Infradian dynamics and variability of salivary testosterone in men and women

Background. The dynamics of testosterone levels exhibits several cyclic patterns with various period lengths. Circadian and circannual rhythms of testosterone are known in both genders. Among infradian rhythms only the circalunar cycle in women is widely accepted. In our previous studies we have found a circatrigintan (30 days) and a circavigintan (20 days) cycle in men. Whether cyclic patterns with higher frequencies are present in the dynamics of testosterone levels in men or in women is unknown.

Aim. To analyze the infradian dynamics of salivary testosterone in both genders for the presence of cyclic patterns.

Subjects and methods. Seventeen young and healthy women and 15 men were asked to collect saliva samples during 30 consecutive days. Testosterone levels were determined using radioimmunoassay, Analysis of Rhythmic Variance II (ANORVA II) was used for statistical analysis. Potential period lengths of 3 - 15 days were evaluated.

Results. The dynamics of salivary testosterone showed high intra-individual variability in both genders (coefficient of variation - 28% in women and 26% in men). ANORVA II analysis showed no significant rhythms, although a weak circaseptan cyclic pattern has been found in women.

Discussion. Our results showed no significant infradian cyclic variation with a period between 3 and 15 days. Further studies should concentrate on potential longer periods. Described intra-individual variability of testosterone levels in both genders should be considered in endocrine research.     

The biological rhythms of the hemostatic system in dogs

Temporal organization of the system of coagulative hemostasis was studied with the help of group and individual chronoanalysis examining the marks, characterising its basic functional blocks. The trustworthy ultra-, circa- and infradian rhythms of the components in two types of the intrasystemic organization were brought to light: the type during which the rhythms of all stages of the process were synphased and the type of time correlation during which the marks of the coagulative and post-coagulative stages of the process of coagulation were antiphased.     

月经周期不同阶段游离皮质醇昼夜节律的变化

为了研究皮质醇分泌的昼夜节律在月经周期中的变化,实验对15位月经周期正常的育龄期健康妇女,在月经周期的不同阶段分别于24h内每隔两小时采样,检测唾液昼夜游离皮质醇水平。采用非线性回归分析模型分析皮质醇昼夜节律。结果显示,皮质醇昼夜节律在整个月经周期都具有复杂的明显受到亚节律(ultradian)影响的分泌形式;与月经期相比,围排卵期和黄体晚期昼夜节律波峰宽度(peak-width)明显减低(P=0．005与0．031),而昼夜节律波谷(trough)有抬高趋势(P=0．0622与0．066);黄体晚期的亚节律波幅(ultradian amplitude)与月经期相比显著减低(P=0．002)而与围排卵期相比有减低趋势(P=0．05)。这些结果提示月经周期的不同阶段对皮质醇分泌的昼夜节律有影响。     

Physiology and regulation of biological rhythms in laboratory animals: an overview

Biological rhythms have been observed in practically all groups of laboratory mammals and at every level of physiological and behavioural organization. Biological rhythms are classified according to their period as ultradian (less than 24 h), circadian (approximately 24 h), infradian (greater than 24 h), and seasonal or circannual rhythms (approximately 1 year). This review outlines what is known about the neurobiology of biological rhythms in mammals and describes the hierarchical order in which ultradian, circadian and infradian rhythms are related to each other. The article does not attempt to catalogue every physiological variable showing rhythmical fluctuations in laboratory mammals. Rather, it focuses on the basic concepts of circadian rhythms and recent advances made in our understanding of the physiology of the internal clock controlling circadian and other biological rhythms.     

Role of the epiphysis in organization of the infradian rhythmicity of physiological systems

In 330 control and epiphysectomized rats divided into groups (each included 15 rats), we compared the dynamics of the following indices: temperature and mass of the body, daily volume of urine, activities of succinate and α-glycerophosphate dehydrogenases in lymphocytes, activity of peroxidase in blood neutrophils, and motor activity in the open field test. In control rats, a set of infradian rhythms was manifested, and their periods were about 26; 18; 13.5; 9; 7; and 3.5 days. In epiphysectomized rats the same set of the periods was observed, but the spectral density of and phase relations between the rhythms were considerably modified. We conclude that the role of the epiphysis in organization of the infradian rhythmicity of physiological processes is significant, but it plays a rhythm-organizing, but not a pacemaker, role. Epiphysectomy results in considerable desynchronization of the studied processes.     

