Biomedical subjects

J C Thornton

Publications and source records attributed to J C Thornton.

At least 19 recordsLinked to original sources

PubMed1995

Bone mineral and body fat measurements by two absorptiometry systems: comparisons with neutron activation analysis.

In 185 adults (68 white and 31 black males, 66 white and 20 black females), total body bone mineral density and content and body fat% were measured by two dual energy X-ray absorptiometry (DXA) systems--Norland XR-26, software version 2.4, and Lunar DPX, software versions 3.4 and 3.6. In a subgroup of 18 males (10 white, 8 black), body fat% and total body calcium were also measured by in vivo neutron activation analysis (IVNA). For total body calcium, the DPX 3.4 system gave the highest (1239 g), IVNA the lowest (1195 g), and the XR-26 (1226 g) was not significantly different from the DPX 3.6 results. For fat%, the XR-26 system gave the highest estimate (23.5%), whereas measurements by the DPX 3.4 and 3.6 systems (17.4 and 18.2%) were similar to the IVNA measurements (18.3%). BMD and BMC measurements by the two DXA systems were highly correlated but significantly different for the entire studied population except in the case of BMC in black males.

Absorptiometry, Photon↗

PubMed1995

Prediction equations for balance measured as sway speed by head tracking with eyes open and closed.

OBJECTIVES: To provide prediction equations for balance measured as sway speed, a population of randomly selected subjects was used as a model. METHODS: 265 subjects were selected from voter registration rolls in Arizona and Louisiana, USA. For validation these predicted values were compared with observed values obtained from a second population in California, USA. RESULTS: Sway speed with eyes open as a natural logarithm was: 1n (open) = -0.248333 -0.009634 x age +0.000164 x age2 and sway speed with eyes closed was: 1n (closed) = -0.585707 -0.023074 x age +0.000315 x age2 + 0.038496 x height (cm) CONCLUSIONS: The natural logarithm of balance with the eyes open was related to age by both linear and quadratic functions. Additionally with the eyes closed balance was dependent on height. These equations can be used to predict performance of groups being studied for effects of noise and chemicals. To define abnormality of individual subjects the predicted value plus 1.5 SDs could be used.

Adolescent↗

PubMed1995

Do radiographic criteria for emphysema predict physiologic impairment?

OBJECTIVE: The functional consequences of pulmonary emphysema have been estimated from autopsy studies. This antemortem study correlates structure as assessed by criteria applied to chest radiographs and function in earlier disease. SUBJECTS AND METHODS: Four thousand one hundred seven male shipyard and construction workers had chest radiographs scored for asbestosis using International Labour Office criteria and for emphysema using five criteria: hyperlucent lung fields, low flat diaphragms on posteroanterior views, low flat diaphragms on lateral radiographs, a wide retrosternal space, and bullae. Total lung capacity (TLC) was measured by planimetry of radiographs and forced vital capacity (FVC) and flows by spirometry: TLC minus FVC equaled residual volume (RV). All were expressed as percentage of predicted (% pred) adjusted for height, age, and duration of cigarette smoking. Linear regression modeling examined the influence of each emphysema criterion on function measurements. RESULTS: Four hundred three (10.1%) of 4,107 men had two or more emphysema criteria and 24.5% had asbestosis. Prevalence of 2 criteria varied by smoking status and was present in 20% of current smokers, 7.5% of ex-smokers, and 2% of never smokers. The TLC % pred and RV/TLC increased and % pred of FEV1/FVC and FEF25-75, FEV1, and FVC decreased with increasing radiographic emphysema criteria. Forty-four (10%) had normal results of spirometry with two or more radiographic emphysema criteria. CONCLUSION: Impairment of airway function worsened with each additional radiographic criteria of emphysema. These criteria were more strongly associated with an increase in RV/TLC than an increase in TLC.

Asbestosis↗

PubMed1994

Asians have lower body mass index (BMI) but higher percent body fat than do whites: comparisons of anthropometric measurements.

We studied the correlations between body mass index (BMI) and percent body fat (fat%) measured by dual-photon absorptiometry (DPA) in 445 white and 242 Asian adults aged 18-94 y. In addition, comparisons in six circumferences and eight skinfold-thickness measurements between whites and Asians were made to explain the discrepancies. Although Asians had lower BMI, they were fatter than whites of both sexes. The correlations between fat% and BMI varied by BMI and sex and race. Comparisons in anthropometry show that Asians had more subcutaneous fat than did whites and had different fat distributions from whites. Asians had more upper-body subcutaneous fat than did whites. The magnitude of differences between the two races was greater in females than in males. Prediction equations developed for each sex and race, based on BMI alone, gave SEEs ranging from 4.4% to 5.7%. All were significantly improved to the range of 3.5-4.4% when age and several skinfold-thickness measurements were added.

