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Biomedical subjects

A D Phillips

Publications and source records attributed to A D Phillips.

108 records · Page 6Linked to original sources
PubMed1982

Passive diffusion in small intestinal mucosa in childhood.

The passive permeability of the small intestinal mucosa in childhood was investigated by studying the penetration of two light- and electron-dense tracer molecules (ruthenium red mol. wt = 1000 and horseradish peroxidase mol. wt = 40 000) into fixed biopsy specimens. Ruthenium red confirmed the presence of damaged and extruding epithelial cells in normal mucosa and showed a significant increase in such cells in abnormal mucosa. Horseradish peroxidase demonstrated that antigenically-sized molecules could enter a proportion of these cells and significantly more cells were penetrated in abnormal mucosa, reflecting the ruthenium red results. Thus, anatomical pathways for passive diffusion of antigen through damaged or extruding cells exist in normal and, to a greater extent, in abnormal small intestinal mucosae in childhood. Further study using living tissue may reveal the importance of this phenomenon in relation to the active uptake of antigen.

Antigens↗
PubMed1981

Small intestinal mucosa in childhood in health and disease.

A great increase in the knowledge of human small intestinal mucosal pathology has resulted from the use of the peroral small intestinal biopsy technique. This paper highlights some different applications of electron microscopy to such biopsy samples in order to obtain diagnostic criteria and to further the understanding of enteric processes in childhood in health and disease. The importance of control data in childhood is emphasized and differences are described between adult and childhood mucosa. The possibilities of quantitative studies at the ultrastructural level and the link between structure and function are demonstrated by studies on microvillous appearance in relation to disaccharidase enzyme levels; the potential for experimental work is shown in studies using tracer molecules to investigate antigen permeability of the small intestine; and finally descriptive observations is highlighted in a section concerned with parasitic, bacterial and viral infections of the small intestine in childhood.

Bacterial Infections↗
PubMed1980

Microvillous surface area in secondary disaccharidase deficiency.

Electron microscopy was used to measure microvillous surface area in seven small intestinal biopsies showing secondary disaccharidase deficiency and in five biopsies having normal disaccharidase levels. There were significant reductions in microvillous surface area in the enzyme deficient group, although the microvilli were not severely damaged. Histological abnormality was not always present with disaccharidase deficiency. There was no significant difference in intraepithelial lymphocyte counts between the two groups.

Adolescent↗
PubMed1979

The structure of the enterocyte in relation to its position on the villus in childhood: an electron microscopical study.

An electron study of histologically normal small intestinal mucosa taken from 10 children has shown, on morphological grounds, that the mid-region of the villus is best adapted for digestion and absorption. Microvilli in the mid-region were tallest, and presented the maximal surface area. In contrast the upper region of the villus exhibited a reduction in microvillous surface area and some cellular damage. Cellular extrusion was observed near the base of the villus as well as near the tip. The occurrence of cellular alterations in the oldest and more exposed regions of normal mucosa in childhood may be symptomatic of a natural epithelial ageing process but may also be the result of an adverse luminal effect on the enterocytes. These findings differ from some of the observations made on adult small intestinal mucosa where it has been reported that the microvilli present a maximal surface area and the enterocytes are most active at the tips of the villi rather than in the mid-region.

Child, Preschool↗
PubMed1979

Small intestinal intraepithelial lymphocyte levels in cow's milk protein intolerance.

The mean small intestinal intraepithelial lymphocyte count in seven children with untreated cow's milk protein intolerance (CMPI) on a milk-containing diet was significantly higher than 22 control children also having a milk-containing diet. Ten milk-intolerant children on a milk-free diet had a mean intraepithelial lymphocyte count which was significantly lower than the level in the 22 control children on a milk-containing diet. When these 10 children were challenged with cow's milk they relapsed clinically, and in every case the intraepithelial lymphocyte count rose, although it remained within normal limits. Nineteen children on milk-free diets who had recovered from CMPI had a mean lymphocyte count which was also significantly lower than controls on normal diets, suggesting that when milk is remo-ed from the diet the lymphocyte count is low regardless of whether the child is milk sensitive or not. The reaction of intraepithelial lymphocytes to milk in CMPI is markedly different from their response to gluten in coeliac disease.

Animals↗
PubMedDate not supplied

Royal Society of Tropical Medicine and Hygiene meeting at Manson House, London, 14 December 1995. Enteropathogenic Escherichia coli--mucosal infection models.

The formation of attaching and effacing (A/E) lesions is central to the pathogenesis of enteropathogenic Escherichia coli (EPEC)-mediated disease in humans and Citrobacter rodentium-mediated transmissible colonic hyperplasia in mice. Closely related outer membrane proteins, known as intimins, are required for formation of the A/E lesion by both EPEC and C. rodentium. In this study we found similar ultrastructural damage in small intestinal biopsies from an EPEC-infected child and large bowel specimens from C. rodentium-infected mice. The C. rodentium-infected large bowel biopsies revealed massive hyperplastic reactions and the infected human small intestinal biopsies showed an increase in total crypt cell number and mitotic index. EPEC-infected small intestinal organ cultures revealed bacteria adhering in a localized pattern and evidence of A/E lesions. Covaspheres coated with a biologically active cell-binding domain of intimin also adhered to cells in a localized fashion but did not induce the characteristic A/E lesions.

Adhesins, Bacterial↗
PubMedDate not supplied

Clinical associations of Norwalk-like virus in the stools of children.

From among 1,360 stool specimens examined during the 19-month period from March 1982 to September 1983, small round-structured viruses, morphologically indistinguishable from the Norwalk agent, were detected by electron microscopy in 42 specimens from 28 children. Diarrhoea was mild, and vomiting, although frequently observed, was not an invariable feature. Mild pyrexia occurred in three patients. Many cases occurred some time after admission to the ward; this and other features suggested a hospital-acquired infection. These cases in particular tended to have other viral infectious agents detected at the same time. Persistent diarrhoea occurred in only three cases; one with preexisting gastrointestinal pathology, and two with a combined Norwalk-like agent, astrovirus, and rotavirus infection.

Acute Disease↗
PubMedDate not supplied

Polymorphonuclear neutrophil leucocytes in childhood Crohn's disease: a morphological study.

Light and electron microscopy was applied to surgical resections and endoscopic biopsies from the ileum and colon of 15 children with Crohn's disease in order to investigate the involvement of neutrophils in the disease process. Clear evidence was found of neutrophil infiltration of the lamina propria and epithelium, neutrophil migration into the gut lumen through epithelial breaks and intact epithelium, neutrophil phagocytosis of luminal and lamina propria bacteria, and the presence of intracellular neutrophils in enterocytes. Similar findings were seen in 5 of 6 children with ulcerative colitis and in a case of an E. coli colitis, but not in 8 controls. The observations demonstrate the involvement of neutrophils in Crohn's disease in childhood and suggest that the response is directed, in part, against luminal enterobacteria and enterocytes.

Abscess↗