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Biomedical subjects

L H Allen

Publications and source records attributed to L H Allen.

At least 55 records · Page 3Linked to original sources
PubMed1994

Iron, vitamin B-12 and folate status in Mexico: associated factors in men and women and during pregnancy and lactation.

To determine the prevalence and causes of anemia in rural Mexico, blood samples and longitudinal dietary data were collected from 187 women, some pregnant and then lactating, and from 72 men. Blood was used to measure anemia, mean cell volume, and plasma ferritin, folate and vitamin B-12. Anemia was found in 33% of the men, 54% of nonpregnant, nonlactating women, 35% of pregnant women and 41% of lactating women, and varied by season. Low iron stores (ferritin) accompanied anemia in only 8% of men compared with 38-67% of women. Low meat intake and poor dietary iron bioavailability were associated with anemia in women. There were no cases of low plasma folate. Low plasma vitamin B-12 was common in all groups, and the incidence increased from 15% at 7 mo of pregnancy to 30% at 7 mo of lactation. Vitamin B-12 was lower in the plasma and milk of anemic lactating women than in plasma and milk of non-anemic lactating women and was classified as deficient in 62% of breast milk samples.

Adult↗
PubMed1994

Maternal body mass index and pregnancy outcome in the Nutrition Collaborative Research Support Program.

This paper uses data from the Nutrition CRSP in Egypt, Mexico and Kenya to examine relationships between maternal BMI and pregnancy outcome. Women were studied from the periconceptional period up to 6 months of lactation. No women in Egypt or Mexico, and only two in Kenya where periods of food shortage occurred, had a BMI < 18 at conception. Women with a lower BMI in Mexico and Kenya gained more weight and fat in pregnancy and lost more weight and fat during lactation. These counter-intuitive relationships affect the interpretation of weight and body composition measures used to assess energy adequacy during pregnancy and lactation. Lower pre-pregnancy BMI predicted lower infant weights at birth and was a risk factor for low birthweight in Kenya. At 3-6 months post partum, maternal BMI was less strongly related to infant size, and the lean body mass component of BMI appeared to be a more important predictor than fatness.

Adult↗
PubMed1994

Nutritional influences on linear growth: a general review.

The first section of this paper reviews what is known about the roles of specific nutrients in the general linear growth faltering that occurs in developing countries. Those reviewed are energy, protein, zinc, iron, copper, iodine and vitamin A. For none of these nutrients was there clear, consistent evidence that supplementation with the nutrient benefited linear growth. Rather, interventions with each specific nutrient had a positive effect on length gain in some studies, while in others these affected only weight gain or had no effect. Reasons for these conflicting results are suggested, including the strong probability that growth is limited by multiple, simultaneous deficiencies in many populations. This point is illustrated with data from the Nutrition Collaborative Research Support Program (CRSP) and other reports. Most interventions with single nutrients have been tested on children older than the age when linear growth faltering is most rapid, that is, within a few months of birth. Possible reasons why growth stunting begins so early in life are presented, but these are mostly hypothetical because of the paucity of information on this topic.

Body Height↗
PubMed1994

An animal model studying reconstruction techniques and histopathological changes in repair of canalicular lacerations.

We designed an animal model using sheep to evaluate three methods of canalicular reconstruction after laceration: direct sutured reapposition of the canaliculus without silicone intubation (4 eyelids), silicone intubation of the canalicular system without mucosal anastomosis (14 lids) and silicone intubation with mucosal anastomosis (10 lids). We also wished to determine the appropriate time of silicone tube removal. In the canaliculi repaired using silicone intubation the tubes were removed at 4, 8 or 12 weeks. Patency of the canalicular system was assessed at 16 weeks by probing. Sections of eyelid tissue were examined histopathologically to confirm patency and to compare the tissue alteration caused by the various methods of repair. We found that silicone intubation was necessary to reestablish patency of the canaliculus and that silicone intubation with and intubation without mucosal anastomosis were equally efficacious in restoring canalicular patency. The optimum time for removal of the tube was 12 weeks. Histopathologically, all canaliculi found to be patent by probing demonstrated mucosal continuity along the canalicular lumen.

Anastomosis, Surgical↗
PubMed1993

High fiber diets slow bone turnover in young men but have no effect on efficiency of intestinal calcium absorption.

