PubMed Health⌕ Search

Biomedical subjects

W Bock

Publications and source records attributed to W Bock.

At least 19 recordsLinked to original sources
PubMed1995

Comparison of high dose therapy of rhEPO, given two or three times a week in premature infants.

We investigated the question whether there is a difference in the response to high dose human recombinant erythropoietin (rhEPO) given twice or three times weekly in premature infants. 48 premature infants were randomly assigned to receive 300 U/kg rhEPO three times a week or 450 U/kg two times a week for at least 4 weeks and up to 6 weeks. Concomitant oral iron supplementation was compulsory, median daily dosage reached 6.6 mg/kg, doses exceeding 8 mg/kg/d were not tolerated. Our data showed no differences in the two groups in regard to hematocrit (HCT), reticulocytes and ferritin levels. A marked increase in reticulocyte counts could be observed in both groups. Serum ferritin decreased as expected. Premature infants starting with a baseline HCT lower than 32% showed a steady increase in HCT without any initial decline. No adverse effects could be observed in either group. Since there is no difference in the response to high dose rhEPO given two or three times weekly, we therefore conclude that the twice weekly regimen is compatible with outpatient treatment.

Anemia↗
PubMed1992

(Aminoalkoxy)chromones. Selective sigma receptor ligands.

A series of (aminoalkoxy)chromones has been prepared, members of which bind potently (16-100 nM) at the sigma binding site and bind weakly (greater than 1000 nM) at the dopamine D2 receptor and 33 other receptors, second messenger systems, and ion channels. At the sigma receptor, the preferred position of attachment for the aminoalkoxy side chain to the chromone ring followed the rank order: 7-position greater than 5-position greater than 6-position. Chromones that contained a 2-substituent that was not coplanar with the chromone ring system showed improved binding over compounds with coplanar substituents. The most potent compound at the sigma site, 7-[[7-(4-hydroxypiperidyl)heptyl]oxy]-2-phenylchromone (74), had receptor affinities (IC50) of 16 nM at the [3H]DTG site, 19 nM at the [3H]-(+)-3-PPP site, and 4000 nM (Ki) at the dopamine D2 receptor. The most selective compound examined, 6-[[6-(4-hydroxypiperidyl)hexyl]-oxy]-2-cyclopentylchromone (58), exhibited IC50s of 51 nM at the [3H]DTG site, 55 nM at the [3H]-(+)-3-PPP site, and 21,000 nM (Ki) at the dopamine D2 receptor. Compound 44 (6-[[6-(4-hydroxypiperidyl)hexyl]oxy]-3-methylflavone, NPC 16377) was systemically effective (ip and po) in two behavioral models predictive of antipsychotic compounds and systemically active in animal models of ischemia.

Chromones↗
PubMed1989

Brain stem auditory evoked potentials (BAEP) monitoring in brain death.

In our intensive care unit, brain stem auditory evoked potentials (BAEP) are measured continuously in comatose patients. For this study we examined 15 patients who fulfilled the criteria of brain death (2). Loss of BAEP in these patients inevitably means loss of brain stem function and consecutive death. Our investigation shows that continuous BAEP monitoring can be helpful for the assessment of brain death and for the earlier decision of organ explantation.

Aged↗
PubMed1988

Effects of cerebellar retraction on brainstem auditory evoked potentials in an experimental animal model of cerebellopontine angle tumor.

The effects of cerebellar retraction on brainstem auditory evoked potentials (BAEPs) were studied in 15 New Zealand rabbits. In the first series, a Fogarty catheter was placed in the cerebellopontine angle of 5 rabbits. When a balloon volume of 0.2 mL was produced, only the latencies of waves III-V of the ipsilateral side increased. With a volume of 0.4 mL the ipsilateral BAEPs were irreversibly lost and the contralateral one reversibly changed. A volume of 0.6 mL caused loss of the BAEP on both sides and death of the animal. In another series, the cerebellum of 10 rabbits was retracted by a self-retaining retractor laterally to medially, so an approach to the cerebellopontine angle was simulated. With a retraction of up to 36 power units (p) the ipsilateral BAEPs were reversibly changed. A retraction of 54 p caused irreversible loss of wave V on both sides. With 84 p ipsilateral and contralateral waves III-V were immediately lost. The animals died within 7 minutes. Our experimental investigation shows that not only a defined volume in the cerebellopontine angle can cause irreversible impairment of brainstem function, but also uncontrolled retraction of the cerebellum.

Animals↗
PubMed1986

[Binding of lead and copper ions to ethanol-insoluble substances from cooking potatoes].

