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Biomedical subjects

M Barac-Nieto

Publications and source records attributed to M Barac-Nieto.

At least 55 records · Page 3Linked to original sources
PubMed1983

Marginal malnutrition in school-aged Colombian boys: anthropometry and maturation.

Colombian reference data for weight and height were used to classify 1108 boys 6 to 16 yr old as nutritionally normal, low weight for age, and low weight for height. The normal group in upper socioeconomic urban and normal, low weight for age, low weight for height groups in lower socioeconomic urban and rural populations were studied. The achieved growth, growth velocities, skinfolds, mid-arm and head circumferences, and sexual maturation were all depressed in the nutritionally deprived groups indicating marginal malnutrition. Since normal boys exist in low socioeconomic and rural populations, normative data for economically advantaged children (national standards), on the average, may serve as desirable goals for low socioeconomic and rural populations. Different cutoff points for achieved growth might be established for marginal malnutrition using national or international reference populations. These ought to be age-related because of accumulated effect of slowed growth with age. Head circumference of school-aged children may proved a useful anthropometric tool in deciding early nutritional history.

Adolescent↗
PubMed1983

Marginal malnutrition in school-aged Colombian boys: functional consequences in maximum exercise.

The maximum treadmill oxygen consumption was measured in 1013 boys, 6 to 16 yr of age classified as nutritionally normal, low weight for age and low weight for height in upper socioeconomic urban and lower socioeconomic urban and rural groups. The marginally malnourished children (low weight for age and height) in both lower socioeconomic urban and rural groups had significantly depressed maximum treadmill oxygen consumption (85%) compared to normal boys, associated with smaller body weights. It is suggested that the reduced body size and maximum treadmill oxygen consumption resulting from marginal malnutrition during growth will have a detrimental effect on work capacity and productivity of these children when they become engaged in heavy physical work as adults. There was no statistically significant correlation between blood Hb concentration (approximately 10 to 15 g x dl-1) and aerobic capacity.

Adolescent↗
PubMed1982

Asymmetry in the transport of lactate by basolateral and brush border membranes of rat kidney cortex.

The uptake of L(+)lactate into rat renal cortical brush border (BBV) and basolateral (BLV) membrane vesicles, isolated through differential centrifugation and free flow electrophoresis, were studied using a rapid filtration technique. In contrast to the lactate transport into the BBV, that into the BLV: 1) was found to proceed only towards equilibrium, 2) showed Na+ -independent coupling of the influx of L(+)lactate and the efflux of L(+) but not to the efflux of D(-)lactate, 3) was not inhibited by D(-)lactate, 2-thiolactate or 3-phenyl-lactate, but 4) was inhibited by 3-thiolactate and alpha-hydroxybutyrate and 5) was accelerated by changes in inwardly directed ionic gradients or by increases in cation conductance both of which led to increased intravesicular positivity. The latter changes had the opposite effect on the uptake of L(+)lactate by BBV. Thus, while the L(+)lactate transport system present in BBV showed the characteristics of Na-dependent electrogenic cotransport system, that in the BLV was consistent with a carrier mediated Na-dependent, facilitated diffusion system.

Animals↗
PubMed1981

Comparisons of body fat estimated from total body water and skinfold thicknesses of undernourished men.

In 49 chronically undernourished adult males, classified as having mild, intermediate, or severe nutritional compromise, comparisons were made of body fat calculated from total body water with values obtained from triceps and scapular skinfolds. These same comparisons were followed in 19 of the severely undernourished subjects during a 2 1/2-month period of dietary repletion. Results indicate that the correlations between fat estimates obtained from body water and skinfolds are good (r greater than 0.8) in mildly undernourished subjects, but that they are progressively reduced as the nutritional compromise becomes more severe until statistical significance disappears. Dietary repletion of 2 1/2-month duration did not restore a statistically significant relationship between fat and triceps and scapular skinfolds. These data imply that the triceps and scapular skinfolds do not adequately represent body fat in chronically undernourished adult males and that new empirical equations are required which take into account nutritional status and possible shifts in fat deposit sites in chronic undernutrition.

Adult↗
PubMed1980

Sodium ion/L-lactate co-transport in rabbit small-intestinal brush-border-membrane vesicles.

