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Biomedical subjects

W D Oxender

Publications and source records attributed to W D Oxender.

At least 37 records · Page 2Linked to original sources
PubMed1977

Resistance of neonatal calves given colostrum diet to oral challenge with a septicemia-producing Escherichia coli.

Twenty Holstein-Friesian male calves were obtained within 4 hours after bith (colostrum deprived) and allotted to 1 of 4 groups, each given a different feeding: colostrum, milk replacer, polyvinylpyrrolidone (PVP), and saline solution (0.85% NaCl). Each calf was fed 2 L of the respective diets every 12 hours. Rectal temperatures were recorded and blood samples were collected immediately before each feeding. At approximately 27 hours of age, all calves were inoculated orally with 1.5 X 10(10) viable organisms of a septicemia-producing Escherichia coli serotype O26: K60:NM. Within 8 hours, all calves had diarrhea. Coli-septicemia (E coli cultured from liver, spleen, and cardiac blood) was present in 1 of the 5 calves fed colostrum, in 5 or the 5 calves fed milk replacer, in 5 of the 5 calves fed PVP, and in 4 of the 5 calves fed saline solution. At necropsy of the calves (12 to 48 hours after oral inoculation), the same organism was isolated by cultural technique from small intestines of 19 of the 20 calves. Serum immunoglobulin G concentrations increased (P less than 0.01) in calves fed the colostrum diet in sharp contrast to the agammaglobulinemia occurring in calves fed the milk replacer, PVP, or saline solution. Results indicate that colostrum fed to the calf soon after birth provides protection from colisepticemia, but does not prevent the diarrhea of colibacillosis.

Animals↗
PubMed1977

Estrus, ovulation, and serum progesterone, estradiol, and LH concentrations in mares after an increased photoperiod during winter.

On December 11, 1974, 15 seasonally anestrous mares were assigned at random to 1 of 3 experimental groups: outdoor-control, indoor-control, or indoor light-treated (a 16-hour photo-period). This experiment was terminated on April 21, 1975. The five mares in the indoor light-treated group ovulated 59.0+/-6.9 days later, which was 74 days earlier (P less than 0.01) than 2 of the 5 outdoor-controls (the other 3 ovulated after April 21 during a subsequent experiment) and 50 days earlier (P less than 0.05) than the indoor-controls. Durations of the 1st estrus for the 3 groups of mares were 13.3+/-3.6, 8.4+/-2.0, and 6.0+/-1.0 days for the indoor light-treated, indoor-control, and outdoor-control groups, respectively. The indoor light-treated mares averaged 4.2 estrous cycles before April 21, the indoor-control mares averaged 1.4 estrous cycles, and 2 of 5 outdoor-control mares ovulated 1 time during the experiment. The peripheral blood luteinizing hormone (LH), estradiol, and progesterone concentrations were minimal during winter anestrous. The hormone changes normally associated with estrous cycle activity in mares--maximal estradiol and luteinizing hormone concentrations near ovulation and maximal progesterone concentration during diestrus--were observed in all mares beginning at the 1st estrus. Hair loss was observed earlier in the light-treated mares, than in either of the other groups. In conclusion, a 16-hour photo-period initiated in early December for anestrous brood mares caused endocrinologically normal estrous cycles to begin within 2 months. This may allow breeding and foaling considerably earlier than normally expected.

Anestrus↗
PubMed1976

Increased blood LH and testosterone after administration of prostaglandin F2alpha in bulls.

