Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SEASONS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2003

Effect of supplemental nutrition around lambing on hair sheep ewes and lambs during the dry and wet seasons in the U.S. Virgin Islands.

Pregnant St. Croix White and Barbados Blackbelly hair sheep ewes were used to evaluate the effect of supplemental nutrition around the time of lambing on ewe and lamb performance during the dry and wet seasons on St. Croix. Beginning 14 d before expected day of lambing (d 0) and for 21 d postpartum, one group of ewes was fed a pelleted supplement in addition to grazing guinea grass pasture (FEED). Other ewes in the flock grazed pasture only (CONTROL). This study was conducted during the dry season (June through September; FEED n = 14 and CONTROL n = 15) and during the wet season the next year (October through January; FEED n = 11 and CONTROL n = 12). The 24-h milk production of each ewe was measured on d 7, 21, 35, 49, and 63. Ewes were exposed to sterile rams equipped with marking harnesses to detect estrus during the postpartum period. The FEED ewes lost less weight postpartum during both seasons (P < 0.0001) and had higher milk production (P < 0.009) than CONTROL ewes during the dry season. During the dry season, the time to the first postpartum estrus did not differ (P > 0.10) between FEED and CONTROL ewes (46.9 +/- 2.7 vs 52.9 +/- 2.6 d, respectively). During the wet season, the time to first postpartum estrus was less (P < 0.07) in FEED than in CONTROL ewes (33.0 +/- 3.1 vs 41.1 +/- 2.9 d, respectively). The FEED ewes had higher lamb birth weight (P < 0.04) and weaning weight (P < 0.05) than CONTROL ewes (3.2 +/- 0.1 and 12.2 +/- 0.5 vs 2.9 +/- 0.1 and 10.9 +/- 0.5 kg, respectively) during the dry season. In the wet season, lamb birth weight and weaning weight were similar (P > 0.10) between FEED and CONTROL (3.2 +/- 0.1 and 15.5 +/- 0.7 vs 3.1 +/- 0.1 and 15.3 +/- 0.6 kg, respectively). Lambs born during the wet season had higher (P < 0.0001) ADG than lambs born during the dry season (194.4 +/- 5.9 vs 127.7 +/- 4.7 g/d, respectively). Strategic nutritional supplementation of hair sheep ewes may provide a method for increasing the weight of lambs produced during the dry season in the tropics, but it does not seem to be beneficial during the wet season.

Animal Feed↗
PubMed2006

Effects of breed and season on performance of lactating sows in a tropical humid climate.

A total of 179 lactations obtained on 71 multiparous sows [30 Creole (CR) and 41 Large White (LW)] between June 2001 and July 2004 were used to determine effects of breed (CR vs. LW) and season (hot vs. warm) in a tropical humid climate on performance during a 28-d lactation period. Mean daily ambient temperature was greater during the hot season than during the warm season (26.0 vs. 23.8 degrees C), and relative humidity was similar in both seasons (85% on average). For both breeds, ADFI was reduced (-700 g/d, P < 0.01), sow BW loss was greater (17 vs. 12 kg, P < 0.01), and piglet growth was reduced (197 vs. 210 g/d, P < 0.05) during the hot vs. the warm season. At farrowing, LW sows were heavier (255 vs. 186 kg, P < 0.01) and had less backfat (21 vs. 40 mm, P < 0.01) than CR sows. The growth rate of CR piglets was lower than that of LW piglets (192 vs. 215 g/d, P < 0.01). A breed x season interaction was observed (P < 0.05) for ADFI and sow BW loss. During the hot season, the reduction of ADFI was more pronounced in LW than in CR sows (-910 vs. -470 g/d). Regardless of the season, BW loss of CR sows remained constant (14.2 kg), whereas it increased during the hot season for LW sows (10 kg). The weaning-to-estrus and the weaning-to-conception intervals were not affected by breed or season and averaged 4.8 and 6.1 d, respectively. The rectal temperature was greater (0.3 degrees C) during the hot season than during the warm season and greater in LW than in CR sows (39.1 vs. 38.8 degrees C, P < 0.10). This study confirms the negative effect of hot season in a tropical humid climate on performance of lactating sows and that breed can have a significant effect on lactation performance. The results also suggest that CR sows are more heat tolerant than LW sows.

