[Nutrition status evaluation of the women at reproductive age. Uses and limitations]. / Evaluación del estado de nutrición de la mujer en edad reproductiva. Usos y limitaciones.

Information is given about the main methods for nutrition status evaluation of the woman, this information is oriented to three stages of the woman's life cycle: adult stage, gestation stage and lactation stage. The usefulness as well as the limitations of the diet surveys are discussed. The main anthropometric indicators are presented, useful in the clinical practice to evaluate nutrition status of the non-pregnant woman (body mass index, waist/hip index and skinfolds), pregnant woman (percentage of expected weight for height and gestation age, weight gain during pregnancy, height of fundus of uterus, arm circumference and skinfolds) and lactating woman (weight loss and skinfolds). The most important nutrition status biochemical indicators are discussed. At last some special evaluation technics as measurements of body composition and balance methods are discussed.

Dietary protein level regulates expression of the mitochondrial branched-chain aminotransferase in rats.

The first step in the degradation of branched-chain amino acids (BCAA) is transamination catalyzed by the branched-chain aminotransferase (BCAT), which is located in extrahepatic tissues. Studies of the effect of dietary protein on BCAT activity have given contradictory results. Therefore, we established the levels of BCAT activity and mitochondrial BCAT (BCATm) mRNA expression in different organs and tissues of rats. We then determined the effect of different levels of dietary protein in well-nourished rats, the effect of feeding a 0.5% casein diet for 5 wk (protein-malnourished rats) and nutritional rehabilitation of these rats with different levels of dietary protein on BCAT activity and BCATm mRNA expression in selected tissues. Finally, the response of tissue BCAT activity and BCATm mRNA levels in rats fed a 10% casein diet and injected with glucagon (4 d) or hydrocortisone (7 d) was determined. The highest concentration of BCATm mRNA was found in stomach, followed by kidney, heart, muscle, brain, skin and lung. Low levels were found in intestine, and no BCATm mRNA was detectable in liver. Although BCAT activity was significantly higher in muscle, kidney and brain from rats adapted to consume a 50% casein diet for 7 h/d for 10 d than in rats fed 6, 18 or 35% casein diets, only muscle had significantly higher levels of BCATm mRNA. In protein-malnourished rats, BCAT activity and BCATm mRNA expression in kidney, muscle and heart were not different from those of rats with free access to an 18% casein diet. Nutritional rehabilitation of the protein-malnourished rats with 50% casein for 21 d significantly increased the BCAT activity and BCATm mRNA expression in muscle. Neither hydrocortisone nor glucagon injection affected BCAT activity or BCATm mRNA concentrations in rat kidney, muscle or heart. We conclude that the nutritional regulation of BCATm is extrahepatic, tissue specific and may involve transcriptional and post-translational mechanisms.

[Stable isotopes in nutrition research]. / Isotopos estables en estudios de investigacion en nutricion.

During the last decades several new techniques have been developed for measuring the utilization of nutrients in humans. The development and potential use of techniques with stable isotopes are discussed. Examples of the different studies are presented for determining whole body aminoacid and protein dynamics like lipids and glucose metabolism in humans. The practical use of these diverse stable isotopically labeled biochemicals provide safe, ethical, noninvasive investigation of nutritional metabolism in humans.

[Effect of food consumption restriction in adult rats on the growth and tissue composition of their suckling offspring]. / Efecto de la restricción en el consumo de alimento de la rata adulta sobre el crecimiento y la composición tisular de la cría lactante.

The repercussion of food restriction consumed by the adult rat during pregnancy and lactation, on the postnatal growth and tissue composition of the young was evaluated during lactation. Two groups of Sprague-Dawley rats were used, one control group was fed "ad libitum" (AL) and the other group, a restricted diet (RD), 30% less of the normal diet. From the eight day of pregnancy and throughout lactation, the food intake and weight of the animals was registered daily. At birth the number of young was adjusted to eight and the weight and tail length were registered daily. At 7, 14, and 21 days of lactation the young of both groups were sacrificed. The liver and the muscles of the extreme posterior were dissected and the wet weight, dry weight, proteins and nucleic acids determined. The mother rats fed "ad libitum increase their intake to 300% from the first day of lactation and they presented a greater body weight than those rats under restricted diet, also begun on the first day of lactation. At birth there were no differences in the weight and the length of the young, however at the end of the lactation the growth rate was significantly lower among the group of rats RD. In the group of young under RD, protein and nucleic acids concentration in the liver were significantly less than those of the AL group and similarly in the muscle, the dry weight, proteins, RNA and DNA were significatively less. From these results it is concluded that the food restriction of the adult rat by 30% during lactation, has a negative effect on the postnatal growth of the young, in terms of weight, length, liver tissue composition and muscular mass.

