythm has been studied for many years in many laboratories worldwide, fine mechanisms of CRV remain obscure. However, a number of specific features of CRV are presently widely recognized. Periodic CRV components isolated from short-term records in patients at rest are represented by high-frequency, low-frequency, and very low-frequency oscillations. Fourier-transform spectral analysis of cardiac rhythm is the most appropriate method of the detection of these oscillations. High-frequency components are associated with respiration and represent the effects of the parasympathetic nervous system on myocardium. Low-frequency components are due to the activity of the postganglionic sympathetic fibers and represent the processes of cardiac rhythm modulation by the sympathetic nervous system. Genesis of very low-frequency oscillations is still uncertain. Most probably, these oscillations are associated with the effects of suprasegmental (primarily, hypothalamic) centers of autonomic regulation. Aperiodic CRV components represent random events associated with the reflex regulation of the heart rate by external or internal factors. Because aperiodic components significantly modify the results of the CRV analysis, the effects of these factors should be eliminated. It is concluded that because many problems associated with cardiac rhythm variability remain to be solved, extensive research in this direction should be continued. Author Affiliation: (1) Medical Military Academy, St. Petersburg, Russia (2) St. Petersburg State University, St. Petersburg, Russia (3) State Research Institute of Applied Problems, St. Petersburg, Russia Article History: Registration Date: 12/10/2004

Byline: G. S. Dzhunusova (1), R. A. Kurmashev (1) Abstract: This article deals with changes in the EEG amplitudes and frequencies, spatial distribution of the main EEG rhythms, and structure of the interconnections between various zones of the hemispheric cortex in neurological patients before and after adaptive biocontrol sessions aimed at normalizing their state. The authors discuss the strategy and tactics of adaptive biocontrol with regard for the individual disorders of EEG parameters. Purposeful voluntary modification of the structure of interzonal relations leads to the rearrangement of intercentral connections and contributes to the cessation of pathological states neurological symptoms completely disappear in most of the patients. It is concluded that if the parameters of purposeful EEG regulation are selected properly, taking into account individual rearrangements, adaptive biocontrol may be used more widely in rehabilitation. Author Affiliation: (1) Institute of Highland Physiology and Experimental Pathology, National Academy of Sciences of the Kyrgyz Republic, Bishkek, Kyrgyzstan Article History: Registration Date: 12/10/2004

The purpose of this research was to review the topic of dengue fever transmission and investigate the relationship between seasonal temperature fluctuations and cyclical dengue fever incidence. Data from Puerto Rico (1988-1992) were used to test the model proposed. Dengue fever is a viral disease caused by any one of four antigenically distinct serotypes. It is transmitted by Aedes mosquitoes and infects 80 million people per year. Currently, dengue is endemic in specific tropical and subtropical regions worldwide and epidemic dengue has been reported in the Americas, Asia and some Pacific Islands. Data for Puerto Rico were collected from the NCDC/NOAA and a study conducted by Perez et al. (1994). Multivariate linear regression analysis was used to determine if a relationship exists between the monthly mean temperature lagged and the monthly incidence of dengue fever in Puerto Rico. Statistical significance was achieved and a second-order model produced an [R.sup.2] of 0.71. A residual analysis reveals positive autocorrelation, thus weakening the model's power to predict monthly dengue incidence. This suggests that other forces or factors related to the history of the herd immunity, the introduction of a new serotype, or demographic transitions are also influencing the cyclical transmission of dengue fever. Case clustering information, regional dengue distributions, and population density transformations must also be obtained in order to assess the forecasting ability of this model. Additional research is needed to avoid oversimplifying the problem. Without such attempts at establishing significant correlations, dengue prevention and control will remain a formidable task for many developing and developed countries. Keywords: Dengue fever; Regression analysis; Disease ecology; Puerto Rico

Byline: M. G. Vodolazhskaya (1) Keywords: conditioned reflex to time; anxious-phobic state Abstract: Improvements in the ability to count time endogenously with maturation in rats depends on the normal age dynamics of anxious-phobic state and is associated with the state of the peripheral compartment of the sympatheticoadrenal system. Increases in the lengths of locomotive excursions were accompanied by decreases in anxious-phobic state and increases in the quality of time-keeping. In rats aged three and six months (but not in one-month-old rats), the ability to count time endogenously showed a parabolic relationship with initial anxious-phobic state: the most precise and efficient counting of time intervals needs a certain intermediate level of anxiety, covering a relatively narrow range. Anxious-phobic states beyond this optimum, either increases or decreases, lead to degradation of chronometric ability. Author Affiliation: (1) Department of Physiology, Stavropol' State University, 1 Pushkin Street, 355009, Stavropol', Russia Article History: Registration Date: 08/10/2004

Byline: Yu. E. Moskalenko (1), V. Frymann (2), G. B. Weinstein (1), V. N. Semernya (1), T. I. Kravchenko (3), S. P. Markovets (1), A. A. Panov (1), N. F. Maiorova (1) Abstract: Slow rhythmic oscillations in the human cranial cavity were studied using two noninvasive methods: the bioimpedance method (volume ratios between liquid media in the cranial cavity) and transcranial ultrasound Doppler echography (variation in the blood flow in the middle cerebral artery). The combination of these methods made it possible to estimate the intracranial hemodynamics. Simultaneous recording of these parameters and their spectral analysis were carried out in healthy subjects and patients with intracranial hypertension syndrome and disturbed cerebrospinal fluid (CSF) flow. The parameters were recorded at rest and immediately after manual (osteopathic) correction. The recording and analysis were performed using a Macintosh-IIsi PC and the Chart-3.52, Cricket Graph-3.32, and Canvas-3.5 software. It was found that slow oscillations of the bioimpedance (BIM) in the frequency range 0.08--0.2 Hz were of intracranial origin and were related to the mechanisms of regulation of the blood supply to and oxygen consumption by cerebral tissue, as well as with the dynamics of the CSF circulation. Author Affiliation: (1) Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Morisa Toreza 44, St. Petersburg, 194223, Russia (2) California Center of Pediatric Osteopathic Medicine, San Diego, California, USA (3) Russian High School of Osteopathic Medicine, St. Petersburg, Russia Article History: Registration Date: 16/10/2004

Circadian rhythms and their molecular and genetic analysis in Neurospora are discussed with the thought that insights foreshadow similar things in the mammalian clock. More than a dozen regulated genes have been found. Work in Neurospora is at the forefront in studying clock control of gene expression. This organism is well suited to such study, being a malleable system. The means of analyzing rhythms are discussed. A short section on nonircadian rhythms in fungi is included.

Data illustrating the biological week and chronomes are presented in recognition of extensive work of G. Hildebrandt.