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Biomedical subjects

H Krakauer

Publications and source records attributed to H Krakauer.

At least 109 records · Page 6Linked to original sources
PubMed1983

Light-scattering studies of the alpha-ketoglutarate dehydrogenase complex from escherichia coli. I. Characterization of the self-association of the complex.

The self-association of Escherichia coli alpha-ketoglutarate dehydrogenase complex (KGDC) purified by a column Chromatographic technique, was characterized by light-scattering photometry. The complex adopts a solution conformation somewhat larger than that observed in the electron microscope. The evidence suggests a nonideal indefinite self-association model for KGDC in KCl, phosphate buffer. The KGDC monomer has a molecular charge of about -3 x 10(2) at neutral pH. The self-association is promoted by increasing KCl concentrations, pH (in the range from 6.3 to 7.4) and temperature (from 20 to 30 degrees C). The effects of pH changes suggest a release of protons during the self-association and a minor 'preferential' interaction of phosphate ions. For the association of one monomer to the aggregate at neutral pH and 25 degrees C. DeltaG degrees = -7.8 kcal mol(-1). DeltaH degrees = 24 kcal mol(-1) and DeltaS degrees = 1.1 x 10(2) cal mol(-1) K(-1). These data indicate that hydrophobic interactions drive the association. Thermodynamically, the self-association of KGDC is a complex phenomenon and may serve to stabilize the enzyme complex in solution.

Journal Article↗
PubMed1983

Assessment of prognostic factors and projection of outcomes in renal transplantation.

Analysis of data on renal transplantation collected in two large multicenter observational studies resulted in the concordant identification of five factors that correlated highly and at a substantial level of statistical significance with the outcome of unrelated cadaveric donor transplantation (i.e., they were associated with differences in one-year graft survivals of 0.07-0.21 and P values less than 0.05). These factors were: blood transfusions prior to the transplant, race of the recipient (white or black), prior failure in transplantation, level of sensitization to lymphocyte alloantigens, and diabetes as the cause of end-stage renal failure. Multivariate analysis with a mathematical survival model confirmed the importance and independence of these prognostic factors. Matching of HLA antigens appeared to be beneficial in both studies, but failed to attain high statistical significance in one. Systematic differences in the use of pretransplant splenectomy and, probably, in the nature of the antilymphocyte serum or globulin led to discordance in assessment of the importance of these factors in the two studies. Although advanced age (greater than 45 years) of the recipient was associated with reduced graft survival in both studies, analysis by means of the model failed to detect a significant correlation between the recipient's age and the outcome in one of the studies because the relation was not monotonic. In an illustration of their utility in the detailed assessment of performance, the prognostic factors were found to substantially account for the markedly superior results at one center and partly for lower graft survivals at another. These prognostic factors may be used to predict probable outcomes for populations and for individual patients subjected to particular arrays of conditioning strategies.

Analysis of Variance↗
PubMed1982

Monoclonal antibodies specific for human polymorphic cell surface antigens. I. Evaluation of methodologies. Report on a workshop.

Five techniques, the direct and the antiglobulin enhanced cytotoxicity assays, indirect immunofluorescence, the enzyme-linked immunosorbent assay, and the radioimmunoassay, were evaluated in a workshop to determine their utility in studies of the interactions of monoclonal antibodies with HLA antigens expressed on lymphocytes. Several well-defined antibodies, both cytotoxic and noncytotoxic, were tested against well-characterized human lymphoid cells. All the methods suffer from some deficiency. The enhanced cytotoxicity assay, however, is most useful as a routine screening tool because of its ease and simplicity; whereas, the enzyme-linked immunosorbent assay is most useful when dissection of antigenic structure is sought because it yields information on the quantities of the antigenic determinants expressed on the cell surface without requiring radioactive reagents.

Antibodies, Monoclonal↗
PubMed1981

Central banking of hybridomas.

The National Institute of Allergy and Infectious Diseases is developing, with the American Type Culture Collection, a central facility for the acquisition, maintenance, and distribution of hybridoma cell lines. This effort finds its principal justification in the great activity in this field and in the large variety of hybridoma lines that are produced because of the intrinsic immense diversity of antibodies the immune system is capable of generating. Thus there clearly needs to exist a mechanism both to facilitate exchange of these cell lines and to assure the preservation of the ones of greatest interest. The burgeoning involvement of commercial interests in the production and marketing of monoclonal antibodies complicates, but in no way vitiates the institute's efforts.

