RESUMO
Obesity is the most common cause of human essential hypertension in most industrialized countries. Although the precise mechanisms of obesity hypertension are not fully understood, considerable evidence suggests that excess renal sodium reabsorption and a hypertensive shift of pressure natriuresis play a major role. Sympathetic activation appears to mediate at least part of the obesity-induced sodium retention and hypertension since adrenergic blockade or renal denervation markedly attenuates these changes. Recent observations suggest that leptin and its multiple interactions with neuropeptides in the hypothalamus may link excess weight gain with increased sympathetic activity. Leptin is produced mainly in adipocytes and is believed to regulate energy balance by acting on the hypothalamus to reduce food intake and to increase energy expenditure via sympathetic activation. Short-term administration of leptin into the cerebral ventricles increases renal sympathetic activity, and long-term leptin infusion at rates that mimic plasma concentrations found in obesity raises arterial pressure and heart rate via adrenergic activation in non-obese rodents. Transgenic mice overexpressing leptin also develop hypertension. Acute studies suggest that the renal sympathetic effects of leptin may depend on interactions with other neurochemical pathways in the hypothalamus, including the melanocortin-4 receptor (MC4-R). However, the role of this pathway in mediating the long-term effects of leptin on blood pressure is unclear. AIso, it is uncertain whether there is resistance to the chronic renal sympathetic and blood pressure effects of leptin in obese subjects. In addition, leptin also has other cardiovascular and renal actions, such as stimulation of nitric oxide formation and improvement of insulin sensitivity, which may tend to reduce blood pressure in some conditions. Although the role of these mechanisms in human obesity has not been elucidated, this remains a fruitful area for further investigation, especially in view of the current epidemic of obesity in most industrialized countries.
Assuntos
Hipertensão , Obesidade , Angiotensinas , Leptina , Sistema Nervoso SimpáticoRESUMO
Obesity is the most common cause of human essential hypertension in most industrialized countries. Although the precise mechanisms of obesity hypertension are not fully understood, considerable evidence suggests that excess renal sodium reabsorption and a hypertensive shift of pressure natriuresis play a major role. Sympathetic activation appears to mediate at least part of the obesity-induced sodium retention and hypertension since adrenergic blockade or renal denervation markedly attenuates these changes. Recent observations suggest that leptin and its multiple interactions with neuropeptides in the hypothalamus may link excess weight gain with increased sympathetic activity. Leptin is produced mainly in adipocytes and is believed to regulate energy balance by acting on the hypothalamus to reduce food intake and to increase energy expenditure via sympathetic activation. Short-term administration of leptin into the cerebral ventricles increases renal sympathetic activity, and long-term leptin infusion at rates that mimic plasma concentrations found in obesity raises arterial pressure and heart rate via adrenergic activation in non-obese rodents. Transgenic mice overexpressing leptin also develop hypertension. Acute studies suggest that the renal sympathetic effects of leptin may depend on interactions with other neurochemical pathways in the hypothalamus, including the melanocortin-4 receptor (MC4-R). However, the role of this pathway in mediating the long-term effects of leptin on blood pressure is unclear. Also, it is uncertain whether there is resistance to the chronic renal sympathetic and blood pressure effects of leptin in obese subjects. In addition, leptin also has other cardiovascular and renal actions, such as stimulation of nitric oxide formation and improvement of insulin sensitivity, which may tend to reduce blood pressure in some conditions. Although the role of these mechanisms in human obesity has not been elucidated, this remains a fruitful area for further investigation, especially in view of the current "epidemic" of obesity in most industrialized countries.
