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Biomedical subjects

A Lucas

Publications and source records attributed to A Lucas.

At least 289 records · Page 16Linked to original sources
PubMed1987

An automated enzymic micromethod for the measurement of fat in human milk.

Most (98%) of the fat in human milk is present as triglycerides. This paper describes the use of a clarification procedure that enables the level of human milk fat to be determined by measurement of glycerol released by enzymic hydrolysis of triglycerides. The method requires only 10-50 microliters milk, thus presenting a possible technique for work with small mammals, and is suitable for use with autoanalysers, permitting rapid sample throughput.

Autoanalysis↗
PubMed1987

The nutritional role of breast-milk IgA and lactoferrin.

The nutritional enigma concerning the extent to which breast-milk immune proteins are digested has been investigated by measuring the intakes and faecal outputs of IgA and lactoferrin over 7 days in 10 exclusively breast-fed (BF) and 9 formula-fed (FF) fullterm infants at 6 and 12 weeks post-partum. BF outputs (mg/day) greatly exceeded FF values (p less than 0.001): at 6 weeks secretory-IgA BF = 160 +/- 28, FF = 14 +/- 2, lactoferrin BF = 14 +/- 2, FF = 0.9 +/- 0.1; at 12 weeks secretory-IgA BF = 94 +/- 17, FF = 25 +/- 5, lactoferrin BF = 7 +/- 1, FF = 1 +/- 0.3. Secretory-IgA represented 42% and 27% of BF faecal protein at 6 and 12 weeks compared with 6% for FF infants at both ages. BF secretory-IgA outputs were highly correlated with intakes (r = 0.83, p less than 0.001). IgA and lactoferrin outputs and the presence of faecal secretory-IgA fragments in BF and FF infants were influenced by defaecation rate, suggesting that partial degradation occurred in the large intestine. By 6 weeks post-partum only 1% lactoferrin and 17% secretory-IgA intakes appeared in the faeces and 95% breast-milk protein could be regarded as nutritionally available. The elevated BF outputs of IgA and lactoferrin relative to endogenous excretion suggest, however, that breast-milk may still make a considerable contribution to intestinal defence mechanisms after the neonatal period despite the small proportion of daily intake which escapes digestion. The protective action of IgA and lactoferrin may also depend on their site of degradation and the nature of fragments.

Feces↗
PubMed1987

Measurement of milk intake by deuterium dilution.

In 14 studies, each lasting seven days, on eight bottle fed infants milk intake was measured by deuterium dilution and by weighing the formula consumed and oral losses. Mean (SD) milk intake was 829 (108) g/day when measured by isotope dilution and 837 (98) g/day when measured by direct weighing, giving a mean difference between methods of 1.0 (5.0)%. Thus the stable isotope procedure is a potentially useful method for investigating lactation and nutritional problems.

Animals↗
PubMed1987

Measurement of carbon dioxide production rate in sick ventilated premature infants.

A new method is described for measuring the rate of carbon dioxide production, and hence for estimating energy expenditure, in preterm infants receiving assisted ventilation. In a validation study, the mean error in carbon dioxide measurement was 1.9%. Measurements were made, over a 45-min period, on 11 sick, ventilated subjects and carbon dioxide production rate was 5.2 +/- 0.7 (SD) ml/min X kg body weight. We suggest that continuous monitoring of carbon dioxide output will contribute to the clinical assessment of the effects of different ventilator settings on pulmonary gas exchange and that estimated values for energy expenditure will be of value in nutritional studies on sick ventilated infants.

Carbon Dioxide↗
PubMed1987

Long-term variation in oxygen consumption rate in preterm infants.

An investigation was made of long-term variation in oxygen consumption rate (VO2) in preterm infants. Four subjects (gestational age 27-34 weeks, postnatal age 17-38 days, weight at study 1.1-2.6 kg) were studied for 5 days each using open-circuit, indirect calorimetry. The mean VO2 for each subject (11.0-11.5 litres/kg/day) was within the reported range. However, the between-subject coefficient of variation during the study (2.1%) was smaller than the mean between-measurement coefficient of variation for daily VO2 (3.8%, range 1.7-6.3%). In addition, the between-measurement coefficient of variation was increased further for measurement intervals of less than 24 h (reaching a mean of 8.3% for 1-hour periods), and a relationship between measurement duration and the precision of estimating VO2 over 3 or 5 days is described. Thus, even 24-hour measurements of VO2 in these preterm infants were less representative of the individual's VO2 over 3 days than the group mean estimate. This finding is of relevance to future studies in this area, particularly those in which short-term measurements of energy expenditure are combined with a nutrient balance study to determine the composition of weight gain, because even small errors in the estimate of total energy expenditure can lead to unacceptably large errors in calculated energy deposition.

Calorimetry, Indirect↗
PubMed1987

Occurrence and significance of riboflavin deficiency in preterm infants.

