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Biomedical subjects

A Allen

Publications and source records attributed to A Allen.

At least 271 records · Page 15Linked to original sources
PubMed1984

Characteristics of glucose-stimulated breathing movements in human fetuses with intrauterine growth retardation.

The characteristics of fetal breathing movements were analyzed in 13 fetuses who were intrauterine growth retarded and in a comparison group of 13 well-grown fetuses. The numbers of minutes of breathing activity per hour were similar for the two groups; the increase (p less than 0.05) after maternally administered glucose was due to longer (p less than 0.05) and more frequent (p less than 0.05) breathing episodes, and was mainly deep breathing. The deep breathing rate increased significantly (p less than 0.05) after glucose. The two groups exhibited similar low occurrences of shallow breathing (less than 5 minutes per hour) throughout the experiments. No significant differences could be demonstrated between intrauterine growth-retarded and well-grown fetuses with respect to the amount, rate, and pattern of breathing activity during fasting or after oral administration of glucose to the mother.

Blood Glucose↗
PubMed1984

Mucus glycoprotein structure, gel formation and gastrointestinal mucus function.

Gastrointestinal mucus occurs as a water-insoluble gel adherent to the mucosal surfaces and as a viscous, mobile solution in the lumen. The adherent gastroduodenal mucus gel is part of the mucosal defence against acid (with HCO3-), pepsin (diffusion barrier) and mechanical damage. Rheological studies show that gastrointestinal mucus is a weak, viscoelastic gel. The size and physical properties of the isolated component glycoproteins depend critically on the methods used to obtain them. A glycoprotein preparation of Mr approximately 2 X 10(6), which possesses the gel-forming properties of the native mucus, is considered to represent the secreted covalent entity in pig gastric and small intestinal mucus. These glycoproteins have a polymeric structure of subunits joined by disulphide bridges between non-glycosylated regions of their protein cores. Glycoprotein polymerization, essential for gel formation, is deficient in gastric mucus in peptic ulcer disease. In vivo, adherent mucus gel forms a thin but continuous cover of variable thickness (rat 5-500 microns) over the gastroduodenal mucosa. Luminal pepsin rapidly dissolves this mucus cover and its continuity is maintained by fresh mucus secretion. Bile, HCl, 2 M-NaCl and ethanol (less than 40%) do not destroy mucus gel structure. Prostaglandins and carbachol increase mucus thickness, affording better protection, but it is thought that continuity of the protective mucus cover is the critical factor in its protective functions.

Animals↗
PubMed1984

Organotin implications in anticarcinogenesis. Background and thymus involvement.

A comprehensive study of the scientific literature regarding tin content in normal and pathogenic human tissue has disclosed that various organotin materials retard both the onset and growth of cancer in laboratory animals, and decreased tissue tin in humans may be associated with tumour development. Initial studies by the authors have shown that the thymus gland of the mouse possesses a relatively high concentration of tin and is also the major site of accumulation for 14C-labelled tri-n-butyltin fluoride (TBTF). When mammary cancer-prone mice with transplanted tumours were orally dosed continuously with this agent in their drinking water, the tumour growth rate was significantly reduced. Both mouse mammary tumours and human lung tumours show low tin content compared to normal body tissue.

Animals↗
PubMed1984

Gastric mucosal protective mechanisms: roles of epithelial bicarbonate and mucus secretions.

Secretion of HCO3 (amounting to 2-10% of maximum H+ secretion) in conjunction with the adherent mucus gel layer (functioning as a mixing barrier) protects gastric mucosa from luminal acid by a process of surface neutralization. Gastric HCO3 secretion is augmented by cholinergic agonists, prostaglandins and low luminal pH. Ulcerogens attenuate HCO3 secretion although passive diffusion of alkali consequent upon an increase in mucosal permeability may mask these inhibitory actions. Studies in vitro indicate that HCO3 transport in the stomach is dependent on oxidative metabolism, carbonic anhydrase activity and involves a CL exchange mechanism. Mucus, synthesized and released from epithelial cells, adheres to the mucosal surface as a thin (less than 80 microns in rat) but continuous gel layer. Prostaglandins and carbachol induced release of preformed mucus and thereby increase thickness, whereas acute exposure to ulcerogens has little effect on overall dimensions of the surface mucus layer. Measurements of pH gradients adjacent to gastric mucosa indicate that the disposal of luminal H+ occurs by extracellular neutralization. However, the fall in pH at the apical cell membrane when luminal pH is low (pH 1.5) suggests that while a mucus-bicarbonate barrier comprises the first line of mucosal defence, other factors are involved in the overall process of mucosal protection in the stomach.

