Biomedical subjects

J S Walton

Publications and source records attributed to J S Walton.

At least 19 recordsLinked to original sources

PubMed1995

Protamine use during peripheral vascular surgery: a prospective randomized trial.

PURPOSE: One hundred twenty patients undergoing aortic reconstruction (40), infrainguinal bypass (49), and carotid endarterectomy (31) were prospectively enrolled into a double-blind randomized trial to investigate the utility of routine heparin reversal with protamine. METHODS: All patients underwent systemic heparinization with 90 U/kg body weight during operation and after revascularization were randomized to receive either protamine or saline solution for heparin reversal. Blood loss was measured throughout the surgical procedure, and indexes of coagulation and the requirement for blood and blood products were documented during operation and the first 24 hours after operation. RESULTS: Plasma heparin concentration, partial thromboplastin time, and activated clotting time were significantly higher (p < 0.05) in those receiving saline solution at 20 minutes and 1 hour after administration. Total surgical blood loss was not significantly different between study groups. No significant differences were found in blood product requirement, intravenous fluid administered, hematocrit, or wound hematomas between groups at 24 hours. In addition, no difference was seen in the surgeon's subjective intraoperative assessment of hemostasis after administration of either study drug. Furthermore, after study drug administration protamine was associated with a deleterious effect on subsequent intraoperative blood loss (318 +/- 33 ml vs 195 +/- 18 ml, p < 0.05). CONCLUSIONS: Although protamine effectively reverses heparin anticoagulation, its routine use after elective peripheral vascular surgical reconstruction does not appear to provide any clinical benefit.

Aged↗

PubMed1991

Absence of oxytocin-neurophysin messenger RNA in the day-18 bovine conceptus.

Total cellular RNA was isolated from conceptus tissue obtained from 22 superovulated cows 18 days after artificial insemination. Total RNA was also isolated from luteal tissue from 3 cyclic cows 7 and 8 days after oestrus. Luteal and conceptus RNA were simultaneously subjected to formaldehyde-agarose gel electrophoresis and transferred to nitrocellulose by bidirectional diffusion blotting. Northern blots were probed using cDNAs specific for bovine oxytocin and bovine beta-actin gene sequences. Hybridization of the oxytocin cDNA to RNA was consistently observed on autoradiographs as a 0.6 kilobase (kb) band in lanes containing corpus luteum RNA, but was not detected in lanes containing conceptus RNA. The presence of conceptus RNA on the blots was confirmed by hybridization of the actin cDNA to conceptus RNA, which resulted in a 2.0 kb band on autoradiographs. These results suggest that oxytocin is not synthesized by the bovine conceptus on Day 18 of gestation.

Actins↗

PubMed1990

The effect of atropine on cadmium- and nickel-induced constriction of vascular smooth muscle of the dogfish shark ventral aorta.

We investigated the effect of blockade of muscarinic, cholinergic receptors by atropine on the Cd2(+)- and Ni2(+)-induced vasoconstriction of rings of endothelium-free, vascular smooth muscle from the ventral aorta of the dogfish shark, Squalus acanthias. Atropine reduced the Cd2(+)-induced vasoconstriction by approximately 50%, but did not alter the Ni2(+)-induced vasoconstriction, suggesting that the vasoactivity of these two metals may be, at least partially, via different pathways. In addition, this is the first demonstration that one component of Cd2+ vaso-toxicity may be via stimulation of muscarinic receptors.

Animals↗

PubMed1990

Recovery of bovine oocytes from small vesicular follicles for in vitro maturation and fertilization.

Five dairy and four beef breed, mature cows were used as oocyte donors to develop a system of multiple recovery of oocytes for in vitro maturation and fertilization. The animals were alternately treated with either 20 mg of follicle stimulating hormone (FSH) in four equal intramuscular injections or saline at 12 h intervals starting between days 9 and 13 of the oestrous cycle, and the procedure was repeated at three-week intervals for up to four collections. Eighteen collections resulted in the recovery of 124 oocytes from 181 follicles (69%). No serious side-effects were observed. Recovery was equally successful in both breeds and was not reduced in repeat attempts upon the same animal. Treatment with FSH only marginally increased the recovery rate (p less than 0.07) and did not affect the number of follicles aspirated (p greater than 0.05), which varied significantly (p less than 0.05) between cows. From 110 oocytes matured and fertilized in vitro, 70 embryos were recovered after culture in the rabbit oviduct or with trophoblastic vesicles in vitro, of which 30 had cleaved and 5 had progressed to an advanced stage of development. Hormone treatment did not affect zygote development (p greater than 0.05). Four non-surgical transfers of embryos obtained in these studies have resulted in two pregnancies determined ultrasonographically and the birth of a heifer calf. This suggests that the procedure for multiple oocyte recovery is safe and that it can be used successfully for obtaining oocytes for in vitro maturation and fertilization.

