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Biomedical subjects

F N Thompson

Publications and source records attributed to F N Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1987

Prostaglandin F2 alpha metabolite levels in normal and uterine-infected postpartum cows.

The stable metabolite of prostaglandin F2 alpha,15 keto-13,14-dihydroprostaglandin F2 alpha (PGFM), was measured from peripheral blood samples collected at specified intervals postpartum from 7 normal dairy cows and 4 cows with apparent endometritis. Plasma PFGM levels were significantly (P less than .05) elevated for the first 5 days postpartum in the cows with endometritis (ranging from 4.0 to 5.0 ng/ml) compared to the controls (approximately 1.0 ng/ml). Beyond 5 days postpartum, plasma PGFM levels were not significantly different and decreased to approximately 0.4 ng/ml by day 13 in both groups. Time to uterine involution was not different between groups (less than 30 days). Therefore, uterine infections in cows during the puerperium was associated with elevated circulating PGFM levels. These findings and the observation that PGF2 alpha is not uterotonic in the puerperal cow do not suggest a therapeutic use of PGF2 alpha in order to evacuate the uterus.

Animals↗
PubMed1987

Selected hormonal changes with summer fescue toxicosis.

The effects of fescue endophyte content (low, 16 or high, 44% of tillers examined) and of N fertilization rate (low, 134 kg N.ha-1.yr-1 or high, 336 kg N.ha-1.yr-1) upon serum prolactin (PRL) in Angus steers were examined. Jugular blood samples for serum PRL determination were taken before (basal) and after thyrotropin releasing hormone (TRH) administration (stimulated). Areas under both the basal and stimulated PRL curves were calculated. While areas under the PRL curves varied with length of photoperiod, high endophyte content resulted in a consistent PRL suppression during 1984. During four time periods in 1984 (May to October), areas under the PRL curves [basal and(or) TRH stimulated] were suppressed (P less than .05) with high endophyte on three dates. Although basal areas under the PRL curves in 1983 were nonsignificantly suppressed with high endophyte, there was a suppression (P less than .05) post-TRH in October with high endophyte. There was no effect of N on PRL areas in either year. No relationship was found to exist between basal PRL areas and average daily gains as computed to encompass a period 2 wk before and after a blood collection date. Mean basal growth hormone (GH) concentration as determined from one bleeding date were elevated (P less than .05) in steers on high compared with low endophyte (7.9 and 6.2 ng/ml +/- 1.1 overall SE, respectively). There was no effect of treatment on TRH-stimulated serum GH values. Mean basal serum insulin values ranged from 13.2 to 17.5 microU/ml (+/- 1.2 overall SE) and were not affected by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1986

Thyroidal and prolactin secretion in agalactic mares.

A study was designed to examine serum concentrations of prolactin (PRL) and iodothyronines before and after thyrotropin releasing hormone (TRH) administration to agalactic (n = 26) and normally (n = 8) lactating mares. Two mg TRH was given intramuscularly (i.m.) twice daily on Day 1 (day of delivery) through Day 5. Jugular venous blood was collected on Days 1 and 5 before TRH (time 0) and at 1 and 3 h post-TRH. Basal serum concentrations of thyroxin (T(4)) were different (P < 0.05) on Day 1 (1.87 vs 1.37 mug/dl) and Day 5 (1.72 vs 1.13 mug/dl) in the normal mares and agalactic mares, respectively. There was no difference in the T(4) response to TRH. While basal serum concentrations of triiodothyronine (T(3)) were not different, agalactic mares responded with greater (P < 0.05) serum concentrations T(3) to TRH on Day 1. Following linear regression of the PRL response to TRH, slope of the lines between groups did not differ; however, elevations were significantly (P < 0.05) greater (1.79 vs 1.28 ng/ml) in control mares compared with agalactic mares, respectively, on Day 1.at 1 h post-TRH. A similar difference existed at time 0 and 1 h on Day 5. Consequently, agalactic mares had reduced basal serum T(4) values; the PRL data leads us to suggest that secretion of this hormone may be insufficient in agalactic mares.

Journal Article↗
PubMed1986

Effect of naloxone on serum luteinizing hormone, cortisol and prolactin concentrations in anestrous beef cows.