The binding of Pb2+- and Cu2+-ions to ethanol-insoluble substances from three sorts of raw or cooked table potatoes in aqueous suspension is investigated. Moreover, analogous tests on the binding of Pb2+-ions to glucose-6- and glucose-1-phosphate as well as to phosphoric acid are performed. The determination of the free cations in the equilibrium solutions is directly carried out by means of ion-specific electrodes in consideration of the pH-influence. In view of nutrition physiology raw and cooked potatoes are capable, as well as vegetables, of binding Pb2+ and Cu2+ ions, due to their content of pectins with an esterification degree found to be in the range of 50-56% and 42-48%, respectively. The binding capacity of the ethanol-insoluble substances does not only base on their content of pectin-carboxyl groups but also on other macromolecular components. Among the metabolic degradation products of potato starch only free phosphoric acid is capable of binding Pb2+ ions.

Copper↗
PubMed1986

Human monocyte modulation of endothelial cells and fibroblast growth: possible mechanism for fibrosis.

Several human diseases are characterized by vascular pathology, fibroblast activation, and excessive fibrosis (e.g., scleroderma, chronic graft versus host disease, pulmonary fibrosis). An intense inflammatory exudate of mononuclear cells which are derived from the peripheral blood precedes the vascular and fibrotic changes. We examined, in vitro, the effects of human peripheral blood mononuclear cell culture supernatants (PBM-SN) on the growth and survival of human endothelial cells (EC) and of human dermal fibroblasts (FB). The same PBM-SN consistently induced inhibition of EC and stimulation of FB proliferation. PBM-SN derived from 42 patients with scleroderma induced 32 +/- 5% (mean +/- SE) more inhibition of EC and 42 +/- 18% more stimulation of FB compared with PBM-SN derived from 30 healthy subjects. Depletion of phagocytic cells or adherent cells from PBM resulted in SN with no demonstrable activity on either EC or FB. Partial purification of PBM-SN on ion exchange and gel filtration chromatography revealed the presence of two fractions that stimulated and one fraction that inhibited FB proliferation, and two fractions that inhibited and one that stimulated EC proliferation. These data suggest that monocytes are capable of releasing mediators that stimulate or suppress EC or FB. However, when activated by surface adherence, resulting SN inhibit EC and stimulate FB proliferation. Serum is required for the expression of FB proliferation.

Cell Adhesion↗
PubMed1985

[The distribution of free and esterified carboxyl groups within the pectin molecule after the action of pectin esterase from Aspergillus niger and oranges].

By reaction of pectin esterase (PE) from Aspergillus niger and oranges as well as lye, with 95% esterified citrus and apple pectin we prepared series of preparations with degrees of esterification between 35 and 77%. In these partial deesterified pectins the form of distribution of the free and esterified carboxyl groups has been determined from the activity coefficient gamma Ca2+ of the calcium counterions in the solutions of the corresponding calcium pectinates, from the electrostatic free enthalpy delta (Gel/N)KCa of the ion exchange Ca2+----2K+ in these systems as well as from the relative activity of the polygalacturonase reacting with sodium pectinate. The PE from A niger hydrolyzes the esterified carboxyl groups more or less randomly, in a manner similar to the effect of lye on pectin. On the other hand PE from oranges brings about block-like groupings of free carboxyl groups in the pectin molecule. The study revealed different reaction mechanisms of the pectin deesterification by pectin esterases from Aspergillus species and higher plants.

Aspergillus niger↗
PubMed1981

[Characterization of polygalacturonase covalently bonded to Sepharose].

For the soluble endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec., investigated in the present work, the defined substrate turnover U at 50% loss of viscosity if 0.2% and is independent on the reaction temperature. In the case of the covalently-bonded enzyme, the following linear equation applies to U, depending on the specific activity A and in the limits from A = O [U] and Amax: U = [U] + S square root of A. U is influenced by the kind of linkage, the conditions of immobilization and the properties of the carrier: it is a measure of the postulated conformational change of the polygalacturonase. The characteristic limiting value for the substrate turnover at A = O [U] is also temperature-independent and proves to be a true increment of binding, whereas Amax depends essentially on the porosity of the carrier. Polygalacturonase-sepharose complexes with a real substrate turnover U of 3--20% were prepared by varying systematically the kind of linkage and the specific activity A. It was found that with increasing U these complexes were, as a rule, inhibited to a lesser extent by a non-competitive pectinase inhibitor than the soluble polygalacturonase. Furthermore, their ability to liberate or enrich oligomeric galacturonic acids with a degree of polymerization greater than 3 was markedly reduced.

Aspergillus↗
PubMed1980

[Effects of molecular parameters of galacturonan substrate on the activity of a polygalacturonase from tomatoes].

