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PubMed1979

Seasonal changes in malnutrition and diarrheal disease among preschool children in El Salvador.

The nutritional status of preschool children in a rural El Salvadoran population was assessed quarterly for 1 year using height, weight and arm circumference measurements in order to define seasonal changes in malnutrition. Seasonal patterns in the incidence of reported malnutrition and diarrheal disease from the local clinic serving the study population and on the national level for EL Salvador were also assessed and were compared with field measurements. Results indicated a similar seasonal increase in both measured malnutrition and in the reported incidence of malnutrition and diarrheal disease occurring at the onset of the rainy season. The results confirm the existence and indicate the magnitude of seasonal changes in malnutrition and diarrheal disease in a preschool population.

Body Height↗

PubMed1979

[Seasonal dynamics in the occurrence of bovine trichophytosis and human dermatomycosis in Czechoslovakia].

The occurrence of the outbreaks of bovine trichophytosis and numbers of people affected by this disease in the Czech Socialist Republic were studied in 1966 to 1977. The effectiveness of the preventive and therapeutic measures against the causative agents of the disease is proved by a marked drop of the number of outbreaks in all months in the mentioned period. The greatest drop was in March (74.9) and April (70.1 annually) and lowest in June to August (24.6 to 27.8 annually). Despite the drop of the number of trichophytosis outbreaks, the number of ill animals slightly rose (+402 heads). The slow decrease of the number of trichophytosis outbreaks in summer requires more intensive therapeutic and preventive activity. Summer emptying of stables, supporting the devitalization of dermatophytes, should be used in the sanitation of the houses. The highest monthly seasonal indices of bovine trichophytosis were found in May and April (more than 13% above the annual average), and the lowest in December (23% below the average) and in November (12.5% below the average). The seasonal occurrence of dermatomycoses in man does not coincide with the seasonal occurrence of the disease in cattle. The seasonal index is at its maximum in winter (January-March), reaching 13-15% above the average. The lowest value of the seasonal index was found in August (20% below the long-term average).

Animals↗

PubMed1978

Effects of haemoglobin electrophoretic pattern and seasonal changes on urine concentration in young adult Nigerian males.

Renal concentrating capacity has been measured in healthy young adult Nigerian males with normal (AA) and abnormal (AS) haemoglobin types in both the dry and the wet seasons after 13 to 15 hours hydropenia respectively. The results show that, in the dry season, urine osmolality values in AA subjects are similar to those observed in Caucasians. They further confirm that renal concentrating capacity is impaired in persons with the S gene, and emphasize the limitations of the specific gravity test as a measure of renal concentrating capacity. In healthy AA subjects, the urine osmolality during the wet season is significantly less than in the dry season, even after longer periods of hydropenia. AS subjects, on the other hand, exhibit no seasonal variation in renal concentrating capacity.

Adult↗

PubMed1979

Localization of gonadotrophin-releasing hormone (GnRH) in the hypothalamus of ovariectomized pony mares by season.

Fifteen Pony mares, ovariectomized during the previous summer, were randomly assigned to three seasonal treatment groups, winter, spring and summer (N = 5). At the designated season, the animals were killed and hypothalamic areas were collected and assayed by radioimmunoassay for gonadotrophin-releasing hormone (GnRH) activity. The hypothalamic areas were sectioned into 54 5-mm cubes to determine the sites of GnRH storage. Maximum immunoreactive GnRH activity was located in an oblique pattern extending from the arcuate nucleus-median eminence area to the anterior hypothalamic area dorsally and anteriorly. While total hypothalamic GnRH concentrations were not significantly different among seasons (P greater than 0.05), there was a trend towards increasing concentrations in the summer season. Distribution of GnRH activity was significantly different among seasons (P less than 0.05), the change in distribution occurring in the ventral to dorsal plane, as well as anteriorly to posteriorly.

Animals↗

PubMed1979

Age, sex, and season of onset of juvenile diabetes in different geographic areas.

