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Biomedical subjects

N Evans

Publications and source records attributed to N Evans.

At least 163 records · Page 9Linked to original sources
PubMed1979

Preliminary experience with controlled-release aminophylline in asthmatic children: salivary levels and peak flow following a single dose.

Preliminary experience of a controlled-release aminophylline tablet in twenty-five asthmatic children has been gained by measuring salivary theophylline levels and peak flow after a single dose (11 mg/kg). The results were compared with an oral theophylline preparation. Mean salivary levels remained elevated at eight hours following ingestion of controlled-release aminophylline, at which time 58% of the children continued to show an improvement in peak flow. Individual children showed a wide variation in salivary levels and respiratory response. It is recommended that theophylline levels should be monitored in the saliva to ensure maximum benefit from the drug.

Adolescent↗
PubMed1978

Adherence of an enteropathogenic strain of Escherichia coli to human intestinal mucosa is mediated by a colicinogenic conjugative plasmid.

The capacity of a human enteropathogenic Escherichia coli (EPEC) strain serotype O26:K60:H11, to adhere to the mucosa of the human fetal small intestine was shown to be plasmid mediated. Adherence was transferred at a high frequency in a long-term conjugal mating experiment to E. coli K-12 and was lost by treatment of the EPEC strain with the curing agent ethidium bromide. Analysis of radioactively labeled DNA from lysates of the EPEC, transconjugant, and cured strains indicated that adherence was correlated with the presence of plasmid DNA species with an approximate average molecular weight of 56 X 10(6). Resistance to the antibiotics spectinomycin, streptomycin, sulfonamides, and tetracycline and production of colicin Ib were all transferred in long-term mating and lost upon curing coordinately with the property of adherence. In conjugal mating experiments of limited duration between E. coli K-12 strains, however, segregation of colicin production and mucosal adherence from multiple drug resistance was observed. Analysis of plasmid DNA of segregant transconjugant strains confirmed the presence in the 56 X 10(6)-dalton plasmid species of two previously unresolved components, pLG101 designating the ColIb plasmid which also carries the determinant for mucosal adherence and pLG102 representing the slightly smaller multiple drug resistance plasmid.

Antigens, Bacterial↗
PubMed1977

Hypoglycemia of infancy and nesidioblastosis. Studies with somatostatin.

We treated a two-month-old infant with servere intractable hypoglycemia and nesidioblastosis with continuous glucose infusions (0.75 g per kilogram per hour) via a central venous catheter. Preprandial glucose levels on this regimen were 37+/-2 mg per deciliter (+/-S.E.M.). Basal serum insulin levels were within normal fasting levels for this age group but inappropriately elevated for the blood glucose levels. The beta cells were exquisitely sensitive to infusions of synthetic cyclic somatostatin, with a dose-dependent rise in blood glucose and concomitant suppression of serum insulin levels. There was only minimal suppression of plasma glucagon levels. Single subcutaneous injections of 50 microng of protamine zinc somatostatin raised preprandial blood glucose levels to 83+/-3 mg per deciliter for four to five days although preprandial hormone levels were unchanged. These findings indicate that hypoglycemia of infancy is a hyperinsulin state with abnormal basal regulation of insulin secretion.

Adenoma, Islet Cell↗
PubMed1977

Hormonal manipulation of carrageenin-induced pyresis in rats,.

The intensity of the hyperthermic response in rats promoted by subplantar injections of 1 mg of carrageenin is directly related to the irritant properties of the type of carrageenin. The overall pyretic response is more dramatic in female rats than in male rats. Subtle changes in the time-course hyperthermic profiles are seen after hormonal modifications.

Animals↗
PubMed1977

Intestinal damage in rotavirus and adenovirus gastroenteritis assessed by d-xylose malabsorption.

The absorption of D-xylose infused into the duodenum was assessed in infants with acute gastroenteritis. 1-hour blood-xylose levels were low in 6 patients found to harbour rotavirus in the small intestinal aspirate. Normal levels (greater than 1-26 mmol/l) were obtained in the absence of virus particles in the small intestine in a further 6 patients: in 3 of these adenovirus or rotavirus was recovered from the stools. Three patients with adenovirus in the small intestinal juice and ill with acute gastroenteritis also had low xylose levels. This finding supports earlier epidemiological studies that adenovirus may be a causative agent of acute infantile gastroenteritis. The association between virus in the small intestine and xylose malabsorption may indicate mucosal damage. Formal proff of this is awaited.

Adenoviridae Infections↗
PubMed1976

High-performance liquid chromatographic analysis of porphyrins in clinical materials.

Methods for the isolation of porphyrins as their methyl esters from porphyric urine and faeces as well as other biological materials are described. Quantitative analyses can be carried out by high-performance liquid chromatography (HPLC), using appropriate internal standards; hence excretion patterns in the various types of porphyria can be obtained which may facilitate clinical diagnosis more effectively than the earlier qualitative thin-layer chromatographic methods. Use of the newer microparticulate column packing materials has improved the efficiency of the HPLC analyses, and enables the more convenient isochratic elution techniques to be used (rather than gradient elution). Separations of some porphyrin isomers on these columns are also described.

Chromatography, High Pressure Liquid↗
PubMed1976

Macrocyclic intermediates in the biosynthesis of porphyrins.

