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At least 991 records · Page 55Linked to original sources
PubMed1996

Season of birth and eating disorders.

A statistically significant season of birth variation is found in an unselected nationwide sample of 1,939 eating disorders patients, with peak season of birth occurring in May. However, among younger patients (n = 882), peak season of birth is in March, which is statistically significantly different to that expected from the general population season of birth cycle. This finding may imply links between etiology of earlier-onset eating disorders and the psychoses; similar first quarter peak seasonal patterns of birth have been found in schizophrenic and affective psychoses--with birth peaks in January and February. In contrast, for the neuroses and personality disorders, birth peaks have been found to be in June and August, similar to the June birth peak found in this study for later-onset eating disorders (n = 1,057), which was not statistically significantly different to season of birth peaks expected from general population data.

Adult↗
PubMed2000

Seasonality of eating pathology on the eating attitudes test in a nonclinical population.

OBJECTIVE: To determine whether there are seasonal fluctuations in eating pathology in a nonclinical population. METHOD: The Eating Attitudes Test (EAT) was completed by 322 subjects during winter and again during summer. Summer and winter responses were compared to investigate differences in EAT total and subscale scores and for individual EAT items. Numbers of subjects fluctuating across the seasons by more than 2 SDs of the cohort's scores were identified. RESULTS: The cohort showed no significant seasonal change on EAT-40 totals, EAT-26 totals, or within the EAT subscales. There were significant (p <.025) seasonal fluctuations on four of the EAT-40 questions. For individual respondents, there was no greater likelihood of scoring significantly higher in the winter than in the summer. DISCUSSION: Clinically significant seasonal fluctuations in eating pathology on the EAT did not occur in this nonclinical population. It is debatable whether items within the EAT which show significant seasonal fluctuations should be retained or discarded.

Adult↗
PubMed2001

Environmental and seasonal adaptations of the adrenocortical and gonadal responses to capture stress in two populations of the male garter snake, Thamnophis sirtalis.

Stress and reproduction are generally thought to work in opposition to one another. This is often manifested as reciprocal relationships between glucocorticoid stress hormones and sex steroid hormones. However, seasonal differences in how animals respond to stressors have been described in extreme environments. We tested the hypothesis that garter snakes, Thamnophis sirtalis, with limited reproductive opportunities will suppress their hormonal stress response during the breeding season relative to conspecifics with an extended breeding season. The red-sided garter snake, T.s. parietalis, of Manitoba, Canada, has a brief breeding season during which males displayed no change in either plasma levels of testosterone or corticosterone, which were both elevated above basal levels, in response to capture stress. During the summer, capture stress resulted in increased plasma corticosterone and decreased testosterone. During the fall, when mating can also occur, males exhibited a significant decrease in testosterone but no increase in corticosterone in response to capture stress. The red-spotted garter snake, T.s. concinnus, of western Oregon, has an extended breeding season during which males displayed a stress response of increased plasma corticosterone and decreased testosterone levels. The corticosterone response to capture stress was similar during the spring, summer, and fall. In contrast, the testosterone response was suppressed during the summer and fall when gametogenesis was occurring. These data suggest that male garter snakes, in both populations, seasonally adapt their stress response but for different reasons and by potentially different mechanisms. J. Exp. Zool. 289:99-108, 2001.

Adaptation, Physiological↗
PubMed2005

Seasonal influence on the onset of idiopathic inflammatory myopathies in serologically defined groups.

