Seasonal variation of plasma glucagon concentrations in men

In an attempt to understand a role of glucagon in seasonal acclimatization in men, measurements of plasma glucagon, blood free fatty acids (FFA), blood glucose, blood ketone body (beta-hydroxybutyrate) and hematocrit were made in 13 male and 8 female college staff members, aged 20 to 42, once a month for one year. Blood samples were obtained at 4:00 to 5:00 p.m, between meals. Average monthly temperatures during the study were as follows; Jan. -7.8, Feb. -5.6, March -3.7, Apr. 4.6, May 11.4, June 18.3, July 23.9, Aug. 22.0, Sept. 14.7, Oct. 7.5, Nov. 1.4, Dec. -4.2 (degrees C). Plasma glucagon, blood FFA and blood ketone body exhibited significant monthly variation in both sexes. Plasma glucagon as well as blood FFA level was significantly higher in winter (Dec., Jan., Feb.) than in summer (June, July, Aug), whereas blood ketone body level was lower in winter than in summer. Plasma glucagon level was significantly lower in female than in male subjects. A significant positive correlation was observed between plasma glucagon and blood FFA levels throughout the year. Seasonal variations of blood glucose and hematocrit were not observed. These results suggest that seasonal variation in glucagon secretion is associated with seasonal changes in ambient temperatures as one of the strategies for climatic acclimatization through regulation of lipid metabolism.     

Seasonal variation of antibody levels among pigeon fanciers

IgG antibody against avian antigens was measured by quantitative radioimmunoassay in serum samples obtained regularly from twenty pigeon fanciers over a 1-year period. A seasonal variation was seen in nine antibody-positive subjects; eight of whom had symptoms of pigeon breeder's disease (PBD), and a clear peak of antibody production occurred during late summer, corresponding with the period of maximum avian contact in the sporting season. All subjects with insignificant specific IgG levels were asymptomatic and displayed minimal changes throughout the year despite a similar exposure pattern to antigen for all individuals. Raised total IgG was a feature of six symptomatic subjects, two of whom had raised total IgA. Three of these six subjects had maximum hypergamma-globulinaemia coinciding with peak specific-antibody levels, but in general the total imrnunoglobulin levels tended to remain high throughout the year with only marginal fluctuations. The total immunoglobulin levels in the other individuals were within normal limits and displayed no remarkable changes during the year. The subjects with pigeon breeder's disease had a more active immune responsiveness to avian contact, and the association of the highest levels with periods of maximal contact with antigen may have an important bearing on the dynamic nature of this condition.     

Seasonal variation of peripheral thyroid hormone levels in major depression.

The seasonal variation in thyroid function tests was examined in 138 patients with major depression. No alterations in thyroxine, free thyroxine index, triiodothyronine, T3 resin uptake and thyrotropin were observed across the four seasons. This applied to both male and female subgroups. These data suggest that seasonality does not account for the wide variability in abnormalities of thyroid function reported in depression.     

Seasonal variation in antioxidant enzyme activity in seminal plasma in Holstein bulls

Seminal oxidative stress status is emerging as a significant prognostic tool in assisted reproductive technology. A dynamic interplay between pro- and anti-antioxidant substances in the ejaculate is essential. In this study, we determined seasonal changes in the activity of the antioxidant enzyme defence system comprising catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) in seminal plasma (SP) of mature Holstein bull’s semen. Samples were collected by a bovine artificial vagina from 30 sexually mature Holstein bulls, and CAT, GPx and SOD activities were determined for different seasons. The CAT enzymatic activity determined in SP was greater in autumn as compared with other seasons (P < 0.01). Significantly lower GPx activity was found in winter compared with other seasons (62 ± 12 versus 133 ± 35; P < 0.01). However, SOD was not significantly affected by the season. The results reported confirm the influence of season on sperm quality. Furthermore, this study presents convincing evidence that SP composition is important in determining the antioxidant defence system of ejaculated spermatozoa.     

