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Biomedical subjects

J D Buchanan

Publications and source records attributed to J D Buchanan.

33 records · Page 2Linked to original sources
PubMed1981

Angiodysplasia.

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Colon↗
PubMed1981

Anaerobic and other fastidious microorganisms in asymptomatic bacteriuria in pregnant women.

Urine from 44 pregnant women with known or suspected renal disease (group 1) and from 50 healthy pregnant women (group 2) with negative routine cultures of midstream urine was obtained by suprapubic aspiration. Aerobic and anaerobic cultures showed bacteriuria in 70% of the women in group 1 and in 26% of those in group 2. Gardnerella vaginalis was the most frequently isolated organism. Ureaplasma urealyticum was isolated from 14(48%) of 29 women in group 1 and from two (12.5%) of 16 women in group 2. Radiologic studies showed a high incidence of underlying renal disease in asymptomatic women with bacteriuria. Localization testing indicated kidney infection in six of 14 women in group 1 and in one of four women in group 2. These findings suggest that there is an increased susceptibility to colonization of the bladder with these microorganisms during pregnancy and that persistence of infection and renal involvement are associated with underlying renal disease.

Anaerobiosis↗
PubMed1978

The radiolysis of glyceraldehyde-3-phosphate dehydrogenase.

The yields in molecules per 100 eV for active-site and sulphydryl loss from glyceraldehyde-3-phosphate dehydrogenase have been determined in nitrous-oxide-saturated, aerated and argon-saturated solutions. Molecular hydrogen peroxide produces a sulphenic acid product, which can be repaired by post-irradiation treatment with dithiothreitol. Comparison of the yields under various conditions showed that in aerated solutions both .OH and .O2-radicals inactivated the enzyme with an efficiency of about 26 per cent. However, the efficiency of .OH in air-free solutions was less, and inactivation by .H and eaq- did not appear to be appreciable. There is a correlation between SH loss and loss of active sites.

Air↗
PubMed1978

Interaction of aminoacridines with nucleic acids. A pulse-radiolysis study.

Pulse radiolysis has been used to study the interaction of aminoacridines with nucleic acids. The data confirm that there are two modes of binding. These are: a weak interaction which has a maximum binding ratio of one site per dye; and a strong binding process effected by both electrostatic and Van der Waals interactions. The limit of this latter, strong binding mode is approximately six sites per dye. The radiation-induced transient absorption spectrum of benzoflavine is characterized by a pronounced bleaching at 440 nm, which is quenched by the addition of nucleic acids. Mechanisms have been proposed for the reactions of both eaq-and .OH with benzoflavine which account both for the observed bleaching of benzoflavine solutions and for the protective effect of nucleic acids. It is proposed that eaq-reacts with benzoflavine to form a stable benzoflavine semiquinone radical and that .OH reacts with subsequent formation of a very stable benzoflavine hydroxycyclohexadienyl radical.

Acridines↗
PubMed1977

Pulse radiolysis of lactate dehydrogenase.

Pulse radiolysis has been used to investigate the rates and transient spectra for the reactions of free radicals with beef heart lactate dehydrogenase at pH 7. Analysis of the results leads to second-order rate-constants for eaq-, .OH, .I, .Br2-, .I2- and .(CNS)2- which are, respectively, 24, 21, 10, 0.55, 0.43 and 0.15 in units of 10(10) M-1 s-1 with uncertainties of +/- 20 per cent. Those for .I and .I2- are similar to the corresponding rate-constants for the related enzyme alcohol dehydrogenase. The spectra of the transient species produced by .OH, .Br2- and .(CNS)2- all showed evidence for reactions with tyrosine and tryptophan residues, and in general terms the magnitudes of the rate-constants appeared to increase with the oxidizing abilities of the radicals. The implication of the results for understanding the mechanism of deactivation by free radicals is discussed.

Animals↗
PubMed1976

Free radical inactivation of lactate dehydrogenase.

The enzyme lactate dehydrogenase (LDH) has been irradiated under various conditions to assess the relative contributions of -H, -OH, H2O2 and -O2- to LDH inactivation, and it is concluded that -OH is the only important inactivating species. Further the effect of the selective free radicals, -(SCN)2-, -Br2- and -I2- on the activity has been studied. In neutral solution, the order of inactivating effectiveness is -I2- greater than -OH greater than -Br2- greater than -(SCN)2-. At pH 8-6, -OH and -Br2- are approximately equal in effectiveness, whereas -(SCN)2- is the least efficient. The radiation inactivation of LDH is accompanied by a loss of sulphydryl groups, and it is suggested that the primary target for radiation damage in LDH is the active site cysteine-165. Subsequent conformational changes are suggested to account for the apparent loss of coenzyme-binding ability and changes in the enzyme's kinetic parameters. The effect of bound coenzyme (NAD) on radiation-induced inactivation of N2O and air-saturated solutions was also investigated, and it is shown that NAD binding protects LDH.

Cobalt Radioisotopes↗
PubMed1975

Return of spermatogenesis after stopping cyclophosphamide therapy.

A follow-up of twenty-six male patients with azoospermia after stopping cyclophosphamide treatment showed a return of spermatogenesis in twelve patients within 15-49 months (mean 31 months). In one patient spermatogenesis returned despite 34 months of treatment with 100 mg. of cyclophosphamide daily. The period of follow-up after stopping cyclophosphamide therapy varied from 5 months to 4 years. After 6 months on cyclophosphamide all patients remained azoospermic while taking the drug. Return of spermatogenesis was not significantly associated with age, duration of cyclophosphamide therapy, total dose, or time of follow-up after stopping treatment; however, the number of patients in the study was small.

Adult↗