Effectiveness of the Body Mass Index in the nutritional diagnosis of pregnant adolescents

The purpose of this study was to analyze the diagnostic capacity of different classification criteria based on Body Mass Index in the assessment of nutritional status and to evaluate their effectiveness. The sample comprised 367 healthy pregnant adolescents in their first trimester of gestation, from a socioeconomic level IV, between Oct. 1999 and Dec. 2008. Two methodologies were applied for the nutritional classification: (1) Integral nutritional diagnosis (gold standard), and (2) Body Mass Index (BMI), using local reference values: Proyecto Venezuela and the Transversal Study of Caracas, and international reference values: Frisancho and WHO 2006. Concordances, kappa, sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and the Youden index were calculated. According to the gold standard and BMI, the percentage of well-nourished pregnant women ranged between 62.4% and 80.6%. Within the deficit range, Frisancho was the most effective with kappa: 0.80; sensitivity: 87.3%; specificity: 94.8%; positive likelihood ratio: 16.9, and negative likelihood ratio: 0.13; Youden index: 0.82. Within the excess range, Frisancho and the Transversal Study of Caracas were the most effective with Youden index: 0.86 and 0.83, respectively. These results revealed that Frisancho was the best criterion to diagnose malnutrition in deficit in pregnant women. All references have an adequate diagnostic capacity for the excess range, of which Frisancho and the Transversal Study of Caracas are the best. We recommend using such reference values to optimize the efficiency of the BMI indicator in diagnosing malnutrition in deficit and in excess in the first trimester of gestation in pregnant adolescents within populations with similar characteristics.     

Food habits and culture factors in pregnant adolescents

The purpose of this study was to identify the food habits of pregnant adolescents and their perception about which, of her cultural concepts, have higher influence. 54 subjects between 12 and 19 years old from Guadalajara City were included and socioeconomic, dietetic data, as food frequency consumption and cultural concepts about feeding were also explored. Chi square was used for identifying association between variables. The fat intake was lower in late vs. Early and middle stage of adolescence (57 vs. 71 g/d, p = 0.05). The iron, calcium and zinc intake was also deficient in the early/middle stage; meanwhile, the folic acid consumption was very low in the late stage of adolescence. Corn tortillas were the most consumed cereal and food (93-96%); junk food and sodas (62 and 55%) prevailed in the early/middle stage. About local costumes, "tacos", "pozole" and burgers were the most referred (74.1%). They also mentioned that fat (36.7%), junk food (30%), chili (26.7%), sodas (23.3%), processed meals (26.7%) and salt (10%) were harmful. They also believed that vegetables (77%), fruits (60 %), milk (21%), broths (17%), and meat (12.5%) were beneficial; and, 96% considered that chicken and bean broths were nutritious (myth). There were some prohibited foods (taboos) during pregnancy: chili (48%), junk food (20%), and salt (16%). Prejudices were more common among later adolescents (60.9%) (p = 0.03). The erratic food habits and the conceptual confusion of these adolescents cause a low intake of nutrients and place them in a nutritional risk.     

Effectiveness of body mass index in the nutritional diagnosis of pregnant women

Our goal was to analyze the concordances and non-concordances of the nutritional classification in pregnant women and to evaluate their effectiveness when different BMI classification methodologies were applied. The study consisted of 314 adult healthy pregnant women in their first trimester, of socioeconomic status IV. In all of them, two nutritional classification criteria were applied: the integral nutritional diagnosis (IND) and different BMI reference values (Institute of Medicine, FAO/OMS, Frisancho, Bray, and Atalah). Kappa, concordance and nonconcordance, sensitivity, specificity, positive and negative predictive values were calculated. The highest frequency of concordance between IND and the analyzed classification criteria in comparing four and three nutritional categories was Frisancho's with the following results 89.2%, Kappa = 0.81 in the first case, and 91.4, Kappa = 0.84 in the second case. In deficit, the Bray and Atalah classification criteria were the highest sensitivities. In excess, FAO/ OMS, Frisancho, and Bray had a high sensitivity (1 - 0.99). Frisancho, in addition, had a high specificity with respect to FAO/OMS and Bray. Frisancho's classification criteria are the best choice for diagnosing adult pregnant women's nutritional status during the first trimester within population groups with these characteristics.     