Effect of apomorphine and haloperidol on plasma cortisol levels in conscious dogs

Cortisol levels were measured in peripheral plasma of conscious dogs after i. v. administration of apomorphine, a dopaminergic agonist, haloperidol, a dopaminergic antagonist, or apomorphine in combination with haloperidol. Apomorphine in a dose of 0.001 and 0.005 mg/kg did not cause any release of cortisol whereas 0.01 and 0.05 mg/kg caused a dose dependent and peakshaped increase of plasma cortisol levels from 20 to 30 and from 20 to 60 ng/ml respectively. Basal levels were reached again within 1 h. Haloperidol (0.1 mg/kg), when given alone, induced a continuous rise of plasma cortisol levels. After 60 min the levels were ?80 ng/ml and still tended to rise. Jf apomorphine (0.01 mg/kg) was given 30 min after the injection of haloperidol (0.1 mg/kg) no further effect of the apomorphine injections was observed. We therefore speculate that apomorphine activates central dopaminergic receptors which cause a release of ACTH from the pituitary into the circulation, which in turn stimulates the release of cortisol from the adrenals. The fact that not only apomorphine but also haloperidol stimulated cortisol release suggests a complex role of dopamine transmission involving different dopaminergic pathways as well as different dopamine receptors. It is also possible that injection of haloperidol induces a stress reaction in the dogs, which causes a release of cortisol from the adrenals.     

Influence of personality traits on plasma levels of cortisol and cholesterol

The literature reports many organic malfunctions that are associated with elevated plasma cortisol and cholesterol levels. The present investigation was concerned with the influence of personality on plasma levels of cortisol and cholesterol. To that effect these variables were determined in a group of 20 subjects who answered the Big-Five Inventory for measurements of personality traits. It was found that: among the 5 personality traits, extraversion was positively correlated to plasma levels of cortisol and cholesterol while the correlation was negative for neuroticism. The positive correlation between extraversion and plasma cortisol and cholesterol, as well as with the responses to stress as shown in a previous study, are similar to findings previously reported on type A individuals. Further studies are needed with a larger group of subjects to conclude to a direct causal relationship between extraversion and the high levels of plasma cortisol and cholesterol, or a predisposition to some organic malfunctions as is the case for type A.     

Mental task-induced strain and its after-effect assessed through variations in plasma cortisol levels

Plasma cortisol levels were measured in 20 healthy men while they carried out mental tasks in intermittent noise. Half the subjects performed a serial short-term memory task and, later on, a multiple-choice task, whereas the other half performed only the multiple-choice task. The aim of the experiment was to determine whether enhanced cortisol release, due to a centrally mediated arousal reaction, depressed the cortisol level when the subjects had to cope with a new task situation. In a previous study, such a regulatory after-effect was revealed in the midday meal-related cortisol peak, but not in a subsequent exercise-induced cortisol peak, although cortisol release in both cases could be related to metabolic changes. The results showed that the second mental task still induced a pronounced rise in cortisol levels. No changes in task performances were found. It is concluded that different regulatory mechanisms are involved in adrenocortical secretion, depending on the origin of the stimulation, and that cortisol responses are closely related to individual coping abilities and strategies.     

Circadian variation of plasma atrial natriuretic peptide, cortisol and fluid balance in the goat

Circadian variation of plasma atrial natriuretic peptide (ANP), cortisol and fluid balance was studied in ten adult female goats. The concentrations of plasma antidiuretic hormone (ADH), electrolytes, creatinine and total protein, as well as plasma and urine osmolalities and renal electrolyte excretion and clearances (Cosm, CH2O, Ccrea), were used to evaluate fluid balance. At 3-h intervals, urine was collected from five goats and venous blood samples from all ten goats. Urethral catheterization had no effect on the results. Besides the lower plasma creatinine level in the dark than in daylight, no other changes were observed in relation to luminousness. Plasma concentrations of ANP, ADH, total protein and K, urine flow rate and osmolality, urine concentrations of Na, K and creatinine, renal Na and K excretion, Cosm, CH2O and Ccrea, and haematocrit showed no circadian variation. Circadian variation was observed in plasma osmolality (P < 0.05) and the concentrations of Na (P < 0.05) and creatinine (P < 0.05), with achrophases around 16:00 hours and nadirs between 01:00 and 07:00 hours. Changes in osmolality and Na followed the feeding schedule. There was a small elevation in plasma cortisol levels in six goats after midnight, which may be the consequence of circadian rhythm. In conclusion, the results suggest that in plasma ANP no circadian rhythm exists.     

