Synthesis and immunochemical study of the antigenic determinant of the H-2Db molecule of the murine major histocompatibility complex

Primary structure of murine class I histocompatibility antigens has been analysed to select possible antigenic determinant. Hexapeptide Leu-Gln-Gln-Leu-Ser-Gly, homologous to the region 95-100 of the H-2Db antigen heavy chain, was synthesised by stepwise elongation of peptide chain beginning from the COOH-terminal Gly. Rabbit anti-hexapeptide antibodies were obtained and shown to interact specifically with purified H-2Db antigen as well as with the native antigen on cell surface. These antibodies bind to lymphocytes of H-2b haplotype (C57BL/6 mice) but not H-2d (BALB/c) or H-2k (CBA). These data suggest that the region 95-100 is responsible for serologic differences between the alleles of H-2 antigens, i.e. it may be a xenotypic as well as an allotypic antigenic determinant. The latter was confirmed by study of interaction of the hexapeptide with allogeneic monoclonal antibodies specific to H-2Db antigen.     

Artificial peptide and carbohydrate antigens. Immobilization of haptens and adjuvant (MDP) on polyacrylamide

To study the influence of the polyacrylamide carrier on immunogenic properties of the peptide and oligosaccharide haptens, we have prepared artificial antigens by conjugation of a synthetic hexapeptide (homologous to the fragment 95-100 of the murine H-2Db antigen heavy chain) or of an oligosaccharide (antigenic determinant of human blood groops, Lea) with polyacrylamide. In some cases the conjugates containing also a synthetic glycopeptide adjuvant, N-acetylmuramoyl-L-alanyl-D-isoglutamine (MDP), were used. Antisera against haptens were obtained by immunization of BALB/c mice with corresponding conjugates. By the enzyme-linked immunosorbent assay it was shown that these antisera had a high binding titer (up to 10 000) to corresponding hapten, and MDP immobilized on the same carrier as hapten possessed a considerable immunostimulating activity. Thus, usefulness of polyacrylamide for preparation of immunogenic artificial molecules carrying peptide and oligosaccharide haptens was demonstrated.     

Mitochondrial DNA evolution in the genus Equus

Employing mitochondrial DNA (mtDNA) restriction-endonuclease maps as the basis of comparison, we have investigated the evolutionary affinities of the seven species generally recognized as the genus Equus. Individual species' cleavage maps contained an average of 60 cleavage sites for 16 enzymes, of which 29 were invariant for all species. Based on an average divergence rate of 2%/Myr, the variation between species supports a divergence of extant lineages from a common ancestor approximately 3.9 Myr before the present. Comparisons of cleavage maps between Equus przewalskii (Mongolian wild horse) and E. caballus (domestic horse) yielded estimates of nucleotide sequence divergence ranging from 0.27% to 0.41%. This range was due to intraspecific variation, which was noted only for E. caballus. For pairwise comparisons within this family, estimates of sequence divergence ranged from 0% (E. hemionus onager vs. E. h. kulan) to 7.8% (E. przewalskii vs. E. h. onager). Trees constructed according to the parsimony principle, on the basis of 31 phylogenetically informative restriction sites, indicate that the three extant zebra species represent a monophyletic group with E. grevyi and E. burchelli antiquorum diverging most recently. The phylogenetic relationships of E. africanus and E. hemionus remain enigmatic on the basis of the mtDNA analysis, although a recent divergence is unsupported.      

Pathogenic effect of enterotoxigenic Escherichia coli and Escherichia coli causing infantile diarrhoea.

Macroscopic, light and electron microscopic alterations in ligated rabbit intestinal loops challenged with five standard enterotoxigenic Escherichia coli (ETEC) and twenty-three enteropathogenic E. coli (EEC-I) strains, freshly isolated from infantile enteritis cases, were investigated. Only two O26 : K60 : H11 strains produced enterotoxin. Their living cultures, sterile filtrates of the fluid medium and ultrasonic lysates of the bacteria resulted in pronounced hypersecretion of the intestinal epithelium followed by fluid accumulation and loop dilatation. These two E. coli strains, similarly as the other loop-negative EEC-I strains, were able to penetrate into the intestinal epithelium. In contrast to the standard ETEC strains, the EEC-I bacteria, adhering to the brush border, intruded into the microvilli, multiplied on the outer epithelial cell membrane making close contact with it and, causing, shedding of microvilli, penetrated into enterocytes becoming enclosed in membrane-bound phagosome-like vacuoles, appeared in the lamina propria and elicited mild focal polymorphonuclear infiltration.     

Microelectrode investigations of learning phenomena in snail (Helix pomatia) neurones.

