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The evaluation of potential pathogenicity of A. hydrophila strains isolated from healthy fish was carried out on the basis of their ability to produce enterotoxins, beta — haemolysins and to haemagglutinate blood cells in humans and guinea pigs. The studies comprised 29 strains of A. hydrophila isolated from 67 fish from 6 fish — breeding stations in the Olsztyn province. No correlation was found between the ability of the examined strains to agglutinate human and guinea pig erythrocytes, and the enterotoxicity and hemolitic activity. Some correlation was found between the enterotoxicity of the strains and their hemolitic activity. Incubation of A. hydrophila strains at temp. 25°C allows to detect more enterotoxic strains (31% strains) than at temp. 37°C (13% strains).
The usefulness of human erythrocytes taken from donors of different blood groups was assessed in respect to their capacity to reat with a suspension of rabbit organs derived from infected animals with RHDV. According to the authors HA test should be carried out in a 0.85 per cent NaCl solution (pH = 7.0) at room temperature and the results should be read after 2—3 hours.
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Pneumocystis carinii w swietle najnowszych badan

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A brief history of studies on Pneumocystis carinii was presented with particular reference to the investigations which had revealed its fungal nature, host specificity, and antigenic variation in the major surface glycoprotein. Furthermore, the problem of hitherto unknown reinfection with P. carinii as opposed to reactivation of latent infection was discussed.
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The very beginnings of plant virus nomenclature and classification were briefly mentioned and different points of view on virus names were commented on, and exemplified by 12 different proposals for the name of tobacco mosaic tobamovirus. The history and activities of the International Committee on Taxonomy of Viruses were briefly reviewed, stressing its legislation and regulation efforts. In the main part of the lecture current regulations and proposals of ICTV were presented concerning introduction of species concept and species-genus-family-order system of virus taxonomy, as well as creating a single taxonomy system for all the viruses. The main results of some research works in the field of genetics and molecular biology were reviewed forming the basis for understanding genetic diversification and speciation in plant viruses by comparing a gene structure and expression mechanisms. The proposed species names as well as those of genus, family and order are cited. Finally, current trends in virus taxonomy were presented. The implications of so-called "super-groups" and some additional proposals for new virus orders and families were discussed. The situation in the taxonomy of plant viroids was briefly commented on.
A simple and quick method of viral DNA purification from RK 13 infected with NIA-3 strain of ADV cell culture yielded DNA which was easily digested with its enzyme restriction. Moreover, it was of a sufficient purity for a restriction pattern (RFP) analysis. The purified DNA was labelled with photobiotin to obtain a biotinylated genetic probe. The full length DNA probe that was developed was found to be very sensitive and specific when it was used for hybridization with ADV DNA. Furthermore, the forenamed biotinylated probe greatly enhanced the detection limits of restriction fragments compared to RFP analysis in ethidium bromide stained agarose gel. These results indicate that the described probe can be used for analysis and characterization of ADV genomes even if only minute amounts of viral DNA are available.
In two farms (A and B) losses of calves in the first 2—3 days after birth caused by diarhhoea were 25,2% and 36,5%. Bacteriological examinations of the intestines revealed an especially high concentration (2,4 X 10⁹ — 3,6 X 10¹⁰ cells/g) of the highly toxinogenic „in vitro” C. perfringens A. Contents of intestines were, however, free of lethal toxins. Examinations of pathological properties of C. perfringens A isolates showed that they produced strong alpha, theta and kappa toxins, and the majority of isolates additionally produced mi and ni toxins. Lack of toxins in the intestines may result from their quick binding with body tissues. This observation is confirmed by the high effectiveness of prophylatic measures i.e. immunization of animals against alpha toxin (article in preparation). The result point to the role of nonenterotoxinogenic strains of C. perfringens A, producing alpha toxin, in the etiology of diarrhoea of newborn calves.
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