Ontogeny of the Locomotor Activity Rhythm in the Common Marmoset (Callithrix jacchus)

The ontogeny of locomotor activity rhythm in the common marmoset was studied in three animals, observed during infant and juvenile stages, and in adult age. Animals were kept with their families in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed in the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. Animal 3 was observed continuously one day a week in order to detect less than 2 h period harmonic components. Animals' weekly data series were analyzed by Fourier analysis and Siegel's test to detect significant harmonic components. Results showed a main 24 h period com ponent for all records and a secondary 8 h period component in at least 34% of animal's week data series. The power content of the 24 h component showed an increase with age, reaching some stability near the 16th week of life suggesting that this component is mature at the end of the animal's infant stage. However, for the 8 h component an oscillating pattern was observed following the environmental annual temperature cycle; this may indicate a seasonal modulation of daily locomotor activity profiles.     

Annual Variation in an Ultradian Component in the Locomotor Activity Rhythm of the Common Marmoset (Callithrix jacchus)

Daily locomotor activity in common marmosets shows a decrease near the middle of the active phase, as observed for captive and wild living animals. An important 8 h period component detected in spectral analysis shows annual variation. To determine the environmental factors that are correlated with this finding, three animals were observed during infant and juvenile stages in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed inside the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. From the Fourier analysis of weekly data series we calculated the relative power of the 8 h period component. Pearson's correlation test showed that the relative power correlates better with environmental temperature and photophase duration than with relative humidity or rainfall. Amplitude but not acrophase showed significant differences (Kruskall-Wallis test, p <0.01) between seasons. These findings suggest that the annual variation in the 8 h period component could result from a temperature modulation on the locomotor activity rhythm.     

Modeling the circadian variability of ambulatorily monitored blood pressure by multiple-component analysis

The use of a set of new end points derived from ambulatory blood pressure monitoring (ABPM), in addition to the blood pressure (BP) values themselves, has been advocated to improve the sensitivity and specificity in diagnosing hypertension and to evaluate a person's response to treatment. An adequate estimation of rhythmic parameters depends, however, on the ability to describe properly the circadian pattern of BP variability. The purpose of this study was to identify a simple model that could characterize sufficiently well the circadian pattern of BP in normotensive healthy volunteers sampled by ambulatory monitoring. We studied 278 clinically healthy Spanish adults (184 men), 22.7±3.3 yr of age, without medical history of hypertension and mean BP from ambulatory profiles always below 135/85 mmHg for systolic/diastolic BP, who underwent sequential ABPM providing a total of 1115 series of BPs and heart rates (HRs), sampled on each occasion at 0.5h intervals for 48 h. Subjects were assessed while adhering to their usual diurnal activity and nocturnal sleep routine, without restrictions but avoiding the use of medication. The circadian rhythm in BP and HR for each subject was established by multiple-component analysis. A statistically significant 24h component is documented for 97% of the BP profiles, with a significant second (12h) harmonic documented in 65% of the profiles. Other ultradian harmonic components were significant in less than 20% of the profiles. A statistically significant increase in the coefficient of determination (percent of overall variability explained by the function fitted to the data) was only obtained after including the periods of 24 and 12 h for BP, and periods of 24, 12, and 6 h for HR in the model components. Although other ultradian components can be demonstrated as statistically significant in a small percent of subjects, a rather simple model including only the two first harmonics of the 24h period describes sufficiently well, at the specified sampling rate, the circadian pattern of BP in normotensive subjects. Departure from this model could characterize overt pathology, as recently demonstrated in the diagnosis of preeclampsia.     