Two experiments were conducted with the opioid antagonist naloxone to determine the effect of opioid receptor blockade on hormone secretion in postpartum beef cows. In Exp. 1, nine anestrous postpartum beef cows were used to measure the effect of naloxone on serum luteinizing hormone (LH), cortisol and prolactin concentrations. Cows received either saline (n = 4) or 200 mg naloxone in saline (n = 5) iv. Blood samples were collected at 15-min intervals for 2 h before and after naloxone administration. Serum LH concentrations increased (P less than .01) in naloxone-treated cows from 1.8 +/- .04 ng/ml before treatment to 3.9 +/- .7 ng/ml and 4.2 +/- .5 ng/ml at 15 and 30 min, respectively, after naloxone administration. In contrast, LH remained unchanged in saline-treated cows (1.6 +/- .3 ng/ml). Serum cortisol and prolactin concentrations were not different between groups. In Exp. 2, 12 anestrous postpartum beef cows were used to examine the influence of days postpartum on the serum LH response to naloxone. Four cows each at 14 +/- 1.2, 28 +/- .3 and 42 +/- 1.5 d postpartum received 200 mg of naloxone in saline iv. Blood samples were taken as in the previous experiment. A second dose of naloxone was administered 2 h after the first, and blood samples were collected for a further 2 h. Serum LH concentrations increased (P less than .01) only in cows at 42 d postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗
PubMed1986

Influence of calf removal on the serum luteinizing hormone response to naloxone in the postpartum beef cow.

Twelve anestrous, postpartum beef cows were used to determine the effect of calf removal on the effect of naloxone on serum luteinizing hormone (LH) concentrations. On d 1, six cows were injected iv with saline and six with 200 mg naloxone dissolved in saline. Blood samples were taken at 15-min intervals for 2 h before and 2 h after naloxone or saline administration. At the beginning of blood sampling, calves were removed from three cows in each treatment. At 48 h after calf removal (d 3), all cows were injected iv with 200 mg naloxone and blood samples were collected as on d 1. On d 1, naloxone treatment increased (P less than .01) serum LH concentrations from 1.2 +/- .3 ng/ml at time 0 to 4.3 +/- .6 ng/ml and 4.7 +/- .8 ng/ml at 15 and 30 min, respectively. Injection of saline had no effect on serum LH concentrations. Forty-eight-hour calf removal increased (P less than .01) serum LH concentrations in five of six cows (1.7 +/- .8 vs 4.4 +/- 1.2 ng/ml). Naloxone treatment failed to increase serum LH concentrations in these cows. Injection of naloxone increased (P less than .01) serum LH concentrations in the one cow that did not exhibit an LH increase after calf removal and in six cows whose calves were not removed (1.4 +/- .2 vs 4.4 +/- .5 ng/ml). The present study provides additional evidence that endogenous opioids regulate LH in the postpartum beef cow. We hypothesize that suckling stimulates an opioid inhibition of LH secretion and removal of the suckling stimulus removes the opioid inhibitory tone.

Animals↗
PubMed1986

Opioid inhibition of luteinizing hormone secretion during the postpartum period in suckled beef cows.

Recent studies have shown that naloxone (N), an opioid antagonist, increases concentrations of luteinizing hormone (LH) in the postpartum anestrous beef cow. However, the LH response to N was influenced by the postpartum interval. For example, a significant LH response to 200 mg of N occurred on d 42 but not on d 14 or 28 postpartum. The present study was conducted to determine the effect of different doses of N on LH secretion during the postpartum period of beef cows. Twelve cows were given 200, 400 or 800 mg of N on d 14, 28 and 42 postpartum in a Latin square design with repeat measures within cells. On d 14, serum concentrations of LH increased (P less than .01) from .5 +/- .1 ng/ml (mean +/- SE) before N to a peak of 2.0 +/- .5 and 1.4 +/- .5 ng/ml for cows given 400 and 800 mg of N, respectively. In contrast, 200 mg of N had no effect on serum concentrations of LH. On d 28 and 42 all three doses of N elevated (P less than .01) serum concentrations of LH. Therefore, a larger dose of N was required to increase serum concentrations of LH on d 14 postpartum compared with d 28 and 42. Based on these data we suggest that endogenous opioids participate in the regulation of LH secretion in the early postpartum period. The differential response to naloxone may be due to changes in endogenous opioid inhibition of LH secretion during the postpartum period.

Animals↗
PubMed1985

Effect of nutrition on the LH response to calf removal and GnRH.