Animal Feed↗
PubMed1997

Seasonal affective disorder in Australia: is photoperiod critical?

OBJECTIVES: Seasonal affective disorder (SAD) is a variant of recurrent depression in which episodes are linked to a particular season, typically winter. SAD is understood as the extreme end of a continuum of seasonality in the general population. Photoperiod (the timing and duration of daylight) has been assumed to be aetiologically critical. The present research used a survey design to investigate the assumed centrality of photoperiod for SAD/seasonality in Australia. Two hypotheses were tested: that self-reported seasonality does not increase further from the equator and that seasonality does not stand alone from non-seasonal neurotic complaints. METHOD: The sampling frame used was adult females on the Australian Twin Registry roll. A sample of 526 women residing across the latitudes of Australia responded to a survey based around the Seasonal Pattern Assessment Questionnaire (SPAQ). The SPAQ asks respondents to retrospectively report on season-related changes in mood and behaviour. The survey also contained three questionnaire measures of neurotic symptoms of anxiety and depression: the General Health Questionnaire (GHQ), the Community Epidemiological Survey for Depression (CES-D) and the State-Trait Anxiety Inventory-Trait (STAI-T). RESULTS: Self-reported seasonality did not correlated with latitude (r = 0.01, NS). On the other hand, a substantial relationship was found between seasonality and each of the measures of non-seasonal complaints: GHQ (r = 0.35, p < 0.001); CES-D (r = 0.35, p < 0.001); and STAI-T (r = 0.30, p < 0.001). CONCLUSIONS: Within the limitations of a design based on retrospective self-report, the findings of the present study suggest that the diathesis for SAD/seasonality may not be photoperiod-specific. At least in Australia, there is provisional support for the proposal that human seasonality may have a broader psychological component. The findings are discussed in terms of established research into normal mood, trait personality and non-seasonal depression.

Adolescent↗
PubMed1998

Seasonal variation in agglutination of Plasmodium falciparum-infected erythrocytes.

Agglutination and rosette formation are in vitro characteristics of Plasmodium falciparum-infected erythrocytes, which have been associated with host protective immune responses and also with parasite virulence. The present study was carried out in an area of seasonal and unstable malaria transmission in eastern Sudan. Plasma samples were obtained before, during, and after the transmission season from a volunteer cohort of 64 individuals seven years of age and older. These plasmas were assayed for their ability to agglutinate cultured parasitized erythrocytes originally obtained from acute malaria infection samples taken from five of the cohort members. Our data show that the capacity of donor plasma samples to agglutinate parasitized cells depended largely on the time of sampling relative to the transmission season, at least within this epidemiologic setting. Thus, although less than half of the pretransmission season samples could agglutinate any of the five lines of cultured parasites, all post-transmission season samples could agglutinate at least one of the parasite lines, with 74% agglutinating two or more lines. This increase in the agglutination capacity of individual plasma samples after the transmission season occurred essentially regardless of whether an individual had experienced a clinical malaria attack during the transmission season. The study thus confirms the acquisition of agglutinating antibodies following episodes of clinical malaria, but also demonstrates that such acquisition can take place in the absence of disease, presumably as a consequence of subclinical infection. This is the first demonstration of marked seasonal fluctuations in the capacity of individuals' sera to agglutinate parasitized red blood cells. Possible explanations for this effect include a decrease in the levels of agglutinating antibodies between seasons, or shifts in the antigens being recognized by such antibodies from one transmission season to the next. Finally, we showed the existence of marked seasonal fluctuation in the levels of agglutinating antibodies, either because levels of such antibodies are not sustained between seasons or because the antigens recognized change from one season to the next.

Adolescent↗
PubMedDate not supplied

Seasonal effects on seminal quality, plasma hormone concentrations, and GnRH-induced LH response in fertile and subfertile stallions.

