Influence of pregnancy and lactation on diurnal and seasonal changes in lactic acid and pyruvic acid levels and in values of pH, pCO2 and pO2 in the mare blood.

1. The diurnal changes in the levels of lactic (LA) and pyruvic (PA) acids and in values of pH, pO2 and pCO2 were studied in the blood of barren and later on in pregnant and lactating mares, throughout three subsequent years. 2. Blood samples were taken every 4 hr, for one day, each month, throughout 3 years. 3. The mares were kept and fed in the same conditions, lighting was natural. 4. In barren mares, diurnal rhythm in LA, PA, pO2 and pCO2 was found. 5. The pregnancy as well as lactation masked diurnal rhythms in parameters studied, except the LA level during lactation but then the acrophase was shifted by 3-4 hr. 6. Seasonal cyclicity was found in the values of LA, PA and pCO2 in barren mares. The pregnancy abolished cyclicity in LA level and modified the behaviour of PA and pCO2 values causing a shift of acrophases and lowering the amplitudes of the indices. 7. In the pO2 tensions no seasonal cycles were observed. 8. In the values of pH neither diurnal rhythms nor seasonal cycles throughout study years were observed.     

Development of diurnal rhythm in some metabolic parameters in foals

1. The development of diurnal rhythm activity of FDPA, AspAT and A1AT and in levels of cortisol, T3 and T4 was observed in the blood serum of six foals. 2. The studies began when a foal was 7 days old and were repeated every month until foals reached 1 year of age. Blood samples were taken every 4 hr for one day each month. 3. As a control group four barren mares were used, kept and examined in the same conditions. 4. In mature mares, diurnal rhythms in activity of A1AT (acrophase at 2200 hr), AspAt (2400 hr) and cortisol (0630 hr) but in T3 only in summer months (acrophase at 0100 hr) were observed. 5. During the first 6 months of foal life, significantly higher mean levels of FDPA, A1AT, T3 and T4 than in control mares were found. 6. The cortisol level in foals was half as much as that of mature mares throughout the year. 7. In foals the diurnal rhythm in A1AT activity occurred in the 5th month and in AspAt--in the 12th month (acrophase at 2400 hr), but in cortisol levels it was developed already in the second month of foal life (acrophase at 0830 hr).     

Influence of pregnancy on diurnal and seasonal changes in glucose level and activity of FDPA, AlAT and AspAT in mares.

1. The diurnal changes in the glucose level and in activity of FDPA, A1AT and AspAT in four pregnant standard-bred mares were studied. 2. As a control four barren mares, were kept and examined in the same conditions. 3. Blood samples were taken every 4 hr for one day, each month, throughout pregnancy, or one year. 4. A diurnal rhythm in activity of A1AT and AspAT in barren mares was found. The pregnancy masked diurnal rhythm in activities of both transaminases. 5. No diurnal rhythm in glucose level and FDPA activity in both groups of mares was observed. 6. Seasonal cyclicity was found in all indices studied, in both groups of mares. 7. The pregnancy did not abolish cyclicity in parameters studied but modified their behaviour--causing a shift of acrophases (glucose, FDPA, AspAT) and lowering the amplitudes (FDPA, A1AT, AspAT).     

Seasonal changes in blood serum protein fractions and in activity of AspAT and AlAT in Arabian brood mares and their foals

In 34 pure breed Arabian horses divided into four groups (Gr. I--10 pregnant mares, Gr. II--7 barren mares, Gr. III--10 foals born in 1981, Gr. IV--7 foals born in 1982) seasonal changes in total blood serum protein, its electrophoretic fractions and the activity of AspAT and AlAT were studied. Seasonal cyclicity was found in all groups in the amount of total serum proteins, and alpha 2- and beta 1-globulin fractions. Cyclicity was found in the level of albumin and activity of AspAT in three groups, not Gr. II, and in gamma-globulin, not Gr. IV. beta 2-globulin and AlAT cyclicity was found in two groups and alpha 1-globulin cyclicity was found only in Gr. II. Out of nine indices studied, cyclicity was found in eight of them in pregnant mares, Gr. I; in seven in older foals, Gr. III; in six in the young foals, Gr. IV; and in five in barren mares, Gr. II.     

