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Biomedical subjects

B Caballero

Publications and source records attributed to B Caballero.

At least 19 recordsLinked to original sources

Fortification, supplementation, and nutrient balance.

Efforts to combat nutrient deficiencies have centered on supplemental nutrient administration and addition of selected nutrients to the food chain in the form of food fortification. Over the past several decades, and as the association between diet and chronic diseases became apparent, supplementation and fortification were also targeted at healthy individuals, with the aim of reducing their risk of future diseases such as cardiovascular diseases, diabetes, and cancer. While supplementation strategies are playing a major role in reducing micronutrient deficiencies around the world, there is less compelling evidence for their role in reducing risk of chronic diseases in healthy individuals, perhaps with the exception of folic acid and reduction of neural tube defects. Nevertheless, with our increasing understanding of the genetic heterogeneity of human nutrient requirements, it is likely that certain groups or populations may clearly benefit from higher intakes of certain nutrients. In addition to supplementation or fortification with specific nutrients, the consumption of certain dietary patterns (such as the Mediterranean diet) is associated with a reduced risk of chronic diseases, particularly cardiovascular diseases.

Dietary Supplements↗

Early nutrition and risk of disease in the adult.

The differentiation of key metabolic systems that occurs during intrauterine life is greatly influenced by environmental nutritional conditions, which in turn are related to maternal nutritional status. In postnatal life, childhood exposure to slow-acting environmental factors, primarily through the diet, will begin to condition adult susceptibility to diseases. Examples of these dietary factors are intake of saturated fat, sodium, calcium, etc. For example, bone calcium accumulation during childhood and adolescence will be a major determinant of risk of osteoporosis later in life. Similarly, a high intake of saturated fat during childhood may promote the process of atherosclerosis in persons with genetic susceptibility, thus accelerating the clinical manifestations of coronary heart disease in adult life. These findings, although still not completely clarified, constitute a significant opportunity for preventive intervention. While preventive intervention in adult life may reduce risk, this is usually difficult and results are often limited. One example would be obesity. In contrast, interventions early in life, aimed at reducing these early risk factors, could potentially result in major reductions in the incidence of several diseases of adults.

Adolescent↗

Bone mineral content in girls perinatally infected with HIV.

BACKGROUND: Early diagnostic efforts and advances in multidrug therapy have considerably prolonged the survival time of children infected perinatally with HIV. Despite these advances, few studies have addressed calcium status and bone growth in HIV-infected children. OBJECTIVE: Our objective was to examine the effect of HIV infection on calcium status and bone growth in children. DESIGN: We measured calcitropic hormones, urinary calcium excretion, bone mineral content, and body composition in 19 young girls aged 9.2 +/- 2.6 y (range: 5.9-15.2 y) who were infected perinatally with HIV. RESULTS: Serum concentrations of 1,25-dihydroxyvitamin D [1,25(OH)(2)D] and parathyroid hormone concentrations were elevated above normal ranges in 25% and 12% of these girls, respectively. Urinary calcium excretion normalized for creatinine excretion was also elevated (Ca/Cr >0.18) in 17% of these children despite suboptimal calcium intakes (679 +/- 437 mg/d). Total-body bone mineral content, measured with the use of dual-energy X-ray absorptiometry, averaged 845.1 +/- 279.0 g and was on average 2.7 z scores below age- and race-matched values reported in non-HIV-infected healthy girls. Significant positive correlations were found between an indirect marker of bone resorption in urine (N:-telopeptide) and 1,25(OH)2D (P < 0.02, r2 = 0.586, n = 9), and between serum N-telopeptide and total alkaline phosphatase (P < 0.001, r2 = 0.541, n = 17), suggesting that calcium insufficiency may be increasing bone resorption in this group. CONCLUSIONS: Young girls with HIV infection had low bone mass and evidence of calcium insufficiency. Nutritional counseling of children with HIV infection should emphasize adequate calcium intakes because of the importance of this age period in bone mineral acquisition.

Absorptiometry, Photon↗

Introduction. Symposium: Obesity in developing countries: biological and ecological factors.

Over the past decade there has been an increasing concern about the impact of chronic, noncommunicable diseases on the health of developing world populations. Traditionally, major causes of illness and death in developing countries have been linked to infectious diseases and undernutrition, and these are still major public health problems in several regions of the world. But recent projections indicate that in 20 y noncommunicable diseases will account for over 60% of the disease burden and mortality in the developing world. Obesity is recognized as an underlying risk factor for many of these chronic conditions. As in developed societies, the risk for obesity in developing countries is also strongly influenced by diet and lifestyle, which are changing dramatically as a result of the economic and nutrition transition. This symposium discusses key aspects of the phenomenon of obesity in the developing world and provides some specific examples from countries facing increasing prevalence of that condition.

