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Biomedical subjects

R E Kessler

Publications and source records attributed to R E Kessler.

At least 55 records · Page 3Linked to original sources
PubMed1983

Effects of substitution on polyglycerol phosphate-specific antibody binding to lipoteichoic acids.

The influence of D-alanine and carbohydrate substitution of lipoteichoic acids (LTAs) on the binding of antibody directed to the polyglycerol phosphate (PGP) portion was found to be at least partially dependent upon the mode of presentation of the antigen. There were greater differences in binding of anti-PGP immunoglobulins to substituted and unsubstituted LTAs in solution (micellar presentation) than when the same LTAs were adsorbed to the erythrocyte surface, which suggests that there is greater hindrance of access to the PGP chain, possibly as a result of closer packing, in a vesicle or micelle than when LTA is bound to a membrane surface. Although the difference in binding of anti-PGP immunoglobulins was nearly 20-fold between unsubstituted and highly substituted LTAs, rocket heights by rocket immunoelectrophoresis were only 4-fold different for the most highly substituted LTA and unsubstituted LTA. However, unsubstituted LTA clearly bound more immunoglobulin molecules than was reflected in the rocket height alone, since the resulting immunoprecipitates were much more prominent or intense, both before and after staining, than those of highly substituted LTAs. Differences between lightly and moderately substituted LTAs were less than twofold, indicating that under most circumstances estimates of LTA concentrations in samples where the composition is unknown will be within approximately twofold of the estimate.

Adsorption↗
PubMed1983

Increased carbohydrate substitution of lipoteichoic acid during inhibition of protein synthesis.

Decreases in electrophoretic mobilities of intracellular lipoteichoic acid, intracellular deacylated lipoteichoic acid, and extracellular deacylated lipoteichoic acid were observed during inhibition of protein synthesis in Streptococcus faecium after exposure to chloramphenicol or valine deprivation. Increased carbohydrate content, and thus an increased mass-to-charge ratio, rather than changes in ester alanine content or novel fatty acid substitutions, appeared to account for the decreased electrophoretic mobilities. The increase in carbohydrate content, as judged from mobility measurements, was progressive over time and appeared to occur on biosynthetically new lipoteichoic acid as well as on lipoteichoic acid made before inhibition of protein synthesis.

Chloramphenicol↗
PubMed1983

Identification and partial characterization of a pheromone-induced adhesive surface antigen of Streptococcus faecalis.

A surface protein antigen that is produced only during the induction of aggregation of Streptococcus faecalis was shown to contribute to and perhaps be primarily responsible for aggregation. The antigen is an immunodominant surface component of induced cells. F(ab) fragments of immunoglobulins specific for this antigen prevented aggregation, providing direct evidence that the antigen is an adhesin. Consistent with this proposed association was the coincident timing of appearance of the antigen and the timing of aggregation after induction.

Adhesiveness↗
PubMed1981

Effects of penicillin on group A streptococci: loss of viability appears to precede stimulation of release of lipoteichoic acid.

The rate of killing of a group A streptococcal species by penicillin was compared with the release of lipoteichoic acid (LTA) and its deacylated derivative, dLTA. Although there was no stimulation of release from stationary-phase cells in the presence of penicillin, there was dramatic release of LTA and dLTA from exponential-phase cells after the addition of penicillin. Although decreases in viability were observed within 15 min after addition of penicillin, culture mass and LTA content did not appear to be affected until after 30 min. Stimulation of release of LTA and dLTA appeared to take place after 15 but before 30 min after addition of penicillin. These observations are interpreted to indicate that the stimulation of release of LTA and dLTA in response to penicillin is secondary to the killing event.

Bacteriolysis↗
PubMed1980

Growth characteristics of group A streptococci in a new chemically defined medium.

A new chemically defined medium for the growth of group A streptococci has been formulated. The advantages of this new medium over previously described defined media are: (i) rates of growth (i.e., doubling times) of 20 strains were comparable to the rates of growth in complex media; (ii) each strain grew to a higher culture density in the new defined medium than in complex media; (iii) transfer from complex media with small inocula was possible without any prior adaptation regimen; and (iv) the production of virulence factors (i.e., M protein and hyaluronic acid) and extracellular enzymes during growth in this new medium was comparable to that in complex media.

Bacterial Proteins↗
PubMed1980

Effect of portal venous blood flow diversion on portal pressure.