Identification of cis-regulatory variation influencing protein abundance levels in human plasma

Proteins are central to almost all cellular processes, and dysregulation of expression and function is associated with a range of disorders. A number of studies in human have recently shown that genetic factors significantly contribute gene expression variation. In contrast, very little is known about the genetic basis of variation in protein abundance in man. Here, we assayed the abundance levels of proteins in plasma from 96 elderly Europeans using a new aptamer-based proteomic technology and performed genome-wide local (cis-) regulatory association analysis to identify protein quantitative trait loci (pQTL). We detected robust cis-associations for 60 proteins at a false discovery rate of 5%. The most highly significant single nucleotide polymorphism detected was rs7021589 (false discovery rate, 2.5 × 10(-12)), mapped within the gene coding sequence of Tenascin C (TNC). Importantly, we identified evidence of cis-regulatory variation for 20 previously disease-associated genes encoding protein, including variants with strong evidence of disease association show significant association with protein abundance levels. These results demonstrate that common genetic variants contribute to the differences in protein abundance levels in human plasma. Identification of pQTLs will significantly enhance our ability to discover and comprehend the biological and functional consequences of loci identified from genome-wide association study of complex traits. This is the first large-scale genetic association study of proteins in plasma measured using a novel, highly multiplexed slow off-rate modified aptamer (SOMAmer) proteomic platform.     

Seasonal variation in human fecundability

Seasonality of effective fecundability was investigated in a cohort of 402 women born in or near Rotterdam, The Netherlands, between 1873 and 1887, and married before the age of 40 years. Applying a newly developed method allowing simultaneous control for inherent couple fecundability, numbers at risk of pregnancy, and multiple confounders, we found a trend towards higher fecundability during the first half of June and the first half of December (P = 0.06). Seasonality of effective fecundability appeared to be strongest for women who married at <20 years of age. Potentially important implications for the study of seasonality of adverse reproductive outcome are discussed.      

Nocturnal variation in plasma levels of gastrin and somatostatin-like immunoreactivity in man

Somatostatin and gastrin-like immunoreactivity was measured in peripheral venous plasma at 22, 24, 02, 04 and 06 hours in 10 experiments performed on 6 healthy volunteers. In five of the experiments the subjects had been pretreated with propranolol 20-40 mg three times daily for one week. At 22 h gastrin and somatostatin levels averaged 153 and 143 pg/ml without treatment with beta-blockers and 93 and 74 with such treatment. Gastrin and somatostatin levels fell during the course of the night to approximately 10 and 60% of the 22 h value, respectively. Somatostatin levels reached their lowest value at 02 h (50%) of the 22 h value. Treatment with beta-blockers tended to decrease gastrin as well as somatostatin levels over the whole experimental period, but did not influence the gradual decline of gastrin and somatostatin levels occurring during the night or the 02 h dip in somatostatin levels. It is suggested that the nocturnal dip in somatostatin secretion is vagally mediated and that the peak in acid output occurring at this hour is due to the decreased output of gastric somatostatin. The fact that the nightly dip in somatostatin secretion coincides with the peak output of the pituitary hormones prolactin and growth hormone is discussed.     

Social housing conditions around puberty determine later changes in plasma cortisol levels and behavior

A recent study found that male guinea pigs raised in large, mixed age/sex groups exhibited an unexpected suppression of their cortisol response at 4 mo of age. The present study examined the effect of social experience around the time of puberty on cortisol response suppression and social behavior at 4 mo of age. Males reared in large, mixed age/sex groups were either pair-housed with a female or moved to another large colony at 55 days of age. When tested at 4 mo, pair-housed males exhibited much higher levels of courtship and sexual behavior than did colony-housed males, and a shorter latency to begin courtship when with an unfamiliar adult female. In addition, pair-housed males showed much higher levels of agonistic behavior and a shorter latency to escalated aggression with an unfamiliar adult male. Pair-housed males also had lower basal cortisol concentrations and exhibited a greater increment in cortisol levels when isolated in a novel cage than did colony-housed males. Finally, pair-housed males showed a smaller increment in cortisol levels when with the stimulus female or male than when isolated, but colony-housed males did not. The findings demonstrate that social housing conditions around the time of puberty can have pervasive effects on social behavior and hypothalamic-pituitary-adrenal (HPA) activity in 4-mo-old males. Further, these findings are consistent with the notion that changes in HPA activity contribute to social behavior development beyond the time of sexual maturity.     

