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Biomedical subjects

G N Cooper

Publications and source records attributed to G N Cooper.

At least 19 recordsLinked to original sources
PubMed1994

Role of bile in non-specific defence mechanisms of the gut.

The effect of depriving the intestine of bile for 48 hours was studied to determine any influence on various parameters of innate immunity in the gastrointestinal tract. Groups of rats were prepared by bile duct cannulation (with or without fluid replacement) or bile duct ligation. Normal and sham operated animals were used for comparing the thickness of the mucus layer and the cells contained therein, enumeration of goblet cells, and measurement of villus size. Histological examination indicated that the intestinal tissues of treated and control rats were similar. Though villus size and numbers of goblet cells were unaffected, a significant reduction occurred in the thickness of the mucus blanket in the duodenal regions of rats deprived of bile, and there were significantly lower numbers of mucus associated enterocytes and lymphocytes, suggesting a lower turnover rate of the epithelium. The balance of the bacterial populations in the caecum and intestine was altered by bile deprivation-increased numbers of coliform organisms were found in both regions. The range of factors, including antibodies and other known constituents, present in bile may contribute to the maintenance of tissue integrity and influence the balance in indigenous bacterial populations in the intestine. Disturbance of the host's biliary system and concomitant effects on the microbial flora may weaken the overall processes of defence in the intestine.

Animals↗
PubMed1988

Antigens involved in resistance to mucosal association by Vibrio cholerae.

Resistance to growth of Vibrio cholerae at the mucosa of blind intestinal loops developed in rats after intestinal or parenteral exposure to live organisms or other antigenic materials. Simultaneous serological studies suggested that neither serum vibriocidal activity nor intestinal mucus antibodies are likely to provide a direct test of antibacterial immune status. Challenge of rats 4 weeks after one dose of antigen may reveal a form of immunity that is not related to antibodies in the intestine and possibly is analogous to long-term immunity expressed in man following infection with the organism. This immunity has not been attributed to lipopolysaccharide (LPS) antigen and does not appear to involve flagella-associated antigens; involvement of antigens other than LPS, such as protein antigens of the outer membranes of V. cholerae, has not yet been substantiated. Separation of monomeric sub-units of outer-membrane proteins by hydrophobic interaction high pressure liquid chromatography has revealed significant quantitative differences among preparations derived from the common serotypes of the organism. These differences may be sufficient to explain the better protection observed when homologous serotypes were used for immunisation and challenge in the long-term resistance model.

Animals↗
PubMed1987

Antibody synthesis in the rat liver: an association between antibody-forming cells in the liver and biliary antibodies following intravenous injection of horse erythrocytes.

The transient appearance of IgM in the bile of rats injected intravenously with horse erythrocytes (HRBC) correlated with the occurrence of anti-HRBC IgM-secreting cells in the liver. Both responses were reduced in animals splenectomised at the time of immunisation. When rats were given 2 injections of HRBC spaced by 28 days, IgG, IgA and IgM antibody-forming cells (AFC) were detected in the liver along with IgM and non-IgM anti-HRBC antibody in bile. There was a 10-fold increase in the total numbers of mononuclear cells (MNC) retrievable from the liver at the height of the biliary antibody response, the majority of which were not AFC. These results suggest that antigen entering the spleen stimulates the release of a population of MNC which may localise in the liver and that a minor portion of these produces specific antibody which is secreted into bile.

Animals↗
PubMed1986

Antibacterial immunity to Vibrio cholerae in rats.

Blind loops prepared in the small intestines of fasted, MgSO4-treated rats were shown to provide a simple, consistent and inexpensive means of studying mucosal colonisation by Vibrio cholerae serogroup O1. When c. 2000 cfu were injected, the number of mucosa-associated V. cholerae in each loop increased by c. 5-6 orders of magnitude in 10-14 h, without enterotoxin-induced fluid production. Scanning electronmicroscopy and culture suggested that most surface-associated organisms were present in the adherent surface mucus. V. cholerae strains varied in terms of surface-colonising capacity. Immunisation with V. cholerae given intra-intestinally greatly reduced the rate of increase and final number of mucosa-associated vibrios within the 14-h period after challenge. The method could be used to compare the immunity induced by various immunising regimens. Immunity was sometimes accompanied by intestinal mucus-borne antibody against V. cholerae lipopolysaccharide but was sometimes demonstrated in the absence of such antibody or of mucus-borne antibody to heat-sensitive surface protein.

Animals↗
PubMed1985

Early myocardial revascularization for postinfarction angina: results and long-term follow-up.

