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K Haupt

Publications and source records attributed to K Haupt.

25 records · Page 2Linked to original sources
PubMed1996

Activation of human platelet protein kinase C-beta 2 in vivo in response to acute hyperglycemia.

Protein kinase C (PKC) is known to be activated in experimental model systems by elevated glucose and may play an important role in the pathogenesis of diabetic complications. Since there is no information about its role in humans in vivo we investigated the activation of PKC in human thrombocytes during infusion of glucose and insulin in normal controls and in 19 NIDDM patients by determining membrane and cytosol levels of PKC beta 2 using immune blots. In the 27 subjects investigated (8 controls, 19 NIDDM) membrane-associated levels of PKC beta 2 increased significantly after 60 and 150 min (p < 0.005). In controls an increase of membrane and of cytosolic PKC beta 2 occurred upon elevation of glucose by 5.5 mmol/L or more and the membrane association persisted for at least 60 min. In NIDDM glucose was elevated by 7.5-10 mmol/L during infusions. Increases of both membrane and cytosolic PKC beta 2 (< 20%-300%) occurred in 10 NIDDM patients suggesting that both, translocation and increased synthesis of PKC beta 2 were stimulated by glucose. Nine other patients showed no alteration (i.e. < 20%) of PKC beta 2. The 2 groups were similar regarding parameters of diabetes control, baseline glucose and glucose elevation during the test. However, the PKC beta 2 responsive group had lower levels of serum triglycerides (1.39 +/- 0.19 vs. 2.32 +/- 0.34 g/L; p = 0.038). To assess whether absolute levels of PKC were altered in human diabetes, platelet levels of PKC alpha, beta 1 and beta 2 were determined in 22 controls and 25 NIDDM subjects with poorly controlled diabetes (HbA1c = 9.8 +/- 0.36%). Cytosolic levels of PKC alpha were significantly decreased by 27% compared to controls in NIDDM but there was no change of PKC beta 1 or PKC beta 2. We conclude that 1. acute elevation of glucose by 5.5 mmol/L or more can activate PKC beta 2 translocation in controls and NIDDM patients in vivo irrespective of parameters of metabolic control. 2. NIDDM patients differ in their PKC beta 2-responses to glucose and 3. poor metabolic control leads to moderate downregulation of PKC alpha suggesting continued activation.

Adult↗
PubMed1996

P300 abnormalities in long-time survivors of acute lymphoblastic leukemia in childhood--side effects of CNS prophylaxis?

The incidence and the degree of P300 abnormalities in relation to psychometric findings was assessed in two groups of long-term survivors of acute lymphoblastic leukemia (ALL) in childhood. The study was performed as part of a follow-up trial, evaluating CNS late-effects after antileukemic therapy, 7.1 +/- 1.6 years after cessation of antileukemic therapy. Subject groups differed primarily in terms of antileukemic CNS prophylaxis: combined radio- and chemotherapy (n = 8) vs. chemotherapy alone (n = 5). Results were compared with those of a third group of healthy controls (n = 13) matched for age and gender. P300 recordings were obtained during a visual oddball-paradigm using checkerboard reversal stimuli of different pattern sizes as target and background events. Neurophysiological data were correlated with the results of a psychological test battery, which measured general intelligence, non-verbal visual memory functioning and concentration. ERP analysis showed a significant prolongation of the P300 latency in irradiated subjects when compared to healthy controls and non-irradiated long-term survivors. Topographical data comparisons revealed substantial P300 differences in both ALL long-term survivor groups when compared with healthy controls. This demonstrated significantly lower amplitudes over the left frontal derivations, associated with lowered concentration abilities, in the irradiated subject group. Higher amplitudes over the parieto-temporal derivations of the right hemisphere, associated with significantly impaired visual memory capabilities, were seen in both long-term survivor groups.

Adolescent↗
PubMed1995

Interaction of human immunoglobulin G with l-histidine immobilized onto poly(ethylene vinyl alcohol) hollow-fiber membranes.

