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Biomedical subjects

R G Thomas

Publications and source records attributed to R G Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1987

The effects of continuous phonation on 133xenon-inhalation air curves (of the kind used in deriving regional cerebral blood flow).

Regional cerebral blood flow (rCBF) may be measured with inhalation techniques that use end-expired values of radioactivity to estimate the isotope concentration in arterial blood. These end-expired data are used as an input function in a mathematical equation to derive rCBF. End-expired air is assumed normally to be in equilibrium with the arterial blood at the alveolar surface of the lung during regular (passive) breathing; this assumption may not be valid during continuous phonation. We therefore have analyzed breathing (inhalation/exhalation) patterns and end-expired radioactivity (133Xe) during (1) speaking, (2) singing, and (3) humming of the national anthem, and also during (4) passive breathing. Statistically significant differences in breathing patterns were measured between a group of nonmusicians and two groups of musicians (singers) during the phonation tasks: The nonmusicians breathed more often (and more rapidly) and exhibited less variability in their breathing patterns than did the musicians. Notwithstanding these differences, the shapes of smoothed functions derived from the end-expired values were not influenced appreciably during phonation (except possibly during talking). The latter finding suggests that estimates of rCBF derived with these data should not be confounded seriously because of the continuous phonation.

Adolescent↗
PubMed1987

Effects of behavioral self-management on oral hygiene adherence among orthodontic patients.

Twenty-nine new orthodontic patients and 30 experienced orthodontic patients received either behavioral self-management of toothbrushing and mouth rinsing or an experimental regimen that consisted of prompting by the orthodontist to brush and rinse regularly plus instructions to turn in home care materials during orthodontic visits. Several sets of data showed uniformly high rates of brushing and rinsing among all four groups of subjects. Several data sets also showed significant improvements in oral health status among all four groups. Substantive and methodologic directions for future research are delineated.

Adolescent↗
PubMed1987

Hearing loss among stroke patients.

Pure-tone hearing thresholds were measured by air conduction for 140 right hemiplegic and 103 left hemiplegic patients who had suffered a single stroke. Statistical and informal testing of the mean audiometric thresholds revealed that: (1) the ability of the aphasic patient to attend to and to perform the audiometric test was independent of the severity of the aphasic impairment; (2) aphasic patients did not suffer disproportionately greater hearing losses than did other right hemiplegic stroke patients; (3) no relation was apparent between the severity of the hearing loss and the test ear or side of hemiplegia after stroke; (4) the severity of high-frequency hearing loss among stroke patients was consistent with that found in the elderly male population at Framingham, MA (Moscicki, Elkins, Baum, and McNamara, Ear Hear 1985;6:184-90); and (5) the prevalence of hearing loss among the stroke patients was greater than that reported at Framingham, but was consistent with rates found among elderly nursing home residents.

Adult↗
PubMed1987

Gonadal dysfunction in diabetic men with organic impotence.

Previous studies of the relationship of gonadal function to impotence in men with diabetes mellitus have yielded conflicting results. Pituitary-testicular function was studied in 28 impotent diabetic men and 15 normal men. Impotence was documented by clinical history and subdivided into categories of primary organic (n = 16), primary psychogenic (n = 7), and unclassified (n = 5) on the basis of nocturnal penile tumescence (NPT) testing, psychological testing, and penile vascular studies. All NPT parameters were diminished (P less than or equal to 0.001) in the impotent diabetic men compared to values in the normal men. Endocrine studies revealed increased urinary LH (P less than or equal to 0.05) and diminished serum free testosterone levels in the diabetic men with primary organic impotence. These changes were not found in normal men or diabetic men with primary psychogenic impotence. Six months of treatment in a home blood glucose-monitoring program resulted in significant improvement in metabolic control but no improvement in pituitary-testicular function, NPT, or sexual performance in the primary organic impotent group. Eight patients with primary organic impotence and no evidence of penile vascular disease had significant improvement (P less than or equal to 0.01) in NPT results as well as subjective improvement in sexual function after 6 months of parenteral testosterone administration. These studies suggest that primary gonadal dysfunction may be related to organic impotence in diabetes, and improvement in selected patients can occur with androgen therapy.