Adipose Tissue↗

PubMed1993

Biological homogeneity and precision of measurement: the boundary conditions for normal in body composition.

For compartments most urgently important to clinical medicine we have satisfactory levels of measurement precision, and the clinical considerations now are the availability of the methods, and the collection of data for normal subjects. Our colleagues in physics and imaging will improve measurement precisions, but the work most needed is to refine the biological side of the measurement equation. Large numbers of measurements, carefully done with carefully calibrated and unchanging systems, exist only for the special case of measuring body calcium in women, in the large cohort of approximately 2,500 women, studied by Aloia and Cohn with neutron activation, and for body potassium, in these women, and in the larger numbers of diverse age, sex, race, and size in the Rosetta study in our laboratory. Can we benefit from the "orthogonal measurements" and "orthogonal physiologic constraints" approaches, in which triangulation is used to combine measurements from several techniques to establish upper-lower bounds estimates by different techniques, with convergence on a "best fit" result? We have noted that the intrinsic homeostatic mechanisms of the body function with great precision to control body temperature, osmotic and ionic concentrations in the water phase, hypertrophy of muscle with exercise, and remodeling of bone by stress. We consider it unlikely that the control mechanisms are more loosely hinged for such secondary parameters as K/FFM and bone density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

Expiratory flows decreased in Los Angeles children from 1984 to 1987: is this evidence of effects of air pollution?

To estimate the effects of air pollution we measured expiratory flows and vital capacities in 556 Mexican-American Los Angeles children in 1984 and 251 in 1987. They included 106 who were measured in 1984 and 1987 and 145 measured only in 1987. Pulmonary function values were standardized for growth be expressing them as percentages of predicted (% pred) based on sex and height. In 1987 mean values for FEV1 and FEF25-75 were lower by 4.5% pred and 13.6% pred respectively (P < 0.001), while vital capacities were not different in 213 children tested as fifth graders in 1984 and 251 fifth grade children in 1987. For the 106 children tested at both sessions (in second grade in 1984 and in fifth grade in 1987) FVC was also not different but FEV1 was 2.0% pred lower (P < 0.06) and FEF25-75 was 7.0% pred lower (P < 0.001). For the 450 children tested only in 1984 and the 106 retested in 1987 there were no significant differences in mean values for FVC, FEV1, and FEF 25-75. Similarly there were no significant differences between the 1987 mean values for 145 children who were studied longitudinally were not different from the 1984 and 1987 cross-sectional cohorts. Across this interval FEV1 and midflows diminished but vital capacities did not. Airways obstruction worsened during children's residence in Los Angeles from 1984 to 1987 and this is probably due to air pollution.

Air Pollutants↗

PubMed1992

Body composition and surgical treatment of obesity. Effects of weight loss on fluid distribution.

Obesity is associated with absolute and relative expansion of the extracellular water compartment (ECW). The effects of substantial and prolonged weight reduction on body water distribution are unknown, however. The authors studied total body water (TBW) by tritiated water dilution, ECW by 35SO4 dilution, exchangeable sodium (Na(e)) by 24Na, and total body potassium (TBK) by 40K whole-body counting in 25 severely obese women (body mass index [BMI] = 48 +/- 7 kg.m-2, mean +/- standard deviation) aged 36 +/- 8 years before and at intervals after gastric restrictive (GR; n = 12) and malabsorptive (MA; n = 13) operations for obesity. Results are compared with a control group of 26 healthy normal-weight women (BMI = 21 +/- 2). Before operation, the obese patients had absolute elevations of all water compartments compared with controls, with significantly higher ratios of Na(e) to TBK (1.17 +/- 0.13 versus 0.91 +/- 0.10; p less than 0.05) and ECW to intracellular water (ICW) (E/I = 0.82 +/- 0.17 versus 0.63 +/- 0.06; p less than 0.05). After weight loss of 52 +/- 20 kg in MA and 47 +/- 19 kg in GR patients (nonsignificant between groups) to a stable level 22 +/- 8 months after operation, there were statistically significant reductions in TBW, ICW, TBK, and Na(e) in both groups, but a significant reduction in ECW only after GR. Adjusting for preoperative weight, duration of follow-up, and rate of weight loss, E/I was greater after MA than GR (1.09 +/- 0.25 versus 0.82 +/- 0.14; p less than 0.05). The elevated preoperative E/I ratio did not normalize with weight loss after surgery, and the response was related to the type of operation. The finding remains to be explained although the increased E/I after MA may reflect mild protein-calorie malnutrition not detectable in the blood. The persistence of elevated E/I with significant weight loss after GR might imply an intrinsic or irreversible imbalance of fluid distribution in obese patients.