Seasonal changes in the red blood cell indices in Arabian brood mares and their foals

In 34 pure-bred Arabian horses, divided into four groups (Gr. I, 10 pregnant mares; Gr. II, seven barren mares; Gr. III, 10 foals born in 1981; Gr. IV, seven foals born in 1982), seasonal changes in haemoglobin level, haematocrit value, sedimentation rate, red blood cell number and diameter, percentage of erythroblasts and reticulocytes, and index F were studied. Seasonal cyclicity was found in all groups in the haemoglobin level, haematocrit value and RBC diameter. It was also found in the sedimentation rate (PCV) and in index F, but not for the youngest foals (Gr. IV). For the RBC number the cyclicity is given in both groups of foals, and the erythroblast and reticulocyte percentage only in the older foals (Gr. III). Out of eight indices studied cyclicity was found in all foals in Gr. III, in five of the mares in Groups I and II, and in four of the youngest foals in Gr. IV. There is no difference in the cyclicity of indices studied between pregnant and barren mares.     

Circadian and seasonal changes of the inducer:suppressor ratio (OKT4+:OKT8+) in venous blood of healthy adults

Circadian and seasonal variations in the T helper: T suppressor-cytotoxic ratio were investigated in peripheral blood from five healthy young men. Mononuclear cells were isolated on Ficoll-Paque gradient, then incubated with OKT4 and OKT8 monoclonal antibodies. Plasma cortisol was determined in four of these seven time series. Large interindividual differences were documented and statistically validated for the 24-hr.-means of total lymphocytes, OKT4+:OKT8+ ratio, and of plasma cortisol (both total and free). For a pooled data, a circadian rhythm was demonstrated by cosinor (p less than 0.001) for total lymphocytes (acrophase at 1.00 hr.), total plasma cortisol (acrophase at 10.30 hrs.) and free plasma cortisol (acrophase at 9.50 hrs.), but not for OKT4+:OKT8+ ratio. This index however exhibited a statistically significant circadian rhythm in April and August, but not in November. Its double-amplitude exceeded 80% of the 24-hour-mean and its acrophase was localized at 6.40 hrs. in April and at 22.30 hrs. in August. Its 24-hr-mean was higher in August as compared to April and November. The circadian rhythm in the OKT4+:OKT8+ ratio did not seem to be related to that of plasma cortisol. Both circadian and seasonal variations need to be taken into account when investigating the regulations of immune variables such as T helper: T suppressor-cytotoxic ratio.     

A study of diurnal changes in cortisol and glucose levels and FDPA activity in foals during the first 13 weeks of life and in their lactating mothers

1. In six standard-bred mares and their foals diurnal changes in the cortisol and glucose levels and in FDPA activity were studies for 13 weeks of foal life. 2. In the cortisol level diurnal rhythm was found in the 3rd, 7th and 11th week of foal life and in the 11th week of lactation in mares. 3. In mares the mean diurnal cortisol level changed from 32 ng/ml in the first week to 57 in the 11th week and in foals from 24 in the first week to 16 ng/ml in the 11th week. 4. In the glucose level no diurnal rhythm was observed. 5. In mares the mean diurnal glucose level after parturition was about 58 mg/100 ml and increased to 83-85 mg/100 ml. In foals it changed from 105 to 128 mg/100 ml. 6. In the activity of FDPA no diurnal rhythm was observed. 7. The mean activity of FDPA changed in mares from 3.3 to 4.4 U and in foals from 5.7 to 7.5 U.     

Seasonal changes in the white blood cell system, lyzozyme activity and cortisol level in Arabian brood mares and their foals

In 34 pure-breed Arabian horses divided into four groups (Gr. I, ten pregnant mares; Gr. II, seven barren mares; Gr. III, ten foals born in 1981; Gr. IV, seven foals born in 1982) seasonal changes in the white blood cell system, cortisol level and lyzozyme activity were studied. Seasonal periodicity was found in all groups for the number of lymphocytes, segmented neutrophils and eosinophils and cortisol level. Leukocyte periodicity was found in three groups, but not in the barren mares. In lyzozyme activity there was periodicity in three groups but not in the youngest foals. In the stab neutrophils, basophils and monocytes no cycle was observed. The behaviour of the indices studied showed the influence of age of the horses (mature vs young) and the physiological state of the mares (pregnancy or barrenness).     

Diurnal changes in lactic and pyruvic acid levels and pH values in foals during the first 13 weeks of their life and in their lactating mothers.