Dietary fiber reduces the absorption of dietary calcium from a meal, but its impact on calcium kinetics is unknown. We therefore evaluated the effects of a high fiber diet on calcium balance and kinetics and on calcium-regulating hormones. Seven young men each participated in two 23-d experiments. In the low fiber period the controlled diet provided 6.5 g fiber/d and 530 mg calcium/d. In the high fiber period fiber was increased to 31.3 g/d and calcium to 586 mg/d by substituting high fiber cereal. Measured between d 7 and 12 of each period, the high fiber diet significantly lowered the apparent absorption of calcium (from 60.6 +/- 23.8% to 37.1 +/- 26.5%) and reduced calcium balance, although balance remained positive overall. Fiber had no effect on serum total or ultrafiltrable calcium, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D or parathyroid hormone concentrations measured on d 1, 7, 12 and 20. Calcium kinetics was studied between d 17 and 23 by administering oral 44Ca and intravenous 42Ca to fasting subjects. Fractional absorption of calcium in the fasting state was unaffected by fiber. However, during the high fiber period, subjects had significantly lower bone accretion, resorption and turnover rates, and calcium flow to bone from the exchangeable pool than during the low fiber period. We conclude that the fiber-induced reduction in calcium absorption slowed down bone calcium turnover but did not increase the efficiency of intestinal absorption.

Adult↗
PubMed1993

Iron-deficiency anemia increases risk of preterm delivery.

In an inner-city sample of pregnant women, iron-deficiency anemia was associated with a higher risk of preterm delivery and low birth weight but not with small-for-gestational-age births. However, the prevalence of iron-deficiency anemia (3.5%) explained only a small proportion of preterm deliveries.

Adolescent↗
PubMed1993

The nutrition CRSP: what is marginal malnutrition, and does it affect human function?

This review of the Nutrition Collaborative Research Support Program (Nutrition CRSP) describes the results of a longitudinal study of the effects of marginal malnutrition on human function in Egypt, Kenya, and Mexico. Growth-stunting occurred soon after birth and was associated with cognitive and behavioral deficits in infancy and childhood. Maternal nutritional status was implicated in this phenomenon. All three population groups had poor dietary quality and multiple micronutrient deficiencies, which were associated with poor function. Energy deficiency was a problem only in Kenya.

Adult↗
PubMed1992

Bioavailability of energy, nitrogen, fat, zinc, iron and calcium from rural and urban Mexican diets.

The availabilities of nutrients from a representative rural Mexican diet (RMD) and a representative urban Mexican diet (UMD) were evaluated by balance experiments in sixteen Mexican women. Compared with UMD, the plant-based RMD led to a higher number of defaecations and higher faecal excretion of dry matter, fat, nitrogen and energy. Apparent digestibility of N from RMD was only 67% compared with 90% from UMD. N balance was 0.4 and 2.6 g/d with RMD and UMD respectively (P < 0.001). Apparent digestibility of energy was 89 and 95% from RMD and UMD respectively (P < 0.001). Calculation of the metabolizable energy (ME) using Atwater's (Atwater & Bryant, 1900) general factors overestimates the determined ME in RMD by 8%. The Food and Agriculture Organization/World Health Organization/United Nations University (World Health Organization, 1985) recommended factors for correction of digestibility of fibre intake overestimate energy and protein absorption from RMD. The diets provided similar amounts of zinc, and its apparent absorption from RMD was 0.5 mg/d (4.6%) and its balance was 0.1 mg/d. This compared with values for UMD of 1.6 mg/d (16%) and 1.2 mg/d respectively. Iron intake was higher from RMD (17.4 v. 11.6 mg/d; P < 0.01), but apparent absorption was 17 v. 35% and balance was 2.7 and 3.8 mg/d (P < 0.001) for RMD and UMD respectively. RMD also contained more calcium (745 v. 410 mg/d) but apparent absorption from RMD was negative (-136 v. 15 mg/d) and balance was more negative (-197 v. -77 mg/d; P < 0.05). Thus, the content of these minerals is not low in the rural diet but their bioavailabilities are poor.

Adolescent↗
PubMed1992

The interactive effects of dietary quality on the growth and attained size of young Mexican children.

Predictors of attained size at 30 mo and growth rate between 18 and 30 mo (eg, diet, maternal size, morbidity, age at weaning, and selected environmental factors) were investigated by using longitudinal data from 67 Mexican children aged 18-30 mo. These children were small because of growth stunting in early infancy. Between 18 and 30 mo they grew on average at the 50th percentile of National Center for Health Statistics references values for weight, and the 25th for length. Size at 30 mo and growth rates were unrelated to energy or protein intakes during the previous year, but positively related to consumption of animal-origin foods. Maternal weight predicted size and growth only for children with larger intakes of animal products. Individual rates of weight and length growth were uncorrelated on average, correlated negatively when animal-product intake was low, and positively only when more animal products were consumed. Integrated weight and length growth, and the influence of maternal size on growth, may be disrupted by poor dietary quality. Different children would be identified as malnourished depending on whether weight or length growth was measured.

