Effects of zeranol on in vitro growth hormone release by lamb and rat pituitary cells.

A series of experiments was conducted to evaluate the effect of zeranol on release and synthesis of growth hormone (GH) by anterior pituitary cells established in either static or continuous flow cultures. Young adult male rats, slaughter-age lambs and juvenile lambs were used as sources of pituitary cells. In static primary cell cultures, no consistent effect of zeranol at 10(-7), 10(-9) or 10(-11) M was demonstrated by either rat or ovine cells. Rat pituitaries established in perifusion culture chambers showed no repeatable response to zeranol. Dissociated cells from lambs established in perifusion culture, however, had significant increases in release of GH in response to 37% of zeranol pulse exposures. When dissociated cells from juvenile lamb pituitaries were used, up to 10-fold increases in GH release consistently were measured within minutes of exposure to zeranol.

Stimulation of pig growth performance by porcine growth hormone: determination of the dose-response relationship.

The present study was undertaken to determine the relationship between dose of porcine growth hormone (pGH) and growth performance of pigs. Porcine GH was administered daily for 35 d [buffer-injected control = (C); 10 micrograms/kg body weight (BW) = (L); 30 micrograms/kg BW = (M); 70 micrograms/kg BW = (H)] to barrows (initial wt = 50 kg). Growth rate was significantly increased by pGH (14% for H dose vs C). Feed efficiency was increased in a dose-related manner (L = 7%, M = 10%, H = 17%) by pGH. There was a concurrent change in carcass composition of pGH-treated pigs. The H dose of pGH decreased the percentage of carcass lipid by 25% (P less than .05). Muscle mass was significantly increased in H vs C pigs (31 vs 26 kg). Serum insulin-like growth factor 1 (IGF-1) concentration increased in a manner that was linearly related to the pGH dose (r = .87). No antibodies to pGH were detected in any of the pigs. In summary, these results extend our earlier findings that pGH increases growth performance markedly. Based on the present findings it appears that the maximally effective dose of pGH is greater than 70 micrograms.kg BW-1.d-1 since several indices of the growth-promoting and metabolic effects of pGH (% carcass protein, % carcass lipid and feed efficiency) had not plateaued.

Stimulation of pig growth performance by porcine growth hormone and growth hormone-releasing factor.

The current study was undertaken to determine the effects of human growth hormone-releasing factor [hpGRF-(1-44)-NH2] on growth performance in pigs and whether this response was comparable to exogenous porcine growth hormone (pGH) treatment. Preliminary studies were conducted to determine if GRF increased plasma GH concentration after iv and im injection and the nature of the dose response. Growth hormone-releasing factor stimulated the release of pGH in a dose-dependent fashion, although the individual responses varied widely among pigs. The results from the im study were used to determine the dose of GRF to use for a 30-d growth trial. Thirty-six Yorkshire-Duroc barrows (initial wt 50 kg) were randomly allotted to one of three experimental groups (C = control, GRF and pGH). Pigs were treated daily with 30 micrograms of GRF/kg body weight by im injection in the neck. Pigs treated with pGH were also given 30 micrograms/kg body weight by im injection. Growth rate was increased 10% by pGH vs C pigs (P less than .05). Growth rate was not affected by GRF; however, hot and chilled carcass weights were increased 5% vs C pigs (P less than .05). On an absolute basis, adipose tissue mass was unaffected by pGH or GRF. Carcass lipid (percent of soft-tissue mass) was decreased 13% by GRF (P less than .05) and 18% by pGH (P less than .05). Muscle mass was significantly increased by pGH but not by GRF. There was a trend for feed efficiency to be improved by GRF; however, this was not different from control pigs. In contrast, pGH increased feed efficiency 19% vs control pigs (P less than .05). Chronic administration of GRF increased anterior pituitary weight but did not affect pituitary GH content or concentration. When blood was taken 3 h post-injection, both GRF- and pGH-treated pigs had lower blood-urea nitrogen concentrations. Serum glucose was significantly elevated by both GRF and pGH treatment. This was associated with an elevation in serum insulin. These results indicate that increasing the GH concentration in blood by either exogenous GH or GRF enhances growth performance. The effects of pGH were more marked than for GRF. Further studies are needed to determine the optimal dose of GRF to administer in growth trials and the appropriate pattern of GRF administration in order to determine whether GRF will enhance pig growth performance to the extent that exogenous pGH does.

Stimulation of swine growth by porcine growth hormone.

