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Biomedical subjects

B Wolf

Publications and source records attributed to B Wolf.

At least 181 records · Page 10Linked to original sources
PubMed1992

[The use of bead cellulose for controlled drug liberation. 5. Kinetics of liberation of bonded drugs from bead cellulose and bead cellulose derivatives].

Examination of in vitro liberation of prazosin hydrochloride and benzocaine from formulations of matrix type with bead cellulose and bead cellulose derivatives shows deviations from first order kinetics owing to competition of several processes: dissociation of ionic bonds or cleavage of covalent bonds between drugs and bead cellulose, pore diffusion, dissolution of the drugs and swelling of cellulose matrix. Suitable combinations of different bonded portions of the drug on bead celluloses let these complexes seem to be successful in the use for controlled and retarded liberation of drugs.

Cellulose↗
PubMed1992

[The use of bead cellulose for controlled drug liberation. 5. Binding of benzocaine as a model drug to dialdehyde-bead cellulose and its in vitro liberation].

In the case of ionic binding of drugs to bead cellulose and its derivatives there was no pronounced retardation obvious. Because of this lack benzocaine as a model drug was covalent bound to dialdehyde bead cellulose by an azomethine bond in analogy with enzyme immobilisation methods. The rate of liberation in phosphate buffer was low and incomplete compared with the dissolution rate of pure benzocaine under the same conditions. A further decrease of liberation rate was obtained by reduction of the azomethine to the amine bond. Retardation of drug liberation strictly speaking was not achieved. The main amount of liberated drug was liberated during the first 20 min, but after 6 h the rate was still under 50% of the drug available. The physical properties of the beads like spherical shape and porosity are not significantly influenced by oxidation of cellulose and by loading with drug.

Benzocaine↗
PubMed1992

Rapid alterations in the plasma membrane structure of macrophages stimulated with bacterial lipopeptides.

Synthetic lipopeptide analogues of the N-terminal region of bacterial lipoprotein are potent activators of macrophages. In a previous study we showed that within minutes after their addition to macrophage cultures, lipopeptides were found attached to the plasma membranes and within different compartments of the cells. Their rapid interaction with the plasma membrane is thought to occur via the insertion of their three fatty acids. We used the freeze-fracture technique to study the influence of lipopeptides on the architecture of plasma membranes. Fifteen to thirty seconds after addition of the lipopeptides, the freeze-fractured plasma membranes show a rapid decrease in the particle density. This effect is not due to a loss of proteins, but is caused by lateral diffusion of single particles, which subsequently aggregate. These alterations are transient, temperature-sensitive and disappear 20 min after stimulation. At 4 degrees C, no change is found in the architecture of the plasma membranes. Using electron energy loss spectroscopy (EELS), lipopeptides can neither be detected on the membrane nor within the cells when incubated at this temperature. Our findings suggest that membrane protein aggregation is involved in the rapid uptake of lipopeptides into macrophages after their interaction with the plasma membranes.

Amino Acid Sequence↗
PubMed1992

Biochemical and immunological characterization of serum biotinidase in profound biotinidase deficiency.

The biochemical and immunological characterization of biotinidase was performed in sera from 100 normal individuals, 68 children with profound biotinidase deficiency (less than 10% of mean normal activity) who were identified symptomatically and by newborn screening, and 63 of their parents. On isoelectric focusing, serum enzyme from normal individuals exhibits extensive microheterogeneity, consisting of at least four major and five minor isoforms at pH 4.15-4.35. Patients with profound biotinidase deficiency can be classified into at least nine distinct biochemical phenotypes, on the basis of (a) the presence or absence of cross-reacting material (CRM) to biotinidase, (b) the number of isoforms, and (c) the distribution frequency of the isoforms. None of the patients with CRM had an abnormal Km of the substrate for the enzyme. All of the parents had normal isoform patterns. The mean activities, CRM concentrations, and specific activities were not significantly different between parents of CRM-positive children and parents of CRM-negative children. There is no relationship between either the age at onset or the severity of symptoms and the isoform patterns or CRM status of the symptomatic children. The isoform patterns of children identified by newborn screening are not different from those of symptomatic children.

Adult↗
PubMed1991

Physical dependence on benzodiazepines: differences within the class.

