Estimation Of Muscle Mass Research Articles

Validity of urinary urea nitrogen as a measure of total urinary nitrogen in adult patients requiring parenteral nutrition

The validity of the urinary urea nitrogen (UUN) estimate of total urinary nitrogen (TUN) was tested in patients who required iv nutrition. UUN and TUN were determined in 120 urine collections from ten preoperative, 13 postoperative, and 11 stressed patients. The relationship between TUN and UUN was examined by linear regression, and analysis of covariance was used on log-transformed data to assess differences between the patient groups. Although there was a close relationship between UUN and TUN for the preoperative patients (r2 = .94, total range of differences = 3.85 g N), this was not as accurate in postoperative and stressed patients (r2 = .69 and .76, respectively, total range of differences = 16.8 and 10.7 g N, respectively). There was no significant difference between the slopes of the regression lines for the relationship between UUN and TUN for three groups (f = 1.1, df = 2114, p less than .3), but the intercepts of the regression lines differed between the preoperative and stressed patient groups (t = 3.47, v = 114, p less than .001). The relationship between TUN and UUN for the whole group was improved by the inclusion of the independent variables of both the patient's clinical state and the urinary creatinine excretion. Arm muscle circumference, which is an estimate of muscle mass, may replace creatinine excretion with little loss in prediction accuracy.

Total-body electrical conductivity (TOBEC): relationship to estimates of muscle mass, fat-free weight, and lean body mass

A comparison of methods for estimating body composition (BC) of 12 subjects was made by using fat-free weight from total-body electrical conductivity (FFWT), muscle mass from 3-methylhistidine excretion (MM3MH) and creatinine excretion (MMCRE), fat-free weight from hydrostatic weighing (FFWBD), and lean body mass from whole-body potassium counting (LBMK). Data were analyzed for day-to-day variability and regression analyses were applied to compare the different methods of measuring BC. Mean values (+/- SEM, kg) for the estimates were 53.9 +/- 3.5 (FFWT), 26.9 +/- 2.9 (MM3MH), 25.3 +/- 2.5 (MMCRE), 53.2 +/- 3.6 (FFWBD), and 52.8 +/- 3.5 (LBMK). Regression analyses revealed that TOBEC estimates of fat-free weight had an adjusted r2 (+/- SEE, kg) of 0.95 +/- 2.2, 0.50 +/- 7.9, 0.95 +/- 1.8, and 0.88 +/- 4.0 for MM3MH, MMCRE, FFWBD, and LBMK, respectively. It was concluded that TOBEC is a potentially reliable method for estimating the muscle mass within the fat-free compartment, as well as fat-free weight and lean body mass.

Estimation of glomerular filtration rate in anorectic adolescents.

Severe malnutrition has been associated with a decrease in fat and lean body mass, as well as in renal function. This study was designed to evaluate the estimation of glomerular filtration rate (GFR, ml/min per 1.73 m2) in malnourished teenagers, by using the formula GFR = kL/Pcr (where L is body height, Pcr is plasma creatinine concentration and k is a proportionality constant relating muscle mass to body size that has been found to equal 0.7 in adolescent boys and 0.55 in girls). Body composition was estimated using anthropometric measurements and urinary creatinine excretion (UcrV). Malnourished female patients showed depletion of fat and muscle, whereas males had primarily decreased muscle mass. There was a good correlation (r = 0.74) between anthropometric [arm muscle volume (AMV)] and chemical UcrV estimates of muscle mass. However, our previously validated estimate of GFR did not give reliable results in this group of malnourished teenagers, probably because their muscle mass was so greatly altered by the severity of malnutrition. Therefore, we used anthropometric measurements and Pcr, to estimate GFR by multiple linear regression. The best prediction was obtained by using AMV/Pcr and the observed/expected (for age, height and sex) weight ratio (WR): GFR (ml/min) = 0.06 AMV/Pcr + 131 WR - 79, r = 0.82, n = 13. We confirm that malnutrition in adolescents is associated with decreased GFR and conclude that the resulting variability in body composition limits the possibility of estimating GFR from Pcr and height.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle mass as a factor limiting physical work.

