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Biomedical subjects

M D Cave

Publications and source records attributed to M D Cave.

86 records · Page 5Linked to original sources
PubMed1972

Localization of ribosomal DNA within oocytes of the house cricket, Acheta domesticus (Orthoptera: Gryllidae).

A large DNA-containing body is present in addition to the chromosomes in oocytes of the house cricket Acheta domesticus. Large masses of nucleolar material accumulate at the periphery of the DNA body during the diplotene stage of meiotic prophase I. RNA-DNA hybridization analysis demonstrates that the genes which code for 18S and 28S ribosomal RNA are amplified in the ovary. In situ hybridization indicates that the amplified genes are localized within the DNA body of early prophase cells. As the cells proceed through diplotene the DNA which hybridizes with ribosomal RNA is gradually incorporated into the developing nucleolar mass.

Animals↗
PubMed1966

Incorporation of tritium-labeled thymidine and lysine into chromosomes of cultured human leukocytes.

The incorporation of thymidine-H(3) and lysine-H(3) into human leukocyte chromosomes was studied in order to determine the temporal relationships between the syntheses of chromosomal deoxyribonucleic acid and chromosomal protein. The labeled compounds were incorporated into nuclei of interphase cells. Label from both precursors became apparent over the chromosomes of dividing cells. Incorporation of thymidine-H(3) occurred during a restricted period of midinterphase (S) which was preceded by a nonsynthetic period (G(1)) and followed by a nonsynthetic period (G(2)). Incorporation of lysine-H(3) into chromosomal protein occurred throughout interphase. Grain counts made over chromosomes of dividing cells revealed that the rate of incorporation of lysine-H(3) into chromosomal protein differed during various periods of interphase. The rate of incorporation was diminished during G(1). During early S period the rate of incorporation increased, reaching a peak in late S. The high rate continued into G(2). Thymidine-H(3) incorporated into DNA was distributed to mitotic chromosomes of daughter cells in a manner which has been referred to as a "semi-conservative segregation." No such semi-conservative mechanism was found to affect the distribution of lysine-H(3) to the mitotic chromosomes of daughter cells. Therefore, it is concluded that synthesis of chromosomal protein and its distribution to chromosomes of daughter cells are not directly influenced by synthesis and distribution of the chromosomal DNA with which the protein is associated.

Autoradiography↗
PubMedDate not supplied

Characterization of plasmids from strains of Mycobacterium avium-intracellulare.

Strains of Mycobacterium avium-intracellulare were examined for the presence of plasmids. Actively growing cultures were treated with cycloserine and ampicillin to sensitize the cells to lysis by detergent, and cleared lysates were prepared by treatment with sodium dodecyl sulfate and NaCl. Purified plasmid DNA was prepared by equilibrium density centrifugation in CsCl gradients containing ethidium bromide and analyzed by agarose gel electrophoresis. Strain LR25 was found to carry three plasmids, including a large plasmid with a molecular weight of greater than 10(8). Examination of the DNA by electron microscopy confirmed that the bands seen in the agarose gels represented circular DNA molecules. The presence of plasmids was demonstrated in four additional strains. Three plasmids were carried in a strain of serovar 2, and single plasmids were detected in strains of serovars 4, 12, and 18. Plasmids were not detected in three strains of serovars 1, 3, and 5.

DNA, Bacterial↗
PubMedDate not supplied

Transmission of tuberculosis among the urban homeless.

OBJECTIVE: To determine the relative frequencies of primary and reactivation tuberculosis in the urban homeless. DESIGN: Prospective evaluation of homeless tuberculosis patients. SETTING: Central Los Angeles, Calif. PATIENTS: Thirty-four homeless patients with culture-proven tuberculosis. INTERVENTIONS: IS6110-based restriction fragment length polymorphism (RFLP) analysis was performed on Mycobacterium tuberculosis isolates. If results were inconclusive, pTBN12-based RFLP analysis was performed. MAIN OUTCOME MEASURE: Clustering of M tuberculosis isolates. A cluster consisted of two or more isolates with indistinguishable RFLP patterns. RESULTS: Twenty-four of 34 homeless patients had clustered isolates in six clusters. CONCLUSIONS: The minimum percentage of cases due to primary tuberculosis in the homeless was estimated to be 53%, compared with the traditional estimate of 10% in the general population. The results suggest that primary tuberculosis caused the majority of tuberculosis cases in this population of the urban homeless in central Los Angeles.

Adult↗