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Biomedical subjects

P J Hanson

Publications and source records attributed to P J Hanson.

At least 19 recordsLinked to original sources
PubMed1992

Nitric oxide donors increase mucus gel thickness in rat stomach.

Instillation of the nitric oxide (NO) generator isosorbide dinitrate (0.1-1 mM) into the rat gastric lumen in vivo produced a dose-related increase in mucus gel thickness that was prevented by coadministration of oxyhaemoglobin (10 microM). Isosorbide dinitrate did not induce epithelial cell damage. S-Nitroso-N-acetyl-penicillamine (0.3 mM) and dibutyryl cyclic GMP (1 mM) also increased mucus thickness. These findings, along with the presence of NO synthase in the gastric mucosa, imply a role for NO in vivo in mediation of gastric mucus release.

Animals↗
PubMed1992

Differential distribution of nitric oxide synthase between cell fractions isolated from the rat gastric mucosa.

Cells isolated from the rat gastric mucosa were resolved into two fractions on a percoll density gradient, and into five fractions using counterflow centrifugation (elutriation). Ca(2+)-dependent nitric oxide synthase (NOS) activity was found in the high density percoll fraction but not in the parietal cell enriched low density fraction. This activity was inhibited by NG-monomethyl-L-arginine with an IC50 of 3.7 microM. Cells in the elutriator fraction rich in mucous-epithelial cells exhibited the highest NOS activity, while the smaller cell fractions had no detectable NOS yet had the highest basal release of prostaglandin E2. The parietal cell enriched elutriator fraction again had low NOS activity. The activity of a constitutive NOS in the mucous-cell fraction may indicate a role of NO in the regulation of epithelial cell integrity or secretion.

Amino Acid Oxidoreductases↗
PubMed1992

Protein kinase C inhibits stimulation of adenylate cyclase by the histamine H2 receptor in rat parietal cells.

The action of protein kinase C on the stimulation of adenylate cyclase activity by the histamine H2 receptor was investigated in rat parietal cells. Protein kinase C was activated by preincubating cells with 12-O-tetradecanoylphorbol 13-acetate (TPA), and adenylate cyclase activity was measured in sonicated extracts. TPA (100 nM) inhibited adenylate cyclase activity stimulated by histamine (100 nM-500 microM). This effect was related to the concentration of TPA. TPA (100 nM) enhanced the stimulation of adenylate cyclase activity by forskolin (100 microM) but had no effect on the stimulation by NaF (10 mM). In conclusion, protein kinase C inhibits stimulation of adenylate cyclase by the histamine H2 receptor. This action could be mediated by changes in the number of affinity of histamine H2 receptors or in the coupling of the receptor to the stimulatory guanine nucleotide regulatory subunit Gs.

Adenylyl Cyclases↗
PubMed1992

A study of glutaraldehyde disinfection of fibreoptic bronchoscopes experimentally contaminated with Mycobacterium tuberculosis.

Mycobacteria are difficult to inactivate, and concern about the spread of tuberculosis at bronchoscopy has a major influence on infection control practices. Recommendations from the UK Department of Health are based largely on in-vitro mycobactericidal assays which do not take into account the particular conditions encountered in endoscopy units. In this applied study cleaning and disinfection methods were examined using five bronchoscopes that were heavily contaminated with a recent isolate of Mycobacterium tuberculosis in sputum. Cleaning reduced contamination by a mean 3.5 log(10) colony forming units (cfu) per ml; all bronchoscopes were free of detectable mycobacteria after 10 min in 2% alkaline glutaraldehyde (AG). It is recommended that all bronchoscopes be thoroughly pre-cleaned and disinfected in 2% AG for 20 min as part of a uniform policy of infection control.

Bronchoscopes↗
PubMed1992

Symptomatic cysts in otherwise normal lungs of children and adults.

The clinical and pathological features of 28 lung cysts resected in the period 1980-1989, excluding those from patients with emphysema elsewhere in their lungs, have been reviewed. In 12 children aged 8 days to 17 years, five cysts were congenital adenomatoid malformations, three were bronchogenic cysts, two were intralobar sequestrations, one was a cystic haemangioma and one resembled the cysts excised from 16 adult patients. This latter group ranged in age from 20 to 62 years and included 11 cigarette smokers and five asthmatics. Twelve of these cysts were intralobar and four were attached by a pedicle to the pleural surface of the lung. All these cysts had a fibromuscular wall showing varying degrees of acute and chronic inflammation. The presence of at least a partial lining of epithelial cells in all the cysts was confirmed using an immunocytochemical marker. The surrounding lung did not show any significant pathology. These cysts are labelled as simple fibromuscular pulmonary cysts. In the childhood cases, a congenital cause could be established in the majority. The pathogenesis of the adult cysts remains unclear. The presence of inflammation in the cyst walls does not necessarily suggest a role for infection, as secondary infection of cysts cannot be ruled out. An aetiological role for local damage due to cigarette smoking or asthma must be taken into consideration.