Animals↗

PubMed1990

Oxytocin-specific RNA, oxytocin and progesterone concentrations in corpora lutea of heifers treated with oxytocin.

Sixteen virgin Holstein heifers were used to study the role of oxytocin in luteal function. Oxytocin (100 i.u.) was administered on Days 2-5 (Exp. 1) or Days 2-6 (Exp. 2), and the corpora lutea were collected and weighed on Day 6 or Day 8, respectively. Plasma progesterone values and tissue concentrations of progesterone and oxytocin were determined by radioimmunoassay. In addition, the tissue level of the oxytocin-specific transcript was measured by dot-blot hybridization. Expression of the oxytocin-specific transcript was not affected by oxytocin treatment in either experiment. In contrast, plasma progesterone values and tissue progesterone and oxytocin concentrations were all decreased after 5 days of oxytocin treatment (Exp. 2), but not after 4 days (Exp. 1). Since oxytocin concentrations were reduced while the level of its transcript remained unaffected, oxytocin injections might be influencing either peptide processing or release.

Animals↗

PubMed1990

Effects of progesterone and human chorionic gonadotrophin administration five days postinsemination on plasma and milk concentrations of progesterone and pregnancy rates of normal and repeat breeder dairy cows.

Treatment with a progesterone-releasing intravaginal device between days 5 and 12 after estrus elevated (p less than 0.05) plasma progesterone concentrations between days 6 and 8 in comparison with controls. Treatment with injectable progesterone (200 mg) on days 5, 7, 9 and 11 postestrus did not increase plasma progesterone concentrations over controls. The administration of 1500 IU human chorionic gonadotrophin (hCG) on day 5 after estrus resulted in a sustained increase (p less than 0.01) in plasma progesterone concentrations from day 8 until day 20 when measurements ceased. Pregnancy rates, as a result of artificial insemination (AI) at the pretreatment estrus, in these treatments (n = 12-14 each), were unaffected by any of the treatments and ranged from 57.1 to 75.0% at 45-60 days post-AI. In a field trial, of 36 repeat breeder cows treated with 1500 IU hCG 5.5 days after insemination, 47.2% were pregnant at 60 days, whereas 39.5% of saline-treated controls were diagnosed pregnant. Treatment with hCG significantly (p less than 0.05) increased milk progesterone concentrations over controls on days 14 and 20 after insemination.

Administration, Intravaginal↗

PubMed1989

Estradiol-induced blockade of ovulation in the cow: effects on luteinizing hormone release and follicular fluid steroids.

Administration of 10 mg estradiol valerate (EV) to nonlactating Holstein cows on Days 16 of the estrous cycle prevented ovulation in 7 of 8 cows for 14 days post-injection. In these 7 cows, the timing of luteolysis and the luteinizing hormone (LH) surge was variable but within the normal range. At 14 days post-treatment, each of these cows had a large (greater than 10 mm) follicle, with 558 +/- 98 ng/ml estradiol-17 beta, 120 +/- 31 ng/ml testosterone, and 31 +/- 2 ng/ml progesterone in follicular fluid (means +/- SE). A second group of animals was then either treated with EV as before (n = 22), or not injected (control, n = 17) and ovariectomized on either Day 17, Day 18.5, Day 20, or Day 21.5 (24, 60, 96, or 132 h post-EV). Treatment with EV did not influence the timing of luteolysis, but surges of LH occurred earlier (59 +/- 8 h post-EV vs. 100 +/- 11 h in controls). The interval from luteolysis to LH peak was reduced from 44 +/- 6 h (controls) to 6.9 +/- 1.5 h (treated). Histologically, the largest follicle in controls tended to be atretic before luteolysis, but nonatretic afterwards, whereas the largest follicle in treated animals always tended to be atretic. Nonatretic follicles contained high concentrations of estradiol (408 +/- 59 ng/ml) and moderate amounts of testosterone (107 +/- 33 ng/ml) and progesterone (101 +/- 21 ng/ml), whereas atretic follicles contained low concentrations of estradiol (8 +/- 4 ng/ml) and testosterone (12 +/- 4 ng/ml), and either low (56 +/- 24 ng/ml) or very high (602 +/- 344 ng/ml) concentrations of progesterone. This study suggests that EV prevents ovulation by inducing atresia of the potential preovulatory follicle, which is replaced by a healthy large follicle by 14 days post-treatment.

