[Automated calculation of the RD parameter in euglycemic insulinemic clamp]. / Avtomatizirovannyi raschet parametra RD v éuglikemicheskom insulinemicheskom klémpe.

The authors proposed a new analytical approach to a search for the RD parameter in euglycemic insulinemic clamp which imparts a rate to glucose infusion. Two diabetic patients were investigated (RD parameter in the first case was determined by intuition, and in the second case--on the basis of mathematical iterative formulas). The analytical approach permitted a two-fold reduction of the time of clamp investigation improving its quality.

[Interaction of cholesterol with polypeptides and amino acids]. / Vzaimodeistvie kholesterina s polipeptidami i aminokislotami.

Using absorbance spectra at 185-225 nm, the interaction of cholesterol and its methyl and acetic esters with some amino acids, guanidine, metformine and two polypeptides-polyarginine and polylysine was studied. In aqueous and alcoholic media (pH 6-7) the largest shift of the absorption maximum in the presence of non-esterified cholesterol was observed in the compounds containing guanidinio groups (guanidine, metformine, arginine, polyarginine) and, in a lesser degree, the compounds containing epsilon-amino groups (lysine, polylysine). The cholesterol esters produced a marked shift in the absorption maxima of arginine, lysine, polyarginine and polylysine in a spirituous medium (as compared to an aqueous medium). During alpha-helization of polyarginine and polylysine (pH 10.5) the non-esterified cholesterol and also its methyl ester induced the highest shift in the absorption maximum of these polypeptides. The cholesterol interaction with the compounds containing the quanidinio and epsilon-amino groups can also be evidenced from the clarification of aqueous suspensions of cholesterol, its methyl ester and cholestane under effects of polylysine and especially polyarginine. The possibility of phospholipid-independent binding of cholesterol by proteins and the type of lipid protein interactions is discussed.

[Interaction of cholesterol with apoprotein E - an arginine-rich protein of very low density lipoproteins]. / Vzamideistvie kholesterina a apoproteinom E - argininbogatym belkom lipoproteidov ochen' nizkoi plotnosti.

Apoprotein E was isolated from delipidated lipoproteins of very low density obtained from blood plasma of rabbits with experimental hypercholesterinemia. The protein, whose molecular weight is 45000, produces a single hand during polyacrylamide gel electrophoresis and contains 10% of arginine. The formation of an apoprotein E -- cholesterol complex and participation of guanidine groups of guanidine groups of arginine residues of apoprotein E in cholesterol binding have been postulated.

[Role of guanidine groups of glutamate dehydrogenase arginine residues in the binding of sex hormones]. / Rol' guanidinovykh grupp argininovykh ostatkov glutamatdegidrogenazy v sviazyvanii polovykh gormonov.

Interaction of sex hormones and glutamate dehydrogenase is studied in vitro. Data are presented concerning the participation of guanidine groups of the enzyme arginine residues in the binding of sex hormones and in the realization of their inhibitory effect.

[On glutamate dehydrogenase interaction with sex hormones]. / O vzaimodeistvii glutamatdegidrogenazy s polovymi gormonami

The effect of sex hormones on the activity of glutamate dehydrogenase from beef liver was studied in vitro. The inhibitory effect of the hormones was relieved both when the guanidine groups of the enzyme were blocked and when L-arginine was added to the reaction mixture. The data obtained suggest that the guanidine groups of the arginine residues of the enzyme are involved in the realization of the inhibitory effect of the hormones.

[Effect of insulin and steroid hormones on the conformation and activity of enzyme proteins]. / Vliianie insulina i steroidnykh gormonov na konformatsiiu i aktivnost' fermentnykh belkov

An immediate effect of hormones (insulin, oxytocin, glucocorticoids and sex hormones) on the conformation and activity of enzymatically active proteins (hexokinase, glutamate dehydrogenase) was studied. Hormone-enzyme complex of insulin-hexokinase was shown to be formed. This process was accompanied by dissociation of the enzyme into two dimers without a loss of the catalytic activity but with disappearance of the property to be inhibited by glucocorticoids. The effect of insulin on the hexokinase activity was postulated to occur due to reaction of thiol-disulphide exchange between disulphide group of insulin and free sulfhydryl group of hexokinase. The inhibitory effect of sex hormones on the glutamate dehydrogenase activity was shown to be determined by their association with the enzymatically active protein. This phenomenon did not occur under conditions of stabilization of the quaternary structure of the enzyme. If the guanidine groups of glutamate dehydrogenase were blocked the inhibitory effect of sex hormones was found to decrease. These data demonstrate the importance of the guanidine groups in binding of sex hormones.

[Effect of thiol reagents on the interaction of glutamate dehydrogenase with sex hormones]. / Vliianie tiolovykh reagentov n vzaimodeistvie glutamatdegidrogenazy s polovymi gormonami

The blocking of glutamate dehydrogenase SH-groups with some thiol reagents decreases the binding of sex hormones and the degree of their inhibitory effect on glutamate dehydrogenase activity.

[Interaction of steroid hormones with glutamate dehydrogenase]. / Vzaimodeistvie steroidnykh gormonov s glutamatdegidrogenazoi

The inhibitory action of sex hormones on the glutamate dehydrogenase activity is due to their binding to the enzyme protein. No binding of sex hormones to glutamate dehydrogenase is observed in the presence of L-amino acids, preventing the enzyme dissociation. Under those conditions the enzyme sensitivity to the inhibitory action of the hormones sharply decreases.