Within 30 days of acute myocardial infarction, 108 consecutive patients underwent urgent surgical myocardial revascularization for postinfarction angina between July 1976 and March 1983. There were 84 men and 24 women whose mean age was 59.6 +/- 9.5 years (range 34 to 80). Group I (15 patients, 14%) underwent surgery within 48 hours, Group II (47 patients, 43%) between 3 and 7 days and Group III (46 patients, 43%) within 30 days. Fifty-nine patients (55%) had transmural infarction. The ejection fraction was less than 40% in 21 patients (19%). Left ventricular end-diastolic pressure was 20 mm Hg or greater in 42 patients (39%). The incidence of single, double, triple vessel and 70% or greater left main coronary artery stenosis was 4, 20, 59 and 17%, respectively. There were two deaths (1.8%) within 30 days of operation. The incidence of intraaortic balloon pumping was higher in patients operated on earlier after myocardial infarction (53% of Group I versus 22% of Group III). Statistically, there were no differences in the use of inotropic agents or the occurrence of arrhythmias or postoperative myocardial infarction in the three groups. Late follow-up (mean 35 months, range 18 to 98) is complete for all patients (100%). There were four late myocardial infarctions and eight deaths. Actuarial survival was 87% at 5 years. Seventy-three percent of the 108 patients were free of angina and the condition of 14% improved. These results indicate that myocardial revascularization in the first 30 days after myocardial infarction can be accomplished with morbidity and mortality rates similar to those of an elective operation for chronic angina refractory to medical management.

Adult↗
PubMed1984

Initial clinical experience with a low pressure drop membrane oxygenator for cardiopulmonary bypass in adult patients.

The new Travenol oxygenator is composed of 80 parallel blood pathways. Microporous membrane separates the blood and gas compartments. The membrane surface area is 3 m2, with a pore size of 0.01 microns. Venous blood drains directly from the patient through the oxygenator, then through an integral heat exchanger and into a reservoir, from which a single arterial pump returns the blood to the patient. The advantage of this configuration of membrane oxygenator is simplicity of setup and operation. A disadvantage that we have observed is an apparent variation in resistance to blood flow through the oxygenator during clinical perfusion. Construction changes in a later version of the oxygenator have reduced the resistance to flow through the blood pathway. This device has been used for 20 perfusions at moderate hypothermia (mean 31.8 degrees C) in patients up to 2.1 m2 body surface area for up to 313 minutes. Blood flow was 2.1 to 5.6 liters/min, partial arterial oxygen pressure 100 to 394 torr, partial arterial carbon dioxide pressure 19 to 57 torr (mean 37 torr) and, arterial pH 7.29 to 7.56 (mean 7.41). Oxygen transfer was as high as 230 ml/min. This integral oxygenator-heat exchanger-reservoir is operated like a bubble oxygenator, with direct venous drainage through the device and a single pump, but it uses a membrane oxygenator for gas exchange to eliminate the detrimental effects of bubbles.

Adult↗
PubMed1984

Intestinal antibodies in rats following exposure to live Vibrio cholerae.

Indirect enzyme-linked immunosorbent assay methods were used to characterize the primary, secondary and tertiary antibody responses of rats to the lipopolysaccharide (LPS) and heat-sensitive surface-associated (HSSA) antigens of V. cholerae in the major immunoglobulin classes of serum, intestinal mucus and bile following intestinal injections of live organisms. Antibody production following the first injection was limited to the IgG and IgM classes of serum and the IgA class of bile but a second dose given 14 days later induced significant responses in all Ig classes of the three materials. Two contacts with the organism established effective, possibly long term, memory; large increases in serum IgG and intestinal mucus IgG and IgA anti-LPS antibody concentrations occurred when the organism was given 6 weeks later, but anti-HSSA production following the third injection was not significantly greater than during the secondary response. The results also suggest that while anti-LPS antibodies of all three Ig classes are formed in the intestinal lymphoid tissues, local anti-HSSA antibody is restricted to the IgA and IgG classes. Excretion of antibodies in bile does not directly correlate with responses in local and peripheral lymphoid tissues. It is suggested that the hepato-biliary system may be as important to antibody-mediated immunity in the intestine as are the active and passive transepithelial mechanisms of antibody secretion.

Animals↗
PubMed1984

Early and late results following repair of partial atrioventricular (AV) canal.

Since 1961, 35 patients have undergone correction of partial AV canal. The mean age was 9.8 years (2 to 56 years). At cardiac catheterization, the ratio of pulmonary to systemic blood flow was greater than 2.5: 1 in 26 patients (74%) while pulmonary artery pressure was greater than 30 mmHg in 18 patients (51%). Mitral regurgitation was mild in 14 patients, moderate in 8 and severe in 3. The defect was closed with a patch in all patients. Mitral valvuloplasty was performed in 23 patients (68%) and no patient required valve replacement. There were no hospital or late deaths. Postoperatively, 22 patients were asymptomatic (NYHA I) while 13 were class II. There was no progression of mitral regurgitation in 8 years mean follow-up.

Adolescent↗
PubMed1983

Enzyme-linked immunoassays for antibodies against Vibrio cholerae.