OBJECTIVE: To assess possible seasonal patterns in the onset of polymyositis (PM) and dermatomyositis (DM). METHODS: The study group comprised 503 patients who met the criteria for probable or definite PM or DM and for whom detailed data on the time of myositis onset were available. Statistical analyses were performed using a Poisson model that assessed associations of ethnicity, sex, autoantibody presence, and month of onset of muscle weakness. RESULTS: There were no significant seasonal patterns of disease onset in myositis patients as a whole or in the total PM or DM populations. Significant seasonal associations were present, however, in the serologically defined groups. In the 131 patients with antisynthetase autoantibodies who were categorized as non-black, myositis onset peaked in March-April (P = 0.03). Among the antisynthetase-positive patients, the association was predominantly in those with PM (n = 85; P = 0.05) and in men (n = 51; P = 0.042). Patients with anti-signal recognition particle autoantibodies, however, did not have a significant seasonal onset, which is in contrast to previous findings. Patients without myositis-specific autoantibodies showed a significant peak in summer, with myositis onset in June-July (n = 252; P = 0.03); this seasonal association was significant in women (n = 182; P = 0.005), whereas there was no seasonal pattern in men (P = 0.9). CONCLUSION: These findings, in conjunction with other data, suggest that diverse environmental agents, acting upon different immunogenetic backgrounds, result in distinct immune responses and clinical syndromes in the idiopathic inflammatory myopathies. Our results emphasize the importance of considering more homogeneous disease groups, based on clinicopathologic features, immune responses, ethnicity, and sex, when attempting to decipher the pathogeneses of autoimmune disorders.

Autoantibodies↗
PubMed2003

Seasonal variations in eating disorder subtypes in Japan.

OBJECTIVE: This study estimated the degree of seasonal changes in eating disorder subtypes in Japan. METHOD: A Japanese version of the Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to 228 outpatients with eating disorders in Kyoto (latitude 35 degrees 01' N). Ninety responses were analyzed. The mean of the global seasonality score (GSS) in the SPAQ and the comorbidity rate of seasonal affective disorder (SAD) and subsyndromal-SAD in each subtype were used as indices of seasonality. RESULTS: The mean (8.2) of the GSS of the bulimia nervosa (BN) group and the sum (43%) of the comorbidity rates of SAD and subsyndromal-SAD in the BN group were significantly higher than those in the nonclinical comparison group. DISCUSSION: The seasonality of BN in Kyoto is the highest among eating disorder subtypes, although lower than that in North America. This finding suggests that light therapy could be useful for Japanese BN patients.

Affect↗
PubMed2001

Unraveling the enigma: the role of melatonin in seasonal processes in birds.

Birds, unlike mammals, do not use the annual profile of pineal melatonin secretion to coordinate their reproductive efforts with a favorable time of year. Melatonin in birds mediates the entrainment of circadian activity rhythms, and thus helps to time hatching of eggs and facilitate migration. However, the role of melatonin as a reliable indicator of day length for seasonal processes has remained equivocal for many years. Recently, the influence of melatonin on two physiological processes involved in aspects of seasonal reproduction has been identified in European starlings: 1) the regulation of seasonal changes in immune function, and 2) neuroplasticity in the song control system. Melatonin can enhance cell-mediated immune function and acts as an inhibitory hormone on the song control system. Melatonin receptor (MelR) density in a forebrain song control nucleus, Area X, is regulated as a function of reproductive state; there is marked downregulation of MelR in Area X during the breeding season in starlings. Seasonal regulation of immune function and neural plasticity within the song control system, and the efficacy of the action of melatonin on these two processes, appears to be modified by the same central, thyroid-dependent mechanism that controls the reproductive state of birds. These data indicate that the interaction of day length and hormones of different classes affects the ability of melatonin to affect seasonal processes in birds. The downstream consequences of MelR regulation within the song control system are discussed with regard to the cellular action of melatonin and its possible interaction with immediate-early genes and transcription factors.

Animals↗
PubMed2001

Seasonal changes in the preferred body temperature, cardiovascular, and respiratory responses to hypoxia in the toad, Bufo paracnemis.

Estivation is accompanied by a reduction of oxygen consumption in amphibians during drought. We tested the hypothesis that, during the dry season, the toad Bufo paracnemis selects a lower preferred body temperature (T(b)), and would be less sensitive to hypoxia, than during its active period. Therefore, during winter (dry season in São Paulo state, Brazil) and summer, we measured the effects of hypoxia (7% inspired O(2)) on preferred T(b). Additionally, pulmonary ventilation, heart rate, blood pressure, and oxygen consumption were also measured in toads at 15 and 25 degrees C. Blood gases were measured at 25 degrees C. Oxygen consumption was significantly higher during summer in toads at 25 degrees C. Under normoxia, preferred T(b) was higher during summer than during winter, and hypoxia caused a drop in preferred T(b) during both seasons. In both seasons, toads at 15 degrees C showed reduced pulmonary ventilation, heart rate, and blood pressure, and hypoxia had no effect. At 25 degrees C during summer only, hypoxia caused an increase in ventilation. Season had no effect on blood gases. We conclude that B. paracnemis displays an endogenous seasonal pattern of thermoregulation and control of ventilation. The decreased preferred T(b) and the physiological responses to hypoxia may be beneficial to toads encountering drought and when food is not available.

