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Biomedical subjects

I M Jones

Publications and source records attributed to I M Jones.

99 records · Page 6Linked to original sources
PubMed1982

An in vivo sister-chromatid exchange assay in the larvae of the mussel Mytilus edulis: response to 3 mutagens.

An in vivo sister-chromatid exchange (SCE) assay using the larvae of the mussel Mytilus edulis was developed. Larvae were exposed to mutagens beginning 12 h after fertilization and harvested 12 h later in the late trochophore stage. Dose responses to the mutagens bromodeoxyuridine, mitomycin C and methyl methanesulfonate were linear. The sensitivity of the SCE response of mussel larvae to these mutagens compares favorably with that of other systems and indicates this assay to be valuable in marine genetic toxicological monitoring.

Animals↗
PubMed1982

Release of [3H]noradrenaline from descending tracts in the cat spinal cord in vivo.

The release of [3H]noradrenaline into the perfused central canal of the cat lumbar-sacral spinal cord was monitored in vivo. Stimulation of descending tracts produced an increase efflux into artificial cerebrospinal fluid containing 10(-6) M phenoxybenzamine which could be dissociated from any concurrent rise in blood pressure. No release was produced by stimulating dorsal roots over the length of cord perfused. It appears, therefore, that noradrenaline can be released from descending nerve terminals, but not from dorsal root afferents in the spinal cord.

Afferent Pathways↗
PubMed1981

Effect of growth rate and nutrient limitation on the transformability of Escherichia coli with plasmid deoxyribonucleic acid.

The observed transformation frequency by plasmid deoxyribonucleic acid of Escherichia coli grown in continuous culture was found to depend on both the steady-state growth rate and the type of nutrient used to limit growth. With carbon, nitrogen, or phosphorus limitation, the faster the growth rate, the higher the transformation frequency. The increase in transformation frequency associated with higher rates was shown to be due to more transformable cells in the population rather than an increased efficiency of deoxyribonucleic acid uptake. Growth rate had relatively little effect on the transformability of cells from sulfate- and Mg2+-limited chemostats, indicating that some factor other than the growth rate must influence the frequency of transformation. Regardless of the nutrient limitation or the growth rate, no transformants were obtained in the absence of CaCl2.

Calcium Chloride↗
PubMed1981

Study of two cases of ring 13 chromosome using high-resolution banding.

The chromosomes of two patients with ring 13 (r13) were studied using high-resolution RBG banding of prometaphase cells. The rings of the two patients differ slightly in breakpoints. Cell with multiple single, double-sized rings, quadruple-sized rings, rod- and ring-shaped fragments, and fragments showing varied states of condensation were seen, as were cells monosomic for chromosome 13. The evolution of these cell lines as a result of sister chromatid exchange, nondisjunction, ring breakage, and premature chromosome condensation is discussed. Clinical features of these patients reflect the heterogeneity of phenotype for r13 patients. Each case includes a feature of trisomy 13. The significance of mosaicism of cell lines in patients bearing ring chromosomes is considered with respect to variation in clinical findings.

Abnormalities, Multiple↗
PubMed1980

Maintenance of some ColE1-type plasmids in chemostat culture.

When cells carrying the plasmids RP1, pDS4101 (a ColK derivative) or pDS1109 (a ColE1 derivative) were maintained in chemostat culture in the absence of antibiotic selection, plasmid-free segregants were not detected after 120 generations of nutrient-limited growth. By contrast, plasmid-free segregants of pMB9- and pBR322-containing cells arose after approximately 30 generations, irrespective of the host genetic background. However, even though pDS1109 was maintained its copy-number fell five-fold during 80 generations of limited growth. It is suggested that loss of pBR322 occurs following a similar copy-number decrease which results in defective segregation of the plasmid to daughter host cells. This defective segregation was not complemented in trans by either RP1 or pDS4101.

Cell Division↗
PubMedDate not supplied

Factors affecting HPRT mutant frequency in T-lymphocytes of smokers and nonsmokers.

The frequency of thioguanine-resistant, hypoxanthine phosphoribosyltransferase-deficient lymphocytes in the peripheral blood of human subjects was used to study the genotoxic effects of smoking. Sixty-two nonsmokers and 58 smokers, aged 19 to 45 years with average ages of 30 and 32 years, respectively, and with no other known exposures, were studied using an in vitro assay of the frequency of mutant lymphocyte clones. Analysis of variance explained 68% of the variation in the mutant frequencies. Mutant frequency was dependent upon lymphocyte cloning efficiency, length of smoking history, age, and interactions between these variables. Four nonsmokers and three smokers had high mutant frequencies that were not explained by these variables. Mutant frequencies were inversely related to lymphocyte cloning efficiencies; the effect was twice as great for smokers as for nonsmokers. The time-dependent effect of smoking dominated, with mutant frequency increasing 10%/year of smoking as compared with an independent 1%/year of age. Smoking had a greater effect on young smokers' lymphocytes. Heterogeneity of mutant frequency among both smokers and nonsmokers and its implications for use of lymphocyte mutation assays as biomarkers are discussed.

Adult↗