Few studies have explored the importance of riboflavin deficiency in premature infants. Infants receiving human milk during the first 2 weeks become biochemically riboflavin-deficient, partly through photodegradation of riboflavin during the banking and delivery of human milk. Animal studies have shown that the metabolic lesions of riboflavin deficiency in sucking neonates differ in important ways from those seen later after weaning. Techniques are described for non-invasive study of functional riboflavin requirements by premature infants. It appears prudent to supplement human milk-fed babies with at least 300 micrograms riboflavin/day; but the potential danger of over supplementation in infants exposed to phototherapy is discussed.

Disease Models, Animal↗
PubMed1987

Does diet in preterm infants influence clinical outcome?

After several decades of intensive research into feeding preterm infants, it is important to question why there is persisting uncertainty over their dietary management. The evolution of scientific investigation in this field is compared with that in other areas of clinical science, where a three-phase pattern emerges: phase 1, reports of anecdotal observation and clinical experience; phase 2, epidemiological observation and physiological experiment; and phase 3, controlled prospective trials of specific interventions on clinical outcome. It is argued that research into feeding preterm infants has not evolved beyond physiological experiment (phase 2) and that the absence of clinical outcome data (phase 3 research) explains major uncertainties in clinical practice. Data from a large randomized multicentre outcome study of preterm nutrition are used to demonstrate how the wealth of previous and current 'physiological' information cannot be used satisfactorily to predict desirable clinical outcome responses to early diet.

Clinical Trials as Topic↗
PubMed1987

Does it matter how we feed premature babies?

The multiplicity of dietary regimes available for low birthweight infants is a measure of clinical uncertainty in this field. The reasons for this persisting uncertainty are analysed: few studies have examined whether early diet matters in terms of clinical outcome; instead, management decisions have been based on short-term 'physiological' studies on nutrient accretion, growth and metabolism. Data from this Unit's multicentre outcome trials on nearly 1000 preterm infants, randomly assigned to early diet, are used to demonstrate that whilst diet influences many aspects of the infants 'physiology' in the short term, such physiological responses have limited value in predicting clinical outcome. Preliminary data from the early follow-up of this cohort to 18 months post-term suggest that the diet used in the neonatal period may have persisting consequences in terms of motor and mental development and growth. The longer-term significance of these findings is being investigated.

Clinical Trials as Topic↗
PubMed1987

Upper intestinal mucosal proliferation in the newborn guinea pig: effect of composition of milk feeds.

To examine the effects of first enteral feeds on the development of the gastrointestinal tract, the changes in upper intestinal mucosal morphology and kinetics were studied during the 1st wk of postnatal life in neonatal guinea pigs. Animals were reared either on mother's milk or on a cow's milk formula isocaloric with guinea pig milk. Mucosal crypt-villus architecture was measured by microdissection, and mucosal kinetics were measured using a metaphase arrest technique. Comparable growth was achieved between the two feeding groups. There were no significant differences in the villus heights, crypt depths, or crypt:villus ratios between the naturally fed and formula-fed guinea pigs. The formula fed had a crypt cell production rate twice as high as the naturally fed animals throughout the study period (p less than 0.001). The higher mucosal proliferation rate of the formula-fed animals may be due to the absence of growth-modulating factors in this milk, or a regenerative response to "damage" of the upper intestinal mucosa by cow's milk proteins.

Animal Feed↗
PubMed1987

Energetic efficiency and nutrient accretion in preterm infants fed extremes of dietary intake.

The role of diet-induced thermogenesis (DIT) in the regulation of energy utilization in preterm infants was investigated by measuring energy expenditure and nutrient deposition in groups of subjects fed either banked drip breast milk (BBM) or a preterm formula (PF). Nutrient deposition was determined by combining a 3-d nutrient balance study and measurement of energy expenditure. Infants fed PF consumed 57 per cent more metabolizable energy (ME) than those fed BBM. There were significant differences between groups in energy expenditure, energy deposition and protein deposition; 76 per cent of the additional ME intake consumed by the PF-fed group was deposited while the remaining 24 per cent was expended. Infants fed PF gained weight 39 per cent faster than those fed BBM (19, compared to 14 g/kg/d), and deposited 128 per cent more fat and 86 per cent more protein. These findings indicate that nutrient deposition, rather than DIT, was the primary use of the extra ME received by the infants fed PF. However, the effect of the high energy intake on weight gain in these subjects was reduced, compared to its effect on nutrient deposition, by increases in the concentrations of fat and protein in new tissue.

Body Weight↗
PubMed1986

Hybridoma growth and antibody secretion in serum-supplemented and low protein serum-free media.