Adaptation, Physiological↗
PubMed1992

Sex differences in adrenal function in the lizard Cnemidophorus sexlineatus: I. Seasonal variation in the field.

In order to document sex differences in adrenal function and how this relates to gonadal function during the period of seasonal activity, blood samples from male and female six-lined racerunners, Cnemidophorus sexlineatus, were taken immediately after capture in the field for determination of plasma corticosterone and gonadal steroid concentrations. Plasma testosterone and dihydrotestosterone levels for males, and 17 beta-estradiol and progesterone levels for females, were measured. Trends in the concentration of plasma corticosterone differed significantly between males and females. In males the highest concentrations of corticosterone were measured in late spring and the lowest concentrations were measured in late summer. Whereas half of the variation in corticosterone levels among males could be explained as seasonal change, less than 1% of the variation among females could be explained as seasonal change. In males plasma corticosterone and androgens exhibited similar seasonal decreases. Corticosterone levels for females were not correlated with progesterone or 17 beta-estradiol levels. Sex differences in seasonal variation in plasma corticosterone concentrations suggest that corticosterone may be involved in the different reproductive strategies and energy requirements of males and females during the seasonal period of activity.

Adrenal Glands↗
PubMed1995

External and internal influences on indices of physiological stress: II. Seasonal and size-related variations in blood composition in free-living lizards, Sceloporus occidentalis.

Seasonal changes in blood composition (plasma osmolality, total plasma protein, hematocrit) in two free-living populations of fence lizards, Sceloporus occidentalis, one living in a very arid environment (Pearblossom, CA) and another in a milder desert (Bend, OR), were analyzed. In this analysis, two features of reptilian physiology and ecology were incorporated: ontogenetic variation in blood composition and seasonal variation in body-size distribution. The population living in the arid environment, but not the mild environment, exhibited significant seasonal changes in blood composition: mean plasma osmolality increased (345 +/- 4 to 356 +/- 3 mOsmol/kg) and mean plasma protein (4.19 +/- 0.20 to 3.34 +/- 0.14 g/dl) and hematocrit decreased (43.8 +/- 0.3 to 31.6 +/- 0.4) from April to August. These changes suggested that the physiological condition of the California population was affected by seasonal changes in the external environment. However, among individuals, a significant portion of the variation in blood composition was associated with an internal factor, body size. Larger lizards had higher osmolality, total protein, and hematocrit than smaller lizards in all seasons. In addition, the mean body size of active lizards decreased from April to August in California, but not Oregon. Because the body-size distribution of active lizards in California shifted between seasons, changes in mean population values of these blood parameters probably do not accurately reflect changes that occur within individuals and therefore may be misleading in assessing the physiological consequences of drought.

Analysis of Variance↗
PubMed2004

Changes in the hemagglutinins and neuraminidases of human influenza B viruses isolated in Italy during the 2001-02, 2002-03, and 2003-04 seasons.

