Morphology and coexistence of congeneric ectoparasite species: reinforcement of reproductive isolation?

Assuming that differences or similarities in morphology among congeneric parasite species living in the same habitat are not a random pattern, several hypotheses explaining morphological differences were tested: (i) reproductive isolation, (ii) niche restriction resulting from competition, and (iii) niche specialization. Congeneric monogenean (platyhelminth) ectoparasites parasitizing the gills of one host species were used as an ecological model. Morphometric distances of the attachment organ and morphometric distances of the copulatory organ between species pairs were calculated, Levin's niche size and Renkonen niche overlap indices were applied. Our results support the prediction that the function of niche segregation is to achieve reproductive isolation of related species in order to prevent hybridization (reinforcement of reproductive barriers). Parasite species living in the same niche differ greatly in the size of copulatory organ. Moreover, species coexistence is facilitated by an increase in morphometric distances of copulatory organ and niche centre distances. Our results also show that species living in overlapping niches have similar attachment organs, which supports the prediction that morphologically similar species have the same ecological requirements within one host and suggests small effects of interspecific competition for the evolution of morphological diversity of attachment organs. Specialist adaptations also seem to facilitate species coexistence and affect the niche distribution within host species. Parasite species that can colonize more than one host species, i.e. generalists, occupy more distant niches within host species than strictly host-specific parasites. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76, 125–135.     

Menaquinone function in the respiratory chain of Micrococcus lysodeikticus]

Menaquinone-9 which is destructed under long-wave UV-irradiation is isolated from Micrococcus lysodeikticus membranes. NAD-H, malate and lactate oxidases are observed to be inhibited under irradiation, dehydrogenases of these substrates being almost intact. Photoinactivation of menaquinone results in the reduction of only one from two cytochromes b, presented in the membrane, thus testifying the location of menaquinone-9 between cytochromes b in the respiratory chain. Reconstruction of malate, NAD-H and lactate oxidases after irradiation took place when natural menaquinone (MQ-9) or menadione (MQ-0) were added. Detailed scheme of M. lysodeikticus respiratory chain is given.     

Interactions between dopamine, serotonin, and other reward factor

Interactions between dopamine, serotonin, reward factors, and main representatives of regulatory peptide families have been analyzed using the bulk of disembodied publications of the last 50 years. A database covering the direction of physiological effects, doses, and administration modes of regulatory peptides and biologically active compounds, species, organ and tissue systems, as well as receptor mechanisms has been created. Complex cascade interactions between dopamine, serotonin, reward factors, and regulatory peptides were analyzed and organized. Analysis of coordinated functioning of the dopaminergic and serotonergic systems (at different levels) allowed us to reveal their opponent reciprocal interactions and to introduce their integral characteristics.     

Changes in peroxidation under conditions of 3,4-benzypyrene-induced carcinogenesis

The activities of enzymatic systems generating and destroying peroxides and the lipid peroxide content in neoplastic rat liver and 3,4-benzpyrene-induced sarcoma were studied. The tumour was characterized by high activity of glutathione peroxidase and low activity of catalase. No urate- and glycolate oxidases or ascorbat dependent peroxidation of lipids and lipid peroxides were found in the tumour. In the liver of neoplastic animals the activities of glutathione peroxidase and NADPH-dependent system of microsomal phospholipid peroxidation and the lipd peroxides content were increased, whereas the activities of catalase and urate oxidase were decreased.     

Intracellular proteolysis: Signals of selective protein degradation

Selective proteolysis is one of the mechanisms for the maintenance of cell homeostasis via rapid degradation of defective polypeptides and certain short-lived regulatory proteins. In prokaryotic cells, high-molecular-mass oligomeric ATP-dependent proteases are responsible for selective protein degradation. In eukaryotes, most polypeptides are attacked by the multicatalytic 26S proteasome, and the degradation of the majority of substrates involves their preliminary modification with the protein ubiquitin. The proteins undergoing the selective proteolysis often contain specific degradation signals necessary for their recognition by the corresponding proteases. This article is dedicated to the 25th Anniversary of the journal Bioorganicheskaya Khimiya     

Distribution of amiloride-sensitive sodium channels in the oral cavity of the hamster

The distribution of amiloride-sensitive sodium channels (ASSCs) in taste buds isolated from the oral cavity of hamsters was assessed by patch clamp recording. In contrast to the case for rats, taste cells from the fungiform, foliate and vallate papillae and from the soft palate all contain functional ASSCs. The differential distribution of ASSCs between the hamster and the rat may be important for understanding the physiology underlying the differing behavioral responses of these species to sodium salts.