The hepta-, hexa- and penta-carboxylic porphyrins found in the faeces of rats poisoned with hexachlorobenzene have been separated by high-pressure liquid chromatography and characterized largely by spectroscopie methods. Their structures were confirmed by total synthesis, as part of a programme in which eleven of the fourteen hepta-, hexa- and penta-carboxylic porphyrins derived from uroporphyrin III have now been synthesized as their methyl esters. The four isomeric heptacarboxylic and three of the pentacarboxylic porphyrinogens have been incubated with haemolysates of chicken erythrocytes, and they are all converted into protoporphyrin IX but at different rates. On the basis of this and other evidence we conclude that the decarboxylation of uroporphyrinogen III to coproporphyrinogen III is a stepwise process taking place by a preferred pathway (both in normal and abnormal metabolism); the acetic acid groups are decarboxylated in a sequential clockwise fashion starting with that on the D ring and followed by those on the A, B and C rings. In the poisoned rats the uroporphyrinogen decarboxylase enzyme (or group of enzymes) is probably partially inhibited and the pentacarboxylic porphyrinogen with an acetic acid group on ring C accumulates. The latter is then transformed by a side pathway into dehydroisocoproporphyrinogen and thence into dehydroisocoproporphyrin and its congeners.

Animals↗
PubMed1976

Lack of breast feeding and early weaning in infants of Asian immigrants to Wolverhampton.

Fifty Asian immigrant mothers who would have expected to breast feed their infants had they remained in rural Asia were studied. There was a striking reduction in the incidence and duration of breast feeding on arrival in the United Kingdom, and a fall in the age of weaning. The availability of an alternative to human milk is the most important factor reducing the incidence of breast feeding. Only 2 (4%) of the 46 infants followed prospectively were breast fed. Reasons for not breast feeding were sought and the results indicated that the majority of mothers were frightened, misinformed, or apathetic about breast feeding. If breast feeding is to be promoted, antenatal education and encouragement is essential. The advantages of human milk need to be stressed. Potentially serious mistakes occurred in preparing bottle feeds, and vitamin supplements were often inadequate. Later weaning could be encouraged by the staff of well baby clinics.

Attitude↗
PubMed1976

Hepta- and hexa-carboxylic porphyrinogen intermediates in haem biosynthesis.

In the course of our studies on intermediates in normal and abnormal metabolism of porphyrins we have synthesised a number of porphyrins related to uroporphyrin-III and compared them with materials isolated from natural sources. In the present paper we show that the corresponding porphyrinogens are all metabolised to protoporphyrin-IX by haemolysates of chicken erythrocytes, but at different rates. The results are discussed in relation to our conclusions concerning the preferred pathway of degradation of uro'gen-III to coproporphyrinogen-III, which indicate a clockwise sequence of decarboxylation reactions.

Animals↗
PubMed1976

Pentacarboxylic intermediates in haem biosynthesis.

The incorporation of the four possible type III porphyrinogens into protoporphyrin is described and their various rates or conversion are discussed. The techniques used involved the incubation of the porphyrinogens in chicken red cell haemolysates followed by extraction and characterisation of the end products on HPLC and TLC. Porphyrin 5 b c d was shown to be more slowly incorporated than porphyrins 5 a b d, 5 a c d and 5 a b c. The relevance of these findings to an understanding of the porphyrin excretion pattern in hepato-erythrocitic porphyria is considered.

Animals↗
PubMed1975

Applications of high-pressure liquid chromatography and field desorption mass spectrometry in studies of natural porphyrins and chlorophyll derivatives.

Mixtures of porphyrins derived from natural sources can be readily separated by high-pressure liquid chromatography both analytically and on a preparative scale. A variety of procedures have been developed not only for the esters but also for free acids, and on the analytical scale quantitation is easily achieved by visible absorption. The retention times are largely characteristic of the number of carboxylic acid side chains (or other polar groups) but further information can be obtained by mass spectrometric studies of the various fractions. Field desorption mass spectrometry is particularly useful for this purpose because the emitter wire can be dipped directly into the eluates. The field desorption spectra of porphyrin free acids and esters as well as their metal complexes give essentially molecular ions with little or no fragmentation in most cases, whereas electron-impact mass spectrometry, particularly of free acids, is impeded by the low volatility of porphyrins. Mixtures can also be analysed by field desorption mass spectrometry, and this provides not only a rapid qualitative assessment of the components of a mixture, but also a check on the subsequent chromatographic separations.

Absorption↗
PubMed1975

Mucosal adherence of human enteropathogenic Escherichia coli.

An in-vitro assay system has been developed to measure bacterial adhesion to the mucosa of human fetal small intestine. Two strains of Escherichia coli that are proven human enteropathogens (E.P.E.C.) have been shown to adhere in large numbers, compared with control organisms. The attachment mechanism is species specific and is not caused by common fimbriae. Mucosal adhesion may be as important as enterotoxin production or invasiveness in determining the virulence of some strains of human E.P.E.C.

Adhesiveness↗
PubMed1975

The agglutinating antibody response in the duodenum in infants with enteropathic E. coli gastroenteritis.

The agglutinating antibody responses in duodenal fluid and serum were measured serially in 15 infants with enteropathogenic E. coli gastroenteritis. Peak levels of duodenal agglutinins were recorded eight to 18 days after the onset of symptoms, and the titres fell within the next seven to 14 days. These antibodies were mainly of the IgA class but IgM antibodies were detected early in the response, especially in the youngest infants. Serum antibody responses were detected in eight patients, but they correlated poorly with the titres of intestinal antibodies. No rise in serum antibodies was found in six infants. Further studies are required to determine whether these differences are host-derived or whether they reflect different pathogenic properties of the infecting organisms.

Agglutinins↗