RESUMO
Measurements of the electronic energy loss are presented for (4)He and (7)Li ions channeling along the Si main axial directions at intermediate to high projectile energies. The Barkas effect, an energy-loss enhancement proportional to the third power of the projectile charge at high energies, is clearly separated from other processes. It reaches about 50% for Li ions channeling along the Si [110] direction. The observed Barkas contribution from the valence-electron gas is in fair agreement with the Lindhard model.
RESUMO
Relationships between occupation, working conditions, and the development and outcome of pregnancy were analysed on a sample of women employed in hospital during their pregnancy. Ancillary staff members experienced more uterine contractions during pregnancy, more preterm deliveries, and more low birthweight infants than those performing other duties; this remained true after adjusting for social characteristics. The rate of preterm delivery was significantly higher in the presence of at least two of the following arduous working conditions: stand-up work, carrying heavy loads (exclusive of patients), and heavy cleaning tasks; this was so, whatever the occupation.
Assuntos
Recursos Humanos em Hospital , Gravidez , Mulheres Trabalhadoras , Mulheres , Trabalho , Feminino , França , Humanos , Recém-Nascido de Baixo Peso , Recém-Nascido , Trabalho de Parto Prematuro , Complicações na Gravidez , Contração Uterina , Índias Ocidentais/etnologiaRESUMO
Twenty years ago, we were invited to present a paper on severe protein-malnutrition in children in a meeting organized by this same Academy. In reviewing that paper for this presentation, it was very frustrating to find that the basic principles we stated there in regard to the nature of the probelm and its epidemiology are as valid today as they were 20 years ago. As most other workers in the field, we were then particularly concerned with the severe forms of protein-calorie malnutrition (PCM): kwashiorkor and marasmus. These individual cases occupied a large proportion of pediatric beds in hospitals of most developing countries, and we were interested in finding better ways to treat them. But also we were studying these cases as a basis for understanding the responsible factors better and for designing possible preventive measures. The interrelations of kwashiorkor and marasmus were recognized then, as well the fact that both protein and calories should be considered together in the epidemiology of the problem. We were also beginning to understand that the severe clinical cases that we were seeing in the hospitals were only the visible part of a much greater problem affecting the communities from which these children came. With the knowledge then available on the epidemiology of PCM, we were also starting to explore some specific measures for its prevention. I would like now to review what progress we have made, if any, in the understanding of the nature and magnitude of the problem, its epidemiology, and in designing preventive measures.
Assuntos
Países em Desenvolvimento , Desnutrição Proteico-Calórica/etiologia , Pré-Escolar , Feminino , Guatemala , Humanos , Lactente , Recém-Nascido de Baixo Peso , Recém-Nascido , México , Gravidez , Desnutrição Proteico-Calórica/prevenção & controleAssuntos
Métodos Epidemiológicos , Programas Nacionais de Saúde , Distúrbios Nutricionais/epidemiologia , Inquéritos Nutricionais , Antropometria , América Central , Pré-Escolar , Técnicas de Laboratório Clínico , Meio Ambiente , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Saúde Bucal , Equipe de Assistência ao Paciente , Estudos de AmostragemRESUMO
The results of two studies of the influence of moderate maternal malnutrition on the weight and chemical characteristics of the placenta are discussed. In the first study, two groups of pregnant women of high and low socioeconomic status from Guatemala City were studied. Socioeconomic status was defined by family income, educational level of the mother, and environmental sanitary conditions. Both groups were very similar with respect to age, parity, gestational age, and absence of severe disease during pregnancy. The average placental weight in the low socioeconomic group was 15 per cent below that of the high socioeconomic group and there was a consistent association between the postpartum maternal weight and placental weight. There were no differences between the two groups regarding placental concentration of fat, protein, water, ash, hemoglobin, and DNA; hydroxyproline and fat concentration were significantly lower in the low socioeconomic group. The hypothesis that the difference in placental weight observed between the two groups was primarily due to maternal nutritional status was tested in the second study by means of nutritional intervention in four rural villages in Guatemala. Two of the villages received a protein-calorie preparation while the other two received a calorie supplement. Placental weight was higher among women with high levels of supplemented calories during pregnancy, independently of the type of food supplement ingested. On the average, the groups with low caloric supplementation (smaller than 20,000 calories) had placental weight 11 per cent below those with high caloric supplementation (larger than or equal to 20,000 calories), In contrast to placental weight, the concentration of placental chemical components studied was not associated with caloric supplementation. It was concluded that moderate protein-calorie malnutrition during pregnancy leads to lower placental weight without significantly changing the concentration of the biochemical components studied. The reduction of placental weight may be the mechanism by which maternal malnutrition is associated with high prevalence of low-birth-weight babies in these populations.
