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At least 1,387 records · Page 77Linked to original sources
PubMed2005

Is period gene causally involved in the photoperiodic regulation of reproductive diapause in the linden bug, Pyrrhocoris apterus?

Earlier experiments demonstrated a strong up-regulation of per mRNA in wild-type (Wt) females of Pyrrhocoris apterus reared under diapause-inducing short days, while per mRNA levels were low in females of two non-diapause mutant strains (Nd), irrespective of photoperiod. In the present study, different sequences of per DNA in two strains of geographically different origin enabled us to analyse genetic linkage between the per gene and the Nd phenotype. Crosses between Wt females originating from C. Budejovice (Czech Republic) and Nd males originating from Lyon (France) resulted in F(2) progeny where 411 females entered diapause under short days and 120 females were reproducing. Thus, the segregation was very close to the 3:1 ratio in favour of diapause females, suggesting that the Nd trait behaves as a single autosomal recessive. Analysis of DNA in 20 females of the F(2) progeny revealed that their phenotype was not linked to the per genotype. We conclude that the per gene is not primarily responsible for the block to diapause photoresponsiveness in Nd mutants and its role, if any, is downstream from other gene(s) controlling diapause. This is the first attempt at genetic linkage analysis between a bona fide circadian clock gene and photoperiodism in a "non-drosophilid" species.

Animals↗
PubMed2006

Inelastic neutron scattering spectrum of Cs2[B12H12]: reproduction of its solid-state vibrational spectrum by periodic DFT.

The inelastic neutron scattering (INS) spectrum of polycrystalline Cs2[B12H12] is assigned through 1200 cm(-1) on the basis of aqueous and solid-state Raman/IR measurements and normal mode analyses from solid-state density functional theory. The Cs+ cations are responsible for frequency shifts of the internal cage vibrational modes and I(h) cage mode splittings due to the crystal T(h) site symmetry. These changes to the [B12H12]2- molecular modes make isolated-molecule calculations inadequate for use in complete assignments. Solid-state calculations reveal that 30/40 cm(-1) shifts of Tg/Hg molecular modes are responsible for structure in the INS spectrum unobserved by optical methods or in aqueous solutions.

Journal Article↗
PubMed2003

The effects of the periodical use of in-feed chlortetracycline on the reproductive performance of gilts and sows of a commercial pig farm with a history of clinical and subclinical viral and bacterial infections.

The objective of this study was to assess the effects of in-feed chlortetracycline (CTC) as a measure of preventing or minimizing infectious problems of reproductive failure in gilts and sows. In a farm of 400 Large White x Landrace gilts and sows with a clinical history of porcine respiratory and reproductive syndrome (PRRS) virus, the animals were treated with CTC. Treatment consisted of 10 g CTC sow/day for 15 days every 3 months. It improved the health status of sows by decreasing post-farrowing clinical mastitis and vaginal discharges, abortions, return-to-oestrus and irregular return-to-oestrus rates. These beneficial effects had a positive impact on the performance of the litter. More piglets were born live and weaned. These positive effects improved with repeated use of CTC. The serological evidence of PRRS virus, Leptospira spp. and Chlamydia spp. and the subsequent beneficial use of the antimicrobial agent indicate that reproductive failure, possibly resulting from the bacterial agents can be controlled with in-feed use of broad spectrum antimicrobials.

Abortion, Veterinary↗
PubMed1992

Metabolic and reproductive hormones during lactation and the post-weaning period in sows.

There is a great variation in body weight loss during lactation among primiparous sows fed a standard diet that is adjusted based on the number of piglets nursed and the maintenance requirements. Energy and protein catabolism is more pronounced during the first 1 to 3 weeks of lactation and sows with low weight loss recover earlier from their negative energy balance during lactation than sows with high weight loss. Using continuous blood collection a decrease in plasma levels of oxytocin, prolactin, and insulin, and an increase in plasma levels and no of LH pulses during lactation were demonstrated. Prolactin levels gradually increased in response to each suckling while only 40-50% of recorded sucklings induced a significant rise in plasma oxytocin. Following a 24-h fast during lactation, levels of prolactin were very low but increased rapidly after refeeding. Even plasma levels of insulin and glucose decreased to very low levels during fasting, but the release of LH was similar before and after refeeding. Weaning resulted in decrease in plasma levels of prolactin and increase in plasma levels and no. of LH pulses. Plasma levels of cortisol showed a diurnal pattern of change which disappeared on the day of weaning. In response to weaning plasma levels of glucagon and gastrin decreased, whereas insulin and somatostatin increased. At weaning sows with low weight loss during lactation had higher plasma insulin and lower plasma cortisol levels than sows with high weight loss, but no differences in levels or no. of LH pulses were observed between the two groups of sows.