1. The diurnal changes in the levels of lactic (LA) and pyruvic (PA) acids and values of pH were studied in standard-bred mares and their foals, for 13 weeks of foal life, throughout 2 years. 2. The studies began when a foal was 7 days old and were repeated every 2 weeks until foals reached 13 weeks of age. 3. Blood samples were taken every 4 hr for one day, each second week. 4. In the LA, PA levels and pH values no diurnal rhythm was stated in lactating mares during study periods. 5. In foals the diurnal rhythm in LA and PA occurred in the 3rd month of their life, with the acrophase at night hours. 6. The significant correlations between foal and their mother metabolites studied were observed. 7. The environmental factors (air temperature, humidity) influence fluctuations of the amplitude in parameters studied in the horse blood.     

Diurnal and seasonal cortisol, testosterone, and DHEA rhythms in boys and girls during puberty

Diurnal and seasonal rhythms of cortisol, testosterone, and DHEA were examined, as little is known about the relationship between these rhythmicities and pubertal development. Salivary samples were obtained from 60 boys and 60 girls at approximately 07:45, 08:00, 08:30, 12:00, 16:50, and 21:00 h. The participants' ages ranged from 8-14 yrs, and each participant was tested three times at six-month intervals. The study was conducted at a General Clinical Research Center (GCRC) and at the homes of the participants. All hormones showed diurnal fluctuations. The acrophase (peak time) of cortisol occurred earlier than for testosterone or DHEA and showed a seasonal effect, with the acrophase occurring earlier in spring than in summer. The cortisol acrophase also occurred later in the day for boys than for girls during later puberty. Seasonal effects were found only for cortisol with higher concentrations in the spring and summer. Cortisol concentrations were relatively stable across pubertal maturation, but significantly lower concentrations were observed at pubertal stage 3 compared to the other stages. Morning cortisol levels were also higher in boys at pubertal stage 2. Testosterone concentrations were higher in boys at pubertal stages 3 and 4, and DHEA was lower at pubertal stage 1 than 3 and 4 for both boys and girls. For the total sample, there was a positive correlation between DHEA and testosterone during early puberty (stages 1-3) but not later puberty (stages 4-5). Awakening secretory activity correlated with daytime secretory activity for testosterone and DHEA, but not for cortisol. These data provide novel chronobiological information on cortisol, testosterone, and DHEA as it relates to sexual maturation and encourage further study on both normal and abnormal endocrine rhythms.     

Diurnal and Seasonal Cortisol,Testosterone, and DHEA Rhythms in Boys and Girls during Puberty

Diurnal and seasonal rhythms of cortisol, testosterone, and DHEA were examined, as little is known about the relationship between these rhythmicities and pubertal development. Salivary samples were obtained from 60 boys and 60 girls at approximately 07∶45, 08∶00, 08∶30, 12∶00, 16∶50, and 21∶00 h. The participants' ages ranged from 8–14 yrs, and each participant was tested three times at six‐month intervals. The study was conducted at a General Clinical Research Center (GCRC) and at the homes of the participants. All hormones showed diurnal fluctuations. The acrophase (peak time) of cortisol occurred earlier than for testosterone or DHEA and showed a seasonal effect, with the acrophase occurring earlier in spring than in summer. The cortisol acrophase also occurred later in the day for boys than for girls during later puberty. Seasonal effects were found only for cortisol with higher concentrations in the spring and summer. Cortisol concentrations were relatively stable across pubertal maturation, but significantly lower concentrations were observed at pubertal stage 3 compared to the other stages. Morning cortisol levels were also higher in boys at pubertal stage 2. Testosterone concentrations were higher in boys at pubertal stages 3 and 4, and DHEA was lower at pubertal stage 1 than 3 and 4 for both boys and girls. For the total sample, there was a positive correlation between DHEA and testosterone during early puberty (stages 1–3) but not later puberty (stages 4–5). Awakening secretory activity correlated with daytime secretory activity for testosterone and DHEA, but not for cortisol. These data provide novel chronobiological information on cortisol, testosterone, and DHEA as it relates to sexual maturation and encourage further study on both normal and abnormal endocrine rhythms.     

Seasonal changes in the circadian rhythm of the total antioxidant activity of human saliva

Seasonal changes in the diurnal rhythm of the total saliva antioxidant activity were monitored using coulometric titration. One-hour shifts of the acrophase of this rhythm towards earlier hours in the spring and in the opposite direction in the autumn could be related to the practice of changing the clock to winter and summer time.     