L-Histidine as pseudobiospecific ligand was immobilized onto poly(ethylene vinyl alcohol) hollow-fiber membranes to obtain an affinity support for immunoglobulin G (IgG) purification. The interaction of human IgG with the affinity membranes was studied by chromatography and equilibrium binding analysis. Adsorption was possible over a broad pH range and was found to depend strongly on the nature of the buffer ions rather than on ionic strength. With zwitterionic buffers like morpholinopropanesulfonic acid (Mops) and hydroxyethylpiperazineethanesulfonic acid (Hepes), much higher adsorption capacities were obtained than with other buffers like Tris-HCl and phosphate buffers. An inhibition analysis revealed that non-zwitterionic buffers competitively inhibit IgG binding, whereas Mops and Hepes in their zwitterionic form do not. By choosing the appropriate buffer system, it was possible to adsorb specifically different IgG subsets. The IgG molecules were found to adsorb on membrane immobilized histidine via their Fab part. Determination of dissociation constants at different temperatures allowed calculation of thermodynamic adsorption parameters. Decrease in KD with increasing temperature and a positive entropy value between 20 and 35 degrees C (in Mops buffer) indicated that adsorption is partially governed by hydrophobic forces in that temperature range, whereas at lower temperatures, electrostatic forces are more important for adsorption.

Adsorption↗
PubMed1995

Separation of immunoglobulin G from human serum by pseudobioaffinity chromatography using immobilized L-histidine in hollow fibre membranes.

L-Histidine, intended as a pseudobiospecific ligand, was immobilized on poly(ethylenevinyl alcohol) hollow fibre membranes after their activation with epichlorohydrin or butanediol diglycidyl ether. The affinity membranes obtained allowed the one-step separation of immunoglobulin G (IgG) from untreated human serum. Elution was possible under mild conditions with discontinuous pH or salt gradients. IgM was also adsorbed to a certain extent and partially separated from IgG by pH gradient elution. The bound IgG fractions showed pI values between 8 and 9.5 and contained IgG1 and IgG3. The dissociation constants for IgG on the bisoxirane- and epichlorohydrin-activated membranes coupled with histidine were determined by equilibrium binding analysis to be 2.5 x 10(-5) and 2.0 x 10(-5) M, respectively. The maximum binding capacity of the affinity hollow fibre membranes was 80 and 70 mg of IgG per gram of support, respectively. With a cartridge of surface area 1 m2 (about 19 g of fibres), during a 60-min run, theoretically up to 1.5 g of IgG can be removed from human serum. The histidine affinity membranes are very stable owing to the simple nature of the ligand and the coupling via an ether linkage. Reproducible results were obtained over more than 1 year even with untreated human serum being used regularly.

Adsorption↗
PubMed1995

In vitro removal of human IgG by pseudobiospecific affinity membrane filtration on a large scale. A preliminary report.

We have developed a pseudobiospecific affinity membrane device for selective removal of human IgG from plasma or serum in vitro for clinical apheresis application. The pseudobiospecific affinity ligand L-histidine was immobilized through an ether linkage onto poly(ethylenevinyl alcohol) hollow fiber cartridge. The obtained affinity membranes showed high selectivity for IgG adsorption from untreated human serum. These membranes are able to adsorb IgG1, IgG2, IgG3 if Mops buffer is used, and more selectively IgG1, and IgG3 in Tris-HCl buffer. With respect to the binding capacity, the pseudobiospecific affinity membrane used showed a higher capacity as compared to protein A-membranes described in the literature. Due to the high capacity, specificity and stability of the histidine affinity membranes, in addition to their lower cost, the approach proposed in this paper may offer a useful alternative to protein A based devices in the treatment of immune-related diseases.

Adsorption↗
PubMed1992

Separation of immunoglobulin G by high-performance pseudo-bioaffinity chromatography with immobilized histidine. I. Preliminary report on the influence of the silica support and the coupling mode.

High-performance liquid affinity chromatography with immobilized histidine as a pseudo-biospecific ligand has been used for the fractionation of human immunoglobulin G (IgG). Histidine was immobilized onto silica in two different modes: directly onto silica after epoxy activation or using an intermediate amino derivatization of silica and then coupling histidine using water-soluble carbodiimide. The behaviours and capacities of the obtained affinity supports as well as the influence of pH, silica type, pore diameter and coupling mode have been studied. IgG was effectively separated from human plasma and high maximal binding capacities were obtained.

Chromatography, Affinity↗