Ten primiparous crossbred cows were assigned to two dietary groups at calving. One group received 120% and the other group received 80% of the National Research Council (NRC) recommended allowance of dietary energy for primiparous cows. At 60 days postpartum, calves were removed from their dams. Blood samples were collected from the cows at 15-min intervals for 8 hr beginning at the time of calf removal and again 24 hr, 48 hr and 72 hr after calf removal. At 72 hr after calf removal, all cows were given 200 ug GnRH intravenously. At calf removal, serum LH concentrations were higher (P<0.01) for cows on 120% (0.9 +/- 0.03 ng/ml) compared to cows on 80% (0.5 +/- 0.03 ng/ml) of recommendations. Serum LH concentrations increased (1.6 +/- 0.1 ng/ml, P<0.01) by 24 hr in cows on the highenergy diet. In contrast, a similar increase was not observed in cows on the low-energy diet until 48 hr after calf removal (1.4 +/- 0.2 ng/ml, P<0.01). These contrasting patterns in serum LH concentrations resulted in a diet by time interaction (P<0.01). Serum LH concentrations increased in both dietary energy groups following GnRH injection, but the response was greater (P<0.01) in cows on the low-energy diet compared to the cows fed the high-energy diet. These results indicate that inadequate dietary energy delays the LH response to calf removal and increases the LH response to exogenous GnRH.

Journal Article↗
PubMed1985

Effect of calf removal on serum luteinizing hormone and cortisol concentrations in postpartum beef cows.

Serum luteinizing hormone (LH) and cortisol concentrations were measured in ten fall calving, Angus cows averaging 38 +/- 8 days postpartum. Calves from five cows were weaned at the beginning of the study. Blood samples were collected at 20 min. intervals for 48 h after weaning and for 8 h on day 4 and day 6 postweaning. Mean serum LH concentrations increased (P<0.01) in weaned cows (W) from 0.55 +/- 0.01 ng/ml at time of calf removal to 1.3 +/- 0.04 ng/ml 48 h afterwards. Comparable LH concentrations for suckled cows (S) were 0.65 +/- 0.08 ng/ml and 0.62 +/- 0.03 ng/ml respectively. Average serum LH concentrations at 48 h after weaning were greater (P<0.01) for W cows than S cows and a treatment by time interaction occurred (P<0.01) with serum LH concentrations increasing (P<0.01) from time of calf removal to 48 h after calf removal in W cows. Frequency of LH peaks increased (P<0.01) in W cows and by 48 h after weaning was greater (P<0.01) in W cows than in S cows. Magnitude of LH peaks did not differ between the two groups. Serum cortisol concentrations were not different between W and S cows except for a transient elevation (P<0.01) in W cows from 7.6 +/- 0.9 ng/ml to 11.9 +/- 1.0 ng/ml 9 to 12 h after calf removal. Since serum LH concentrations were increased in W cows but not in S cows at 48 h and serum cortisol concentrations increased transiently in W cows we suggest that circulating cortisol levels may not be a physiological inhibitor of LH secretion in the suckled postpartum beef cow.

Journal Article↗
PubMed1985

Effects of continuous alpha (1-24) ACTH infusion in the dog.

Dogs chronically infused with alpha (1-24) ACTH for 2 weeks showed continuous elevations in plasma ACTH, cortisol, and progesterone levels. Haematologic changes included immediate increases in numbers of mature neutrophils and monocytes and reduced numbers of eosinophils and lymphocytes. Haematocrits were also reduced with ACTH infusion. Whereas serum potassium levels fell in association with ACTH, serum sodium was unchanged. Activities of two serum enzymes of probable liver origin, alkaline phosphatase and alanine aminotransferase, increased gradually with ACTH treatment. Histologic examination of liver tissue revealed prominent hepatocellular vacuolisation. The trophic action of ACTH infusion was manifested by an increased adrenal gland weight and an enhanced cortisol response to a bolus ACTH injection given 1 day after the infusion ceased. Long-term infusion of ACTH resulted in haematologic, biochemical and morphologic changes resembling those observed in dogs with spontaneous pituitary-dependent hyperadrenocorticism.

Adrenocorticotropic Hormone↗
PubMed1985

Morphometric studies of the bovine uterus: microscopic lesions and retrospective reproductive history.

