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Biomedical subjects

W W Thatcher

Publications and source records attributed to W W Thatcher.

At least 235 records · Page 13Linked to original sources
PubMed1981

Hormonal responses of lactating dairy cattle to TRH and ACTH in a shade management system within a subtropical environment.

Lactating cows (64) were balanced by breed (54 Holstein and 10 Jersey) and assigned randomly to shade (S) or no shade (NS) management treatments for a continuous 20 wk trial beginning 5-5-76. A sub-sample of Holstein cows, five S and five NS, were fitted with jugular catheters 84 days after initiation of experiment. Thyrotropin Releasing Hormone (TRH; 100 mug) was administered intravenously at 1200 h to evaluate prolactin responses. Two days later each cow received intravenously 200 IU of ACTH at 1100 h to compare acute corticoid responses to ACTH. Mean prolactin response to TRH was greater for NS cows (291 vs 169 ng/ml; P < .01) as was peak plasma concentrations at 20 min (467 vs 267 ng/ml; P < .01). Mean corticoid response to ACTH injection was less for NS cows (52 vs 70 ng/ml; P < .10). Corticoid concentrations of plasma in both treatments had declined 65% by 7 h postinjection. These endocrine differences may be associated with thermoregulation and/or metabolic adjustments of cows exposed to different environmental systems of management during a seasonal period of thermal stress.

Journal Article↗
PubMed1981

Hormonal interelationships and physiological responses of lactating dairy cows to a shade management system in a subtropical environment.

Lactating cows (n = 64) were assigned randomly to shade or no shade treatments for a continuous trial (20 wk) during summer of 1976. Respirations/min and rectal temperatures were higher for no shade cows. Dry matter forage intake was 9.7% higher for shade cows, whereas water intake was 19% greater for no shade cows. Milk yield and conception rates were higher for shade managed cows. Mean plasma corticoid concentrations were high throughout the entire estrous cycle in no shade compared to shade cows (13.04 > 8.72 ng/ml). No shade cows had higher progesterone and LH concentrations, and a lower estradiol to progesterone ratio during the cycle. Results indicated that endocrine changes were indicative of recurring estrous cycles in thermal stressed lactating dairy cows. However, alterations in water intake and thermoregulation of stressed cows were associated with decreased fertility and milk production, and changes in steroid concentrations that may reduce uterine blood flow.

Journal Article↗
PubMed1981

Periparturient endocrine changes of conceptus and maternal units in Jersey cows bred for milk yield.

Control cows, sired by and bred to bulls with assumed zero estimated breeding values, and selected cows, sired by and bred to bulls of high predicted difference for milk yield, were used. Blood samples were collected via jugular venipuncture on alternate days from 35 to 14 days prepartum, from 14 to 28 days postpartum, and daily from 14 days prepartum to 14 days postpartum. We examined blood hematocrit, and concentrations in plasma of protein, estrone, estradiol, estrone sulfate, progestins, glucocorticoids, luteinizing hormone, and prolactin. Total plasma volume was measured on days -21, -7, and +11. Weekly body weights, prepartum and postpartum, were recorded. All data were analyzed by least squares analysis of variance with day and hematocrit as continuous independent variables. Hematocrit was higher for selected cows throughout the sampling period. Prepartum concentrations of progesterone were higher in selected cows, but concentrations of estrone, luteinizing hormone, and prolactin were lower than in control cows. Hormonal and physiological responses indicated that selection for milk yield influenced both the conceptus and maternal units as measured by prepartum endocrine function.

Animals↗
PubMed1981

Periparturient and postpartum endocrine changes of conceptus and maternal units in Jersey cows bred for milk yield.