Adult↗
PubMed1986

Resectable pulmonary nephroblastoma metastases presenting as chest wall lesions on radiography. A report of 2 cases.

Two children with pulmonary metastases from nephroblastomas showed the radiological features of chest wall tumour involvement. Diagnostic surgical exploration subsequently revealed pedunculated and fully resectable peripheral lung metastases. The mechanism by which these pedunculated lesions mimicked the classic 'D sign' of an extrapulmonary (pleural or chest wall) tumour is explained.

Child, Preschool↗
PubMed1986

Iodine retention and thyroid dysfunction in patients on hemodialysis and continuous ambulatory peritoneal dialysis.

Povidone-iodine is frequently used as an antiseptic in patients on chronic dialysis. In order to determine if the use of povidone-iodine affects thyroid function in these patients, we measured serum iodine and thyroid hormone levels in dialysis patients prior to and following discontinuation of topical povidone-iodine antiseptics. Serum inorganic iodine levels were elevated initially in nearly 90% of the patients (19 on hemodialysis, 12 on continuous ambulatory peritoneal dialysis [CAPD]). Following discontinuation of povidone-iodine, iodine levels over a 3-month period decreased modestly in patients on CAPD (n = 5) and were unchanged in patients on hemodialysis (n = 5). Total and free thyroxine levels were frequently low but did not correlate with protein-bound or inorganic iodine levels and did not change after discontinuation of povidone-iodine. Thyrotropin levels correlated significantly (r = .62, P less than .01) with inorganic iodine levels in patients on hemodialysis, but not for patients on CAPD. We conclude that abnormal thyroid function tests are common in dialysis patients but are not related to iodine retention or to the routine use of topical povidone-iodine-containing antiseptics.

Adult↗
PubMed1986

The value of ultrasound in the diagnosis of renal failure.

Seventy-four patients with impaired renal function were investigated by ultrasound. By assessing renal length, renal echogenicity and collecting system dilatation, one can establish whether renal function is impaired by chronic or acute renal changes or by obstructive changes.

Humans↗
PubMed1985

Simple ureteroceles--ultrasonographic recognition and diagnosis of complications.

Ultrasound scans were performed on 6 adult males with simple ureteroceles, 2 of which were detected on primary scanning of patients in renal failure and 4 after excretory urography. Two complications were also detected--obstruction with hydro-ureter formation and tumour formation in a ureterocele. A scheme is proposed for differentiating ureteroceles from other causes of bladder filling defects using ultrasound examination.

Adult↗
PubMed1985

Proton imaging with surface coils on a 0.15-T resistive system.

Coil development is fundamental to the optimization of imaging systems at any field; however, it is especially critical for low-field systems where signal strength is limited. Here we demonstrate a type of surface coil design which makes possible the acquisition of high-quality images of the neck and extremities.

Humans↗
PubMed1985

Plutonium in gonads: a summary of the current status.

A review of the literature was carried out to investigate the following: the fraction of Pu in the body that was in the gonads; the necessity for a localization factor in calculating the genetic dose to humans; and the possibility that an unexpectedly high relative biological effectiveness (RBE) causing genetic effects could occur for alpha particles. Human autopsy data from both occupationally exposed persons and the public were relied on to determine the amount of Pu in the gonads. It was found that an average fraction of 3 X 10(-3) of the Pu in the body was in the ovaries and testes but there was a wide variation among individuals. While a localization factor over the average of 2.5-4 is needed to calculate the dose to the sensitive cells for rodents, no such factor is required for the human. Information on the RBE for various genetic effects shows RBEs for Pu alpha's about as would be expected from neutron irradiation. The usual quality factor applied in calculating dose equivalent is appropriate and may be conservative, particularly for females.