The activity of a major form of the tomato polygalacturonase (EC 3.2.1.15) depends of the origin of the galacturonan substrates (apple, citrus) as well as upon the molecular mass, the degree of esterification and the distribution of the ester methoxyl groups. Optimal substrates are citrus pectic acids with a degree of esterification < 1% and a molecular mass corresponding to a viscosity number [eta] = 90 ml/g galacturonan. In the [eta] range from 16 to 474 ml/g, the Km values decrease to constant amount of 15.6 mM galacturonic acid units, which corresponds to 0.27% galacturonan. In a statistical distribution of the ester methoxyl groups, the activity reaches zero in the range of the degree of esterification from 80 to 90%. Enzymatically de-esterified pectins with a degree of esterification < 32% and a block-like distribution of the ester methoxyl groups behave as comparable pectic acids. In summary, there is a good agreement between these enzymesubstrate interactions and those of endopolygalacturonases from Aspergillus spec. Differentiations manifested themselves only in the transition range between macromolecular galacturonan substrates and oligomeric substrates below the established critical molecular mass.

Glycoside Hydrolases↗
PubMed1978

[Mode of action and inhibition of polygalacturonase covalently bound to polysaccharide and glass carriers].

Endo-polygalacturonase (EC 3.2.1.15.) from Aspergillus spec. is much changed as far as its mode of action and the interaction with vegetable inhibitors of pectinase (from green beans and cucumbers) are concerned when it is covalently bound to insoluble carriers (Sepharose, cellulose powder, macroporous glass and nonporous ballotinis). Whereas a 2% degradation of substrate by the soluble enzyme caused a 50% decrease of viscosity of citrus pectic acid, the comparable degradation of substrate was increased to a level of about 10% with the investigated polygalacturonase carrier complexes apparently independent of the properties of the carriers and the kind of binding of the enzyme. In contrast to this the higher degradation of substrate of 15 and 20% respectively which was further stated at a 50% decrease of viscosity is unambiguously connected with the carriers and is in direct correlation with the specific activity of the polygalacturonase carrier complexes. Contrary to the soluble enzyme the covalently bound enzyme produces more lower oligomerous galacturonic acids by an exo-mechanism or by multiple attack already at the beginning of the hydrolysis of pectic acid. During the final stage there is an enrichment of trigalacturonic acid besides mono- and digalacturonic acids independent of the state of solution of the enzyme. It could further be stated that the strong inhibition of the soluble endo-polygalacturonase by selected pectinase inhibitors which was described earlier is reduced by degrees with the enzyme covalently bound to the insoluble carriers.

Enzymes, Immobilized↗
PubMed1978

[Synthesis and properties of immobilized enzymes. X. Covalent binding of polygalacturonase to insoluble carriers].

The pectinolytic enzymes are of practical interest for the clarification of fruit juice. In the present paper the covalent coupling of polygalacturonase (PG; E. C. 3.2.1.15) is reported. A commercially available enzyme (Rohament P; 5 U/mg) and purified Endo-PG (200 U/mg) are immobilized to the following carriers: BrCN-activated Sepharose, carbodiimide-activated CH-Sepharose, dialdehyde Sepharose, dialdehyde Sephadex, dialdehyde cellulose, CMC-azide, carbodiimide-activated CMC, macroporous glass (isothiocyanate and carbodiimide coupling) and glass beads. The implications of pore diameter (Sephadex- and Sepharose derivatives), of purity of the PG, of protein content of the PG-carrier-complexes as well as the presence of substrate during the coupling reaction, are discused in relation to the relative and specific activity of the bound protein and to the efficiency of the coupling reaction. From the carriers under study derivatives of Sepharose yield the best result (relative activity max. 88%, specific activity max. 5400 U/mg). The immobilization to isothiocyanate glass yields good results, too (relative activity 20%, specific activity 500 U/g). The mechanical instability of the PG-dialdehye Sephadex-complexes and the low relative activity of the bound enzyme are unsatisfactory. Due to their low affinity to PG, the derivatives of cellulose are also inappropriate for covalent coupling of this enzyme. All PG-carrier-complexes are largely stable both during storage at 4 degrees C and repeated activity assays.

Enzymes, Immobilized↗
PubMed1977

[Computer tomography in intracranial hemorrhage (author's transl)].

For the detection of acute intracranial and intracerebral hemorrhage computer tomography C.T.- examination is of greatest importance. The diagnostic value exceeds angiographic findings. Especially in cases of urgency C.T. should be used as routine examination.

Acute Disease↗
PubMed1976

[Retention of apple starch in production of pectin by the aluminum pectinate procedure].

Apple pectin produced by means of the aluminum pectinate procedure contains less starch than apple pectin obtained by precipitation with ethanol. The degradatin of the starch which occurs during production depends to a great extent upon the conditions of pomace digestion. The absorption maxima of the amylose-iodine complexes range in general from 550 to 570 nm. Model experiments with highly esterified pectin and partially degraded (by mechanolysis) apple starches were performed to establish favourable conditions for fractionating the pectin and starch components which are obtained when the pectin is precipitated as aluminum pectinate and when the granular coagulate is washed with water.

Aluminum↗