Animals↗
PubMed1985

Seasonal changes in the concentrations of plasma gonadotropins and prolactin in wild mallard drakes.

Seasonal changes in the concentrations of plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin were measured in serial samples taken from seven captive wild mallard drakes exposed to natural lighting and temperature in Kiel, West Germany (54 degrees N), for 20 months. The seasonal pattern of plasma LH levels was characterized by high titers during the reproductive phase in the spring, a steep decrease toward the end of this phase (May/June), low levels during the summer, and a second annual peak in the fall. Plasma FSH levels increased during February and March, the period of rapid testicular growth, and reached the highest values at the end of March/beginning of April. Later in the spring FSH levels decreased and remained low for the rest of the year. The concentrations of plasma prolactin increased progressively during April and May, reaching their highest values at the end of the breeding season, coinciding with the steep fall in the levels of plasma gonadotropins. Prolactin concentrations fell during July and August and were at their lowest level in the autumn. It is concluded that the development of photorefractoriness is associated with an increase in the concentrations of plasma prolactin.

Animals↗
PubMed1982

Geographic variation in Peromyscus leucopus: short-day induced reproductive regression and spontaneous recrudescence.

In order to determine if intraspecific differences exist in the photoperiodic control of the reproductive cycle of white-footed mice (peromyscus leucopus), 34 male and 60 female mice from either Connecticut (CT), Virginia (VA), or Georgia (GA) laboratory stocks were exposed to either a long (16L:8D) or short (9L:15D) photoperiod for up to 27 weeks. Reproductive status (testis length or the presence of a perforate vagina) of these mice was assessed every 1 to 2 weeks. After this time, the males were killed and testis length, testes weight, and seminal vesicle weight determined. Testis length in mice from CT and VA began to decrease after Week 5 of short-day exposure and reached a minimum at Week 13; this effect was less pronounced in the VA mice. Little change occurred in the GA short-day mice and in the three groups exposed to long photoperiods. Spontaneous gonadal recrudescence began after Week 17 in CT males and Week 15 in VA males, but was not yet complete at the end of Week 27. Similar results were obtained with the females. These results show that genetic differences exist in both the degree and duration of reproductive quiescence in this species.

Animals↗
PubMed1998

Endometrial cytology of the normal bitch throughout the reproductive cycle.

Samples for endometrial cytology were collected both from live bitches using transcervical uterine cannulation (n = 48) and postmortem (n = 10). The cells identified were endometrial epithelial cells, leucocytes, erythrocytes, spermatozoa, bacteria and cervical or vaginal cells. The endometrial epithelial cells varied morphologically throughout the reproductive cycle and had signs of degeneration during late dioestrus and during early and mid-anoestrus following dioestrus and postpartum. Neutrophils were the most common leucocytes observed during pro-oestrus, oestrus, dioestrus and early pregnancy, and lymphocytes during anoestrus. Macrophages were frequently seen during anoestrus. Erythrocytes were found in variable numbers at all stages of the reproductive cycle. Spermatozoa were detected in samples collected during oestrus and early pregnancy in bitches which had their last mating one to three days previously. Bacteria were commonly observed during pro-oestrus and oestrus. Cornified cervical or vaginal cells were present during pro-oestrus and oestrus. This study demonstrated that the numbers, types, proportions and morphology of cells in endometrial cytological samples from normal bitches varied throughout the reproductive cycle.

Animals↗
PubMed2001

Application of progesterone measurement for age and body weight at puberty, and postpartum anestrus in Korean native cattle.

Studies were conducted in Korean native cattle to determine the age and body weight at puberty, and to determine the postpartum anestrus intervals based on plasma progesterone profiles, rectal palpation, ultrasonography and estrus observation. Korean native cattle reached puberty at 344 days of age and at 188 kg body weight as determined by plasma progesterone profiles, but estrous behavior was not detected until 3 months later, at a body weight of 215 kg. Prolonged postpartum anestrus occurred in 40% of smallholders cows, where animals were tethered and fed hay and rice straw, whereas its incidence was only 6.8% in a well managed herd that was grazed and housed. Plasma progesterone profiles were used to monitor ovarian activity postpartum in standard fed cows (n=44) and restricted fed cows (n=20). In standard fed cows 81.8% showed luteal activity by 50 days postpartum, compared to 55% in restricted fed cows. Approximately 40% of cows in both groups had shown observable estrous behavior by this time. This study indicates that one or more ovulations had occurred before pubertal heifers and postpartum cows showed overt estrous behavior. It was concluded that improved management and feeding practices should result in improved reproductive performance.