Modeling the circadian variability of ambulatorily monitored blood pressure by multiple-component analysis

The use of a set of new end points derived from ambulatory blood pressure monitoring (ABPM), in addition to the blood pressure (BP) values themselves, has been advocated to improve the sensitivity and specificity in diagnosing hypertension and to evaluate a person's response to treatment. An adequate estimation of rhythmic parameters depends, however, on the ability to describe properly the circadian pattern of BP variability. The purpose of this study was to identify a simple model that could characterize sufficiently well the circadian pattern of BP in normotensive healthy volunteers sampled by ambulatory monitoring. We studied 278 clinically healthy Spanish adults (184 men), 22.7±3.3 yr of age, without medical history of hypertension and mean BP from ambulatory profiles always below 135/85 mmHg for systolic/diastolic BP, who underwent sequential ABPM providing a total of 1115 series of BPs and heart rates (HRs), sampled on each occasion at 0.5h intervals for 48 h. Subjects were assessed while adhering to their usual diurnal activity and nocturnal sleep routine, without restrictions but avoiding the use of medication. The circadian rhythm in BP and HR for each subject was established by multiple-component analysis. A statistically significant 24h component is documented for 97% of the BP profiles, with a significant second (12h) harmonic documented in 65% of the profiles. Other ultradian harmonic components were significant in less than 20% of the profiles. A statistically significant increase in the coefficient of determination (percent of overall variability explained by the function fitted to the data) was only obtained after including the periods of 24 and 12 h for BP, and periods of 24, 12, and 6 h for HR in the model components. Although other ultradian components can be demonstrated as statistically significant in a small percent of subjects, a rather simple model including only the two first harmonics of the 24h period describes sufficiently well, at the specified sampling rate, the circadian pattern of BP in normotensive subjects. Departure from this model could characterize overt pathology, as recently demonstrated in the diagnosis of preeclampsia.     

Locomotor performance of sand lizards (Lacerta agilis): effects of predatory pressure and parasite load

Locomotor performance affects foraging efficiency, predator avoidance and consequently fitness. Agility and speed determine the animal's social status and reflect its condition. In this study, we test how predatory pressure and parasite load influences locomotor performance of wild specimens of the sand lizard Lacerta agilis. Animals were chased on a 2-metre racetrack. Lizards with autotomy ran significantly faster than lizards with an intact tail, but there was no significant difference in running speed between individuals with fresh caudal autotomy and regenerated tails. Parasite presence and load, age and sex had no significant effect on speed. Our results indicate that autotomy either alters locomotory behaviour or that individuals with autotomised tails were those that previously survived contact with predators, and therefore represented a subgroup of the fastest individuals. Therefore, in general, predatory pressure but not parasites affected locomotor performance in lizards.     

Play behaviour in group-housed dairy calves, the effect of space allowance

In dairy calves kept in pens, lack of sufficient space may inhibit the performance of play behaviour. The present study investigated, firstly, if an increase in space allowance increases the occurrence of play behaviour, and secondly, if calves kept at a low space allowance perform more locomotor play when released individually in a large novel area. A total of 96 dairy calves in six repetitions were housed in groups of four, in pens of either 4, 3, 2.2 or 1.5 m(2) per calf from 2 weeks of age. The occurrence of play behaviour in the home environment was recorded continuously for each individual calf during 24 h at 5, 7 and 9 weeks of age. Locomotor play decreased over the weeks (54, 29 and 19 s for weeks 5, 7 and 9, respectively; F(2,40)=17.98; P<0.001), and the interaction between space allowance and week tended to be significant (F(6,40)=1.96; P<0.10). At 5 weeks of age, calves kept at 4 or 3 m(2) per calf performed more locomotor play in the home environment than calves at 2.2 or 1.5 m(2) per calf (68, 74, 38 and 39 s for 4, 3, 2.2 and 1.5 m(2) per calf, respectively; F(3,15)=3.40; P<0.05), but in weeks 7 and 9, no effects of space allowance were found. In addition, the duration of locomotor play was recorded for all calves during an individual 10-min open-field test in a 9.6x4.8 m arena at 4 and 10 weeks of age. During the open-field test at 10 weeks of age, calves from pens with 1.5 m(2) per calf performed more locomotor play than calves on the remaining treatments (10, 9, 12 and 25 s for 4, 3, 2.2 and 1.5 m(2) per calf, respectively; F(3,15)=4.05; P<0.05). The present study shows that an increase in the available space increases the occurrence of locomotor play in the home environment at 5 weeks of age. It also shows that calves kept in pens with the smallest space allowance performed more locomotor play behaviour when released in a large arena at 10 weeks of age.     