Animals↗
PubMed1981

Changes in lectin receptor lateral mobilities accompany lymphocyte stimulation.

Changes in lateral mobilities of rabbit lymphocyte membrane components in response to succinyl concanavalin A (S Con A) have been studied by fluorescence photobleaching recovery (FPR). During hrs 0 to 3 after exposure to S Con A, lectin receptor mobilities on both T and B cells fall about 2-fold. Reduced mobility of T cell lectin receptors persists until hr 18. From hr 18 to 24 rapid recovery of original mobility occurs if and only if lectin is present. In contrast, nonresponding B cells recover original receptor mobility gradually over hr 4 to 48. Metabolic inhibitors added at hr 3 restore original receptor mobilities, but cytoskeletal disruptors have this effect on T cells only. From hr 0 to 15, washing lectin from the cell surface is decreasingly effective in restoring T cell receptor mobility. After hr 15, mobility cannot be enhance by lectin removal. Parallel DNA synthesis studies show that, for T cell stimulation, lectin must be present on the cell surface during hr 0 to 3 and 18 to 24. These are the periods when FPR measurements show lectin receptor mobilities being restricted and released, respectively. Stimulation of B cells by anti-Ig shows several interesting features. First, stimulation by intact anti-Ig fails to reduce the mobilities of Con A receptors in a manner similar to that produced by S Con A. Second, S Con A does reduce mobility of surface Ig. Thus, Con A receptors would appear to exert a unique anchorage modulation of mobilities of other membrane molecules.

Animals↗
PubMed1977

Thermodynamics of antibody-antigen reactions. 1. The binding of simple haptens to two classes of antibodies fractionated according to affinity.

The thermodynamic parameters which characterize the binding of dinitrophenylglycine and dinitrophenylmethoxypoly(ethylene glycol) to selected affinity classes of equine IgG and IgG(T) antibodies were determined by fluorescence quenching and flow calorimetry. The binding enthalpies and entropies were in all cases large and negative, falling in the ranges -14 to -17 kcal/mol and -18 to -25 eu, respectively. The differences in the enthalpies and entropies of binding for different affinity classes and for different haptens are discussed with reference to differences in the structures of the haptens studied and as indications of differences in binding site structure. In addition, the apparent existence of fluorescent side chains which can transfer energy to either hapten binding site in IgG(T) antibodies but not in IgG antibodies is interpreted as indicative of a smaller average interbinding site distance in IgG(T) than in IgG antibodies.

Animals↗
PubMed1977

Thermodynamics of antibody-antigen reactions. 2. The binding of bivalent synthetic random coil antigens to antibodies having different antigen precipitating properties.

The objects of this study were the equine IgG and IgG(T) classes of antibodies with immunologic specificity for the dinitrophenyl group and bivalent antigens consisting of linear poly(ethylene glycol) polymers which terminated at both ends in dinitrophenyl groups. Complex formation between antibodies of both classes and one of several sharp fractions of antigen having number average molecular weights in the range 25 000 to 75 000 were studied by measuring the light scattered from solutions containing equimolar amounts (approximately 5 x 10(-6) mol/L) of one of the antibodies and one size fraction of antigen, and variable amounts of monovalent hapten. The data were analyzed in the context of a model that accounted for the formation of linear and cyclic complexes of all extents of aggregation. Two parameters in addition to the intrinsic antibody-dinitrophenyl group association constant were found to be necessary in the assumed equilibrium model to account for the behavior of the system. One of these accounted for the looses in configuration entropy that resulted when a random-coil polymer became bound at one end to a space-occupying antibody. The other was a ring closure factor for the formation of cyclic complexes. Ring closure factors for the formation of larger cyclic complexes (present in only small amounts under the conditions studied) were related to the ring closure factor for the formation of the smallest, which was found to increase as antigen size decreased, and for each antigen size to be consistently higher for IgG(T) antibody than for IgG antibody. Comparison of the theoretically estimated values of the two parameters within their measured values indicated that the average conformation of IgG antibodies in solution is open ("T" shaped) but the average inter-Fab are angle in IgG(T) antibodies is approximately 60 degrees or less.

Animals↗