16,16-Dimethylprostaglandin E2↗
PubMed1984

Cyclic nucleotides and glycoproteins during formation of cholesterol gallstones in prairie dogs.

Male prairie dogs received in standard diets either 0.08% cholesterol (control, n = 30) or 1.2% cholesterol (lithogenic, n = 31). Animals were killed at days 2-4, 7, 10, 21, and 39 to determine the temporal sequence of changes in mucosal cyclic adenosine 3':5'-monophosphate in the gallbladder and of cholesterol saturation, glycoproteins, cholesterol crystals, and gallstones in bile of prairie dogs fed a cholesterol-rich lithogenic diet. Glycoprotein concentration in bile in the lithogenic group was significantly elevated compared to controls on all days of death. Saturation of bile and formation of cholesterol crystals occurred only in the lithogenic group, detected first after 7 days of feeding. Gallstones were found in the lithogenic group only. Elevation of cyclic adenosine 3':5'-monophosphate in the mucosa of gallbladders was found in the lithogenic group only, beginning at day 10. In summary, increased glycoproteins in bile preceded cholesterol saturation and crystallization which, in turn, preceded increased mucosal cyclic adenosine 3':5'-monophosphate.

Animals↗
PubMed1984

Studies on gastrointestinal mucus.

Mucus is secreted throughout the gastrointestinal tract. The primary secretion is the water insoluble gel adherent to the mucosal surface but substantial amounts of mucus also occur in the lumen. The following are discussed: the functions of mucus; the structure and properties of mucus; study of the adherent mucus gel on the mucosal surface; the effects on mucus properties of proteolysis; thiol agents; bile salts; acid and hyperosmolar solutions. Much of our work on mucus has been with that from the stomach but where possible studies on the intestines and colon are discussed. Studies show that mucous secretions from the different regions of the gastrointestinal tract have similar rheological properties although the component glycoproteins differ in their detailed structure.

Animals↗
PubMed1984

Current concepts of gastroduodenal mucosal protection.

Mucosal protection against luminal acid and pepsin and recovery from acute damage in the upper gastrointestinal tract depends upon a number of interrelated mechanisms. The thin adherent mucus gel layer protects against shear and luminal pepsin and provides a mixing barrier for surface neutralization of H+ by HCO3- secreted from the underlying epithelia. Gastric HCO3- transport amounts to 2-10% of maximum H+ rate and involves a Cl- exchange mechanism. The rate of duodenal HCO3- transport is some 5-fold greater and both Cl- exchange and transcellular secretion of HCO3- occur. Blood flow ensures adequate oxygenation, provides a pool of HCO3- and maintains mucosal acid-base balance. Gastroduodenal mucosa has a high proliferative rate and in the stomach, the process of continual cell replacement is augmented by restitution of epithelial integrity following acute damage.

Animals↗
PubMed1984

Seventh-Day Adventist adolescents--life-style patterns and cardiovascular risk factors.

The life-style of adolescents attending a Seventh-Day Adventist boarding school was evaluated as it related to cardiovascular risk factors. The diet contained 34% calories as fat, with 11% derived from saturated fat. Total serum cholesterol levels were low (mean, standard deviation=138+/-15 mg per dl), and apolipoprotein B level was low as well (46+/-9 mg per dl). The high-density lipoprotein cholesterol level was within the usual range (52.4+/-13.3 mg per dl). Mean blood pressures were also low (systolic, 104.1+/-9.6 mm of mercury; diastolic, 65.7+/-9.7 mm of mercury). There was no self-reported use of cigarettes. If this life-style were to continue through adulthood, the incidence of premature atherosclerotic disease, particularly coronary artery disease, for this group might well be reduced, compared with other North Americans, as suggested by findings from previous studies of adult Seventh-Day Adventists.

Adolescent↗
PubMed1984

Significance of cone biopsy margins in the management of patients with cervical neoplasia.