Diurnal rhythm in the counts and types of milk somatic cells,neutrophil phagocytosis and plasma cortisol levels in Karan Fries cows during different seasons and parity

Chances of mammary infections are comparatively higher in high producing cows during harsh environmental conditions and are usually characterised by changes occurring in various somatic cells secreted in the milk and their activities. The present study was conducted to record diurnal rhythmicity in milk somatic cell counts (SCC), neutrophil: macrophage (N: M) ratio, phagocytic activity (PA) of milk neutrophils and plasma cortisol concentrations during different seasons and parity in high producing Karan Fries cows. Values of milk SCC, N: M ratio and plasma cortisol levels were lowest during thermoneutral (TN), intermediate in winter and highest during the summer season. Diurnal rhythm in the milk SCC and N: M ratio was noticed in the summer while plasma cortisol exhibited diurnal rhythm in both winter and summer seasons. Milk SCC, N: M ratio and plasma cortisol increased in multiparous cows, but diurnal variation was noticed only in the N: M ratio and plasma cortisol in cows having more than four parity. Phagocytic activity of milk neutrophils was highest during TN, intermediate in winter and lowest during the summer season. Phagocytic activity was higher and similar in cows up to fourth parity but decreased in subsequent lactation cycles. Diurnal rhythm in the PA was noticed in winter and summer seasons and in cows having more than four parity where morning samples showed higher phagocytosis as compared to the evening samples. These results can be used for immunomodulatory interventions and therapeutic approaches in treating mastitis of crossbred cows reared under tropical conditions.     

Alteration of circadian rhythmicity of CD3+CD4+ lymphocyte subpopulation in healthy aging

The CD4+ T helper/inducer and the CD8+ T suppressor/cytotoxic are major lymphocyte subsets that play a key role in cell-mediated immunity. Aging-related changes of immune function have been demonstrated. The purpose of this study is to analyze the dynamics of variation of these specific lymphocyte subsets in the elderly. In our study cortisol and melatonin serum levels were measured and lymphocyte subpopulation analyses were performed on blood samples collected every four hours for 24 hours from fifteen healthy young middle-aged subjects (age range 36-55 years) and fifteen healthy elderly male subjects (age range 67-79 years). A clear circadian rhythm was validated for the time-qualified changes of CD3+ and CD4+ cells with acrophase at night and for the time-qualified changes of CD8+ cells with acrophase at noon in young middle-aged subjects and for the time-qualified changes of CD3+ cells with acrophase at night and for the time-qualified changes of CD8+ cells with acrophase at noon in elderly subjects. No clear circadian rhythm was validated for the time-qualified changes of CD4+ cells in elderly subjects. No statistically significant correlation among lymphocyte subsets was found in elderly subjects. In elderly subjects CD3+ lymphocyte percentage was higher in the photoperiod and in the scotoperiod and cortisol serum level were higher in the scotoperiod in respect to young middle-aged subjects. In the elderly there is an alteration of circadian rhythmicity of T helper/inducer lymphocytes and this phenomenon might contribute to the aging-related changes of immune responses.     

Seasonal changes in some plasma hormones in pigeons: diurnal variation under natural photoperiods with constant or seasonally changing ambient temperature

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to constant temperature and naturally varying photoperiods. A significant seasonal variation in the mean daily levels of triiodothyronine (T3), thyroxine (T4), corticosterone (B), lutropin (LH) and FFA was seen in the outdoor birds and in the T4 and B levels of indoor birds. The diurnal variation of hormone levels was generally more pronounced in winter in both groups. Cold ambient temperature significantly decreased the plasma LH level and potentiated the increasing effect of short photoperiod on plasma B level. Diurnal variation of plasma FFA level seems to be under the control of photoperiod, without any effects due to the ambient temperature. No significant correlation was found between FFA and GH concentrations.     

Effect of photoperiod on the diurnal rhythm of plasma testosterone, dihydrotestosterone and androstenedione in mature male chickens

1. The effects of different photoperiods on the concentrations of plasma androgens, testes weight and on the diurnal rhythm of plasma testosterone (T), dihydrotestosterone (DHT) and androstenedione (A) in mature, single comb White Leghorn male chickens were studied. 2. Birds were exposed to either 14 hr of light (lights on at 0600-2000 hr) or to 24 hr of light per day. 3. Blood samples were collected from birds in both groups at 3-hr intervals and plasma levels of T, DHT and A were measured using radioimmunoassays. Following blood collection, birds were weighed, killed and testis weights were recorded. 4. Under 14 hr of light, there was a diurnal rhythm of T and DHT with hormone concentrations peaking at the end of the dark period. There was no obvious rhythm for A. Exposure to 24 hr of light abolished the diurnal rhythm found under 14 hr of light. 5. There was an increase not only in testis weights but also in body weight and hormone concentrations under 24 hr of light. 6. It was concluded that photoperiod plays an important role in controlling the concentration and rhythm of androgens in mature male chickens.     

