PubMed Health⌕ Search

Biomedical subjects

H C Lukaski

Publications and source records attributed to H C Lukaski.

71 records · Page 4Linked to original sources
PubMed1984

Increased cholesterol in plasma in a young man during experimental copper depletion.

Signs of copper depletion were produced in a healthy man by an amount of dietary copper (0.83 mg/day) similar to that in some contemporary diets. Urinary and fecal loss of copper exceeded intake. Plasma copper, ceruloplasmin, and superoxide dismutase activity in erythrocytes decreased. Cholesterol in plasma increased, and hematologic indices were unchanged. Lipid metabolism may be a more sensitive index of copper nutriture than are changes in hematology. The findings support the hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease.

Adult↗
PubMed1984

Influence of type and amount of dietary lipid on plasma lipid concentrations in endurance athletes.

Changes in plasma total cholesterol, triglyceride, and lipoprotein concentrations were assessed in three male endurance cyclists who consumed isoenergetic diets for 28-day periods in which carbohydrate, polyunsaturated fat, or saturated fat contributed about 50% of the daily energy intake. Dietary cholesterol was similar among the diets. Maximal aerobic capacity was maintained at 62 ml O2/(kg X min). Body weights were held within 3% of admission levels. The polyunsaturated fat diet significantly (p less than 0.05) reduced mean fasting plasma total cholesterol in comparison to the saturated fat and carbohydrate diets (160 versus 254 and 243 mg/dl, respectively). Similarly, the polyunsaturated fat diet depressed (p less than 0.05) mean plasma triglycerides relative to the saturated fat and carbohydrate diets (37 versus 62 and 79 mg/dl, respectively). No significant dietary effects were seen on high-density lipoprotein cholesterol. The observed changes in plasma total cholesterol were not significantly different than the values predicted by the Keys' equation, delta CHL = 1.35(2 delta S-delta P) + 1.5 delta Z. We conclude that under controlled conditions in which physical activity is constant l) dietary lipid differences influence fasting serum lipid and lipoprotein concentrations among men with high energy expenditures, and 2) the Keys' equation gives useful predictions of changes in plasma total cholesterol among vigorous men consuming different types and amounts of dietary lipid.

Adult↗
PubMed1984

Fat-free mass as a function of maximal oxygen consumption and 24-hour urinary creatinine, and 3-methylhistidine excretion.

The relationships between maximal oxygen consumption (VO2max) with fat-free mass (FFM), and with 24-h urinary excretion of 3-methylhistidine (3MH) and creatinine (Cr), were studied in 12 active men age 31.4 +/- 9 yr (mean +/- SD). FFM, VO2max and VO2maxWt-1 were 50.9 +/- 9.1 kg, 3.8 +/- 0.9 L X min-1, and 54.8 +/- 9.4 ml X kg-1 X min-1, respectively. Urinary 3MH and Cr after 3 days on a meat-free diet were 213.9 +/- 30.8 mumol X day-1 and 1.60 +/- 0.3 g X day-1, respectively. 3MH X Cr-1 was 135.3 +/- 16.8 mumol X g-1 or 15.3 +/- 1.9 molar ratio X 10(3). The strongest (p less than 0.01) associations found were 3MH versus FFM, FFM versus VO2max, and 3MH versus VO2max. Other significant (p less than 0.05) relationships were Cr versus FFM, Cr versus 3MH, and Cr versus VO2max. Nonsignificant correlations were found for 3MH X Cr-1 versus VO2max X kg-1 X min-1 versus FFM, 3MH X Cr-1 versus VO2max, and FFM versus VO2max X kg-1 X min-1. The best predictor of FFM was 3MH. It was concluded that endogenous urinary 3MH excretion is a valid method to study human body composition and that 3MH is more closely related to FFM (r = 0.93) than VO2max (r = 0.78).

Adult↗
PubMed1984

Changes in plasma zinc content after exercise in men fed a low-zinc diet.