Assuntos
Hipertensão/fisiopatologia , Leptina/fisiologia , Neuropeptídeos/fisiologia , Obesidade/fisiopatologia , Sistema Nervoso Simpático/fisiologia , Animais , Pressão Sanguínea , Índice de Massa Corporal , Circulação Coronária , Modelos Animais de Doenças , Cães , Ácidos Graxos/fisiologia , Humanos , Hipertensão/etiologia , Rim/metabolismo , Natriurese , Obesidade/complicações , Sódio/urinaRESUMO
The selenium in the diet of persons in arsenic-endemic areas, high levels of arsenic in the drinking water, was evaluated. The methodology used was that of 24-hr dietary recall. Daily selenium intakes of two rural towns in northern Mexico were found to be similar, approximating 72.9 and 60.6 micrograms. These values were similar to those of a previously arsenic-exposed area from California, Edison community. The Edison participants had a daily selenium intake of 61.8 micrograms. The possible negative effect of selenium to produce differences in reported geographical variation in disease could not be substantiated in this study. Other nutrient intakes, protein and energy were also found similar for communities. Differences were noted in vitamin A intake where one-third the daily requirement was experienced by Mexican participants compared to two-thirds the requirement being satisfied by those participants from Edison.
Assuntos
Arsênio , Dieta , Ingestão de Alimentos , Selênio/análise , Poluição Química da Água , Abastecimento de Água , Adulto , Proteínas Alimentares/análise , Feminino , Humanos , Masculino , México , Pessoa de Meia-Idade , Necessidades Nutricionais , Selênio/administração & dosagem , Vitamina A/administração & dosagem , Vitamina A/análiseRESUMO
We studied the response to reimmunization at 36 months of age with Haemophilus influenzae type b (Hib) polyribosylribitol phosphate (PRP) capsular polysaccharide vaccine. Children enrolled in the study had previously received PRP or PRP plus diphtheria and tetanus toxoids with pertussis vaccine at 18 months of age. A control group of children, who received a first dose at 36 months of age, was also studied. Ninety-five percent of children receiving a second dose of vaccine had a postimmunization anti-capsular antibody level of greater than or equal to 1 microgram/mL. In comparison, 70% of 36-month-old children who received their first dose of PRP had a postimmunization level greater than or equal to 1 microgram/mL (P = 0.09). The geometric mean titer at 37 months of age was 8.64 micrograms/mL in children who had received two doses of PRP vaccine, compared with 2.19 micrograms/mL in the group who received only one dose of PRP at 36 months of age (P = 0.04). We conclude that infants immunized at 17 to 19 months of age with PRP had an excellent immunologic response to reimmunization at 36 months of age.
Assuntos
Vacinas Bacterianas/administração & dosagem , Vacinas Anti-Haemophilus , Imunização Secundária , Polissacarídeos Bacterianos/administração & dosagem , Fatores Etários , Anticorpos Antibacterianos/análise , Cápsulas Bacterianas , Vacinas Bacterianas/imunologia , Pré-Escolar , Toxoide Diftérico/administração & dosagem , Vacina contra Difteria, Tétano e Coqueluche , Combinação de Medicamentos/administração & dosagem , Feminino , Humanos , Lactente , Masculino , Vacina contra Coqueluche/administração & dosagem , Polissacarídeos Bacterianos/imunologia , Toxoide Tetânico/administração & dosagemRESUMO
64 healthy infants, 2-3 months old, were randomly assigned to one of three vaccination groups which either diphtheria-pertussis-tetanus (DPT) vaccine, Haemophilus influenzae type b capsular polysaccharide polyribosyl-ribitol phosphate (PRP) vaccine, or PRP+P (with pertussis adjuvant) vaccine in three doses at intervals of two months. Local and systemic reactions occurred most frequently after DPT vaccination and least frequently for PRP alone. Data for 60 infants from whom complete sera sets were available indicated that 70 percent of the infants who received three doses of PRP+P showed two fold or greater increases in titers of antibody to PRP with final values above the level assumed to give protection against invasive H. influenzae type b disease (>0.15 ug/ml). In contrast, less than 10 percent of infants who received PRP vaccine alone showed 2-fold or greater increases (Summary)