We have examined changes of postsynaptic potentials and of pattern activity of the identified silent and oscillatory snail neurones in Helix pomatia during conditioning. Local changes of EPSP or IPSP have been recorded during association following the first stimulus in the silent cells, whereas spike discharges could be observed in response to the 2nd stimulus. In the oscillatory neurones changes of pattern activity have been recorded following the 2nd stimulus, while the first stimulus proved to be ineffective. The formation of temporary connections of snail neurones seemed to be a specific phenomenon, because it was necessary to pair stimuli of different inputs for the development of these modifications. These plastic changes seemed to depend on the interstimulus as well as on the intertrial intervals. Our experimental data underline the probable role of the stimulus parameters and of the electrical properties of neurones during the formation of learned neuronal responses.     

Cassava leaf harvesting as vegetables; a cause of vulnerability of cassava plant to cassava mosaic disease and eventual yield reduction: Ernte von cassavablättern als gemüse; eine ursache für die anfälligkeit der cassavapflanze für die cassava-mosaikkrankheit und für spätere ertragseinbußen

The consequence of harvesting young leaves of cassava as vegetable on the vulnerability of the crop to cassava mosaic disease (CMD) and on storage root yield was investigated using 30 cassava genotypes planted in IITA fields located in the humid forest (Port Harcourt?:?Onne), forest-savannah transition (Ibadan), southern guinea savannah (Mokwa) and northern guinea savannah (Zaria) agroecologies in Nigeria. Tender apical leaves and shoots of the cassava genotypes were removed from forty plants per cassava genotype with the same number of plants considered as control. Whitefly infestation, disease incidence (DI) and symptom severity (ISS) of the disease were assessed at monthly interval for six months and also at the ninth month after planting (MAP). Yield reduction due to this treatment was calculated as percentage harvest index (HI). Whitefly population fluctuated throughout the period of observation at all locations with higher population obtained generally for treated plants compared to control plants. Sprouting leaves of some treated genotypes were observed with severe mosaic symptoms, while corresponding control showed no mosaic symptoms. Contrarily, no remarkable difference was observed in Zaria between the mean ISS of treated and control cassava genotypes. There was a highly significant difference (P?<?0.01) in DI and ISS among cassava genotypes across all locations. Also, there was a highly significant interaction (P?<?0.01) in symptom severity between location (loc) and genotype, genotype and treatment (trt), loc and trt. Interaction between loc, genotypes and trt with regard to DI was highly significant at 2, 3 and 4 MAP, while with ISS, the interaction was highly significant all through the counting period. There was a positive relationship between DI and ISS on plants of genotypes 96/1039 and ISU. The percentage HI (27.4) of treated plants of genotype 95/0166 in Ibadan was remarkably lower than the value obtained for corresponding control (41.9) plants. Also, sharp distinction in% HI of treated (39.5) and control (43.8) ISU was observed in Onne with their respective ISS values as 3.7 and 3.2. Therefore, harvesting tender apical leaves and shoots of cassava as vegetables should be discouraged as it increases the severity of CMD infection in the regenerating shoots of cassava with attendant storage root yield reduction.     

Ethological Features of the Ontogenesis of the Locomotor System in Bony Fish (by the Example of the Rainbow Trout Oncorhynchus mykiss Walbaum)

Biology Bulletin - The features of the structural adaptive changes in the somatic muscles of rainbow trout are presented at various stages of early post-hatching ontogenesis. The development of the...     

Comparative evaluation of the effectiveness of the treatment of gastroduodenal Campylobacter infection in children

Schemes developed by the authors for antibacterial therapy of gastroduodenal bacterosis caused by Campylobacter spp. in children are described. The data on the treatment of 56 patients with duodenal ulcer and gastroduodenitis are presented. The efficacy of the treatment with medicines under the control of the clinical, endoscopic and microbiological indices was compared. The study showed that De-Nol, furazolidone and combination of trichopol (metronidazole) with vicair were the most efficient drugs for therapy of children with such diseases.     

Giant multimodal heart motoneurons of Achatina fulica: a new cardioregulatory input in pulmonates.

The regulation of the heartbeat by the two largest neurons, d-VLN and d-RPLN, on the dorsal surface of visceral and right parietal ganglia of Giant African snail, Achatina fulica, was examined. Using the new method of animal preparation, for the first time, discrete biphasic inhibitory-excitatory junction potentials (I-EJPs) in the heart and several muscles of the visceral sac were recorded. The duration of hyperpolarizing phase (H-phase) of biphasic I-EJPs was 269+/-5.6 ms (n=5), which is 2-3 times less than that of the cholinergic inhibitory JPs (682+/-68.5 ms, n=5). The H-phase of I-EJPs was not altered by the application of atropine, picrotoxine, succinylcholinchloride, D-tubocurarine and tetraethylammonium or substitution of Cl(-) ions. Even the low-frequency neuronal discharges (1-2 imp/s) evoked significant facilitation and potentiation of the H-phase. Between the multimodal neurons d-VLN/d-RPLN and mantle or visceral organs there is evidence of direct synaptic connections. These neurons were found to have no axonal branches in the intestinal nerve as once suspected but reach the heart through several other nerves. New giant heart motoneurons do not interact with previously identified cardioregulatory neurons.