To anticipate the hepatic vascular response to portacaval anastomosis, we studied portal pressure during diversion of portal blood through a temporary extracorporeal umbilical vein to saphenous vein shunt. The relationship of portal pressure to shunted flow was approximately linear. In five schistosomiasis patients (controls) portal diversion to 1,250 ml/min gave portal pressure-shunted flow curve slopes ranging from 0.13 to 0.57 cm water/100 ml per min (0.31+/-0.18, mean+/-SD). In 17 cirrhotic patients with portal hypertension a continuum of slopes was observed from within mean+/-2 SD of control (type A) to larger slopes (type B) indicating failure of portal pressure regulation. When portal flow was augmented by shunting from saphenous vein to portal vein, cirrhotic patients who had slopes less than mean+/-2 SD of controls during diversion (type A) exhibited a compliant system with small increases in portal pressure, whereas type B patients had significantly greater pressure increases. Selective investigations suggested that changes in portal pressure provoked compensatory changes in hepatic arterial blood flow that tended to maintain portal pressure at a set point. Type B patients demonstrated failure of this mechanism to varying degrees.After end-to-side portacaval shunt, seven type A cirrhotic patients maintained residual intrahepatic venous pressure unchanged from prior portal pressure, whereas six type B patients had a significant decrease. Residual intrahepatic venous pressure was measured after portacaval shunt in 40 cirrhotic patients who were followed for as long as 9 yr (median survival 4.0 yr). The 13 patients who developed chronic encephalopathy had significantly lower pressure (21.1+/-4.4 cm, mean+/-SD) and shorter survival (median 0.6 yr) than the other 27 patients (32.6+/-5.3 cm, 5.0 yr). The preoperative estimation of portal pressure-diverted portal flow curve slope anticipates the hepatic vascular response to portacaval anastomosis and identifies a group of patients in whom loss of portal blood flow results in a low residual intrahepatic venous pressure that is associated with early death and chronic encephalopathy.

Alcoholism↗
PubMed1979

Characterization and localization of the enzymatic deacylation of lipoteichoic acid in group A streptococci.

Protoplasts of a group A streptococcal strain were shown to contain enzymatic activity capable of converting lipoteichoic acid (LTA) to deacylated lipoteichoic acid (dLTA). The enzyme(s) appear to be located mainly in the membrane, although activity was also found in the cytoplasm. Determination of the sites of cleavage within the LTA molecule was approached by comparing the chemical composition of LTA and native dLTA. Native dLTA, as distinguished from chemically deacylated LTA, was isolated from buffer in which live streptococci had been resuspended and incubated. The chemical data suggest that the enzyme(s) was(were) lipolytic in nature; that is, the conversion of LTA to dLTA was the result of cleavage of the ester linkages between the fatty acids and the remainder of the LTA molecule.

Carboxylic Ester Hydrolases↗
PubMed1979

Chemical analysis of changes in membrane composition during growth of Streptococcus pyogenes.

Changes in the structural components of the Streptococcus pyogenes membrane between exponential and early stationary phases of growth are reported. The overall protein composition ranged from 70 to 73% of the dry weight of the membranes, irrespective of the phase of growth from which they were isolated. Amino acid analyses of membranes isolated from streptococci in either the exponential or stationary phase of growth demonstrated that two amino acids, cysteine and tryptophan, were absent. Further analysis of the membrane proteins by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis demonstrated that there were proteins unique to a particular phase of growth as well as differences in the amount of specific proteins from the various growth phases. In addition, membranes isolated from exponential-phase cultures contained a higher percentage of peripheral protein than did stationary-phase membranes. There also appeared to be an increase in the amount of outer surface proteins during this growth phase. The phosphorus content of the membranes increased during the stationary phase of growth, whereas the sugar composition remained constant. The only sugar found under various conditions of growth in any of the strains was glucose. Total fatty acid content and the mole percent composition of various fatty acids did not change in the different phases of growth. However, the mole percent composition of fatty acids in the membranes of various group A streptococci did differ between strains. Therefore, these results provide evidence that the composition of membranes of S. pyogenes does not remain constant throughout the growth phases of the culture.

Adenosine Triphosphatases↗
PubMed1979

Quantitative immunoelectrophoretic analysis of Streptococcus pyogenes membrane.

