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Biomedical subjects

C Garza

Publications and source records attributed to C Garza.

At least 73 records · Page 4Linked to original sources
PubMed1988

Body volume and fat-free mass determinations by acoustic plethysmography.

An acoustic plethysmograph designed to measure body volumes of infants is described. This method uses the principle of the Helmholtz resonator in which the resonant frequency of a chamber is inversely proportional to the square root of the volume of air inside the chamber. After an object is placed inside the chamber, the change in resonant frequency is used to measure the volume of the object. The coefficient of variation of repeated measures of body volumes of 13 miniature piglets (5 to 18 days old, body weights 1253 to 2631 g) ranged from 0.3 to 3.2%. Body volumes measured by the acoustic method agree closely with those calculated from carcass analysis in which body volume is the sum of the volumes of total body water, fat, protein, and minerals. Fat-free mass computed from densitometry using a four-compartment model and body volume measurements from the acoustic method agrees with fat-free mass obtained from carcass analysis. The mean difference between methods was not significant: 1 ml for body volume and 3 g for fat-free mass. The limits of agreement between methods was +/- 75 ml for body volume and +/- 214 g for fat-free mass. Our results indicate that the acoustic method can measure a change in body volume of 75 ml and a change in fat-free mass of 214 g in a 2000 g infant.

Adipose Tissue↗
PubMed1988

Bone mineral content reflects total body calcium in neonatal miniature piglets.

We measured bone mineral content (BMC) in 18 neonatal miniature piglets by single photon absorptiometry, total body calcium (TBC) by total body neutron activation analysis, growth, and serum indices of mineral status (calcium, phosphorus, alkaline phosphatase activity). Measurements were begun on day 6, when the piglets were weaned, and were continued to day 19. After weaning, the piglets were assigned randomly to receive one of three diets which differed only in their concentrations of calcium and phosphorus: 100% of the recommended level (diet A), 60% (diet B), and 20% (diet C). No differences were observed among groups during the 19-day study, either in weight gain (48 +/- 2 g/day) or increment in crown-rump length (2.4 +/- 0.2 cm/wk). BMC correlated significantly (p less than 0.001) with TBC at 6 (r = 0.83), 13 (r = 0.77), and 19 (r = 0.93) days. BMC correlated significantly (p less than 0.001) with the ash weight (r = 0.87) and calcium content (r = 0.90) of the corresponding tibial bone segment. Anthropometric parameters and serum indices of mineral status did not predict TBC as accurately as did BMC measurements. We observed a range in BMC measurements in this study that was similar to the range reported for infants in the 1st yr of life. The high correlation between BMC and TBC suggested that BMC is useful in the assessment of mineral status in infants.

Animals↗
PubMed1988

Long-term airway sequelae in a pediatric burn population.

All admissions to the Shriner's Burn Institute in Galveston over a 5-year period were reviewed. One hundred of 1,092 patients admitted (9.2%) required airway support (endotracheal intubation or tracheostomy) for more than 24 hours. All clinical variables relating to general presentation and airway care were tabulated. Children who required open airway operations for resolution of acquired airway defects were analyzed separately. No predictive factors could be identified. Guidelines for optimal airway management in the burned child are reviewed.

Bronchoscopy↗
PubMed1988

Milk production by mothers of premature infants.

Milk volume, day of initiation of pumping, duration and frequency of milk expression, and length of night rest interval were evaluated for the first month postpartum in 32 healthy, nonsmoking women (ages 20 to 38 years) who delivered at 28 to 30 weeks' gestation. Early milk volumes were related negatively to the delay between delivery and the initiation of milk expression (r = -.48, P less than .02). Average milk volumes at 2 weeks and 4 weeks postpartum were 493 +/- 330 and 606 +/- 369 mL/d (mean +/- SD), respectively, and were not related to the absolute frequency or duration of pumping or to night rest interval. Volume changes between weeks 2 and 4 postpartum were correlated with the absolute frequency (r = .49, P less than .01) and duration of pump use (r = .42, P less than .05) during this interval and with changes in frequency (r = 0.56, P less than .002) or duration (r = 0.49, P less than .05) between the first 2 and the second 2 weeks postpartum. Optimal milk production was associated with five or more milk expressions per day and pumping durations that exceeded 100 min/d.

Adult↗
PubMed1988

Variability of macronutrient concentrations in human milk.