Variability in the Period of the Blood Pressure Orcadian Rhythm in Human Beings

In studies and assessments of human beings done in natural settings, it is assumed that the period τ of circadian rhythms, including ones of systolic (SBP) and diastolic (DBP) blood pressure, is equal to 24 hours. To test this hypothesis, SBP and DBP rhythms were studied in 112 medication-free, non-hospitalized subjects (62 males, 47.1 + 2.0 years [χ ± SEM], and 50 females, 54.5 ± 2.1 years) by 48h ambulatory blood pressure monitoring (ABPM). Of these, 26 were hypertensive (diurnal SBP> 140 mmHg and diurnal DBP> 90 mmHg) and 86 normotensive. All subjects were synchronized by their habitual daytime activities from ?08:00h to ?23:00h ± lh and by sleep at night. The BP was assessed at 15-minute intervals during a continuous 48h span using a Spacelabs model #90207 ABPM. The time series data of each subject were individually evaluated by power spectra analysis for the prominent x of the SBP and DBP rhythms. The prominent X differed from 24 hours in 22/112 subjects for SBP and in 16/112 subjects for DBP. Generally, in these individuals the τ was less than 24 hours. The occurrence of non-24h τ's was more frequent in hypertensive than normotensive subjects; the difference between the groups in the distribution of the prominent τ's by class (τ = 24h, >=12, 12h<24h, etc.) was statistically significant (χ² test =19.1; p < 0.001). No difference in the distribution of x's of blood pressure was detected according to the subject's age and gender. These findings suggest that ABPM done only for a duration of 24h may be too short to characterize accurately the features of the day-night variation in human BP, including the precise period of its rhythm. (Chronobiology International, 14(3), 307–317, 1997)     

Neural pathways involved in mutual interactions between optic lobe circadian pacemakers in the cricketGryllus bimaculatus

The circadian locomotor rhythm of the cricketGryllus bimaculatus is primarily generated by a pair of optic lobe circadian pacemakers. The two pacemakers mutually interact to keep a stable temporal structure in the locomotor activity. The interaction has two principal effects on the activity rhythm, i.e., phase-dependent modulation of the freerunning period and phase-dependent suppression of activity driven by the partner pacemaker. Both effects were mediated by neural pathways, since they were immediately abolished after the optic stalk connecting the optic medulla to the lobula was unilaterally severed. The neural pathways were examined by recording locomotor activity, under a 13 h light to 13 h dark cycle, after the optic nerves were unilaterally severed and the contralateral optic stalk was partially destroyed near the lobula. When the dorsal half of the optic stalk was severed, locomotor rhythm mostly split into two components: one was readily entrained to the given light-dark cycle and the other freeran with a marked fluctuation in freerunning period, where the period of the freerunning component was lengthened or shortened when the onset of the entrained component occurred during its subjective night or day, respectively. The phase-dependent modulation of activity was also observed in both components. However, severance of the ventral half of the optic stalk resulted in appearance only of the freerunning component; neither the phase-dependent modulation of its freerunning period nor the change in activity level was observed. These results suggest that neurons driving the mutual interaction and the overt activity rhythm run in the ventral half of the proximal optic stalk that includes axons of large medulla neurons projecting to the cerebral lobe and the contralateral medulla.Abbreviations LD light dark cycle - freerunning period     

Different behavior of body temperature and total locomotor activity daily rhythms during light/dark cycle in stabled Oryctolagus cuniculus

In order to investigate the potential causal link between the rhythm of activity and body temperature, we simultaneously recorded rectal temperature and total locomotor activity in five clinically healthy female rabbits (blue Vienna breed), 12 week old and mean body weight 2.7 ± 0.3. Animals were housed in individual cages (90?×?50?×?35 cm) under natural 12/12 light/dark cycle. Total locomotor activity was monitored for 15 days by an activity data logger. On day 1, 5, 10, and 15 rectal temperature was recorded every 2 h for a 24-h period. Application of single cosinor method showed a nocturnal daily rhythm of rectal temperature with a range of oscillation of about 1 °C, acrophase after dusk and low robustness value. The daily rhythm of locomotor activity showed its acrophase in the middle of the scotophase and a high robustness value. This information improves the knowledge available on the circadian biology of rabbits useful in the evaluation of physiology of this species.     