Plasma amino acids profile of healthy pregnant adolescents in Maracaibo, Venezuela

One hundred female adolescents (13-18 y) were clinical and anthropometrically studied to select only those with adequate nutrition. Most adolescents belonged to IV socio-economic stratum families (worker class). Height, weight, age, body mass index and medial arm circumference were used as anthropometric parameters. After screening, only 41 non pregnant girls (control) and 42 pregnant girls with adequate nutrition were selected to analyze plasma amino acids. Fasting peripheral venous blood was drawn, and plasma amino acids were analyzed by HPLC. Amino acid concentrations were expressed as umol/L +/- SE. SAS/STAT program was used for statistical analysis. Amino acid values of control adolescent group were found in ranges reported by other investigators, with slight variations, mostly in diminution, presumably due to nutritional, metabolic or genetic conditions of people living in tropical regions. In pregnant healthy adolescents, distributed according to gestational age: < 32 weeks (n = 30) and > 32 weeks (n = 12), a diminution of total molar plasma amino acids was found, by comparing with control values. Ten amino acids (Pro, Gly, Gln, Arg, Ser, Orn, Tau, Leu, Thr and Val) appeared significantively diminished throughout gestation, being Gly. Gln and Arg most affected since earlier weeks. During the 2nd period. Thr and Val increased their grade of affectation; whereas some amino acids values (Orn, Pro and Tau) tended to recuperate. Several of affected amino acids are gluconegoenic, thus, they could be utilized to supply the energy required by the pregnant adolescent against her double stress: the fetus development and her own development. The plasma amino acid values reported in both, healthy non pregnant and pregnant adolescents, could be taken as regional referential profile of plasma amino acids in this poblational group for further research on adolescent and fetal--maternal malnutrition.     

The effectiveness of anthropometric indicators in the nutritional diagnosis of well-nourished and undernourished pregnant women

The objective was to evaluate the effectiveness of the indicators prepregnancy weight and prepregnancy body mass index in the categorization of the nutritional state of the pregnant woman. The study group was formed by 109 pregnant women. They were evaluated in the first trimester of the pregnancy, at the "Centro de Atención Nutricional Infantil Antímano". In each one of them the nutritional state was classified according to three criteria: integral nutritional diagnosis, prepregnancy weight and prepregnancy body mass index. For the evaluation of the effectiveness of the diagnostic criteria, the other two approaches were compared with the integral nutritional diagnosis. The analysis of the frequency, sensibility, specificity and predictive values were applied. The integral nutritional diagnosis showed: 75.2% (n = 82) well-nourished and 14.8% (n = 27) undernourished. The sensibility of the prepregnancy weight was 0.93 and of the prepregnancy body mass index was 0.52, with a positive predictive value of 0.60 and 0.82 respectively. The specificity of the first indicator was 0.79 and of the second was 0.96, with negative predictive value of 0.97 and 0.86 respectively. The pregnancy weight demonstrated to be effective to diagnosis undernourished women.     

Dietary evaluation of pregnant adolescents during first, second and third trimester

In order to identify risk of inadequate intake of calories and nutrients during pregnancy, 75 pregnant adolescents (14 to 18 years old) apparently healthy, from low socioeconomic level, in their first prenatal control (12 weeks) were studied by two 24 hour recalls and a food frequency questionnaire at each trimester. Nutritional status was assessed by body mass index (pregestation weight/height) and classified according to American Medicine Institute reference. Paired t-test, frequency distribution and ANOVA were used for statistical analysis. Low weight was found in 34.6% of adolescent at the first visit and 5.3% were overweight. Even though, caloric intake was below recommendation, significant increases were observed between first and second trimester for energy, carbohydrates, niacin and zinc (p < 0.001) and for fat, proteins, riboflavin, thiamin, vitamin C, calcium and iron (p < 0.05). From second to third trimester, differences (p < 0.05) were significant only for vitamin A. Between first and third trimester, differences were significant (p < 0.05) for energy, proteins, carbohydrates, niacin, riboflavin, zinc and for thiamin, vitamin A and calcium (p < 0.05). A high proportion of pregnant adolescent did not reach recommendations for energy, folate, calcium and zinc. Food intake pattern did not change significantly among trimesters. Mean total weight gain was 9.2 kg and 0.412 +/- 0.4 g/week. Newborn's mean weight was 3.221 +/- 418 grams. It is concluded that adolescents are at high nutritional risk and deficiency of dietary intake should be followed. Attention should be addressed from the preconceptional period to postpartum in order to improve maternal and fetal conditions.     

Lean adolescents with increased risk for metabolic syndrome

The aim of the present study was to determine in adolescents the relationship between insulin levels and body mass index (BMI), body fat distribution, diet, life style and lipid profile. We studied 167 adolescents (68 boys and 99 girls) whose ages ranged from 14 to 17 years. A detailed medical (including pubertal stage) and nutritional record was obtained from each subject. Biochemical measurements included fasting serum insulin, glucose, total cholesterol (TC), triglycerides (Tg), HDL-C, LDL-C and VLDL-C. HOMA insulin resistance (IR) and HOMA beta-cell function (beta-cell) were calculated. Insulin levels were over 84 pmol/L (cut off normal value in our lab) in 56% of the boys and 43% of the girls. Thirty-seven percent of lean adolescents whose BMI was 21.5 +/- 1.9 kg/m2 presented higher fasting insulin levels. HOMA IR, Tg, systolic (SBP) and diastolic blood pressure (DBP) values when compared to a lean normoinsulinemic group. Insulin levels were correlated (p < 0.01) with body mass index. Both boys and girls in the highest BMI quartile (BMI > 24 kg/m2) had significantly higher serum insulin, HOMA beta-cell, and Tg levels, and the lowest HDL-C levels. A high-energy intake rich in saturated fat and low physical activity were found in this lean but metabolically altered adolescents. We conclude that even with a BMI as low as 21 kg/m2 an inappropriate diet and low physical activity might be responsible for the high insulin levels and dislipidemias in adolescents.     