Seasonal effects on hormonal and seminal parameters in subfertile stallions have not been well documented and could provide information that is needed to understand the underlying endocrine mechanisms associated with testicular dysfunction. Such information may be useful in developing diagnostic tools to identify those stallions who are candidates for treatment. This investigation characterizes and compares the effects of season on endocrine function and seminal quality in fertile and subfertile stallions. Eight fertile and six subfertile stallions between the ages of 5 and 18 years were injected intravenously once every hour for 3 hours with either 1 mL saline on the first experimental day or 5 micrograms gonadotropin-releasing hormone in 1 mL saline on the second experimental day during the nonbreeding and breeding season. Heparinized blood samples were collected periodically through a jugular catheter before and after treatment for analysis of luteinizing hormone, follicle-stimulating hormone, testosterone, and estrogen conjugates by radioimmunoassay. Semen samples were collected twice, 1 hour apart, from all stallions in both seasons for analysis of volume, concentration, motility, pH, and morphology. A series of low intravenous doses (5 micrograms) of gonadotropin-releasing hormone induced a significant luteinizing hormone response (P less than 0.05) compared with saline treatment in both fertile and subfertile stallions. Fertile stallions had a twofold higher (P less than 0.05) net increase in plasma luteinizing hormone levels (peak levels minus baseline levels) in the breeding seasons than in the nonbreeding season. The magnitude of the luteinizing hormone response relative to baseline levels in fertile stallions, however, was one-and-one-half times greater (P less than 0.05) in the nonbreeding season than in the breeding season. In contrast, season did not have an effect on the net increase in plasma luteinizing hormone or the magnitude of the luteinizing hormone response relative to baseline levels in subfertile stallions. The net increase in plasma luteinizing hormone was similar between the two groups of stallions in both seasons. The magnitude of luteinizing hormone response relative to baseline levels, however, was lower (P less than 0.05) in subfertile stallions (141 +/- 14%) than in fertile stallions (235 +/- 46%) in the nonbreeding season; the two groups exhibited similar responses in the breeding season. Compared with fertile stallions, subfertile stallions had twofold to fourfold higher (P less than 0.05) plasma levels of gonadotropins and similar testosterone levels. The number of total progressively motile sperm was lower (P less than 0.05) in subfertile stallions in both seasons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

[Radiation characteristics in a tropical seasonal rain forest canopy gap].

Based on the observations in the radiation with different wavelengths in tropical seasonal rain forest canopy gap, interior of forest, and meteorological station in different seasons, the radiation characteristics of canopy gap were discussed. The results showed that the value of different wavelength radiation had the phenomenon of "suddenly emergent" at the center and north edge of canopy gap. Moreover, each radiation value reached the maximum rapidly, and then decreased quickly around the noon. The daily gross radiation of different wavelengths within the canopy gap was bigger than that in the interior of forest, but smaller than that at meteorological station. Compared to the north edge, the daily gross radiation in the center of the gap was bigger in dry-hot season, rain season and later rain season, but smaller in fog-cool season, which was influenced by dense fog, solar angle and azimuth. The total daily gross solar radiation at the center was the maximum when the solar angle was the biggest in rain season, higher in later rain season and dry-hot season, and was the minimum in fog-cool season. The ratios of infrared and visible light radiation to total solar radiation varied with the seasons at the center and north edge of the canopy gap, which fully indicated the environmental heterogeneity within the canopy gap. Compared with meteorological station and interior of forest, the ratios of infrared radiation to total solar radiation in the gap were bigger than those of meteorological station, but smaller than those of interior of forest, which were just contrary to the ratios of visible light to total solar radiation. In addition, the seasonal variation of the ratios of visible light to total solar radiation was higher than that of the ratios of infrared radiation to total solar radiation within the gap. Generally, canopy gap could increase infrared radiation and decrease visible light radiation in tropical seasonal rainforest.

Environment↗
PubMed1981

Control of seasonal reproduction in sheep and goats by light and hormones.