Age, sex, and estimated time of onset of insulin-dependent diabetes were determined for children in Pittsburgh (N = 673), Gainesville (N = 976), Galveston (n = 741), and Melbourne (N = 851). The US cities had a decrease in new cases during the summer and peak incidence in January through April. In Melbourne, monthly trends were reversed: there were more cases during May through August. In US cities, but not in Melbourne, children less than 6 years old showed a greater variation by season than children 6 years old and older. Observations of the same fall and winter onset (in different calendar months) of insulin-dependent diabetes in Australia and the United States, and exaggeration of seasonal differences in young US children, suggest that onset of insulin-dependent diabetes is associated with seasonally varying viral diseases. Mumps and rubella infections do not seem to be responsible for much of the seasonal variation. Seasonal peaks of mumps and rubella are later than those observed for insulin-dependent diabetes, and immunization with live mumps and rubella viruses has not been associated with changes in incidence of insulin-dependent diabetes. An increase in disease incidence in boys over girls below age 6 years and in girls over boys at ages 6 through 11 years was consistently observed but not explained.

Adolescent↗

PubMed1979

Observations on ostertagiasis in young cattle over two grazing seasons with special reference to plasma pepsinogen levels.

The epidemiology of ostertagiasis in south west Scotland was studied in groups of cattle grazed through two successive grazing seasons separated by a period of winter housing. Towards the end of the first grazing season (September) the numbers of infective larvae (L3) on the pasture had increased to high levels (up to 24,000 L3 per kg) which resulted in high faecal egg counts, worm burdens, plasma pepsinogen levels and the occurrence of clinical ostertagiasis in the calves. By late spring (May) at the onset of the second grazing season, there was an almost complete mortality of the overwintered L3 on the pasture followed by the appearance of moderately high numbers of a new population of L3 in September (up to 9000 L3 per kg). The latter increase in the numbers of L3 was reflected by negligible faecal egg counts, low worm burdens and a moderate elevation of plasma pepsinogens in the second year animals. It therefore seems that although young cattle acquire a good immunity to Ostertagia ostertagi after one season at grass the small infections established in the early part of the second season are capable of contaminating the pasture to levels which could be dangerous for susceptible stock. An allergic reaction in the abomasal mucosa could be the basis of the elevated pepsinogens present in the second year animals.

Animals↗

PubMed1978

Psychiatric disorder, hospital admission, and season.

Psychiatric disorder has been considered to have seasonal variation for a long time. The studies to date have suffered frequently from small samples and imprecise terminology, and the results have been inconclusive. This study has attempted to overcome these difficulties by examining hospital admissions to all facilities in the province of Ontario for a six-year period, with each year carefully divided into seasons. Statistically significant seasonal variation, with peaks in the spring and fall, was found overall for neurotic and endogenous depression. Alcoholism also showed a spring peak. No other diagnoses, overall, showed seasonality, although personality disorders, drug addictions, and transient situational disturbances exhibited trends similar to neurotic depression for certain age and sex groups. The findings are discussed in terms of their clinical and research significance.

Adjustment Disorders↗

PubMed1976

Adenohypophysial cell-types in the pituitary gland of the soft-shelled turtle, Trionyx sinensis. I. Seasonal cycles.

By using various staining techniques, two acidophilic and three basophilic cell-types have been distinguished in the pars distalis of Trionyx sinensis. Seasonal fluctuations in their cytoplasmic granulation, cell and nuclear size have been compared with seasonal patterns of activity in the gonads, adrenals and thyroid. On the basis of the results, specific functions have been ascribed to each cell-type. Basophils 1 activity closely parallels the seasonal thyroid cycle. Basophils 2 are probably FSH-secreting gonadotropes and their activity correlates with the seasonal cycle of spermatogenesis in the seminiferous tubules. The functional activity of the testicular interstitial cells correlates with the secretory pattern of the basophils 3. That these are LH-secreting cells is also suggested by the epididymidal cycle, which indicates a high level of androgen secretion coincident with the rapid degranulation of these cells, at a time of no spermatogenetic activity. Adrenal activity shows no relationship with the basophils 3 cycle, and chromophobic cells may be the locus of ACTH secretion. Acidophils 2 remain stable throughout the year and are probably somatotropes, but acidophils 1 increase their activity in autumn and are likely to be lactotropes.

Adrenocorticotropic Hormone↗

PubMed1978

Effect of seasonal variation on lymphoid tissues of the lizards, Mabuya quinquetaeniata Licht. and Uromastyx aegyptia Forsk.

