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Biomedical subjects

M Wittner

Publications and source records attributed to M Wittner.

At least 181 records · Page 10Linked to original sources
PubMed1971

Sites of cytoplasmic ribonucleoprotein-filament assembly in relation to helical body formation in axenic trophozoites of Entamoeba histolytica.

Axenic trophozoites of Entamoeba histolytica showed increased logarithmic growth but absence of "chromatoid" material (stacked helical arrays of ribonucleoprotein [RNP]) when grown in an all-liquid monophasic culture. Organisms grown in a liquid overlay on a semisolid slant (biphasic medium) showed slow logarithmic growth and the presence of chromatoid material. Chromatoid material accumulated in the rapidly growing trophozoites from monophasic culture during treatment with the Vinca alkaloid, vinblastine. Many of the glycogen-free regions of vinblastine-treated trophozoites as well as, to a lesser degree, of normal cells grown in monophasic and biphasic cultures, contained free ribosomes and randomly oriented 60 A filaments. As ribonucleoprotein assumed the packed helical configuration, areas consisting of parallel, packed filaments could be detected adjacent to and continuous with the ordered RNP arrays. This arrangement could be visualized most frequently in vinblastine-treated trophozoites grown in monophasic cultures. Depending on the tilt of the section with respect to the longitudinal axis of individual helices, 60 A filamentous material could be demonstrated associated with the RNP helices. Localization of ribonucleoprotein precursors was followed by means of high resolution radioautography with uridine-(3)H and cytidine-(3)H. With a short (30-min) pulse, label could be visualized only over the glycogen-free areas containing free ribosomes and filaments. With 60-min pulses, label could also be seen over the packed helical arrays. With 30-min pulses followed by a 60-min cold chase, label was seen chiefly over RNP helices. It is postulated that the areas containing ribosomes and filaments represent sites of assembly of the RNP helices possibly on a filament protein column. The possibility that the final helical configuration may be due to a property of this protein is suggested.

Animals↗
PubMed1970

Ultrastructure of bacterized and axenic trophozoites of Entamoeba histolytica with particular reference to helical bodies.

Electron microscopy of bacterized and axenic trophozoites of Entamoeba histolytica showed only slight differences in ultrastructure between the two. As with other species of Entamoeba so far studied, this species lacks typical mitochondrial structures and formed endoplasmic reticulum. Dense clusters of glycogen particles are especially characteristic in axenic amebas. Microtubular structures 360 A in diameter appear randomly oriented in both bacterized and axenic trophozoites. Ribonucleoprotein (RNP) bodies are of two typical forms-elongate, parallel arrays of helices (the classical chromatoid bodies), and short helical fragments. Both kinds of helix show a recurring pitch angle of 68-80 degrees and an over-all diameter of 480 A. RNP particles comprising the helices average 180 A in diameter. The longitudinal axes of adjacent helices are 440 A apart. Following RNase digestion of water-soluble methacrylate sections, helices show a core approximately 60 A in diameter. Short helices are also associated with digestive vacuoles. Free RNP particles per se are never seen within digestive vacuoles, but intact short helices are frequently detected closely associated with the external membrane of digestive vacuoles. In some cases, continuation of externally intact helical forms could be related to filamentous material within the vacuole. Acid phosphomonoesterase activity could be demonstrated within digestive vacuoles where deposition of reaction product is especially intense on the filamentous material.

Acid Phosphatase↗
PubMedDate not supplied

Myocardial expression of endothelin-1 in murine Trypanosoma cruzi infection.