Seasonal variations of reproductive ability have been demonstrated in male and female sheep and goats. For the female, there is a distinct breeding season. Whilst there are large breed differences in the duration of the sexual season, oestrous cycles generally start when daylength is decreasing and end when daylength is increasing. In some breeds, ovulation without oestrus occurs during the non-breeding season. Although males are able to mate all the year round, seasonal variations occur in the weight of the testis and seminal vesicles and in the fructose concentration of the seminal vesicles. Sexual behaviour and semen characteristics also show seasonal variations. These seasonal variations in males and females are related to hormonal levels. FSH and LH concentrations in the pituitary are reduced to 50% during the non-breeding season. In the peripheral blood, LH concentrations vary throughout the year whilst prolactin concentrations follow the pattern of daylength. Steroid hormones and their feedback actions at the hypothalamo-pituitary axis play a role in the regulation of seasonal reproduction. Three different ways are proposed to overcome these seasonal variations. (1) Males can be introduced into a flock of females before the onset of the breeding season. This leads to induction of ovulation and oestrus, although the first ovulation is frequently followed by a short luteal phase. Teasing does not necessitate contact or sight and is only effective after a period of isolation of the females from the males. (2) Oestrus and ovulation may be induced during the anoestrous period by hormonal treatments. Inducers of LH release have to be associated with a progestagen treatment; PMSG is still the most efficient inducer of LH release. Artificial insemination is useful in this context to avoid subfertility due to seasonal variations of the male. (3) The period of reproduction may be controlled by artificial light regimens. There is a photoinducible period in the circadian cycle of the ewe and it may soon be practical to breed out of season by timed exposure of ewes to short periods of light during the normal hours of darkness.

Animals↗
PubMed1998

Seasonal variations in hospital admissions for affective disorders by gender and ethnicity.

Hospital admission statistics for depression and mania have shown significant seasonal patterns. The present investigation was conducted to establish the pervasiveness of the impact of seasons on mood disorder presentation at Birmingham (52 degrees North) by gender and ethnicity. Non-mood disorder admissions were examined as a control to determine the specificity of any seasonal variation to affective illness. Case notes for 992 admissions, during January-December 1995 inclusive, to an inpatient unit were reviewed retrospectively. Admission data were broken down by gender and into three ethnic groups: Asian, white and black. Seasonality in admissions for depression, bipolar disorder and non-mood disorders was tested by gender and ethnicity. Admission frequencies for depression showed significant seasonal pattern, with the incidence of depression being highest in winter. Total admissions, bipolar and non-mood disorders did not show any significant seasonal variability. A gender effect was evident on seasonality of admissions for affective illness, with significant winter peak for depression and summer peak for bipolar disorder in women only. The Asian group was the only ethnic group that showed significant seasonal variation in depression, with a greater number of depressive episodes in winter. Environmental variables were related significantly to the incidence of mood disorders. Specific seasonal effect for affective illness was evidenced by the non-existence of seasonality in other psychiatric disorders. The reverse seasonal pattern for depression and mania suggests a maladaptive response of vulnerable individuals to specific functions of seasons.

Adult↗
PubMed2006

Seasonality associated with the serotonin 2A receptor -1438 A/G polymorphism.

BACKGROUND: Seasonal affective disorder and seasonal rhythms in mood and behavior (seasonality) have been reported to be associated with serotonergic system. In this study we investigated the relationship between the serotonin 2A receptor (5HTR2A) -1438 A/G polymorphism and seasonal variation in a young Korean healthy population. METHODS: 297 young Korean medical students were recruited for this study. They were genotyped for the 5HTR2A -1438 A/G polymorphism and evaluated the seasonal variation in mood and behavior by the Seasonality Pattern Assessment Questionnaire (SPAQ). RESULTS: The Global Seasonality Score of the SPAQ among three genotypes were not different. However, the comparison between seasonals and non-seasonals showed significant difference in the genotype distribution. The winter-type seasonals showed a significantly higher frequency of the 5HTR2A -1438 A allele compared with non-seasonals (chi2 = 6.80, p = 0.009; OR = 1.79; 95% CI, 1.15-2.78). CONCLUSION: These results suggest that the 5HTR2A -1438 A/G polymorphism is possibly related to seasonality in the Korean population.

Adult↗
PubMed2004

Bronchial hyperreactivity and spirometric impairment in patients with seasonal allergic rhinitis.