The thymus in the lizards Mabuya quinquetaeniata and Uromastyx aegyptia is highly involuted in winter but exhibits in the other seasons a rich lymphoepithelial organization. The splenic white pulp is severely depleted in winter but is extensively developed in spring, summer and autumn. In these seasons, the splenic lymphoid tissue of Mabuya occurs in a continuous phase throughout the organ obscuring the red pulp, whereas in Uromastyx the white pulp remains localized as periarteriolar aggregates and the red pulp is always clearly delineated. In both lizard species, gut-associated lymphoid tissue is well represented, especially in the large intestines and in Mabuya it is almost similar in different seasons. In Uromastyx, in winter, lymphoid nodules are only found in the caecum and the colon, but during warm seasons, inumerable nodules are distributed throughout the gut. The findings are important for a clearer understanding of immunologic competence in reptiles.

Animals↗

PubMed1979

Seasonal acclimatisation in the hen.

1. The oxygen consumption and body temperature of White Leghorn x Rhode Island Red laying hens, which were being kept in a semi-natural climate, were periodically measured for short periods at ambient temperatures between 2 and 32 degrees C in a suitable chamber. 2. A seasonal shift was observed in lower critical temperature (Tc) and thermoneutral oxygen consumption. The slope of the relationship between oxygen consumption and air temperature at less than Tc was not discernibly affected by season. 3. The seasonal shifts correlated best with mean daily outside temperature Ta) during the experimental periods; a seasonal decrease of 10 degrees C in Ta was associated with a decrease of 8.5 degrees C in Tc and a 12% increase in thermoneutral oxygen consumption. 4. The capacity to maintain body temperature stability at extremes of environmental temperature was improved by acclimatisation to heat.

Acclimatization↗

PubMed1976

Seasonality, natality and herd immunity in feline panleukopenia.

Feline panleukopenia (FPL) was diagnosed in 185 of 7043 feline admissions (2.63%) at a university veterinary hospital over an eight-year period. FLP has a distinct seasonal pattern, occurring during July, August and September. Seasonal peaks were noted in all the years studied. Cats less than one year of age accounted for 70% of the total morbidity. The birth of felines in the United States also assumes a distinctly seasonal pattern. Analysis of 47,786 purebred litters born during 1970-1972 revealed a peak during April, May and June with a national median of May 29. A unifying hypothesis is presented to account for the seasonal occurrence of FPL. An influx of susceptible cats occurs annually following the birth of large numbers of kittens each spring, and disappearance of maternal immunity during the next two to three months. The addition of a large number of susceptible kittens leads to the development of summertime epidemics and serves to exemplify the principles of "herd immunity."

Animals↗

PubMed1979

Seasonality and the requirements for perpetuation and eradication of viruses in populations.

Perpetuation of a virus in a population is distinct from the ability to persist in a cell culture or individual host. Parameters which determine perpetuation include: 1) the size of the population; 2) the turnover of the population; 3) the proportion of immunes in the population; 4) the transmissibility of the infection; and 5) the generation time between sequential infections. These parameters may be grouped into two composite factors which most directly affect transmission dynamics and perpetuation: (a) population turnover per generation period, and (b) transmissibility or the fraction of susceptibles infected per existing infection. Perpetuation in small populations usually requires either the ability to persist in individuals or rapid population turnover. Conversely, human viruses which initiate only acute infections require larger populations to persist. Seasonal variation in transmissibility can greatly increase the minimum population size in which persistence is possible, and we argue that the population size of 500,000 for measles persistence (described by Bartlett) is primarily a consequence of seasonal variation. Computer modelling can be used to examine the effect of changes in parameters which determine the seasonal cycle of virus perpetuation and fadeout. Finally, human infections are reviewed to indicate those which have been eradicated (smallpox), are on the threshold of eradication (poliomyelitis), are possibly eradicable (measles), or could be candidates for future efforts (hepatitis A and hepatitis B). In developing a strategy for eradication two points are of great potential utility: first, the seasonal trough should be exploited as a time for effective intervention; and, second, containment efforts should be directed at epidemiologically important population groupings such as schools.

Animals↗

PubMed1979

A shifting seasonality of schizophrenic births.

In view of recent findings in Japan, and in England and Wales, data on schizophrenic births in the United States were reexamined to see if seasonal shifts had occurred. In Missouri a progressive shift from February to April and May was noted between 1921 and 1930 and between 1941 and 1950. In five New England states there was no shift over the same period. Data were then obtained to compare the Missouri shift with two hypotheses previously put forward to explain schizophrenic birth seasonality: (1) that it is related to the seasonality of general births, and (2) that it is related to seasonal temperature variation. Neither hypothesis was supported by the data.