Circadian Rhythms and time Measurement in Locomotor Activity of the Scorpion Leiurus Quinquestriatus (Buthidae)

The circadian rhythms of locomotor activity of the scorpion Leiurus quinqueslriatus were examined under different light-dark cycles and in free-running conditions. The circadian rhythm is bimodal in LD 12:12 with alternating cycles of temperature (35°-25°C) with high intensity (1300 lux) or in LD 12: 12 with constant temperature 35° C with 300 lux. In LD 12:12 (1300 lux), in long or in short light spans with constant temperature, the bimodal pattern is slightly changed with the appearance of a third minor peak of activity. In free-running conditions, the bimodal rhythm of locomotor activity persists in DD with T about 24 hr, but in LL the rhythm becomes unimodal with T about 24 hr. Cosinor and power spectrum analysis showed the presence of more than one periodic component. It seems that there is a correlation between the range of light regimens, temperature, light intensity and the coincidence of these components. These components are independently entrained by the environmental light cycle. The mechanism of entrainment of components is discussed.     

Action anticipation in human infants reveals assumptions about anteroposterior body-structure and action

Animal actions are almost universally constrained by the bilateral body-plan. For example, the direction of travel tends to be constrained by the orientation of the animal''s anteroposterior axis. Hence, an animal''s behaviour can reliably guide the identification of its front and back, and its orientation can reliably guide action prediction. We examine the hypothesis that the evolutionarily ancient relation between anteroposterior body-structure and behaviour guides our cognitive processing of agents and their actions. In a series of studies, we demonstrate that, after limited exposure, human infants as young as six months of age spontaneously encode a novel agent as having a certain axial direction with respect to its actions and rely on it when anticipating the agent''s further behaviour. We found that such encoding is restricted to objects exhibiting cues of agency and does not depend on generalization from features of familiar animals. Our research offers a new tool for investigating the perception of animate agency and supports the proposal that the underlying cognitive mechanisms have been shaped by basic biological adaptations in humans.     

Growth of the maxillary complex in the rhesus monkey (Macaca mulatta)

The growth of the maxillary complex of 36 rhesus monkeys (Macaca mulatta) was analyzed quantitatively and qualitatively during four defined stages of postnatal development (i.e., infant, juvenile, adolescent, young adult). At each stage, growth was observed during a 24 week period. Since some animals were observed during two successive stages of development, 47 periods of growth were studied. The incremental growth data were collected by superimposing serial cephalograms on cranial base implants and on maxillary implants. The largest increments of growth were observed in the infant animals and were successively less during the other periods studied. The horizontal growth component was more prominent than the vertical component in all age groups. The contribution of sutural growth to the vertical displacement of the maxilla was greater posteriorly, leading to a rotation of the maxillary complex during growth. The occlusal relationship was maintained by selective bone remodeling in conjunction with dentitional migration.     

QUANTITATIVE AND QUALITATIVE CHANGES IN RIBONUCLEIC ACIDS OF RAT BRAIN DEPENDENT ON AGE AND TRAINING EXPERIMENTS

—Investigations of rat brain RNA were carried out by phenol extraction of the whole brain and chromatographic fractionation into ribosomal RNA and transfer RNA. (1) The amounts of both RNA species increase in the course of the animal's development reaching a maximum at about the tenth week of life. The ratio of both species remains constant throughout the growth to the twentieth week. After the rats had been trained how to reach their forage by balancing on a stressed rope, the rRNA content was found to be significantly higher, whereas the tRNA content was unchanged. (2) The portion of ribosomes bound in polysome complexes decreases with increasing age of rats. Conditioning of the animals brings about again an increase in polysome content. It is supposed that this reflects an enhanced synthesis of specific proteins in young developing rats and in the course of conditioning. (3) In young rats a second valine specific tRNA could be found as a minor component in addition to the major valyl-tRNA. This additional component disappears as the animals advance to an age of 3 weeks and it could not be detected in the brains of rats after training experiments. In tRNAs specific for the amino acids leucine, lysine and phenylalanine no kind of deviation could be stated.     