Animals↗

PubMed1989

Effect of treatment with progesterone on pregnancy rate and plasma concentrations of progesterone in Holstein cows.

Progesterone-releasing intravaginal devices inserted into the vaginas of dairy cows between d 5 to 12 (n = 28) or d 10 to 17 (n = 27) after insemination increased pregnancy rate to 60 over 30% in untreated control cows (n = 30). Plasma progesterone concentrations were increased during both progesterone treatments. Subtraction of the estimated contribution of exogenous progesterone indicated that endogenous, luteal progesterone was reduced during d 10 to 17 but not during d 5 to 12. Supplemental progesterone increased pregnancy rate but suppressed endogenous production of progesterone when administered during d 10 to 17 after insemination.

Administration, Intravaginal↗

PubMed1989

Identification of a luteotrophic protein in bovine allantoic fluid.

Allantoic fluids (n = 65) of Day 24-37 bovine conceptuses were collected and assayed for luteotrophic activity in vitro with dispersed bovine luteal cells. Significant luteotrophic activity was found in 41% of the samples, with the highest percentage occurring between Days 25 and 28. The activity is ammonium sulphate-precipitable, heat-labile and inactivated by trypsin and chymotrypsin. Gel filtration column chromatography identified one peak of luteotrophic activity with a molecular weight of 68,000. Concanavalin A bound the luteotrophic activity, thus allowing rapid and substantial purification from a major protein of Mr 68,000 which was concanavalin A non-reactive. The results of one- and two-dimensional SDS-PAGE of concanavalin A-reactive fractions containing activity suggest that the luteotrophic activity present in allantoic fluid is associated with a glycoprotein of Mr 68,000 present in very low concentrations. The active factor does not appear to be alpha-fetoprotein. This protein may be an important conceptus-derived luteotrophin that stimulates progesterone production by the corpus luteum of cows during pregnancy.

Allantoin↗

PubMed1987

Relationships between time of day, estrous behavior, and the preovulatory luteinizing hormone surge in Holstein cows after treatment with cloprostenol.

Using continuously observed primiparous cows, comparisons were made between cloprostenol-induced and preceding or succeeding spontaneous estruses in a crossover design. There were no significant differences between spontaneous and induced estruses in duration or intensity. In a second experiment, estrus was controlled by administration of two cloprostenol injections, 12 h apart, initiated at 0800 or 2000 h during the midluteal phase. Continuous observation and frequent blood sampling were used to determine relationships between behavior and plasma concentrations of LH and estradiol-17 beta. Relationships between plasma concentrations of estradiol-17 beta and the intensity or duration of estrous behavior were not detected. The intervals from treatment to the onset of estrus and to the LH surge were not affected by time of treatment but were highly correlated. The onset of the LH surge always followed the onset of standing to be mounted by 1 to 2 h. Initiating treatment with cloprostenol at 2000 h resulted in an increased proportion of animals exhibiting onset of estrus and increased mounting behavior at night relative to treatment at 0800 h. For efficient detection of estrus after cloprostenol treatment it is suggested that cloprostenol be administered early in the working day.

Animals↗

PubMed1986

Effect of environment on the intake of food and water, body weight, egg production and plasma concentrations of corticosterone and prolactin in turkey hens.

During the first 4 weeks of egg production, there were no differences in the plasma concentrations of prolactin and corticosterone, egg production, body weight and the consumption of food and water between turkey hens which were maintained in cages or in floor pens. The plasma concentration of prolactin increased to the same extent in both environments during the period of peak egg production. A further rise in concentration of prolactin occurred in association with the termination of oviposition in 15 of the 19 hens which stopped laying eggs. Prolactin appeared to be progonadal and then antigonadal, once a threshold concentration was exceeded. This threshold value was higher in caged turkey hens. After laying ended, high concentrations of prolactin in hens maintained in cages were not maintained in the absence of a stimulus or stimuli associated with the nests.

Animals↗

PubMed1986

Effect of boar presence before and after weaning on estrus and ovulation in sows.

