Stimulation of nonspecific resistance by thymopentin and its analogs against Leishmania donovani infection in hamsters

Thymopentin and its analogs have been synthesized by the solution phase method of peptide synthesis and evaluated for their prophylactic efficacy against L. donovani infection in hamsters. Thymopentin and some of the analogs were found to stimulate nonspecific resistance of the host against Leishmania donovani infection in hamsters.     

Stimulation of hepatocyte DNA synthesis by neurotensin

Epidermal growth factor and transforming growth factor alpha stimulated DNA synthesis in primary cultures of adult rat hepatocytes. Neurotensin amplified epidermal growth factor-stimulated or transforming growth factor alpha-stimulated DNA synthesis by three- to eightfold. Neurotensin by itself did not stimulate DNA synthesis. Amplification of DNA synthesis by neurotensin was observed as low as 10^?10 M, and it was increased in a dose-dependent manner with maximal effects at 10^–8 M. These results were obtained when hepatocytes were cultured in Williams' medium E, but not in Leibovitz L-15 medium, suggesting that a minor component(s) in the medium is required for hepatocytes to fully respond to neurotensin. Neurotensin effect on DNA synthesis was observed not only in normal rat hepatocytes but also in partially hepatectomized rat hepatocytes, although its effect was stronger in normal hepatocytes. Amplified DNA synthesis was inhibited by transforming growth factor β. Secondary mitogens (co-mitogens) such as insulin, vasopressin, or angiotensin II interacted additively with low concentrations of epidermal growth factor as well as with neurotensin. Neurotensin-related peptides such as kinetensin or neuromedin-N, which was released from blood plasma by pepsin digestion, did not have this amplifying effect on DNA synthesis at any concentrations tested. Neurotensin mRNA was found in several organs including brain and intestine, but not liver. These results suggest that neurotensin can be regarded as a new secondary mitogen and that it may be involved in cell proliferation, including regenerating liver as a gastrointestinal hormone and/or a neurotransmitter. © 1994 Wiley-Liss, Inc.     

Stimulation of rat pituitary tumoral cell proliferation in vitro by tetra- and pentagastrin.

The effects of the active gastrin fragments, penta- and tetragastrin on the incorporation of tritiated thymidine into the rat pituitary tumoral cells were investigated in vitro. The significant stimulation of 3H-thymidine incorporation was observed as an effect of the investigated substances. The putative role of gastrin as an autocrine growth factor active in pituitary tumorigenesis was discussed.     

Conformation states of thymopentin and its synthetic analogs

Spatial structures of the biologically active fragment Arg-Lys-Asp-Val-Tyr of tymopoetin (tymopentin) and its synthetic analogs: [Lys1-Arg2]-, [Glu3]- and [Gly3] have been investigated by theoretical conformational analysis. These results indicate that the conformational properties of fragments are represented in aqueous solution by five different backbone forms.     

The ways of realization of high specificity and efficiency of enteropeptidase

Comparative substrate analysis of full-length bovine enteropeptidase and trypsin, bovine and human enteropeptidase light chains was performed using model N-terminal dodecapeptides corresponding to wild-type human trypsinogen and pancreatitis-associated mutant trypsinogens K23R and D22G. The substitution of Lys residue by Arg at P1 leads to 2-fold increase in the efficiency of enteropeptidase hydrolysis; the absence of the negatively charged residue at P2 reduces the efficiency of such hydrolysis by two orders of magnitude. The difference in efficiency of peptide chain hydrolysis after Lys/Arg residues by enteropeptidase compared to trypsin is equal to the difference in hydrolysis by serine proteases of different primary specificity of their specific substrates.     

Evaluation of vaccinal immunogenesis by the peroxidase method

The possibility of evaluating functional immunomorphogenesis in the course of the vaccinal process after the injection of conjugated and live brucellosis vaccines, as well as conjugated plague antigen and Yersinia pestis strain EV, to guinea pigs has been shown by means of the direct and two-layer variants of the immunoperoxidase assay. The dynamics of the accumulation of globulin-producing cells in the immunocompetent organs and the time course of immunoglobulin titers in the peripheral blood after the injection of live and conjugated vaccines have been followed up. These data may be used for the morphological evaluation of approved preparations.     

Effect of beta-adrenoreceptor stimulation on gastric secretion stimulated by histamine, acetylcholine, and pentagastrin

In chronic experiments on dogs with gastric and duodenal fistulas and catheters implanted into the jugular vein, it was established that the beta-adrenoagonist novodrin inhibits gastric secretion stimulated with acetylcholine or pentagastrin but does not alter secretion stimulated with histamine. The inhibitory effect of novodrin on gastric secretion is a consequence of its direct action on beta-adrenoreceptors of the gastric mucosa. The scheme demonstrating interrelations of beta-adrenoreceptors to acetylcholine, gastrin and histamine is offered.     

Effect of neurotensin injections into caudate nuclei on realization and extinction of conditioned motor reflex in rats

It was shown that neurotensin microinjections into the caudate nuclei facilitated of a conditioned reflex but not affected its realization. Besides, neurotensin was shown to have a positive aftereffect on extinction. Motor activity of rats in the "open field" was augmented after neurotensin administration. A conclusion was drawn that the functional effect of neurotensin administration into the caudate nuclei is connected with the normalization of the motivational and emotional state of an animal rather than with the regulation of the motor function.