Child Mortality Estimation: Estimating Sex Differences in Childhood Mortality since the 1970s

Introduction

Producing estimates of infant (under age 1 y), child (age 1–4 y), and under-five (under age 5 y) mortality rates disaggregated by sex is complicated by problems with data quality and availability. Interpretation of sex differences requires nuanced analysis: girls have a biological advantage against many causes of death that may be eroded if they are disadvantaged in access to resources. Earlier studies found that girls in some regions were not experiencing the survival advantage expected at given levels of mortality. In this paper I generate new estimates of sex differences for the 1970s to the 2000s.

Methods and Findings

Simple fitting methods were applied to male-to-female ratios of infant and under-five mortality rates from vital registration, surveys, and censuses. The sex ratio estimates were used to disaggregate published series of both-sexes mortality rates that were based on a larger number of sources. In many developing countries, I found that sex ratios of mortality have changed in the same direction as historically occurred in developed countries, but typically had a lower degree of female advantage for a given level of mortality. Regional average sex ratios weighted by numbers of births were found to be highly influenced by China and India, the only countries where both infant mortality and overall under-five mortality were estimated to be higher for girls than for boys in the 2000s. For the less developed regions (comprising Africa, Asia excluding Japan, Latin America/Caribbean, and Oceania excluding Australia and New Zealand), on average, boys'' under-five mortality in the 2000s was about 2% higher than girls''. A number of countries were found to still experience higher mortality for girls than boys in the 1–4-y age group, with concentrations in southern Asia, northern Africa/western Asia, and western Africa. In the more developed regions (comprising Europe, northern America, Japan, Australia, and New Zealand), I found that the sex ratio of infant mortality peaked in the 1970s or 1980s and declined thereafter.

Conclusions

The methods developed here pinpoint regions and countries where sex differences in mortality merit closer examination to ensure that both sexes are sharing equally in access to health resources. Further study of the distribution of causes of death in different settings will aid the interpretation of differences in survival for boys and girls. Please see later in the article for the Editors'' Summary.     

Analysis of coupling between optic lobe circadian pacemakers in the cricket Gryllus bimaculatus

The coupling mechanism between weakly coupled two optic lobe circadian pacemakers in the cricket Gryllus bimaculatus was investigated by recording the locomotor activity, under light-dark cycles with various lengths, after the optic nerve was unilaterally severed. The activity rhythm split into two components under the light cycles different from 24 h: one was readily entrained to the light cycle and the other only loosely entrained or freeran. Additional removal of the optic lobe on the intact side resulted in a loss of the entrained component and that on the blinded side caused the reverse effect, indicating that the entrained component was driven by the pacemaker on the intact side and the other by the one on the blinded side. The synchronization between the two components was achieved only in light cycles with a limited length between 23 and 25 h. Without this range, the desynchronization of the components occurred. In the split rhythm, the phase-dependent modulation of the period of freerunning component and the mutual suppression of locomotor activity during the subjective day phase were clearly observed. The suppression was also evident in the lights-on peak that was the masking effect of light. The light cycle with dim light significantly reduced the ratio of animals with the pacemaker coupling as well as the magnitude of the period modulation. These results suggest (1) that the mutual coupling is achieved only when the difference in the periods between the two pacemakers is within an allowable range, (2) that the photic information is also involved in the mechanism of mutual coupling, and (3) that the suppression of activity occurs at the regulatory center for locomotion.Abbreviations CT circadian time - DD constant darkness - LL constant light - LD light to dark cycle - T length of light to dark cycle - freerunning period     

The secret world of shrimps: polarisation vision at its best

Background

Animal vision spans a great range of complexity, with systems evolving to detect variations in light intensity, distribution, colour, and polarisation. Polarisation vision systems studied to date detect one to four channels of linear polarisation, combining them in opponent pairs to provide intensity-independent operation. Circular polarisation vision has never been seen, and is widely believed to play no part in animal vision.

Methodology/Principal Findings

Polarisation is fully measured via Stokes'' parameters—obtained by combined linear and circular polarisation measurements. Optimal polarisation vision is the ability to see Stokes'' parameters: here we show that the crustacean Gonodactylus smithii measures the exact components required.

