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Biomedical subjects

K Hofmann

Publications and source records attributed to K Hofmann.

At least 145 records · Page 8Linked to original sources
PubMed1982

Insulin receptor isolation studies.

The observation that N alpha,B1-biotinylinsulin binds firmly to resins in which succinoylavidin is covalently attached to AH Sepharose 4B and can be retrieved by exposure of the resins to 20 mM biotin provided the basis for the present investigations. Solubilized, partially purified insulin receptor from human placenta binds to affinity resins in which N alpha,B1-biotinylinsulin is noncovalently attached to AH Sepharose 4B-immobilized-succinolylavidin. Exposure of the receptor loaded resin to 20 mM biotin results in liberation of a high molecular weight material containing bound 125I-biotinylinsulin, which precipitates with polyethyleneglycol and cross reacts with human insulin receptor antibodies. The technique is biospecific and appears to be applicable to the purification of insulin receptors on a preparative scale. Crude solubilized insulin receptor from human placenta is contaminated with "insulinase" which is inhibited by N-ethylmaleimide. HPLC provides a tool to assess "insulinase" activity that is more sensitive than the TCA precipitation method.

Chromatography, High Pressure Liquid↗
PubMed1982

[Operative management of spontaneous kidney transplant rupture. Personal experiences and literature review].

Spontaneous rupture of the cadaver kidney is not rare in the early post-transplant period. In the literature the rupture complication rate varies between 0.3% and 8.5%. in our series 4.2% (12 of 285) of transplanted kidneys ruptured spontaneously. All transplant ruptures occurred as an early complication within 6 weeks postoperatively in the clinical setting of oliguria. In 8 of 12 patients we tried to preserve the graft by covering it with dehydrated solvent-dried human dura that is then sutured in place. In these cases surgical repair resulted in diuresis and restoration of normal graft function with long-term survival. This study emphasizes the possibility and necessity of conservation and repair of the ruptured allograft.

Adolescent↗
PubMed1981

Expression of antigenic markers during the development of oligodendrocytes in mouse brain cell cultures.

The expression of myelin basic protein (MBP) and galactocerebroside (GC), two antigenic markers for oligodendrocytes, was checked on 7-, 14-, 21- and 28-day-old dissociated mouse brain cell cultures (BCC) by using the indirect immunofluorescence method with double staining. The number of GC positive cells increased between the 7th and the 14th day of culture before a steady state was reached. In contrast to this, the MBP-positive cells appeared only on the 14th day of culture, and their number increased with the age of the culture. In double staining, the serum produced against isolated oligodendrocytes shows the same picture as the anti-GC serum, while only a part of GC-positive cells showed also the presence of MBP. Our data suggest that the GC appears very early on the membrane of the oligodendrocytes during development while cells exhibiting both GC and MBP probably represent a more differentiated oligodendrocyte population.

Animals↗
PubMed1981

Synthesis of lipids in mouse brain cell cultures during development.

Several metabolic activities in dissociated cultures of newborn mouse brain were compared to the situation in vivo. The developmental activity pattern of cerebroside-sulfotransferase, cyclic nucleotide phosphohydrolase, and beta-hydroxy-beta-methyl glutaryl-coenzyme A-reductase and the synthesis and deposition of sulfatide and cholesterol in culture were estimated. The enzyme activity patterns in vivo and in culture are the same. Since the cultures show very little myelin formation, the parallel increase of enzyme activities necessary for myelination in vivo and in culture suggest the existence of intrinsic factors regulating the biochemical differentiation. In addition, the formation of the products, determined in culture, follows the patterns of the enzyme activities. Dissociated brain cell cultures are therefore a valid model for the study of biochemical parameters related to the synthesis of brain lipids during development.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1981

[Altered bacterial periurethral flora in young girls with chronic, recurrent urinary tract infections? (author's transl)].

Assuming a local weakness in the defence system to be responsible for chronic, recurrent infection of the urinary tract in young girls, we made 86 determinations of the bacterial periurethral flora from 70 female patients aged between five and eleven years. Within three patient groups (urologically healthy, temporarily free from infection, currently suffering an acute attack of chronic, recurrent urinary tract infection), we found gram-negative bacteria in 1/20 of the healthy children, in 1/2 of those temporarily free from infection and in all children suffering an acute attack. Enterococci (the accompanying flora) was found in 1/20, 1/2 of the children respectively. In both cases, the differences were significant (chi 2-Test, p less than 0.01). In comparison to healthy children, the more children, in 1/2 of those temporarily free from infection and in all children suffering an acute attack. Enterococci (the accompanying flora) was found in 1/20, 1/2 of the children respectively. In both cases, the differences were significant (chi 2-Test, p less than 0.01). In comparison to healthy children, the more children, in 1/2 of those temporarily free from infection and in all children suffering an acute attack. Enterococci (the accompanying flora) was found in 1/20, 1/2 of the children respectively. In both cases, the differences were significant (chi 2-Test, p less than 0.01). In comparison to healthy children, the more frequent colonization of children who were not currently infected, but who were prone to infection, was seen particularly as an indication of an intermittent local weakness in the defence system, possibly occurring when a defence mechanism occasionally falls short of a threshold level, thus allowing an infection to set in.

Child↗
PubMed1981

Hormonal properties of avidin-biotinylinsulin and avidin-biotinylcorticotropin complexes.

