Relationship between pituitary responsiveness to Gn-RH and number of Gn-RH-binding sites in pituitary glands of beef cows

Changes in the ability of Gn-RH to induce gonadotrophin release with time after synchronization of oestrus was determined in 4 groups of 6 cows each. Cows were given Gn-RH at 40-min intervals for 6 h beginning at -24, 0, 18 or 36 h (time 0 = removal of progestagen implant). Changes in concentration (ng/ml) of serum LH after Gn-RH averaged 2.9, 6.2, 6.4 and 33.4, whereas serum FSH averaged 25.7, 35.8, 35.8 and 97.3. Thus the responsiveness of the pituitary to Gn-RH had increased by 36 h after implant removal. Other groups of cows subjected to the same synchronization scheme were slaughtered at 0 h, 24 h or at various times after onset of oestrous behaviour. Gn-RH binding to crude pituitary membrane preparations was assessed. There was no apparent change in the affinity constant of Gn-RH-binding sites with time after synchronization. The number of Gn-RH-binding sites remained unchanged until the period of oestrus when a significant decline with time was detected. We conclude that the increase in pituitary responsiveness to Gn-RH that occurs before the preovulatory gonadotrophin surge was not directly associated with changes in number or affinity of pituitary Gn-RH-binding sites in crude pituitary membrane preparations.

Selective suppression of the cytotoxic T cell response to influenza virus in mice

Mice injected with inactivated (UV light-irradiated) influenza virus produce specific antibody, become sensitized for a delayed-type hypersensitivity reaction, but do not generate specific cytotoxic T (Tc) cells. If injected 4-5 days later with infectious virus, the formation of Tc cells is suppressed by > 90%. If A strain viruses are used, the suppression observed is cross-reactive within A strain viruses but does not extend to B/LEE or to Sendai virus. Serum from mice injected with UV-irradiated virus contains antibodies which on adoptive transfer can inhibit Tc cell formation when infectious homologous virus is used to challenge the recipients. Spleen cells from the same mice, upon adoptive transfer, also inhibit (50-70%) Tc cell formation if transferred within 24 h of injection of infectious virus, and the specificity pattern observed is cross-reactive within A strains. The activity of the cells mediating suppression is destroyed by monospecific anti-Thy-1.2 antibody and complement. The immune cells require I region sharing between donor and recipient mice for their suppressor activity to be effective. (There is also a partial requirement for K, D region sharing, but the possible rejection of transferred cells is not excluded.) Dilution assays in which clonal expansion of Tc precursors is used to estimate their frequency and the presence of T helper (Th) cells indicate that suppressed mice possess Tc precursors and primed cells which, upon restimulation, act as Th cells. Furthermore, injection of irradiated Th cells with inactivated virus does not significantly reduce the ensuing suppression.

Bovine prolactin, TSH, T and T concentrations as affected by tall fescue summer toxicosis and temperature

Serum concentrations of prolactin (PRL), thyrotropin (TSH), thyroxine (T4) and triiodothyronine (T3) were compared between Holstein calves fed a toxic fescue (G1-307) and Holstein calves fed a less toxic fescue (G1-306) at one of three environmental temperatures (low, 10 to 13 C; medium, 21 to 23 C; high, 34 to 35 C). Three calves were assigned to each treatment combination, and hormone concentrations were determined before (basal) and after thyrotropin-releasing hormone (TRH) was injected at 15 microgram/100 kg body weight via jugular cannula. Calves fed the toxic G1-307 had lower basal PRL concentrations than those fed G1-306 (1.8 +/- .1 vs 6.0 +/- 1.2 ng/ml). Increasing ambient temperature increased basal PRL levels in calves fed G1-306 (i.e., low [2.3 +/- .3] < medium [3.6 +/- .9] < high [12.1 +/- 1.3 ng/ml]) but not in calves fed G1-307 (i.e. low [1.8 +/- .1] = medium [2.0 +/- .1] = high [1.6 +/- .1]). Similarly, after TRH injection, PRL release was greater in calves fed the less toxic G1-306 (35.7 +/- 5.2 ng/ml) than in those fed G1-307 (5.6 +/- .6 ng/ml) and was positively affected by temperature (i.e., low [6.9 +/- 1.2] < medium [18.8 +/- 5.6] < high [36.3 +/- 5.9 ng/ml]). In contrast, basal and TRH-induced TSH concentrations were unaffected by temperature or fescue. However, T3 (time 0) was inversely related to temperature (1.06 +/- .1, 1.40 +/- .1 and 1.87 +/- .2 ng/ml for high, medium and low temperature, respectively). After TRH injections, T3 increased linearly and at the same rate (.007 ng/ml/min) at all temperatures, but T4 concentrations increased only in low temperature groups. Neither T4 nor T3 concentrations were affected by forage fed. We conclude that some factor(s) in toxic fescue inhibits PRL secretion, especially at high temperature, an environmental condition closely associated with fescue summer toxicosis in cattle. Increased body temperature and respiration rates associated with fescue summer toxicosis apparently are not mediated by TSH or thyroid hormone secretion.