Throughout most of the last decade, B/Yamagata/16/88-lineage influenza viruses were predominant among the B isolates circulating worldwide, whereas B/Victoria/2/87-lineage viruses were isolated infrequently and restricted geographically to eastern Asia. During the 2001-02 influenza season, B/Victoria/2/87-lineage viruses re-emerged in North America and Europe and spread worldwide. Virological surveillance in Italy during that season showed wide circulation of influenza B viruses, of which most were antigenically related to the B/Sichuan/379/99 (Yamagata-lineage) vaccine strain, together with a smaller number of B viruses antigenically similar to B/HongKong/330/01, a recent B/Victoria/2/87-lineage antigenic variant. In the subsequent 2002-03 epidemic season, B viruses with a Victoria-lineage hemagglutinin (HA), more closely related to that of B/Shandong/7/97, were isolated exclusively. Similar strains have continued to predominate among the few B viruses isolated in Italy during last season (2003-04), although most influenza B viruses, isolated sporadically elsewhere in Europe, again belong to the Yamagata-lineage. In the present study, phylogenetic analyses of the HA and neuraminidase (NA) genes of representative B strains, isolated throughout Italy during 2001-04, showed that during the first influenza season the NA genes, as well as the HA genes, separated into the two distinct clades, the Yamagata- and Victoria-lineages, and showed no evidence of genetic reassortment. On the contrary, all the B viruses isolated in the 2002-03 and most of those isolated in the 2003-04 epidemic season were "Victoria HA-Yamagata NA" reassortants similar to those isolated in other parts of the world, showing that these reassortants became established in the human population. The frequency of reassortment between HA and NA of distinct lineages and sublineages highlights again the importance of detailed molecular analyses of both surface glycoproteins in understanding the evolution of influenza B viruses.

Genetic Variation↗
PubMed2003

Brain aromatase, 5 alpha-reductase, and 5 beta-reductase change seasonally in wild male song sparrows: relationship to aggressive and sexual behavior.

In many species, territoriality is expressed only during the breeding season, when plasma testosterone (T) is elevated. In contrast, in song sparrows (Melospiza melodia morphna), males are highly territorial during the breeding (spring) and nonbreeding (autumn) seasons, but not during molt (late summer). In autumn, plasma sex steroids are basal, and castration has no effect on aggression. However, inhibition of aromatase reduces nonbreeding aggression, suggesting that neural steroid metabolism may regulate aggressive behavior. In wild male song sparrows, we examined the neural distribution of aromatase mRNA and seasonal changes in the activities of aromatase, 5 alpha-, and 5 beta-reductase, enzymes that convert T to 17 beta-estradiol, 5 alpha-dihydrotestosterone (5 alpha-DHT, a potent androgen), or 5 beta-DHT (an inactive metabolite), respectively. Enzyme activities were measured in the diencephalon, ventromedial telencephalon (vmTEL, which includes avian amygdala), caudomedial neostriatum (NCM), and the hippocampus of birds captured during spring, molt, or autumn. Aromatase and 5 beta-reductase changed seasonally in a region-specific manner. Aromatase in the diencephalon was higher in spring than in molt and autumn, similar to seasonal changes in male sexual behavior. Aromatase activity in the vmTEL was high in both spring and autumn but significantly reduced at molt, similar to seasonal changes in aggression. 5 beta-Reductase was not elevated during molt, suggesting that low aggression during molt is not a result of increased inactivation of androgens. These data highlight the relevance of neural steroid metabolism to the expression of natural behaviors by free-living animals.

Aggression↗
PubMed1995

Seasonal changes in song nuclei and song behavior in Gambel's white-crowned sparrows.

In males of several songbird species, the morphology of forebrain nuclei that control song changes seasonally. The only seasonally breeding songbird in which seasonal changes in the structure of song control nuclei have been reported not to occur is the nonmigratory Nuttall's subspecies of white-crowned sparrow. In the present study, we manipulated photoperiod and plasma testosterone concentrations in captive male white-crowned sparrows of the migratory Gambel's subspecies. Males exposed to photoperiods and plasma testosterone concentrations typical of those experienced by wild breeding males had larger song control nuclei than males held on a winter photoperiod. We also found seasonal changes in stereotype of spectral and temporal parameters of song in wild Gambel's white-crowned sparrows. We hypothesize that seasonal changes in the song control nuclei may correlate with seasonal changes in song stereotypy.

Animals↗
PubMed2002

Seasonal dependency of the effects of rotational stress and cyclophosphamide in mice bearing lewis lung carcinoma.