The antigenic composition and molecular structure of the plasma membrane of Streptococcus pyogenes (group A; M type 6) were studied by crossed immunoelectrophoresis (XIE) and other related quantitative immunoelectrophoretic techniques. After establishment of a reference pattern of 29 immunoprecipitates, the relative differences in amounts of individual antigens contained in membranes isolated from cells that were harvested during the exponential or stationary phase of growth were examined. Relative increases and decreases in amounts of individual antigens were estimated from the areas subtended by immunoprecipitates after XIE of Triton X-100 extracts. The asymmetric distribution of antigens on the inner and outer surfaces of the membrane was established in absorption experiments with intact, stable protoplasts. Of the 29 immunoprecipitates, 8 appeared to contain antigens exposed on the outer surface of the membrane, whereas 11 appeared to contain antigens either located on the inner surface or unexposed. Six antigens appeared to have limited exposure on the outer surface, and four others remain to be assigned. Certain immunoprecipitates were characterized with respect to enzymatic activity or interaction with the lectin concanavalin A. Reduced nicotinamide adenine dinucleotide dehydrogenase (EC 1.6.99.3), adenosine triphosphatase (EC 3.6.1.3), and polynucleotide phosphorylase (EC 2.3.7.8) were demonstrated by zymogram techniques. The latter two activities were present within the same immunoprecipitate, suggesting the occurrence of a multienzyme complex. In addition, the areas under the immunoprecipitates containing the three enzymatic activities were not affected by absorption of antimembrane immunoglobulin with intact protoplasts and thus appeared to be located on the inner surface of the membrane. The results from absorption experiments also suggested that the exposure of outer protoplast surface antigens was greater on protoplasts from exponential-phase cells than on those from stationary-phase cells, even when found in increased amounts in the latter.

Adenosine Triphosphatases↗
PubMed1979

Precursor-product relationship of intracellular and extracellular lipoteichoic acids of Streptococcus faecium.

Exponential biosynthesis and excretion of lipoteichoic acid (LTA) during the exponential phase of growth, and continued synthesis and excretion during valine starvation of Streptococcus faecium (S. faecalis ATCC 9790), were shown. During exponential growth, extracellular LTA (LTAx) accounted for approximately 13% of the total LTA in cultures, whereas during valine starvation, this percentage increased to approximately 60% within 4 h. LTAx was present in a low-molecular-weight, apparently deacylated form, whereas intracellular (LTAi) was present primarily in an apparently high-molecular-weight, acylated and micellar form. Experiments utilizing chases of either fully equilibrated or short pulses of [14C]- or [3H]glycerol were used to demonstrate that LTAx was derived directly from LTAi.

Acetates↗
PubMed1979

Enzymatic deacylation of lipoteichoic acid by protoplasts of Streptococcus faecium (Streptococcus faecalis ATCC 9790).

High-molecular-weight, micellar lipoteichoic acid (LTA) was converted to a lower-molecular-weight, apparently deacylated polymer when the former was incubated in the presence of growing protoplasts of Streptococcus faecium (S. faecalis ATCC 9790), but not when incubated in fresh or spent protoplast medium. The mobility of the low-molecular-weight polymer upon agarose gel electrophoresis was indistinguishable from that of native extracellular lipoteichoic acid LTA(X) from this organism or from chemically deacylated LTA. Native LTA(X) was shown to contain less than one fatty acid equivalent per 18 LTA(X) molecules, in contrast to the 4:1 ratio of fatty acids to polyglycerolphosphate chains in micellar LTA.

Enterococcus faecalis↗
PubMed1976

Indications, clinical value and complications of endoscopic retrograde cholangiopancreatography.

Endoscopy combined with endoscopic retrograde cholangiopancreatography is a unique tool providing a broad, precise yield of diagnostic information about diseases of the upper gastrointestinal tract. In the absence of gross anatomic disease, its diagnostic accuracy should exceed 90 per cent and risk be minuscule. The incidence of complications and, therefore, risk to the patient and proportional to the magnitude and remedial nature of the disease processes found. In the absence of diagnostic procedures for diseases of the biliary tree and pancreas that are riskless, the relationship of endoscopic retrograde cholangiopancreatography risk to diagnostic value and patient salvage emphasizes the value of endoscopy combined with endoscopic retrograde cholangiopancreatography as the diagnostic procedure of choice for patients with suspected disease of the biliary tract or pancreas. The unique value of endoscopic retrograde cholangiopancreatography in providing rapid visualization of diseases of the upper gastrointestinal tract mucosa combined with cholangiography and pancreatography is dramatized in the patient with upper abdominal pain syndrome with or without jaundice. In the face of a rapidly evolving illness and the potential need for early surgical intervention, barium studies are relatively contraindicated and have a poor diagnostic yield. By contrast, endoscopic retrograde cholangiopancreatography combined with endoscopy rapidly rules out, or, in the presence of disease of the upper gastrointestinal tract, permits the immediate use of subsequent diagnostic procedures. An experience with more than 1,000 procedures reveals that endoscopic retrograde cholangiopancreatography is an invaluable tool for the diagnosis and management of disease of the pancreas and biliary tract.

Biliary Tract Diseases↗