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Abstract

Objectives

To test whether Oxytetracycline inactivates collagenase when combined as a potential treatment for retained fetal membranes in cattle and to determine whether Oxytetracycline passes to blood from fetal membranes after intraplacental injection.

Design

Prospective, controlled study.

Sample Population

288 placentomes from 12 cows in their third trimester of pregnancy and 4 cows at term pregnancy.

Procedure

8 experimental groups were established: saline control, collagenase, collagenase plus Oxytetracycline at 3 dosages, and Oxytetracycline at 3 dosages. Placentomes were infused through an umbilical vessel with the test solutions and incubated at 39 C for 4 hours. Immediately after incubation, the force needed to detach cotyledons from caruncles was measured by a manometry technique. Cotyledon-caruncle interface fluids were analyzed for hydroxyproline (collagen breakdown) and total protein contents. A combination of collagenase and Oxytetracycline was injected via umbilical arteries of cows undergoing cesarean section and in cows with retained fetal membranes after natural delivery. Antibiotic residue in blood was determined by the Bacillus stearothermophilus disk assay.

Results

There were no significant differences among collagenase and collagenase plus Oxytetracycline groups in the amount of pressure needed to separate cotyledon from caruncle, amount of hydroxyproline released, and amount of total protein broken down. The 4 cows tested negative for Oxytetracycline in the blood.

Clinical Relevance

Oxytetracycline and collagenase may be a potential combination treatment for retained fetal membranes in cattle. In addition, the lack of antibiotic residue detection in blood may be of regulatory relevance. (Am J Vet Res 1996;57:522–525)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the in vitro effect of the combination of lignan enterolactone (ENL) or lignan enterodiol (END) with melatonin on steroid hormone secretion and cellular aromatase content in human adrenal carcinoma cells. Sample—Human adrenocortical carcinoma cells.

Procedures—Melatonin plus ENL or END was added to cell culture medium along with cAMP (100μM); control cells received cAMP alone. Medium and cell lysates were collected after 24 and 48 hours of cultivation. Samples of medium were analyzed for progesterone, 17-hydroxyprogesterone, androstenedione, aldosterone, estradiol, and cortisol concentration by use of radioimmunoassays. Cell lysates were used for western blot analysis of aromatase content.

Results—The addition of ENL or END with melatonin to cAMP-stimulated cells (treated cells) resulted in significant decreases in estradiol, androstenedione, and cortisol concentrations at 24 and 48 hours, compared with concentrations in cells stimulated with cAMP alone (cAMP control cells). The addition of these compounds to cAMP-stimulated cells also resulted in higher progesterone and 17-hydroxyprogesterone concentrations than in cAMP control cells; aldosterone concentration was not affected by treatments. Compared with the content in cAMP control cells, aromatase content in treated cells was significantly lower.

Conclusions and Clinical Relevance—The combination of lignan and melatonin affected steroid hormone secretion by acting directly on adrenal tumor cells. Results supported the concept that this combination may yield similar effects on steroid hormone secretion by the adrenal glands in dogs with typical and atypical hyperadrenocorticism.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate glucose and lipid metabolism in healthy adult horses administered levothyroxine sodium (L-T4).

Animals—12 healthy adult mares.

Procedure—8 horses received an incrementally increasing dosage of L-T4 (24, 48, 72, or 96 mg of L-T4/d) for weeks 1 to 8. Each dose was provided between 7 AM and 8 AM in the morning grain meal for 2 weeks. Four additional horses remained untreated. Serum concentrations of nonesterified fatty acids, triglyceride (TG), total cholesterol (TC), and very-low-density lipoprotein (VLDL) were measured and composition of VLDL examined in samples obtained between 8 AM and 9 AM at weeks 0, 2, 4, 6, and 8. Glucose dynamics were assessed by use of a combined IV glucose-insulin tolerance test (IVGITT) conducted before and at the end of the 8-week treatment period. Data for each combined IVGITT were interpreted by use of the minimal model.

Results—Plasma TG, TC, and VLDL concentrations significantly decreased over time in treated horses. At the completion of the 8-week treatment period, mean plasma VLDL concentration was 46% of the mean value for week 0 in treated horses. Insulin sensitivity significantly increased (> 2-fold) in treated horses, but glucose effectiveness and net insulin response were not affected. Levothyroxine sodium significantly increased the rate of insulin disposal.

Conclusions and Clinical Relevance—Administration of L-T4 decreases blood lipid concentrations, improves insulin sensitivity, and increases insulin disposal in horses. Levothyroxine sodium may have potential as a treatment for horses with reduced insulin sensitivity. (Am J Vet Res 2005;66:1032–1038)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize the physiologic response to IV bolus injection of glucose and insulin for development of a combined glucose-insulin test (CGIT) in horses.

Animals—6 healthy mares and 1 mare each with pituitary adenoma and urolithiasis.

Procedure—Horses were given a CGIT (glucose, 150 mg/kg; insulin, 0.1 U/kg); results were compared with a singular IV glucose tolerance test (GTT; 150 mg/kg) and a singular IV insulin sensitivity test (IST; 0.1 U/kg). Healthy horses were also given a CGIT after receiving xylazine and undergoing stress.

Results—Physiologically, the CGIT resulted in a 2-phase curve with positive (hyperglycemic) and negative (hypoglycemic) portions; the positive phase came first (250% of baseline at 1 minute). The descending segment declined linearly to baseline by approximately 30 minutes and to a nadir at 58% of baseline by 75 minutes. After a 35-minute valley, a linear ascent to baseline began. Addition of insulin in the CGIT increased glucose utilization by approximately 4.5 times during the positive phase but not during the negative phase. The diseases' effects and experimental inhibition of insulin secretion with xylazine and stress were detectable by use of the 2 phases of the CGIT. Only a single positive phase resulted from the GTT and a single negative phase from the IST.

Conclusions and Clinical Relevance—The CGIT resulted in a consistent, well-defined glycemia profile, which can be disrupted experimentally or by a disease process. The CGIT has clinical potential because it provides integrated information and more information than either the singular GTT or IST. (Am J Vet Res 2005;66:1598–1604)

Full access
in American Journal of Veterinary Research

Objective—

To evaluate results of a combined dexa-methasone suppression/thyrotropin-releasing hormone (TRH) stimulation test in horses suspected clinically to have a pars intermedia pituitary adenoma (PIPA).

Design—

Case-control study.

Animals—

7 healthy adult horses and 5 horses suspected to have a PIPA.

Procedure—

A baseline blood sample was collected, and dexamethasone (40 μg/kg [18 μg/lb] of body weight, IV) was administered; a second blood sample was collected 3 hours later, and TRH (1.1 mg, IV) was administered; serial blood samples were collected 15, 30, 45, 60, and 90 minutes and 21 hours after TRH administration (24 hours after dexamethasone injection). Cortisol concentration was determined for all blood samples.

Results—

Baseline Cortisol concentration was significantly lower in horses suspected to have a PIPA than in healthy horses. Cortisol concentration was suppressed by dexamethasone in both groups; however, after TRH administration, Cortisol concentration returned to baseline values in horses suspected to have a PIPA, but not in healthy horses. Concentration was still less than the baseline value 24 hours after dexamethasone administration in healthy horses.

Clinical Implications—

The combined dexamethasone suppression/TRH stimulation test may be a useful diagnostic test in horses suspected to have a PIPA. For clinical application, collection of a blood sample 30 minutes after TRH administration is recommended. (J Am Vet Med Assoc 1997;211:79–81)

Free access
in Journal of the American Veterinary Medical Association