Structural characteristics of lysine-rich histone from the sperm of a mollusk Anodonta piscinalis

Sperm of freshwater bivalve mollusk Anodonta piscinalis was found to contain two fractions of lysine-rich histone: somatic histone H1 and sperm-specific protamine-like histone, named Hp. A detailed analysis of H1 and Hp structure was carried out by means of N-bromosuccinimide, chymotrypsin and pepsin cleavage followed by determination of the lysine residue number, positive charge and molecular length of obtained fragments by the method of incomplete succinylation. It has been shown, that Anodonta histone H1, like the avian histone H5, contains 3 tyrosine residues in the central hydrophobic domain of the molecule. Histone Hp contains 5 tyrosine residues, 3 of which are localized in the hydrophobic domain, while the rest two--in the COOH-terminal part of the molecule, characterized by a strong positive charge. Such unusual disposition of tyrosine residues in the lysine-rich histone has been found for the first time. All the regions of histone Hp molecule contain a great number of arginine residues. The only phenylalanine residue is localised approximately in the middle of the polypeptide chain for both H1 and Hp molecules. On the basis of structure homology between histones H1 and Hp the origin of Hp from H1 in the course of evolution is proposed.     

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Synthesis and antibacterial activity of novel phosphonium salts on the basis of pyridoxine

A series of 13 phosphonium salts on the basis of pyridoxine derivatives were synthesized and their antibacterial activity against clinically relevant strains was tested in vitro. All compounds were almost inactive against gram-negative bacteria and exhibited structure-dependent activity against gram-positive bacteria. A crucial role of ketal protection group in phosphonium salts for their antibacterial properties was demonstrated. Among synthesized compounds 5,6-bis[triphenylphosphonio(methyl)]-2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine dichloride (compound 20) was found to be the most effective towards Staphylococcus aureus and Staphylococcus epidermidis strains (MIC 5 μg/ml). The mechanism of antibacterial activity of this compound probably involves cell penetration and interaction with genomic and plasmid DNA.     

A Model of Genome Size Dynamics During Speciation

A model developed for the evolving size of the repetitive part of the eukaryote genome during speciation was subjected to analytical and computer treatment. The basic assumption of the model was that two classes of repetitive DNA contribute mainly to macroevolutionary changes in genome size: arrays of tandem repeats (ATR) changing through unequal crossover and mobile genetic elements (MGE) changing presumably through an integration mechanism of the Tn- and Is-kind operating in bacteria. Within the framework of this model, the macroevolution of the MGE size is formally equivalent to that of the ATR in the particular case when shifts of chromatids have only one repeat out of register. This allowed us to consider genome size as a large set of various ATRs. The results obtained are as follows. If the duplication and deletion of repeats have unequal fixation probabilities during each speciation act, the predicted species distributions of genome size significantly deviate from the real ones; if they have equal fixation probabilities, there is a conformance between calculated and real distributions. In the latter case, the model reproduces the salient features of real distributions upon acceptance of 1) upper selective boundary nonspecifically limiting increase in genome size within the evolving taxonomic group and 2) non-neutrality of variability in genome size with respect to speciation.