Subject(s)
Acquired Immunodeficiency Syndrome/virology , Blood Platelets/virology , HIV-1/isolation & purification , Megakaryocytes/virology , Thrombocytopenia/virology , Acquired Immunodeficiency Syndrome/complications , Acquired Immunodeficiency Syndrome/immunology , Antigen-Antibody Complex/immunology , Blood Platelets/cytology , Blood Platelets/immunology , Female , Follow-Up Studies , HIV Antigens/analysis , HIV Envelope Protein gp41/analysis , Humans , Male , Thrombocytopenia/complications , Thrombocytopenia/immunologyABSTRACT
The Yeast phase of Histoplasma capsulatum has stringent growth requirements. Transition from mycelium to yeast takes place only in the presence of cysteine and can be blocked by the -SH groups inhibitor p-chloromercury-phenylsulfonic acid (PCMS). Ultrastructural studies show lysis and degeneration of PCMS treated mycelium grown at 37 degrees C for 24 hours. Only 50% of PCMS treated mycelium appear degenerate when grown at 34 degrees C for 24 hours. The remaining cells have normal morphology with only slight changes in the cell wall structure. The effect of PCMS is permanent and hereditary. Mice injected with PCMS treated mycelium do not develop disease and are resistant to virulent strains of H. capsulatum when challenged.
Subject(s)
4-Chloromercuribenzenesulfonate/pharmacology , Histoplasma/drug effects , Sulfhydryl Reagents/pharmacology , Cell Differentiation/drug effects , Depression, Chemical , Histoplasma/genetics , Histoplasma/growth & development , Histoplasma/ultrastructure , Microscopy, ElectronABSTRACT
The ultrastructural changes which occur during the mycelium to yeast transition in Histoplasma capsulatum induced by a temperature shift from 25 degrees C to 34 degrees C are described and compared to those observed after a temperature shift from 25 degrees C to 37 degrees C. 24 hours after the temperature shift to 34 degrees C only 8% of the cells are lysed. However, many mitochondria have lost their characteristic elongated form and have become rounded. Vesicular cristae which are no longer oriented parallel to the long axis of the mitochondria are also observed. In contrast a temperature shift from 25 degrees C to 37 degrees C induces lysis of 70% of the cells; mitochondria are rarely observed in the remaining cells. These ultrastructural changes can be correlated with the uncoupling of oxidative phosphorylation and the production of heat shock proteins.
Subject(s)
Histoplasma/ultrastructure , Fungal Proteins/metabolism , Gene Expression Regulation, Fungal , Heat-Shock Proteins/metabolism , Histoplasma/growth & development , Histoplasma/metabolism , Oxidative Phosphorylation , TemperatureABSTRACT
Isolation of virus-like particles from sera of anti-HCV positive patients and their ultrastructural characterization are reported. Particles were identified in sera of 5 out of 6 patients tested. Immunoelectron microscopy assay revealed small aggregates of viral particles. Size and morphological criteria suggest that these particles can be classified as Togaviridae.
Subject(s)
Hepacivirus/isolation & purification , Hepatitis C/microbiology , Hepacivirus/classification , Hepacivirus/ultrastructure , Hepatitis C/etiology , Hepatitis, Chronic/microbiology , Humans , Togaviridae/classificationABSTRACT
Ultrastructural changes observed during the first 24 hours of mycelium to yeast transition in the dimorphic fungus Histoplasma capsulatum are reported. During this period the plasma membrane becomes undulated and the cell wall loses its characteristic fibrous outer layer. At 8 h the ordered lamellar structure of the mitochondria is no longer apparent. 24 h after the temperature shift 70% of the cells are lysed. The remaining cells contain many cytoplasmic membrane structures; mitochondria are rarely observed. These morphological changes are probably correlated with the physiological events characteristic of mycelial to yeast transition.
Subject(s)
Histoplasma/ultrastructure , Cell Wall/ultrastructure , Histoplasma/physiology , Microscopy, Electron , Mitochondria/ultrastructure , TemperatureABSTRACT
The ultrastructural morphology of the early phases of mycelium-yeast transition in Histoplasma capsulatum after a temperature shift from 25 degrees C to only 34 degrees C is described. Under this condition of lower temperature oxidative phosphorylation is not completely uncoupled and maximum production of heat shock proteins (hsp) occurs. 24 h after temperature shift more than 90% of the cells still appear vital. Alterations in the organization of the mitochondrial cristae are the only ultrastructural changes observed in these cells. In contrast, 70% of the cells degenerate 24 h after a temperature shift from 25 degrees C to 37 degrees C and in the remaining cells mitochondria are rarely observed. These observations are discussed in relation to the production of hsp, the uncoupling of oxidative phosphorylation and the virulence of different strains of H. capsulatum.
Subject(s)
Histoplasma/ultrastructure , Hot Temperature , Heat-Shock Proteins/biosynthesis , Histoplasma/growth & development , Histoplasma/metabolism , Oxidative PhosphorylationABSTRACT
The ultrastructural changes which occur during the first 24 h of mycelium to yeast transition have been studied in the dimorphic fungus Histoplasma capsulatum. A temperature shift controls mycelial to yeast transition. During the first 24 h respiratory rate, ATP and cytochrome concentration fall to very low levels. Ultrastructural observations showed that the plasma membrane became undulated and the cell wall lost its characteristic fibrous outer layer. At 8 h the ordered lamellar structure of the mitochondria was no longer apparent. 24 h after the temperature shift 70% of the cells were lysed. The remaining cells contained many cytoplasmic membrane structures; mitochondria were rarely observed. These changes are considered to be the morphological expression of the physiological events characteristic of stage one in mycelial to yeast transition.