Two types of experiments were conducted to determine the relationship of changes in blood luteinizing hormone (LH) and testosterone in bulls given prostaglandin F2alpha (PGF2alpha). Episodic surges of LH and testosterone occurred in tandem, apparently at random intervals, on the average once during the 8-hr period after bulls were given saline. In contrast, after sc injection of 20 mg PGF2alpha, blood serum testosterone increased synchronously to a peak within 90 minutes four-fold greater than pre-injection values, and the testosterone surges were prolonged about three-fold compared to those in controls. Each of the PGF2alpha-induced surges of testosterone was preceded by a surge of blood serum LH which persisted for about 45 minutes and peaked at about 3 ng/ml. In a second experiment, PGF2alpha was infused (iv, 0.2 mg/min) for 20 hr; blood plasma testosterone increased from 7.0+/-0.6 to 16.0+/-1.5 ng/ml within 2.5 hr and remained near this peak for 10 hr. Then testosterone gradually declined to about 9 ng/ml at the conclusion of the 20-hr infusion. These changes in testosterone were paralleled by similar changes in blood plasma LH, although LH declined 3 hr earlier than testosterone. Random episodic peaks of blood plasma LH and testosterone typical of untreated bulls resumed within 8 hr after conclusion of PGF2alpha infusion. In both experiments, the surge of testosterone after PGF2alpha was preceded by increased blood LH. We conclude that increased LH after administration of PGF2alpha probably caused the increased testosterone. However the mechanisms of these actions of PGF2alpha remain to be determined.

Animals↗
PubMed1976

Effect of gonadotropin-releasing hormone and human chorionic gonadotropin on cows with ovarian follicular cysts.

Ovarian follicular cysts of cattle were defined as follicular structures (larger than or equal to 2.5 cm, diameter) which persisted for 10 days or longer in the absence of functional luteal tissue. Thirty dairy cows with ovarian follicular cysts were allotted to 6 groups (5 cows per group) and each was given 0 (saline solution), 25, 50, 100, 150, or 250 mug of gonadotropin-releasing hormone (GnRH) by intramuscular (IM) injection. Samples of blood were collected before GnRH was injected (0 hour), at 0.25, 0.50, 0.75, 1, 2, 3, and 4 hours, and at 1, 7, 11, 15, and 20 days after treatment. Five additional cows with follicular cysts were treated IM with 10,000 units of human chorionic gonadotropin (HCG), and blood sample collections were made before treatment (0 hour) and on days 1, 7, 11, 15, and 20 after treatment. Serum luteinizing hormone (LH) concentration was not altered in cows given saline solution, but was increased significantly in cows given any of the doses of GnRH (in a dose-related manner). Peak LH responses occurred about 2 hours after GnRH was given, and by 4 hours LH was beginning to decrease. Serum progesterone concentrations increased by more than 2.0 ng/ml by day 11 after treatment in 18 of 20 cows treated with 50, 100, 150, or 250 mug of GnRH. Progesterone responses in these cows were greater (P less than 0.05) than in cows given saline solution or a 25-mug dose of GnRH. Mean progesterone response to the 4 large doses of GnRH was similar in magnitude and duration to serum progesterone changes during the leutal phase of the bovine estrous cycle. After cows were treated with HCG, serum progesterone values were similar to those in cows given GnRH (50 to 250 mug).

Animals↗
PubMed1975

Experiences with a veterinary preceptorial program.

An off-campus, practitioner-supervised training (preceptorial) program for veterinary students at Michigan State University was developed and introduced in the fall of 1972. The program was designed to meet the needs of students concentrating on food animal medicine. It has enabled senior students to receive degeee credit for on-the-job experience with practitioners. Students opting for the program gain experience and knowledge in segments of clinical veterinary medicine that are most available with off-campus practitioners. Exposure of students to the clinical abilities of private practitioners, the case method of study, and diagnostics in a realistic environment are the goals of the program. The program has afforded faculty members and private practitioners meaningful insights into the changing face of veterinary education. Indeed, the consensus of the faculty in the Department of Large Animal Surgery and Medicine at Michigan State University is that an off-campus curriculum. Participating students and practitioners report that the program has been successful and is worthy of expansion and continuation. Both groups rate the program favorably and believe it has been a worthwhile teaching-learning experience.

Curriculum↗
PubMed1975

Androgens in the bovine fetus and dam (38567).