Adult↗

PubMed1977

Thyrotropin releasing hormone (TRH) in pineal and hypothalamus of the frog: effect of season and illumination.

The influence of photo-illumination and season on the pineal and hypothalamic content of TRH in the leopard frog (Rana pipiens) was studied. Animals (4-6 in each group) were exposed to constant light or darkness for 72 h and then sacrificed. The pineal and hypothalamus from each frog were extracted for TRH measurement by radioimmunoassay. The experiment was performed in spring, autumn, early winter and mid-winter. In early winter, mid-winter and spring the pineal content of TRH ranged from 0.14-0.70 ng. Significant differences between groups due to season and illumination were recorded. In autumn, mean levels of TRH were 12.95 ng (dark exposed) and 4.19 ng (light exposed)-values 10-20 times higher than at other times of the year (P less than 0.001). The hypothalamic content of TRH ranged from 11.4 ng in spring to 19.5 ng in autumn. Seasonal differences were present, but no effect of light or darkness was found. There was no definite relation between the TRH levels in hypothalamus and pineal. The alteration in pineal and hypothalamic TRH produced by season, and the effect of illumination on pineal TRH content, support the view that TRH has a neuronal function in vertebrates, possibly as a neurotransmitter.

Animals↗

PubMed1979

Seasonal variation and the influence of body temperature on plasma concentrations and binding of thyroxine and triiodothyronine in the woodchuck.

Woodchuck plasma was collected during four seasons of the year and assayed for total and dialyzable (free) T4 and T3 and for rT3. Plasma concentrations of total and free T4 and T3 were higher in the spring (T4, 5.4 +/- 0.6 microgram/dl; free T4, 3.0 +/- 0.4 ng/dl; T3, 202 +/- 22 ng/dl; free T3, 0.51 +/- 0.04 ng/dl) and lower in the prehibernatory fattening period in summer (T4, 2.3 +/- 1.0 microgram/dl; free T4, 1.2 +/- 0.5 ng/dl; T3, 45 +/- 27 ng/dl; free T3, 0.16 +/- 0.10 ng/dl) and fall (T4, 3.2 +/- 1.0 microgram/dl; free T4, 1.3 +/- 0.2 ng/dl; T3, 130 +/- 12 ng/dl; free T3, 0.25 +/- 0.02 ng/dl). In spite of the extremely high concentrations of T3 in the winter (437 +/- 32 ng/dl), free T3 concentrations (0.034 +/- 0.003 ng/dl), when measured at the appropriate temperature for hibernation, were significantly lower than those found at other seasons of the year. Plasma binding of T3 was lower during the summer and increased again to approximately double the spring value during the winter. rT3 was at or below the sensitivity of the method (6 ng/dl) at all seasons. It is suggested that the wide seasonal variations in thyroid hormone concentrations and altered plasma protein binding may represent important adaptations influencing the metabolic rate and the process of hibernation in the woodchuck.

Animals↗

PubMed1975

Seasonal patterns of sleep stages and secretion of cortisol and growth hormone during 24 hour periods in northern Norway.

A group of 7 healthy male subjects was studied in regard to sleep stages and 24 h plasma cortisol and growth hormone patterns during the 4 seasons of the year in an Arctic environment (Tromsø, Norway). No difference in total sleep or sleep stage per cents was found for any of the yearly seasons. A small but statistical significant increase in mean plasma cortisol concentration and amount secreted for 24 h was found for the autumn-winter seasons, as compared with the spring and summer. However, no difference in the circadian curve of cortisol hormonal pattern was found. All subjects secreted growth hormone shortly after sleep onset at night and no difference was found as a function of season of the year.

Adult↗

PubMed1979

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.

Acclimatization↗

PubMed1975

Effect of season on some characteristics of stallion semen.

Season had a pronounced effect upon seminal pH and refractometer 'protein', total carbohydrate, dry weight, total N2 and lactic acid in seminal plasma of first and second ejaculates. In addition, total seminal volume, spermatozoa per ml and per ejaculate, non-protein sulphhydryl and glycerylphosphorylcholine of second ejaculates were also influenced. There was a season difference in the concentrations of lactic acid in spermatozoa from first and in total N2 from spermatozoa in second ejaculates. The effects of season on seminal plasma were greater than those on spermatozoa. Spermatozoa in first ejaculates were less affected by season than those in secons ejaculates. This differential effect on first and second ejaculates was generally true of all seminal characteristics.

Animals↗