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At least 685 records · Page 38Linked to original sources
PubMed1979

Toxoplasma gondii-vertebrate cell interactions. II. The intracellular reproductive phase.

The reproduction of Toxoplasma gondii RH-strain in vertebrate cells was studied in a controlled-environment culture system. The lag period before reproduction and the doubling time of individual parasites were determined using a least-squares linear regression method of analysis which does not artificially constrain the data. In the majority of cases, the time intercept of the linear regression line was either zero, implying the lack of a lag phase before reproduction, or negative, implying the parasite had completed part of its reproductive cycle before entering the host cell. The mean doubling time of T. gondii is 10.9 h in bovine embryo skeletal muscle cells and 8.3 h in HeLa cells. This difference is not significant at the 5% level. The population doubling times of mouse-derived parasites is best described by a gamma distribution.

Animals↗
PubMed1985

Path analysis of dry period nutrition, postpartum metabolic and reproductive disorders, and mastitis in Holstein cows.

Path analysis and logistic regression were used to model direct and indirect relationships among clinical periparturient (within 30 d after calving) retained placenta, metritis, veterinary-assisted dystocia, uncomplicated and complicated ketosis, left displaced abomasum, parturient paresis, mastitis, and estimated nutrient intakes (protein, calcium, phosphorus, energy; coded into terciles) in the last 3 wk of the dry period. Data were from 1,374 multiparous Holstein lactations for calvings from March 1981 through February 1982 in 31 commercial herds in central New York. Periparturient disorders occurred as a complex. Odds ratios for the multiplicative effects of parturient paresis on incidence of veterinary-assisted dystocia, retained placenta, complicated ketosis, and clinical mastitis were 7.2, 4.0, 23.6, and 5.4, respectively. Reproductive disorders were interrelated. Retained placenta, left displaced abomasum, and parturient paresis directly increased risk of complicated ketosis (odds ratios were 16.4, 53.5, and 23.6, respectively). Higher terciles of estimated energy intake in the last 3 wk of the dry period decreased risk of veterinary-assisted dystocia and left displaced abomasum, while higher terciles of estimated protein intake decreased risk of retained placenta and uncomplicated ketosis. Estimated nutrient intakes were directly related to subsequent metabolic disorders and directly and indirectly related (mediated by metabolic disorders) to reproductive disorders. The study suggests that feeding higher intakes (relative to National Research Council recommendations) of protein and energy in the last 3 week of the dry period may reduce the incidence of metabolic and reproductive disorders. Exact recommendations as to the amounts and types of feed cannot be made from our results.

Animal Nutritional Physiological Phenomena↗
PubMed1984

Determination of fertility interval with ovulation time estimation using differential skin surface temperature (DST) measurement.

Temperature distributions over the breasts of five healthy, young female volunteers using non-pharmaceutical contraceptives were studied over a menstrual cycle to identify "dynamic" temperature points related to E2-induced vascularity and "static" temperature points reflecting the body's core temperature. Corresponding thermometric measurements were analyzed. It was shown during a preliminary study that the DST between a "dynamic" and "static" point, so located, provides advance information on ovulation timing independent of physiologic disturbances and circadian and ambient temperature changes.

Adult↗
PubMed2005

Strategies for improving fertility in the modern dairy cow.

The high producing dairy cow of the 21st century is subfertile during lactation. Our objectives are to characterize physiological periods limiting reproductive performance and to describe integrated management strategies to improve pregnancy rates. Ovarian recrudescence with normal re-occurring estrous cycles and restoration of fertility to first service are associated with a reduced occurrence of periparturient metabolic and reproductive disorders. Marked negative changes in energy balance and reduced immunocompetence influence gonadotropic and metabolic hormones. Induced ovarian inactivity was associated with enhanced uterine involution. Post-partum health and reproductive performance were improved when by-pass lipids enriched in polyunsaturated fatty acids were fed in the pre- and post-partum periods. Pharmaceutical control of follicle, CL, and uterine function with PGF, GnRH and intravaginal progesterone releasing inserts, has permitted development of more optimal timed-insemination programs for first service. Likewise, resynchronization of nonpregnant cows coupled with the use of ultrasound for early pregnancy diagnosis provides the opportunity for a second timed-insemination within 3 days of a nonpregnant diagnosis. Bovine somatotropin (bST) increases embryo development and embryo survival when coupled with a timed-insemination program or cows detected in estrus. Presence of a conceptus alters endometrial expression of genes and proteins in response to bST and nutraceuticals (i.e., unsaturated fatty acids such as eicosapentaenoic and docosahexaenoic acid in by-pass lipids) to improve pregnancy rates. Postovulatory increases in progesterone may enhance pregnancy rates in targeted populations of lactating dairy cows, but timing and magnitude of the progesterone increases are pharmaceutically dependent.