A survey of reproductive tracts from nonpregnant cows at an abattoir was conducted. Reproductive tracts from 98 cows were studied microscopically and evaluated with a grading system to determine the severity of pathologic changes. Inflammatory reaction (type and distribution), fibrosis, gland morphology, and appearance were measured, quantified, and scored (1 to 4). Category 1 endometrium (normal) was found in 18 cows, category 2 in 23, category 3 in 34, and category 4 in 23. The category of endometrium was then compared with the retrospective reproductive status, and it was found that reproductive problems had occurred in 6 cows (33.3%) in category 1, in 13 cows (56.5%) in category 2, in 25 cows (73.5%) in category 3, and in 21 cows (91.3%) in category 4. Cervicitis was found in 43 (43.8%) genital tracts; 16 cows (16.3%) had salpingitis. Ovarian lesions were not observed. Serum samples were tested for certain antibodies. Only 1 was seropositive for brucellosis, but 61 of 81 sera had leptospira titers greater than 1:100 and 1:50 (hardjo). The serovar hardjo was the most prevalent. All sera had neutralizing titers against parainfluenza type 3 virus; 74.2% and 56.7% of the sera had neutralizing antibodies against bovine viral diarrhea virus and infectious bovine rhinotracheitis virus, respectively.

Animals↗
PubMed1984

Serum thyroxine and triiodothyronine concentrations in canine pyoderma.

In an effort to evaluate the effect of pyoderma on circulating iodothyronines, plasma triiodothyronine (T3) and thyroxine (T4) values were determined before and after thyroid stimulating hormone administration in 25 dogs with pyoderma and in 15 controls. Basal T4 values were increased in dogs with pyoderma, but neither stimulated T4 nor T3 values were altered by this condition. On the basis of low values for circulating iodothyronines, hypothyroidism was suspected in 3 dogs in the pyoderma group. The dog with the most involved lesions had extremely low T3 and T4 values as well as an autoimmune disease. It was concluded that most dogs with pyoderma do not have thyroid dysfunction.

Animals↗
PubMed1983

Effects of prednisone on thyroid and gonadal endocrine function in dogs.

To assess the effect of a glucocorticoid on thyroid and gonadal endocrine function, prednisone was administered on alternate days to dogs. The prednisone injections resulted in adrenocortical suppression, as shown by the response to ACTH. Basal plasma thyroxine and tri-iodothyronine concentrations were considerably reduced in prednisone-treated dogs. However, the thyroid response to injection of thyrotrophin-releasing hormone was not altered, indirectly demonstrating that pituitary release of TSH was not inhibited by prednisone. Similarly, the response of the thyroid to exogenous TSH was not reduced by prednisone treatment. Electron microscopic examination of thyroid tissue revealed accumulation of colloid droplets in the follicular cell cytoplasm of dogs treated with prednisone. It is postulated that prednisone may interfere with basal thyroid hormone secretion by inhibiting lysosomal hydrolysis of colloid in the thyroid follicular cell. Basal plasma concentrations of LH and testosterone, measured in the male dogs, were reduced by prednisone treatment. Responses of prednisone-treated dogs to luteinizing hormone releasing hormone were not significantly reduced. Prednisone administration did not alter testicular responsiveness to injection of human chorionic gonadotrophin. After orchidectomy, plasma LH values were significantly reduced in prednisone-treated dogs. Taken together, these results suggest that LH secretion in dogs is inhibited at the hypothalamic and/or pituitary level by prednisone administration, which consequently results in reduced testosterone concentrations.

Animals↗
PubMed1983

Use of a low dose synthetic ACTH challenge test in normal and prednisone-treated dogs.

The utility of a low dose (1 microgram/kg) synthetic ACTH challenge test in detecting moderate reductions in adrenocortical sensitivity in dogs was examined. First, the adrenocortical responses to an intravenous bolus of either 1 microgram/kg or 0.25 mg per dog of synthetic ACTH were compared in two groups of normal dogs. While plasma cortisol concentrations were similar in both groups 60 minutes after ACTH injection, dogs given 0.25 mg ACTH showed continued elevations in plasma cortisol concentrations at 90 and 120 minutes after ACTH injection. Later, the dogs previously tested with the 1 microgram/kg ACTH challenge were given a single intramuscular dose of prednisone (2.2 mg/kg) and retested with 1 microgram/kg of ACTH one week later. Plasma cortisol levels were significantly reduced after ACTH injection in dogs previously given prednisone demonstrating that a single intramuscular prednisone dose causes detectable adrenocortical suppression one week after administration. The 1 microgram/kg synthetic ACTH challenge test provides a sensitive means for evaluating adrenocortical suppression in dogs.

