Search PubMed⌕ Search

Biomedical subjects

A Allen

Publications and source records attributed to A Allen.

At least 289 records · Page 16Linked to original sources
PubMed1982

A simple method for measuring thickness of the mucus gel layer adherent to rat, frog and human gastric mucosa: influence of feeding, prostaglandin, N-acetylcysteine and other agents.

1. A technique has been developed for measuring thickness of the gastric surface mucus gel layer. Mucosal sections (1.6 mm) were cut from frog and rat stomach and human antrum, mounted transversely and viewed by an inverse microscope (x 200 magnification) under dark field illumination or phase contrast. The mucus layer was readily distinguishable and its dimensions could be recorded by means of an eyepiece graticule. 2. Mean mucus gel thickness in rat, frog was 73, 76, 55 and 192 micrometer respectively. However, there was variation in the average thickness of the gel layer between individual mucosae from the same species (up to twofold). Mucus thickness between adjacent regions of the same mucosal section also varied markedly (up to tenfold). 3. Topical administration of 16,16-dimethylprostaglandin E2 by oral intubation caused a significant increase in thickness in both rat and frog at doses of 5 microgram/ml and 0.5 microgram/ml respectively. Feeding and exposure of the mucosa to N-acetylcysteine (10-20%, w/v) produced variable effects whereas pepsin (1 mg/ml) caused a marked reduction in thickness of the surface gel layer in both rat and frog. 4. The technique provides a rapid and simple method for determining gastrointestinal mucus thickness in relation to mucosal morphology. It is ideally suited for studying the control of mucus secretion and effect of drugs.

16,16-Dimethylprostaglandin E2↗
PubMed1982

Changes in the structure of the mucous gel on the mucosal surface of the stomach in association with peptic ulcer disease.

The glycoprotein of human gastric mucus has been isolated and purified from mucous gel scraped from the surface of resected mucosa. All samples of mucus when analyzed by gel filtration were found to contain native, gel-forming, polymeric glycoprotein, together with varying amounts of the lower-molecular-weight glycoprotein. The galactosamine and glucosamine content of the lower-molecular-weight glycoprotein was the same as that for the native polymeric glycoprotein. The absence of serum glycoproteins and proteoglycans in the glycoprotein preparations was demonstrated. Gastric mucus from normal mucosa obtained by resection of the antrum during pancreatoduodenectomy, from duodenal ulcer patients, and from gastric ulcer patients contained 33.4% +/- 5.1%, 50.2 +/- 3.3%, and 65.1 +/- 2.8%, respectively, of the lower-molecular-weight glycoprotein. These results show the total mucous gel of the gastric ulcer group [and to a lesser extent, of the duodenal ulcer group] contains more lower-molecular-weight mucous glycoprotein, which from previous studies in vitro would suggest a weaker mucous gel structure.

Adult↗
PubMed1981

A 70000-molecular-weight protein isolated from purified pig gastric mucus glycoprotein by reduction of disulphide bridges and its implication in the polymeric structure.

The glycoprotein of pig gastric mucus has been isolated free of non-covalently bound protein as judged by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and equilibrium density-gradient centrifugation. After reduction with 0.2 M-mercaptoethanol, protein was released from the glycoprotein, which consisted of a major 70000-mol.wt. component and a minor 60000-mol.wt. component. The 70000-mol.wt. protein fraction was separated from the reduced glycoprotein by either density-gradient centrifugation in CsCl or by gel filtration. Analysis of the 70000-mol.wt. protein fraction showed that, within the limits of the analysis, it was non-glycosylated, and its amino acid analysis was quite different from that of the reduced glycoprotein, which is high in serine, threonine and proline. There was a ratio of one 70000-mol.wt. protein per native glycoprotein molecule of 2 X 10(6) mol.wt. Dissociation of the native glycoprotein into glycoprotein subunits (5 X 10(5) mol.wt.) by reduction or proteolysis results in the release or hydrolysis respectively of the 70000-mol.wt. protein. A similar 70000-mol.wt. protein is demonstrated in human gastric mucus glycoprotein. A structural role for the proteins in these mucus glycoproteins is proposed.

Amino Acids↗
PubMed1981

Isolation and characterization of the native glycoprotein from pig small-intestinal mucus.

Glycoprotein from pig small-intestinal mucus was isolated free of non-covalently bound protein and nucleic acid with a yield of over 60%. No non-covalently bound protein could be detected by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis or by equilibrium centrifugation in a density gradient of CsCl with 4 M-guanidinium chloride. The intrinsic viscosity and reduced viscosity of the glycoprotein preparations rose with the removal of non-covalently bound protein and nucleic acid from the glycoprotein, evidence that non-covalently bound protein does not contribute to the rheological properties of the glycoprotein in the mucus. The pure glycoprotein, in contrast with impure preparations, gelled at the same concentration of glycoprotein as that present in the gel in vivo. The glycoprotein was a single component, as judged by gel filtration and analytical ultracentrifugation. The distribution of sedimentation coefficients was polydisperse but unimodal with an s025,w of 14.5S and a molecular weight of 1.72 X 10(6). The chemical composition of the glycoprotein was 77% carbohydrate and 21% protein, 52% of which was serine, threonine and proline. The glycoprotein had a strong negative charge and contained 3.1% and 18.3% by weight ester sulphate and sialic acid respectively. The molar proportion of N-acetylgalactosamine was nearly twice that of any of the other sugars present, the glycoprotein had A and H blood-group activity and the average maximum length of the carbohydrate chains was deduced to be six to eight sugar residues.

