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Biomedical subjects

L T Weaver

Publications and source records attributed to L T Weaver.

At least 109 records · Page 6Linked to original sources
PubMed1989

Changes in upper intestinal epithelial morphology and kinetics in the growing guinea pig.

Weaning, the process of intestinal adaptation from milk to solid diet, demands changes in gastrointestinal function. We aimed to measure upper intestinal mucosal morphology and cytokinetics during early life, to determine whether the marked changes seen at weaning in altricial species, such as rat and mouse also occur in the precocial guinea pig. A total of 79 animals was studied. Jejunal morphology was measured by microdissection and crypt cell production rate by a metaphase arrest technique in animals at 1, 7, 14, 21, and 28 days after birth. There was a 40% decline in villus height from 986 to 576 microns during the first 2 wk (p less than 0.001). Crypt depth increased by 25% from 148 to 199 microns (p less than 0.01). After an initial decline there was a significant increase in crypt:villus ratio from 6.7 to 8.2 (p less than 0.001), in crypt cell production rate from 3.9 to 5.6 cells/crypt/h (p less than 0.001), and net villus influx from 26.1 to 45.9 cells/villus/h (p less than 0.001) from 14 days onward. These proliferative changes were accounted for by an increase in the depth and number of crypts, and in crypt cell production rate, leading to an increase in net villus influx. In contrast with the rat and mouse they were gradual, occurred largely during the 3rd wk, and appeared to follow the cessation of breast feeding and commencement of solid food. It is suggested that the functional changes in the small intestine that occur during weaning in the guinea pig are neither due to rapid proliferation of a new epithelial cell population, nor precipitated by change in diet.

Animals↗
PubMed1988

The impact of milk and weaning diet on gastrointestinal permeability in English and Gambian infants.

To test the hypothesis that cow's milk formula and weaning diet may damage the gut mucosa, the gastrointestinal permeability of 77 healthy English and Gambian infants was measured from the urinary recovery of the markers lactulose and mannitol included in feeds. All infants were born at term and studied at 6, 12 and 18 weeks of age. No infant developed diarrhoea or failed to thrive. Infants fed on cow's milk formula had higher urinary lactulose: mannitol excretion ratios than breast-fed infants at 6 weeks of life (P less than 0.05). There was no significant difference in the urinary marker excretion ratios of English formula-fed and Gambian breast-fed infants at 12 weeks. An increase in urinary lactulose: mannitol excretion ratios was seen in all infants at 18 weeks. This was more probably due to increasing age than to the introduction of weaning diet. Cow's milk formula feeding was associated with greater intestinal permeability than breast feeding in infants aged 6 weeks. The introduction of weaning diet after 6 weeks did not appear to have an impact on the gastrointestinal permeability of healthy growing infants born in either England or rural Gambia.

Aging↗
PubMed1988

Does 'sugar' permeability reflect macromolecular absorption? A comparison of the gastro-intestinal uptake of lactulose and beta-lactoglobulin in the neonatal guinea pig.

Intestinal closure to cow's milk beta-lactoglobulin occurs within 6 days of birth in the guinea pig. Passive intestinal permeability to lactulose persists through the suckling period. The uptake of small water-soluble markers does not reflect macromolecular absorption, and has no place in the measurement of immunologic protein handling by the gut.

Animals↗
PubMed1988

The guinea pig as a model for the study of the effects of milk on growth and development.

Study of the effects of enteral nutrition on neonatal growth and development has been hindered by the lack of a suitable model. A model has been developed to measure the effects of an artificial milk formula on the growth of the newborn guinea pig. The composition of milk expressed from lactating guinea pigs 2 to 13 days postpartum was analysed for its protein, lactose, fat and metabolizable energy contents. Changes in osmolality, water and electrolyte contents were determined. An isotope (3H2O) dilution method was used to measure daily milk intakes of naturally suckled animals. An artificial formula, based on cow's milk (CMF), isocaloric with natural guinea pig milk was designed and synthesized. Neonatal guinea pigs were reared either naturally or on CMF from birth to 8 days. Comparable growth and milk intakes were achieved by the two feeding groups. No adverse effects of CMF were noted. The study represents the development of an effective means of raising a laboratory animal during the suckling period on an artificial milk formula. The model may be used to measure the impact of enteral nutrition on the ontogeny of the gut, and on neonatal growth and development, in a precocial species which more closely resembles man than the altricial species, such as rat and mouse, generally used for this purpose.