The antitumor effects of cyclophosphamide were previously shown to be markedly reduced by the application of restraint stress in mice bearing Lewis lung carcinoma. The aim of this work was to determine the effects of rotational stress on the antitumor action of cyclophosphamide in the same animal-tumor system. Since the effects of rotational stress on metastasis were found to display a circannual rhythm, with a maximum in summer and a minimum in winter, the experiments were performed in June and February. Groups of 10 young female mice were kept under low stress housing conditions, with a 12-12 h light/dark cycle, starting 2 weeks before and during each experiment. Rotational stress caused an increase of metastasis volume to 361% of nonstressed controls in June and a decrease to 32.4% in February. In both seasons, the treatment with cyclophosphamide (240 mg/kg/day for 6 days) caused the absence of detectable metastasis at sacrifice in all mice; its combination with rotational stress caused the presence of metastases in similar proportions (6/10 and 10/10 for June vs February, respectively). The survival time of control mice was approximately twice as long in February as in June and was not appreciably modified by rotational stress; cyclophosphamide was similarly active in both seasons (4/10 and 6/10 long-term survivors for June vs February, respectively), and the number of long-term survivors was reduced to 0/10 in both seasons by rotational stress. The survival of the different experimental groups inversely correlated with the number of metastases as determined at sacrifice at the end of treatment and also with the number of CD3(+) and CD4(+) splenic T-lymphocyte subsets. These results do not appear to depend on the disruption of the circadian organization of the mice by rotational stress or by seasonal differences in cyclophosphamide activity. On the other hand, they can be interpreted assuming that cyclophosphamide reduces tumor metastasis and that T-lymphocyte-mediated immune responses of the host, amenable to modulation by stress and displaying seasonal differences uncoupled from circadian rhythms, further contribute to the tumor inhibitory effects of the drug. The observed differences in tumor metastasis caused by rotational stress and survival time in two different seasons, and the marked attenuation of cyclophosphamide antitumor action by rotational stress, appear of interest for their experimental and clinical implications.

Animals↗
PubMed1997

Plasma steroid profiles in nesting loggerhead turtles (Caretta caretta) in Queensland, Australia: relationship to nesting episode and season.

Plasma levels of four hormones-progesterone (P), testosterone (T), estradiol 17-beta (E2), and corticosterone (B)-were measured in samples taken from nesting female loggerhead turtles (Caretta caretta) by using specific radioimmunoassays. Samples were taken in an early, middle, or late period during the summer nesting season from females at first, second, third, or > fourth nesting episodes, defined as successive within-season nesting events, at Mon Repos Beach, Queensland, Australia. Data on individual patterns of nesting, collected over the past 20 years by the Queensland Turtle Research Project, and the seasonal nesting data, were analyzed with respect to influences on hormonal profiles. Circulating levels of E2 were mostly undetectable, suggesting either that this estrogen is not produced at this time of nesting, or that, perhaps, another estrogen may be present that is not detected by the specific radioimmunoassay. P, T, and B profiles in the nesting females were associated with the individual turtles' progression through successive nesting episodes, with a marked decline in all three hormones by the last (> 4) nesting episode of the season. Nesting episode accounted for significant changes that were related to season, in that nesting episode and season were significantly correlated. These patterns were observed in the population, when singly sampled at each time period or nesting episode, and in individual females sampled repeatedly over time. Moreover, T and B were highly and significantly correlated in females at all nesting episodes and time periods, and in the singly and repeatedly sampled females. The magnitude of change in T and B over time was also highly and significantly correlated in repeatedly sampled females. Together these results suggest the hypothesis that T and B interact over the period of successive nesting and may be involved in reproductive functions such as the mobilization of reserves for egg production in C. caretta.

Animals↗
PubMed2002

Seasonal differences in the hormonal control of territorial aggression in free-living European stonechats.

In birds, territorial aggression during the breeding season is regulated by testosterone (T). However, many bird species also express aggressive behavior during the nonbreeding season, when plasma levels of T are low. It has been suggested that during this period estrogens might play a major role in regulating territorial aggression. In the present study we compared the effects of simultaneous blockage of androgenic and estrogenic actions on territorial aggression during the breeding and nonbreeding seasons in free-living male European stonechats (Saxicola torquata rubicola). European stonechats are of particular interest since they establish territories and form pairs during both the breeding and the nonbreeding seasons. Thus territorial aggression and its endocrine control can be compared between reproductive and non-reproductive contexts. Inhibition of androgenic and estrogenic actions by simultaneous application of Flutamide and ATD reduced territorial aggression during the breeding season, but not during the nonbreeding season. Our results show that androgens and/or estrogens are involved in the endocrine control of territorial aggression in stonechats only in a reproductive context, but not in a non-reproductive one.

