The lack of ability of carcinogens and non-carcinogenic analogs to induce sex-linked recessive lethals in Drosophila melanogaster

The mutagenic activity of two known carcinogens (benzo(a) pyrene and 2-acetylaminofluorene) and that of two structurally closely related but not carcinogenic compounds (pyrene and 4-acetylaminofluorene) was examined by the Muller-5 test for sex-linked recessive lethals (SRL). The chemicals tested were applied to the food medium for larvae of Canton-S Drosophila melanogaster. No statistically significant differences in frequencies of induced SRL were found either within pairs of chemicals or between treated and untreated animals.     

Mitogenic action of substance P on the epithelial cells of the tongue

Substance P (10 and 100 ng/ml) stimulates the proliferation of basal cells from rat's tongue epithelium in primary cultures with 2.5% fetal calf serum. In serum-free medium substance P have no effect on the epithelial cell growth. This neuropeptide secreted by afferent nerve fibers of the tongue epithelium is suggested to have a neurotrophic influence on epithelial cells controlling their proliferation.     

Determination of plasmid copy number by the "boiling" method

A fast and reliable approach for determination of plasmid copy number in Escherichia coli is proposed, based on the "boiling" method (5) for separation of plasmid and chromosomal DNA. The method includes in vivo uniform labeling of total bacterial DNA, separation of DNA into plasmid and chromosomal DNA fractions, and quantitation of DNA in the two fractions by radioactivity measurement. No isolation and purification of native DNA are necessary.     

Spectral features of amines of 2-phenylbenzazoles upon interaction with DNA

Absorption and fluorescent spectra of various synthetic aminophenyl derivatives of benzoxazole, benzothiazole and benzimidazole have been studied to estimate the efficiency of their binding with DNA. The significance of different functional groups of the fluorochromes for their interaction with DNA was determined, and main demands are formulated to the compounds to be used as potential fluorescent probes for DNA studies.     

Amplification of bacterial plasmids without blocking protein biosynthesis

The effect of amino acids (presence or absence from the growth media) and metal ions on the replication of Escherichia coli plasmids in rel A+ strains was studied. It was found that: (i) The absence of one amino acid from the growth media had no effect on the plasmid copy number in prototrophic E. coli strains: (ii) The presence of only one amino acid in artificial media free of amino acids had a negligible effect on the plasmid copy number for the amino acids Ala, Arg, Glu, His, Leu, Phe, Thr, Trp, and Tyr: (iii) The combination of Met and Thr caused a rise in pBR322 plasmid copy number up to 90-100 plasmid copies per cell: (iv) The Fe3+ concentration had an amplification effect on E. coli plasmids. The pBR322 plasmid copy number for media free of amino acids and supplemented with 0.2-0.4 mM FeCl3 was 60-80 plasmid copies per cell: (v) The combination of Fe3+ with certain amino acids (Ala, Arg, Glu, Leu, Thr, and Trp) leads to a dramatic increase in the plasmid copy number reaching 180-270 plasmid copies per cell for the plasmid pBR322 and 20-24 for the plasmid pR100.     

On the trends in protein molecular evolution: Amino acid composition

Data on the amino acid composition of proteins having various functions from organisms representing different evolutionary levels (83 superfamilies) are used in order to elucidate the trends in protein molecular evolution. The interconnections evolutionary rate (rate of mutation acceptance) — amino acid composition, and evolutionary level of the organism — amino acid composition (in case of proteins of the same or very similar function) are studied. The amino acid compositions of proteins performing jointly an evolutionarily old functions are also juxtaposed. The mean contemporary protein composition is used as a basis for comparison. The obtained results are evidence in favour of the existence of a trend for an increase of the special amino acids (Met, Ile, Gln, His, Lys, Asn, Phe, Tyr, Trp, Cys) at the expense of the usual ones (Thr, Pro, Ala, Ser, Arg, Gly, Leu, Val, Glu, Asp). The tests of statistical significance of the obtained results (comparison of the mean compositions of proteins from low evolutionary level organisms with that of all sequenced proteins; comparison of the mean contemporary protein composition with that obtained after simulation of the evolutionary process) confirm and universalize the observed trend. The above results direct the attention to the concept of a smaller number of amino acids in the ancient proteins and respectively simpler genetic code. A fluctuation around the initial primitive level is suggested to explain the conservatism of proteins of the same function in evolutionarily low level organisms. The observed trend could be applied for designing new proteins.     

Local anesthetics-induced inhibition of chloroplast electron transport

The effects of local anesthetics on photosynthetic activity of pea chloroplasts were investigated in order to elucidate the role of Ca2+ in photosynthetic electron transport. Dibucaine, benzocaine and tetracaine were found to inhibit the O2-evolving activity. The inhibitory effect decreases in the order dibucaine greater than benzocaine greater than tetracaine greater than trimecaine similarly as does the potency to inhibit propagation of excitation in nerve fibre. As demonstrated in experiments with artificial donors and acceptors, the site of inhibition is the water-splitting site of PSII. The inhibitory power of the anesthetics grows with increasing ionic strength of the incubating mixture (by adding NaCl or MgCl2) and with pH; this is explained by occurrence of the neutral form of amine. At low concentrations the charged anesthetic acts as a protonofore; however, the inactivation of water splitting is not due to the protonophoric effect. The incubation is followed by the disappearance of ESR signal IIs. The role of Ca2+ and Ca2+-binding protein in PSII electron transport and its localization are discussed.     

Features of energy metabolism of myocardial mitochondria and their ultrastructure in normal and immobilized rats of different animal social rank

The oxidative and phosphorylating functions of mitochondria (M) and their ultrastructure were studied in the myocardium of normal and 6.5-hour immobilized rats that belonged to different zoosocial groups. M from dominant rats under normal conditions were shown to exhibit higher energy and to possess better respiratory energy regulation than those of "outcast" rats. However, the ultrastructure of M had no group specificity in normal. The immobilization caused more profound changes in M from the dominant rats and led to a more pronounced swelling of M in the myocardium of the above rats than in the "outcast". M from the subdominant rats were most resistant to an immobilization stress.     

Molecular weights of the hetero-organic NHCP antigens of kidney origin associated with rat hepatomas

The narrow NHCP protein fractions, possessing a proper phosphoprotein kinase activity, were isolated from kidney of intact rats, hepatoma tissue and liver cells of rats treated with hepatocarcinogen in the process of phosphocellulose gradient chromatography by elution of 0.4-0.5 M NaCl. The gel filtration on Sephadex G-75 and SDS-PAAG electrophoretic data demonstrate that all the NHCP protein fractions mentioned above include a general molecular component with the mass of 23 kD, and display identical antigenic properties. Thus, in accordance with the data obtained, the role of the hetero-organic NHCP protein antigen of kidney origin associated with hepatoma may be played by the general molecular component of NHCP protein fractions possessing properties of a specific chromosomal phosphoprotein kinase.