Two hundred sixty-two sows were used to investigate the effects of boar exposure during the last week of nursing (BPRE) and after weaning (BPOST) on the return to estrus. Because approximately one-half of the sows were weaning their first litter, a third factor, primiparous vs multiparous (LITT), was considered in the statistical analysis. To evaluate the effect of treatment on ovarian activity, the sows were also blood-sampled twice weekly for 3 wk after weaning for the measurement of plasma progesterone concentrations as an index of ovulation. Boar exposure after weaning was the most important stimulus of early ovulation and estrus after weaning (P less than .001). A greater proportion of first-litter sows exhibited estrus later (P less than .02) and ovulated later (P less than .09) than did multiparous sows. First-litter sows were unaffected (P greater than .10) by boar exposure before weaning. Multiparous sows were sensitive to boar exposure during nursing. Maximal boar exposure for these sows (BPRE + BPOST) resulted in 95% of sows in estrus and ovulating within 20 d of weaning. No boar exposure resulted in 45% and 38% anestrus and anovulatory sows. Boar exposure, either before or after weaning, was effective in reducing the number of anestrus and anovulatory sows to between 15 to 30%. The effects of BPRE and BPOST on return to ovulation were additive and approximately equal.

Animals↗

PubMed1986

Reproductive performance of lactating Holstein cows fed supplemental beta-carotene.

Fifty-six Holstein cows were used in a replicated study to determine whether supplemental beta-carotene improved reproductive performance. Each of two replicates was of completely randomized design with 2 X 2 factorial arrangement of two diets with or without beta-carotene supplementation. On a dry matter basis, diet 1 was 5% hay, 20% haylage, 25% corn silage, and 50% concentrate. Diet 2 was 7.5% hay, 42.5% corn silage, and 50% concentrate. The diets contained adequate amount of vitamins A, D, and E. From 10 d postpartum until pregnancy was confirmed by rectal palpation, half the cows on each diet received a supplement of 400 mg beta-carotene per head daily. The remaining cows on each diet received a supplement of 160,000 IU vitamin A per head daily. Supplemental beta-carotene increased plasma beta-carotene throughout the trials. Median days to first ovulation, first service, days open, and mean services per conception were: 22, 77, 97, and 1.6 for cows receiving beta-carotene supplement compared with 19.5, 73, 82, and 1.9 in controls. Supplementation did not affect first service conception rate, uterine involution, or milk yield. Incidence of follicular cysts, luteal cysts, pyometra, and endometritis in cows fed beta-carotene were 11, 7, 0, and 7% compared with 8, 21, 4, and 13% in control cows. Supplemental beta-carotene did not improve the fertility of Holstein cows.

Animals↗

PubMed1986

Indicators of estrus in Holstein cows housed in tie stalls.

Fourteen lactating Holstein cows were observed between 40 and 150 d postpartum to identify physiological and behavioral changes associated with the day of estrus. Ovulation was predicted on 29 occasions from changes in concentrations of progesterone in milk. Estrus was detected by casual observation by the herdsperson 22 times, but only 13 were detected during a daily 30-min exercise period with an androgenized heifer. Morning milk yield and daily feed intake decreased on the day of estrus. Rectal temperature, afternoon milk yield, and number of changes in postural position during the previous night increased on the day of estrus. When an increase greater than one standard deviation from the within-cow mean was considered evidence of estrus, all measures indicated more false positives than true positives. A combination of elevated temperature, increased changes of postural position at night, and depressed feed intake accurately predicted estrus, but only on 6 occasions out of 29.

Animals↗

PubMed1985

Effect of feed and water deprivation or force-feeding on plasma prolactin concentration in turkey hens.

Plasma concentrations of prolactin (Prl), glucose, corticosterone, and D(-)-3-hydroxybutyrate (DBHB) were compared in nonlaying, nonincubating turkey hens subjected to feed and/or water deprivation. Neither Prl nor corticosterone concentrations were significantly (P greater than 0.05) altered by any of the treatments, whereas fasting significantly (P less than 0.05) reduced the concentration of glucose and increased the concentration of DBHB. Plasma levels of Prl in incubating hens were significantly (P less than 0.05) reduced by nest deprivation either in the absence of feed and water or when the hens were force-fed the normal intake for a laying hen. After 48 h of nest deprivation, the hens resumed nesting within 5 min of being returned to the pen although the plasma levels of Prl were low. Neither nest attentiveness nor the concentration of Prl were affected by force-feeding the hens while they were incubating eggs. The concentration of glucose increased in response to force-feeding or nest deprivation, whereas the concentration of corticosterone was increased only by force-feeding. These results suggest that Prl may not be involved in the striking changes in both intermediary and water metabolism which occur during incubation in the turkey hen. Furthermore, since incubation behavior can occur in the presence of low concentrations of Prl, elevated levels of Prl during broodiness appear to be maintained by a stimulus associated with the nest itself or some other aspect(s) of the environment.

