Biomedical subjects
S D Thomas
Publications and source records attributed to S D Thomas.
Face validity.
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Development of the General Health Motivation Scale.
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Intentionality in the human-environment encounter in an ambulatory care environment.
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Riboflavin status in urban adolescents.
We compared riboflavin status in 284 healthy adolescents attending an urban university hospital clinic with that of 43 adolescents with a variety of chronic medical conditions. Riboflavin status was determined by erythrocyte glutathione reductase activity and 24-hour dietary recall of riboflavin intake. The mean activity coefficient for the healthy adolescents was 1.08 (SD +/- 0.09) and 1.10 (SD +/- 1.01) in the chronically ill group. Significantly higher values were found in females of both groups (z = 4.90, p less than 0.0001). Seventeen (7%) of the healthy teenagers and seven (16%) of the chronically ill group had biochemical evidence of riboflavin deficiency (p less than 0.02). Although the mean daily intake of riboflavin for the total group exceeded the recommended daily allowance, there was significantly lower riboflavin intake in the subgroup of adolescents who had abnormal activity coefficients (z = 3.29, p less than 0.001). These data suggest that subclinical riboflavin deficiency may occur in adolescents and that deficiency may be related to dietary intake of riboflavin.
Malignant hyperthermia.
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Balloon dilatation of the aortic valve for inoperable aortic stenosis.
The place of balloon dilatation of the aortic valve in the treatment of calcific aortic stenosis is controversial. Thirty two patients (mean age 76) in whom valve replacement was contraindicated were followed up for three to 24 months (mean 8); 25 were in functional class III or IV according to the New York Heart Association's classification. Major complications of the procedure occurred in four patients. Echocardiography and Doppler studies were performed before operation and before discharge in 28 patients, and the area of the valve was measured again six to 50 (mean 23) weeks after operation in 11 patients. The peak to peak aortic pressure gradient fell from a mean of 65 (SD 24) to 46 (20) mm Hg, but the area of the aortic valve, measured by Doppler echocardiography, in 18 patients showed a modest but significant increase, from 0.61 (0.16) to 0.74 (0.23) cm2. One month after dilatation, 29 patients were alive, of whom 17 had improved symptoms. Only two had lasting clinical benefit. Sixteen patients died, 12 of a cardiac cause. The estimated one year survival rate was 49%. Six patients underwent or required valve replacement because of persisting symptoms. In view of its limited long term efficacy balloon dilatation of the aortic valve should be used only for patients with severe symptoms whose life expectancy is limited by other disease or who are considered to be unsuitable for valve replacement. It may have a role in improving the condition of patients who present with cardiogenic shock or pulmonary oedema before valve replacement is undertaken.
Purification, crystallization and properties of porphobilinogen deaminase from a recombinant strain of Escherichia coli K12.
Porphobilinogen deaminase has been purified and crystallized from an overproducing recombinant strain of Escherichia coli harbouring a hemC-containing plasmid which has permitted the purification of milligram quantities of the enzyme. Determination of the Mr of the enzyme by SDS/polyacrylamide-gel electrophoresis (35,000) and gel filtration (32,000) agrees with the gene-derived Mr of 33,857. The enzyme has a Km of 19 +/- 7 microM, an isoelectric point of 4.5 and an N-terminal sequence NH2-MLDNVLRIAT. The substrate, porphobilinogen, binds to the active-site dipyrromethane cofactor to form three intermediate complexes: ES, ES2 and ES3. The gene-derived primary structure of the E. coli deaminase is compared with that derived from the cDNA of the human enzyme.
Mithramycin selectively inhibits transcription of G-C containing DNA.
Mithramycin induces a reversible inhibition of cellular RNA synthesis without affecting DNA synthesis. The authors have shown this drug induces myeloid differentiation of HL-60 promyelocytic leukemia cells and is an effective agent in certain patients with chronic granulocytic leukemia. In order to investigate the mechanism by which this drug inhibits RNA synthesis we have compared the effect of mithramycin on RNA synthesis by whole cells, isolated nuclei, and RNA synthesis by isolated E. coli RNA polymerase and eukaryotic RNA polymerase II. Exposure of HL-60 cells to mithramycin at concentrations of 4.6 X 10(-7) m or higher for 48 hours causes an almost immediate inhibition of RNA synthesis (up to 85% at 4 hours) with only modest cytotoxicity at these concentrations. Endogenous RNA synthesis by isolated nuclei can be inhibited by mithramycin only at high concentrations (greater than 10(-5) m), suggesting that mithramycin primarily may inhibit initiation, rather than elongation. Mithramycin inhibits in vitro transcription of salmon sperm DNA by E. coli RNA polymerase at DNA:drug ratios similar to those required for RNA synthesis inhibition in whole cells. Similar DNA binding studies with synthetic oligonucleotides demonstrate that mithramycin is a potent inhibitor of transcription of Poly dG.dC by E. coli RNA polymerase but has no effect on transcription of Poly dA.dT. The rapid inhibition of whole cell and isolated RNA polymerase transcription, and the relative insensitivity of isolated nuclei, suggest mithramycin may interact with specific DNA sequences in order to inhibit the initiation of RNA synthesis in intact cells.
Self-retaining U-tube nephrostomy.
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Death expectancies in alcoholic and nonalcoholic persons.
The Do-It-Yourself Death Certificate (DIYDC) was administered to a group of alcoholic inpatients (N = 39) and to a group of university employees (N = 39). The groups were matched on age, sex, and race. Both alcoholics and nonalcoholics projected unrealistic expectations about their deaths when compared with actuarial cause of death data, but this was somewhat more true of those in the alcoholic group, who expected to live longer than would be expected and who only infrequently attributed their deaths to drinking. Strong preferences were expressed for a quick death, and some differences were observed between the groups with regard to seasonal expectations of time of death and attitudes toward life-prolonging techniques. The DIYDC appears to be a useful adjunct to existing methods of death research, and it may have practical applications with some clinical groups, provided that certain ethical considerations are observed.
Primary amyloidosis of urinary bladder and ureter: cause of mural calcification.
Primary amyloidosis is seen in the absence of predisposing disease. It may affect most organs in the body, including the collecting system of the urinary tract. Submucosal calcifications have been described in the renal pelvis and may be pathognomonic for primary amyloidosis of the renal pelvis. We have been able to demonstrate similar submucosal calcifications in the ureter and bladder. The differential diagnosis of submucosal calcification of the distal ureter and bladder must include bilharziasis and tuberculosis. With the recognition of submucosal calcifications, diagnosis of the underlying disease may be readily made. An illustrative case is presented.
Assessing alcoholism treatment effectiveness. A comparison of three evaluative measures.
The success rates of patients in an alcoholism treatment unit were evaluated according to three criteria: vocational rehabilitation, abstinence and a behavioral rating scale. The three measures yielded success rates of 70, 34 and 62%, respectively.
Eye injury during transurethral surgery.
An injury to a surgeon's cornea, which resulted in permanent damage, is reported. The accident could have been prevented if there had been no exposed metal in the telescope eyepiece and if the surgeon had been wearing glasses. Any telescope with exposed metal in the center of the eyepiece should be returned to the manufacturer for replacement with a more protective and insulated type of eyepiece.