Highly purified porcine growth hormone (pGH; USDA-B1) was administered by im injection (22 micrograms X kg body weight-1 X d-1) to rapidly growing Yorkshire barrows for 30 d. Growth hormone significantly increased growth rate (10%), feed efficiency (4%), cartilage growth and muscle mass. However, pGH did not affect carcass adipose tissue mass. Intramuscular lipid content of the longissimus was increased 50% by pGH administration. Plasma pGH concentration was elevated (7- to 11-fold) for 3 to 5 h post-injection. Chronic administration of pGH depressed pituitary GH content and concentration approximately 45%. No GH antibodies were detected in the plasma of GH-treated swine. Plasma somatomedin-C concentration was increased 55% by GH treatment 3 h post-injection. Plasma glucose and insulin concentrations were both significantly increased in GH-treated swine, suggesting that the animals had developed a state of insulin resistance. Plasma-free fatty acid concentration tended to be higher in GH-treated animals. Treatment of swine with pGH significantly decreased plasma blood urea nitrogen. Assessment of animal health during the trial and postmortem indicated that pGH administration did not have any adverse effects. In summary, treatment of young, rapidly growing swine with pGH stimulated growth performance without affecting animal health or inducing the production of GH antibodies.

Receptor-dependent and independent degradation of insulin by isolated swine adipocytes at 37 C.

Insulin binding and degradation were measured at 37 C in isolated swine adipocytes. In preliminary experiments, binding decreased rapidly with increasing incubation time. This was associated with a marked increase in insulin degradation. Insulin binding was suppressed by some lots of bovine serum albumin (BSA), which suggests that some commercial preparations of BSA are contaminated with insulin-like molecules. In adipocyte suspensions, greater than 90% of the insulin degraded was due to a nonreceptor mediated process (i.e., insulin degrading activity present in the media). Despite the presence of insulin degrading activity in the media the cells were metabolically (as judged by lipogenic capacity and lactic dehydrogenase activity) and morphologically (greater than 98% excluded trypan blue) intact indicating that the cells were not leaking during the incubation. In subsequent experiments it was found that the specific step associated with transfer of cells during adipocyte isolation resulted in the release of insulin degrading activity. Implementation of a 30-min preincubation and washing sequence after adipocyte isolation removed the media insulin degrading activity, resulting in a marked reduction (approximately 70%) of insulin degradation by adipocyte suspensions. As a result of this modification, binding of tracer quantities of insulin attained steady-state binding conditions and maintained this for 2 h. These results demonstrate that techniques can be used to minimize nonreceptor mediated insulin degradation in adipocyte suspensions. As a result in vitro studies can be conducted that measure insulin binding and biological action in swine adipocytes at physiological temperatures.

Sarcocystis sp. in the eastern cottontail (Sylvilagus floridanus).

Sarcocystis sp. was observed in 100 of 185 (54.1%) Eastern cottontails (Sylvilagus floridanus) examined in Pennsylvania over a three year period. Gross and histologic examination commonly revealed cysts in skeletal muscle of the fore and hind legs, flanks and loins. Two rabbits had cysts in esophageal skeletal muscle. Host response to Sarcocystis sp. is described. Adult rabbits had a significantly greater rate of infection (69.3%) than juveniles (20.7%) (P less than 0.01).

Gastrointestinal parasites of the eastern cottontail (Sylvilagus floridanus) in central Pennsylvania.

During a 3 year period, 186 eastern cottontails (Sylvilagus floridanus) were trapped from two areas and examined for helminth and protozoan parasites. Fecal samples from 139 were evaluated for coccidia and helminth ova. Nine species of coccictia were identified: Eimera audubonii, E. azul, E. environ, E. honessi, E. maior, E.minima, E. neoirresidua, E. neoleporis, and E. sylvilagi. Ova from 5 helminth species were found: Cittotaenia sp., Hastilesia tricolor, Passalurus sp., a trichostrongyle-type nematode species, and Trichuris sp. Five helminths were recovered from stomachs and small intestines: Cittotaenia sp. H. tricolor, Obeliscoides cuniculi,, Passalurus ambiguus, and Trichostrongylus calcaratus.

Histologic evaluation of the effects of diethylstilbesterol and zeranol on certain lamb tissues.

Forty-eight lambs with equal numbers of rams, ewes, and wethers were used in a growth and metabolism trial. Within each sex, equal numbers were used as controls, and implanted with zeranol or deithylstillbestrol (DES) or both. The lambs were slaughtered 44 days after implanting and the effects of the different implants (or in combination) on certain endocrine glands, urogenital tracts, and other selected tissues were determined. All animals given implants had adrenal cortical hyperplasia. Thyroid gland activity was depressed by DES implants in wethers, and by the combination of zeranol and DES in wethers and rams. Changes in the urogenital tracts of DES-implanted lambs, including the urethra, seminal vesicle, epididymis, testis, and uterus, were similar to those observed following treatment with exogenous estrogens. The results of this evaluation confirm that DES has higher estrogenic activity than zeranol. When these two compounds were used in combination, their estrogenic effects were additive.