Adolescent↗
PubMed1991

Viral transmission and fibreoptic endoscopy.

Fibreoptic endoscopes have been responsible for outbreaks of infection with bacteria although viral transmission has been reported only once. The emergence of human immunodeficiency virus (HIV) has prompted a review of infection control practices in endoscopy units because of the theoretical possibility that HIV might be transmitted at endoscopy. Recent studies have shown that bronchoscopes and gastroscopes used on AIDS patients become contaminated with HIV genetic material although cleaning equipment in detergent removes all traces of the virus. Thorough precleaning has been shown to eliminate even high titres of HIV from endoscopes and 2% alkaline glutaraldehyde has been found to inactivate the virus rapidly even if the virus is dried in serum to a surface. These findings support the British Society of Gastroenterology recommendations for the cleaning and disinfection of endoscopic equipment and demonstrate that a uniform policy of infection control is practicable in endoscopy units.

DNA, Viral↗
PubMed1991

Recovery of the human immunodeficiency virus from fibreoptic bronchoscopes.

Ten bronchoscopes that had been used on patients with the acquired immunodeficiency syndrome were sampled to determine the nature and extent of microbial contamination. Samples were taken by irrigating the suction biopsy channel with modified viral transport medium and by swabbing the insertion tube. Sampling was repeated after they had been cleaned in detergent and after two minutes' disinfection in 2% alkaline glutaraldehyde. Before being cleaned the seven bronchoscopes tested by polymerase chain reaction were contaminated with the human immunodeficiency virus, though infectivity and antigen assays gave negative results. Other organisms identified were hepatitis B virus (1), commensal bacteria (9), and Pneumocystis carinii (4). Mean bacterial contamination was 2.27 log colony forming organisms per millilitre. Cleaning the bronchoscope before disinfection removed all detectable contaminants with a reduction in bacterial growth of up to 8 log colony forming units/ml.

Bronchoscopes↗
PubMed1990

AIDS: practising safe endoscopy.

The emergence of HIV has provoked a widespread reappraisal of infection control practices in endoscopy units. Infection control practices should be applied to all patients alike without recourse to selection or screening. Although there has only been one reported instance of viral transmission at endoscopy, HIV could in theory be transmitted by a contaminated endoscope. Experience suggests that this is more likely to occur from damaged endoscopes, if an unsuitable disinfectant is used or endoscopes are not precleaned. In-use studies have shown that HIV contaminates endoscopes used on patients with AIDS, but in amounts too small to cause infection in tissue cultures. Cleaning in neutral detergent is extremely effective in removing contaminating micro-organisms, including HIV, from endoscopes. Aldehydes are the disinfectants of choice, but any disinfectant may fail if organic material is not removed by cleaning. After thorough cleaning, short disinfection times (e.g. four minutes) ensure inactivation of all relevant micro-organisms except Cryptosporidium and mycobacteria, although in practice even these organisms are likely to be reduced to non-pathogenic levels. Accidental needlestick injuries are the greatest hazard in the endoscopy suite; needles should not be resheathed and biopsy forceps must be handled with great care. The wearing of gloves should become second nature.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Regulation of mucus secretion by cells isolated from the rat gastric mucosa.

1. A suspension of cells, containing about 30% mucous cells, was isolated from the rat fundic mucosa, and was pre-incubated with D-[6-3H]glucosamine. 3H-labelled material subsequently released into the medium was separated by Fast Protein Liquid Chromatography on a Superose 6 column. 2. A sharp peak of labelled high molecular weight material eluted from the column close to the void volume. This material was identified as mucous glycoprotein by its similar chromatographic behaviour to partially purified rat gastric mucous glycoprotein, by its resistance to complete degradation by papain and by its behaviour on treatment with dithiothreitol. On a caesium chloride density gradient the labelled material was virtually all located between densities of 1.35 and 1.53 g/ml. with the main peak at 1.40 g/ml. 3. A broad peak of lower molecular weight material was also eluted from the column. The release of this unidentified material did not seem to be closely associated with the release of mucous glycoprotein from the cells. 4. Release of mucous glycoprotein was stimulated by secretin (half-maximally effective concentration 2.3 nM, 84% stimulation above basal release at 100 nM), and by isoprenaline (half-maximally effective concentration 34 nM, 33% stimulation at 1 microM). Carbachol (0.5 nM) produced a significant (18-29%) stimulation of mucus secretion, but gastrin (100 nM), histamine (0.5 mM) and epidermal growth factor (200 nM) were without effect. 5. The preparation should prove useful in the identification of the agents which regulate gastric mucus secretion.