External factors controlling annual testosterone and thyroxine cycles in the edible dormouse Glis glis

Annual patterns of hibernation, body weight, plasma testosterone and thyroxine were measured in two groups of edible dormice exposed to a constant photoperiod and to either environmental temperature (I), the four functions displayed annual cycles and the two hormonal cycles were parallel and restricted to the aroused state, while in group II only irregular infradian fluctuations were observed. However, a body temperature of 30 degrees C remained the critical lower limit enabling the start of the testosterone cycles for the two groups. Respective roles of endogenous and synchronizing mechanisms in controlling biological rhythms are discussed.     

Infradian rhythmics of markers of physiologic and metabolic processes in Wistar male rats

This work presents the results of the amplitude-phase structure of the physiological rhythms (locomotor activity) and steroid hormones production (common testosterone and cortisole) in gelded and intact Wistar male rats as well as rats exposed to an information load. The markers have been shown to depend on the social state of the animal. It was proved that there was a phase coincidence of the periods of the biological rhythms of common testosterone (intact rats), cortisole and locomotor activity for animals with different individualand typological features. It was shown that the oscillation period of infradian rhythms of the measured markers of physiologic and metabolic processes in the animals of all groups amounted to 4 days. It was found that infradian rhythms were not sensitive to factors of various genesis.     

Circatrigintan Cycle of Salivary Testosterone in Human Male

Background. Circadian and circannual cycles of testosterone (T) in men are known. The results of our previous study have shown indices for the existence of a male circalunar cycle of T similar to the female one. Objective. The purpose of this study was to investigate possible infradian rhythms of salivary T in young healthy men. Subjects & Methods. Saliva samples from 31 healthy men (18–25 years of age) were collected every second day (for 1 month) and every third day (during the following 1.5 months). T levels were determined by radioimmunoassay. Data were statistically analyzed for infradian rhythmic changes using two different methods: moving averages – zones of extremes, and analysis of rhythmic variance. Results. The data showed rhythmic variations with 2 different infradian periods. The differences between extreme values of the circatrigintan (period of 30 days) and circavigintan (period of 20 days) cycles were found to be highly significant (p < 1E-9; p < 1E-8). Conclusion. We believe that this is the first study demonstrating the existence of circatrigintan and circavigintan rhythms of testosterone in human males. Our findings might have implications in human physiology and pathophysiology.     

Children's diurnal cortisol activity during the first year of school

The present study examined 4- to 5-year-old British children's diurnal cortisol activity during their first year of school. The children's cortisol was measured before enrollment (baseline), upon enrollment, and both 3 and 6 months after enrollment. On each day, cortisol was sampled four times, providing information about the diurnal amount of cortisol secreted (AUC_G). Mixed-effect models were constructed to examine the way children's cortisol fluctuated over the course of the school year. Physiological activity was greater 3 months after enrollment, suggesting that some children reacted more to the challenge of school later than they did initially. Implications and suggestions for transitional practices and future research are discussed.     

Effect of geomagnetic activity on the rhythm of resistance of rats to hypoxia

The resistance of male Wistar rats to acute hypoxia was estimated from the lifetime at an "altitude" of 11.5 km above sea level from 13 to 21 p.m. and in different seasons of a year. Identical types of rhythms (circaseptan, circasemiseptan, infradian, circadian, and ultradian) of geomagnetic activity and lifetime were revealed. It was found that the periods of basal rhythms either coincide or are multiple. It was shown that the rhythms of geomagnetic activity (including nonbasal rhythms) affect lifetime rhythms (especially ultradian rhythms). As the periods of the rhythms decrease, the number of rhythms for both parameters increase (ultradian rhythms are most numerous), and relative differences in the values of periods (they are minimal for ultradian rhythms) and the amplitudes of rhythms decrease.     