Adult↗

PubMed1992

Predictive equations for total lung capacity and residual volume calculated from radiographs in a random sample of the Michigan population.

BACKGROUND: Published predicted values for total lung capacity and residual volume are often based on a small number of subjects and derive from different populations from predicted spirometric values. Equations from the only two large studies gave smaller predicted values for total lung capacity than the smaller studies. A large number of subjects have been studied from a population which has already provided predicted values for spirometry and transfer factor for carbon monoxide. METHODS: Total lung capacity was measured from standard posteroanterior and lateral chest radiographs and forced vital capacity by spirometry in a population sample of 771 subjects. Prediction equations were developed for total lung capacity (TLC), residual volume (RV) and RV/TLC in two groups--normal and total. Subjects with signs or symptoms of cardiopulmonary disease were combined with the normal subjects and equations for all subjects were also modelled. RESULTS: Prediction equations for TLC and RV in non-smoking normal men and women were square root transformations which included height and weight but not age. They included a coefficient for duration of smoking in current smokers. The predictive equation for RV/TLC included weight, age, age and duration of smoking for current smokers and ex-smokers of both sexes. For the total population the equations took the same form but the height coefficients and constants were slightly different. CONCLUSION: These population based prediction equations for TLC, RV and RV/TLC provide reference standards in a population that has provided reference standards for spirometry and single breath transfer factor for carbon monoxide.

Adult↗

PubMed1991

Prevalence of spirometric abnormalities in a representative sample of the population of Michigan.

A random sample of a large industrial state in the United States (Michigan) was studied via respiratory questionnaire, medical history, physical examination, and spirometry: 976 white adults performed a battery of spirometric tests (FVC, FEV1, FEV1/FVC and FEF25-75%). Using predictive equations derived from normal subjects in the survey and defining spirometric abnormality by the lower 95% confidence interval, prevalences of abnormality were greater in those who had a smoking history. When equations derived from normal non-smokers were used, as has been the general practice, 21.3% of men and 18.5% of women with a positive smoking history had an abnormal FEV1 and 26.7% and 17.8% an abnormal FEF25-75%, respectively. Although FVC is thought to be affected little by smoking, mean values were lower and prevalences of abnormal values higher in smokers. Prevalences are also shown using an adjustment for the effect of smoking and using conventional (percent of predicted value) definitions of spirometric abnormality. The prevalences of spirometric impairments in this cross section of a large state should be useful for comparison with other populations under study in North America.

Adult↗

PubMed1991

Surface-disorganized, attenuated mutants of Aeromonas salmonicida as furunculosis live vaccines.

A slow-growing, aminoglycoside-resistant mutant and a rapidly-growing pseudo-revertant were isolated from Aeromonas salmonicida, the causative agent of salmonid furunculosis. These mutants continued to elicit a variety of classical virulence factors associated with A. salmonicida pathogenesis. They differed morphologically from the wild-type and from one another with respect to A-layer organization, membrane antagonist sensitivity and particularly to aerobic metabolism. Both mutants were drastically altered in the architecture of the 2D crystalline surface array (A-layer), although both were similar to wild-type with respect to cell surface composition. The slow-growing, antibiotic-resistant mutant differed significantly from the wild-type by the apparent loss of virtually all aerobic metabolism; the pseudo-revertant had partially recovered the ability to aerobically metabolize certain carbon sources. Both mutants were avirulent and incapable of tissue persistence. The rapidly-growing, antibiotic-sensitive pseudo-revertant, when administered either intraperitoneally or by immersion, effectively protected salmonid fish from challenge by a heterologous virulent stain suggesting its candidature as a live, attenuated furunculosis vaccine.