Adrenal Cortex↗
PubMed1983

Effect of prednisone on thyroid gland morphology and plasma thyroxine and triiodothyronine concentrations in the dog.

The effects of multiple IM injections of prednisone (2.2 mg/kg) on thyroid morphology and on plasma thyroxine (T4) and triiodothyronine (T3) concentrations in dogs were determined, and the effects of a single prednisone injection on the same circulating iodothyronine concentrations were assessed. Plasma T4 and T3 concentrations decreased significantly after 3 injections of prednisone were made. However, with a single prednisone injection, there was no significant difference in plasma T4 values between control and treated animals. Starting at 8 hours after a single prednisone injection and continuing through day 2, plasma T3 values were significantly lowered. Prednisone treatment also resulted in significantly more thyroid cytoplasmic colloid droplets per follicular cell (3.19 vs 0.57 in treated and control dogs). Lysosomal hydrolysis of colloid appeared to be inhibited by glucocorticoids in dogs, resulting in an alteration of normal thyroid gland functioning.

Animals↗
PubMed1982

Effect of monitoring corpus luteum function on days open.

The concentration of progesterone in milk fat was measured to ascertain whether knowledge of corpus luteum function could be used to increase reproductive efficiency. As they calved, 47 cows were assigned to either a milk-sampled group (24) or an unsampled control group (23). Progesterone concentrations indicative of a functional corpus luteum were first present at an average of 29.4 days postpartum. The average postpartum interval to first estrus was 49 days for cows sampled and 7.19 days for control cows. The postpartum interval to conception was 84.8 days for sampled cows and 113.7 days for control cows. Twenty of 63 (31.7%) ovulations were not associated with behavioral estrus. Cystic ovarian disease with periods of anestrus were observed in five cows. We conclude that failure to detect estrus was a more limiting factor in reproductive efficiency than was anestrus. To determine the reproductive status after breeding, we measured progesterone concentrations on days 19 through 23 postinsemination. Progesterone was higher for pregnant than for nonpregnant cows on all days. However, only on days 20 and 21 was there complete separation of the progesterone ranges in pregnant and nonpregnant cows.

Animals↗
PubMed1982

Effects of dexamethasone infusion on the plasma cortisol response to cosyntropin (synthetic ACTH) injection in normal dogs.

Graded dosages of cosyntropin (synthetic corticotropin) were injected into groups of normal dogs on consecutive days. On the first day, cosyntropin was administered alone and, on the second, dogs were infused with dexamethasone three hours before cosyntropin injection. Adrenocortical function was assessed by sequential measurement of plasma cortisol (hydrocortisone) concentration. While no response differences were noted to the various amounts of cosyntropin injected with or without dexamethasone pretreatment, the magnitude of adrenocortical response was significantly greater in dogs infused with dexamethasone. It is concluded that dexamethasone pretreatment renders the canine adrenal cortex more responsive to a subsequent injection of cosyntropin. The combined dexamethasone infusion-cosyntropin injection test produces consistent adrenocortical responses in normal dogs, and has potential value in evaluation of adrenopathic dogs.

Adrenal Glands↗
PubMed1982

Adrenocortical suppression in the dog given a single intramuscular dose of prednisone or triamcinolone acetonide.

Adrenocortical function was assessed in dogs given a single intramuscular dose of either prednisone or triamcinolone acetonide (TCA; or saline solution to controls) to determine the duration of adrenocortical suppression caused by 2 commonly used glucocorticoids. The glucocorticoids were administered at recommended therapeutic doses; therefore, dogs given prednisone received a greater amount of glucocorticoid activity than did in dogs given TCA. Basal and ACTH-stimulated plasma cortisol concentrations, as determined by radioimmunoassay, were obtained once a week. Total intravascular eosinophil concentration and skin responses to intradermally injected histamine phosphate were quantitated. Dogs given TCA showed suppressed basal and ACTH-stimulated plasma cortisol concentrations 1 week after injection; the latter change persisted 2 weeks after injection. Adrenocortical function in 1 of 4 dogs given TCA remained suppressed for 4 weeks. In contrast, prednisone did not significantly alter adrenocortical function. Although intravascular eosinophil concentrations did not vary among groups, skin responses to intradermally injected histamine phosphate were reduced 6 days after prednisone and TCA were given.

Adrenal Cortex↗