Use of spin-labelled substrate analogs for a comparative study of microsomal cytochrome P-450 and P-448

The previously described, iodine-labeled alkylating stable nitroxyl radicals located at different distances between the N-O. group and the iodine atom were used for a comparative study of the structure of microsomal cytochromes P-450 and P-448 active centers. The radicals were shown to change the optical spectra of Fe3+ located in the active site of the enzyme that are similar to those induced by cytochrome P-450 substrates. Some differences in the type of the radicals binding to control, phenobarbital- and 3-methylcholanthrene-induced microsomes were revealed. The alkylating radical substrate analogs covalently bound to microsomal cytochrome P-450 in the vicinity of the active center, resulting in the inhibition of oxidation of type I and II substrates (e. g., aniline and naphthalene). The value of the spectral binding constant (Ks) for naphthalene in the presence of the radical covalently bound to the cytochrome P-450 active center showed a tendency to increase. Using the ESR technique, the interaction between Fe3+ and the radical localized in the active site of cytochrome P-450 was demonstrated. The contribution of Fe3+ to the relaxation of the radicals covalently bound to cytochrome P-450 was evaluated from the values of the spin label ESR spectra saturation curves at 77K. The distances between the N-O. group of these radicals and Fe3+ in the enzyme active center for the three types of microsomes were determined. The data obtained point to structural peculiarities of the active center of cytochrome P-450, depending on the microsomal type.     

Effect of adenine nucleotides on the activator function of streptokinase

The addition of ATP or 3,5-AMP (but not UTP, GTP, CTP, AMP, 2,3-AMP, ADP, inorganic pyrophosphate) at a final concentration of 10(-1) M into streptokinase solution, pH 7.0 or 9.5, causes a dramatic inhibition of streptokinase-induced fibrinolysis. The specificity of ATP effect is fully lost at pH 3.0, when all nucleotides completely inhibit the activating function of streptokinase. Ribose-5-phosphate causes a similar effect at pH 3.0. The character of nucleotide action on the activating function of streptokinase considerably differs from their influence on proteolytic reactions.     

Mitogenic action of bacterial T-independent antigens under various conditions of lymphocyte culture

The mitogenic response of lymphocytes in mouse spleen cell culture to the action of Salmonella typhi lipopolysaccharide (LPS) and Vi-antigen under different experimental conditions has been studied. The density of the culture has been shown to influence the activation of lymphocytes with Vi-antigen. Thus, macrophages stimulate mitogenesis at the concentration of lymphocytes equal to 1.0-1.2 X 10(6) cells/ml and suppress it when this concentration increases tenfold. The method used for the purification of cell suspension from adhering cells has been shown to influence the level of the mitogenic response of lymphocytes. The cultures, purified from macrophages by filtration through a column packed with cotton wool, have been found to respond to the mitogenic doses of LPS 7-8 times weaker than those purified by adhesion onto plastic. Background and mitogen-induced inclusion of 3H-thymidine into lymphocytic DNA varies in accordance with the presence of adhering cells. For this reason, in the evaluation of the influence of macrophages on mitogenesis it is expedient to consider not only the stimulation index, but also the absolute inclusion of thymidine into cells.     

Genetics of congenital esophageal defects

An analysis of 304 cases of esophageal atresia in fetuses and neonates showed that frequency of other congenital malformations is 43.1% including 10% of chromosomal disorders and monogenous syndromes. Summarizing the authors' own data and evidences from literature the genetic risk for sibs is calculated to be 0.88% and heredity--57.3 +/- 5.1%. The hypothesis that esophageal atresia is a malformation of multifactorial genesis with polygenic hereditary component is confirmed.     

Purification, quaternary structure and immunological properties of phosphorylase kinase from chicken skeletal muscle

Phosphorylase kinase was isolated from red and white chicken skeletal muscle in a nearly homogeneous state as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The molecular weight of the native enzyme as determined by gel filtration on Sepharose 4B is close to that of rabbit skeletal muscle phosphorylase kinase (i. e., approximately 1300 000). The molecular weights of the subunits determined by SDS gel electrophoresis are: alpha', 140 000 beta, 129 000; gamma', 44 000; delta, 17 000 (cf. the Mr values of the alpha- and gamma-subunits of the rabbit muscle isoenzyme are 146 000 and 42 000). The four subunits, alpha', beta, gamma' and delta, were found to exist in equimolar amounts as shown by a densitometric analysis of acrylamide gels; hence, the subunit formula of the chicken skeletal muscle isoenzyme is (alpha' beta gamma' delta)4. Rabbit antisera against a mixture of alpha'- and beta-subunits of chicken phosphorylase kinase yield a single precipitin line with this enzyme, do not show cross reactions of identity with the rabbit muscle enzyme but strongly inhibit the activity of the chicken enzyme and partially inhibit the activity of the rabbit muscle isoenzyme.     

Ascorbate-independent carotenoid de-epoxidation in intact spinach chloroplasts

Slow (> 1 s) light-induced absorbance changes in the 475–530 nm spectral region were examined in Type A chloroplasts from spinach. The most prominent absorption change occurred at 505 nm. The difference spectrum for this light-induced increase, its absence in osmotically shocked chloroplasts and restoration by ascorbate, and its sensitivity to dithiothreitol indicate that the absorption change is due to carotenoid de-epoxidation. The reaction in intact chloroplasts is characterized by its independence of exogenous ascorbate and a rate constant 3- to 8-fold higher than that reported previously for chloroplasts supplemented with ascorbate.The relevance of carotenoid de-epoxidation to other photosynthetic processes was examined by comparing their sensitivities to dithiothreitol. Levels of dithiothreitol that eliminate the 505 nm shift are without effect on saturated rates of CO₂ fixation and do not appreciably inhibit fluorescence quenching. We conclude that carotenoid de-epoxidation is not directly involved in the reactions of photosynthesis or in the regulation of excitation allocation between the photosystems.     

Sex-specific somatic–otolith growth relationship in two Gadidae

Otolith and somatic mass of two Gadidae ( Merlangius merlangus and Trisopterus minutus ) were compared in order to analyse the sex-specific relationship between otolith and somatic growth at age. In the present study, otolith mass appeared a reliable indicator of age in both species. Otolith growth reflected somatic growth, but the relationship between these characters varied and differed between species and sexes.     

Experimental effect of ultraviolet laser radiation on lung, tracheal and bronchial tissues

The authors studied morphological changes under the effect of laser radiation. Various disorders in the blood circulation have been revealed such as hyperemia, stasis which did not depend upon the exposition time.