Animals↗
PubMed1997

The R40H mutation in a late onset type of human ornithine transcarbamylase deficiency in male patients.

Ornithine transcarbamylase (OTC) deficiency is an X-linked trait and is one of the most frequent of the inherited urea cycle enzyme deficiencies. Most male patients with OTC deficiency develop a hyperammonemic crisis and die in the neonatal period or in early infancy. In contrast to those patients, in some male patients the disease first becomes overt in adolescence or during the reproductive age period. In the present report, we describe six such male patients who first developed clinical signs at ages ranging from 6 to 58 years, all of whom came from a limited area of the northern part of Kyushu Island in southern Japan. The mutation analysis disclosed a R40H mutation in exon 2 of the OTC gene in each of these patients. Transmission of this mutant gene through paternal lineage as well as through maternal lineage was documented in one family. The levels of mRNA of the mutant OTC gene expressed in transfected Cos 1 cells and in the liver tissue obtained by biopsy in one patient were both similar to those of the wild-type gene. The activity of the mutant OTC was, however, decreased to a level of 28% of the wild-type OTC, and the levels of the mutant OTC protein expressed in Cos 1 cells were decreased, as assessed by western blot analysis. Apparent Km values of the mutant enzyme for ornithine (1.1 mM) and carbamylophosphate (2.0 mM) were similar to those of the wild-type enzyme. Both enzymes gave similar pH-dependency profiles, giving a maximal activity at pH 7.8-7.9. Activity of wild-type OTC expressed in Cos 1 cells did not change after five cycles of freezing and thawing, whereas that of the mutant OTC decreased to 17% by this treatment. These results suggest that deficiency is due to inactivation of the mutant OTC under certain conditions.

Adolescent↗
PubMedDate not supplied

Metabolism during delayed hatching in terrestrial eggs of a marine fish, the grunion Leuresthes tenuis.

California grunion, Leuresthes tenuis (Osteichthyes: Atherinidae), leave the ocean to spawn in the sand following extreme high tides in summer. Eggs develop out of water and are able to hatch within 9-13 d, the primary hatching period. Eggs hatch on immersion and agitation by waves at the next extreme high-tide series. However, if the waves do not reach them and hatching is not induced, eggs remain viable in the sand for several weeks. During this period, grunion eggs will delay hatching, but will hatch at any time if immersed and agitated in seawater. Egg metabolism during embryonic development was measured by aerial respirometry. Metabolism increased linearly until the first date at which eggs were able to hatch. At that time, metabolic rate stabilized and remained constant for two additional weeks of embryonic incubation. Larvae induced to hatch after different durations of incubation within this period were not significantly different in length; however, the amount of oil contained in the yolk decreased linearly during the delayed hatching period. We suggest that the increase in grunion egg metabolism during the time to primary hatching capability, and the steady, high metabolic rate throughout the delayed hatching period, permit reproduction in the unique niche of these marine eggs. These semiterrestrial anamniotic eggs develop quickly and remain continuously ready to hatch over an extended period in response to an environmentally dependent and somewhat unpredictable embryonic timetable.

Adaptation, Physiological↗
PubMed1984

Photoperiod influences the annual reproductive cycle of the male pallid bat (Antrozous pallidus).

Adult pallids bats collected in April or May, were maintained in short or long photoperiods (10 or 14 h light/day) for 3-6 months. In August, the short-day bats had regressed testes, epididymal spermatozoa and fully developed accessory sex glands, corresponding to the autumnal reproductive condition of field animals; long-day bats had testes undergoing spermatogenesis, few epididymal spermatozoa and undeveloped accessory sex glands (summer reproductive condition). Bats in each photoperiod manifested the expected autumnal reproductive pattern in October. We suggest that photoperiod influences the reproductive physiology of male pallid bats by affecting an endogenous circannual reproductive rhythm.

Animals↗
PubMed1975

[Reproduction of Bothrops moojeni Hoge in captivity].

It is stated that there are sufficient different morphological characteristics in order to distinguish the sexes with a certain practice, but that each of these characteristics by itself does not alone represent a completely valid criterium. These observations have shown in the periods of reproduction a chifting of six months after six years of captivity. Then the various phases of sexual behaviour are related: the male-fight, the courtship, the conquest of the partner by sexual display and finally the copulation. It is established moreover that the period between the copulation and parturition does not necessarily constitute the duration of gestation, which seems in fact shorter because of retarded fertilizations. However, there is quite a constant average of a period of gestation of 200 days. There follows a complete inventory of the 29 copulations and 67 layings that were observed.

Aggression↗