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Biomedical subjects

E M Walker

Publications and source records attributed to E M Walker.

At least 91 records · Page 5Linked to original sources
PubMed1976

Antileukemic properties of organoplatinum complexes.

The antitumor activity of 46 cis-amineplatinum congeners was evaluated against L1210 leukemia in (C57BL/L X DBA/2)F1 mice. Several compounds in this series significantly prolonged the life-spans of mice with the leukemia. During the selection of the compound that yielded optimal activity [dichloro(1,2-diaminocyclohexane)platinum], the chlorides were substituted with various organic and inorganic anions. The aqueous solubility was greatly increased with retention of significant antileukemic activity. Most of the active compounds were synergistic with cyclophosphamide, and cure rates up to 80% were obtained with certain combinations.

Animals↗
PubMed1976

Combination chemotherapy of L1210 leukemia with platinum compounds and cyclophosphamide plus other selected antineoplastic agents.

Six antitumor platinum compounds were used in combination with cyclophosphamide plut 1 of 7 other antitumor drugs for treatment of L1210 leukemia in B6D2F [C57BL/6 X DMA/2) F] mice. Data obtained from each three-agent regimen were compared with those obtained after administration of each compound alone and each appropriate two-agent combination. No cure (greater than 60-day survival) was obtained with any compound used alone. Combination of cyclophosphamide with a platinum compound (Pt+CY) yielded a collective cure rate of 193/420, and the addition of a third cure rate to 290/420 (P less than 0.001). Certain regimens produced 100% cure rates. The most effective drugs when used in combination with PT+CY were cytosine arabinoside, 5-fluorouracil, hydroxyurea, and Yoshi-864. Adriamycin, methotrexate, and vincristine were less effective at the doses used. Toxicity, as evidenced by maximum weight loss, was slightly greater with the three-agent combinations than with the Pt+CY regimens.

Animals↗
PubMed1972

Conjugation in Escherichia coli: failure to confirm the transfer of part of sex factor at the leading end of the donor chromosome.

Experiments were carried out attempting to determine whether part of sex factor is transferred at the leading end of the Hfr chromosome during conjugation. In the first experiment, an analysis was made of the donor properties of recombinant strains which had inherited the terminal but not the proximal marker from an Hfr. Secondly, recombinants integrating an extremely proximal marker from an Hfr were examined for the inheritance of a sex factor affinity locus adjacent to this marker. In the third experiment, proximal transfer of the wild-type allele of a temperature-sensitive sex factor mutation was looked for, using as recipient a temperature-sensitive Hfr strain, and as donor a wild-type Hfr isogenic with respect to the site of sex factor integration. In none of these experiments could the presence of sex factor material at the leading end be demonstrated. The results do not rule out the possibility that part of F is transferred proximally but only integrated at a very low frequency. They do, however, conflict with certain findings of other authors which, in the past, have been taken as evidence for the transfer of part of F at the leading end.

Alleles↗
PubMed1970

Conjugation in Escherichia coli: interactions affecting recombination frequencies for markers situated at the leading end of the donor chromosome.

Experiments have been performed to test the validity of a model which relates low recovery of very early donor markers in recombinants to the presence of sex-factor deoxyribonucleic acid at the leading end of donor deoxyribonucleic acid transferred by conjugation. This model has been found to be incorrect. The results obtained do not rule out the possibility that a piece of sex factor is transferred at the leading end, but indicate, however, that if this occurs it is not the cause of the low recovery of a very early donor marker.

Chromosome Mapping↗
PubMed1969

Temperature-sensitive conjugation-defective F factor in Escherichia coli.

A mutant strain of Escherichia coli K-12 which is unable to transfer genetic material at 42 C has been isolated. Although transfer is inhibited at this temperature, the formation of specific pairs is unaffected. This strain and its derivatives also show an altered sensitivity to certain ribonucleic acid-containing male specific phages at 42 C. Both phenotypic changes are reversed when a derepressed fi(+) R factor is present in the same cell and a revertant which has regained both activities has been obtained. The nature of the temperature-sensitive defect and its effect on the conjugation process are discussed.

Chromosome Mapping↗
PubMed1967

Conjugation in Escherichia coli: recombination events in terminal regions of transferred deoxyribonucleic acid.

An investigation of recombination events occurring in zygotes formed during conjugation has been carried out. The frequencies with which donor markers situated close to the origin are recovered indicates an obligatory interaction between the recipient chromosome and a region on the donor chromosome adjacent to the leading end. The partial exclusion from recombinants of some of the most proximal markers studied, however, indicates that this interaction does not occur at the free extremity of the transferred deoxyribonucleic acid. Alternate models to explain these facts are presented.

Chromosome Mapping↗