Maximal exercise has been performed by eight men and eight women, using four types of ergometer (2-leg, 1-leg, arm + shoulder, and arm) while breathing room air and while breathing 12% O2. Results have been related to anthropometric estimates of muscle mass in the active limbs. Although significant sex differences of O2 transfer and power output are shown, the sex-specific aerobic performance was roughly proportional to active muscle volume (both when comparing individuals on a given type of ergometer and when comparing average scores of the several types of ergometer). However, the relationship was closer for steady power output than for peak O2 intake (where the scores for arm work were boosted by the use of accessory muscles and by hyperventilation). When breathing 12% O2, the 2-leg performance was substantially reduced (an average of 28.7% for O2 transport and 19.2% for power output). This effect dropped to 9.1% for O2 transport and 12% for power output in one-leg ergometry and was negligible for arm or arm plus shoulder work. It is argued that because of difficulty in perfusing small muscles, arm work is limited largely by the intrinsic power of the active muscles, that single-leg ergometry is limited rather equally by central circulatory and muscular factors, and that two-leg ergometry is almost entirely dependent on the central circulatory transport of O2.

Leucine incorporation into mixed skeletal muscle protein in humans.

Fractional mixed skeletal muscle protein synthesis (FMPS) was estimated in 10 postabsorptive healthy men by determining the increment in the abundance of [13C]-leucine in quadriceps muscle protein during an intravenous infusion of L-[1-13C]leucine. FMPS in our subjects was 0.046 +/- 0.003%/h. Whole-body muscle protein synthesis (MPS) was calculated based on the estimation of muscle mass from creatinine excretion and compared with whole-body protein synthesis (WBPS) calculated from the nonoxidative portion of leucine flux. A significant correlation (r2 = 0.73, P less than 0.05) was found between MPS (44.7 +/- 3.4 mg.kg-1.h-1) and WBPS (167.8 +/- 8.5 mg.kg-1.h-1). The contribution of MPS to WBPS was 27 +/- 1%, which is comparable to the reports in other species. Morphometric analyses of adjacent muscle samples in eight subjects demonstrated that the biopsy specimens consisted of 86.5 +/- 2% muscular as opposed to other tissues. Because fiber type composition varies between biopsies, we examined the relationship between proportions of each fiber type and FMPS. Variation in the composition of biopsies and in fiber-type proportion did not affect the estimation of muscle protein synthesis rate. We conclude that stable isotope techniques using serial needle biopsies permit the direct measurement of FMPS in humans and that this estimation is correlated with an indirect estimation of WBPS.

Effects of a beta-agonist (clenbuterol) on growth, carcass composition, protein and energy metabolism of veal calves.

Twenty-two British Friesian bull calves were used in a comparative slaughter experiment to determine the effects of a beta-agonist (clenbuterol) on body composition and energy retention. Four calves were slaughtered at 18 d of age and constituted the initial slaughter group. Of the remaining calves, eight (group A, controls) were given milk replacer only, and ten calves (groups B and C, five calves per group) were given milk replacer plus clenbuterol (0.1 and 1.0 mg clenbuterol/kg milk replacer equivalent to approximately 2 and 20 micrograms/kg body-weight respectively over the 105 +/- 3 d of the experimental period). Calves were slaughtered over the weight range 146-177 kg. Clenbuterol had no significant effect on dry matter (DM) intake, daily live-weight gain or feed conversion ratio. DM digestibility of the milk replacer was not affected by treatment. Nitrogen balance was measured on three separate occasions starting when the calves weighed approximately 60, 110 and 130 kg. N retention was increased over the experimental period in clenbuterol-treated calves, although the effect only achieved significance in calves weighing approximately 110 kg live weight (P less than 0.05). Clenbuterol (20 micrograms/kg body-weight) increased estimated mean daily N retention in the carcass of the calves from 22 to 25 g whilst N retention in the non-carcass components decreased from to 8 g/d. Effects of clenbuterol on N retention occurred mainly in skeletal muscle. Fat in both carcass and non-carcass components was reduced by treatment with clenbuterol. The total energy content of live-weight gain was reduced from 1077 to 897 MJ in clenbuterol-treated calves and mean daily heat production was estimated to increase from 23.1 in controls to 25.9 MJ/d in calves in group C. In calves of mean live weight during balance of 120 and 136 kg, clenbuterol significantly increased daily urinary creatinine excretion and in 120 kg calves N tau-methylhistidine was significantly decreased (P less than 0.05). Based on estimates of muscle mass from urinary creatinine and protein degradation from N tau-methylhistidine excretion, the fractional breakdown rate of muscle protein in clenbuterol-treated calves was only 0.66 of that in the controls when the calves weighed 120 kg.