Alpha Particles↗
PubMed1984

131I macro-aggregated albumin perfusion scanning and chest radiography in asbestos exposure.

131I macro-aggregated albumin perfusion scanning and conventional radiography were used to study the lungs of 108 men who had been exposed to asbestos dust. The presence or absence of basal crackles was recorded in all cases. Forced vital capacity (FVC) was measured in 94 cases. Underperfusion of the lower zones of the lungs was considered to be present in only 8 of 39 cases with small irregular opacities classified as category 1/0 or higher on the 1971 International Labour Organization classification for pneumoconiosis. In 5 of 69 cases classified in categories less than 1/0, perfusion in the lower zones appeared to be impaired. Details of these cases are given. Underperfusion was more common among men with basal crackles or reduced FVC (less than 80% of predicted value) but this trend was not statistically significant.

Adult↗
PubMed1984

The value of computerised axial tomography in the assessment of workers exposed to asbestos.

Nineteen men who had been exposed to asbestos for long periods were subjected to an examination of the lungs by means of computerised axial tomography (CT). Some features of asbestos-related disease are shown better on CT than on conventional roentgenograms, and occasionally features not shown at all on conventional films may be demonstrated on CT. It was concluded that CT may be useful in cases with borderline and doubtful signs on conventional films, and very occasionally in persons with long exposure who have normal conventional films.

Asbestosis↗
PubMed1984

Magnesium therapy in massive digoxin intoxication.

A potentially fatal case of massive digitalis intoxication is presented. Recurrent ventricular fibrillation failed to respond to lidocaine or phenytoin, but responded dramatically to magnesium sulfate infusion. A review of the literature and previous clinical studies, as well as the case reported here, appears to indicate that magnesium sulfate given intravenously in adequate quantities (2 to 3 g in one minute followed by 2 g/h for 4 to 5 h) is effective in controlling ventricular irritability caused by toxic levels of digitalis preparations.

Digoxin↗
PubMed1984

Plutonium partitioning among internal organs.

An estimate of partitioning of plutonium among skeleton, liver, and other organs is needed to estimate the radiation dose to individual organs. This review was done to provide an analysis of the coefficients currently used for the translocation of plutonium from blood to other organs and excreta. Data from both experimental animals and human autopsy cases were used in our analysis. The analysis of data from 257 experimental animal and 169 human subjects led to a conclusion that a 70-30% split of plutonium distribution between skeleton and liver, respectively, would be appropriate for use in plutonium organ distribution models. Analysis of data from other organs and early excreta indicated that these other compartments generally comprised less than 3% of the total early body burden. The variability of plutonium distribution within all compartments is emphasized, with the conclusion that the coefficients of uptake to individual organs are adequate to estimate average organ doses for an exposed population but use for estimating doses for an individual will lead to uncertain results.

Animals↗
PubMed1983

Early prediction of the adult respiratory distress syndrome by a simple scoring method.

Early identification of patients who will develop the adult respiratory distress syndrome (ARDS) is important in prognosis, management, and candidate selection for studies that evaluate both pathophysiology and early therapy. The purpose of this study was to improve the accuracy of early prediction of ARDS by using a simple scoring method that combines the weighted risks from individual risk factors. By a discriminant function analysis of 136 patients with one or more clinical conditions predisposing to risk of ARDS, simple linear equations were derived in which several different risk factors, weighted by coefficients, served as the variables. We developed several equations from which individual "ARDS scores" could be calculated, and we found retrospectively that half the 46 patients who had developed ARDS scored higher than a particular "index score," while about 90% of the patients who never developed ARDS scored less than that index despite the presence of significant risk factors. We then prospectively tested these equations in 87 other patients and found similar results. In summary, a simple clinical scoring system which can be used soon after admission can identify, with reasonable accuracy, individual patients who are almost assured of developing ARDS.

Humans↗