Biomedical subjects
Publications and source records attributed to R B Thompson.
Five of 75 patients with chronic granulocytic leukaemia seen over a 25 year period had papilloedema at presentation. These patients had unusually high leucocyte counts and the papilloedema may be a manifestation of leucostasis. The fundal abnormalities resolved in all five patients--in four after conventional treatment with busulphan only.
Seventeen adult patients with previously untreated acute lymphoblastic leukaemia (ALL) were entered into a schedule of chemotherapy in which 3 combinations, each of 4 drugs, were administered in a predetermined cyclical rotation in combination with cranial irradiation and intrathecal injections of methotrexate. Of the 17 patients, 16 completed induction therapy and 15 (94%) entered remission. The only patient with T-ALL died before receiving any therapy. The median survival for all patients (17) was 22 months. Meningeal leukaemia did not occur during the haematological remission phase although 3 patients developed this complication following relapse. The authors conclude that the addition of cyclophosphamide and cytosine arabinoside to vincristine/prednisone provides excellent remission induction but the aggressive maintenance schedule employed has not led to significant long-term survival.
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Bacteriophage T5 induces a deoxyuridine 5'-triphosphate nucleotidohydrolase (dUTPase) activity during infection of Escherichia coli. A T5 mutant (T5 dut) unable to induce this dUTPase activity has been isolated. Although this mutant is viable, the E. coli dUTPase activity is not sufficiently active to exclude uracil from the progeny DNA and about 3% of the thymine is replaced by uracil. When the mutant is grown in an E. coli dut host about 12% of the thymine in the progeny DNA is replaced by uracil. T5 phage containing 12% uracil can replicate in uracil-DNA glycosylase-deficient (ung) hosts with high efficiency, but fail to replicate in ung+ hosts. The amount of thymine replaced by uracil in the progeny produced in dut hosts is nearly independent of the ung genotype, indicating that the host uracil-DNA glycosylase-dependent repair pathway is not operating efficiently to remove uracil from T5 progeny DNA.
The amino acid sequences of chymotryptic and tryptic peptides of Hippopotamus amphibius cytochrome c were determined by a recent modification of the manual Edman sequential degradation procedure. They were ordered by comparison with the structure of the hog protein. The hippopotamus protein differs in three positions: serine, alanine, and glutamine replace alanine, glutamic acid, and lysine in positions 43, 92, and 100, respectively. Since the artiodactyl suborders diverged in the mid-Eocene some 50 million years ago, the fact that representatives of some of them show no differences in their cytochromes c (cow, sheep, and hog), while another exhibits as many as three such differences, verifies that even in relatively closely related lines of descent the rate at which cytochrome c changes in the course of evolution is not constant. Furthermore, 10.6% of the hippopotamus cytochrome c preparation was shown to contain isoleucine instead of valine at position 3, indicating that one of the four animals from which the protein was obtained was heterozygous in the cytochrome c gene. Such heterogeneity is a necessary condition of evolutionary variation and has not been previously observed in the cytochrome c of a wild mammalian population.
Three-dimensional finite models for the monkey, baboon, and human brains have been developed and are described. Isoparametric brick elements and membrane elements represent the soft tissue and partitioning internal folds of dura, respectively. By specifying the finite element mesh on the skull inner surface, the irregular shape of the brain is generated. Each model is subjected to the same skull acceleration to investigate response relationships between species. Important dynamic response differences are revealed by comparing the computed intracranial pressures. Experimentally derived head injury data are correlated with model dynamic responses. Using the baboon and monkey models, brain injury tests are simulated and model response measures are compared to produced injury. Using the human model, computed stresses are compared to intracranial pressures measured in cadaver impact tests.
A bacteriophage T5 mutant has been isolated that is completely deficient in the induction of deoxynucleoside 5'-monophosphatase activity during infection of Escherichia coli F. The mutant bacteriophage has been shown to be deficient in the excretion of the final products of DNA degradation during infection of E. coli F, and about 30% of the host DNA's thymine residues were reinocorporated into phage DNA. During infection with this mutant, host DNA degradation to trichloroacetic acid-soluble products was normal, host DNA synthesis was shut off normally, and second-step transfer was not delayed. However, induction of early phage enzymes and production of DNA and phage were delayed by 5 to 15 min but eventually reached normal levels. The mutant's phenotype strongly suggests that the enzyme's role is to act at the final stage in the T5-induced system of host DNA degradation by hydrolyzing deoxynucleoside 5'-monophosphates to deoxynucleosides and free phosphate; failure to do this may delay expression of the second-step-transfer DNA.
Chronic dermatitis in nutria (Myocastor coypus) in Louisiana was traced to secondary bacterial and fungal infection resulting from the penetration of achene awns of smooth beggartick (Bidens laevis) into the skin.
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