Control cows, sired and bred by bulls of zero estimated breeding value, and selected cows, sired by and bred to bulls of high predicted differences for milk yield, were used to evaluate maternal endocrine changes from 14 days prepartum to 28 days postpartum. Examined were concentrations in plasma of 13, 14 dihydro-15 keto-prostaglandinF2 alpha, progesterone, estrone sulfate, estrone, luteinizing hormone, and prolactin. Ability of cows to release prolactin and luteinizing hormone on day 10 postpartum was evaluated after a simultaneous injection of thyrotropin releasing hormone (100 microgram) and gonadotropin releasing hormone (100 microgram). Changes in progesterone and estrogens prepartum lead to peak concentrations of prolactin and prostaglandin at parturition and 3 days postpartum, respectively. Higher basal concentrations of prolactin for control cows prepartum were associated with a higher prolactin release by thyrotropin releasing hormone at 10 days postpartum. Although release of luteinizing hormone in response to gonadotropin releasing hormone did not differ between groups on day 10 postpartum, a subsequent increase in progesterone to above 1 ng/ml was earlier and more precisely synchronized among control cows (16 +/- .43 versus 23 +/- 2.33 days). Within cow concentrations of F2 alpha 13, 14 dihydro-15-keto-prostaglandin-F2 alpha were correlated with size of previous gravid uterine horn (.67) and milk yield (-.39). Selection for milk yield influenced postpartum endocrine function.

Animals↗
PubMed1980

A study of prostaglandin F2 alpha as the luteolysin in swine: V. Comparison of prostaglandin F, progestins, estrone and estradiol in uterine flushings from pregnant and nonpregnant gilts.

Uterine flushings were collected from 38 gilts representing Days 6,8,10,12,14,15,16 and 18 of the estrous cycle and pregnancy. The same group of gilts were represented within each of the respective days of the estrous cycle and pregnancy, i.e., three to six gilts per day per status. Uterine flushings (about 40ml) were assayed for prostaglandin F (PGF), estrone (E1), estradiol (E2), progestins (P) and protein. Nonpregnant gilts had higher (P < .01) concentrations of P in uterine flushings than pregnant gilts, but pregnant gilts had higher (P < .01) E1 and E2 concentrations. Significant day by status interactions were detected for E1 (P < .05), but not for E2 concentrations in uterine flushings. Total recoverable PGF and PGF concentrations in uterine flushings were greater (P < .01) in pregnant than nonpregnant gilts and significant (P < .01) day by status interactions were detected. In nonpregnant gilts, PGF increased between Days 12 and 16, i.e., during the period of corpora lutea (CL) regression. In pregnant gilts, PGF in uterine flushings increased markedly between Days 10 and 18. Total recoverable PGF on Day 18 of the estrous cycle was only 464.5 +/- 37.6 ng as compared to 22,688.1 +/- 1772.4 ng on Day 18 of pregnancy. Total recoverable protein was also higher (P < .01) in pregnant gilts. These data indicate that PGF synthesis and secretion by the uterine endometrium and/or conceptuses is not inhibited during pregnancy and suggest that PGF is sequestered within the uterine lumen of pregnant gilts, as is the total protein component of endometrial secretions referred to as histotroph.

Animals↗
PubMed1979

Actions of hormones on the uterus and effect on conceptus development.

The process of reproduction in the mammalian female involves interactions between gonadal and placental steroids and, possibly, protein hormones such as placental lactogen, and the uterine endometrium. These interactions are discussed relative to available data from pigs and with the understanding that the concepts presented may not be directly applicable to other species. Swine embryos enter the uterus for continued development beyond the early blastocyst stage and, within the uterus, the spherical blastocyst, of about 2 mm diameter on day 12, undergoes rapid elongation to an organism of about 1 m in length by day 15 of pregnancy. During this period of elongation, the blastocyst appears to provide the chemical signal, presumably unconjugated estrogens, that allows for corpora lutea (CL) maintenance (luteostatic effect) and, therefore, continued production of progesterone by the CL which is essential for pregnancy. Estrogens from the blastocyst may exert their luteostatic effect on the uterus by causing prostaglandin F2 alpha, the presumed porcine uterine luteolysin, to be secreted in an exocrine (toward the uterine lumen) rather than an endocrine (toward the endometrial stroma and vasculature) direction during pregnancy. Consequently, prostaglandin F2 alpha is sequestered in the uterine lumen and does not become available, via the utero-ovarian vasculature, to exert its luteolytic effect. The potential steroid precursor(s) available to the trophoblast for estrogen synthesis appear to be produced through endometrial conversion of progesterone to unconjugated androgens, e.g., androstenedione and testosterone, and conjugated estrogens, e.g., estrone-sulfate and estradiol-sulfate. The estrogens may, in concert with progesterone and possibly other hormones, placental lactogen for example, act locally, i.e., at the site of placentation to: result in a luteostatic effect; increase uterine blood flow; enhance water, electrolyte and substrate (carbohydrate and amino acid) transport to the site of placentation and across the placenta; affect synthesis and secretion of macro-molecules (histotroph) by the uterine glands that serve as enzymes and (or) carrier molecules and control or modulate physiological and (or) biochemical events essential to placental and fetal development that are not understood.