Adult↗

Diet culture and obesity in northern Africa.

The etiology of obesity in North Africa is not well understood and few studies shed any light on its development among women. This study compiles what is known about the prevalence of obesity and its determinants in Morocco and Tunisia. Results from the authors' two surveys on nutrition-related disease among reproductive-age women (sample size: 2800) and their children (1200 children under 5 y and 500 adolescents) were combined with data from four national income and expenditure surveys (dating from 1980) to assess obesity trends and development in Morocco and Tunisia. Overall levels of obesity, identified by body mass index (BMI) > or = 30 kg/m(2), were 12.2% in Morocco and 14.4% in Tunisia. Obesity is significantly higher among women than among men in both countries (22.7% vs. 6.7% in Tunisia and 18% vs. 5.7% in Morocco) and prevalence among women has tripled over the past 20 y. Half of all women are overweight or obese (BMI > 25) with 50.9% in Tunisia and 51.3% in Morocco. Overweight increases with age and seems to take hold in adolescence, particularly among girls. In Tunisia, 9.1% of adolescent girls are at risk for being overweight (BMI/age > or = 85th percentile). Prevalence of overweight and obesity are greater for women in urban areas and with lower education levels. Obese women in both countries take in significantly more calories and macronutrients than normal-weight women. The percentage contribution to calories from fat, protein and carbohydrates seems to be within normal limits, whereas fat intake is high (31%) in Tunisia and carbohydrate intake (65-67%) is high in Morocco. These are alarming trends for public health professionals and policy makers in countries still grappling with the public health effects of malnutrition and micronutrient deficiencies. Health institutions in these countries have an enormous challenge to change cultural norms that do not recognize obesity, to prevent significant damage to the public's health from obesity.

Adolescent↗

Overweight and obesity among Alaskan Eskimos of the Bering Straits Region: the Alaska Siberia project.

OBJECTIVE: To document the height, weight, BMI and prevalence of obesity for Eskimo residents of four villages of the Bering Straits Region of Alaska. DESIGN AND SUBJECTS: 454 Non-pregnant residents over 24 y of age, with at least one Eskimo grandparent participated in one cross sectional survey within each village. MEASUREMENTS: Height, weight, calculation of BMI (kg/m2), proportion of 'overweight' (BMI 25-29.9), and proportion of 'obese' (BMI>/=30). RESULTS: For women and men, respectively, mean heights were 153.4 and 165.2 cm; weights were 64.2 and 71.6 kg; and BMI were 27.2 and 26.2 kg/m2 after age standardization. For women, 27.9% were overweight, and 32.8% were obese compared with 36.2% and 15.6%, respectively, for men. Alaskan Eskimo participants of the Alaska Siberia Project had a significantly lower proportion of total overweight (BMI>/=25, 54.9% for women, and 32.0% for men) compared with the three sites of the Strong Heart Study, which ranged from 65.9 to 80.2% for women and 53.6 to 66.7% for men. Compared with American men of all races, the proportion of overweight and obese participants was similar for Eskimo men. The proportion of obese was significantly higher for Eskimo women compared with American women of all races, but the proportion of overweight was similar. CONCLUSION: Although the prevalence of obesity among the Alaskan Eskimos is lower than for American Indians, the high proportion of overweight observed in this study is of concern for Alaskan Eskimo adults, especially for women.

Adult↗

Estimation of body fat from anthropometry and bioelectrical impedance in Native American children.