Umbilical arterial and venous blood, and fetal testes were taken from 38 bovine fetuses at 90, 180 or 260 days of gestation. Concurrently blood also was taken from the jugular, and from the uterine artery and vein of the dams. Testosterone and androstenedione were determined by radioimmunoassays. Fetal testicular homogenates had 0.96 and 0.35 mug/g of testosterone and 0.39 and 0.50 mug/g of androstenedione at 180 and 260 days of gestation, respectively. Males had five to tenfold more serum testosterone and about twofold more androstenedione than female fetuses at each trimester of gestation. Male fetal blood testosterone decreased (P less than 0.01) from 2.7 to 0.3 ng/ml between 90 and 260 days of gestation. But, maternal testosterone and androstenedione increased (P less than 0.05) during gestation in cows with males, but not in cows with female fetuses. Testosterone was higher (P less 0.05) in cows carrying males than in cows with female fetuses. Androstenedione was higher in blood leaving the placenta on both the maternal and on the vetal sides suggesting placental synthesis of androstenedione.

Androstenedione↗
PubMed1975

Luteinizing hormone and androgens in the bovine fetus after gonadotropin-releasing hormone.

After an intra-arterial injection of 10 mug GnRH into four bovine male fetuses, serum LH increased (P less than 0.01) 2-fold by 15 min and plateaued at approximately 11 ng/ml from 60 to 180 min. After GnRH in six female fetuses, LH increased (P less than 0.01) 7-fold by 15 min and plateaued at approximately 17 ng/ml from 60 to 180 min. Maternal serum LH was not significantly influenced (P greater than 0.05) by sex of fetus or administration of GnRH to the fetus. After GnRH in male fetuses, serum testosterone increased (P less than 0.05) and remained 2-fold greater than basal levels through 180 min. In contrast, serum testosterone from female fetuses averaged 370 +/- 60 pg/ml at injection and was unchanged after GnRH. Androgen synthesis was significantly increased during in vitro incubation of fetal testicular explants by the addition of LH. We conclude that GnRH causes release of LH from the bovine fetal pituitary as early as 120 days of age and that the testes respond with testosterone secretion after LH stimulation.

Androstenedione↗
PubMed1975

The cycle of oestrus, ovulation and plasma levels of hormones in the mare.

The duration of the oestrous cycle and day of ovulation were recorded in six mares which were used for concurrent assay of plasma levels of sex steroids and pituitary LH concentration. Peak of progesterone were reached during dioestrus and those of oestradiol and androstenedione occurred 2 days before ovulation and were in decline on the day of ovulation. Plasma oestrone remained constant (between 9 and 12 pg/ml) throughout the cycle. Plasma LH rose to a maximum near to the time of ovulation, and thereafter decreased gradually until mid-dioestrus. The pattern of secretion is compared with that reported in other domesticated animals.

Androstenedione↗
PubMed1975

Oestrus, ovulation and plasma hormones after prostaglandin F2alpha in mares.

The luteolytic effect of PGF2alpha, administered by intrauterine infusion or subcutaneous injection during early dioestrus, was observed in mares of mixed breeds. An infusion of 10 mg on Days 7 to 9 after ovulation caused a sharp fall in plasma progesterone levels and induced oestrus and ovulation. Oestrus was significantly longer than in the natural cycle but the time of ovulation in relation to the end of oestrus was normal. The time of return to oestrus following luteolysis was not dependent on the amount of PGF2alpha within the range of doses given. Luteolysis could be induced as early as Day 5 following natural ovulation.

Androstenedione↗
PubMed1975

Control of estrus with prostaglandin F2alpha in mares: minimal effective dose and stage of estrous cycle.

To determine the minimal effective dose of prostagiandin (PGF2alpha; tromethamine salt) given subcutaneously (SC), mares of mixed breeding (400 kg av body weight) were given 2-, 3-, 5-, and 10-mg doses from 7 to 9 days after ovulation. In some but not all mares given doses of 2 and 3 mg of PGF2alpha, luteolysis occurred, but doses of 5 or 10 mg of PGF2alpha were luteolytic in all mares. The 10-mg dose of PGF2alpha did not cause luteolysis in mares 1 day after ovulation, and caused luteolysis in only 2 of 5 mares on day 3 after ovulation. The same dose of PGF2alpha, however, caused luteolysis in all mares on days 5 or 7 after ovulation. The results indicate that the minimal effective luteolytic dose of PGF2alpha (free-acid equivalent) is about 9 mug/kg, and that PGF2alpha is effective fromday 5 after ovulation.

Animals↗