Commission questions existence of RN shortage.
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Employment↗
Biomedical subjects
A Allen
Publications and source records attributed to A Allen.
Submaxillary mucins. Intermolecular interactions and gel-forming potential of concentrated solutions.
The intermolecular interactions in concentrated solutions of pig submaxillary mucin (PSM) and sheep submaxillary mucin (SSM) were studied by mechanical spectroscopy. PSM and SSM were purified from detectable protein and nucleic acid by equilibrium centrifugation in a CsCl density gradient. PSM and SSM isolated in the presence of proteinase inhibitors showed distinct differences from preparations isolated in the presence of 0.2 M-NaCl alone, the latter having a carbohydrate and amino acid analysis similar to other preparations isolated by precipitation or ion-exchange techniques. Gel-filtration studies showed that preparations isolated in the presence of 0.2 M-NaCl alone were dissociated into smaller-sized glycoprotein units by 3.5 M-CsCl or 2.0 M-NaCl (SSM), pH 2.0 (PSM) or heating at 100 degrees C for 10 min (PSM and SSM). Preparations isolated in the presence of proteinase inhibitors were not dissociated by these treatments. Proteolysis fragmented all submaxillary mucin preparations into small glycopeptides of Mr 13,700 for PSM and of Mr 14,000 and 15,000 for SSM. PSM preparations when concentrated formed viscoelastic gels, as determined by mechanical spectroscopy. In contrast, SSM showed characteristics of a weak viscoelastic liquid under comparable conditions (coil overlap). PSM glycoprotein isolated in proteinase inhibitors formed weak viscoelastic gels at concentrations between 5 and 15 mg/ml. Preparations of PSM glycoprotein isolated in the presence of 0.2 M-NaCl (concentration 10-97 mg/ml) had the same overall mechanical gel structure as those preparations extracted in the presence of proteinase inhibitors. This gel structure was seen to collapse following proteolysis of both preparations or after acid treatment of the glycoprotein isolated in the presence of 0.2 M-NaCl, consistent with the breakdown in size of the polymeric glycoprotein. Treatment of PSM gel with 0.2 M-2-mercaptoethanol caused a surprising increase in gel strength, which was further markedly increased on removal of the reducing agent by dialysis. An association of reduced subunits of PSM was observed by gel filtration after removal of 0.2 M-2-mercaptoethanol. These results point to intermolecular disulphide exchange occurring on reduction of these PSM glycoprotein preparations. These results demonstrate that gel formation in PSM glycoprotein is similar to that for other gastrointestinal mucus glycoproteins from stomach to colon. Gel formation in PSM, as in other mucins, depends on polymerization of subunits.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Mucus glycoprotein gels. Role of glycoprotein polymeric structure and carbohydrate side-chains in gel-formation.
The structure of mucus glycoprotein gels from the pig gastrointestinal tract was investigated by mechanical spectroscopy. Gastric, duodenal, and colonic mucus had the same mechanical profile, characteristic of a viscoelastic gel. The gel structure collapsed on destruction of the polymeric structure of the component glycoprotein by reduction with 0.2M mercaptoethanol or after proteolysis with papain. The progressive weakening of mechanical properties and the decrease in polymeric glycoprotein content were measured as functions of time of reduction. A linear correlation was obtained between the gel quality [defined by tan delta, the ratio of the loss modulus (G'') to the storage modulus (G')] and the proportion of polymeric to subunit glycoprotein in the mucus. Purified mucus glycoprotein, at the same concentration as that in native mucus, resulted in a gel with mechanical properties no different from those of the respective native secretion, demonstrating that the glycoprotein alone could reproduce the gel-forming properties of mucus. After proteolytic digestion, all native secretions and reconstituted mucus showed an absence of Newtonian behaviour in the frequency dependence of dynamic viscosity at low frequencies. This provided evidence that the noncovalent interactions, characteristic of the native gel matrix, were still present after proteolytic digestion when the nonglycosylated protein core accessible to proteinases had been removed. These results were interpreted to show (a) a common mechanism for gel-formation in gastric, duodenal, and colonic mucus; (b) that the polymeric structure of mucus glycoproteins confers the three-dimensional structure necessary for formation of the gel network; and (c) that noncovalent interactions which arise between the glycoprotein molecules by relatively stable interdigitation of the carbohydrate side-chains are involved in formation of the gel network.
Animals↗
Smoking-related disease in a VA hospital.
An inpatient population was studied to assess the contribution of smoking to the cause of their hospitalization. We established a new methodology to assess a patient population for smoking-related disease, and found that, during a 24-hr period, 32% of all medical and surgical patients studied were hospitalized with smoking-related disease. Moreover, 17% of all medical and surgical patients were hospitalized for diseases that were very highly related to smoking (with risk-ratios greater than 5). On certain services these percentages were much higher. Smoking-related diseases account for a significant proportion of the hospitalizations at the Kansas City Veterans Administration Hospital.