Influence of cortisol on developmental rhythms during embryogenesis in a tropical damselfish

Newly-spawned teleost eggs can vary widely in their maternal endowment of a variety of hormones, including cortisol. Field and laboratory experiments have shown that initial egg cortisol concentrations directly influence the size at hatching of the benthic spawning damselfish, Pomacentrus amboinensis. The present study examines the mechanism by which cortisol influences larval size at hatching by investigating the growth and developmental rhythms throughout embryogenesis. Newly spawned eggs of P. amboinensis were collected from natural benthic nests, and half of each clutch was incubated in a moderate level of cortisol (2.7 x 10(-6) M, equivalent to a concentration of 0.79 pg/egg). Cortisol was found to have no affect on the rate of cell-pulsations up to epiboly (18 hr post-fertilization), with cells pulsing at a mean rate of 56-60 pulses/min. Cortisol had an affect on the relative growth rate from the start of gastrulation to knot formation. Growth in the cortisol-supplemented embryos was pulsed, with periods of fast growth punctuated by long periods of stasis. Overall growth rates during this period were lower in the cortisol-supplemented embryos despite their higher growth during active periods. Pulse rates of somite cells and contraction rhythms of myotomes and the heart were twice as high in cortisol-supplemented embryos than controls. Despite this, cortisol-supplemented eggs developed at the same rate as controls and hatched at the same time. This study suggests that the maternal endowment of cortisol to eggs plays a vital role in determining the embryonic rhythms by which embryos grow and may be directly influencing metabolism.     

Effects of barefoot habituation in winter on thermal and hormonal responses in young children--a preliminary study

This study investigated how socks-wearing habit or habitual barefoot in the cold winter affected skin temperatures of distal lower extremities, the urinary excretion of adrenaline, noradrenaline and cortsisol in young children. In Experiment I for preschool children, the measurements of foot and leg skin temperatures were conducted for 30 min in the classroom controlled at 23+/-2 degres C and 50+/-5%RH, and the excretion of urinary catecholamines and cortisol during nocturnal sleep were analyzed. In Experiment II for elementary school children, nocturnal secretion of urinary catecholamines and cortisol was analyzed. While leg skin temperature tended to be lower in barefoot group than in socks group during Experiment I, foot skin temperature was not significantly different between the two groups. Fall of leg skin temperature during 30 min measurement tended to be smaller in barefoot group than in socks group. Urine volume and urinary excretion of cortisol tended to be greater in barefoot group than in socks group for preschool children. Urinary noradrenaline was significantly greater and cortisol tended to be greater in barefoot group than in socks group for elementary school children. Considering that most of the findings shown above were in the proximity of the established level of statistical significance, it was provisionally concluded that young children with barefoot habituation might show more effective cold adaptation of metabolic type than those without the habituation do, by keeping their skin temperatures higher even in the cold and enhancing the metabolic rate.     

Circadian rhythms of salivary cortisol content during long-term space flight

Adaptation mechanisms of adrenal function related to secretion of cortisol were studied under conditions of microgravity. Parameters of diurnal rhythms of salivary cortisol were studied by Russian cosmonauts on board orbital station Mir during long-term space flights (SF). The preflight circadian rhythms of salivary cortisol in cosmonauts were characterized by the morning maximum occurring at 9∶43 a.m., the fluctuation amplitude 6.05 nmol/1, and the daily average concentration 8.79 nmol/l. The characteristics of cortisol diurnal rhythm changed under conditions of long-term space flight. On average, the rhythm measure and amplitude decreased after two months of flight. The postflight maximum concentration of free cortisol tended to occur later in the day. Evidently, the motor activity during SF, i.e., prophylactic exercises along with other factors, significantly influenced the parameters of cortisol circadian rhythm that was revealed by the individual variability of findings during the flight. After the long-term SF, individual ratios of salivary and plasma cortisol levels increased against the background of increased plasma content of the hormone, i.e., the fraction of free, physiologically active hormone in the total pool of circulating molecules decreased.     

Infradian rhythms of the esophageal epithelium mitotic activity, corticosterone and thyroxin level in Japanese quail Coturnix japonica

Everyday dynamics of corticosterone and thyroxin levels on blood serum, as well as esophageal epithelium proliferation activity in Japanese quail males, have been investigated over a period of 16 days. It was estimated that different individuals synchronically exhibited a 4-day rhythm of the corticosterone serum level. The thyroxin level displayed a 3-day biorhythm. The mitotic index in the esophageal epithelium negatively correlated with the corticosterone level. The revealed infradian rhythms of the corticosterone and thyroxin levels, as well as esophageal epithelium mitotic index, should be taken into account while carrying out experiments concerning the determination of the hormone level and mitotic activity of epithelial tissues.     