OBJECTIVE: Obesity, as measured by body mass index, is highly prevalent in Native American children, yet there are no valid equations to estimate total body fatness for this population. This study was designed to develop equations to estimate percentage body fat from anthropometry and bioelectrical impedance as a critical part of Pathways, a multi-site study of primary prevention of obesity in Native American children. DESIGN: Percentage fat was estimated from deuterium oxide dilution in 98 Native American children (Pima/Maricopa, Tohono O'odham and White Mountain Apache tribes) between 8 and 11 y of age. The mean fat content (38.4%+/-8. 1%) was calculated assuming the water content of the fat-free body was 76%. Initial independent variables were height, weight, waist circumference, six skinfolds and whole-body resistance and reactance from bioelectrical impedance (BIA). RESULTS: Using all-possible-subsets regressions with the Mallows C (p) criterion, and with age and sex included in each regression model, waist circumference, calf and biceps skinfolds contributed least to the multiple regression analysis. The combination of weight, two skinfolds (any two out of the four best: triceps, suprailiac, subscapular and abdomen) and bioelectrical impedance variables provided excellent predictability. Equations without BIA variables yielded r2 almost as high as those with BIA variables. The recommended equation predicts percentage fat with a root mean square error=3.2% fat and an adjusted r2=0.840. CONCLUSION: The combination of anthropometry and BIA variables can be used to estimate total body fat in field studies of Native American children. The derived equation yields considerably higher percentage fat values than other skinfold equations in children.

Adipose Tissue↗

Plasma insulin levels and incidence of hypertension in African Americans and whites.

BACKGROUND: Hyperinsulinemia may play an important role in the pathogenesis of hypertension in whites but the role of hyperinsulinemia in hypertension in African Americans is controversial. SUBJECTS AND METHODS: We studied the relationship between insulin levels and subsequent incidence of hypertension in 140 African Americans and 237 whites who were initially screened for possible participation in the Trials of Hypertension Prevention, phase 1. Plasma insulin and serum glucose were measured at baseline and at a follow-up examination 7 years later. Blood pressure was measured by trained observers using a random-zero sphygmomanometer. Incident hypertension was defined as an average systolic pressure of 160 mm Hg or higher and/or diastolic pressure of 95 mm Hg or higher at a single visit and/or use of antihypertensive medication during follow-up. RESULTS: Over the 7 years of follow-up, the incidence of hypertension was 25.7% in the African Americans and 25.3% in the whites. Baseline plasma insulin and insulin-to-glucose ratio were associated with an increased risk of hypertension in both the African Americans and the whites. After adjustment for age, sex, race, body mass, heart rate, and alcohol consumption at baseline as well as intervention assignment in the Trials of Hypertension Prevention, phase 1, a 1-SD (21 pmol/mmol) difference in baseline insulin-to-glucose ratio was associated with a 2.77 (95% confidence interval, 1.48-5.19) odds ratio of hypertension in the African Americans and a 1.69 (95% confidence interval, 1.08-2.64) odds ratio in the whites. CONCLUSION: These results suggest that higher plasma insulin levels are associated with an increased risk of hypertension in both African Americans and whites.

Adult↗

Dietary Approaches to Stop Hypertension: a summary of study results. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension multicenter trial examined the impact of dietary patterns on blood pressure in 459 adults with blood pressure < 160 mm Hg systolic and 80 to 95 mm Hg diastolic. After a 3-week run-in period on a control diet low in fruits, vegetables, and dairy products, and with a fat content typical for Americans, participants were randomized for 8 weeks to either the control diet, a diet rich in fruits and vegetables, or a combination diet that emphasized fruits, vegetables, and low-fat dairy products. Body weight and sodium intake were held constant, and physical activity did not change during the intervention. Baseline mean +/- standard deviation systolic and diastolic blood pressures were 131.3 +/- 10.8 mm Hg and 84.7 +/- 4.7 mm Hg, respectively. Relative to the control diet, the combination diet reduced blood pressure by 5.5 mm Hg and diastolic blood pressure by 3.0 mm Hg (P < .001). For those on the fruits and vegetables diet, blood pressure reductions relative to control were 2.8 mm Hg systolic (P < .001) and 1.1 mm Hg diastolic (P < .07). In 133 participants with hypertension, the combination diet produced a net blood pressure reduction of 11.4 and 5.5 mm Hg systolic and diastolic, respectively (P < .001). In participants without hypertension (n = 326), the corresponding blood pressure reductions were 3.5 mm Hg systolic (P < .001) and 2.1 mm Hg diastolic (P < .003). In other subgroup analyses, minorities showed relatively larger reductions in blood pressure than nonminorities (P < .001). We conclude that the dietary pattern reflected in the combination diet can substantially reduce blood pressure, and, accordingly, provides an additional lifestyle approach to preventing and treating hypertension.

Adult↗

Bacteria isolated from rock art paintings: the case of Atlanterra shelter (south Spain).

