Characteristics of the het mutations in the Escherichia coli chromosome causing an increase in Tn1 transposition frequency

Four mutations were studied which lead to increasing the frequency of transposon Tn1 translocation into different replicons. These mutations (het1, het2, het3 and het4) increase the frequency of Tn1 translocation 10-20-fold. The het1 mutation is recessive and has been localized in the 90-94.5 min region of the bacterial chromosome. The mutation effects Tn1 transposition in the presence of F plasmid only. As we have demonstrated recently, F-plasmid inhibits Tn1 transposition in Escherichia coli cells. The het1 mutation eliminates this inhibition. Unlike het2, het3 and het4 mutations, het1 is responsible for resistance to male phages f1, f2, MS2 and inhibition of conjugative transfer in F+ bacteria.     

Isolation of estrophilic fractions of hydroxysteroid dehydrogenase from rabbit liver

Estrophilic forms of rabbit liver cytosolic hydroxysteroid-dehydrogenase (HSD) were obtained as a highly purified preparations by means of fractionation with ammonium sulfate, gel-filtration, ion-exchange chromatography on DEAE-Sephadex A-50, affinity chromatography on estradiol-Sepharose and ion-exchange chromatography on DEAE-Toyopearl 650M. The protein express 4 different kinds of NADP-dependent activities: 3 alpha, 3 beta- and 17 beta-HSD activities with androgens and 20 alpha-HSD with progesterone as substrates. Revealed multiplicity of HSD enzymatic activity is demonstrated here for the first time. 17 beta-HSD activity of the protein preparations with estradiol is extremely low. Absence of a real metabolic activity of the protein with a ligand interacting with it rather intensively suggests that the isolated HSD forms can act not only as an enzyme, but also as a buffer-reserving mechanism for some steroids.     

Immunobiologic activity of Bordetella pertussis strains defective in various virulence factors

The immunobiological properties of mutant strains, selectively deprived of certain antigens (hemagglutinin, B. pertussis toxin, dermonecrotic toxin, hemolysin, adenylate cyclase), have been studied with the aim of finding out the relationship between the presence of certain antigens in microbial strains and their protective properties. The results of these studies suggest that the protective potency of pertussis vaccine may be related to the presence of some antigenic substances, including those not pertaining to the known factors of virulence.     

Partial characterization of protein kinase-catalyzed phosphorylation of low molecular weight proteins in purified preparations of pigeon heart sarcolemma and sarcoplasmic reticulum

Pigeon heart microsomes contain three minor size protein kinase substrates of minimal molecular weights of 22 000, 15 000, and 11 500, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When the microsomes were partially loaded with calcium oxalate and subjected to rate zonal and isopynic centrifugations in sucrose density gradient columns, the 22 000 and the 15 000 dalton proteins settled in the heaviest fraction, which was composed mainly of vesicles of sarcoplasmic reticular membranes; the 11 500 dalton protein was concentrated in the lightest fractions, which consisted chiefly of vesicles of sarcolemmal origin. During incubation of the membrane fractions with Mg[γ-³²P]ATP significant amounts of ³²P were incorporated into all these proteins. Incorporation of ³²P into the 15 000 dalton protein was moderately and ³²P incorporation into the 22 000 dalton protein was markedly enhanced in the presence of exogenous soluble cyclic AMP-dependent protein kinase and cyclic AMP. The phosphorylation of the three proteins was virtually unaffected by CA²⁺ concentrations up to 0.1 mM and by ethyleneglycol-bis(β-aminoethylether)-N,N′-tetraacetic acid in the absence of added Ca²⁺.Phosphorylation of the 22 000 and the 11 500 dalton proteins occurred mainly at serine residues. In the 15 000 dalton protein threonine residues were the main site of endogenous phosphorylation. Nearly equal amounts of [³²P]-phosphate were incorporated into threonine and serine residues of this protein when phosphorylation was supported by exogenous cyclic AMP-dependent protein kinase and cyclic AMP.The 15 000 dalton protein could be removed from its membrane attachment by extraction with an acidic chloroform/methanol mixture. This step opens the way for the purification of this membrane-bound protein kinase substrate.     

Study of the relationship between the trace element content and the physiological properties of Salmonella typhi during submerged cultivation

The content of trace elements in the cells served as one of the characteristics of physiological condition of the population. The character of the changes in the trace elements content depending on the rate of the microbial multiplication pointed to the importance of the mineral sources of nutrition for the development of the cells analyzed.     

The effect of α-factor on the rate of cell-cycle initiation in Saccharomyces cerevisiae : α-Factor modulates transition probability in yeast

The rate of cell-cycle initiation was studied in a-cells of S. cerevisiae in the presence of the synthetic analogue of α-factor [N-Trp, Arg⁷]-α-factor (TA-αF). It was shown that TA-αF lowers the rate constant of cell-cycle initiation (or transition probability) for each separate cell. It was concluded on the basis of these results that the term ‘arrest’ in G1 by α-factor should be interpreted in a quantitative sense as the decrease in the probability of the emergence from ‘start’ per unit time and not as being equivalent to an ‘all-or-none’ response. The dependence of the rate constant of the cell-cycle initiation on the concentration of TA-αF can be described by the Hill equation where n = 1.01 + 0.05 and K = 14.5 ± 2.5 nM (±S.E.). It is demonstrated that after transfer of cells into the medium with a higher or a lower concentration of TA-αF, the rate constant of cell-cycle initiation changes abruptly from one value to another after a lag-period of 30 and 40 min respectively. This suggests a multistep mechanism of action for α-factor. The difference in the lag-periods allows us to suggest that α-factor exerts its action by two independent pathways. Since the Hill coefficient is practically equal to unit, no cooperative interactions are likely to be involved at least in one of these pathways. The inhibition of cell-cycle initiation can be used as a more adequate and sensitive test for biological activity of α-factor as compared to morphological measurements.     

Effect of 3-hydroxypyridine derivatives on the central nervous system

Experiments on mice and rats were made to study the effect of inhibitors-antioxidants (3-hydroxypyridine derivatives) on the central nervous system. It was established that 3-hydroxypyridine derivatives (50 to 200 mg/kg) possess a broad spectrum of psychotropic effects. They cause normalization of behavior in conflict situations, exert an antiaggressive and anticonvulsant action (antagonism with corazol), are capable of potentiating the hypnotic effect of barbiturates, and of suppressing the animals' motor activity if given in high doses. Most compounds under study have antihypoxic and antiamnestic effects.     

High-frequency electrospectroscopy of human whole blood with different degrees of oxygen saturation

The electric properties of normal human blood were measured at 1.0-2.0 MHz frequency range. The dependence of relaxation time of the erythrocyte membranes on the degree of hemoglobin molecules saturation with oxygen was obtained.