PubMed Health⌕ Search

Biomedical subjects

G B CHAPMAN

Publications and source records attributed to G B CHAPMAN.

At least 19 recordsLinked to original sources
PubMed1963

CYTOLOGICAL ASPECTS OF ANTIMICROBIAL ANTIBIOSIS. III. CYTOLOGICALLY DISTINGUISHABLE STAGES IN ANTIBIOTIC ACTION OF COLISTIN SULFATE ON ESCHERICHIA COLI.

Kaye, Jeremy J. (Cornell University Medical College, New York, N.Y.) and George B. Chapman. Cytological aspects of antimicrobial antibiosis. III. Cytologically distinguishable stages in antibiotic action of colistin sulfate on Escherichia coli. J. Bacteriol. 86:536-543. 1963.-Broth cultures of Escherichia coli were subjected to a constant concentration of colistin sulfate for varying periods of time. Controls and treated cells were fixed, dehydrated, and embedded in methacrylate, and ultrathin sections were examined in an electron microscope. Three stages in the antibiotic process were discerned. Stage 1 was characterized by a disruption of the axial orientation of the nuclear material and by an invasion of nuclear areas by tufts of material presumably of cytoplasmic origin; no loss of cellular contents could be detected cytologically. Stage 2 was characterized by the loss of nuclear material and by a loss of typical cytoplasmic granularity, an increase in cytoplasmic electron density, and an agglomeration of the cytoplasm into packed tufts of material; in contrast to the nuclear material, there was no loss of cytoplasmic material in this stage. Stage 3 was characterized by the loss of the altered cytoplasmic material but with the persistence of mesosomes, plasma membrane, and cell wall. Speculation that each and all of these changes might have resulted from an altered intracellular milieu secondary to a primary effect of the antibiotic on the plasma membrane is presented.

Anti-Bacterial Agents↗
PubMed1962

Cytological aspects of antimicrobial antibiosis. II. Cytological changes associated with the exposure of Pseudomonas aeruginosa and Bacillus megaterium to colistin sulfate.

Chapman, George B. (Cornell University Medical College, New York, N.Y.). Cytological aspects of antimicrobial antibiosis. II. Cytological changes associated with the exposure of Pseudomonas aeruginosa and Bacillus megaterium to colistin sulfate. J. Bacteriol. 84:180-185. 1962-Broth cultures of Pseudomonas aeruginosa and Bacillus megaterium were exposed to the antibiotic colistin sulfate. Control (unexposed) and exposed cells were fixed, dehydrated, and embedded in methacrylate. Ultrathin sections were examined in an RCA EMU2-D electron microscope. Two conspicuous cytological changes were noted in P. aeruginosa. The nuclear material was no longer demonstrable in its normal sites, leaving an empty space, and the cytoplasm lost its granularity, becoming homogeneous. In B. megaterium, the latter change was also noted. The nuclear material, however, although no longer demonstrable, did not leave an empty space. Rather, it seemed that cytoplasmic material had engulfed and masked nuclear areas. Cells which showed these changes were nonviable.

Anti-Bacterial Agents↗
PubMed1961

Fine structure of the larval anuran epidermis, with special reference to the figures of Eberth.

Small pieces of skin from 8 cm long Rana clamitans larvae were fixed in OsO(4), washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU 2D. The sections showed that aggregates of fibrous material in the cells of the inner layer of epidermal cells are identical in disposition and size with the classical figures of Eberth. It is conclusively shown that these figures do not arise from an aggregation of mitochondrial filaments. The tendency of the fibrils to concentrate on attachment points, or thickenings of the basal plasma membrane, is noted. It is also observed that numerous mitochondria are located in the distal region of the cells of the outer layer of epidermis in association with the secretory vacuoles. Microvilli are seen occasionally on the free surface of the skin. Cisternae are found only in the cells of the outer epidermal layer, while vesicular endoplasmic reticulum is found in the cells of both epidermal layers.

Animals↗
PubMed1959

Cytological studies of the nematocysts of Hydra. I. Desmonemes, isorhizas, cnidocils, and supporting structures.

Entire hydras or tentacles were fixed in OsO(4) or in KMnO(4) and thereafter washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on an experimental model, thermal expansion type ultramicrotome or on a Porter-Blume microtome. The sections were examined in an RCA electron microscope. Type EMU-2 D. "Squash preparations" for light microscopy, were made from the hydra mouth region and the attached tentacles. These were observed with an AO Baker interference microscope. In the mature organism, three of the four types of nematocysts normally found in hydra could be positively identified with the electron microscope. The desmonemes, the smallest type, have a dense matrix and a thin capsule. The two different types of mature isorhizas could not be distinguished with certainty. They are intermediate in size between the desmonemes and stenoteles and have a capsule with a dense matrix. The cnidocil, or triggering hair, which is composed of a dense core and a fibrillar sheath has nine supporting elements arranged in a semi-circle near its base. Twenty "supporting structures" are arranged around the nematocyst capsule and interconnections between the supporting elements and these latter structures have been observed. Development of the nematocysts involves an increase in density of the matrix. Spines can be seen in the interior of tubular structures within the capsules of the holotrichous isorhizas.

Animals↗