For 30 days five healthy men aged 23-57 yr consumed a diet adequate in zinc (8.6 mg/day); they ate a low-zinc diet (3.6 mg/day) for the next 120 days and then received a zinc-supplemented (33.6 mg/day) diet for 30 days. Copper intake was constant at 1.8 mg/day. Aerobic capacity was determined periodically during each diet period. Relative zinc balance (% of control) declined during depletion (r = -0.28, P less than 0.009). Pre- and postexercise zinc concentrations decreased when dietary zinc was restricted (r = -0.61, P less than 0.0001 and r = -0.78, P less than 0.0001) and increased with supplementation (r = 0.61, P less than 0.008 and r = 0.76, P less than 0.0003, respectively). Both plasma zinc and hematocrit increased (P less than 0.01) after maximal exercise. To minimize the effect of hemoconcentration during exercise, the van Beaumont quotient (J. Appl. Physiol. 34: 102-106, 1973) was calculated using pre- and postexercise hematocrit and plasma zinc. The initial quotient of 1.8 +/- 1.8% (mean +/- SE) declined (P less than 0.05) to -7.4 +/- 2.3% during depletion. With zinc repletion, the quotient increased to 6.9 +/- 3.6%, which was greater (P less than 0.05) than the quotient in depletion but similar to the initial quotient. The quotient was a strong predictor (r = 0.71, P less than 0.0005) of the change in relative zinc balance during zinc depletion. In contrast, no changes were found in plasma copper content. These data suggest that zinc mobilization from tissues is impaired during zinc depletion, and they validate the use of the van Beaumont quotient as an index of change in body zinc stores.

Adult↗
PubMed1983

Maximal oxygen consumption as related to magnesium, copper, and zinc nutriture.

Forty-four healthy male university athletes and 20 untrained men underwent maximal treadmill exercise testing to determine the relationship between maximal oxygen consumption and various measurements of elemental nutriture. Hb and mean plasma and erythrocyte concentrations of magnesium, copper, and zinc were within established norms for both groups after a 12-h fast. Mean plasma copper concentration was significantly (p less than 0.01) higher in the athletes (90 +/- 14.3 versus 81 +/- 8.0 micrograms/dl). Average maximal oxygen consumption also was significantly (p less than 0.001) higher in the athletes [4.5 +/- 0.5 versus 3.3 +/- 0.6 L/min and 55.5 +/- 7.1 versus 47.0 +/- 6.0 ml/(kg x min)]. Plasma magnesium was significantly correlated (r = 0.46; p less than 0.002) with maximal oxygen consumption, ml/(kg x min), among the athletes. This relationship persisted when the effect of Hb concentration was removed by covariance analysis (p less than 0.005). Only a weak association (r = -0.32; p = 0.17) was found between oxygen consumption and plasma magnesium in the untrained men. We hypothesize that ionic magnesium may facilitate oxygen delivery to working muscle tissue in trained subjects.

Adult↗
PubMed1983

Potential errors in body composition as estimated by whole body scintillation counting.

Vigorous exercise has been reported to increase the apparent potassium content of athletes measured by whole body gamma ray scintillation counting of 40K. The possibility that this phenomenon is an artifact was evaluated in three cyclists and one nonathlete after exercise on the road (cyclists) or in a room with a source of radon and radon progeny (nonathlete). The apparent 40K content of the thighs of the athletes and whole body of the nonathlete increased after exercise. Counts were also increased in both windows detecting 214Bi, a progeny of radon. 40K and 214Bi counts were highly correlated (r = 0.87, p less than 0.001). The apparent increase in 40K was accounted for by an increase in counts associated with the 1.764 MeV gamma ray emissions from 214Bi. Thus a failure to correct for radon progeny would cause a significant error in the estimate of lean body mass by 40K counting.

Adolescent↗
PubMed1981

A comparison of methods of assessment of body composition including neutron activation analysis of total body nitrogen.

Fourteen healthy men underwent determinations of total body nitrogen (TBN) by prompt gamma neutron activation analysis and total body potassium (TBK) by whole body counting to estimate the muscle and nonmuscle components of the fat-free body mass (FFBM) and their protein contents. Comparison of FFBM estimated from TBN and TBK (60.6 +/- 6.9 kg, mean +/- SD), densitometry (62.3 +/- 7.1 kg), TBK alone (62.2 +/- 8.0 kg) and TBW (63.9 +/- 7.8 kg) showed no differences among the techniques. Similarly, there were neither differences in fat mass nor percent body fat among the methods. Analysis of the chemical composition of FFBM of this group showed TBK/FFBM = 62.6 +/- 2.3 mEq/kg, TBW/FFBM = 74.6 +/- 0.2%, TBN/FFBM = 32.74 +/- 1.09 g/kg, protein/FFBM = 20.5+/- 0.7%. The calculated mineral content of the FFBM was 6.4%. These values are strikingly similar to the values calculated by direct chemical analysis. It was concluded that the combined TBN-TBK method is a valid technique for estimating body composition in man.

Adipose Tissue↗
PubMed1981

Variability of body density in ambulatory subjects measured at different days.

The variability of weight in air and underwater, residual lung volume and body density was studied in ambulatory men who were advised to maintain a constant diet and level of physical activity for four days (group I) and 60 days (group II). It was assumed that data obtained from group I which included volunteers familiar with the densitometric procedure would yield more reliable information than from group II which consisted of inexperienced subjects. Weight underwater and residual lung volume were the most variable measurements. The precision in body density varied from 0.0008 to 0.0018 g.ml-1, equivalent to 0.32 and 0.73% body fat in groups I and II, respectively. The data suggest that familiarity with the technique did not influence the reliability of body density measurement. Body composition as indicated by body density appears to remain constant over relatively long periods during which diet and levels of physical activity are controlled.

