Variations of the effect of insulin on neutrophil respiratory burst. The role of tyrosine kinases and phosphatases.

The priming effect of insulin on the fMLP-induced respiratory burst of mouse neutrophils as well as the involvement of tyrosine protein kinases and phosphatases in this process have been studied. Peritoneal evoked neutrophils of NMRI strain mice were incubated with 0.01-100 nM insulin for 1-60 min at 22, 30, or 37 degrees C and activated by 0.1-50 microM N-formyl-methionyl-leucyl-phenylalanine (fMLP). The production of reactive oxygen species (ROS) by neutrophils was monitored by luminol-dependent chemiluminescence. We found that 125I-labeled insulin binding by mouse neutrophils occurred with saturation and high affinity. Insulin itself did not change the basal level of the ROS production but could modulate fMLP-induced respiratory burst. The effect of insulin depended on temperature and duration of pretreatment of the neutrophils with insulin and the concentration combination of the insulin and fMLP. The tyrosine kinase inhibitor tyrphostin 51 decreased the fMLP-induced respiratory burst significantly. Insulin did not change the fMLP response of neutrophils pretreated with tyrphostin. However, the effect of tyrphostin on the response to 50 microM fMLP was considerably decreased in neutrophils treated with insulin. There was no such effect during activation by 5 microM fMLP, for which the priming effect of insulin was not observed. Insulin did not increase the fMLP-induced respiratory burst in neutrophils treated with the protein phosphatase inhibitors orthovanadate and pyrophosphate. If the inhibitors were added after insulin, the combined effect was nearly additive. It is possible that priming by insulin of the fMLP-induced respiratory burst is triggered by tyrosine phosphorylation, realized with its participation, and involves the signaling pathways initiated by tyrosine phosphorylation but subsequently is not dependent on the latter. The role of protein phosphatases in priming by insulin is of little importance. The data indirectly confirm the idea that priming of the neutrophil respiratory burst is a result of crosstalk of signaling pathways of the insulin and fMLP receptors with the participation of tyrosine phosphorylation.

Structural and functional similarity between Yersinia pestis capsular protein Caf1 and human interleukin-1 beta.

A comparative study of the structural and functional properties of recombinant Yersinia pestis Caf1 and human IL-1beta was performed. According to Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) data, IL-1beta and Caf1 are typical beta-structural proteins. Neither protein interacts with the hydrophobic probe ANS (8-anilino-1-naphthalenesulfonate) under physiological conditions. Specific binding of Caf1 [K(d) = (5.4 +/- 0.1) x 10(-10) M] to interleukin-1 receptors (IL-1Rs) on the surface of finite mouse fibroblasts (line NIH 3T3) was observed. Caf1 is able to inhibit high-affinity binding of (125)I-labeled IL-1beta to NIH 3T3 cells, and in the presence of Caf1, the binding of [(125)I]IL-1beta is characterized by a K(d) of (2.0 +/- 0.3) x 10(-9) M. Caf1 binding to IL-1R could reflect adhesive properties of the capsular subunits responsible for the contact of bacteria with the host immunocompetent cells. In its turn, this may represent a signal for the initiation of the expression and secretion of the proteins of Y. pestis Yop virulon. Thus, these results help to explain the importance of Caf1 in the interaction of Y. pestis with the host immune system.

[The comparative characteristics of the immunomodulating properties of protein A from Staphylococcus aureus of different origins]. / Sravnitel'naia kharakteristika immunomoduliruiushchikh svoistv belka A Staphylococcus aureus razlichnogo proiskhozhdeniia.

The immunomodulating properties of highly purified staphylococcal protein A and its analog obtained by gene engineering techniques have been compared with those of commercial preparations. The comparison has shown that the differences observed in this investigation may be explained by the presence of admixtures of staphylococcal nature in commercial preparations. The preparations of highly purified staphylococcal and recombinant protein A stimulate humoral immune response and the processes of phagocytosis and do not show mitogenic activity with respect to T cells. The conclusion on the identity of the immunomodulating activity of the preparations of natural and recombinant protein A has been made.

[Conformation changes in the mechanism of cryoprecipitation of human monoclonal immunoglobulin M]. / Izuchenie konformatsionnykh izmenenii v mekhanizme kriopretsipitatsii monoklonal'nogo immunoglobulina M cheloveka.

The role of conformational changes in the mechanism of cryoprecipitation of human monoclonal immunoglobulin M (IgM) was studied. It was demonstrated that the variable moiety of the Fab-region of cryo-IgM has a site which comprises 5 to 6 charged amino acid residues. This site is responsible for intermolecular electrostatic interactions which lead to the formation of a precipitate with a decrease in temperature. This interaction is cooperative and stabilized by dipole molecules of H2O. The chain growth during aggregation is nuclear. The primary nucleus contains three IgM macromolecules. stability of the three-molecule nucleus is provided for by 16--17 intermolecular links. Using circular dichroism and fluorescent methods, it was found that the formation of a cryoprecipitate is accompanied by ionic pair release and conformational changes.

[The role of intermolecular electrostatic cooperative interactions causing cryoprecipitation of human monoclonal immunoglobin M]. / Izuchenie roli mezhmolekuliarnykh élektrostaticheskikh kooperativnykh vzaimodeistvii, obuslavlivaiushchikh kriopretsipitatsiiu monoklonal'nogo immunoglobulina M cheloveka.

A chemical modification of carboxylic groups of monoclonal human cryoglobulin M has been studied. The modification by a chromophoric carbodiimide was accompanied by complete loss of IgM cryoprecipitating properties. The number of carboxylic groups important for biological activity was estimated by the Tsou method and found to be 2. The cryoprecipitation dependence on ionic strength has been investigated and the number of ions per binding site isolated upon formation of intermolecular ion couples has been estimated. Mechanism of cryoprecipitation stipulated by intermolecular cooperative electrostatic interactions is proposed.

Effect of chemical modification on the cryoprecipitation of monoclonal human cryoglobulin M.

The effect of the chemical modification of lysine, histidine, arginine, tyrosine, tryptophan residues and carboxylic groups on the cryoproperties of monoclonal human cryoglobulin M has been studied. The modification of 35-40 lysine residues and that of 42-45 arginine residues in the molecule of cryo-IgM has been shown to result in practically complete inhibition of the cryoprecipitation. The same effect is observed on the modification of 60 histidine residues per molecule and on modification of 50 or 51 carboxylic groups. At the same time the modification of practically all the reagent-exposed tryptophan (10 residues per molecule) and tyrosine residues (55 residues per molecule) does not lead to any noticeable decrease in the cryoprecipitation. The conformations of the modified and native proteins are identical according to the circular dichroism data.

[Effect of diazepam and fenazepam on neural regulation of cerebral circulation]. / Vliianie diazepama i fenazepama na nervnuiu reguliatsiiu mozgovogo krovoobrashcheniia.

Diazepam and phenazepam produce a depressant action on reflex changes in the cerebral blood flow and increase the tone of cerebral vessels, induced by stimulation of the afferent fibers of A and C groups of somatic nerves. The drugs potentiate the processes of central inhibition of tonic sympathetic activity and of reflex somatosympathetic responses along with the decreased amplitude and potential frequencies on the EEC. Phenazepam exerts a more pronounced depressant effect on the nervous regulation of cerebral circulation. GABA-ergic mechanisms are suggested to participate in the action of diazepam and phenazepam on the central regulation of cerebral circulation.