[The biological bases of human lactation]. / Bases biológicas de la lactancia materna.

The mammary gland integrated by secretory acini has two main physiological goals: the lactogenesis and the milk ejection. The first is controlled by estrogens, prolactin and cortisol; the former by oxytocin. Milk is synthesized through five mechanisms namely: I. Cellular synthesis and exocytosis; 2. Cellular synthesis and exocytosis packed in cell membrane fragment; 3. Passive transport through both cell membranes; 4. Active transport via receptors through both cell membranes, and 5. Paracellular transport. The human milk has a high concentration of lactose and relatively low concentrations of fat and protein in comparison to other species. Its composition varies little in relationship to maternal diet, nevertheless, it holds a close correlation, with body composition of the mother. Exclusively breast-fed infants grow in a similar manner to those formula-fed up to 4-6 months; afterwards growth decelerates, to spurt up the need for complementary food. It has been amply demonstrated that human milk protects against acute infections, both bacterial and viral. The current hospital practices of perinatal care should be changed in our country in order to favour the initiation of breast-feeding. Concerned physicians should have more and precise knowledge about the physiology of lactation in order to help mothers to pursue a successful lactation.

Maternal nutritional status and milk volume. Is there a cause-effect relationship?

Studies on human lactation were examined in order to gather some answers about questions concerning the effect of maternal food intake, size, fatness and economic status on milk production. Up to date, evidence in the literature is insufficient to permit definitive answers, but a general conclusion can be drawn: milk volume varies little among mothers with largely variable energy intakes, sizes and economic status. There is a great need for more controlled studies focusing on the relationship between maternal energy balance and milk output. Although many studies have separately addressed the nutritional changes in mothers throughout lactation (1-8) and milk consumption by infants (9-17), very few have correlated maternal nutritional conditions and the volume of milk consumed. This report will consider investigations published from 1975 and on, combining data on maternal nutritional status and milk production in the same individual. The rationale is that around 1975 more accurate and standardized methodology began to be used in related studies. Milk output is estimated by the summary of the differences of body weights of infants obtained before and after each milking episode during 24 hours. Before 1975 the balances used for such a purpose had very poor precision, and this interfered seriously on the inter and intra-personal variability of the measurements. Electronic scales made available after that year gave enough reliability to the procedure. This report is comprised of studies from birth to four months postpartum, when energy supplementation is less common, and quantitatively less important. Nutritional status of the mothers will be analyzed on the basis of four categorizing variables: social and economic status, anthropometry, food intake and body composition.

[Breast feeding and protein metabolism]. / La lactancia y el metabolismo de proteínas.

During pregnancy, nutrient body reserves are accumulated, especially fat, which are later mobilized during the breastfeeding period. During the synthesis of maternal milk, the mammary tissue increases its speed to synthesize structural, catalytic and exporting proteins. Due to the above, there is also an increase in the uptake of amino acids as well as the concentration of RNA within that tissue. The demand for energy during the breastfeeding period, exceeds in calories the amount of intake by the mother, causing a loss in body mass; at the same time the exchange in protein balance seems to lead towards degradation. The demand for substrates by the breast tissue is covered by the dietary intake and by other substrates mobilized from the maternal compartments. In the case where amino acids are needed, muscles have become a source of supply. These amino acids are used in the synthesis of proteins and oxidized in order to obtain fatty acids and carbohydrates. When weaning, the muscle mass recovers the amount of proteins in an undefined amount. There is a need for more information concerning the adaptations which occur during the metabolism of proteins during breast-feeding. Breast-feeding; proteins; mammary tissue.