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Biomedical subjects

W C MacLean

Publications and source records attributed to W C MacLean.

At least 55 records · Page 3Linked to original sources
PubMed1980

Lactose malabsorption by premature infants: magnitude and clinical significance.

Sequential studies of breath hydrogen excretion in response to lactose feeding were carried out in 22 premature infants during the first seven weeks of life. Seventy-five percent of infants excreted H2 in breath during the first two weeks, 100% by the end of the third week. The peak H2 concentration and the five-hour mean breath H2 excretions were significantly related to lactose intake per day, lactose intake per feeding and postnatal age, though only lactose intake per day remained significant when all three variables were included in multiple regression analysis. Preprandial breath H2 concentration was inversely related to the frequency of feeding. Using the five-hour mean H2 excretion, it was estimated that 66% or more of ingested lactose entered the colon and was fermented. Throughout the studies stool patterns and rates of weight gain of the infants were normal. Premature infants normally malabsorb substantial amounts of lactose. The elevation of breath H2 in these infants apparently represents a successful adaptation of the colonic microflora to this physiologic malabsorption and should not be cause to modify the diet of an infant who is clinically well.

Humans↗
PubMed1980

13C abundances of nutrients and the effect of variations in 13C isotopic abundances of test meals formulated for 13CO2 breath tests.

Unlike 14CO2 breath tests, 13CO2 breath tests are performed in the presence of a large background of naturally occurring isotope. Because the exact abundance of 13CO2 in breath can be changed by variations in diet, a study of the 13C abundance of dietary constituents and their effects on breath 13CO2 has been undertaken. Dietary constituents have been combusted to CO2 and the relative abundance of 13C analyzed by mass spectrometry. Breath CO2 was collected and isotopically analyzed after the ingestion of several dietary constituents and test meals. The 13CO2 abundance of breath CO2 was shown to change in response to the 13C abundance of the substrate being oxidized. Conversely, a test meal that closely approximates the 13C abundance of fasting breath CO2 from North Americans was shown not to alter the 13CO2 abundance in breath. Investigation of the breath 13CO2 response to individual 13C-labeled dietary constituents demonstrated that amino acids produced the earliest 13CO2 response followed in order by medium chain triglycerides, carbohydrates, and long chain triglycerides. Because of the variation in 13C abundances in nature, the 13C abundance of any unlabeled substrate ingested during a 13CO2 breath test must be considered in order to eliminate artifacts that may reduce the sensitivity of the breath test or produce erroneous results. Methods for correcting breath tests for changes in background 13CO2 abundance are also discussed.

Adult↗
PubMed1980

Urban-rural differences in the growth of Peruvian children.

The growth characteristics of children from four villages in northern Peru were compared with those of poor urban children in the capital city, in whom short stature but generally satisfactory weight for height relationships after infancy had been demonstrated. Height for age and weight for age fell more rapidly during infancy in the rural than in the urban children of both sexes. Rural girls caught up with the urban girls in height during childhood but did not match them in weight until late adolescence. Their weight to height ratios were consistently lower after 1 year of age, most strikingly between 2 and 5 years of age, and did not approach or match those of the urban girls until adolescence. Rural boys did not catch up with the urban boys in height or weight (differences in height were not statistically significant between 6 and 10 years, however) and their ratios remained consistently lower until late adolescence, most strikingly in early childhood and during puberty. Such urban-rural and sex differences, if typical and current, might well call for very different remedial measures at different ages in each of the populations.

Adolescent↗
PubMed1980

Nutritional value of normal, opaque-2 and sugary-2 opaque-2 maize hybrids for infants and children. 1. Digestibility and utilization.

The opaque-2 (o2) gene increases the lysine and tryptophan contents of maize and its protein quality; the sugary-2 (su2) gene improves vitreousness and density but decreases lysine; the double-mutant surgery-2 opaque-2 (su2o2) has the improved kernel characteristics and an even higher protein quality than opaque-2. Digestibility of energy and protein, and protein quality of normal, o2 and su2o2, both as endosperm (E) and whole kernel (WK) meals, were studied in eight convalescent malnourished children, 10--25 months of age. Diets provided 100--125 kcal/kg/day, 10% fat, with all of 6.4% protein calories from one of six maize meals or casein. Endosperm meals provided 83.2, 91.2 and 82.1% of energy, WK meals 73.2, 68.6 and 67.2% of energy in respective diets. Apparent N retention from E meals was lower than from WK meals, both lower than from casein. For each type of meal (E and WK) there was strong correlation between lysine "absorbed" and N retention, but this was higher from WK at equal lysine intakes. For 50% of children to match N retention from casein, presumably equal to requirement, they would have to consume 203.9, 148 or 122.5% of energy requirement as normal, o2 or su2o2 E meals, obviously impossible. For WK meals, they would have to consume 108.2, 90.3 or 84.2% of energy as normal, o2 or su2o2.

Child, Preschool↗
PubMed1980

Utilization of the protein and energy of the white potato by human infants.