Conclusions/Significance

This vision provides optimal contrast-enhancement and precise determination of polarisation with no confusion states or neutral points—significant advantages. Linear and circular polarisation each give partial information about the polarisation of light—but the combination of the two, as we will show here, results in optimal polarisation vision. We suggest that linear and circular polarisation vision not be regarded as different modalities, since both are necessary for optimal polarisation vision; their combination renders polarisation vision independent of strongly linearly or circularly polarised features in the animal''s environment.     

Photoperiod influences endogenous rhythm of ambient temperature selection by the honeybee Apis mellifera

The aim of this study was to evaluate whether the day–night cycle phase is a critical factor modulating diurnal rhythm of isolated honeybee's thermal preference or other factors are involved. The insects were exposed to standard (LD 12:12) and reversed (DL 12:12) photoperiods as well as to constant light and constant darkness conditions. Thermal preference and motor activity of honeybees were recorded for 3–5 days in a thermal gradient system. Under the standard (control) photoperiod conditions mean values of temperature selected by honeybees changed rhythmically within the period of about 24 h. Honeybees, exposed to the modified light–darkness cycle distinctly modified their rhythm of thermal preference. Under the reversed photoperiod conditions period of selected ambient temperature was much longer than before, until a complete reversal of the circadian oscillation was established at the end of the experiment. Experiments performed under constant light and constant darkness yielded undisturbed 24 h rhythms of both ambient temperature selection and locomotor activity. Under these conditions only a slight, nonsignificant flattening of the temperature selection curves was noticed. Both lack of substantial changes in the amplitude and occurring phase shifts of the rhythm, recorded in our experiments suggest its endogenous character. Our results prove that diurnal rhythm of ambient temperature selection by bee workers may be entrained by light–dark cycles. This implies a critical role of photoperiod in the modulation of nychthemeral oscillations of thermal preference in honeybees.     

Mandibular growth in the rhesus monkey (Macaca mulatta)

Mandibular growth of 42 rhesus monkeys (Macaca mulatta) was analyzed quantitatively and qualitatively. Four groups of animals were defined according to dentitional age (i.e., infant, juvenile, adolescent, young adult). At each age growth was observed for a 24 week period. Since some animals were observed at more than one stage of development, 57 periods of growth were studied. The growth incremental data were collected by superimposing serial cephalograms on mandibular implants. Growth and remodeling of both the skeletal and dento-alveolar components of the rhesus mandible were greatest in the infant monkeys and were less in successive age groups. Posterior relocation of the ramus was noted in all age groups while bone deposition on the anterior and inferior borders of the mandibular body was greatest in the younger animals. The most pronounced dental changes also occurred in the younger animals while the dentitions of the adolescent and adult animals were generally more stable. This study demonstrates that the rate and direction of normal mandibular growth varies with the age of the animal. Furthermore, mandibular growth is quantified at four defined maturational levels to provide a set of values illustrating normal mandibular growth. These values can also be used as control data for experimental studies.     

Infant development in two aquarium bottlenose dolphins

The behavioral development of two aquarium bottlenose dolphin calves, one male (born to a primiparous mother) and one female (born to a multiparous mother), was examined. From birth to 9 weeks of age, a total of 558.7 h of nursing and behavioral data were collected using focal sampling methods. Data from both calves revealed a pattern of increasing independence as they aged, but there were significant differences between the two calves. Suckling rates, mean suckles per bout, suckling bout rates, and bout durations for the male calf were higher than those for the female calf throughout the study. These frequencies declined significantly over time in the male's case but not in the female's case. Her suckling durations (lock-on time) were longer than his. The male spent more time in infant position (under the mother) than the female calf and less time swimming in echelon position (alongside the mother). Over time, the male spent less time in infant position, and the female calf spent more time socializing and less time echelon swimming. Both calves decreased the amount of time spent close to their mothers over the 9 week period, and the mothers decreased their role in proximity maintenance over time. We suggest that factors related to maternal primiparity caused the male calf to develop an effective compensatory response of frequent nursing and spending more time in infant position. Both calves survived and were healthy at the end of the observation period. © 1995 Wiley-Liss, Inc.