Animals↗
PubMed1979

Hormonal and physical changes associated with bovine conceptus development.

Conceptus (placental membranes, fetal fluids and fetus) development was characterized between Days 27 and 111 of gestation. Progestagens, oestrone, oestradiol, oestrone sulphate and prostaglandins (PG) F were measured in maternal plasma and allantoic and amniotic fluids. Protein concentrations are described for fetal fluids. The early increase in placental membrane weight from 1.12 g (27 days) to 58.45 g (50 days) was associated with oestrogen production presumably of conceptus origin. Oestrogens increased significantly in allantoic and amniotic fluids throughout the period studied with oestrone being the primary free oestrogen, rising from 2 pg/ml (Day 33) to 144 ng/ml by 111 days in allantoic fluid. Changes in plasma oestrogens of the maternal circulation were not detected until after Day 70 at which time oestrone concentration was greater than that of oestradiol. Fetal fluid concentrations of progestagens, oestrone sulphate and PGF were not related to maternal plasma levels and a sequestration of these hormones by the allantois is postulated.

Allantois↗
PubMed1979

Luteolytic effect of oestrone sulphate on cyclic beef heifers.

The action of oestrone sulphate on luteal function was tested in cyclic beef heifers. Once daily injection of 28 or 56 mg oestrone sulphate in corn oil beginning on Day 10 of the cycle had a significant luteolytic effect as compared to corn oil-treated controls.

Animals↗
PubMed1978

Uterine luminal prostaglandin F in cycling mares.

Prostaglandin F was measured by radioimmunoassay in uterine flushings of cycling mares on days 4, 8, 12, 14, 16, 18 and 20 post-ovulation. Prostaglandin F was significantly (P less than .05) affected by day of the estrous cycle and reached maximal levels on day 14. Least squares means for days 4, 8, 12, 14, 16, 18 and 20 were: .66, .81, 4.77, 14.31, 5.48, 3.68 and 2.97 ng/ml, respectively.

Animals↗
PubMed1978

A study of prostaglandin F2alpha as the lutbolysin in swine: IV An explanation for the luteotrophic effect of estradiol.

This study evaluated effects of estradiol valerate on synthesis, secretion and direction of movement of immunoreactive prostaglandin F2alpha (PGF) in swine. Gilts were randomly assigned to provide uterine flushings representing days 11, 13, 15, 17 and 19 of the estrous cycle (three gilts/day). The same gilts then were allowed one estrous cycle for recovery. During the second postoperative estrous cycle they were treated with estradiol valerate (EV) (5mg/day, SC) on days 11 through 15 and uterine flushings again were obtained on the same respective days with the same gilts represented within each day. Total recoverable PGF per uterine horn increased from day 11 (X - 1.98 ng) to day 17 (X = 210.20 ng) and then declined to day 19 (X = 66.20 ng) during the control period. Following EV treatment average total recoverable PGF was the control period. Following EV treatment average total recoverable PGF was 1.9, 4,144.3 and 4,646.7 ng on the same respective days. EV treatment also resulted in maintenance of elevated levels of total protein and acid phosphatase activity in uterine flushings. These data suggest that estradiol may exert its luteotrophic effect by preventing the release of PGF from the uterine endometrium into the uterine venous system (endocrine secretion) while maintaining the movement of endometrial secretions into the uterine lumen (exocrine secretion).

