José Méndez

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.

Sports science and body composition analysis: emphasis on cell and muscle mass.

Because we are unsure of many of the constants that we use in the calculation of components of body composition, there is a need for a greater number of postmortem analyses in order to prepare better equations for more accurate utilization of indirect noninvasive measurements. At present, most investigators who study active people (including athletes) use techniques that only provide an approximation of body fatness. Because excess fat serves as a burden to the body during transport in the performance of many physical activities, fatness constitutes a variable of concern. Fat-free body weight is usually calculated by difference and serves as a reference for some physiological functions. Although fat-free weight and lean body mass are not the same, most investigators calculate fat-free weight and many use the terms interchangeably. Some of the assumptions and problems in utilizing hydrodensitometry in the calculation of body fatness remain unresolved, such as the true densities of the different gross components of body composition in the young, aged, physically fit, etc. A variety of body composition profiles of different athletes have been published in recent years, which substantially augment efforts initiated in the 1940s and 1950s. The regular employment of a total body water assessment along with hydrodensitometry would improve the accuracy of calculation of body fatness, but the procedure is somewhat expensive in cost and time of subject involvement. In order to extend our knowledge of body composition and to quantitatively ascertain the mass of skeletal muscle, some of the procedures for calculating cell and muscle mass are reviewed including total body potassium, total body nitrogen, creatinine excretion, and 3-methylhistidine excretion. These procedures reveal important information, but require further investigation before we are confident that we are measuring cell or muscle mass. We have focused on 3-methylhistidine excretion because preliminary investigation suggests that it may reveal differences in muscle mass not detected by densitometry.

Serum Lipid Levels Among Rural Guatemalan Indians

S ERUM cholesterol levels imi adult Guatemnalan Indians have been found to be very low as compared with values reported for the urban, non-Imidian population in the upper income groups of Guatemala City and the population of North America and some European counri6 The low serum cholesterol values observed in the Guatemalan Indians and in many population groups throughout the world appear to be associated with a low fat comisumption and with a low incidence of coronary heart disease . . .8 Conversely, in population groups consuming large amounts of fat, especially saturated lipids, serum cholesterol levels amid mortality rates due to coronary heart disease are higher.36 Up to fifty years of age, cholesterol levels are usually higher in muemi than women, a finding which also parallels the higher incidence of myocardial infarction commonly observed among men. However, the often reported increases in serum cholesterol concemitration with age9”#{176}are not found in all population gr’ ‘3 III Guatemala about 54 per cent of the total population of 3.5 millions are classified as Indians. The majority of them live under relatively primiti e comiditions in small cornmnunities scattered throughout the country. They are divided imito various groups, but

Energy: Caloric Requirements

The science of bioenergetics, as we know it today, was perhaps initiated with the studies of Lavoisier (1743–1794), who discovered the principles of in vivo and in vitro oxidation and combustion. He ascertained that the intensity of metabolism was dependent upon physical work, environmental temperature, and food intake. He devised an ice calorimeter to study the body heat emanating from guinea pigs and determined that oxygen was utilized by the metabolizing body and that a gas was given off (carbon dioxide) that was the same as that produced when acid was added to limestone. Lavoisier appreciated the chemical identity of the oxidative process of carbon and the burning of carbon in a candle flame.

Diet and Serum Cholesterol Levels Among the "Black Caribs" of Guatemala

SERUM cholesterol levels have been found to be markedly reduced among lower socioeconomic urban groups in Guatemala,13 and the incidence and severity of atherosclerotic heart disease in these people is also very low when coml)ared with that in business and professional persons.45 The people in the rural lower socioeconomic groups in Guatenuala are predominantly Mayan Indian in racial origin while those in the upper income groups are primarily European caucasoid and mestizo. This racial difference is not considered responsible for the findings, however, since similar differences in atherosclerosis are found between racially homnogeneous persons in the upper and lower income groups in Costa Rica . 2 .5 Environmental conditions must, therefore, be responsible; among the environmental variables which have received special attention are dietary differences.

A practical and reliable method for determination of urinary 3-methylhistidine

A practical and reliable semiautomated method for analysis of urinary 3-methylhistidine (3-MH) was designed combining the isolation of 3-MH by ion-exchange chromatography with the color reaction given by ninhydrin-orthopthalaldehyde (ninhydrin-OPT) reagent after alkalinization. 2 ml of urine were passed through disposable columns packed with an ion-exchange resin (Dowex 50-X8, 200-400 mesh) and the acidic and neutral amino acids were eluted with 10 ml of 0.2 M pyridine solution. Then, the 3-MH was quantitatively eluted and separated from histidine with a volume of 9 ml of a 1.5 M pyridine solution. Standard Autoanalyzer equipment was used for the automation of spectrophotometry. The method permits the analysis of 40 samples in duplicate per day. The 3-MH color reaction was linear for concentrations from 0.015 to 0.24 mu mol/ml. The mean recoveries of 3-MH from standards and urine were 98.6 +/- 1.3 and 99.0 +/- 1.3%, respectively. Duplicate determinations of urine samples showed a variation coefficient of 1.8%. An excellent agreement was obtained between urine samples analyzed by the present method and by an amino acid analyzer. The need for the elimination of the interfering amino acids was clearly demonstrated.

Liver composition in kwashiorkor and marasmus

Abstract Livers taken post-mortem from seven children with kwashiorkor, eight with marasmus and eight “apparently well-nourished” were analyzed for water, fat, protein, lipid phosphorus, cholesterol, and ash content. The final causes of death in most cases were diarrhea of unknown etiology and acute bronchopneumonia. The nutritional status was assessed from clinical history, socioeconomic information, and direct examination. Body weight and length, thickness of the abdominal subcutaneous tissue, and weight of the livers were also recorded. The results were expressed on a fresh, dry and fat-free per cent basis. It was found that the chief variable influencing the gross composition of livers in all three types of cases is the amount of fat. The fat-free tissue apparently remains basically unchanged. When the total liver components, taking into account liver weights, are expressed per unit of body length, all the values, with the exception of fat, become similar. The fatty change of the liver is a characteristic feature of kwashiorkor, and it is wholly lacking in marasmus.