Age Factors↗
PubMed2004

Postpartum ovarian follicular dynamics and estrous activity in lactating dairy cows.

The objectives of this study were to characterize early postpartum follicular dynamics in dairy cows in relation to their estrual activity and subsequent reproductive performance using 50 (26 primiparous and 24 multiparous) lactating Holstein cows. Ovaries and uterine horns of postpartum lactating cows were examined by ultrasonography 3 times weekly and continued until first services occurred after a 45-d voluntary waiting period. No differences were detected in fertility between primiparous and multiparous cows. In 40 of 50 cows, first postpartum ovulation was observed within 4 follicular waves, and the follicular wave patterns and ovarian cycles in most cows returned to normal as in cattle having normal estrous cycles after the second postpartum ovulation. Cows with the longest intervals from calving to first ovulation produced the most milk and also had prolonged intervals to first estrous activity. Differences in follicular dynamics before first ovulation altered intervals to first estrus, first service, and uterine involution, but these differences did not affect pregnancy rate, number of services, and days open. First postpartum insemination after 3 follicular waves tended to have greater pregnancy rates than those after 2 follicular waves. First inseminations at first estrus could produce greater pregnancy rates than those at subsequent periods of estrus.

Animals↗
PubMed1983

Effects of various forage feeding programs during dry period on body condition and subsequent lactation health, production, and reproduction.

During 3 yr, 289 Holstein cows prior to being dried off were assigned randomly to one of three diets: all long hay, 50% hay and 50% corn silage, and limit-fed corn silage plus 1.1 kg liquid protein supplement added per cow per day. Body weights, condition scores, and calving difficulties were recorded. Calf weights were recorded at birth. All cows were distributed across eight postpartum experiments. Body condition was similar for all cows at termination of dry period. Cows fed limited corn silage plus liquid supplement gave birth to heavier calves and had greater calving difficulty. Diet for dry period had little effect on health in the subsequent lactation. Cows fed long hay while dry consumed more dry matter, produced more milk with lower milk fat percent, and were not different for 4% fat-corrected milk compared to cows fed the other two diets in dry period. Days open were greater for cows fed long hay while dry. In general, as long as the ration is nutritionally balanced and fed in amounts to achieve or maintain adequate body condition, forage programs ranging from all hay to all corn silage can be fed successfully during the dry period.

Animals↗
PubMed2002

Temporal fluctuation and reproduction of Thermocyclops decipiens (Copepoda, Cyclopoida) in an eutrophic lake of central Brazil.

Lake Paranoá is an eutrophic reservoir situated in the urban region of Brasília. This study was carried out in a fixed collection station located in the Riacho Fundo branch of the reservoir. Zooplankton samples were collected at intervals of 3-5 d at 9:00 a.m. during two months in the dry and rainy seasons for two years (dry-1996, rainy-1997, dry-1997 and rainy-1998), using a 64 microns-mesh plankton net. The most predominant species was Thermocyclops decipiens (about 50% of the total zooplankton community), which during the whole period had a high reproductive rate. The highest densities were found in the dry-1996 season (1700 ind/l for nauplii), and also fluctuated widely overtime. Nauplii stages dominated during the four periods, comprising 50-75% of the total population density. Ovigerous females peaked in the dry-1996 and rainy-1997 seasons, with 20-30% of the total females. The largest peak in egg production occurred during the dry-1996 season, and the total egg production was 2.0 x 10(3) eggs/l. Mesocyclops longisetus is a first record for Lake Paranoá. The ecological factors that determine the success of T. decipiens in eutrophic systems are related to omnivorous feeding habits and prey-predator interactions.

Animals↗
PubMed1982

Photoperiod and reproduction in female deer mice.

Female deer mice were exposed to a short day (SD, 6L:18D) photoperiod beginning during 1 of 3 stages of life. In the first experiment, exposure to SD during adulthood resulted in a minimal disruption of reproductive condition; many females bore 2 litters after the onset of this treatment. In the second experiment, females reared on SD from weaning matured normally, as measured by vaginal introitus; however, vaginal closure occurred in approximately one-half of these females by 9 weeks of age. In the third experiment, females were born of mothers housed on either an SD or a long day photoperiod, and were continued on the maternal photoperiod until 6 weeks of postnatal age. The SD photoperiod markedly inhibited reproductive maturation as measured by vaginal patency, ovarian weight, and uterine weight. A comparison of reproductive organ weights and vaginal condition provided evidence for the validity of the latter measure as an index of reproductive state. As assayed by the present testing procedure, the sensitivity of the reproductive system to photoperiod decreases as a function of age in female deer mice.

Animals↗