Subtraction Gated Computed Tomography with the Dynamic Spatial Reconstructor

Three-dimensional (3-D) dynamic computed tomography of the heart with the dynamic spatial reconstructor (DSR) is being used for studies of cardiovascular function. Formerly, continuous infusion of bilateral bolus injections of contrast medium were required to visualize both sides of the heart simultaneously. The DSR was used to circumvent many of the drawbacks of these methods. In anesthetized dogs a bolus of 1 ml/kg body weight contrast medium was injected into the superior vena cava and 60/s scans were performed during the dextro- and levophases of the resulting angiogram. The recorded scan data were used to generate successive volume (3-D) images with a scan aperture time of 0.06 s each. Each scanned cardiac cycle was thus represented by sequential volume images with either the right or left chambers opacified. Matching equal time intervals from the R wave of the electrocardiogram, the volume images of the left heart phase were digitally subtracted (voxel for voxel) from the images of the right heart phase, with all resulting negative voxel values set to zero. Only the contrast enhanced right ventricle (RV) chamber remained in the subtraction images, whose brightness was then scaled to match the brightness of the opacified left ventricle (LV). The modified RV phase images were then added to the LV phase images. The resulting volume images contain equally enhanced LV and RV chambers and can be used for retrospective analysis, including display of static and dynamic oblique planar images. Verification of the accuracy of this technique was made by estimation of LV muscle mass in five dogs. Dynamic spatial reconstructor estimates from subtracted gated images were compared with postmortem measurements. The correlation was 0.999 with a mean discrepancy of 2.3 +/- 0.4% SEM.

The assessment of muscle mass in progressive neuromuscular disease.

We performed sequential studies of two methods used to estimate muscle mass in 34 patients with progressive neuromuscular disease for periods of up to 52 months. Creatinine excretion and total body potassium were low at the outset in virtually all patients. Creatinine excretion continued to decline in most patients, but total body potassium did not decline significantly. Creatinine excretion may measure declining muscle mass more accurately than total body potassium, but both measurements can estimate muscle mass for metabolic studies or therapeutic trials.

Total plasma creatinine: an accurate measure of total striated muscle mass.

Creatinine is a metabolite unique to striated muscle. Measurement of 24-h urinary creatinine excretion is an established method for estimating striated muscle mass. However, accurate assessment of urinary creatinine excretion is often impractical. We investigated the hypothesis that total plasma creatinine could be used instead of urinary creatinine excretion to estimate body composition. In 24 men, plasma volume and plasma creatinine concentration were measured, and total plasma creatinine was calculated as the product of these two measurements. Other measurements included urinary creatinine excretion, total body water, and anthropometry. Total plasma creatinine correlated strongly with urinary creatinine excretion (r = 0.82) and with weight, total body water, and anthropometrically estimated lean body mass. Muscle mass could be predicted by the equation: 0.88 x total plasma creatinine (mg). To verify this relationship, total plasma creatinine was prospectively measured in four dogs, then their total striated muscle was removed and weighed. Predicted muscle mass was within +/- 3.9% (range = 0.5-10.8%) of observed muscle mass. The ability to estimate muscle mass conveniently and accurately from total plasma creatinine should prove valuable for future studies in physiology and body composition.

Growth, fatness, and leanness in Mexican-American children

Height, weight, arm circumference and the triceps skinfold were measured in 1269 Mexican-American school children, 6 through 17 years of age, from Brownsville, Texas. Arm circumference was corrected for the triceps skinfold to estimate midarm muscularity and fatness. The triceps skinfold was also used to estimate the occurrence of obesity and leanness. The heights and weights of Brownsville Mexican-American children compare favorably to those for Mexican-Americans in the Texas phase of th Ten State Nutrition Survey, and approximate the 25th centile of the United States Health Examination Survey (HES) reference data. Estimated midarm fat areas for Mexican-American children are similar to or slightly below HES values, while estimated midarm muscle areas are consistently below HES medians. The differences in estimated muscle mass of the arm reflect in part the smaller body size of Mexican-American children, and perhaps their diet, which tends to be adequate in calories and less satisfactory in protein. About 5 to 7% of the Mexican-American children are classified as "obese" using HES and TEcumseh (Michigan) criteria, both sets of reference data giving comparable results except in boys 14 to 17 years. However, about 30% of the Mexican-American children are classified as "lean" by the Tecumseh criteria and only 3% by the HES criteria. Estimates of obesity and leanness in a population thus vary with the criteria used.