Uptake of L-lactate into rabbit jejunal brush-border-membrane vesicles prepared by a Ca2+-precipitation procedure was studied by a rapid filtration technique with L-[14C]-lactate as tracer. Transport of L-lactate into an intravesicular (osmotically reactive) space could be established. An inwardly directed NaCl gradient (outside 21 mM/inside 0mM) stimulated the uptake of L-lactate at 15 s 2-4-fold compared with that observed with an equal KCl gradient. A transient accumulation of L-lactate inside the vesicles (overshoot) was observed in the presence of an NaCl gradient. Gradients of LiCl, RbCl, CsCl or choline chloride were not able to replace NaCl in the stimulation of L-lactate uptake. L-Lactate uptake was saturable only in the presence of Na+. D-Lactate, DL-thiolactate (2-DL-mercaptopropionate), pyruvate and propionate inhibited the Na+-stimulated L-lactate uptake; D-lactate, thiolactate and pyruvate provoked trans-stimulation of L-lactate uptake. Artificially imposed diffusion potentials (inside negative) did not exert any effect on the Na+-dependent L-lactate uptake. The results are consistent with the existence of an electroneutral Na+/L-lactate co-transport system in the brush border of rabbit small intestine.

Animals↗
PubMed1980

Aerobic work capacity and endurance during nutritional repletion of severely undernourished men.

Oxygen consumption in maximal exercise (VO2max) was found to increase during nutritional rehabilitation of severely undernourished, sedentary adult males only when dietary protein was increased from 27 to 100 g/day. Adequate caloric intake, maintained for 45 days before the increase in protein content of the diet, had no effect on VO2max. The VO2max values were found to correlate best with the creatinine excretion rates (an index of the muscle cell mass) at the different stages of repletion. The average increment in VO2max/muscle cell mass ratio, although significant, was of a small magnitude (+15%). The VO2max/muscle cell mass ratio correlated only with the blood and plasma volumes at the different stages of repletion. After 2.5 months of protein repletion the VO2max values were still lower than those in mildly undernourished or normal Colombian adult males. Maximal endurance time at 80% aerobic load decreased significantly from an average of 113 min at the beginning of hospitalization to 42 min at the end of the period of protein repletion. This could be the result of replacing carbohydrate calories with protein in the diet, producing depletion of muscle glycogen stores, and/or to "detraining" effects associated with sedentary hospital life.

Adult↗
PubMed1980

Lactate-sodium cotransport in rat renal brush border membranes.

Brush border membrane vesicles were obtained from rat kidney cortex through a calcium precipitation method and their transport properties for lactate were studied by a rapid-filtration technique. Transient concentrative uptake of L-lactate was observed in the presence of inwardly directed NaCl gradient, but not in the presence of a KCl, LiCl, RbCl, CsCl, or choline chloride gradient. The sodium-dependent L-lactate uptake was saturable and was inhibited by D-lactate. The activation curve with sodium was hyperbolic. Maneuvers that render the inside of the vesicle more negative stimulated sodium-dependent L-lactate uptake, suggesting an electrogenic transfer of L-lactate and sodium. An L-lactate gradient also accelerates the sodium movement across the brush border membrane. Studies on the pH dependency of L-lactate transport and on the effect of L-lactate on proton movements across the brush border membrane indicate that there is little contribution of nonionic diffusion and/or of lactate-H+ cotransport to the transfer of L-lactate across the renal brush border membrane. In summary, sodium-lactate cotransport is the major mechanism for L-lactate transfer across the renal brush border membrane.

Animals↗
PubMed1979

Functional assessment of nutritional status: heart rate response to submaximal work.

The heart rate response to submaximal treadmill work been calculated using the heart rates and oxygen intakes obtained from normally nourished and undernourished adult male subjects during a maximal oxygen consumption test. Increased severity of malnutrition was associated with an increased heart rate response to the same submaximal work loads. The response was observed to decrease during a period of high protein dietary repletion of the most severely malnourished subjects. The data suggest the possibility of developing a submaximal work test for use in the field to provide physiological data to supplement anthropometric and biochemical information used to assess the nutritional status of populations.