Seasonal variation in postnatal depression

BACKGROUND: We evaluated the occurrence of postnatal depression in general and during different seasons as part of a larger longitudinal mother-child follow-up study. METHOD: One hundred and eighty-five mothers, from the maternity wards of University Hospital of Oulu, Finland, completed a self-rating depression scale, the Edinburgh Postnatal Depression Scale (EPDS) twice: first at hospital 2-7 days after delivery and the second time at home 4 months after the delivery. Different psychosocial variables were mapped out to avoid any confounding factors. The year was divided in two separate ways: first, three different time periods were selected by the amount of sunlight: dark (October-January), intermediate (February, March, August, September) and light (April-July), and second, the year was divided by seasons. The results were analysed by the chi(2)-test for multinomials. RESULTS: Sixteen percent (16.2) of mothers were scored as being depressed using 13 as a cut-off point immediately after the infant was born. Thirteen percent (13.0) were depressed measured 4 months postpartum. There was more mild depression in the autumn (ratio observed/expected 1,62; 95% confidence interval 1.05-2.19) immediately after delivery, using 10 as a cut-off, and less depression in the spring (0.27; 0.00-0.62) measured at home later, using 13 as a cut-off. When using classification by the amount of light there was more depression during the dark time (1.58; 1.05-2.11) immediately postpartum. LIMITATIONS: The group sizes and the amount of sample sizes collected within each month are quite small. CONCLUSIONS: It should be borne in mind that seasonal changes and alterations in the amount of light might influence the occurrence of postnatal depression.     

Psychologic stress increases plasma levels of prolactin, cortisol, and POMC-derived peptides in man

Stressful social interactions have been shown to elicit increases in heart rate as well as in plasma levels of epinephrine, norepinephrine, and cortisol in humans. We sought to determine whether a competitive oral examination would affect plasma levels of the pituitary hormones ACTH, beta-endorphin, beta-lipotrophic hormone, and prolactin in a group of healthy young males. Seven min after beginning the examination, heart rate increased 27% and plasma levels of ACTH, beta-endorphin, beta-lipotropic hormone and prolactin rose 59%, 79%, 42%, and 46%, respectively, compared to values shortly before the examination. These hormone values returned to initial levels after the subjects returned to the waiting room. Plasma cortisol changes were similar in direction to those of ACTH but occurred about 15 min later. The present study demonstrates that a stressful social interaction can elicit rapid increases in plasma levels of the proopiomelanocortin derived peptide hormones and prolactin in man.     

Spontaneous afternoon plasma cortisol in depression

Spontaneous plasma cortisol was measured in the interval from 15.00-18.00 h 74 hospitalized depressed patients (56 endogenously and 18 non-endogenously depressed according to the Newcastle index). The cortisol value at the individual time points correlated well with the mean cortisol concentration with the best correlation in the interval between 16.00 and 17.00 h (RHO = 0.89-0.92). For most patients maximum cortisol concentration was found early in the sampling period. Plasma cortisol was high during depression and was reduced after recovery in both diagnostic groups. Correlation between plasma cortisol during depression and type of depression or degree of depression was poor indicating that spontaneous plasma cortisol might have only a limited diagnostic value. However, among the endogenously depressed patients those not responding to treatment with cyclic antidepressants alone had significantly higher cortisol levels prior to treatment than responders. Afternoon plasma cortisol thus may be used as a predictor of the outcome of treatment with cyclic antidepressants.     

Genetic variation at fibrinogen loci and plasma fibrinogen levels.

In view of the controversy regarding genetic variation at the fibrinogen loci and plasma fibrinogen levels, we have analysed DNA polymorphisms at the alpha (TaqI), beta (BclI and HaeIII), and gamma (KpnI/SacI) fibrinogen loci in 247 subjects whose plasma fibrinogen was determined by clotting and nephelometric assays. Strong linkage disequilibrium was found between the alpha/TaqI and gamma/KpnI/SacI markers and between the beta/BclI and beta/HaeIII markers. A lesser association was found between the alpha/TaqI and beta/BclI loci, beta/BclI and gamma/KpnI/SacI markers, alpha/TaqI and beta/HaeIII markers, and the gamma/KpnI/SacI and beta/HaeIII markers. This is consistent with the known physical order of these loci and suggests a relative excess of recombination in the alpha/gamma to beta interval. Plasma fibrinogen levels, by either assay method, when corrected or uncorrected for age, sex, and smoking habit, did not show any statistically significant associations with the four fibrinogen polymorphisms examined at the alpha, beta, and gamma fibrinogen loci either singly or when analysed as a haplotype.