Too many patients in the United States undergo hysterectomy for cervical neoplasia following cone biopsy because too many gynecologists choose not to pay attention to the pathology present at the margins of the cone specimen. In view of the need to improve the management of cervical neoplasia--i.e., to reduce the number of needless hysterectomies--a retrospective study was done to verify the trend in our institution and to evaluate the utilization of cone biopsy to determine the extent of the process. Also, the methods used for procuring the cone sample and for interpreting the results of the biopsy were studied. The present study included 345 patients who underwent a cone biopsy; subsequently, 102 of them had a hysterectomy. Based on the evaluation of the cases in this study, information was obtained about the performance of cone biopsy and the guidelines for determining when a hysterectomy should be performed and when other, less drastic means of eradicating the neoplasia should be considered.

Adult↗
PubMed1983

Dietary salt and blood pressure.

Research evidence on the role of dietary sodium in the etiology and pathogenesis of hypertension is briefly reviewed. This matter is assuming new importance at present, given new data on the efficacy of normalization of blood pressure for adults with so-called "mild" hypertension (average diastolic 90-104 mm Hg), hence the need for safe nutritional-hygienic alternatives to years-long drug treatment for millions of people with such hypertension. Two trials by the authors deal with some unresolved questions in this area. The first, a preliminary study, involved 21 lacto-ovo-vegetarian high school students living in a boarding school. With decrease in daily Na intake from 216 to 72 meq for the experimental compared with the control group, red blood cell Na concentration was significantly lower in the former; systolic pressure was slightly but not significantly lower. The second trial, the Primary Prevention of Hypertension, involves over 200 hypertension-prone persons aged 30-44, and explores the ability in the experimental group to reduce blood pressure and prevent development of hypertension by safe nutritional-hygienic means (weight reduction, dietary Na decrease, avoidance of excess alcohol, rhythmic exercise). Initial results at 6 months are presented. Trials on the prevention and control of hypertension by nonpharmacologic means, including reduced Na intake, and involving analyses of the inter-relationships among dietary Na, other dietary factors, Na metabolism, and blood pressure in samples from different population strata, are an important present-day research need.

Adolescent↗
PubMed1983

Gastric and duodenal HCO3- transport in vivo: influence of prostaglandins.

Gastric and duodenal HCO3- transport was compared in the same mammalian species (cat) in vivo. The most appropriate technique for detecting HCO3- in the lumen of the stomach was measurement of pH and CO2 tension, whereas in the duodenum it was pH-stat titration. For experiments on gastric HCO3- transport, conscious cats prepared with vagally denervated fundic pouches were used; for those on duodenal transport anesthetized animals with in situ perfused segments were studied. When expressed in terms of gross surface area, basal HCO3- output was six times greater in the duodenum than in the stomach (approximately 1.5 cf. approximately 0.25 mumol X cm-2 X 15 min-1). topical application of 16,16-dimethyl prostaglandin E2 (dmPGE2) to duodenal mucosa caused a concentration-dependent increase in HCO3- output and transmucosal electrical potential difference (PD) over the range 0.01-1.0 microgram X ml-1. PGE2 was approximately 200 times less potent than dmPGE2 as a stimulant of duodenal HCO3- transport. Increases in the rate of luminal HCO3- output following application of dmPGE2 were considerably less in the stomach compared with the duodenum (approximately 50% cf. approximately 1,000% at 1 microgram X ml-1). Intravenous dmPGE2 (1 microgram X kg-1 X h-1) had no effect on either gastric or duodenal HCO3- outputs. Indomethacin (5 mg X kg-1 iv) inhibited duodenal HCO3- output by approximately 50% and reduced PD but did not influence gastric HCO3- output. We propose that in the cat duodenum in vivo local prostaglandins regulate HCO3- transport, but in the cat stomach in vivo they have a less important role.

Animals↗
PubMed1982

The effect of maternal glucose infusion on breathing movements in human fetuses with intrauterine growth retardation.

forty-nine patients with suspected intrauterine growth retardation (IUGR) were studied under rigid experimental conditions to determine baseline fetal breathing movement (FBM) activity and the response to 90-minute maternal glucose infusion, as compared to that of normal control subjects. Patients with IUGR showed a normal amount of FBMs during maternal fasting. All groups exhibited a significant increase in FBMs after glucose was administered. During the final 60 minutes of the glucose infusion, the severe IUGR group (weight for gestational age less than the third percentile) showed less FBM activity (p less than 0.01) than the other study and control groups.

Adult↗