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Biomedical subjects

M Rýc

Publications and source records attributed to M Rýc.

At least 37 records · Page 2Linked to original sources
PubMed1983

Biological activity of synthetic subunits of Streptococcus peptidoglycan. II. Relation of peptidoglycan subunits and analogues to fever effect and induction of tolerance.

A series of synthetic subunits and analogues of streptococcal peptidoglycan was prepared and used in fever and tolerance experiments on rabbits. The lengthening of the chain of the peptide moiety of peptidoglycan did not result in pyrogenic activity, except for hexapeptide. Attachment of the muramyl residue rendered the peptides pyrogenic. The activity of such materials varied in degree and was rather in an indirect relation to peptide chain length. A change in the configuration of C4-OH or C3-OR in the muramyl residue resulted in a profound decrease in pyrogenicity. No inhibitory effect of N-acetylmuramyl-D-alanyl-D-isoglutamine on muramyldipeptide (MDP) pyrogenicity could be demonstrated. Repeated administration of MDP resulted in the induction of tolerance to the pyrogenicity of this substance in rabbits. These animals were not tolerant to the pyrogenicity of peptidoglycan. Nontolerance was also observed in reciprocal experiments with these materials as well as in trials with hexapeptide and peptidoglycan given in either order. The data are consistent with the assumption that peptidoglycan contains more than one biologically active subunit. There is a structure-to-function relationship. The knowledge of the biological effects of the synthetic analogues is essential for the prospect of their use under model or human conditions.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1982

Electron microscopic study of the location of the Fc-reacting factor on group A streptococci.

The presence of the Fc-reacting factor was demonstrated on four out of five different group A Streptococcus strains using ferritin-labelled immunoglobulin G. A comparison of the results obtained by this electron microscopic technique with Fc-reacting factor detection results obtained with hydrochloric acid extracts of cells in passive haemagglutination on sensitized red cells, showed that not only hydrochloric acid extractable but also non-extractable Fc-reacting factor can be present on the group A Streptococcus cell. Out of several IgGs tested, only rabbit and swine IgGs bound to Fc receptors of group A Streptococcus walls. The Fc-reacting factor is ultrastructurally localized on the tips of the filamentous protrusions forming the outermost layer of the Streptococcus wall. The involvement of the Fc portion of IgG in the reaction was demonstrated by a positively reacting sandwich arrangement in which Streptococcus cells were incubated with rabbit antiferritin before being treated with ferritin.

Cell Wall↗
PubMed1981

Combination effect with some aminoglycoside antibiotics.

Strains of resistant species -- Staphylococcus aureus and Streptococcus faecalis -- isolated from material of nosocomial infections in the surgical department of a Prague hospital were tested for combined effect with further chemotherapeutics. The same concerned Ps, aeruginosa noted, at present, by a high degree of resistance. In Ps. aeruginosa it was the combination sisomicin-carfecillin that proved a success in 50 p. c. of cases as well as that of sisomicin-doxycyclin. At the same time the authors draw attention to the possibility of antagonistic action of the combination sisomicin-chloramphenicol in a third part of the strains tested. Potentiation of the effect in Staphylococcus aureus strains was observed also in the combination sisomicin-carfecillin in more than one half of the strains tested and in case of sisomicin-doxycyclin in one third of the strains. In Streptococcus faecalis strains sisomicin was combined with amoxycillin, carbenicillin, carfecillin and doxycyclin; synergistic action being observed with all those combinations in more than one half of strains tested. No antagonism was registered in those cases. (Ta.).

Aminoglycosides↗
PubMed1981

Ultrastructural study of interaction of group A streptococci with tissue culture cells.

Submicroscopic aspects of the adherence of Group A streptococci to HEp-2 cells and the time sequence of their further interaction with these cells were studied. The M+ variant of streptococci, characterized by the presence of filamentous protrusions on the cell wall, displayed a high capacity for adherence, in contrast to the M- variant of the same strain, where adherence was low. The first stage of the interaction between M+ variant of Group A streptococci and HEp-2 cells was adherence of the filamentous protrusions of the bacterial cell wall to host cell cytoplasmic membrane; this was followed by closer contact of the streptococcus cell wall with HEp-2 cell surface. Continuing incubation led to the development of invaginations in the cytoplasmic membranes of HEp-2 cells, into which streptococci gradually penetrated. Ingestion of streptococci into the forming pseudovacuoles of the host cell was accompanied by bacterial cell division, culminating in total disintegration of the host cell and release of the streptococci into the medium. At all stages of the interaction there was a pronounced tendency to form multiple contacts between the surface structures of the streptococcus cell and the membrane structures of the animal cell being attacked.