Effects of nutritional copper deficiency on adult non-pregnant and pregnant rats and their newborns.

The effects of nutritional copper deficiency on weight gain, food intake and fertility of pregnant and non-pregnant adult Wistar rats, and weight of newborns, were studied. The adult animals were subjected to diets with different copper content (control-5 ppm; moderate deficiency -1.2 ppm; severe deficiency -0.3 ppm) for six weeks (non-pregnant) and nine weeks (pregnant). No effect on weight gain or appetite was seen in the groups of animals subjected to copper deficiency. Fertility, as evaluated by the number of conceptuses and liverborns of the pregnant animals, and weight of newborns also, were not impaired. These data show that not only the extent of deficiency, but also the period during which it is imposed, as well as its duration, condition the appearance of alterations of this deficiency.     

Secular trends in growth in male adolescents: height and weight gains, nutritional state and relation with education

This work aimed at characterizing the modifications in adolescents nutritional status, growth evolution and education along time and the correlation with the height, weight and body mass index. Data came from 2616 male adolescents soldiers between 17 and 19 years old enlisted for Armed Services in the city of Vi?osa-Minas Gerais, Brazil, between 1995 and 2004. There was a positive secular trend for height and weight, with a 4cm and 3kg median increment, respectively, along time. There was a reduction from 28.0% to 11.6% on the prevalence of short stature in the period. It was estimated positive correlation (p < 0.05) between education and stature, weight and BMI. The prevalence of weight excess (risk of overweight and overweight) increased from 7.1% (1995) to 9.1% (2004). Although it was observed positive secular trend for stature and weight, it was not sufficient to reach the median of the National Center for Health Statistics/Center for Disease Control and Prevention. Weight excess and short stature prevalence must be monitored, being necessary the implementation of measures that focus to prevent these disturbance and aim at reaching or maintaining an adequate nutritional state for future generations.     

异型材挤出中应力应变问题

通过对实际生产过程中经常出现的型材弧面以及应变收缩等问题 ,结合笔者多年模具设计、调试的经验 ,提出了解决办法。结果表明 :异型材生产过程中的关键是模具定型模的设计。     

粉煤灰在油田开发中的应用

在对某热电厂粉煤灰的粒度、化学成分、水化性等性能分析的基础上，介绍了一种以粉煤灰为主剂的水井用调剖剂。经室内实验分析和现场应用的效果分析，证明FP-2型粉煤灰类调剀剂的堵水调剖效果好，为粉煤灰的综合利用找出了一条新的应用途径。     

粉煤灰在油田开发中的应用

在对某热电厂粉煤灰全面的性能分析的基础上,介绍了一种以粉煤灰为主剂的水井用调剖剂。经室内实验分析和现场应用的效果分析,证明FP-2型粉煤灰类调剖剂的堵水调剖效果好,为粉煤灰的综合利用找出了一条新的应用途径。     

A nutritional evaluation of acetostearins in rats

A modified glyceride, acetostearin, has been studied in feeding experiments with rats using several nutritional and biochemical criteria. As acetostearins are more readily absorbed than the standard fats from which they are prepared, it was possible also to study the effect of high levels of saturated fat on essential fatty acid utilization. The retarded growth and poor survival of acetostearin-fed animals indicate the possibility of antagonism of the acetostearins to essential fatty acid utilization. The decreased plasma cholesterol levels and elevated liver cholesterol values observed in the acetostearin-fed animals appear to be due mainly to essential fatty acid deficiency. High cholesterol levels in the adrenals show some indication of the involvement of caloric insufficiency in cholesterol metabolism of acetostearinfed rats. Therefore, the probable explanation of the poor nutritional performance of rats fed acetostearin is a combination of essential fatty acid deficiency and caloric insufficiency.     

异型材挤出口模内的流动模拟

本文根据挤出机理，对口模内的流动行为进行适当的简化和假定，建立了挤出口模内流动分析的数学模型，并采用横截面／假想区域法实现了复杂异型材挤出口模内的数值模拟，数值分析结果与三维有限元解和解析解的对比，取得了满意的效果。     

井眼循环温度分布规律

结合实际运用分析各种井内温度确定方法，并根据能量守恒的原理，结合传热学和流体力学的基本原理，建立了相应的井眼内温度数学模型和确定任意时刻、井深处的钻具内和环空中的温度值的计算公式。     

塑料异型材挤出模中的压力分布

本文对塑料异型材挤出模机头典型流道结构进行了分析，给出了各种类型流道的压力降计算公式，并用一实例说明文中所述方法的正确性。