Variability observed in the energy, total nitrogen, lactose and fat concentrations of human milk was partitioned among subjects, days and sample duplicates. Highly significant differences were detected between individuals and between days within the individual for all four nutrients (P less than 0.001). Subjects, days and sample duplicate determinations contributed 89, 9 and 2 per cent, respectively, to the variance for energy; 87, 12 and 1 per cent for nitrogen; 75, 21 and 4 per cent for lactose; and 92, 8 and less than 1 per cent for fat. The reliability of mean estimates for a group or for an individual was derived for various combinations of subjects, days and duplicates to provide a tool for planning future studies.

Adult↗
PubMed1987

Macro- and trace-mineral intakes of exclusively breast-fed infants.

Intakes of calcium, phosphorus, magnesium, zinc, sodium, potassium, iron, and copper of 45 exclusively breast-fed infants were determined during the first 4 mo of life. Direct 24-h measurements of milk intake and mineral contents of human milk were used to estimate mineral intakes. Daily intakes of Ca, P, Zn, K, Na, Fe, and Cu decreased significantly over the study period while the intake of Mg increased. With the exception of Mg, mineral intakes on a weight basis displayed significant quadratic trends over the 4 mo. In spite of seemingly low-mineral intakes, growth progressed satisfactorily.

Body Height↗
PubMed1987

Plasma amino acid differences in very low birth weight infants fed either human milk or whey-dominant cow milk formula.

Midmorning plasma amino acid levels were measured in 31 healthy, very low birth weight infants (mean age 16 days, mean birth weight 1180 g, gestation 29 wk) during 96-h balance studies. All infants received continuous enteral infusion of isonitrogenous, isocaloric preparations of either human milk fortified with pasteurized, lyophilized fractions of mature human milk (n = 18) or whey-dominant cow milk-based formula (n = 13). Weight gain (15 g/kg/day), nitrogen retention (303 mg/kg/day), and metabolizable energy (104 kcal/kg/day) were similar between groups. Plasma levels of threonine, valine, and the sum of essential amino acids were significantly greater in the whey-dominant formula-fed infants (p less than 0.01). Taurine and cystine were measured in significantly greater concentrations in the fortified human milk and threonine, valine, methionine, and lysine in the whey-dominant cow milk formula (p less than 0.01). Relationships between plasma amino acid levels and indices of nitrogen utilization differed between groups. These differences suggest that further modifications of whey-dominant formulas may be indicated.

Amino Acids↗
PubMed1987

Future research in human milk.

Because of the importance of breast-feeding to child health, research in the formation, composition, and biological effects of human milk should be strongly encouraged. Future exploration should include the processes that are responsible for the synthesis and secretion of human milk; the nature and function of the physical compartments in human milk; the structure and function of certain proteins and other components in human milk; and the in vivo fate and effect of a host of constituents including nutrients, growth factors, hormones, inducers, immunological factors, and antiinflammatory agents. Because of the potential public health benefits, these studies should be a high priority in pediatric research for the next decade.

Breast Feeding↗
PubMed1987

Special properties of human milk.

Human milk is a highly complex fluid with a nutrient balance and an array of functional properties that may promote a level of metabolic efficiency that is not attainable when a cow milk-based formula is fed. This is not a novel idea. Mitchell in 1933 proposed that the level of efficiency of energy use is determined by the nutrient "balance" in the diet. Nonetheless, difficulties remain in the attempt to reconcile the low levels of intake with established estimates of energy needs. If the amount of energy that appears necessary for growth and maintenance of a 4-month-old infant is compared with that from his or her intake of an exclusive human milk diet, the infant should have little or no energy left for activity. Do metabolic economies contribute to more efficient uses of energy for growth and maintenance in breastfed infants? Are there differences in body composition? Does more efficient use of energy occur as a result of a decrease in clinical and subclinical infections? Is efficient energy utilization accomplished by significant curtailment in activity? If an excess level of energy is consumed by bottlefed infants, what are the positive or negative short-term or long-term consequences? These questions are the focus of research in numerous laboratories. Field and clinical studies of breastfed infants and in vitro studies of human milk offer unique opportunities to understand basic mechanisms of human adaptations to nutrient intake and environmental challenges.

Adult↗
PubMed1987

Human lactation: maternal transfer of dietary triglycerides labeled with stable isotopes.