Whole body protein turnover in aging man

To explore the effects of aging on dynamic aspects of whole body protein metabolism in man, the 15N-glycine infusion method of Picou and Taylor-Roberts was used to estimate rates of total body protein synthesis and breakdown in both young adults and elderly subjects. Nine healthy elderly subjects, 4 male and 5 female, 65–91 yr old, participated in the study. Results obtained with 4 young men and 4 young women, 18–25 yr old, were used for comparative purposes. Total body protein synthesis and breakdown rates, per day and per unit body weight per day, were lower in women than in men and significantly lower in elderly women than in young women. Urinary creatinine was used to estimate muscle mass, and whole body 40K to calculate body cell mass. Whole body protein synthesis and breakdown rates, per unit creatinine, were higher in the elderly than in the young adults. Expressed per unit body cell mass, the rates were higher in elderly men than in young men, and a similar, but not statistically significant, difference was observed between elderly and young women. From these results it appears that whole body protein synthesis declines with age in man and is associated with the loss of body cell mass. There is also a redistribution in the pattern of whole body protein synthesis and breakdown as aging progresses, with the visceral organs making a progressively greater contribution to whole body protein metabolism than the skeletal musculature.

Evaluation of muscle mass measurement by 14C-creatine dilution in the dog

Dogs were given a tracer dose of 14C-creatine. A substantial fraction of the administered radioactivity is excreted in urine (27.5% in 5 days, 67% in 17 days); residual activity is concentrated in skeletal and smooth muscle (3–6% in other major viscera). However, tissue radioactivity of muscle tissue, when referred to weight, potassium, or nitrogen is not uniform, and no reasonable estimate of muscle mass can be made from a single biopsy specimen in this species.

Human power output in exercise of short duration in relation to body size and composition.

Abstract Maximum power output during the performance of a standing jump of two feet from a force platform and stair climbing has been studied in 47 male subjects aged 20-50 years and 8 female subjects aged 18-27 years in relation to body composition. During the standing jump, power output mean values of 5·23 hp for men and 3·15 hp for women wore recorded. These figures are amongst the highest over recorded in man; they ore some four times higher than the corresponding values for the stair climb and fifteen times those achieved during maximum aerobic work on a stationary bicycle ergometer. Maximum power output in the two forms of activity were dependent on ago and sex, size, stature and, to a lesser extent, body composition of the subject. In young men and women the power output values were related to estimates (from soft tissue radiographs) of thigh muscle and loan body mass. However, in older subjects these relationships disappeared. Power output values during stair climbing could be accounted for in ter...

Muscle mass determination by isotopic dilution of creatine- 14C

Because of the localization of creatine in muscle, the feasibility of using isotopic dilution of 14C-creatine to estimate muscle mass in vivo was investigated. Rats were sacrificed at daily intervals following the administration of 1–2 μc. of 1- 14C-creatine I.V. Urine and stool were the major routes of 14C excretion. 14C calculated to be remaining in the body (“ 14C injected minus 14C excreted”) was 100 ± 2 per cent of that found by carcass analysis. By 144 hours, 94 per cent of body 14C was in carcass muscle, 4 per cent in skin and 2 per cent in gut, kidney and liver. Although not all 14C was in muscle, the discrepancy was accepted since only a 6–7 per cent overestimate of muscle mass could be introduced. The mean 14C concentration in four muscle pieces was considered to be representative of the concentration in the muscle compartment. Paired comparison revealed that there was no significant difference between muscle mass values determined by isotopic dilution ( 14C remaining in the body divided by 14C/Gm. fat free muscle) and the anatomic muscle mass (obtained by dissection) in 24 rats weighing 200–400 Gm. These results indicate that dilution of 14C-creatine can be used to measure muscle mass in vivo in rats and suggest that with appropriate modification this method may be applicable to man and other large animals.

Symposium on Atomic Energy in Animal Science. II. Estimation of Carcass Lean Muscle Mass in Steers By K40 Measurement

Symposium on Atomic Energy in Animal Science. II. Estimation of Carcass Lean Muscle Mass in Steers By K40 Measurement

TOTAL BODY WATER AND SOLIDS IN SIX- TO SEVEN-YEAR-OLD CHILDREN: DIFFERENCES BETWEEN THE SEXES

Total body water of the boys in this study was higher by 1.63 1 and by 3.75% than total water, expressed either in absolute or relative values, of the girls. These mean differences between the sexes were significant. The absolute quantity of body solids was higher in the girls by 0.44 kg. This difference was statistically insignificant. However, body solids expressed as a percentage of body weight were found to be higher by 3.75% in the girls, a difference which was statistically significant. The relative estimate of fatness by five skinfold measurements revealed all the skinfolds to be smaller in the boys. In particular, the upper arm and the thigh skinfolds were smaller in the boys to a statistically significant extent. The relative estimate of muscle mass made from the three calculated diameters showed that the boys had slightly greater musculature on their limbs. However, none of these differences proved to be statistically significant.