Glutaraldehyde-treated V. cholerae organisms bind firmly to the surfaces of plastic microELISA plates, thus providing a stable immobilized antigen for use in enzyme-linked immunosorbent assays (ELISA). Serum absorption and ELISA-inhibition experiments indicate that, in addition to detecting natural antibodies in normal rat serum, the immobilized antigen may be used to quantitate specific anti-V. cholerae antibodies induced in rats by injection of live organisms. Apart from serotypically specific anti-lipopolysaccharide (LPS) antibodies, the reaction with immobilized organisms seems to involve antibodies common to Inaba and Ogawa serotypes; it is suggested that these antibodies are primarily directed against antigens of the outer membrane protein complex of V. cholerae cells. These findings have led to the development of an indirect ELISA method which quantitates levels of antibodies that react with heat-sensitive surface antigens of V. cholerae without involvement of anti-LPS antibodies. When used in conjunction with the indirect LPS-ELISA, the test has been found to provide a more detailed description of the serum antibody responses of rats to parenteral injections of live V. cholerae than has been reported previously.

Animals↗
PubMed1982

Percutaneous vs surgical placement of intra-aortic balloon assist.

Fifty-three patients required IABP over a one-year period. The type of insertion (percutaneous vs surgical) was used randomly. The hemodynamic effect, complication rate, and inability to insert the balloon were similar in both groups. Besides less trauma and cost-effectiveness, the most important advantage of percutaneous over surgical balloon insertion is shorter time interval between decision and insertion which thus allows faster stabilization of ischemic heart patients.

Adult↗
PubMed1981

The role of serum and biliary antibodies and cell-mediated immunity in the clearance of S-typhimurium from chickens.

The development of three parameters of immunity in response to a non-lethal infection of Salmonella typhimurium in adult chickens has been examined. Intravenous inoculation of 1 X 10(6) organisms established infection in the liver, spleen and intestinal tract of all birds; the organism persisted in these sites until day 9 of the infection, after which it was cleared rapidly from all sites. High levels of agglutinating and haemagglutinating antibodies were found in serum and bile 5 days after infection; they peaked at days 7 to 10, and detectable antibody was still present in both fluids 6 weeks after infection. The presence of this antibody did not appear to cause a significant reduction in organism numbers in any of the sites examined. Cell mediated immunity was detected at day 14. It is suggested that cells mediated immunity is responsible for clearance of the organisms from the tissues.

Animals↗
PubMed1981

Immune responses of rats to live Vibrio cholerae: antibodies in serum and intestinal secretions.

Following injection of live Vibrio cholerae into the small intestine of rats, antibodies appear in the serum and mucus secretions associated with the intestinal surfaces. In contrast to oral immunization, single pulses given by this route cause primary and secondary agglutinating and vibriocidal antibody responses; they are slower to develop but similar to those induced by intravenous injection of 10-fold lower doses of the organisms. However, the intestinal route of injection appears to favour local formation of agglutinating antibodies that are directly transferred to the mucus secretions; it is likely that these are of the sIgA class. Evidence has also been presented which suggests that intestinal injection causes formation of antibodies which inhibit agglutination of V. cholerae by type-specific antiserum; these inhibitory effects are eliminated if the reaction is carried out in the presence of diluted normal rabbit serum rather than saline.

Animals↗
PubMed1981

Immune responses of rats to live Vibrio cholerae: secretion of antibodies in bile.

Agglutinating and vibriocidal antibodies appear in the bile of rats within a few days of intravenous or intraintestinal injection of live Vibrio cholerae. Whereas the presence of IgM and IgG antibodies area accounted for by passive exudation from serum., those of the IgA class are selectively (actively) transferred from serum to bile. Bile duct ligation causes a 10-fold increase in serum IgA levels over a 48-h period; a similar increase in agglutinating antibody titre occurs only in rats injected intraintestinally, thus providing further evidence for the predominance of IgA-antibody formation when antigen is taken up from the intestinal lumen. Biliary antibodies do not appear to augment the antibody levels in mucus secretions that adhere to the small intestine surfaces. However, when the bile flow is interrupted by bile duct occlusion or cannulation, the antibody levels in these secretions increase in parenterally-immunized animals. It is unlikely, therefore, that bile duct ligation will provide a satisfactory approach to determining the protective function of biliary V. cholerae antibody.

Animals↗
PubMed1978

Antibodies in the intestinal secretions of rats. Primary and secondary responses to polymeric flagellin.

The antibody responses in serum and secretions obtained from the mucosal surfaces of the small intestine of rats immunized by a parenteral and intestinal route have been compared. Though no significant differences in the mean serum titres were found, the responses of animals immunized via the latter route to large doses of antigen were far less uniform. Apart from the first few days of the primary response, antibody activity was found in three major immunoglobulin classes (IgG2, IgA and IgM), irrespective of the route of immunization. Significant antibody activity appeared in the intestinal surface secretions only after two injections of antigen. In rats immunized parenterally the activity was found only in the IgG2 component. Whilst activity was found in both IgG2 and IgA fractions of the secretions obtained from intestinally immunized rats, it was predominantly of the IgG2 class. The possible significance of this observation is discussed.

Animals↗