Adult↗
The effect of 50 Hz external electrical interference on implanted cardiac pacemakers.
The effects of injected 50 Hz alternating current on the function of cardiac pacemakers has been observed in 18 patients with implanted unipolar VVI units. Current, in the range 0-600 microA was applied via electrodes attached to the patients' upper body and feet and fed from a specially designed current injection unit at the bedside. Most implanted pacemakers reverted to interference mode in the current range 29-250 microA. At current levels just below the reversion current all units developed irregular and inappropriate pacing. This current level was pacemaker dependent and varied in the range 27-246 microA. The total reversion current depended on the location of the injecting electrodes and on the patients' posture. The sensitivity of the units to injected interference was increased by deep inspiration. Temporary pacing catheters fitted to an additional ten patients were used to monitor the interference voltage which would be sensed by an implanted unit. This voltage was similarly dependent on patient posture and on deep respiration. Current injection has proved to be a safe, controllable and reproducible method of testing the sensitivity of implanted pacemakers to 50 Hz external interference.
Aged↗
Pepsins and the mucus barrier in peptic ulcer disease.
Studies show that the gastroduodenal mucosal barrier is damaged by pepsin under conditions in which it is resistant to acid alone. The continuous layer of adherent mucus gel provides a diffusion barrier to luminal pepsin, preventing its access to the underlying epithelium. Pepsin has mucolytic activity and will progressively digest the adherent mucus layer at its luminal surface, although normally this is balanced by secretion of new mucus to maintain a continuous barrier. In peptic ulcer disease the proportion of peptic activity in gastric juice attributable to pepsin type 1 is significantly raised (four to five-fold). Pepsin 1 has increased mucolytic activity compared with the major component, pepsin 3, both at the optimal pH of 2 (twofold increase in activity) and at higher pH values up to pH 5 (sixfold increase in activity at pH 4). Structural studies show that the gel forming polymeric mucin of the antral adherent mucus barrier is deficient in peptic ulcer disease. This breakdown of the mucus barrier in peptic ulcer patients can be attributed to the increased pepsin activity of gastric juice seen in this disease, although other explanations are also possible. The increased pepsin activity of gastric juice in peptic ulcer patients is compatible with the concept 'no acid, no pepsin, no ulcer'.
Gastric Acid↗
Accepting the challenge of excellence.
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Humans↗
The mucus barrier. Its role in gastroduodenal mucosal protection.
A layer of water-insoluble mucus gel has been shown to form a continuous cover over the gastroduodenal mucosal surfaces, of median thickness of 180 micron in stomach in humans. This adherent mucus is the first line in mucosal defence against the natural aggressors, acid and pepsin, in the lumen. Mucus gel provides a stable unstirred layer that supports surface neutralisation of acid by mucosal bicarbonate. Mucus gel is a diffusion barrier to pepsin in the lumen, preventing proteolysis of the underlying epithelial cells. There is, however, a dynamic balance between digestion by pepsin of the mucus layer at its luminal aspect and secretion of new mucus by the epithelium. There is evidence that, in peptic ulcer disease, the rate of peptic degradation of the mucus barrier is increased. Exogenous damaging agents such as ethanol and aspirin permeate the gel matrix of the mucus barrier, rapidly damaging the underlying epithelium. The subsequent reepithelialisation process is protected by a gelatinous coat over ten times thicker than the original adherent mucus layer. This gelatinous coat is primarily a fibrin-based gel with necrotic cells and mucus.
Animals↗
Bedside nurses: an endangered species.
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Allied Health Personnel↗
Training and needs of health visitors in the haemoglobinopathies.
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Community Health Nursing↗
Early intravenous indomethacin prolongs respiratory support in very low birth weight infants.
Infants weighing 1500 g at birth requiring either intermittent positive pressure ventilation or continuous positive airway pressure by 12 hours of age were entered in a randomized double blind controlled trial to test the efficacy of early intravenous indomethacin therapy in preventing chronic pulmonary disease of prematurity. Of the 30 newborns enrolled, 15 were treated with indomethacin and 15 were treated with placebo at 12, 24 and 36 hours of age. The groups were similar for birth weight, gestational age, sex, hyaline membrane disease and intracranial hemorrhage. Infants in the placebo group were successfully weaned from intermittent positive pressure ventilation at an earlier age than infants in the indomethacin group (p less than 0.05). Furthermore, chronic pulmonary disease of prematurity was similar in the two groups despite a reduction in the incidence of patent ductus arteriosus in the indomethacin group.
Clinical Trials as Topic↗
Formation of a fibrin based gelatinous coat over repairing rat gastric epithelium after acute ethanol damage: interaction with adherent mucus.