Adult↗
PubMed1981

Relationship between endogenous 3-methylhistidine excretion and body composition.

Fourteen healthy men (aged 20-30 yr) consumed two isocaloric, isonitrogenous diets in the sequence of a 4-day meat diet (MD) followed by a 7-day meal-free diet (MFD). Urinary 3-methylhistidine (3MH) excretion during the MD (513 +/- 21 mumol . day-1, mean +/- SE) was significantly higher (P less than 0.01) than day 3 of the MFD (230 +/- 10 mumol . day-1), after which the mean daily 3MH output was constant with a mean coefficient of variation of 4.5%. There was no change in fat-free body mass (FFBM) determined by densitometry at the start (62.3 +/- 1.8 kg) and the end (62.2 +/- 1.9 kg) of the 11-day dietary period. Mean muscle mass (MM) calculated from measurements of total-body potassium and nitrogen was 23.4 +/- 1.3 kg. Endogenous 3MH excretion was related more closely to MM (r = 0.91, P less than 0.001) than to FFBM measured by densitometry (r = 0.81, P less than 0.001). Only a low correlation coefficient (r = 0.33, P less than 0.05) was observed between 3MH and the nonmuscle component of FFBM. Urinary creatinine output also was correlated significantly with 3MH (r = 0.87; P less than 0.001) and MM (r = 0.79; P less than 0.01). It is concluded that because endogenous 3MH is significantly related to MM in man, it can be used as a marker to study in vivo total-body muscle protein degradation provided that the necessary dietary restrictions are observed.

Adult↗
PubMedDate not supplied

Processing of TRH precursor peptides in rat brain and pituitary is zinc dependent.

The enzymes responsible for the posttranslational processing of precursor proteins to form alpha-amidated peptide hormones require the availability of several cofactors, including zinc, copper and ascorbate ions. Major changes in the availability of these cofactors, as well as the rate of hormone precursor conversion to active hormone, occur during neonatal development, aging and caloric restriction. The effects of 6 weeks of a zinc-deficient (ZD1) diet, pair feeding (PF) and partial zinc deficiency (ZD6) compared to a control diet on the enzymatic cleavage and processing of prepro-TRH to form TRH have been studied in the hypothalamus, brain, and pituitary of young adult male Sprague-Dawley rats. Reverse phase high pressure liquid chromatography (HPLC) revealed that TRH was the major TRH-IR component of the hypothalamus, brain and pituitary. The effect of zinc deficiency on the TRH-Gly-IR HPLC profile of rat brain was to reduce selectively the are of the peaks for TRH-Gly and other low molecular weight pro-TRH peptide fragments with a C-terminal Gly compared to the corresponding TRH-Gly-IR peaks of the control group. We conclude that the processing of prepro-TRH to form TRH is zinc dependent via posttranslational processing enzymes such as carboxypeptidase H.

Amino Acid Sequence↗
PubMedDate not supplied

Testosterone increases TRH biosynthesis in epididymis but not heart of zinc-deficient rats.

Enzymes responsible for the posttranslational processing of precursor proteins to form alpha-amidated peptide hormones require the availability of several cofactors, including zinc, copper, and ascorbic acid. For this reason, we studied the effects of 6 weeks of a zinc-deficient diet (ZD1; 1 microgram zinc per g diet), pair-feeding (PF), and marginal zinc deficiency (ZD6; 6 micrograms zinc per g diet) compared to a control diet (36 micrograms/g zinc) on the conversion of prepro-TRH to TRH in epididymides, testes, prostate, pancreas, and heart of young adult, male Sprague-Dawley rats. In the epididymis, severe zinc deficiency (ZD1 diet) reduced TRH and TRH-like peptides to undetectable levels. In ZD6 animals, TRH was selectively inhibited 80%, while pair-feeding increased all of these peptide levels compared to controls. A similar effect of zinc deficiency on the TRH precursor peptides was observed. A quantitative loss of TRH from the testes of ZD1 was also observed. Zinc deficiency results in a substantial reduction in body weight and testosterone production in male rats. Exogenous testosterone (T) supplementation of ZD1 rats resulted in a selective increase in the TRH concentration of the epididymis but not of the heart. The change in steady-state levels of TRH precursor peptides in the hearts of the ZD1+T rats was consistent with a reduction in the activity of the zinc-dependent carboxypeptidase H enzyme. We conclude that severe zinc deficiency inhibits TRH biosynthesis in reproductive tissues of the male rat due to the combined effects of hypogonadism and inhibition of the zinc-dependent carboxypeptidase H.