In connection with the development of affinity columns (based on the avidin-biotin interaction) for retrieval of peptide and protein hormone receptors, the hormonal properties of a number of avidin-biotinylinsulin and avidin-bioinylcorticotropin complexes were examined. Of particular interest was an evaluation of streptavidin as a ligand for the attachment of biotinylated hormones to solid supports and its possible advantage over SpHPP-avidin (S = succinoylated; pHPP = 3-(p-hydroxyphenyl)propionyl). As concerns binding kinetics using rat liver plasma membranes, streptavidin was found superior to avidin since it does not display apparently nonsaturable binding. Scatchard analyses of the binding of 125I-streptavidin, 125I-S-streptavidin and 125I-SpHPP-avidin to rat liver plasma membranes gave KD value of 6.7, 13.2, and 10.6 nM respectively. The binding was saturable and the unlabeled proteins competed with their labeled counterparts for the membrane binding sites. Biotinylinsulin, attached to either streptavidin or SpHPP-avidin was able to compete for 125I-insulin-binding sites on rat liver plasma membranes though somewhat larger concentrations of the complexes than of insulin were required to achieve comparable inhibition. The ID50 values for insulin and the biotinylinsulin complexes were 5 and 80 nM respectively. Biotinylcorticotropin was found to be a more effective activator of particulate rat adrenal adenylate cyclase when complexed with unmodified avidin than with streptavidin, S-streptavidin or SpHPP-avidin.

Adenylyl Cyclases↗
PubMed1980

Hormone-receptor studies with avidin and biotinylinsulin-avidin complexes.

Avidin can be labeled to high specific radioactivity by introducing 3-(p-hydroxyphenyl)-propionyl groups into the molecule (pHPP-avidin). 125I-pHPP-avidin binds avidly to rat liver plasma membranes and is not displaced by unlabeled pHPP-avidin. Nonspecific binding of 125I-pHPP-avidin can be substantially reduced by succinoylation of pHPP-avidin with succinic anhydride (SpHPP-avidin). Spectral changes ensuing when the dye 4-hydroxyazobenzene-2'-carboxylic acid binds to avidin cannot be used to assess the binding characteristics of the modified avidins since the absorption coefficients of the complexes are markedly different; however, the modified molecules bind theoretical amounts of [14C]biotin. Biotinylinsulin and biotinylinsulinSpHPP-avidin complexes compete with 125I-insulin for binding to receptor sites on rat liver plasma membranes. Biotinylinsulin complexes with unmodified avidin display anomalous binding behavior attributable to formation of membrane aggregates. In light of this finding, results obtained using unmodified avidin must be interpreted with caution. Biotinylinsulin125I-SpHPP-avidin binds specifically and saturably to rat liver plasma membranes. The biotinylhormoneSpHPP-avidin technique has potential for labeling peptide hormones and other compounds that cannot be iodinated by conventional procedures.

Amino Acid Sequence↗
PubMed1980

Iminobiotin affinity columns and their application to retrieval of streptavidin.

A method is described for the retrieval of streptavidin from the culture broth of Streptomyces avidinii. The key step in this procedure is the adsorption of streptavidin from culture concentrates to an affinity column in which iminobiotin is attached to AH-Sepharose 4B. This column binds streptavbidin at pH 11 and releases the protein at pH 4. The recovery of streptavidin is practically quantitative. The pH dependence of the iminobiotin-avidin affinity, discovered by Green [Green, N. M. (1966) Biochem. J. 101, 774-779], has thus found practical application. The streptavidin bound 4.07 +/- 0.02 mol of [14C]biotin per mol and was essentially homogeneous as judged by disc and slab gel electrophoresis. Streptavidin was extensively succinoylated without loss of biotin-binding capacity. The observations that 125I-labeled streptavidin and 125I-labeled succinoylstreptavidin are retained by iminobiotin-AH-Sepharose 4B columns at pH 7.5 and are eluted at pH 4.0 provides a convenient purification method for these iodinated proteins. The technique employed for the retrieval of streptavidin is generally applicable to the isolation of iminobiotinylated molecules.

Bacterial Proteins↗
PubMed1980

Abnormal metabolism of 35SO4-sulfatide in jimpy brains expressed in brain organotypic cultures.

Cerebroside-sulfotransferase (CST), creatine-phosphokinase (CPK), and 3-hydroxy-3-methylglutaroyl CoA (HMG CoA) reductase activity, protein, and DNA content were measured in an easy-to-perform organotypic culture system of newborn normal and jimpy brains. The defective sulfatide synthesis which has been shown in vivo in jimpy brains could also be demonstrated in organ cultures of jimpy mice in the form of lowered CST activity in the homogenate as well as reduced 35SO4 incorporation into 35SO4-sulfatide. HMG CoA reductase was reduced to 60% of that found in 16-day-old normal cultures, similar to the findings in vivo. DNA of jimpy cultures was significantly lower than that in normal cultures, suggesting the possibility of an arrest in the differentiation or increased cellular death of presumptive oligodendrocytes, as was found in vivo. Organ cultures of jimpy mouse brain can serve as an appropriate model for further study of the primary defect in this animal mutant.

Animals↗
PubMed1979

Evaluation of smoking-induced effects on sympathetic, hemodynamic and metabolic variables with respect to plasma nicotine and COHb levels.

The effect of smoking cigarettes containing 1.5 mg and 0.08 mg nicotine per cigarette and of sham-smoking was studied in six healthy habitual smokers. Levels of carboxyhemoglobin (COHb) and plasma nicotine were measured simultaneously with hemodynamic variables, such as heart rate and blood pressure, and with the metabolic parameters, plasma DBH, cortisol, blood glucose, lactate and free fatty acids. All variables, with the exception of COHb are dose related to plasma nicotine levels. Blood pressure, heart rate and lactate show simultaneous peaks together with maximal nicotine levels, while DBH and cortisol, blood glucose and free fatty acids show a delayed reaction compared to nicotine concentrations. No effects of COHb, even with levels up to 5.6 +/- 0.5% have been observed on the variables investigated. These results demonstrate, that it is nicotine which induces considerable hemodynamic and metabolic alterations after smoking.

Adult↗