PIP: The results of 2 studies carried out at the Institute of Nutrition of Central American and Panama are described. The 1st study was of an urban population and the other in rural villages. The influences of mode rate maternal malnutrition on the weight of the placenta and its chemical characteristics were particularly studied. Placentas were homogenized and then divided into 3 equal parts which were lyphilized. In the urban study, women of high and of low socioeconomic status were compared. The low socioeconomic group was considered to suffer from calorie deficiency, and particularly protein malnutrition at the time of the study. The values of the tricipital skinfold tests were lower in this group, and the weight for height ratio was low (p less than .01). The average placental weight in the low socioeconomic group was 15% below th at of the high socioeconomic group. Placental concentrations of protein, water, ash, hemoglobin, and DNA were the same in the 2 groups, while hydroxyproline and fat levels were less in the low socioeconomic group, and peripheral villi areas of the placenta were shown to be less in this group (p less than .001). These changes were attributed to moderate maternal malnutrition. In the rural study the female populations of 4 villages were investigated. Mean weight gains during pregnancy were only 60% of normal. Diet consisted mostly of corn and beans with little animal protein. In 2 villages, a dietary supplement containing protein was distributed and in the 2 other villages another supplement without protein and of lower caloric value was given. Placental weights were 11% less in those with the lower caloric and no protein supplement. An association between maternal malnutrition, placental weight, and birth weights of infants was shown. Low placental weight was considered to be the most important measurable factor in reducing birth weights.
Assuntos
Placenta/fisiopatologia , Complicações na Gravidez/fisiopatologia , Desnutrição Proteico-Calórica/fisiopatologia , Peso ao Nascer , Carboidratos da Dieta/administração & dosagem , Proteínas Alimentares/administração & dosagem , Feminino , Guatemala , Inquéritos Epidemiológicos , Humanos , Necessidades Nutricionais , Tamanho do Órgão , Placenta/análise , Gravidez , Desnutrição Proteico-Calórica/prevenção & controle , População Rural , Fatores Socioeconômicos , População UrbanaRESUMO
Diarrheic processes pose a grave health threat in much of Latin America, especially for small children. One reason for this is the close connection between diarrhea and lack of proper nutrition. The present article seeks to explore this connection by examining two of its main components: the protection against diarrhea resulting from breast-feeding and the increased vulnerability to diarrhea created by malnutrition. Breast-feeding helps prevent enteric infections in several ways. For one thing, the mother's colostrum and milk contain antibodies against some enterobacterial antigens. For another, the so-called "bifid factor" in human milk helps discourage growth of pathogenic enterobacteria in the intestinal lumen. Furthermore, children living in unhealthy surroundings become heavily exposed to common bacteria when breast-feeding stops, a circumstance deemed largely responsible for "weaning diarrhea." Proper nutrition in general is also important, since diarrhea tends to be more common and severe among malnourished children. Several processes that could contribute to this problem have been suggested. These include morphological alterations of the intestinal mucosa in malnourished children, poor intestinal absorption of fats and other nutrients, irritation caused by increased concentrations of free bile acids, and changes in the composition of the intestinal flora. Though not all these processes are well understood, it is clear that malnutrition favors development of diarrhea, while diarrhea in its turn precipitates and aggravates malnutrition. The sad plight of millions of children in the Americas is the result of this combined interaction. Many of those who experience it die, and the survivors fail to achieve their full potential growth and development. The control of diarrheic infections alone would greatly improve these children's nutritional status. Likewise breast-feeding in the early months of life, duly supplemented later and followed by a sound diet after weaning, would considerably reduce the danger and damage caused by diarrheic infections.