Amino Acid Sequence↗
PubMedDate not supplied

Validation of dual x-ray absorptiometry for body-composition assessment of rats exposed to dietary stressors.

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure soft-tissue composition of laboratory rats with altered body composition associated with nutritional perturbations is lacking. We compared DXA determinations made in prone and supine positions with measurements of chemical composition of 49 male, weanling Sprague-Dawley rats that were fed the basal AIN-93 growth diet, were fed the basal diet modified to contain 30% fat, were fasted for 2 d, were limit fed 6 g of the basal diet daily for 1 wk, or were treated with furosemide (10 mg/kg intraperitoneally 2 h before DXA). DXA produced similar estimates of body mass and soft-tissue composition in the prone and supine positions. DXA estimates of body composition were significantly correlated with reference composition values (R(2) = 0.371-0.999). DXA discriminated treatment effects on body mass, fat-free and bone-free mass, fat mass, and body fatness; it significantly underestimated body mass (1% to 2%) and fat-free and bone-free mass (3%) and significantly overestimated fat mass and body fatness (3% to 25%). The greatest errors occurred in treatment groups in which body mass was diminished and body hydration was decreased. These findings suggest that DXA can determine small changes in fat-free, bone-free mass in response to obesity and weight loss. Errors in DXA determination of fat mass and body fatness associated with extra corporeal fluid and dehydration indicate the need for revision of calculation algorithms for soft-tissue determination.

Absorptiometry, Photon↗
PubMedDate not supplied

Bioelectrical impedance methods in clinical research: a follow-up to the NIH Technology Assessment Conference.

In 1994, the National Institutes of Health (NIH) convened a Technology Assessment Conference "to provide physicians with a responsible assessment of bioelectrical impedance analysis (BIA) technology for body composition measurement." In 1997, Serono Symposia USA, Inc., organized an invited panel of scientists and clinicians, with extensive research and clinical experience with BIA, to provide an update. Panel members presented reviews based on their own work and published studies for the intervening years. Updates were provided on the single and multifrequency BIA methods and models; continued clinical research experiences; efforts toward establishing population reference norms; and the feasibility of establishing guidelines for potential diagnostic use of BIA in a clinical setting. This report provides a summary of the panel's findings including a consensus on several technical and clinical issues related to the research use of BIA, and those areas that are still in need of additional study.

Body Composition↗
PubMedDate not supplied

Densitometry-based equations for estimating body composition in Fischer rats.

Male Fischer rats are widely used to evaluate the effects of nutritional repletion or deprivation on the rat's nutritional status. Practical methods are needed to evaluate changes in body composition. Chemical analysis is expensive, time consuming, and often not available; bioelectrical impedance analysis in laboratory animals lacks standardization. Postulating that the measurement of densitometry would allow reliable estimation of body composition in the male Fischer rat, we studied 27 male Fischer rats. Densitometric measurements of the carcasses and their chemical analysis were performed to obtain reference values. Initial estimation of the fraction of body fat based on densitometry was attempted with the Siri equation intended for use in humans. We found that this equation was not suitable for use in the male Fischer rat because it underestimated fat mass at high carcass weights and overestimated fat mass at low carcass weights. Therefore, the Siri equation was modified to more accurately predict carcass composition in the male Fischer rat. Three different predictive equations based on simple densitometric measurements were developed that allow separate estimation of carcass fat, carcass water, and carcass protein in the male Fischer rat. These equations were found to be accurate to within 2-5-3% of carcass weight.

Adipose Tissue↗
PubMedDate not supplied

Validation of body composition assessment techniques in the dialysis population.

Assessment of body composition remains a goal for the routine assessment of nutritional status of patients on long-term dialysis. Methods generally available for estimation of body fat in healthy individuals are limited by practicality and availability for use in this patient population. Anthropometry, which is cost effective and easy to perform, is limited by the lack of appropriate reference standards for patients on dialysis and artifact caused by hydration status. Bioelectrical impedance affords new opportunities for non-invasive assessment of fluid volume, its distribution, and body cell mass; estimation of fat-free mass and body fat can be affected by hydration status. Dual x-ray absorptiometry permits estimation of bone status and fat mass because changes in hydration status are reflected in estimates of fat-free mass. Evaluation of validity of techniques for fluid status and body composition assessment requires the use of appropriate reference methods and proper statistical procedures to examine error, not only between groups, but by individual. Use of body composition assessment methods together with biochemical measurements will enhance the nutritional assessment of end-stage renal disease patients on long-term hemodialysis.

Absorptiometry, Photon↗