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J Pangborn

Publications and source records attributed to J Pangborn.

10 recordsLinked to original sources
PubMed1977

Dorsal-ventral differentiation in Simonsiella and other aspects of its morphology and ultrastructure.

The morphology and ultrastructure of the aerobic, Gram-negative multicellular-filamentous bacteria of the genus simonsiella were investigated by scanning and transmission electron microscopy. The flat, ribbon-shaped, multicellular filaments show dorsal-ventral differentiation with respect to their orientations to solid substrata. The dorsal surface, orientated away from the substrate, is convex and possesses an unstructured capsule. The ventral surface, on which the organisms adhere and glide, is concave and has an extracellular layer with fibrils extending at right angles from the cell wall. The cytoplasm in the ventral region contains a proliferation of intracytoplasmic membranes and few ribosomes in comparison to the cytoplasm in other parts of the cell. Centripetal cell wall formation is asymmetrical and commences preferentially in the ventral region. Quantitative differences in morphology and cytology exist among selected Simonsiella strains. Functional aspects of this dorsal-ventral differentiation are discussed with respect to the colonization and adherence of Simonsiella to mucosal squamous epithelial cells in its ecological habitat, the oral cavities of warm-blooded vertebrates.

Animals↗
PubMed1975

Scanning electron microscopy of fruiting body formation by myxobacteria.

Scanning electron microscopy was used to follow fruiting body formation by pure cultures of Chondromyces crocatus M38 and Stigmatella aurantica. Vegetative cells were grown on SP agar and then transferred to Bonner salts agar for fructification. Fruiting in both species commences with the formation of aggregation centers which resemble a fried egg in appearance. In Chondromyces the elevated center or "yolk" region of the aggregation enlarges into a bulbous structure under which the stalk forms and lengthens. At maximum stalk height the bulb extends laterally as bud-like swellings appear. These are immature sporangia and are arranged in a distintive radial pattern around the top of the stalk. This symmetry is lost as more sporangia are formed. Stigmatella does not form a bulb; rather the yolk region of the aggregation center projects upward to form a column-like stalk which is nearly uniform in diameter throughout its length. At maximum stalk height, the terminus of the stalk develops an irregular pattern of bud-like swellings. These differentiate into sporangia. Stalks of 2-week-old mature fruiting bodies of both species appear to be cellular in composition. Stereomicrographs suggest orientation of these cells parallel to the long axis of the stalk. Stalks of 8-week-old fruiting bodies of Chondromyces were acellular and consisted of empty tubules, suggesting that the cells undergo degeneration with aging of the fruiting body.

Microscopy, Electron, Scanning↗
PubMed1967

Filamentous cells of Escherichia coli formed in the presence of mitomycin.

The effects of mitomycin C on cell elongation of Escherichia coli B were studied. Filament formation was most marked in cultures treated with a moderate level (1 mug/ml) of the antibiotic, becoming less obvious at higher levels (10 mug/ml). Cells treated with a bacteriostatic concentration (0.1 mug/ml or less) of mitomycin C were also significantly elongated. The filamentous or elongated cells appeared to lack septa, since their spheroplasts were considerably larger than those formed from normal cells. The appearance of empty spheres also indicated some defects in the surfaces of the filamentous cells. Electron micrographs of the filaments revealed a characteristic difference in the arrangement of the nuclei in the filaments formed in the presence of low (0.1 mug/ml) and high (5 mug/ml) concentrations of mitomycin C. The filaments formed by the low level of mitomycin C had normal well-defined nuclear bodies distributed along the long axis, whereas those formed by the elevated level of the antibiotic contained smaller nuclei. The latter were characteristically confined to the center of the cells and did not extend out to the tips of the filaments.

Cell Nucleus↗
PubMed1966

Ultrastructure of Lampropedia hyalina.

Pangborn, Jack (University of California, Davis), and Mortimer P. Starr. Ultrastructure of Lampropedia hyalina. J. Bacteriol. 91:2025-2030. 1966.-In an effort to learn more about the structural bases for the sheeting format of Lampropedia hyalina, ultrathin sections were cut which were precisely oriented either parallel to or perpendicular to the plane of growth; these were examined by electron microscopy. Lampropedia cells show cytological features typical of gram-negative bacteria. In addition, three uniquely structured layers are found exterior to the cell walls. Details are presented regarding the fine structures and geometric relationships of these layers; their probable origins and involvements in the characteristic cellular juxtaposition are discussed.

Ascomycota↗
PubMed1965

Studies on the release of lysosomal enzymes from kidney lysosomes.

Incubation of kidney lysosomes at 37 degrees results in a graded release of lysosomal enzymes. The release of enzyme occurs in two stages. First the enzymes become available to the substrate but remain sedimentable. Later the amount of soluble enzyme increases and eventually is almost equal to that of the available enzyme. Morphological studies of lysosomes showed that during the process involving increasing availability of enzymes, the lysosomes remained intact. Release of the soluble enzymes was characterized ultrastructurally by a complete loss of the electron-opaque matrix contained within the lysosomal membrane. The increased release of soluble enzymes was concomitant with an increase in the number of individual lysosomes showing complete loss of contents, rather than a gradual loss or dilution of matrix density. Lysosomes which had lost their electron-opaque contents retained their outer membrane intact and were seen to contain numerous internal membranes and small vesicles.

Acid Phosphatase↗
PubMed1962

LOCALIZATION OF RESPIRATORY ENZYMES IN INTRACYTOPLASMIC MEMBRANES OF AZOTOBACTER AGILIS.

Pangborn, J. (University of California, Davis), Allen G. Marr, and S. A. Robrish. Localization of respiratory enzymes in intracytoplasmic membranes of Azotobacter agilis. J. Bacteriol. 84:669-678. 1962.-Thin sections of the cells of Azotobacter agilis which have been disrupted by sonic treatment, by osmotic shock, or by ballistic disintegration reveal a network of internal membranes in the form of vesicles and tubules. The internal membranes are attached to the envelope. Treatment in a Mickle disintegrator of envelopes emptied of cytoplasm by osmotic shock results in the loss of the internal membranes and a concomitant release of reduced diphosphopyridine nucleotide oxidase from the envelopes. Thus, the intracytoplasmic membranes are the probable locus of the respiratory enzymes of the cell. Thin sections of whole cells show tubular intracytoplasmic membranes which are obscured by ribosomes and other dense cytoplasmic constituents.

Journal Article↗