The thyrotropic cells of the guinea pig pituitary

Summary Three different immunocytoenzymatic techniques were used to identify and characterize the thyrotropic cells in the pituitary of normal guinea pigs at the ultrastructural level (superimposition technique, immunocytochemical technique using P.A.P. and indirect immunohistoenzymatic method before embedding).These cells are characterized by a dark cytoplasm with granules ranging from 1500 to 2000 Å in diameter. The appearance of these granules is very variable: some display a marked electron density and are homogeneous but some have a less marked electron density with a more electron dense peripherally situated region.The TSH molecules are essentially confined to the granules but when the immunocytochemical reactions are carried out before embedding, positive staining is also seen in the cytoplasm and the outer surface of most of the rough endoplasmic reticulum membranes. These results are discussed.We thank D. Quief for technical assistance. This work was supported by a grant from U.E.R. III LilleAttaché de Recherche INSERM     

Effects of guinea pig vasoactive intestinal peptide on the isolated perfused guinea pig heart

The pharmacological effects of guinea pig vasoactive intestinal peptide (VIP) were studied in isolated perfused guinea pig hearts. Bolus injections of VIP produced a dose-dependent tachycardia that was not affected by atenolol. A decrease in amplitude of ventricular contractions occurred in response to all doses of VIP. This response was preceded by a small increase in amplitude in 3 of 6 hearts at the highest dose. VIP produced a decrease in perfusion pressure which was prominent after coronary tone was elevated with [Arg8]-vasopressin. The present findings support speculation that VIP may have a role in the regulation of heart rate and coronary blood flow.     

Effects of maternal administration of diethylstilbestrol and estradiol on the newborn guinea pig

The subcutaneous injection of diethylstilbestrol (2.5 micrograms/day) into pregnant guinea pigs from the 28th or 40th day to term resulted in an accelerated tempo of differentiation of the genital tract of the female offspring at birth, as well as intense estrogenic stimulation. Estradiol (50 micrograms per day) injected over the same period caused insignificant estrogenic stimulation in the newborn. The normal embryogenesis of the genital tract is described and a pattern of caudocranial differentiation identified. The normal genital tract is described as a basis for the analysis of results in the newborn. Comparative studies in other animals are discussed.     

Intravesical BCG administration in the guinea pig

Intravesical BCG administration is used as an adjuvant therapy after transurethral resection for superficial bladder cancer in man. The mechanisms of its antitumor activity are not known. The aim of this study was to characterize the histomorphological changes in various organs of the guinea pig after intravesical BCG administration. The BCG preparation used was BCG-RIVM, a Dutch BCG preparation. Instillations were performed in previously undamaged bladders weekly for 6 consecutive weeks and lasted 30 min or 1 h. Different doses were used ranging from 10³ culturable particles (c.p.) to 5 × 10⁷ c.p. of BCG. After 6 weeks, the animals were killed and postmortem examination was performed. The bladder wall, retroperitoneal lymph nodes, spleen, liver, lungs and distant lymph nodes were examined histologically. The BCG therapy, with a dose of 10₆ culturable particles and higher, induced an inflammatory reaction consisting of mononuclear infiltrates in the subepithelial tissue of the bladder wall. In approximately 50% of the animals investigated, the infiltrates were accompanied by noncaseating granulomatous lesions indicated by the presence of epithelioid cells. In general, the epithelial layer of the bladder showed no visible alterations. Similarly, a granulomatous inflammatory reaction was observed in the first retroperitoneal (iliac) lymph nodes draining the bladder. Granulomatous lesions were occasionally also present in liver and lung. In three of the 29 animals investigated, lesions were present both in liver and lungs, and in two of these three animals a granulomatous reaction was observed in the spleen and distant lymph nodes indicating a generalized inflammatory response induced by BCG. No microorganisms were detected by Ziehl-Neelsen (ZN) staining or culture in L?wenstein-Jensen medium in the first draining (iliac) lymph nodes of the bladder or in the spleen. In this study we found that BCG could induce inflammatory reactions in the bladder wall after its introduction into the previously undamaged bladder. Ulceration of the epithelium covering the mononuclear infiltrates was not observed. Occasionally a generalized inflammatory response to BCG was present in the animals investigated.     

Effects of steroid administration on pituitary luteinizing hormone and follicle-stimulating hormone in ovariectomized pony mares in the early spring: pituitary responsiveness to gonadotropin-releasing hormone and pituitary gonadotropin content

These experiments tested the hypothesis that administration of steroid hormones to ovariectomized (OVX) mares during the vernal transition to the breeding season would influence LH and FSH secretion. Circulating gonadotropin concentrations, response to exogenous GnRH, and pituitary gonadotropin content were monitored. Experiments 1 and 2 were conducted, beginning 10 March, and 3 February, respectively, utilizing a total of 30 long-term OVX pony mares. In experiment 1, mares were administered vehicle (n = 5) or estradiol-17 beta (E2, n = 5, 5 mg/3 ml sesame oil), twice daily for 16 days. Blood samples were collected daily for assessment of circulating LH and FSH concentrations. On Day 10 of treatment, 400 micrograms GnRH were administered to all mares. LH increased significantly over days of treatment in the estradiol-treated group, but pituitary response to GnRH tended to be less than in control mares. Circulating FSH tended to decline over days of treatment in estradiol-treated mares, and the pituitary response to GnRH was significantly reduced. Pituitary LH, but not FSH, was increased on Day 16 of treatment with estradiol. In experiment 2, 20 OVX mares received, twice daily, vehicle (n = 5), E2, n = 5; 5 mg), progesterone (P4, n = 5; 100 mg), or progesterone plus estradiol (P4/E2, n = 5; 100 + 5 mg). Treatment continued for 14 days. GnRH (100 micrograms) challenges were administered on Days 6 and 13 of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)