Aeromonas↗

PubMed1991

Measuring body fat: calibrating the rulers. Intermethod comparisons in 389 normal Caucasian subjects.

A systematic study of 389 normal Caucasians stratified for sex and age compared all of the traditional methods for measuring fat: body water, underwater weighing, body potassium, and anthropometrics and the newer methods of dual-photon absorptiometry, bioimpedance analysis, and total body electrical conductivity. Measurements by all methods are highly intercorrelated, but methods differences show the population means for fat percent to range from 26 to 35% of body weight across eight methods. All methods show increasing fat (as % body weight) with age in both sexes but vary in secular slope. The goal of this report is to provide direct translations between each of the eight methods. Intermethod comparison equations are given as simple linear regressions by using each method both as dependent and independent variable for each sex, permitting translation for results by any method to any other.

Adipose Tissue↗

PubMed1990

Cross-shift and chronic effects of stainless-steel welding related to internal dosimetry of chromium and nickel.

Ninety welders from a stainless-steel fabricating plant were studied by pulmonary function tests and serum and urine chromium and nickel levels, cross-sectionally, and 31 were compared across a Monday shift. They had welded for a mean of 11 years, mean age was 44 years, and mean smoking duration was 20 years in 62 current smokers. Baseline spirometric tests were significantly reduced: FVC to 95.4 mean percentage of predicted (pop), FEV1 to 94.5 pop, FEF25-75 to 85.9 pop, and FEFR75-85 to 74.8 pop. Current smokers had greater reductions in flow rates and FVC than nonsmokers even after adjustment of their predicted values for the effects of duration of smoking. Neither alveolar volume at 104.3 pop nor diffusing capacity for carbon monoxide (single breath) at 98.5 pop was reduced. There were no significant changes in pulmonary function measurements across a Monday workshift in 31 welders, but in seven men who welded stainless steel, levels of serum chromium (Cr) rose 66% from 1.9 +/- 2.1 micrograms/liter and urinary Cr increased 22%. Serum nickel levels rose only 7%, although they were elevated before shift, 1.1 +/- 0.4 micrograms/liter (compared with 0.21 +/- 0.20 micrograms/liter in controls), and urinary nickel levels did not increase. Eleven years of welding had reduced vital capacities and expiratory flows. Monday stainless-steel welding raised the serum and urine chromium levels (measures of internal dosimetry for exposure) but did not decrease pulmonary function values.

Adult↗

PubMed1989

Efficacy of a nonrestricted fat diet in patients with cystic fibrosis.

We sought to determine if an increased oral intake with a noninvasive nutrition program in patients with cystic fibrosis could influence growth, weight gain, and pulmonary function. Thirty-seven patients, aged 2 to 27 years, were instructed to consume a nonrestricted fat diet during an intervention period of 4 years. The results showed that patients increased the mean energy intake significantly to a level of more than 120% of the recommended daily allowance. The enhanced intake resulted in significant weight gain. Pulmonary function (forced expiratory flow 25%-75%) deteriorated during the 2-year preintervention period but stabilized during the 4-year intervention period. Both male and female patients were able to maintain their established height and weight scores during adolescence. The recommendation for a high-energy diet with no restrictions placed on the fat intake and the control of the steatorrhea by administration of an optimal enzyme dosage is supported by our data. Individualized nutritional counseling should be attempted before implementing invasive nutritional intervention programs.

Adolescent↗

PubMed1989

An examination of factors that could affect choice reaction time in histology technicians.

Histology technicians exposed to formaldehyde and solvents have symptoms and objective evidence of neurobehavioral impairment of memory, judgment, and equilibrium. Because reaction time has been prolonged in many groups of workers exposed to toxicants, choice reaction time was measured in 385 female formaldehyde and solvent-exposed histology technicians, and 79 unexposed female laboratory workers. Choice reaction time to a visual stimulus (CRT) is defined, for the purpose of this study, as the time required for discriminated cancellation of two different letters on a microcomputer screen by pressing the matching keys. Initial analysis showed that increases in age, years of cigarette smoking, and hours per day of formaldehyde exposure significantly lengthened CRT, but xylene-toluene exposure had no effect. Since duration of smoking and length of daily formaldehyde exposure were age related, multiple linear regression analysis of CRT was performed using them as independent variables. Increasing age was the only significant factor in lengthening CRT. However, in these female histology technicians, the second measurement one year later was 44 msec faster (p less than .04). The reason for improved performance is unclear, but it may be an effect of training encompassing familiarity, improved attention, or learning.