Adolescent↗
PubMed1979

Body composition during nutritional repletion of severely undernourished men.

Body composition was studied in severely undernourished adult male inhabitants of a rural area of Colombia to evaluate the extent and the time course of the changes occurring upon nutritional repletion. During a 45-day basal period on a low (26g/day) protein diet containing adequate calories, body fat depots increased significantly (mean +/- SD = +3.02 +/- 2.9 kg), and there was a significant decrease in cell hydration from 81.8 to 76.4% (-5.4 +/- 9.1%). Upon protein repletion (100 g/day), cell hydration decreased significantly to 71.4%, while body cell mass increased markedly (9.0 +/- 1.1 kg). During protein repletion, muscle cell mass increased significantly (+5.5 +/- 0.6 kg) and rapidly, while the increase in nonmuscle cells (+3.5 +/- 3.8 kg) and specifically in red cell mass lagged behind. With repletion, the changes in the absolute values for plasma volume (+0.4 +/- 0.13 liters) were significant, but those in extracellular fluid volume (-0.7 +/- 1.9 liters) were not. Thus, the major compositional changes observed occurred in the body fat and the body cell mass components; these occurred independently of each other.

Adipose Tissue↗
PubMed1978

Body composition in chronic undernutrition.

Anthropometric (height, weight, and skinfolds), biochemical (serum proteins, albumin, and cholesterol), metabolic (nitrogen balance and creatinine excretion), hematological (plasma volume, hemoglobin, hematocrit, bone marrow hemosiderin, percent transferrin saturation, vitamin B12, and folic acid) variables and body water compartments (total and extracellular) have been measured in 49 adult male subjects who exhibited a wide range of nutritional states from normal to severely undernourished. Changes in body composition associated with moderate degrees of nutritional compromise were related principally to decreases in body cell mass (-15%). Body fat was normal. With severe nutritional involvement, both fat depots (-29%) and body cell mass (-29%) were significantly diminished. Muscle cell mass was more affected than other cells in the body (-41%). These data could indicate that in the group with moderate compromise, energy reserves (and hence energy balance) were maintained but dietary protein deficiencies were not compensated for. Both calorie and protein deficiencies were evident in the subjects with severe undernutrition. Multiple regression equations (r greater than 0.8) were developed that allow prediction of muscle cell mass, fat-free weight, and body cell mass from simple anthropometry and serum albumin levels. Decreases in serum albumin concentration were best related to deficits in muscle mass (r = 0.77).

Adolescent↗
PubMed1978

Aerobic work capacity in chronically undernourished adult males.

Maximal O2 consumption (VO2max) and maximal endurance time at 80% Vo2max (T80) were determined in 49 subjects with varying degrees of nutritional compromise. Vo2max was lover by 21% and 52% in subjects with moderate and severe undernutrition, respectively, when compared to men with mild nutritional compromise. Most (80%) of the change in Vo2max could be related to the estimated differences in muscle cell mass (MCM). A significant reduction (-18%) in the Vo2max per unit of MCM was found in the severely undernourished subjects, indicating basic physiological changes. Total body hemoglobin showed the highest correlation with Vo2max (r = 0.709) and at constant MCM (partial r = 0.796). A multiple regression equation was derived to estimate the Vo2max of populations on the basis of simple anthropometry and blood hemoglobin levels. T80 (93-103 min) and estimated maximum sustained 8-h percent effort (32%) in mild, intermediate, or severe undernutrition were not significantly different; by contrast, endurance at a given absolute work load was markedly lower in severe undernutrition (8 vs. 1.5 h) due presumably to the difference in Vo2max.

Adipose Tissue↗
PubMed1978

[Effect of mannitol on oxygen consumption of the renal cortex of rats].

