Regulation of estrus and ovulation in mares with progesterone or progesterone and estradiol biodegradable microspheres with or without PGF2alpha.

A single injection of a microsphere preparation, designed to deliver 1.25 gm progesterone and 100 mg estradiol-17beta at a controlled rate, for a duration of 12 to 14 days, produces accurate control of estrus and fertile ovulations in mares. Treatment is followed by PGF2alpha injection 14 days after steroid injection. The objectives of the present study were to determine whether estradiol added to the progesterone treatment or PGF2alpha administered at the end of the steroid treatment regimen, would improve synchronization of estrus and ovulation. A total of 45 cyclic horse mares was randomly assigned to 1 of 5 treatment groups as follows: Group 1 (control, n=9) sterile microsphere vehicle+sterile PGF2alpha vehicle 14 days after treatment with microsphere vehicle; Group 2 (n=9) progesterone and estradiol microspheres+PGF2alpha 14 days after treatment with microspheres; Group 3 (n=9) progesterone and estradiol microspheres+PGF2alpha vehicle 14 days after treatment with microspheres; Group 4 (n=9) progesterone + PGF2alpha 14 days after treatment with microspheres; and Group 5 (n=9) progesterone+PGF2alpha vehicle 14 days after treatment with microspheres. Addition of estradiol (P<0.05) or PGF2alpha (P<0.05) to the treatment regimen increased synchronization efficary by reducing variation in days to ovulation. All treatments significantly reduced variation in days to estrus compared with that of the controls; however, mares in the progesterone groups had an increased incidence of silent or shortened estrous behavior (2 days in duration compared with mares treated with progesterone (78 vs 33%, respectively). Therefore, estradiol and PGF2alpha each appear to reduce variation in days to ovulation while estradiol seems to promote better expression of posttreatment estrous behavior.

Diaphragmatic herniation as a cause of lethargy and exercise intolerance in a mare.

A diaphragmatic hernia in which 90% of the large colon had herniated through a 16-cm linear tear in the diaphragm was found in a 12-year-old Quarter Horse mare. Clinical signs included lethargy and exercise intolerance. Diagnosis of diaphragmatic hernia was made based on careful thoracic auscultation, combined with ultrasonographic and radiographic examination of the thorax.

Struvite urethral calculus in a three-month-old thoroughbred colt.

A 3-month-old Thoroughbred colt was presented with signs of colic. Findings from physical examination, abdominal paracentesis, abdominal radiographs and clinical pathology revealed uroperitoneum secondary to a calculus obstructing the urethra and causing subsequent urinary bladder rupture. Analysis of the calculus demonstrated a tissue center with outer concretions composed primarily of struvite.

Effect of l-Homoserine on the Growth of Mycobacterium tuberculosis.

l-Homoserine was observed to inhibit the growth of Mycobacterium tuberculosis. In the metabolism of M. tuberculosis, l-homoserine was found to be a precursor of threonine, isoleucine, and methionine. l-Homoserine-inhibited cells contained elevated levels of the enzyme acetohydroxy acid synthetase. In addition, washed cell suspensions of M. tuberculosis formed significant amounts of alpha-amino-n-butyric acid from supplements of l-homoserine. dl-Alpha-amino-n-butyric acid proved to be much more inhibitory for growth than l-homoserine. Growth antagonism by l-homoserine was reversed by l-lysine, l-threonine, and combinations of l-leucine with l-valine. At the cellular level, these amino acids reduced the amount of acetohydroxy acid synthetase in cells grown with l-homoserine and competed with dl-homoserine-4-(14)C for entrance into the extractable cell pool. l-Isoleucine also antagonized the conversion of l-homoserine to alpha-amino-n-butyric acid. Available data indicated that the effect of l-homoserine was related to its conversion to alpha-amino-n-butyric acid which subsequently inhibited growth.