The digestibility and protein quality of the white potato were studied in 11 infants, ages 8-35 months, recovering from malnutrition. Seven 9-day dietary periods comprised the study. Digestibility was assessed by metabolic balance during the last 6 days of dietary periods in which potato provided 25%, 50% or 75% of dietary energy. Casein-based control dietary periods preceded and/or followed each potato dietary period. Fecal wet and dry weights, fecal energy, computed fecal carbohydrate and fecal fat during consumption of the 25% potato diet did not differ from control. Analysis of variance showed that consumption of increasing amounts of potatoes produced a significant linear increase in all parameters of digestibility except fecal fat. Fecal wet weight and energy content during the 75% potato period were more than double control values. Regression analysis of data from potato dietary periods showed fecal wet weight to be an excellent predictor of fecal dry weight (r = 0.904), energy content (r = 0.785) and computed fecal carbohydrate (r = 0.770). Protein quality of potato was assessed with N balance studies during the dietary periods in which potato provided all dietary protein (approximately 5% protein kcal). Apparent N retention was 78% of that from an isonitrogenous casein control diet. Decreased apparent N absorption was primarily responsible for the difference; the "biologic value" (percent of absorbed N that was retained) was similar for both diets.

Caseins↗
PubMed1979

Nutritive value of brown and black beans for infants and small children.

A precooked, instantized mixture of brown and black beans, with and without 0.3% DL-methione added, served as the only source of protein in the diets of 10 recovered malnourished infants and children 10 to 42 months of age. At 6.4 to 5.7% dietary protein calories stool wet weights were twice as high, apparent N absorption significantly lower (65.6 +/- 5.9 versus 87.5 +/- 2.3% of intake), and apparent N retention much lower (9.8 +/- 6.1 versus 34.5 +/- 10.2% of intake) than during preceding and following isocaloric and isonitrogenous casein-based diets. The addition of methionine resulted in minimal improvement in N retention and a highly suggestive increase in fasting plasma free methionine. Prolonged feeding of the methionine-enriched beans at 8.0 to 10.9% protein calories supported satisfactory growth and serum albumin levels in two of three children, not so in the smallest one, in whom repeated balance studies demonstrated no decrease over time in stool wet weight and on marginal improvement in N absorption and retention. The poor digestibility of the protein in these beans is the first-limiting factor in its utilization by infants and small children.

Caseins↗
PubMed1979

Growth standards for poor urban children in nutrition studies.

In order to estimate the importance of a variety of environmental and dietary factors as determinants of growth in a group of 123 poor Peruvian urban children between 2 and 19 years old, we found it necessary to express anthropometric measurements in units that were not age- or sex-dependent. Height quotient and weight quotient for each child were calculated from height and weight ages derived from the 50th percentile of the Boston reference data for the appropriate sex. Only 5% of the children had heights above the Boston 50th percentile (height quotient greater than 100) and 18% had weights above the 50th percentile (weight quotient greater than 100), but 88% had weights that were appropriate or excessive for height (weight/height quotient greater than or equal to 1.00). Some CATch-up" gains in relative height and weight were apparent in preschool children but more impressive gains in both linear and ponderal growth, relative to the Boston data, were evident between 8 and 13.5 years in girls and 10 and 17 years in boys. When the same quotients were calculated for a much larger sample from the same socioceonomic level it seemed likely that this last peak was due to earlier puberty and sexual maturation, and that quotients derived from the Boston data would have different meanings at different ages, making them inappropriate for further statistical analysis. New quotients for the study population, derived from the larger Peruvian group, did not have sex- or age-dependent trends. Racial and regional differences in patterns of growth must be taken into account in the interpretation of anthropometric and nutritional data.

Adolescent↗
PubMed1979

Effect of an episode of severe malnutrition and age on lactose absorption by recovered infants and children.

The degree of which the ability to absorb lactose can be regained after recovery from an acute episode of severe malnutrition is in doubt. Lactase activity was indirectly assessed by means of a standard lactose tolerance test (2 g lactose per kilogram of body weight) in 71 Peruvian Mestizo infants and children (age 5 to 55 months) who had suffered such an episode. All were studied just before discharge after several months of hospital rehabilitation, during which linear growth and weight gain had accelerated and signs of significant malabsorption of other nutrients had disappeared. Only 39% of the total group had a positive test (delta blood glucose greater than 25 mg/dl); there was a decreasing proportion of positive responders with increasing age. No difference in response attributable to type or severity of malnutrition was found. Comparison of the present data with previous data from children in the same community who had never been acutely malnourished suggests that acute malnutrition may hasten the permanent decline of lactase activity normally expected later in life.

Acute Disease↗
PubMed1978

Total management of short gut secondary to midgut volvulus without prolonged total parenteral alimentation.

Absorption studies in rats have shown that intestinal adaptation after catastrophic injury can be stimulated by early enteral feeding. Using this concept, we have devised a technique of early initiation and advancement of oral feedings that begins with Cho-Free and Polycose and gradually adds sucrose and MCT in increasing proportions. The increasing complexity and caloric density of this diet provide sufficient nutrition to allow weaning from total parenteral alimentation within 2--3 wk. Our preliminary experience in babies with midgut volvulus, necrotizing enterocolitis, and gastroschisis has been successful and uncomplicated. These patients have demonstrated consistent weight gain and have been spared the complications associated with prolonged parenteral alimentation.

Animals↗