Factors Influencing Classroom Behavioral Engagement During the First Year at School

The present study examined child and school factors that might foster classroom behavioral engagement during the first year at school in a sample of 67 typically developing British 4-year-olds. The children were followed for 9 months from the summer before enrollment through the first 7 months of school. Our findings showed that effortful control and attachment security facilitated engagement, whereas impulsivity adversely affected engagement. The children's classroom engagement was further supported by close relationships with the teachers, but those who had more conflicts with the teachers or had developed avoidant feelings toward school tended to be more disengaged in the classroom. This study suggests that features of the child and environment collectively affect the early development of behavioral engagement at school, with some features possibly playing a more significant role at some than other phases during school transition. Limitations, implications, and suggestions for future research are discussed.     

Reproductive physiology of the clouded leopard: II. A circannual analysis of adrenal-pituitary-testicular relationships during electroejaculation or after an adrenocorticotropin hormone challenge

A circannual analysis was made of serum cortisol, luteinizing hormone (LH), and testosterone concentrations in the male clouded leopard (Neofelis nebulosa). Group I males (n = 4), maintained in a standardized environment, were bled serially during a regimented anesthesia/electroejaculation episode occurring monthly (beginning in January, ending in December). Additional sampling intervals were conducted under anesthesia only (control, n = 8), anesthesia plus a single adrenocorticotropin hormone challenge (ACTH, Cortrosyn, n = 4), or anesthesia plus a single 25 micrograms injection of gonadotropin-releasing hormone (GnRH, Gonadorelin, n = 4). Group II males (n = 6) from various zoological collections were sampled serially under the same semen collection conditions on one random occasion within the year. Serum cortisol levels were 2 times greater than values measured in comparable studies involving other felid species. Cortisol concentrations were similar during electroejaculation and control (anesthesia only) episodes, and mean levels did not rise as a result of semen collection. Adrenocorticotropin caused an immediate rise in cortisol to levels at least 1.5 times greater than electroejaculated or control counterparts. Mean concentrations of basal cortisol in individual males gradually increased as the year progressed, possibly as a consequence of repeated psychogenic stress. Between seasons, there were no differences in mean LH; however, testosterone levels were greater (p less than 0.05) in the winter compared to all other seasons. There were no differences (p greater than 0.05) between individual males in secretory patterns or mean concentrations of cortisol, LH, or testosterone. Within males, distinct temporal fluctuations were observed in both LH and testosterone during the approximately 80-min sampling interval. Neither LH nor testosterone profiles appeared affected by cortisol patterns during electroejaculation or after an ACTH challenge. A bolus of GnRH induced a marked rise in serum LH and testosterone within 15 and 30 min respectively, indicating that these two hormones were coupled. Both LH and testosterone profiles in Group II males mimicked those in Group I; concentrations of cortisol in Group II males immobilized on one occasion were similar to those of Group I animals sampled from January-May but appeared to be less than values measured from June-December. These data demonstrate that the clouded leopard, compared to other felids, produces markedly elevated concentrations of cortisol, which are likely related to an aggressive behavioral temperament.(ABSTRACT TRUNCATED AT 400 WORDS)     

Infradian rhythmicity in sleep/wake ratio in developing infants

Although there are several reports on ultradian and circadian rhythms in newborns, we found only one report in which infradian periodicities are described for heart-rate measurements in the early stages of human development. Here, we report infradian rhythms in the monthly range in the sleep/wake cycle of four infants studied along 24 consecutive weeks. Our procedure was applied to sleep diary records from four healthy newborns. The data were arranged in binary time series representing sleep (-1) or wake (1) states. These time series were integrated in order to obtain the cumulative sleep/wake time. A measure of the sleep/wake ratio (SWR) was obtained by computing the average slope of the cumulative sleep/wake time. To extract periodicities we applied the Fourier periodogram to the temporal course of the SWR. We found a notorious difference in the SWR pattern among infants. In two infants the SWR showed a marked linear decay, spending more time asleep than awake, while in the two other infants oscillated near zero. We found robust oscillations in all children. In all cases the Fourier periodogram results present significant power in the infradian range. From these results, we suggest that sleep and wake durations are probably modulated by some internal stimuli.     