UNLABELLED: We previously demonstrated in a group of patients with perennial allergic rhinitis alone, impairment of spirometric parameters and high percentage of bronchial hyperreactivity (BHR). Thus, the present study aimed at evaluating a group of subjects suffering from seasonal allergic rhinitis alone to investigate the presence of spirometric impairment and BHR both during and outside the pollen season. METHODS: One-hundred rhinitics sensitized to pollen allergens only were evaluated during and outside the pollen season. Spirometry and methacholine bronchial challenge were performed. RESULTS: Four rhinitics showed impaired values of FEV1 without referred symptoms of asthma during the pollen season. FEF 25-75 values were impaired in 17 rhinitics during the pollen season and in 11 rhinitics outside the pollen season (P<0.05). Fifty-four patients showed positive methacholine bronchial challenge both during and outside the pollen season. PD20/FEV1 methacholine was lower during the pollen season than outside (P<0.05). In BHR positive patients, reduced values of FVC (P<0.05), FEV1 (P<0.05), and FEF 25-75 (P<0.01) were significantly demonstrated in comparison with BHR negative rhinitics. There was a relationship between BHR degree and FEF 25-75 values only during the pollen season (P<0.001). CONCLUSIONS: This study evidences that an impairment of spirometric parameters may be observed also in patients with seasonal allergic rhinitis alone during the pollen season. A high percentage of these patients had BHR. A close relationship between upper and lower airways is confirmed also in the model of pollen allergy. Thus, a careful evaluation of lower airways should be performed also in those patients with seasonal allergic rhinitis alone.

Adult↗
PubMed2005

Analysis of seasonal variation of birth defects in Atlanta.

BACKGROUND: Compared with analyses of temporal trends, analyses of seasonal variations in the prevalence of birth defects have been more limited and have provided less consistent information. Possible reasons for this lack of consistency in findings include differences in populations, underlying factors, seasons or climates, and methods of ascertainment and analysis between studies. This study examines possible seasonal variation in the prevalence of selected birth defects in a defined study population using graphical displays and three statistical methods. METHODS: Cases were infants and fetal deaths in nine birth defect groups born to residents of mothers in five counties of metropolitan Atlanta during the period of 1978-2001 and ascertained by the Metropolitan Atlanta Congenital Defects Program. These birth defect groups were anencephaly, spina bifida, total neural tube defects, cleft palate, cleft lip with or without cleft palate, anomalies of the pulmonary valve, anomalies of the aortic valve, hypoplastic left heart syndrome, and congenital dislocation of the hip. We pooled monthly case counts and calculated monthly rates for each of these birth defect groups for five different birth periods: 1978-2001, 1978-1989, 1990-2001, 1990-1994, and 1995-2001. We applied the Cochran-Armitage test for trend to rule out homogeneity in pooled monthly rates. Data for each defect group were examined for possible seasonal (i.e., cyclical) variation overall and within the cited birth periods using the Hewitt-Rogerson test and the Walter-Elwood test. RESULTS: Graphical analyses of the pooled monthly rates showed no apparent seasonal patterns for any of the nine defect groups examined. Statistical tests for seasonality suggested possible seasonality for three defect groups: the Hewitt-Rogerson test was statistically significant for anencephaly (peak March-August, p = 0.048),while the Walter-Elwood test was significant for anomalies of the pulmonary valve (peak September, p = 0.02), and anomalies of the aortic valve (peak July, p = 0.039). With both methods, the results appeared to be influenced by the choice of time (i.e., birth) period. Results for anomalies of the pulmonary valve were statistically significant and more consistent with all tests in most of the time periods examined. CONCLUSIONS: Graphical analyses and basic statistical tests for seasonality showed no consistent evidence of seasonality for any of the nine defect groups examined, except for anomalies of the pulmonary valve. The two basic statistical methods coupled by a trend test for exploring seasonal patterns of the prevalence of birth defects can be useful for preliminary analyses of possible seasonal patterns. However, these methods have some limitations: (1) an assumption of no strong temporal trend over the study years, and (2) the results can vary by time period chosen. For specific hypotheses regarding seasonality, a more robust analytical approach such as time-series analysis might be more appropriate.

Anencephaly↗
PubMed1997

Seasonal changes in affective state in samples of Asian and white women.