Amino Acids↗
PubMed1981

Polymeric structure of pig small-intestinal mucus glycoprotein. Dissociation by proteolysis or by reduction of disulphide bridges.

Pig small-intestinal mucus glycoprotein, of molecular weight 1.72 X 10(6), is cleaved by Pronase digestion into glycoprotein subunits of molecular weight 4.5 X 10(5). Of the protein component of the native glycoprotein 29% by weight was lost on Pronase digestion, with no loss of carbohydrate. The non-glycosylated region of the protein that was lost with proteolytic digestion had a broad spectrum of amino acid residues, in contrast with the glycosylated region of the protein, which was resistant to proteolysis and was rich in serine, threonine and proline residues. Reduction with 0.2M-mercaptoethanol dissociated the Pronase-digested glycoprotein subunits into smaller glycoprotein subunits of molecular weight 2.7 X 10(5). On reduction, the native glycoprotein was dissociated into subunits of molecular weight 2.4 X 10(5), a similar size to those obtained from reduction of the Pronase-digested glycoprotein. On reductive dissociation of the native glycoprotein, in addition to glycoprotein subunits, protein was also released principally as a component of 90000 molecular weight. This protein was separated quantitatively from the reduced glycoprotein in amounts compatible with one 90000-mol.wt. protein molecule per 1.72 X 10(6)-mol.wt. native glycoprotein molecule. No 90000-mol.wt. protein was released on reduction of the isolated Pronase-digested glycoprotein. Pig small-intestinal mucus glycoprotein is therefore a covalent polymer of glycoprotein subunits joined by disulphide bridges. This polymeric structure differs in important respects from that previously shown for gastric mucus, in particular with respect to the size and number of component subunits per native molecule.

Amino Acids↗
PubMed1981

Dietary sodium, erythrocyte sodium concentration, sodium-stimulated lithium efflux and blood pressure.

1. There was a significant positive relationship between sodium-stimulated lithium efflux and systolic blood pressure (r = 0.512) in erythrocytes of black school children. Weight was also positively and significantly correlated with blood pressure. Although erythrocyte sodium concentration did not bear any significant relationship with blood pressure, it did bear significant inverse relationship with urinary sodium excretion. 2. High-school students were randomly assigned to either the experimental or the control group. In the former a reduction of about 70% in salt intake was achieved. After 24 days, the erythrocyte sodium concentration was significantly reduced in the experimental group. A non-significant decline in systolic blood pressure was observed in the experimental group; no change was detectable in the control group for either erythrocyte sodium concentration or systolic blood pressure.

Adolescent↗
PubMed1981

Assessment of sensory function in the operating room utilizing cerebral evoked potentials: a study of fifty-six surgically anesthetized patients.

Sensory evoked potentials (visual, auditory, and somatosensory) were recorded from 56 patients at the time of surgery to monitor neural function during critical portions of the operation. Fluctuations in latency and amplitude of the components occurred with changes in depth of anesthesia, blood pressure, irrigation, and neural tissue manipulation. Most of these changes were only transient. Permanent changes in evoked potentials occurred with decompression of neural tissue and prolonged retraction. Transient changes were not associated with any change in postoperative neurological function whereas changes in evoked potentials that persisted through the operation were highly likely to be associated with a postoperative change.

Adolescent↗
PubMed1981

Psychosocial factors in cancer.

Proper attention to psychosocial factors may be important in the long-term outcome of a patient with cancer. If the physician makes the patient a partner in the treatment program, compliance problems are overcome and the patient retains a sense of importance. Communication with the patient and the patient's family is essential throughout all stages of management. The physician should treat the patient with respect, openness and empathy.

Adaptation, Psychological↗
PubMed1980

Sleep apnoea in acromegaly.

Day time somnolence or excessive snoring, or both, occurred in five out of 11 patients with acromegaly. All five had episodes of sleep apnoea, and three had the sleep apnoea syndrome. Growth hormone concentrations were higher (p less than 0.025) in these patients than in the six patients without these symptoms. One patient with daytime somnolence and one asymptomatic patient had flow loop evidence of upper airways obstruction. Two of the patients with the sleep apnoea syndrome had cardiomegaly. Sleep apnoea appears to be common and clinically important in acromegaly, and it may be central, obstructive, or mixed. Polygraphic nocturnal monitoring is indicated to assess these patients properly.

Acromegaly↗
PubMed1980

Sleep apnoea in Scheie's syndrome.

An 18-year-old student presented with a two-year history of daytime sleepiness and noisy breathing during sleep. Both he and his brother, aged 25 years, had Scheie's syndrome, a mucopolysaccharidosis characterised by small stature, micrognathia, corneal clouding, hepatosplenomegaly, raised urinary mucopolysaccharides, and undetectable levels of alpha-L-iduronidase assayed in cultured fibroblasts. Both brothers had sleep apnoea (apnoea index, 59 and 35 respectively) during which there was a significant fall in heart rate and arterial oxygen saturation. One brother had EEG changes suggestive of cerebral hypoxia and the other had ventricular extrasystoles at the end of several episodes. Tracheostomy in the younger brother produced a dramatic symptomatic improvement and reduced the number and severity of apnoeic episodes (post-tracheostomy apnoea index 2.4).

Adolescent↗