The effects of low-dose 0.5-mg melatonin on the free-running circadian rhythms of blind subjects

Exogenous melatonin (0.5-10 mg) has been shown to entrain the free-running circadian rhythms of some blind subjects. The aim of this study was to assess further the entraining effects of a daily dose of 0.5 mg melatonin on the cortisol rhythm and its acute effects on subjective sleep in blind subjects with free-running 6-sulphatoxymelatonin (aMT6s) rhythms (circadian period [tau] 24.23-24.95 h). Ten subjects (9 males) were studied, aged 32 to 65 years, with no conscious light perception (NPL). In a placebo-controlled, single-blind design, subjects received 0.5 mg melatonin or placebo p.o. daily at 2100 h (treatment duration 26-81 days depending on individuals' circadian period). Subjective sleep was assessed from daily sleep and nap diaries. Urinary cortisol and aMT6s were assessed for 24 to 48 h weekly and measured by radioimmunoassay. Seven subjects exhibited an entrained or shortened cortisol period during melatonin treatment. Of these, 4 subjects entrained with a period indistinguishable from 24 h, 2 subjects continued to free run for up to 25 days during melatonin treatment before their cortisol rhythm became entrained, and 1 subject appeared to exhibit a shortened cortisol period throughout melatonin treatment. The subjects who entrained within 7 days did so when melatonin treatment commenced in the phase advance portion of the melatonin PRC (CT6-18). When melatonin treatment ceased, cortisol and aMT6s rhythms free ran at a similar period to before treatment. Three subjects failed to entrain with initial melatonin treatment commencing in the phase delay portion of the PRC. During melatonin treatment, there was a significant increase in nighttime sleep duration and a reduction in the number and duration of daytime naps. The positive effect of melatonin on sleep may be partly due to its acute soporific properties. The findings demonstrate that a daily dose of 0.5 mg melatonin is effective at entraining the free-running circadian systems in most of the blind subjects studied, and that circadian time (CT) of administration of melatonin may be important in determining whether a subject entrains to melatonin treatment. Optimal treatment with melatonin for this non-24-h sleep disorder should correct the underlying circadian disorder (to entrain the sleep-wake cycle) in addition to improving sleep acutely.     

Infradian Rhythmicity in Sleep/Wake Ratio in Developing Infants

Although there are several reports on ultradian and circadian rhythms in newborns, we found only one report in which infradian periodicities are described for heart-rate measurements in the early stages of human development. Here, we report infradian rhythms in the monthly range in the sleep/wake cycle of four infants studied along 24 consecutive weeks. Our procedure was applied to sleep diary records from four healthy newborns. The data were arranged in binary time series representing sleep (?1) or wake (1) states. These time series were integrated in order to obtain the cumulative sleep/wake time. A measure of the sleep/wake ratio (SWR) was obtained by computing the average slope of the cumulative sleep/wake time. To extract periodicities we applied the Fourier periodogram to the temporal course of the SWR. We found a notorious difference in the SWR pattern among infants. In two infants the SWR showed a marked linear decay, spending more time asleep than awake, while in the two other infants oscillated near zero. We found robust oscillations in all children. In all cases the Fourier periodogram results present significant power in the infradian range. From these results, we suggest that sleep and wake durations are probably modulated by some internal stimuli.     

The effect of cyproterone acetate alone and in combination with ethinylestradiol on the hypothalamic pituitary adrenal axis, prolactin and growth hormone release in male-to-female transsexuals

This study investigated the effects of long-term cyproterone-acetate (CA) treatment on the hypothalamus-pituitary-adrenal axis and further on the release of prolactin and growth hormone. Thirty-one male-to-female transsexuals, treated at least 3 months either with 100 mg CA alone or in combination with 50 micrograms ethinyloestradiol (EO)/day, were studied. In all of them the cortisol response to 250 micrograms Synacthen administration was comparable to that measured in controls. Six subjects treated with CA alone (group I) and six subjects treated with CA + EO (group II) underwent an insulin-hypoglycemia test. Seven eugonadal men served as controls. Compared with control values: in two subjects of group I and one subject of group II a low cortisol response was found. The mean growth hormone response was found to be lower in both groups, whereas the mean prolactin response was lower in group I.