Seasonality of the affective state has been reported to vary in direct proportion to latitude in temperate regions. The frequency of seasonal affective disorder (SAD) and the severity of the symptoms associated with it have been reported to be greater in higher than in lower latitudes. In addition, recent research has suggested a genetic loading for SAD. Most of the research on the seasonality of affect has been done in high latitude areas, seasonal mood cycles have been infrequently investigated in tropical areas, and no study has so far measured and compared seasonal changes in affect and behaviour in indigenous and populations non-indigenous to high latitudes. To rule out the biases associated with retrospective designs, a prospective longitudinal study was designed to investigate seasonal mood variations in indigenous white and non-indigenous Asian populations. Since previous research has indicated the excessive vulnerability of women to winter depression, it was decided to measure seasonality of the affective state only in women. To examine the relative effects of genetic predispositions and physical environment, the Asian group was further divided into "Asian" and "Asian-British". The former group comprised women who were living in England but who had been born and had spent considerably more time in their country of origin, while the latter group consisted of women who were born in England and who had lived there all their lives. The three groups of 25 women each were matched for age and socio-economic status, and were interviewed every month for 1 year using the Hospital Anxiety and Depression Scale (HAD), a Behavioural Change Inventory (BCI), the Ladder Scale of General Well-being (LSW) and a Monthly Stress Inventory (MSI). One retrospective scale was administered at the end of the study year to compare the extent of seasonal change in affect with that on the HAD-depression subscale. The results showed that seasonal depression peaked in winter in all three groups, with the incidence of winter depression being highest in the Asian group. Seasonal changes on several dimensions of behaviour were in the direction of winter depression for all three groups. States other than depression (anxiety and general well-being) did not show any seasonal variation. Hours of daylight was found to be the best predictor of seasonal variation in mood among environmental and psychosocial variables. There was no evidence to support a genetic hypothesis for SAD.

Adult↗
PubMed2005

Season effect on genitalia and epididymal sperm from Iberian red deer, roe deer and Cantabrian chamois.

Seasonality deeply affects the physiology and behavior of many species, and must be taken into account when biological resource banks (BRBs) are established. We have studied the effect of seasonality on many reproductive parameters of free-ranging Iberian red deer, roe deer and Cantabrian chamois, living in Spain. Testicles from hunted animals were collected and sent to our laboratory at different times during the year. We recorded the weight and volume of testis, the weight of the epididymis and its separate parts (caput, corpus, and cauda), the weight of the sperm sample collected from the cauda epididymis, and several sperm parameters (sperm concentration, spermatozoa recovered, motility, HOS test reactivity, acrosomal status, and viability). We studied the data according to several periods, defined accordingly to each species. For red deer, we defined rut (mid-September to mid-October), post-rut (mid-October to mid-December), and non-breeding season (February). For roe deer, they were pre-rut (June), rut (July), post-rut (first fortnight of August), and non-breeding season (September). For chamois: non-breeding season (June to mid-September) and breeding season (October-November). The rut/breeding season yielded significantly higher numbers for almost all parameters. However, in the case of red deer, sperm quality was higher in the post-rut. For roe deer, testicular weight was similar in the pre-rut and in the rut, and sperm quality did not differ significantly between these two periods, although we noticed higher values in the rut. In the case of chamois, sperm quality did not differ significantly from the breeding season, but data distribution suggested that in the non-breeding season there are less males with sperm of good quality. On the whole, we find these results of interest for BRB planning. The best season to collect sperm in this species would be the breeding season. However, post-rut in red deer, pre-rut in roe deer, and non-breeding season in chamois could be used too, because of the acceptable sperm quality, despite the lower quantity salvaged. More in-depth research needs to be carried out on the quality of sperm salvaged at different times of the year in order to confirm these findings.

Acrosome↗
PubMed2005

Seasonal pattern of bovine fasciolosis in the Kafue and Zambezi catchment areas of Zambia.