Hybridoma cell growth and monoclonal antibody secretion were studied with three murine hybridomas, SS1.1, NS6.3 and 455, propagated in four low protein serum-free media and various serum-supplemented media. Cell metabolism, as indicated by cell growth and glucose uptake, and antibody production rates were measured. The analysis focused on the secretion of monoclonal antibodies as a function of the medium makeup. Although cell densities achieved were generally higher for serum-supplemented media, glucose uptake rates did not vary significantly, and antibody secretion rates measured at peak cell density were higher for serum-free media with all three hybridomas. Decreasing the serum concentration had opposite effects for the IgM and IgG secretors, NS6.3 and SS1.1; secretion rates measured at peak cell density were higher for the former and lower for the latter.

Animals↗
PubMed1986

Birthweight centiles in preterm infants reappraised.

The relationship between birthweight, gestation and obstetric and neonatal course was examined for 444 live births at 25-31 weeks gestation in 5 centres from 1982 to 1984 and comparative data were obtained from 121 infants below 32 weeks born in 1968-1972. The rate of 'interventive' deliveries by elective caesarean section, at this gestation, performed largely for conditions associated with poor intrauterine growth, has risen over 10-fold in the past decade, now accounting for 42% of deliveries at 30 weeks. This may explain in part a secular trend towards reduced birthweight for gestation in preterm infants. Electively delivered infants were significantly lighter than those delivered spontaneously and were responsible for substantial skewing and lowering of overall birthweight centiles. In contrast, the infant's sex, whether or not the infant survived following live birth, and whether gestational age was assessed by maternal dates or by clinical estimation (including ultrasound), all made no significant difference to birthweight centiles. A new birthweight centile chart is presented for infants less than 32 weeks, based only on spontaneous deliveries. This chart differs considerably from those commonly used in Britain and, we suggest, provides a realistic standard for identifying abnormal intrauterine growth.

Birth Weight↗
PubMed1986

Comparison of the doubly labeled water (2H2(18)O) method with indirect calorimetry and a nutrient-balance study for simultaneous determination of energy expenditure, water intake, and metabolizable energy intake in preterm infants.

The doubly labeled water method was compared with indirect calorimetry and a nutrient-balance study for simultaneous determination of rates of CO2 production, energy expenditure, and water intake over 5 days in four preterm infants. Additionally, metabolizable energy (ME) intake estimated using the isotope procedure (as energy expenditure plus an estimate for energy deposition based on weight gain), was compared to ME intake measured in the balance study. Compared to values obtained by traditional methods, calculated CO2 production, energy expenditure, and water intake differed by -1.4 +/- 4.8% (SD), +0.3 +/- 2.6%, and +5.7 +/- 1.4%, respectively; the difference in water intake was significant (p less than 0.05). Calculated ME intakes were 5.3 +/- 19.3% less than measured intakes, but the difference was not significant. These findings indicate that the doubly labeled water method can provide accurate information on rates of CO2 production, energy expenditure, and water intake in preterm infants, but individual estimates of ME intake may be subject to substantial error.

Calorimetry, Indirect↗
PubMed1986

Gut hormones and 'minimal enteral feeding'.

Previously we have identified multiple surges in plasma concentrations of gut hormones postnatally in enterally fed term and preterm infants. In this study on 104 preterm infants we have shown that such surges are induced after ingestion of very small quantities of human milk. Whereas 6-day-old exclusively parenterally fed infants showed no postnatal elevation in enteroglucagon, gastrin, GIP, motilin and neurotensin, infants recovering from hyaline membrane disease who had received restricted enteral nutrition had similar hormone surges to those seen in well infants on full enteral feeds. Significant elevations in enteroglucagon, gastrin and GIP occurred after a cumulative mean enteral feed volume since birth of only 24 ml (12 ml/kg body weight) had been consumed and after a mean total intake of 96 ml (50 ml/kg) the response was maximal. Greater feed volumes were required to produce a neurotensin or motilin surge, but even these volumes were substantially lower than those required for full enteral feeding. In view of the proposed roles of gut hormones in the adaptation to extrauterine nutrition these data have implications for mammalian biology and raise the possibility that 'minimal enteral feeding' might have a clinical therapeutic role in infants undergoing prolonged parenteral nutrition.

Enteral Nutrition↗
PubMed1986

Breast milk jaundice in premature infants.

In randomised study of 186 preterm infants those fed on maternal or banked breast milk had a significantly higher peak bilirubin concentration and a more prolonged jaundice than infants fed an artificial preterm formula and were over four times more likely to achieve plasma bilirubin values above 200 mumol/l (11.7 mg/100 ml). This dietary effect was seen even in a high risk subgroup of sick ventilated infants below 1500 g who were receiving restricted enteral intakes. We suggest that breast milk jaundice in preterm infants may increase clinical intervention. Our findings are discussed in the light of epidemiological data suggesting an association between moderate hyperbilirubinaemia (greater than 170 mumol/l) and neurodevelopmental outcome.

Bilirubin↗