We have determined the oxygen consumption (QO2) in renal cortical tissue from controls and from rats which received in vivo and infusion of mannitol (600 mM) in order to study the metabolic changes which occurred in the tissue. QO2 was significantly higher (+20%, p less than 0.01) in slices from animals which received the infusion than in those from non-infused animals, when incubated in mannitol containing solutions; these slices had tubules with their lumens open. When the slices were incubated in solutions without mannitol or obtained from animals not infused with mannitol, the QO2 was lower and the tubules appeared histologically with the lumen closed. A short (2 min) exposure to 2 mM ethacrinic acid inhibited QO2 only in slices from mannitol infused animals incubated in mannitol containing solutions. Similar exposures to 1 mM ouabain inhibited QO2 both in slices from infused and from non-infused animals and independently of the composition of the incubation media. We suggest that the higher QO2 found in those slices which had their tubular lumens open, as well as the specific inhibitory effect of ethacrinic acid on the excess QO2 of such slices, might relate to transport processes, linked to tissue metabolism, and only present in tubules which have their lumens open. Such active transport process may correspond, for example, to the coupled transcellular Na+ and Cl- transport. The effects of mannitol on the tissue water content is discussed.

Animals↗
PubMed1977

Energy expenditure, productivity, and physical work capacity of sugarcane loaders.

VO2, E and heart rates (fH) were measured in 28 Colombian sugarcane loaders while loading cane and in the laboratory during a VO2max test. Productivity (metric tons-day-1) of the workers was also obtained. During work, VO2 was 1.251-min-1, VE 38.81 min-1, and fH 120 beats-min-1. The subjects worked at 42% of VO2max (6.3 +/- 1.0 kcal-min-1) during the field measurement periods. Energy expenditure was estimated to average 3,281 kcal-24 hr-1. Productivity was higher in men with lower fat content, resting fH and fH at VO2 = 1.25 1-min-1, indicating a positive relationship between productivity and physical fitness. Productivity was not related to age but, since VO2max decreased with age, the relative effort required to maintain productivity increased in the older workers. Efficiency (kg cane loaded-1 VO2-1) and estimated sustained effort (percent VO2max) were not significantly correlated with productivity in this type of discontinuous, moderate work.

Age Factors↗
PubMed1977

Productivity and maximal oxygen consumption in sugar cane cutters.

Vo2max and daily productivity (metric tons/day) have been measured in 46 sugar cane cutters 18 to 34 years of age. A multiple regression analysis demonstrated that productivity was simultaneously related to VO2max, height and body fat (r=0.685;P less than 0.001). The multiple regression equation was: productivity (tons/day)=0.81 VO2max-0.14 percent fat +0.03 height -1.96. The data indicate that productivity is affected indirectly by nutritional status through the influence of the latter on height, fat content and VO2max. The decrease in VO2max that occurs with age was similar to that reported in the literature. Evidence is presented that, as the worker ages, a higher percent VO2max has to be utilized to maintain productivity.

Adolescent↗
PubMed1977

Efficiency and daily work effort in sugar cane cutters.

Productivity (metric tons (tonnes)/day), efficiency (kg cane cut/litre Vo2), and effort (percent Vo2 max sustained during an 8-hour workday) have been measured in 54 Colombian sugar cane cutters. In workers who sustained less than 40% Vo2 max during the workday, the effort expended was related to productivity (4 = 0-71) but efficiency and productivity were not significantly correlated. In 16 workers sustaining a greater than 40% Vo2 max during the workday, productivity and effort were not related and efficiency was significantly reduced. Subjects using less than 40% Vo2 max were divided into good, average and poor producers and compared with the men with low efficiencies. In general, these inefficient men had the anthropometric and physical fitness characteristics of low productivity workers (smaller stature, weight and Vo2 max). However, the frequency of good, average, and poor cutters in the inefficient group did not differ from that of the men expending less than 40% of their maximum effort nor was their average productivity different. No obvious reasons for the differences in efficiency and effort of these men were found.

Adult↗
PubMed1976

The aerobic power of several groups of laborers in Colombia and the United States.

Physiological responses to exercise and anthropometry were measured in several groups of physical laborers. The groups included Colombian sugar cane cutters, sugar cane loaders and general farm laborers. In addition, migrant workers and civil service laborers from the United States were studied. The Colombian populations were generally shorter, weighed less and had less body fat than the United States group. The nutritional state of the Colombian groups, as measured by the hematocrit, hemoglobin, serum albumin and total blood protein, appeared normal. The aerobic power of the Colombia populations was significantly larger than the United States groups. The larger aerobic power of the Colombian groups is probably related to greater physical fitness associated with the physical demands of their occupations.

Adult↗