In order to establish seasonality of bovine fasciolosis in the Southern province of Zambia, 288 cattle were examined at slaughter at Turnpike slaughter slab for 1 year. The examination involved liver inspection and coprological examination. Liver condemnation rates were relatively high at the beginning of both the cold dry season and the rainy season (May/June and December, respectively). All cattle, regardless of age, had higher fluke abundances in the post-rainy season (39.1% young and 42.1% adult) while the lowest rates were in the hot dry season (13.3% young and 14.3% adult). On coprological examination, the highest abundance was in the post-rainy season (45.0%) and the lowest in the cold dry season (24.9%). From November (end of dry season) to February/March (end of rains), more fluke eggs were found than in any other period. The distribution of fluke eggs was significantly different (p<0.001) among the four seasons. Identified associations were: egg counts were highest in post-rainy (mean abundance=146) and lowest in cold dry season (mean abundance=118) at 95% confidence (CI 0.64-1.25). Differences in abundance observed according to origin, sex and age of cattle were not significant on both methods. Based on these results, it may be concluded that Fasciola gigantica was present throughout the year in cattle in Zambia but the abundance was highest in the post-rainy season and lowest in the cold dry season.

Age Factors↗
PubMed2003

Reproductive season affects inhibitory effects from large follicles on the response to superovulatory FSH treatments in ewes.

The main objective of this study was to compare the effect of the presence of large follicles at the start of FSH treatment on the superovulatory response in ewes in the breeding and nonbreeding seasons. A second objective was to verify the effect on the superovulatory response of the presence of a corpus luteum at the start of the FSH treatment during the breeding season. Fifteen ewes in breeding season (October) and 14 in nonbreeding season (May-June) were treated with 40 mg FGA sponges (Chronogest) for 14 days, together with a single dose of 125 microg cloprostenol on Day 12, considering Day 0 as day of progestagen insertion. Superovulatory treatments consisted of eight decreasing doses (1.5 ml x 3, 1.25 ml x 2 and 1 ml x 3) of Ovagen twice daily from 60 h before to 24h after sponge removal. Ovarian structures were assessed by transrectal ultrasonography using a 7.5 MHz linear array probe. Luteal activity at progestagen insertion (Day 0) and presence of corpus luteum and of large follicles at first FSH dose (Day 12) were determined. There were no significant differences between the breeding season and nonbreeding season for ovulation rate (11.6+/-1.4 versus 11.6+/-1.3), number of recovered embryos (8.0+/-1.1 versus 9.6+/-1.3) or number of viable embryos (7.2+/-1.1 versus 5.8+/-1.2). During the breeding season, there were fewer recovered embryos in ewes with a large follicle (> or =6mm) at first FSH dose (6.9+/-1.1 versus 12.3+/-1.8, P<0.05) and fewer viable embryos (5.0+/-1.2 versus 10.5+/-0.5, P<0.05) than in ewes without such a follicle. During the nonbreeding season, however, there were no significant differences between ewes with or without a large follicle for either recovered (9.0+/-2.5 versus 11.3+/-1.2) or viable embryos (6.3+/-2.3 versus 8.1+/-1.2). Analysis of seasonal differences in ewes with a large follicle showed a lower number of recovered embryos in the breeding season (P<0.05) due to a lower recovery rate (65.7% versus 92.3%, P<0.05), since mean number of corpora lutea in response to the FSH treatment was similar (10.9+/-1.3 versus 10.0+/-2.5). These results indicate that, in sheep, the inhibitory effects of large follicles during the nonbreeding season are not as obvious as during the breeding season.

Animals↗
PubMed2003

Sex differences in cortisol secretion after administration of an ACTH analogue in sheep during the breeding and non-breeding season.

The aim of this study was to compare the response of cortisol in sheep of different sex and gonadal status to adrenal cortex stimulation by an ACTH analogue in the breeding and non-breeding season. Twenty-four adult Corriedale sheep were used in the non-breeding season, and 19 in the breeding season. Three weeks prior to the first trial (non-breeding season), six rams and six ewes were gonadectomised. In each trial, blood was obtained every 15min for 9h and the animals received 0.5mg of ACTH (Tetracosactid, Synacthen Depot i.m., after 1.5h of sampling. Sampling began at 10:00a.m. in the non-breeding season and at 9:00a.m. in the breeding season. Three main effects (sex, gonadal status and season) were evaluated, each with two levels (male and female, intact and gonadectomised, breeding and non-breeding season, respectively). In both seasons, the females showed higher cortisol levels after ACTH than males (P<0.001), though the difference seemed less marked in the non-breeding season. The cortisol response in the ewes was not affected by season. The rams, however, showed a lower response in the breeding season (P<0.03). Gonadectomy reduced the response in the ewes (P<0.001) but had no effect in the rams. Nevertheless, gonadectomy also eliminated the differences between the ewes and the rams, such that the intact rams had lower levels of cortisol compared to the intact females, with those of the gonadectomised animals of both sexes being intermediate between the gonad-intact groups. The results of this study confirm sex differences in ACTH induced cortisol secretion in intact sheep in vivo. Furthermore, by applying exogenous ACTH we have directly stimulated the adrenal cortex, indicating the existence of sex differences also at this level. The circulating gonadal steroids, which are responsible at least in part for the sex differences in the responses to stress, may influence cortisol secretion from the adrenal gland by direct action at the cortex.