Seasonal effects on plasma cortisol concentrations in the Bedouin buck: circadian studies and response to ACTH

Our work aims at the exploration of cortisol secretion in the Bedouin goat, native to the Algerian Sahara desert, to understand the mechanisms of adaptation to extreme hot climates. In the present study, diurnal and seasonal variations of cortisol concentrations were measured in basal conditions, as well as the response to ACTH stimulation tests across seasons in bucks. The plasma concentrations of cortisol showed no diurnal cycle but a large variation across seasons. The highest levels occurred in summer and winter when the environmental conditions are at their extreme levels. The rectal temperature showed nychthemeral and seasonal variations, and BW was also different across seasons with highest values in summer and lowest in winter. The results obtained after administration of two doses (2 or 10 μg/kg BW) of synthetic ACTH to three different age groups (kids, adults and elderly animals) showed a strong increase in plasma cortisol concentrations under all conditions with maximum levels achieved between 15 and 120 min. The analysis of the area under the cortisol curve showed no significant difference between the responses to the two doses of ACTH and between age groups, but showed seasonal variations with the lowest response in autumn than in other seasons. We conclude that season significantly affects secretion of cortisol in both basal state and under ACTH stimulation. However, the variation of adrenal reactivity to ACTH is not sufficient to explain seasonal differences, and in particular the summer peak in basal circulating cortisol concentrations. Further research should focus on the respective contribution of environmental factors (such as day length, temperature, humidity) and the mechanisms involved in cortisol regulation.     

Seasonal and diurnal rhythms of thyroidal status in the rainbow trout, Salmo gairdneri Richardson

The concentrations of thyroxine (T₄) and triiodothyronine (T₃) in the blood plasma of rainbow trout ( Salmo gairdneri Richardson) at intervals throughout the year have been measured by a chemically specific gas-liquid chromatographic (GLC) method. Mean hormone levels showed a seasonal variation, maximal levels of both hormones occurring in winter and minimal concentrations in mid summer. An apparent secondary maximum in mean T₄ and T₃ concentrations was observed in spring. (T₄)/(T₃) ratios have been found to be highest in winter and lowest in summer. A radioimmunoassay procedure, validated by GLC analyses, revealed the presence of a diurnal rhythm in serum T₄ levels of trout sampled in September and in April.     

Independence between Rhythms of Temperature and Progesterone in Mares

We investigated the ultradian and diurnal body temperature and plasma progesterone concentration rhythms and the temporal relationship between them in mares during the midluteal phase. Data were obtained from 6 mares at 3-h intervals for 3 consecutive days. Cosinor analysis showed that body temperature acrophases occurred in the evening, whereas the progesterone acrophases occurred in the early morning (3 mares) and at night (3 mares). The spectral analysis of the temperature data showed periods of 24 hr for all mares and of 8 hr for 1 mare. In contrast, the periods observed for plasma progesterone concentration were quite divergent (24 and 12 hr). The small variation in the rhythmic parameters of body temperature suggests that its oscillator system is stable. No phase relationship was detected between the rhythmometric parameters of body temperature and plasma progesterone concentration, suggesting that the physiological mechanisms of control of the 24 hr and ultradian rhythm of the two variables are not coupled during the midluteal phase.     

Independence between Rhythms of Temperature and Progesterone in Mares

We investigated the ultradian and diurnal body temperature and plasma progesterone concentration rhythms and the temporal relationship between them in mares during the midluteal phase. Data were obtained from 6 mares at 3-h intervals for 3 consecutive days. Cosinor analysis showed that body temperature acrophases occurred in the evening, whereas the progesterone acrophases occurred in the early morning (3 mares) and at night (3 mares). The spectral analysis of the temperature data showed periods of 24 hr for all mares and of 8 hr for 1 mare. In contrast, the periods observed for plasma progesterone concentration were quite divergent (24 and 12 hr). The small variation in the rhythmic parameters of body temperature suggests that its oscillator system is stable. No phase relationship was detected between the rhythmometric parameters of body temperature and plasma progesterone concentration, suggesting that the physiological mechanisms of control of the 24 hr and ultradian rhythm of the two variables are not coupled during the midluteal phase.