The Sierra de la Plata is an Aljibe yellow sandstone formation from the Acheulian period. There are a few shelters, some of them with rock art paintings. The most representative one, and subjected to anthropogenic pressure, is that of Atlanterra, situated in a residential area. This shelter contains some rock art paintings made with iron oxides. The bacteria present in these paintings were isolated and identified using an automatic method: fatty acid methyl esters profiling. Most of the bacteria belong to the Bacillus genus, B. megaterium being the most abundant species. The isolated strains are able to reduce hematite. This is significant due to the fact that Fe(III)-(hydr)oxides are the most abundant pigments in rock art.

Bacillus↗

Whole body protein turnover in children with human immunodeficiency virus (HIV) infection.

The purpose of this study was to determine the rate of whole body protein turnover (WBPT) in human immunodeficiency virus (HIV)-infected children, and to determine the relationship between WBPT and growth. The rate of WBPT was calculated from the cumulative excretion of labeled urinary ammonia after a single intravenous dose of 15N-glycine in three groups of children: 1) HIV+ with growth retardation (HIV+ Gr); 2) HIV+ with normal growth (HIV+); and 3) HIV-uninfected with normal growth (HIV-). Twenty-six children between 2 and 11 y of age were studied (10 HIV+ Gr, 12 HIV+, 4 HIV-). All children were afebrile and free of acute infection during the study. Rates of WBPT (mean +/- SD) for the study groups were: HIV+ Gr, 12.2 +/- 4.8; HIV+, 10.7 +/- 5.1; and HIV-, 8.6 +/- 2.1 g.protein.kg-1.d-1 (NS, P > 0.05). Although not statistically significant, mean WBPT was 42% greater in HIV+ Gr, and 24% greater in HIV+ compared to HIV-. Statistically significant correlations were found between WBPT and Z scores for height (r = -0.39, P = 0.05) and weight-for-age (r = -0.51, P = 0.01) and dietary intake of protein (r = 0.39, P = 0.05), and between protein balance (synthesis-catabolism) and intakes of energy (r = 0.47, P = 0.02) and protein (r = 0.40, P = 0.04). There was no statistically significant correlation between WBPT and resting energy expenditure (r = 0.27, P = 0.19), or CD4 cell number (r = 0.05, P = 0.82). These data suggest an association between increased rates of protein turnover and low weight and height-for-age Z scores, and that it may be possible to achieve positive protein balance given an adequate intake of nutrients.

Ammonia↗

Design and statistical analysis for the Pathways study.

We report the design, rationale, and statistical procedures used in Pathways, a randomized, school-based intervention for the primary prevention of obesity in American Indian children. The intervention, which is now being implemented in 7 American Indian communities around the country, includes a health-promotion curriculum, a physical education program, a school meal program, and a family involvement component. Forty-one schools serving American Indian children were randomly assigned to be either intervention or control groups. The intervention will begin in the third grade and continue through the end of the fifth grade. Efficacy of intervention will be assessed by differences in mean percentage body fat, calculated by a prediction equation, between intervention and control schools at the end of the fifth grade. Power computations indicate that the study has power to detect a mean difference of 2.8% in body fat. Data analysis will use intention-to-treat concepts and the mixed linear model. The study will be completed in 2000.

Analysis of Variance↗

Body composition assessment in American Indian children.

Although the high prevalence of obesity in American Indian children was documented in several surveys that used body mass index (BMI, in kg/m2) as the measure, there is limited information on more direct measurements of body adiposity in this population. The present study evaluated body composition in 81 boys (aged 11.2+/-0.6 y) and 75 girls (aged 11.0+/-0.4 y) attending public schools in 6 American Indian communities: White Mountain Apache, Pima, and Tohono O'Odham in Arizona; Oglala Lakota and Sicangu Lakota in South Dakota; and Navajo in New Mexico and Arizona. These communities were participating in the feasibility phase of Pathways, a multicenter intervention for the primary prevention of obesity. Body composition was estimated by using a combination of skinfold thickness and bioelectrical impedance measurements, with a prediction equation validated previously in this same population. The mean BMI was 20.4+/-4.2 for boys and 21.1+/-5.0 for girls. The sum of the triceps plus subscapular skinfold thicknesses averaged 28.6+/-7.0 mm in boys and 34.0+/-8.0 mm in girls. Mean percentage body fat was 35.6+/-6.9 in boys and 38.8+/-8.5 in girls. The results from this study confirmed the high prevalence of excess body fatness in school-age American Indian children and permitted the development of procedures, training, and quality control for measurement of the main outcome variable in the full-scale Pathways study.

Adipose Tissue↗

Resting energy expenditure and body composition in children with HIV infection.

