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Biomedical subjects

D J Cummings

Publications and source records attributed to D J Cummings.

97 records · Page 6Linked to original sources
PubMed1967

Induced structural defects in T-even bacteriophage.

Multiple aberrant substructures of T-even bacteriophage particles occurred when amino acid analogues or antimetabolites were present during phage growth. Certain aberrant substructures were induced by specific analogues or antimetabolites. In particular, it was observed by electron microscopy that l-canavanine, an arginine analogue, gave rise to polyheads; l-azetidine-2-carboxylic acid, a proline analogue, gave rise to polytail tubes; and 1,2,4-trizaole-3-alanine, a histidine analogue, proflavine, and actinomycin D all gave rise to small heads. These aberrant substructures were similar to those reported earlier with conditional lethal mutants (amber) of T4D in a restrictive host.

Acridines↗
PubMedDate not supplied

Morphological changes in aging cell lines of Paramecium aurella. I. Alterations in the cytoplasm.

Electron microscopical examination of aging P. aurelia revealed that definitive changes occur in the cytoplasm of old cells. There was an increase in the number of mitochondria and lysosomal bodies as well as the appearance of large dense bodies and autophagous vacuoles. The mitochondria were altered morphologically and many appeared to be coalesced with lysosome-like bodies and were also observed to be degenerating within autophagous vacuoles. The large dense bodies were considered to be similar to the lipofuscin or age pigments reported in other aging cells. The relationship of the large dense bodies to the lipofuscin pigments and their probable origin are discussed as is the involvement of the cytoplasm in the aging death process in P. aurelia.

Aging↗
PubMedDate not supplied

Morphological changes in aging cell lines of Paramecium aurelia. II. Macronuclear alterations.

Electron microscopic examination of aging P. aurelia showed that the macronucleus undergoes characteristic structural changes. The surface of the aging macronucleus was highly invaginated. Compared with young macronuclei, the chromatin bodies appeared to be smaller and condensed, and were fewer per unit area of the aging macronucleus. The nucleolar bodies also showed morphological alterations. In many aging macronuclei the nucleolar bodies appeared to be aggregated. Large ring-shaped or coiled loops of nucleoli were also observed. These changes in the ultrastructure of macronucleus in the aging paramecia suggest that the macronucleus in the aging cells is less active in the synthesis of macromolecules and transport of material to the cytoplasm.

Animals↗
PubMedDate not supplied

Morphological changes in aging cell lines of Paramecium aurelia. III. The effects of emetine on polysome formation.

The effect of emetine, an inhibitor of cellular protein synthesis, on young and old cell lines of Paramecium aurelia was studied. Emetine treatment resulted in the accumulation of ribosomal aggregates in the form of helices or rosettes. In treated young cells, large patches of endoplasmic reticulum with clusters of ribosomes were frequently observed. These structures were smaller in treated aging cells. Owing to the association of these ribosomal clusters with endoplasmic structures, they were called "ribosomal complexes". In young cells the polysome helices were more numerous, compared to those of old cells. The difference in the number of polysomes between the young and old cells appeared to be related to the number of ribosomes. The results suggested that in aging cells there were fewer ribosomes and less RNA. In very old cells the ribosomal particles appeared to be altered morphologically.

Animals↗