Adrenal Cortex↗
PubMed2001

Seasonal regulation of membrane and intracellular corticosteroid receptors in the house sparrow brain.

A number of studies have demonstrated seasonal regulation of the adrenocortical response to stress, or of corticosteroid binding globulins, but very few studies have examined seasonal regulation of corticosteroid receptor levels. As a result, there have been few attempts to produce an integrated picture of seasonal plasticity of the stress response. We measured baseline and stress-induced corticosterone (CORT), corticosteroid binding globulin and neuronal cytosolic and membrane corticosteroid receptor levels in male and female, wild-caught house sparrows (Passer domesticus) during three different seasons over the annual cycle (nesting, molting and winter). We identified three neuronal corticosteroid receptors in the house sparrow brain: two intracellular receptors and one membrane-associated receptor. Little is known about corticosteroid receptors in neuronal membranes of avian and mammalian species, but we found that the levels of membrane corticosteroid receptors varied seasonally, being lowest during the nesting season. Cytosolic corticosteroid receptor numbers (both low and high affinity receptors) also varied seasonally. In contrast to the membrane bound receptors, however, the numbers of low and high affinity cytosolic receptors were lowest during winter. In addition, mean levels of total basal and stress-induced CORT in the plasma varied seasonally. Both basal and stress-induced levels of total CORT were significantly higher during nesting than during winter or molt. Finally, corticosteroid binding globulin levels in plasma were also seasonally regulated, in a pattern similar to total CORT, so that estimated free CORT levels did not vary between seasons. These data indicate that multiple components of the stress response are seasonally regulated in birds obtained from wild populations. Interactions between these regulated components provide a basis for seasonal differences in behavioural and physiological responses to stress.

Animals↗
PubMed1997

Serum level of soluble interleukin-2 receptor in patients with seasonal allergic rhinitis.

The rate of release of the soluble form of interleukin-2 receptor (soluble IL-2R) reflects T cell activation in vivo. Since T lymphocytes play a central role in respiratory allergic disorders, the measurement of serum levels of soluble IL-2R may be useful in analysing the disease state of allergic disorders. The study has aimed at investigating the seasonal changes in serum soluble IL-2R in 81 patients with seasonal allergic rhinitis due to Japanese cedar pollens, with special reference to the effect of anti-allergic pharmacotherapy and immunotherapy. Serum samples were obtained twice from each patient, before and during the pollen season, and all the serum samples were simultaneously used for determination of soluble IL-2R and cedar pollen-specific immunoglobin E (IgE). Seasonal elevation in soluble IL-2R was not associated with the good clinical outcome but was associated with the poor clinical outcome, irrespective of pharmacotherapy or immunotherapy. Additionally, successful immunotherapy suppressed seasonal elevation of serum soluble IL-2R more strongly than successful pharmacotherapy, and seasonal increase rates in soluble IL-2R were inversely correlated with the duration of immunotherapy. Seasonal increase rates in soluble IL-2R were significantly correlated with seasonal increase rates in specific IgE in both the medication group and the immunotherapy patients. These results may suggest that seasonal changes in serum soluble IL-2R may serve as an indicator for clinical outcome of seasonal allergic rhinitis, that the magnitude of T cell activation could affect specific IgE production, and that T cell activation could be gradually modulated as immunotherapy proceeds. In conclusion, seasonal changes in serum soluble IL-2R may serve as an objective indicator for clinical outcome of seasonal allergic rhinitis.

Adolescent↗