The purpose of this study was to determine whether alterations in body composition, resting energy expenditure (REE), and dietary energy intake are associated with growth retardation in HIV-positive children. Body composition (deuterium oxide dilution, skinfold measurements), REE (indirect calorimetry), and energy intake (24-hour weighed food intake) were evaluated in three groups: HIV-positive with growth retardation (HIV+Gr), HIV-positive with normal growth (HIV+); and HIV-uninfected with normal growth (HIV-). Children were between 2 and 11 years of age, afebrile, and free from acute infection. Forty-two children (13 HIV+Gr, 19 HIV+, 10 HIV-) were studied. Lean body mass was significantly reduced in HIV+Gr compared with HIV- (p < .05), and fat mass was significantly reduced in HIV+Gr and HIV+ compared with HIV- (p < .05). The percentages of lean and fat mass were not significantly different between groups, suggesting that differences in lean and fat mass were proportional to differences in body size. Consistent with reduced lean body mass, mean REE was significantly lower in HIV+Gr compared with HIV- (p < .05). Differences in mean REE/kg of body weight or lean body mass between groups were not statistically significant. A significant negative correlation was found between REE (kcal/kg/day) and weight-for-age (p = .04), and a trend with height-for-age Z-score (p = .07). Mean energy intake was not significantly different between groups. This study suggests that lean and fat mass are proportionately reduced in HIV-positive children with growth retardation. Further studies are necessary to delineate the relationship between energy balance and growth in children with HIV infection.

Adipose Tissue↗

Compartmental modeling of human lactation.

A difficult task for a novice modeler is beginning a modeling project. The methods described here delineate the modeling process step by step. Aristole is quoted as having said "One learns to play the flute by playing the flute," and the same principle holds somewhat for modeling. An excellent means for understanding modeling is to work with example models, altering rate coefficients and model structure, to learn first-hand the mechanics of the process. An excellent resource for viewing and downloading published models is the Library of Mathematical Models of Biological Systems, and can be accessed via the World Wide Web at the address http://gopher.dml.georgetown.edu/model/model.html++ + . This modeling library provides access to working models of biological systems. Experimenting with available examples of models, such as those presented in this volume and those available through the Modeling Library, provides an excellent opportunity for new modelers to get started in compartmental modeling.

Breast Feeding↗

Serum and plasma markers of nutritional status in children infected with the human immunodeficiency virus.

OBJECTIVE: To determine whether reduced serum or plasma protein and micronutrient levels are common in children infected with the human immunodeficiency virus (HIV) and whether these levels are different in children with growth retardation compared to those with normal growth. SUBJECTS: Children were separated into three groups: (a) HIV-infected with growth retardation (HIV + Gr); (b) HIV-infected with normal growth (HIV+); (c) HIV-uninfected with normal growth (HIV-). All children were afebrile and free of acute infection at the time of study. During a 24-hour stay in the Pediatric Clinical Research Unit, blood was drawn for analysis of total protein, albumin, zinc, selenium, and vitamin A levels; growth measurements were obtained; and dietary intake was assessed by 24-hour weighed food intake and 24-hour dietary recall. STATISTICAL ANALYSIS: Mean differences between groups were assessed by analysis of variance, and differences in the frequency of nutrient deficiency were determined by chi 2 analysis. RESULTS: Thirty-eight children between 2 and 11 years of age were studied: 10 HIV + Gr, 18 HIV+, and 10 HIV-. No statistically significantly differences were noted in mean levels of albumin, prealbumin, zinc, and selenium. Mean serum level of vitamin A was significantly higher in the HIV + Gr group than in the other two groups. There were no significant differences between groups in the frequency of deficiency for any nutrient studied. Mean energy and nutrient intake was similar among groups. APPLICATIONS/CONCLUSIONS: Abnormal serum or plasma protein or micronutrient levels were uncommon in this cohort of HIV-infected children, even in children with growth retardation. Routine monitoring of the level of proteins and micronutrients studied is unnecessary in the absence of specific clinical indicators of deficiency.

Biomarkers↗

High bone mass as a marker for breast cancer risk.

Postmenopausal women in the highest quartile for metacarpal bone mass were found to have an increased risk of developing breast cancer, after adjusting for age and other variables known to influence breast cancer risk. Although the mechanisms responsible for this relationship have not been identified, postmenopausal bone mass may serve as an indicator of cumulative estrogen exposure.

Bone Density↗