A gelatinous coat, heterogeneous in appearance, was formed over damaged rat gastric mucosa recovering from acute ethanol injury. This coat, in places 1.6 mm thick (median thickness 680 microns), was 10 times thicker than the translucent layer of adherent mucus (median thickness 70 microns) covering the undamaged mucosa. Immunohistochemistry and periodic acid Schiff staining showed this gelatinous coat to be predominantly a fibrin gel with an exterior layer rich in mucus and necrotic cells. The plasma clotting time was significantly decreased in vitro by pig gastric mucus gel and soluble mucus glycoprotein (90% and 13% respectively) suggesting that in vivo the mucus layer remaining after epithelial damage could act as a template for fibrinogen-fibrin conversion. These results show that a fibrin based gelatinous coat, quite distinct from the adherent mucus layer and with considerable protective potential could be formed over the repairing rat gastric mucosa after acute ethanol damage.
Animals↗
Humor in psychotherapy: a view.
This paper offers a perspective on the use of humor as both an assessment tool and as a therapeutic tool within the context of a psychodynamic approach to psychotherapy. While mindful of the potential difficulties which attend its introduction into the treatment situation there is an attempt to balance this position through a consideration of the appropriate conditions and modes of operation under which a humor-enriched approach may be efficacious. Ultimately, the paper concludes that proper employment requires an informed awareness of the risks and benefits along with the parameters for its use.
Humans↗
Gastroduodenal mucosal defence mechanisms and the action of non-steroidal anti-inflammatory agents.
This review summarises gastroduodenal protective mechanisms, the actions of non-steroidal anti-inflammatory (NSAI) agents on mucus and HCO3 secretions, and the basis of gastric mucosal injury induced by acetylsalicylic and salicylic acids (ASA and SA). Resistance to autodigestion by acid and pepsin present in gastric juice is multifactorial involving pre-epithelial (mucus-bicarbonate barrier) and post-epithelial (blood flow, acid-base balance) factors in addition to properties of the surface cell layer per se. The latter includes mucosal re-epithelialisation, a property which appears particularly important with respect to recovery from acute injury. A range of NSAI agents (ASA, fenclofenac, ibuprofen and indomethacin) inhibit gastric HCO3 transport in isolated mucosal preparations. Inhibition of duodenal HCO3 transport has been demonstrated in response to indomethacin in vitro and in vivo. These effects on secretion can be antagonised by exogenous prostaglandins of the E series. The layer of secreted mucus gel overlying the epithelial surface is not affected by NSAI drugs in the short term. However a number of these agents have been shown to inhibit glycoprotein biosynthesis by the epithelial cells. Thus loss of this protective coat could be anticipated during chronic drug exposure since erosion of adherent mucus by luminal shear and proteolysis would not be compensated by continued secretion. Detailed analysis of the gastric mucosal injury induced by salicylates both in vitro and in vivo reveals that much of the damage previously attributed to ASA is in fact due to the metabolic product SA. In this respect it is concluded that mucosal injury caused by ASA is due to a combination of two factors.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The gastric mucosal epithelial barrier: role of mucus and fibrin.
A continuous layer of insoluble mucus gel is adherent to the luminal surface of the gastric epithelium. The true thickness of the gel and its continuity can only be observed on unfixed sections of mucosa since histological fixatives cause dehydration and denaturation of mucus. The mucus:bicarbonate barrier can protect the undamaged epithelium from the endogenous luminal aggressors acid and pepsin but does not appear to offer much protection against exogenous damaging agents such as topical alcohol. Following acute ethanol injury, damaged epithelium is replaced by cells migrating from the gastric pits. In rat gastric mucosa this process of re-epithelialisation is protected by a gelatinous coat ten times thicker than the normal adherent mucus layer. Our studies now show this coat to be a fibrin gel with mucus and necrotic cells. Evidence suggests that the existing mucus layer can act as a template for the fibrinogen--fibrin conversion. These results demonstrate that a fibrin based gelatinous coat, quite distinct from the adherent mucus layer and with considerable protective potential, can be formed over the repairing damaged gastric mucosa.
Animals↗
Mechanical characterization and properties of gastrointestinal mucus gel.
Mechanical spectroscopy has been used to study the structure of mucus gel taken from the surface of the pig gastrointestinal tract. Mucus from stomach, duodenum and colon was insoluble and its mechanical properties, characteristic of a weak viscoelastic gel, were unchanged in saline, acid (pH 2) and denaturants. Small intestinal mucus gel which was of poorer quality, was disrupted following exposure to acid and denaturants. Concentration of purified glycoprotein produced gels that had mechanical spectra with the same profiles as the respective native secretion except for reconstituted small intestinal mucus which was of better quality and similar to the other native and reconstituted gels. Reduction of S-S linkages or proteolysis of all mucus gels caused a collapse of structure to give profiles typical of a viscous solution. This collapse of gel structure was shown to result from a breakdown of the covalent polymeric structure of the component glycoproteins. A linear correlation for mucus gels was observed between gel quality (as defined by tan delta) and the ratio of polymeric glycoprotein to its degraded lower molecular weight subunit. Human gastric mucus from a histologically normal stomach also had the characteristics of a weak viscoelastic gel, although that from patients with peptic ulcer disease has a significantly reduced content of polymeric glycoprotein.
Animals↗