3-Hydroxybutyric Acid↗

PubMed1985

Identification and measurement of 4-oestren-3,17-dione (19-norandrostenedione) in porcine ovarian follicular fluid using high performance liquid chromatography and capillary gas chromatography-mass spectrometry.

4-Oestren-3,17-dione (19-norandrostenedione) has been identified as a major steroid in porcine ovarian follicular fluid for the first time. This steroid was isolated by C18 reverse-phase high performance liquid chromatography (HPLC) and its structure was established unambiguously by capillary gas chromatography-mass spectrometry. The mean concentration in pooled fluid obtained from prepubertal gilts determined by HPLC and capillary gas chromatography was 1.71 mumol/l. The leve of this steroid in fluid obtained from large preovulatory follicles of sows exceeded 21.0 mumol/l on days 19 and 20 of the oestrous cycle. The high levels of this steroid within the follicle during the follicular phase might imply a possible biological role in follicular development and oocyte maturation.

Androstenedione↗

PubMed1985

The relationship between plasma concentrations of prolactin and consumption of feed and water during the reproductive cycle of the domestic turkey.

The plasma concentrations of prolactin (PRL) were measured throughout the reproductive cycle of turkey hens. Plasma PRL levels increased during egg laying from 20.1 +/- 3.9 ng/ml (means +/- SEM) at the first oviposition to 55.6 +/- 5.1 ng/ml at the last oviposition. Levels of PRL increased during incubation and were maintained between 70 and 90 ng/ml. After the poults were hatched, the concentration of PRL decreased rapidly and by 7 days after hatch, PRL levels were not significantly different from those observed before egg laying. The consumption of feed and water decreased significantly (P less than .05) during incubation to less than 10% of that observed during egg laying. The intake of feed and water increased rapidly after the poults were hatched. Hens lost 17% of their body weight during the incubation period. The concentration of D-(-)-3-hydroxybutyrate (DBHB) increased 16-fold during the incubation period and decreased rapidly after the poults were hatched. Body temperature and the concentration of glucose were significantly (P less than .05) depressed during incubation. Hematocrit increased significantly (P less than .05) during the transition from egg laying to incubation. These data suggest that the changes in the concentration of PRL may be related to the large changes in intermediary and water metabolism that occur during broodiness.

Animals↗

PubMed1984

Effects of luteinizing hormone, progesterone, testosterone, estradiol and corticosterone on ovulation and luteinizing hormone release in hens treated with aminoglutethimide.

Aminoglutethimide (AG), an inhibitor of steroidogenesis, was administered s.c. to 5 groups of laying hens at a dose of 200 mg AG/kg body weight 9 h before expected midsequence ovulation. This dose has previously been demonstrated to consistently block ovulation. The injection of AG was followed by s.c. injections of: Group 1, 1.0 mg progesterone; Group 2, 0.1 mg estradiol-17 beta; Group 3, 1.5 mg corticosterone, all at 6 h prior to expected ovulation; Group 4, 1.0 mg testosterone at both 8 h and 5 h before expected ovulation; and Group 5, 25 micrograms of ovine luteinizing hormone (LH) at 8 and 50 micrograms ovine LH at 6 h before expected ovulation. For each group, 4 control hens were injected with AG and the appropriate vehicle. Blood samples were taken at 1- or 2-h intervals from the time of AG injection to the expected time of ovulation. The hens were killed 4 h after expected ovulation and examined for the occurrence of ovulation. In all hens injected with vehicle, ovulation and the preovulatory surges of progesterone, testosterone, estradiol-17 beta and LH were inhibited. The plasma concentration of corticosterone was not reduced following an injection of AG. Four of 6 hens ovulated in response to injection of ovine LH, although neither endogenous LH nor progesterone were released. Thus, LH appears to play a direct role in follicular rupture and extrusion of the ovum. The administration of progesterone induced a significant and prolonged rise in LH, restoring AG-blocked ovulation in all hens treated (n = 6). Injections of testosterone restored LH release in all hens and ovulation in 2 of 7 hens treated. Three of 7 hens ovulated in response to the corticosterone injection. A preovulatory rise in LH was not observed, indicating that corticosterone may exert its ovulation-inducing effect directly on the mature follicle. Estradiol-17 beta did not restore LH release or ovulation in any of the hens treated with AG.

Aminoglutethimide↗