Animal Feed↗
PubMed1987

Tolerance to orally induced anaphylactic sensitisation to cow's milk proteins and patency of the intestinal mucosa in the neonatal guinea pig.

Guinea pigs fed cow's milk within 2 days of birth may acquire tolerance to anaphylactic sensitisation to cow's milk proteins. Appreciable amounts of beta-lactoglobulin may be detected in their blood, in contrast with animals receiving cow's milk later than this age. Uptake of beta-lactoglobulin from the gut to circulation ceases after the 6th postnatal day. These findings could be relevant to cot death in the human infant should the anaphylactic hypothesis be substantiated.

Anaphylaxis↗
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↗
PubMed1986

Neonatal intestinal lactase activity.

The sequential changes in intestinal lactase activity of 40 neonates were measured indirectly from the differential uptake and excretion of lactose and the non-metabolisable disaccharide lactulose contained in formula feeds. A daily decline in urinary lactose:lactulose excretion ratios, reflecting a rise in intestinal lactase activity, followed formula feeding. Percentage decline was related directly to gestation: full term infants displayed a fivefold greater decline in lactosuria than infants with a gestation of 28 weeks during the first 10 days of milk feeding. The difference between lactose:lactulose ingestion and excretion ratios suggests that within five days of starting feeds intestinal hydrolysis of lactose exceeds 98% efficiency, even in very preterm infants.

Aging↗
PubMed1985

Intestinal permeability changes and excretion of micro-organisms in stools of infants with diarrhoea and vomiting.

The relation between diarrhoea and vomiting, the excretion of stool micro-organisms, and the passive intestinal permeability in 20 infants living in a deprived urban area was studied prospectively from birth to age 6 months. Intestinal permeability was measured from the ratio of lactulose to mannitol recovered in the urine of infants receiving feeds containing both markers. Micro-organism excretion was found to occur in both the presence and absence of gastrointestinal symptoms, but a significantly higher mean intestinal permeability was recorded in those infants with symptoms and organisms in the stool than in those with neither. An increased intestinal permeability may be a sign of mucosal damage by intestinal micro-organisms.

Diarrhea, Infantile↗
PubMed1984

The association of extrahepatic bile duct atresia and neonatal Epstein-Barr virus infection.

An infant with uncorrectable extrahepatic bile duct atresia was found to have evidence of Epstein-Barr virus infection during the neonatal period. It is probable that the infection was acquired in utero. In view of the association of hepatitis with the Epstein-Barr virus in later life, it is possible that this infection was responsible for the development of bile duct obstruction.

Antibodies, Viral↗
PubMed1984

Intestinal permeability in the newborn.

Passive intestinal permeability in 33 newborn babies was studied using feeds containing lactulose and mannitol. Each marker is thought to pass across the gut wall by a different route; lactulose by a paracellular and mannitol by a transcellular pathway. Neither is metabolised and both are wholly and solely excreted by the kidney; urinary recovery is a measure of the intestinal uptake. Babies born before 34 weeks' gestation exhibited a higher intestinal permeability to lactulose than more mature babies, and all preterm babies showed an appreciable decline in lactulose absorption during the first week of oral feeds. Babies of 34 to 37 weeks' gestation achieved a 'mature' intestinal permeability to lactulose within four days of starting oral feeds. These findings may reflect the immaturity of the gut of the preterm baby rather than a process essential to adaptation to enteral nutrition.

Gestational Age↗