Aggression↗
PubMed2002

Seasonal variations in circadian rhythms of plasma melatonin in ruin lizards.

We examined melatonin profiles of ruin lizards in different seasons (spring, summer, and autumn) under light:dark (LD) and concomitant responses when transferred to continuous darkness (DD) to determine the degree to which previously reported seasonally dependent effects of pinealectomy on locomotor behavior are related to melatonin secretion. The amplitude of the melatonin rhythm and the amount of melatonin produced over 24 h varied with season. In spring, the amount of melatonin produced was greatest and the amplitude 4- 5 times that found in summer or autumn. The degree of self-sustainment of the melatonin rhythm when transferred to DD also varied with season. In DD, melatonin levels remained high but did not exhibit circadian variation in spring. In summer, the melatonin profile persisted virtually unchanged in DD, showing the existence of a circadian rhythm. Finally, in the fall there was no circadian variation in DD and levels remained low. These responses correspond closely to previously reported effects of pinealectomy on locomotor behavior where there is little or no effect of pinealectomy in spring or fall but a profound alteration of locomotor behavior in summer. These results suggest that the seasonally dependent effects of pinealectomy on locomotor behavior in ruin lizards are related to a seasonally mediated change in the degree of self-sustainment of some component of the circadian pace-making system of which melatonin plays some role.

Animals↗
PubMed2002

Restoring fire as an ecological process in shortgrass prairie ecosystems: initial effects of prescribed burning during the dormant and growing seasons.

Prior to Anglo-European settlement, fire was a major ecological process influencing the structure, composition and productivity of shortgrass prairie ecosystems on the Great Plains. However during the past 125 years, the frequency and extent of grassland fire has dramatically declined as a result of the systematic heavy grazing by large herds of domestic cattle and sheep which reduced the available levels of fine fuel and organized fire suppression efforts that succeeded in altering the natural fire regime. The greatly diminished role of recurrent fire in these ecosystems is thought to be responsible for ecologically adverse shifts in the composition, structure and diversity of these grasslands, leading specifically to the rise of ruderal species and invasion by less fire-tolerant species. The purpose of this study was to evaluate the ecological effects of fire season and frequency on the shortgrass prairie and to determine the means by which prescribed fire can best be restored in this ecosystem to provide the greatest benefit for numerous resource values. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry were measured prior to and following fire treatments on a buffalograss-blue grama shortgrass prairie in northeastern New Mexico. Dormant-season fire was followed by increases in grass cover, forb cover, species richness and concentrations of foliar P, K, Ca, Mg and Mn. Growing-season fire produced declines in the cover of buffalograss, graminoids and forbs and increases in litter cover and levels of foliar P, K, Ca and Mn. Although no changes in soil chemistry were observed, both fire treatments caused decreases in herbaceous production, with standing biomass resulting from growing-season fire approximately 600 kg/ha and dormant-season fire approximately 1200 kg/ha, compared with controls approximately 1800 kg/ha. The initial findings of this long-term experiment suggest that dormant-season burning may be the preferable method for restoring fire in shortgrass prairie ecosystems where fire has been excluded for a prolonged time period.

Agriculture↗
PubMed1984

HLA-related heterogeneity in seasonal patterns of diagnosis in Type 1 (insulin-dependent) diabetes.

HLA type, time of year of diagnosis, and age at diagnosis were studied in 52 new cases of Type 1 diabetes in Seattle, Washington. Diagnosis was found to be seasonal in diabetic patients positive for DR3 (p less than 0.005), with the expected marked reduction in new cases during the summer months. This seasonality was not age-related (p greater than 0.13). Cases who were DR3-negative did not show significant seasonality of diagnosis (p greater than 0.5). However, when age at diagnosis was adjusted for, a seasonal effect was found in the DR3-negative group (p less than 0.006), with older cases favouring a spring onset and younger cases favouring an autumn onset. Thus, DR3-positive cases showed a seasonal diagnosis pattern that did not depend on age, while DR3-negative cases showed an age-dependent seasonal pattern. These differences may reflect the predominance of different aetiological mechanisms in these two genetic groups.

Adolescent↗