Biomedical subjects

L C Sowden

Publications and source records attributed to L C Sowden.

6 recordsLinked to original sources

PubMed1979

The ultrastructure of the major species of an enriched methanogenic culture utilizing acetic acid.

The ultrastructure of the cells of the major component of an enriched culture of a presumed methanogen which utilized acetic acid was studied by transmission and scanning electron microscopy. The filaments were composed of Gram-positive, rod-shaped cells, 1--2 micrometer in length and about 0.5 micrometer in breadth, attached end to end. Septa between cells were complex, with a central, electron-dense sheet which had a spherical enlargement in the center separating the cell walls. The cells walls themselves were of variable thickness with a light, fluffy, thin portion on the outside and a denser, thicker portion within. They contain a series of rings stacked side by side which are composed of material that stains strongly and positively with phosphotungstate ion. The cytoplasmic membrane of these cells had an outer leaflet which stains more densely with uranium and lead ions than the inner leaflet. There were no recognizable organelles in the cytoplasm other than ribosomes. It is shown in these observations that the presumed methanogen may likely be a new species.

Acetates↗

PubMed1979

Additional properties of a soluble polymer of glucose from cultures of Acetobacter xylinum.

The results of differential, thermal analysis of a soluble, beta (1 leads to 2)-branched, beta (1 leads to 4)-D-glucan isolated from cultures of Acetobacter xylinum are consistent with previous conclusions about its structure. The O-acetyl content of the polymer is 8.3% which corresponds to a maximum substitution of one acetyl group per three glucose residues. Proton nuclear magnetic resonance spectra confirm that all the glycosidic bonds are beta linkages. Some preparations of the polymer are contaminated by another polymer containing mannose and rhamnose. No evidence was obtained to support a previous suggestion that the branched D-glucan is a precursor of bacterial cellulose and this suggestion is now withdrawn.

Glucans↗

PubMed1978

Morphology microstructure, and development of colonies of Acetobacter xylinum.

Development of the morphology and microstructure of colonies of Acetobacter xylinum growing on agar was studied by optical microscopy, and transmission and scanning electron microscopy. The mass of rapidly dividing cells surrounded by a sheath of cellulose microfibrils passes from a smooth spheroid to a flattened aggregate with a characteristic "pillowed" surface. This morphology is the result of a repeated extrusion of cells from the confirming sheath, followed by regeneration of a new portion of the sheath on the extrusion of cells from the confirming sheath, followed by regeneration of a new portion of the sheath on the extruded cell mass. Relations of this mechanism to others which produce similar shapes are indicated.

Agar↗

PubMed1977

The structure of cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus.

The structure of the pellicles and cells of the cellulose-producing bacteria, Acetobacter xylinum and Acetobacter acetigenus, was studied by transmission electron microscopy of thin sections and freeze-etch replicas of glucose-stimulated cell suspensions, quiescent cell suspensions, and discrete pellicles. These bacteria have a relatively thin cell wall in section, with several irregular features superimposed on an otherwise simple, Gram-negative morphology. There are no flagella or pili. Unfixed, unextracted cells, viewed as whole mounts, show spherical or ellipsoidal bodies of undetermined composition which disappear after extraction with water or ethanol and propylene oxide. For both species, there are several kinds of cell surface irregularities, some of which are localized protrusions of the cell envelope. A variety of irregularities is seen frequently on cells in the first minutes of glucose incubation, on cells in a discrete pellicle, on quiescent cells, and on starved cells. Immediately after the addition of glucose to cellulose-free cells in suspension culture, fine fibrils appear on and (or) near the cell envelope. The fine fibrils are frequently as small as 3 nm in diameter in both freeze-etch and thin-section preparations and are frequently associated with freshly synthesized cellulose fibrils. Starved cells in suspensions free of (classical) microfibrils sometimes reveal stubs of an extracellular structure whose morphology resembles that of a nascent cellulose fibril.

Cell Membrane↗

PubMed1977

Purification and properties of a soluble polymer of glucose from cultures of Acetobacter xylinum.

A soluble nondialyzable polymer of glucose was isolated and purified by selective ethanol and ammonium sulfate precipitation from the supernatant of a culture of Acetobacter xylinum which was actively producing cellulose. This polymer was heterogeneous in size with an average sedimentation constant S20,w, of the most abundant fraction of 11.1. On drying from dilute solution in water, the polymer(s) showed extended linear fibrils or aggregates of such fibrils by transmission electron microscopy. The infrared spectrum resembled closely that of cellulose II. Preparations of the lyophilized polymer were amorphous by X-ray diffraction. Composition and structure of the polymer were established by enzymatic digestion, acid hydrolysis before paper chromatography, and methylation followed by gas-liquid chromatography. Glucose was the only component of the polymer. There were few, if any, alpha 1 leads to 4 linkages between glucose residues. The polymer(s) is a linear chain of glucose units linked beta 1 leads to 4 with single glucose residues as branches at position 2 of every third glucose on the average. The possibility that this branched glucose polymer is an intermediate in cellulose biosynthesis is examined.

Chemical Phenomena↗

PubMed1975

Variability of the iron, copper and mercury contents of individual red blood cells.

The relative iron, copper and mercury contents of individual, isolated erythrocytes from eight people were determined by analytical electron microscopy. The variation in iron content between erythrocytes of the same sample is more than six times, for copper content more than tem times and for mercury more than five times. Similar variations were observed for 1-day-old chick defintive erythrocytes and for 4-day-old chick embryo primitive erythrocytes. The range of variation does not depend greatly, it at all, on the age of the erythroyctes or the tissue of origin. There is little or no correlation between the variation of iron contnet and that of copper. The cause of the wide variation of metallic ion contnt among erythroyctes is not yet known.

Adult↗