Acid Phosphatase↗
PubMed1978

Development of the conceptus in the bovine.

Growth of fetuses, fetal membranes, and fetal fluids was characterized by least squares analysis for 254 conceptuses ranging from 25 to 278 days of gestation. Prior to 100 days of gestation, increases in allantoic fluid volume and chorio-allantoic membrane weight preceded those of fetal weight, amnio-allantoic membrane weight, and amniotic fluid volume. The relative rate of growth of components suggests a prerequisite of chorio-allantoic membrane expansion for subsequent fetal growth. Male fetuses were heavier than female fetuses as early as 100 days of gestation. Rate of growth of all fetuses was maximal at 230 days of gestation with a peak rate of greater than 200 g/day. Growth rate then declined to less than 100 g/day by term.

Allantois↗
PubMed1978

Induction of lactation: lactational, physiological, and hormonal responses in the bovine.

Milk yields, physiological responses, and concentrations of plasma hormones were evaluated in 24 attempts to induce lactation in nonlactating dairy cows. Subcutaneous injections of estradiol-17beta and progesterone (.10 and .25 mg/kg body weight per day) for 7 consecutive days were used. Dexamethasone injections (.028 mg/kg body weight per day) on days 18 to 20 were given during 12 attempts at induction. Milking was initiated on day 21. All cows showed proestrus activity within 2 days after the first steroid injection; this subsided, then reappeared in many animals between days 16 to 20. In 14 of 24 attempts mean daily milk production was greater than 5 kg. Actual or projected 305-day lactation milk yields were between 1859 and 5354 kg. However, milk yields of seven induced cows averaged only 73% (32% to 136% range) of their previous natural lactations. Dexamethasone injections increased the number of cows that produced more than 5 kg/day; however, milk yields were not improved. Concentrations of estradiol, estrone, and progesterone in plasma were unaffected by dexamethasone, but concentrations of glucocorticoids in plasma were depressed on days 19 to 22. Concentrations of prolactin (peak and mean) in plasma for six cows each that produced greater or less than 5 kg/day did not differ. However, concentrations of prolactin increased in the week following steroid injections (days 8 to 15) only in those cows that produced greater than 5 kg/day but were elevated in all cows during the 3rd wk.

Animals↗
PubMed1978

Adrenal responsiveness in pre- and postpartum dairy cows.

Adrenal responsiveness was evaluated by injecting 10 multiparous dairy cows with 200 IU adrenocorticotropin between -13 and -2 days prepartum (I) and postpartum between 24 and 40 h (II) and 21 and 24 days (III). Concentrations of glucocorticoids following injection were influenced by day of injection, temperature, and minimum percent relative humidity but not by breed, breed X injection day interaction, or age of cow. Likewise differences in regressions for adrenal response and mean response (ng/ml) for the three injections were nil. Mean concentrations at peak (45, 60, and 120 min postinjection samples) adjusted for preinjection concentrations also did not differ for the three periods of injection. Mean concentrations of glucocorticoids in plasma for daily samples between -13 and -2 days prepartum were 5.3 +/- .4 (n = 61), reached a peak of 14.8 +/- .3 ng/ml the day of calving, and remained high for 2 days postpartum. Estradiol increased through prepartum sampling from 23.3 to 339.6 +/- 94.1 pg/ml the day of calving, then declined abruptly. Progestins began to decline about -5 days prepartum from mean concentration of 4.09 +/- .62 (n = 25) and attained low concentrations (.30 +/- .06 ng/ml) 2 days postpartum. Although there was a surge of glucocorticoids at parturition, this was not associated with a modification in adrenal responsiveness or with prepartum concentrations of other steroid hormones of plasma. Adrenal potential in prepartum and postpartum dairy cows appears well maintained.

Adrenal Glands↗