Animals↗
PubMed1990

Elimination of high titre HIV from fibreoptic endoscopes.

Concern about contamination of fibreoptic endoscopes with human immunodeficiency virus (HIV) has generated a variety of disruptive and possibly unnecessary infection control practices in endoscopy units. Current recommendations on the cleaning and disinfection of endoscopes have been formulated without applied experimental evidence of the effective removal of HIV from endoscopes. To study the kinetics of elimination of HIV from endoscope surfaces, we artificially contaminated the suction-biopsy channels of five Olympus GIF XQ20 endoscopes with high titre HIV in serum. The air and water channels of two instruments were similarly contaminated. Contamination was measured by irrigating channels with viral culture medium and collecting 3 ml at the distal end for antigen immunoassay. Endoscopes were then cleaned manually in neutral detergent according to the manufacturer's recommendations and disinfected in 2% alkaline glutaraldehyde (Cidex, Surgikos) for two, four, and ten minutes. Contamination with HIV antigens was measured before and after cleaning and after each period of disinfection. Initial contamination comprised 4.8 x 10(4) to 3.5 x 10(6) pg HIV antigen/ml. Cleaning in detergent achieved a reduction to 165 pg/ml (99.93%) on one endoscope and to undetectable levels (100%) on four. After two minutes in alkaline glutaraldehyde all samples were negative and remained negative after the longer disinfection times. Air and water channels, where contaminated, were tested after 10 minutes' disinfection and were negative. These findings underline the importance of cleaning in removing HIV from endoscope and indicate that the use of dedicated equipment and long disinfection times are unnecessary.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Contamination of endoscopes used in AIDS patients.

Contamination of twenty endoscopes used in patients with AIDS was assessed. The suction-biopsy, air, and water channels and the insertion tube were sampled after use, after washing in detergent, and after disinfection for 2 min in 2% alkaline glutaraldehyde. The polymerase chain reaction with Southern blotting, cell cultures, and antigen immunoassay were used to detect human immunodeficiency virus (HIV). Samples were also examined for cytomegalovirus, adenoviruses, enteroviruses, herpes simplex virus, myxoviruses, hepatitis B surface antigen, fungi, and bacteria. Seven of twenty unwashed endoscopes were contaminated by HIV. Commensal bacteria were found in all endoscopes, Candida albicans in six, Staphylococcus aureus in five, and Pseudomonas aeruginosa in five. Washing alone removed all detectable organisms from 66 of 68 contaminated sites; Neisseria spp were recovered from two air channels after washing but not after disinfection. Washing achieved a mean reduction of 4.93 (95% confidence interval 3.69-6.17) colony forming units per ml.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Chemical inactivation of HIV on surfaces.

To assess whether alcohol and glutaraldehyde are effective disinfectants against dried HIV the virucidal effects of 70% alcohol (ethanol and industrial methylated spirit) and 1% and 2% alkaline glutaraldehyde were tested against cell associated and cell free HIV dried on to a surface. Virus stock (100 microliters) or 10,000 cultured C8166 T lymphocytes infected with HIV were dried onto sterile coverslips and immersed in 2% and 1% alkaline glutaraldehyde and 70% ethanol for 30 seconds and one, two, four, and 10 minutes, there being an additional time point of 20 minutes for cell free virus disinfected with 70% industrial methylated spirit. In addition, virus stock in neat serum was tested with 1% and 2% alkaline glutaraldehyde to see whether the fixative properties of glutaraldehyde impair its virucidal properties. Virus activity after disinfection was tested by incubating the coverslips (cell associated virus) or the coverslips and sonicated cell free virus with C8166 T lymphocytes. The lymphocytes were examined for the formation of syncytia and HIV antigens were assayed in the culture fluid. Both 2% and 1% alkaline glutaraldehyde inactivated cell free HIV within one minute; 2% alkaline glutaraldehyde also inactivated cell free virus in serum within two minutes, but a 1% solution was ineffective after 15 minutes' immersion. Cell associated HIV was inactivated by 2% alkaline glutaraldehyde within two minutes. Seventy per cent industrial methylated spirit failed to inactivate cell free and cell associated HIV within 20 and 15 minutes, respectively, and 70% ethanol did not inactivate cell free virus within 10 minutes. Seventy per cent industrial methylated spirit and ethanol are not suitable for surface disinfection of HIV. Fresh 2% solutions of alkaline glutaraldehyde are effective, but care should be taken that they are not too dilute or have not become stale when used for disinfecting HIV associated with organic matter.

Acquired Immunodeficiency Syndrome↗