Physico-chemical properties of several phages of Bacillus thuringiensis

A study was made of biological and physico-chemical properties of phages of Bac. thuringiensis as well as of a number of parameters of nucleic acids isolated from these phages. The phages contain double-stranded DNA. Molecular weights of DNA from three phages--Tg9, Tg10 and Tg13 have been determined by two independent methods: by measuring the contour length of DNA, from the sedimentation constant and for DNA of phage Tg10 also by endonuclease EcRI hydrolysis. These methods gave similar results. On the basis of the temperature of DNA melting the content of GC pairs was found equal to 37.9, 33.4 and 35.1 mole% for DNA's of phage Tg9, Tg10 and Tg13, respectively. On the basis of measuring the intervals of DNA melting a conclusion was made that DNA of the Tg9 and Tg13 phage has a random distribution of base pairs, while DNA of phage Tg10 displays some clustering of base distribution along the molecule. It has been shown that restrictase EcoRI hydrolyses phage Tg10 DNA into 6 fragments of different molecular weights; DNA's of Tg9 and Tg13 phages are not hydrolyzed. A possibility of existance of phage Tg10 DNA in linear and ring forms has been established. The characteristics of phage particles have been determined by electron microscopy.     

The unusual estrogen-binding protein (UEBP) of male rat liver: structural determinants of ligands

The unusual estrogen-binding protein (UEBP) found in a male rat liver is a sex dependent protein which differs from other known receptor and transport proteins by the high lability of its complexes with estradiol (E2) and also the unique specificity of affinity for hormones. In this work values of relative binding affinity (RBA) of the UEBP for 57 steroids and their analogs were determined. The affinity of steroids was characterised by the amount of the unlabeled compound needed for 50% inhibition of [3H]-E2 binding with the UEBP. A number of derivatives of estrane and androstane possess an ability to interact with this protein, in contrast to the derivatives of pregnane, stilbene and triphenylethane. Characterized by RBA values, natural steroids are found to have the following order: estriol larger than or equal to E2 greater than 16 alpha-hydroxyestrone = 2 alpha-hydroxytestosterone greater than 16-epiestriol greater than or equal to estetrol greater than or equal to 17-epiestriol greater than or equal to 2-methoxyestradiol greater than or equal to 5 alpha-androstane-3 alpha,17 beta-diol greater than or equal to estrone greater than testosterone greater than or equal to 2 beta-hydroxytestosterone greater than 5 alpha-dihydrotestosterone. Affinity of estrogens and androgens for the UEBP diminishes abruptly after removal of 3- and 17-hydroxy groups, masking of these by ether bonds or changing of 17 beta-hydroxyl to 17 alpha. All the investigated 17 oxo-C19-steroids, 5 beta-derivatives of testosterone, its 6 beta- and 16 alpha-hydroxy metabolites as well as 5 alpha-androstane-3 beta,17 beta-diol and 19-nortestosterone exhibit no essential affinity for the protein. On the basis of the results obtained it is suggested that the binding sites for estrogens and androgens in the UEBP molecule overlap but do not completely coincide.     

Chronoinotropic reaction of the hypertrophied myocardium using an electromechanical coupling mathematical model.]

Static and dynamic chrono-inotropic responses were recorded from both normal and hypertrophic rat auricular myocardium. The slope of the static force-frequency relation from hypertrophied heart was steeper than in the control hearts. The cellular mechanisms underlying changes in the force frequency response associated with hypertrophy of the heart were studied by means of a mathematical model of excitation-contraction coupling. The characteristic features of hypertrophied heart force-frequency relations are shown to be due to the enhanced volume of the intracellular Ca-stores in contrast to the total volume of the cardiomyocyte.     

Synaptonemal complexes as evidence for meiosis in the life cycle of the monomorphic diplokaryotic microsporidium Paranosema grylli

Characteristic configurations of the nuclei and synaptonemal complexes, indicative of the onset of meiosis, were observed in the meronts of the monomorphic diplokaryotic microsporidium, Paranosema grylli. This finding indicates that a process similar to the meiosis previously reported in polymorphic and some monomorphic monokaryotic microsporidia probably occurs in the development of P. grylli. It is the first evidence for the possible presence of a sexual phase in the life cycle of this microsporidium, which for a long time has been considered asexual.     

Independence of the processes of transposition and genome rearrangements induced by transposons

The data on the influence of the tnm mutations affecting transposition process on the deletion formation promoted by Tn and IS elements are presented. It was shown that the tnm mutations did not affect the frequency of deletion formation. The results of genetic analysis of the tnm mutant deficient in both transposition and genomic rearrangements induced by Tn9 inserted into lambda prophage, indicated that the mutant phenotype was caused by two different but linked mutations. A mutation affecting the process of genomic rearrangements was designated gerA2. The gerA2 mutation decreased sharply the frequency of rearrangements promoted by Tn9, Tn10 or Tn601 inserted into lambda prophage. However, this mutation had no influence upon transposition of the same Tn elements. The data obtained could be interpreted as indicating the independence of the processes of transposition and genomic rearrangements or as indication of the existence of specific steps of these processes.     

Morphological characteristics of phagolysis of S- and R-forms of Shigella flexneri

The differences in the character and time of the lysis of S. flexneri S- and R-mutant cells have been detected by the method of time-lapse microfilming. The asymmetry of the phagolysis of the S-form of shigellae infected with phage F1 has been revealed.