Inhibition of ovulation, steroidogenesis and collagenolytic activity in rabbits by sulpiride-induced hyperprolactinaemia

Ovulation induced by hCG in rabbits was reduced significantly (P less than 0.005) by sulpiride-induced hyperprolactinaemia. The pre- and post-ovulatory increases in peripheral and ovarian venous progesterone (but not oestradiol or testosterone) were suppressed in the treated animals. The condition of hyperprolactinaemia also prevented the usual changes in 2,4-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg-OH peptidase (DNP-peptidase) and alpha-N-benzoyl-DL-Arg-beta-naphthylamide hydrolase (BANA-hydrolase) activities in follicular tissue that had been stimulated by an ovulatory dose of hCG. These results suggest that inhibition of progesterone production and collagenolytic enzyme activity by sulpiride-induced hyperprolactinaemia may be responsible for the ovulatory dysfunction that occurs when a mammal has a high level of circulating prolactin.     

Identification of (Na,K)ATPase inhibitor in brine shrimp,Artemia salina,as long-chain fatty acids

Summary An inhibitory activity to (Na,K)ATPase was found in cell extracts of the brine shrimp, Artemia salina, irrespective of its developmental stages. Organic solvent extraction together with gas chromatographic analysis reveals that the inhibitory activity is due to long-chain, non-esterified fatty acids and their derivatives. Unsaturated fatty acids, especially with cis-configuration, are more effective in inhibition than saturated ones.Abbreviations ATPase adenosine triphosphatase - EDTA ethylenediamine-tetraacetate - TLC thin-layer chromatography     

Effects of Na+ and K+ on Artemia salina (Na,K)-ATPase solubilized with a zwitterionic detergent, CHAPS

The membrane bound (Na,K)-ATPase prepared from Artemia salina nauplii was solubilized with a zwitterionic detergent, 3[3(cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), and then purified on a Bio-Gel A-1.5 m column in the presence of the detergent. 1) Upon solubilization, both NaCl and KCl protected the enzyme against loss of activity, KCl being more effective than NaCl. 2) Gel filtration of the solubilized enzyme on a Bio-Gel A-1.5 m column in the presence of 5 mM CHAPS resulted in loss of the enzyme activity even when one of the cations was added. Most of the phospholipids in the solubilized enzyme preparation were removed during the gel filtration (delipidation) and 10-25 phospholipids were left on a protomer (alpha beta) of the enzyme irrespective of the cation present during the gel filtration. With the addition of exogenous phospholipids, the activity was restored. The activity of the enzyme delipidated in the presence of KCl was restored to 3-4 times higher than in the case of that delipidated in the presence of NaCl. 3) Relipidation experiments with a fluorescent phospholipid, dansyl phosphatidylethanolamine (Dans-PE), suggested that the enzyme delipidated in the presence of KCl reassociated with phospholipids more firmly than the enzyme delipidated in the presence of NaCl. From these results we concluded that K+ stabilized the (Na,K)-ATPase more effectively than Na+, even when the enzyme was delipidated.     

Application of an enzyme-linked immunosorbent assay for screening of T-2 toxin-producing Fusarium spp.

Culture filtrates of Fusarium species were subjected without clean-up procedures to an indirect competitive enzyme-linked immunosorbent assay with anti-T-2 toxin monoclonal antibody. Fusarium sporotrichioides, F. poae, F. tricinctum, and F. culmorum strains were positive for T-2 toxin, with a minimum detection limit of 5 pg per assay (100 pg/ml of culture filtrate), and the assay data correlated well with the gas-liquid chromatographic data.     

In situ cGMP phosphodiesterase and photoreceptor potential in gecko retina

The possible involvement of phosphodiesterase (PDE) activation in phototransduction was investigated in gecko photoreceptors by comparing the in situ PDE activity with the photoreceptor potential. In the dark, intracellular injection of cGMP into a gecko photoreceptor caused a long-lasting depolarization. An intense light flash given during the depolarization phase repolarized the cell with a short latency comparable to that of the light-evoked hyperpolarizing response, which indicates that the activation of PDE in situ is rapid enough to generate the photoreceptor potential. PDE activity in situ was estimated quantitatively from the duration of the cGMP-induced depolarization, since it was expected that the higher the PDE activity, the shorter the duration. Under steady illumination, the enzyme exhibited a constant activity. On exposure to a light flash, PDE became activated, but recovered in the dark with a time course that was dependent on the intensity of the preceding stimulus. When PDE activity and photoreceptor sensitivity to light were measured in the same cell after a light flash, both recovery processes showed similar kinetics. Theoretical analysis showed that the parallelism in the recovery time courses could be explained if cGMP is the transduction messenger. These results suggest that PDE activation is involved not only in the generation but also in the adaptation mechanisms of the photoreceptor potential.     

Mapping the idiotopes of a monoclonal anti-myoglobin antibody with syngeneic monoclonal anti-idiotypic antibodies: detection of a common idiotope

A panel of syngeneic monoclonal anti-idiotypic antibodies was prepared by immunizing A.SW mice with keyhole limpet hemocyanin-coupled A.SW monoclonal anti-myoglobin (HAL 19, IgG1) and screening the cloned hybridomas for production of IgG2 binding to idiotype but not to certain other anti-myoglobin antibodies of the same subclass in an ELISA. With these antibodies, we identified three nonoverlapping idiotopes, based on three clusters of monoclonal anti-idiotopes that mutually inhibit within each cluster, but not between clusters (Cluster I: S2, S6, S8; Cluster II: S5, S7; Cluster III: S9). Only Cluster II antibodies block the binding of myoglobin to HAL 19 and so identify a binding site-related idiotope(s). Binding of both Cluster II monoclonals (S5 and S7) to Hal 19 is inhibited by a rabbit anti-idiotype that we previously reported detects a common cross-reactive anti-myoglobin idiotope in immune sera. However, only one of these, S7, and not S5, identifies an idiotope that is present on 20 to 30% of A.SW anti-myoglobin antibodies in immune sera and ascites. The panel of syngeneic monoclonal anti-idiotype antibodies also detects new idiotopes not detected by the rabbit anti-idiotype. The development of a panel of syngeneic monoclonal anti-idiotypic antibodies to different clusters of idiotopes on the same antibody molecule, including one that identifies a major common idiotope in immune sera, should allow the analysis of possible idiotype network regulation in vivo and in vitro in a completely syngeneic system.     

Primary structure of heat-stable enterotoxin produced by Yersinia enterocolitica

A heat-stable enterotoxin was isolated and purified from the culture supernatant of $\text{Yersinia enterocolitica}$ by reversed-phase high-performance liquid chromatography. The amino acid sequence of the purified toxin was determined to be as follows: Gln-Ala-Cys(X)-Asp-Pro-Pro-Ser-Pro-Pro-Ala-Glu-Val-Ser-Ser-Asp-Trp-Asp-Cys-Cys-Asp-Val-Cys-Cys-Asn-Pro-Ala-Cys-Ala-Gly-Cys (X: not determined). The C-terminal sequence containing 6 half-cystine residues was highly homologous to that of heat-stable enterotoxin of enterotoxigenic $\text{Escherichia coli.}$