Analysis of Variance↗
PubMed1992

An ocular dynamic study supporting the hypothesis that hypothyroidism is a treatable cause of secondary open-angle glaucoma.

To examine the hypothesis that glaucoma may be a manifestation of unrecognized hypothyroidism, we studied 25 consecutive patients with newly diagnosed hypothyroidism who presented to an endocrinology clinic. Using tonography and tonometry, we demonstrated a reduction in facility of outflow in the hypothyroid state. With treatment of the hypothyroidism alone there was a statistically significant improvement in facility of outflow, intraocular pressure and Po/C (p < 0.002). Our results support the hypothesis that secondary open-angle glaucoma may be a manifestation of hypothyroidism and that the glaucoma will resolve on treatment of the primary disease.

Adolescent↗
PubMed1992

Reversal of poorly controlled glaucoma on diagnosis and treatment of hypothyroidism.

Hypothyroidism was diagnosed in a 62-year-old woman with poorly controlled primary open-angle glaucoma, including a disc hemorrhage and a documented arcuate scotoma. After 1 year of thyroxine therapy the glaucoma was easily controlled, pilocarpine treatment was stopped and the visual fields were completely normal. To our knowledge this is the first report in the modern literature of reversal of open-angle glaucoma with treatment of hypothyroidism.

Female↗
PubMed1992

Lactose digestion from unmodified, low-fat and lactose-hydrolyzed yogurt in adult lactose-maldigesters.

The efficiency of carbohydrate absorption from two unmodified plain yogurts, a low-fat yogurt and a yogurt produced from lactose-hydrolyzed milk, was compared using the breath hydrogen response in 14 lactose-maldigesters. The maldigesters showed symptoms of intolerance to a standard 360 ml glass of milk containing 18 g lactose. Compared to intact milk, the breath hydrogen response to two varieties of unmodified yogurt and the lactose hydrolyzed yogurt was severely attenuated while the hydrogen response to low-fat yogurt was intermediate. Intolerance symptoms were significantly and equally reduced with all four yogurt products compared to milk. Ten lactose-digesters had a significantly greater efficiency of lactose digestion with 360 ml of milk than the 14 maldigesters; however, except for the magnitude of the maximum rise in breath H2, no inter-group differences were observed in response to unmodified yogurt. We conclude that lactose prehydrolysis adds nothing to the ability to tolerate and digest plain, full-fat yogurts, but it may be useful with low-fat or pasteurized varieties.

Adult↗
PubMed1991

A microprocessor-regulated constant voltage, current, wattage, and temperature electrophoresis power supply.

The analog control circuitry typically found in commercial electrophoresis power supplies was replaced by a digital microcomputer. Analog to digital converters were used to monitor the voltage applied to and current passed through an electrophoresis cell. Microcomputer programming was employed to compare converter input values with preselected operating parameters and then calculate a required output voltage. Timing sequences were generated through programming utilizing clocks located on the interface boards. A digital to analog converter was employed to apply a control voltage to a constant voltage power supply. This process was completed at least 20 times each second. BASIC programming subroutines were written to maintain constant voltage, current, power (wattage), and temperature. To these operating procedures, other techniques such as automated endpoint detection of isoelectric focusing and pulsed waveform outputs were easily added. This power supply containing a microcomputer system as the feedback element was shown to have a greater stability and versatility than conventional supplies.

Blood Proteins↗
PubMed1991

Household size, food intake and anthropometric status of school-age children in a highland Mexican area.

Large household size is widely regarded as a risk factor for malnutrition in developing countries, particularly for infants and young children. This study examines the extent to which household size is related to nutritional status in school-age children in the Solis Valley in highland Mexico. The relationships of food intake, anthropometric measures, and household size are assessed in a sample of 110 children (7-9 years of age), who were followed longitudinally for a minimum of one year as part of the Collaborative Research Support Program on Food Intake and Human Function. Diets in the valley are characterized by very low intake of animal food products and are heavily dependent on maize, which is primarily home-produced. Growth faltering is pervasive; the mean Z score for height-for-age in the sample is--1.6 of the NCHS reference standard. Children from larger households are significantly shorter and consume diets of poorer quality, as assessed by intake of foods from animal sources. These relationships remain statistically significant in regression analyses that control for household economic status. It therefore appears that the resources available to households in the Solis Valley are inadequate to buffer children in even more advantaged households from the stresses of maintaining large families.

Anthropometry↗