Tumor-associated antigens of rat moloney sarcoma cells. II. Cytosol antigens

Rat Moloney sarcoma cells (MST) were pulsed with 35S-L-methionine for 10 and 60 min and lysed by vortexing in 0.5% deoxycholate, 0.5% NP40, 0.02 M Tris, 0.05 M NaCl, pH 7.5, for 30 sec. The lysate was centrifuged at 16,300 X G for 10 min and the supernatant was co-precipitated with Ig fractions of normal BN serum, normal Lewis serum, BN antiserum to Moloney sarcoma cells (BNaMST), BN antiserum to tumor-associated antigens (BNaTAA), BN antiserum to murine leukemia virus (BNaMuLV), BN antiserum to p30 (BNap30), BN antiserum to gp70 (BNagp70), Lewis antiserum to BN (LeaBN), and BN antiserum to BC5 tumor (BNaBC5). With BNaTAA and BNaMST, a cytoplasmic TAA with m.w. 85,000 was detected. In addition, BNaTAA detected three other species of cytoplasmic TAA with m.w. 220,000, 170,000 and 39,000.

Serum thyrotropin, thyroxine, and tri-iodothyronine in dairy cows fed varying amounts of iodine

The objective was to determine whether dairy cows fed supplemental iodine daily at 2.5 or 5.0 mg per kg body weight for 49 wk had altered thyroid status relative to controls fed no supplemental iodine. Average daily dose of iodine was 1.6 and 3.3 g. Iodine as ethylene diamine dihydriodide was fed to Holstein cows beginning at 8 to 10 wk of lactation, for the remainder of that lactation, through the dry period, and into the next lactation. On day 341 after onset of iodine feeding, each cow was injected intravenously with 15 microgram thyrotropin releasing hormone per 100 kg body weight. Thyrotropin in jugular blood collected before injection of releasing hormone averaged 7.6, 6.1, and 8.2 ng/ml for cows given 0, 2.5, and 5.0 mg iodine/kg body weight; there were no differences between means. Releasing hormone increased thyrotropin, thyroxine, and tri-iodothyronine in serum of all cows, but increases were not affected by quantity of dietary iodine.

Long-term incubation of rat thymus cells: Cytolytic actions of glucocorticoids in vitro

A system has been developed for long-term incubation of rat thymus cells in sus pension in a chemically defined medium consisting of medium 199 and methylcellulsoe. With this system it is possible to study quantitatively the full time-course of glucocorticoid actions, from the early inhibitory effects on glucose uptake to the slow cytolytic effects. Cells incubated under these conditions preserve their sensitivity to the inhibitory effects of cortisol on glucose uptake for al least 12 h. Glucocorticoids at physiological concentrations lead to cytolysis (measured by reduction in viable cell counts determined by a modification of the pronase-cetrimide method) by 12 h incubation time. The cytolytic effect exhibits well-defined dose-response relationships and specificity for glucocorticoids. By 24 h,cortisol at 10(-6)M consistently reduces the total cell count by about 15%, and the viable cell count by about 40%. Cortisol is active down to 10(-7) M. Dexamethasone is roughly 10 times as active as cortisol, and cortisone completely inactive. Cortexolone is slightly active, but also shows antiglucocorticoid activity by its ability to block the action of cortisol. Under anerobic conditions in Medium 199, no inhibitory effect of cortisol is observed on glucose uptake.

Deoxycytidine transport in the presence of a cytidine deaminase inhibitor and the transport of uracil in Escherichia coli B

Tetrahydrouridine, a cytidine deaminase inhibitor, prevents periplasmic degradation of deoxycytidine by Escherichia coli B. It does not inhibit deoxycytidine transport and therefore allows an accurate determination of deoxycytidine transport. Data obtained using tetrahydrouridine show that deoxycytidine is transported in E. coli B as the intact nucleoside by an active transport process, with a K-m of 6 times 10-minus 6 M. Cytidine and deoxyadenosine inhibit transport competitively, whereas guanosine has no effect on transport. Arsenate or KCN greatly reduces transport. In a mutant resistant to the nucleoside antibiotic, showdomycin, the active transport of deoxycytidine is lost, and residual slow uptake occurs by passive diffusion. Uracil is accumulated in E. coli B by an active transport process with a K-m of 5 times 10-minus 7 M.