A stable isotope tracer method was utilized to measure quantitatively the secretion of diet-derived fatty acids (FA) into human milk. A mixture of [2H6]tripalmitin, [2H18]-triolein, and [2H12]trilinolein was administered to three healthy, lactating women 22 to 30 years of age. Milk and blood samples were collected sequentially for 72 hr. The FA composition and concentration of total plasma, lipoprotein, and milk triglycerides were determined by gas-liquid chromatography (GLC) and the isotopic enrichment was determined by gas-liquid chromatography-mass spectrometry (GLC-MS). There were no statistically significant differences in mammary secretion of the individual fats, either by a single individual or between subjects. The mean secretion of fat by one breast was 5.11 +/- 1.26% of the dose (CV = 25%). There was a significant 6.0-hr delay between peak occurrence of the tracer in plasma and its occurrence in milk. The lipids are transported to the mammary gland primarily by the chylomicron and very low density lipoprotein triglycerides.

Adult↗
PubMed1986

The effects of different total parenteral nutrition fuel mixes on skeletal muscle composition of infant miniature pigs.

Two groups of 10-day-old miniature pigs were maintained on isocaloric and isonitrogenous total parenteral nutrition (TPN) regimens for nine days. One group received nonprotein energy as glucose, whereas the second group received a mixture of fat and glucose. The administration of the amino acid/glucose fuel mix resulted in higher plasma insulin but lower glucagon concentrations compared to the amino acid/glucose/fat mix. Differences also were observed in the composition of skeletal muscle, which contained higher concentrations of alkali-soluble (AS) proteins (chiefly cellular protein) and DNA, when glucose was the only source of nonprotein energy. Intracellular sodium and water content and nonalkali-soluble proteins (largely extracellular proteins) were lower in the skeletal muscle of the amino acid/glucose group than in that of the group receiving the fat regimen. No differences in RNA concentration, RNA/AS protein, or AS protein/DNA ratios were observed. These data suggest that conditions of high insulin production in the postnatal growth period favored increased DNA replication and accretion of AS protein. The differences in water and electrolyte composition indicate that the rate of chemical maturation of skeletal muscle was slower in the piglets receiving amino acids/glucose/fat than in those on the glucose regimen. This study has demonstrated that the source of nonprotein energy can influence skeletal muscle maturation in the postnatal period.

Animals↗
PubMed1986

Sources of variance in milk and caloric intakes in breast-fed infants: implications for lactation study design and interpretation.

Between-individual variation (BIV) and day-to-day variation (DDV) of total caloric and human milk intakes were examined in 17 infants. Nine were studied at months 5 and 6; 8 at months 6 and 7. All 17 were exclusively breast-fed for 5 full mo after which solid foods were added to the diet. Each infant was studied for five consecutive 24-h periods during which serial measurements were made of milk intake (test weighing) and solid food intake (pre- and postfeeding jar weighing). Total daily caloric intakes (kcal/day) were (mean +/- SD) 492 +/- 57, 547 +/- 70, and 567 +/- 98 at months 5, 6, and 7, respectively. Estimates of caloric intakes (kcal/kg/day) adjusted for body weight were 65.9 +/- 6.7, 72.6 +/- 11.2, and 70.9 +/- 13.0 at months 5, 6, and 7, respectively. Milk intakes (g/day) were 735 +/- 85, 640 +/- 106, and 562 +/- 214 at months 5, 6, and 7, respectively. BIV of milk intake increased after the introduction of solid foods. DDV (expressed as coefficient of variation) of caloric intake was nearly constant at each monthly observation and BIV increased from 8.8 at month 5 to 14.6 at month 7. The numbers of 24-h periods and subjects required for estimates of known precision of caloric and milk intakes of older breast-fed infants can be determined from these estimates of variance.

Adult↗
PubMed1986

Enhanced fecal excretion of selected immune factors in very low birth weight infants fed fortified human milk.

The amounts of lactoferrin, lysozyme, total IgA, secretory IgA (SIgA), and specific SIgA antibodies to a pool of Escherichia coli O antigens were measured in 96-h collections of feces obtained from 28 very low birth weight infants, 28-30 wk of gestation, studied at 2.5 and 6 wk of age. Eighteen of these infants were fed their mothers' milk fortified with fractions of skim and cream derived from pasteurized, lyophilized, mature human milk (FM) and 10 infants were fed commercial cow's milk-based formula. The concentrations of these selected immune factors in the FM and formula also were measured. Specific SIgA antibodies to E. coli O antigens were detected in the feces of 90% of the FM-fed infants, but in none of the feces of the formula-fed infants. The feces obtained from FM-fed infants had markedly greater quantities of lactoferrin (p less than 0.001), lysozyme (p = 0.006), and IgA (p less than 0.001) than those of cow's milk formula-fed infants. The concentrations of total and secretory IgA were correlated significantly (r = 0.88, p less than 0.001) and 95% of total IgA was SIgA. The fecal concentration of specific SIgA antibodies to E. coli O antigens in FM-fed infants correlated with the concentration of these antibodies in their milk (p less than 0.001). However, there were no direct relationships between the milk concentrations or the infant's intakes of the other selected immune factors and the excretion of these factors in the feces.(ABSTRACT TRUNCATED AT 250 WORDS)

Feces↗
PubMed1985

Feeding patterns of exclusively breast-fed infants during the first four months of life.