Cell Division↗
PubMed1980

Immunoelectron microscopic study of the location of group-specific and protein type-specific antigens of group B streptococci.

The ultrastructural location of the group-specific polysaccharide and the type-specific protein antigens R and X of group B streptococci was studied by means of the direct immunoferritin technique. The group-specific antigen was located on the outer wall layer. The specificity of the reaction was proved by the inhibition of labelling after absorption of the antibody-ferritin conjugate with group B polysaccharide. On the other hand, the demonstration of the polysaccharide was not sterically hindered by protein type antigens. As with group A and C streptococci the group polysaccharide could be localized on both the outer and inner surfaces of isolated walls. The protein antigens R and X were also demonstrated on the wall surface. The specificity of the reaction was ensured by making use of the enzymic sensitivity of these antigens. The location of the R protein on long filaments protruding from the cell surface resembles that of M protein of group A streptococci. In contrast to the group polysaccharide both the R and X protein antigens are localized only on the outer surface of isolated walls.

Antigens, Bacterial↗
PubMed1980

Adherence of group A streptococci to epithelial cells in tissue culture.

Using the HEp-2 cell line system the factors and mechanisms of group A Streptococcus adherence had been studied. It was shown that high adherence was chiefly found in strains showing attributes of virulence (presence of M protein, growth in human blood, lethality for mice). The data supplied by experiments with pepsin and LTA suggest that there exist at least two mechanisms of adherence.

Adhesiveness↗
PubMed1979

Biological activity of synthetic subunits of streptococcus peptidoglycan. I. Pyrogenic and thrombocytolytic activity.

The ability of some synthetically prepared analogues of Streptococcus peptidoglycan subunits (dipeptide, tetrapeptide, glycodipeptide and glycotetrapeptide) to cause fever in rabbits and lysis of rabbit blood platelets was studied. While di- and tetrapeptides did not exhibit these activities, glycodipeptides and glycotetrapeptides displayed pyrogenic and thrombocytolytic activities comparable with those of natural peptidoglycans.

Blood Platelets↗
PubMed1979

Infantile gastroenteritis virus.

The authors demonstrated presence of virus particles of 55--75 nm manifesting morphological properties of the virus of infantile gastroenteritis (rotavirus, orbivirus, reo-like virus) by means of the electron microscopy, when investigating samples of stools of children sufferring from non-bacterial diarrheal diseases. Stool extracts were incubated with commercial gamma globulins or with convalescent sera provoking formation of extensive immunocomplexes. The complexes do not form when stool extracts are incubated with sera obtained from initial stages of the disease. This finding is an evidence of the presence of the virus in question among our population.

Age Factors↗
PubMed1978

Fine structure of imbibed sclerotial cells of Claviceps purpurea (Fr.) Tul revealed by freeze-etching.

The fine structure of the cortex of the natural sclerotium of Claviceps purpurea was studied. The cell wall of sclerotial cells is thickened due to overproduction of the fibrillar component of the wall. The intracellular spaces of the cortex tissue form a continuous system which is apparently instrumental in mediating communication between the growing sclerotium and the external milieu. The cytoplasmic membrane of imbibed sclerotial cells carriers abundant signs of secretory activity. Secretion vesicles, the content of which is discharged into external space, apparently contain exo 1,3-glucanase. Cytoplasmic vesicles migrating toward the plugged pores of the thickened septa apparently involve hydrolase secretion too. Spherosomes with lipid content are a predominant component of the cytoplasm of sclerotial cells. The activity of the membrane systems of imbibed cells indicates that the mobilization of lipids sets in only after activation of the hydrolases. Findings of phagocytosis of lipid granules by vacuoles are relatively frequent so that lipolysis might proceed in the vacuoles. Alkaloids could not be detected with the aid of freeze-etching.

Cell Wall↗