Search PubMed⌕ Search

Biomedical subjects

M Monk

Publications and source records attributed to M Monk.

At least 91 records · Page 5Linked to original sources
PubMed1978

Problems in suicide statistics for whites and blacks.

The accuracy of suicide statistics was assessed by comparing published Health Department suicide rates for an area of New York City with Medical Examiner records. For the period 1968--1979, records from the Medical Examiner's Office were searched to determine all deaths classified as definite suicides. Another group of deaths was considered suicide by the Medical Examiner but never classified as such. These deaths we labeled "assigned suicides." When definite suicides were compared with all deaths considered suicide by the Medical Examiner (definite and assigned suicides), black suicide was underestimated by 80 per cent and white suicide by 42 per cent. Underestimation was the same for males and females but varied by age group. In 1968, when the seventh revision of the International Classification of Deaths (ICD) was used, Health Department suicide rates for blacks were almost identical to Medical Examiner rates, while white rates were underestimated by 25 per cent. In 1969--1970, when the eighth revision was used, Health Department statistics underestimated black suicides by 82 per cent and white suicides by 66 per cent. Reasons for the underestimations were related to the methods used in committing suicide by the two ethnic groups and to the ways that suicide classification has changed from the seventh to eighth revision. Implications for research using official death certificate reports are discussed.

Adolescent↗
PubMed1978

X-chromosome activity in preimplantation mouse embryos from XX and XO mothers.

Embryos from XO female mice begin development with half the activity levels of an enzyme (HPRT) coded for by a gene on the X chromosome, compared with embryos from XX females. Groups of unfertilized eggs and individual embryos at the 8-cell, morula and blastocyst stages were assayed for HPRT activity. An autosomally coded enzyme (APRT) was assayed simultaneously in the same reaction mix as a control. There is a substantial increase in HPRT activity by the 8-cell stage. However, the mean activity of HPRT in embryos of XO mothers remains half that in embryos of XX mothers. This suggests a significant maternally inherited component of HPRT activity in 8-cell embryos. By the 9- to 16-cell morula stage the HPRT activities in the two groups of embryos become similar due, presumably, to a transition to embryo-coded activity; HPRT activities in individual morulae from XX mothers show a bimodal distribution consistent with the hypothesis that both X-chromosomes are active in XX embryos at this stage.

Adenine Phosphoribosyltransferase↗
PubMed1976

Patterns of lactic dehydrogenase isozymes in mouse embryos over the implantation period in vivo and in vitro.

Following blastocyst implantation, or outgrowth in vitro, the LDH isozyme pattern changes from that of the maternally inherited B subunit isozyme form (LDH-1) to a pattern dominated by A subunits (Auerbach & Brinster, 1967, 1968). In preimplantation embryos we have observed additional isozyme bands, as yet unidentified. An analysis of the pattern of newly synthesized LDH isozymes and specific activity of LDH in different regions of early postimplantation embryos suggests that there is a sequantial activation of A and B subunits, and that activity first appears in ICM- (inner cell mass) derived tissues and then in trophoblast-derived tissues. In vitro, in the absence of ICM cells, the transition of LDH-isozyme pattern does not occur in outgrowing trophoblast giant cells. This suggests a possible inductive interaction between ICM and trophoblast.

Animals↗
PubMed1975

The kinetics of derepression of prophage lambda following ultraviolet irradiation of lysogenic cells.

Double lysogens for prophages lambda cI+ and lambda cI ind-ts-857 are induced only by the combined effects of ultraviolet (UV) irradiation and high temperature, not by either treatment alone (Sussman and Jacob, 1962). We have followed the kinetics of inactivation of the cI+ repressor brought about by irradiation in asynchronously and synchronously growing cultures of B/r (lambda cI ind- ts-857). Assays of the yield of phage released as a result of temporary thermal inactivation of the UV-resistant ind- ts-857 repressor at intervals after the irradiation accurately reflect the time course of UV-induced inactivation of the cI+ repressor. The results show that UV-induced derepression takes place in all cells of the population approximately 20 min after the irradiation whether the cells were growing asynchronously or synchronously. Hence UV induction of prophage lambda is not triggered at a particular stage in the cell cycle.

Cell Count↗
PubMed1973

Deoxyribonucleic acid synthesis in recA and recB derivatives of an Escherichia coli K-12 strain with a temperature-sensitive deoxyribonucleic acid polymerase I.

recA and recB derivatives of a strain of Escherichia coli with a temperature-sensitive deoxyribonucleic acid (DNA) polymerase I (polA12) are inviable at high temperature, but continue to incorporate (3)H-thymine into DNA for extended periods. The DNA made in pulse-chase experiments at high temperature in the polA12 parent and its double-mutant derivatives has been examined by alkaline sucrose gradient sedimentation analysis. The low-molecular-weight DNA fragments made during short pulses were joined at the same rate in each strain. Furthermore, the resulting high-molecular-weight DNA was of the same size in each case and was stable for at least 50 min. It is concluded that the inviability of the double mutants is due neither to a defect in converting low-molecular-weight DNA intermediates to high molecular weight nor to the presence of unrepaired random breaks in their DNA.

Carbon Isotopes↗
PubMed1972

Conditional lethality of recA and recB derivatives of a strain of Escherichia coli K-12 with a temperature-sensitive deoxyribonucleic acid polymerase I.

We have isolated a strain of Escherichia coli K-12 carrying a mutation, polA12, that results in the synthesis of a temperature-sensitive deoxyribonucleic acid (DNA) polymerase I. The double mutants polA12 recA56 and polA12 recB21, constructed at 30 C, are inviable at 42 C. About 90% of the cells of both double mutants die after 2 hr of incubation at 42 C. Both double mutants filament at 42 C and show a dependence on high cell density for growth at 30 C. In polA12 recB21 cells at 42 C, DNA and protein synthesis gradually stop in parallel. In polA12 recA56 cells, DNA synthesis continues for at least 1 hr at 42 C, and there is extensive DNA degradation. The results suggest that the primary lesion in these double mutants is not in DNA replication per se.

Alkanes↗