Milk intake and feeding patterns of 45 exclusively breast-fed infants were documented longitudinally over the first four months of life. Two prevailing feeding patterns were identified: one in which feedings were distributed throughout the 24-h day and one in which feedings were excluded from the early 12:00 a.m. to 6:00 a.m. period. No significant differences in total milk intake (g/24 h) were detected the day irrespective of feeding pattern. Feeding frequency and duration declined in successive months of lactation. Total milk intake was not significantly correlated to feeding frequency or duration.

Adolescent↗
PubMed1985

Fortified mothers' milk for very low birth weight infants: results of macromineral balance studies.

The mineral adequacy of fortified mothers' milk for very low birth weight (VLBW) infants was tested during their first two postnatal months. Metabolic balance and serum Ca, P, Mg, Na, and K values were evaluated at 2.5 and 6 weeks of life in 32 VLBW infants (less than 1.3 kg). Infants were fed either their mothers' milk fortified with skim and cream components derived from heat-treated, lyophilized mature human milk (FMM) or commercial cow milk-derived formulas. Despite Ca and P concentrations 50% to 100% higher in the fortified human milk than is usual in unfortified human milk, group FMM's Ca and P intakes remained significantly below those fed formula (P less than 0.001). Serum calcium levels and alkaline phosphatase activity were higher and serum phosphorus lower (P less than 0.002) in group FMM, whereas serum levels of magnesium, sodium, and potassium were similar in both groups. Ninety-six-hour urinary excretion of Ca was greater and 96-hour urinary excretion of P was less in group FMM (P less than 0.02). Retention of Ca and P in both groups was significantly below estimates of intrauterine accretion. Mg retention was significantly higher in group FMM (P less than 0.002) despite intakes of Mg significantly below those in infants fed formula. Although intakes of Na were below recommended levels in both groups, by the second balance period all infants demonstrated Na retention that was greater than expected from the sum of estimates of intrauterine accretion and dermal losses. Similar findings were noted for K. Biochemical and balance data indicate that relative to the needs of the VLBW infant, fortified mothers' milk was deficient in Ca and P, but adequate in Mg, Na, and K.

Animals↗
PubMed1985

Fortified mothers' milk for very low birth weight infants: results of growth and nutrient balance studies.

Mothers' milk, fortified daily with skim and cream components derived from mature donor human milk, was fed fresh during the first 2 postnatal months to 18 (group FMM) healthy, very low birth weight (VLBW) infants. Following the same feeding protocol, 16 additional VLBW infants were fed commercial formula that had a similar range of energy and nitrogen. Infants were evaluated for growth, metabolizable energy, balances of nitrogen and fat, and biochemical markers of nutritional status. Growth measurements from birth to 1800 gm were similar in the two groups. Nutritional balance was performed at approximately 2.5 (first study period) and 6 (second study period) weeks. Metabolizable energy (average 109 kcal/kg/day) was similar in both groups and met theoretical needs of the growing VLBW infant. Apparent nitrogen retention was similar and equivalent to estimates of intrauterine nitrogen accretion (approximately 325 mg/kg/day). Fat absorption increased from the first (70% of intake) to the second study (80% of intake) and was similar in both groups. Serum values for albumin, total protein, prealbumin, hemoglobin, and creatinine were also similar, and declined with increases in postnatal age. Significant differences were observed between feeding groups for serum phosphorus and calcium. These results indicate that healthy VLBW infants maintain adequate growth and macronutrient balance for the first 2 months postnatally when fed mothers' milk fortified with additional skim and cream components.

Anthropometry↗
PubMed1985

Prediction of body density from skinfold measurements in lactating women.

Regression equations predicting body density from skinfold measurements were derived for a group of lactating women. It was concluded that specific equations for lactation were not necessary, since the resultant equations were not significantly different from those published for non-lactating women. The ability to predict an individual's body density from skinfold thickness measurements was unsatisfactory for either clinical or research applications.

Adipose Tissue↗