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A M Fiskin

Publications and source records attributed to A M Fiskin.

27 records · Page 2Linked to original sources
PubMed1968

Autocorrelation functions of noisy electron micrographs of stained polynucleotide chains.

Polyuridylic acid was deposited on carbon films in the presence of the thallous salt of mercury-p-dihydroquinone-O,O-diacetic acid under conditions leading to attachment of one of these molecules to each nucleotide. In electron micrographs of the stained polynucleotide chain, detail was obscured by the noise resulting from the substrate. Optically obtained autocorrelation functions of the distribution of density along the strands revealed peaks suggesting a structural regularity of 8 angstroms; this was interpreted as the internucleotide spacing.

Hydroquinones↗
PubMedDate not supplied

Ultrastructural cytology of Basidiobolus haptosporus: morphology and electron cytochemistry of microbodies.

Vegetative and reproductive cells of Basidiobolus haptosporus possess naturally occurring organelles identified as microbodies. Cells of four other species of the genus contained morphologically indistinguishable organelles. Microbodies were invariably present in cells of the fungi grown on routine mycological media. The constitutive microbody was characterized by a single, intensely electron-opaque crystalloid body which rapidly enlarged to fill the organellar compartment. The microbody then underwent degeneration by an autolytic-like process. Growth of the fungi on xanthine and its catabolites as sole nitrogen sources (but not urea) greatly enhanced the production of new microbodies in which protein was initially accumulated as paracrystalline arrays. These inclusions then underwent reorganization and compaction to form crystalloid bodies. Key enzymes of the purine degradation pathway are believed to be core proteins of the crystalloid. D-amino acid oxidase, alpha-hydroxy acid oxidase, xanthine oxidase and urate oxidase (but not catalase) were detected cytochemically in mature microbodies. Significant levels of phosphorus and molybdenum were present in the microbody crystalloid by X-ray dispersive microanalysis; iron and copper were not detected. The ability of Basidiobolus species to assimilate xanthine and its catabolites might explain their ecological association with the gut and cloacal contents of various amphibia, reptiles and fish.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Double-membraned vesicles and their possible role in the ontogeny of microbodies of Basidiobolus haptosporus.

A concomitant but transient occurrence of large numbers of double-membraned vesicles with immature, culturally induced microbodies was demonstrated in thin sections of Basidiobolus haptosporus soon after transfer of the fungus to a defined medium containing xanthine or its catabolites as the sole source of nitrogen. Double-membraned vesicles were rapidly formed as derivatives of endoplasmic cisternae later to occur free in the cytoplasm, often as the most predominant cytoplasmic inclusion. Densitometric measurements revealed that heavy metal-binding cytoplasmic constituents were concentrated within the vesicular lumen. Most of the double-membraned vesicles appeared to undergo degeneration; they were rare to absent in thin sections of older cells. At times, double-membraned vesicles were seen connected to newly formed microbodies in a manner suggesting ontogenic relationships. The outer vesicular membrane was continuous with the single limiting membrane of the microbody via a short tubule. We interpret these observations as empirical ultrastructural evidence to suggest that some double-membraned vesicles become specialized and function as precursor inclusions in the biogenesis of new microbody populations committed to purine salvage.

Basidiomycota↗
PubMedDate not supplied

Electron cytochemical demonstration of phosphatase activity with microbody membranes of Basidiobolus haptosporus.

Growth of cells of the potentially zoopathogenic fungus Basidiobolus haptosporus on a nutritionally defined medium with xanthine or urate as the nitrogen source results in greatly increased populations of microbodies. Modified Gomori procedures at the electron microscopic level suggested the single limiting membrane (and in some cases the granular matrix) of immature microbodies to be the exclusive subcellular locale(s) of alkaline phosphatase, 5'-nucleotidase and nucleoside diphosphatase activities. When grown in the presence of low inorganic phosphate, additional alkaline phosphatase activity was further identified cytochemically at and along profiles of endoplasmic reticulum and on inclusions previously described as "double-membraned vesicles". Cytochemical localization of acid phosphatase at microbody membranes was minimal if not ambiguous; Mg++-dependent adenosine triphosphatase and glucose-6-phosphatase were not identified at these locales. Quantitative biochemical estimates of alkaline phosphatase activity levels in particulate fractions initially increased with age of cells, perhaps as a function of the cultural induction and marked increase in immature microbody populations. We suggest that this enzyme may participate in some manner with protein translocation mechanisms associated with microbody biogenesis, ontogeny, and/or physiological function.

5'-Nucleotidase↗