Some hematological and histopathological effects of the alkaloids gramine and hordenine on meadow voles (Microtus pennsylvanicus).

Meadow voles (Microtus pennsylvanicus) were used to evaluate the relative toxicity of the alkaloids, gramine and hordenine, which are present in reed canarygrass (Phalaris arundinacea) and to assess their effects on the quality of this grass as a forage. One hundred and twenty meadow voles, 31 days of age, were fed gramine (0, 0.125, 0.25, or 0.5% of a nutritionally complete diet) or hordenine sulfate (0, 0.15, 0.31, or 0.62% of the diet) for 21 days. The effects of treatment on growth, mortality, hematology, blood chemistry, and histology of body organs were examined. Approximately one-third of the voles died when fed either 0.25 or 0.50% gramine. Voles that survived on gramine diets had kidney lesions, glycosuria, higher intakes (P less than 0.05), and lower weight gains (P less than 0.01) than control animals. Voles fed 0.25 and 0.50% gramine had increased circulating reticulocyte levels (P less than 0.01) and those fed 0.125% gramine had higher alkaline phosphatase activity (P less than 0.05) than the control voles. Hordenine did not affect vole diet intake, weight gain, or rate of mortality. Voles fed hordenine developed kidney lesions and glucose was detected in the urine of 62% of these animals. Gramine was more toxic than hordenine on a molar equivalent basis.

Eimeria azul sp. n. (protozoa: Eimeriidae) from the eastern cottontail, Sylvilagus floridanus, in Pennsylvania.

Eimeria azul sp. n. is described from the cottontail rabbit, Sylvilagus floridanus, in central Pennsylvania. The oval oocysts are 19.5--27.0 micrometer by 15.0--19.0 (mean - 22.9 X 16.7 micrometer). The fusiform sporocysts are 7.8--14.0 micrometer by 3.3--6.5 micrometer (mean = 11.8 X 5.8 micrometer). A Stieda Body is present. There is no micropyle, oocyst residuum or polar granule. The sporocyst has a residuum which is variable in appearance. The oocysts are characterized by a blue tint when viewed with an apochromatic objective lens.

Pathologie changes in endocrine glands and certain other tissues of lambs implanted with the synthetic growth promotant zeranol.

As doses of zeranol implants (0 (control), 12, 24, 48, and 96 mg) were increased, there were increased reaction and activity in target organs (such as urogenital tract and mammary, adrenal, hypophyseal, and thyroid glands) of castrated male sheep (wethers). Hyperplasia and transitional and squamous transformation in the prostate were mild (1+) in the wethers given 12- and 24-mg doses, moderate to marked (2.5+) in the wethers given 48-mg doses, and severe (4+) in the wethers given 96-mg doses. Papillary proliferation and fibrosis increased correspondingly in the seminal vesicle. Changes in the distal penile urethra increased from papillary hyperplasia in the wethers given a 24-mg dose to 100% squamous transformation in the wethers given a 96-mg dose. Mammary gland development was noticeable in the wethers given a 24-mg dose and increased thereafter to progressive alveolar growth and secretory activity in the wethers given 48- and 96-mg doses. Along with a progressive increase of adrenal gland weight and adrenal gland/thyroid gland ratios over the controls, the principals had hypertrophy and hyperplasia of the adrenal cortex. Mean adrenal cortex widths for control wethers and wethers given 24-, 48-, and 96-mg doses were 2,089, 2,140 (adjusted value, 2,194), 2,416, and 2,425 mum, respectively. Mean adrenal gland weights for control wethers and wethers given 12-, 24-, 48-, and 96-mg doses were 2.50, 2.61, 2.53, 2.70, and 2.78 g. respectively. Hyperplasia (nodule formation) plus exhaustive and pyknotic changes of the adrenal cortex increased similarly with increasing zeranol dose. After the thyroid gland weights decreased (2.19, 2.04, 2.00, and 1.72 g, respectively, for control wethers and wethers given 12-, 48-, and 96-mg doses), secretory activity of thyroid epithelial cells decreased. In the glandular portion of the hypophysis, secretory activity and proliferation of eosinophilic cells increased with the larger zeranol doses (48 and 96 mg). There was a corresponding decrease in the number of basophils. These changes are consistent with increased somatotropin and adrenocorticotropin secretion and decreased thyrotropin secretion. Muscle and ligament structures appeared looser and widened in the wethers given the 96-mg dose, and fat cell formation was increased in the muscles along ligament muscle junctions.