Chagas' disease, caused by Trypanosoma cruzi, is an important cause of myocarditis and chronic cardiomyopathy and is accompanied by microvascular spasm and myocardial ischemia. We reported previously that infection of cultured endothelial cells with T. cruzi increased the synthesis of biologically active endothlein-1 (ET-1). In the present study, we examined the role of ET-1 in the cardiovascular system of CD1 mice infected with the Brazil strain of T. cruzi and C57BL/6 mice infected with the Tulahuen strain during acute infection. In the myocardium of infected mice myonecrosis and multiple pseudocysts were observed. There was also an intense vasculitis of the aorta, coronary artery, smaller myocardial vessels and the endocardial endothelium. Immunohistochemistry studies employing anti-ET-1 antibody revealed increased expression of ET-1 that was most intense in the endocardial and vascular endothelium. Elevated levels of mRNA for preproET-1, endothelin converting enzyme and ET-1 were observed in the same myocardial samples. Plasma ET-1 levels were significantly elevated in infected CD1 mice 10-15 days post infection. These observations suggest that increased levels of ET-1 are a consequence of the initial invasion of the cardiovascular system and provide a mechanism for infection-associated myocardial dysfunction.

Animals↗
PubMedDate not supplied

Fatal cryptosporidiosis complicating Kaposi's sarcoma in an immunocompromised man.

Fatal cryptosporidiosis in a bisexual immunosuppressed man with disseminated Kaposi's sarcoma and intractable diarrhea is described. Cryptosporidium sp. was isolated from the stool antemortem by Sheather's floation technique. This parasite should be considered in immunosuppressed hosts with chronic diarrhea when routine methods fail to demonstrate etiologic agent. Since this organism is already infectious when passed, stool precautions should be maintained.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Ribosomal RNA sequences of Enterocytozoon bieneusi, Septata intestinalis and Ameson michaelis: phylogenetic construction and structural correspondence.

The microsporidian species Enterocytozoon bieneusi, Septata intestinalis and Ameson michaelis were compared by using sequence data of their rRNA gene segments, which were amplified by polymerized chain reaction and directly sequenced. The forward primer 530f (5'-GTGCCATCCAGCCGCGG-3') was in the small subunit rRNA (SSU-rRNA) and the reverse primer 580r (5'-GGTCCGTGTTTCAAGACGG-3') was in the large subunit rRNA (LSU-rRNA). We have utilized these sequence data, the published data on Encephalitozoon cuniculi and Encephalitozoon hellem and our cloned SSU-rRNA genes from E. bieneusi and S. intestinalis to develop a phylogenetic tree for the microsporidia involved in human infection. The higher sequence similarities demonstrated between S. intestinalis and E. cuniculi support the placement of S. intestinalis in the family Encephalitozoonidae. This method of polymerized chain reaction rRNA phylogeny allows the establishment of phylogenetic relationships on limiting material where culture and electron microscopy are difficult or impossible and can be applied to archival material to expand the molecular phylogenetic analysis of the phylum Microspora. In addition, the highly variable region (E. coli numbering 590-650) and intergenic spacer regions in the microsporidia were noted to have structural correspondence, suggesting the possibility that they are coevolving.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

A cell culture system for study of the development of Toxoplasma gondii bradyzoites.

Toxoplasma gondii is a ubiquitous apicomplexan parasite and a major opportunistic pathogen under AIDS-induced conditions, where it causes encephalitis when the bradyzoite (cyst) stage is reactivated. A bradyzoite-specific Mab, 74.1.8, reacting with a 28 kDa antigen, was used to study bradyzoite development in vitro by immuno-electron microscopy and immunofluorescence in human fibroblasts infected with ME49 strain T. gondii. Bradyzoites were detected in tissue culture within 3 days of infection. Free floating cyst-like structures were also identified. Western blotting demonstrated the expression of bradyzoite antigens in these free-floating cysts as well as in the monolayer. Bradyzoite development was increased by using media adjusted to pH 6.8 or 8.2. The addition of gamma-interferon at day 3 of culture while decreasing the total number of cysts formed prevented tachyzoite overgrowth and enabled study of in vitro bradyzoites for up to 25 days. The addition of IL-6 increased the number of cysts released into the medium and increased the number of cysts formed at pH 7.2. Confirmation of bradyzoite development in vitro was provided by electron microscopy. It is possible that the induction of an acute phase response in the host cell may be important for bradyzoite differentiation. This system should allow further studies on the effect of various agents on the development of bradyzoites.

Animals↗