Environmental Exposure↗

PubMed1989

Choice (CRT) and simple reaction times (SRT) compared in laboratory technicians: factors influencing reaction times and a predictive model.

Choice reaction time (CRT) and simple reaction time (SRT) tests were administered to 151 female histology laboratory technicians to determine if occupational exposure to organic solvents and formaldehyde delayed either or both. The relationships between CRT and SRT latencies were evaluated using different testers, sequences of administration, and microcomputers. Formaldehyde exposure, cigarette smoking history, ethnicity, and alveolar CO levels did not significantly influence CRT and SRT. However, slightly different protocols did significantly affect SRT. A linear model demonstrated that logSRT (LSRT) and LogCRT (LCRT) were longer with increasing age, promising further clinical applications. It is concluded that both CRT and SRT measure some overlapping and some different neurologic pathways. Reaction times in large "normal" populations are needed to compare with groups exposed to potential neurotoxins.

Adult↗

PubMed1989

Respiratory symptoms and functional impairment from acute (cross-shift) exposure to welding gases and fumes.

One hundred forty-five male welders from a West Coast shipyard were studied cross-sectionally and across a Monday work shift by pulmonary function tests and a questionnaire. Ten years of welding was associated with chronic bronchitis in 23.3% of nonsmokers compared to 3.3% in male controls, shortness of breath in 31.5% of nonsmokers compared to 1.5% in controls, and chest pain or heaviness in 38.4% compared to 4.4% in controls. Men who welded aluminum but had never smoked had more frequent wheezing, chest tightness, phlegm, feverishness and fatigue than those welding mild (black) or stainless steel. There were no significant cross-shift effects from welding exposure on measurements of pulmonary function. Although baseline expiratory flows were reduced slightly when compared to Caucasian-predicted values, ethnic specific comparisons for the largest subgroup showed only that FEF25-75 was reduced to 92.9 percentage of predicted values. Diffusing capacities for carbon monoxide were significantly reduced as compared to referents. The pulmonary function values of 25 current smokers were indistinguishable from the 41 who had never smoked, which probably reflects their low consumption of cigarettes.

Acute Disease↗

PubMed1989

Pulmonary function in histology technicians compared with women from Michigan: effects of chronic low dose formaldehyde on a national sample of women.

Chronic workplace exposure to formaldehyde and solvents at low doses reduced pulmonary function in 280 non-smoker white women working as histology technicians. They were studied during national workshops at four United States cities for four years. Height and age adjusted comparisons of pulmonary function were made with women in a stratified random population sample of Michigan and with a selected subset of the population that was used to model predictive pulmonary equations for function. The major functional change in histology technicians was a steeper decrement in vital capacity and flows from age 20 to 60 by regression analysis than occurred in the modelled Michigan population. Furthermore non-smoking and currently smoking women studied at two sites had significantly lower flows than were found in the sample of Michigan women. There was no consistent effect of an aerosol bronchodilator on flows of women at the four sites. Diffusing capacity for carbon monoxide single breath and alveolar volume were below the comparison group of Michigan women only when tested at Washington DC.

Adult↗

PubMed1989

Body fat from body density: underwater weighing vs. dual-photon absorptiometry.

We measured fat in 286 healthy volunteers by underwater weighing (FUWW) and dual-photon absorptiometry (FDPA) to develop a translation table for the differing results from these entirely different techniques and to study the sources of these differences. In 99 males and 187 females aged 19-94 yr, fatness was 7-47%. Prediction equations are presented for FUWW-FDPA (delta F), density of lean body mass (DLBM), and FDPA. FUWW and FDPA were significantly different from each other (P less than 0.01). Calculated DLBM is less than the assumed constant of 1.10 (P less than 0.01), ranging widely from 1.05 to 1.13 and being highly correlated with the ratio of total body bone mineral to lean body mass (TBBM/LBM). delta F, the differences between FUWW and FDPA measurements in individual subjects, varied widely (-7 to +11% in males and -18 to +13% in females). The difference was positively correlated with the DLBM. FUWW was no better than anthropometrics in equations for predicting FDPA. The FDPA predicted from anthropometrics showed smaller standard errors than when FUWW was used. Neither anthropometrics nor FUWW equations are clearly superior to those previously available.

Adipose Tissue↗