Concern about physical dependence seems to be the major limiting factor in the long-term treatment with benzodiazepines (BZD). The severity of the withdrawal syndrome is determined by multiple factors, e.g. dose, duration of use, frequency of dose interval, mode of discontinuation, the pharmacologic characteristics of the BZD, personality and previous or concurrent use of cross-dependent drugs and/or alcohol. There is evidence that BZD with a short elimination half-life cause a more severe withdrawal syndrome than those with a long elimination half-life. Besides pharmacokinetic properties, pharmacodynamic factors such as potency may also covary with the liability of a BZD to induce physical dependence. There is an increasing body of literature indicating that quickly eliminated, high potency BZD such as alprazolam and lorazepam may be more likely to cause severe withdrawal reactions than slowly eliminated compounds such as diazepam or less potent derivatives such as oxazepam. Alprazolam seems to play an exceptional role, insofar as relatively soon after its introduction to the market a number of case reports of withdrawal psychoses, seizures and intense rebound anxiety were published. Data reviewed from the literature correspond well with the results of interviews conducted with 31 clinicians across the United States with experience in detoxifying patients dependent on BZD, 84% of these physicians mentioning alprazolam as especially problematic with respect to the intensity and/or duration of the withdrawal syndrome.

Anti-Anxiety Agents↗
PubMed1991

Benzodiazepine dependence: detoxification under standardized conditions.

In an analysis of the withdrawal syndrome of 12 patients dependent on benzodiazepines (BZD), important factors such as underlying psychiatric disease, precipitating life events, complaints leading to BZD use, and also positive and negative psychological and social consequences, duration of intake, dose and type of BZD dependence are discussed. Withdrawal was completed under standardized inpatient conditions reducing the BZD dose to 50% of the previous dose once every 5 days and maintaining control through regular measurements of the BZD urine concentrations. The course of the somatic, psychological and perceptual withdrawal phenomena was documented according to Lader's BZD withdrawal symptom checklist (Lader, M. (1983) J. Clin. Psychiatry 44, 121-127). The reduction scheme proved to be safe and efficient; no major withdrawal syndromes developed. Abstinence phenomena largely disappeared within 10 days of discontinuation.

Adult↗
PubMed1991

Statistical approaches for the detection of heterozygotes for biotinidase deficiency.

We applied and evaluated 3 statistical approaches for the detection of heterozygotes for biotinidase deficiency in a randomly selected population of French adults. The first method, which used a cutoff value to dichotomize the population, lacked sensitivity. The second approach calculated the probability of heterozygosity for a given enzyme activity through the application of Bayes theorem to the normal density functions of the enzyme distributions of the obligate heterozygote and the test populations. A priori values of the means and standard deviations (SDs) of the genotypic distributions were used. This method was sufficiently sensitive for both population screening and genetic counseling, but requires prior knowledge of the frequency of the deficient gene (q). The third approach was similar to the second, however, maximum likelihood estimates of the means and SDs of the genotypic distributions were calculated and used to determine the probability of heterozygosity for a given enzyme activity. This method was as sensitive as the second method and is appropriate for screening populations for which there is little prior information about the gene frequency and the genotypic distributions. This method can also be used to estimate the gene frequency of the disorder within a given ethnic or racial population. Using this method, we estimated the frequency of heterozygotes (2pq) in the French population to be 0.012, which was similar to that estimated from the results of neonatal screening for biotinidase deficiency. These methods can be used to detect heterozygotes and to estimate the gene frequency of other inherited enzyme deficiencies.

Amidohydrolases↗
PubMed1991

Variable expression of albinism within a single kindred.

We studied the albinotic characteristics in 13 members of a white family (age range, 2 to 73 years), which were graded according to severity and were correlated with visual acuity. Clinical, electrophysiologic, and biochemical characteristics of this family do not fit any known category of human albinism. The degree of heterogeneity in expression of albinotic features was unexpected. The correlation between visual acuity and nystagmus was particularly strong. The brown-haired propositus had severe skin involvement, iris transillumination, fundus hypopigmentation, and foveal hypoplasia. He had no manifest nystagmus, however, and his visual acuity was nearly normal. These observations suggest that nystagmus imposes a visual deficit beyond that related to foveal hypoplasia alone.

Adolescent↗
PubMed1991

Identification of an abundant S-thiolated rat liver protein as carbonic anhydrase III; characterization of S-thiolation and dethiolation reactions.

An S-thiolated 30-kDa protein has been purified from rat liver by two steps of ion-exchange chromatography. This monomeric protein has two "reactive" sulfhydryls that can be S-thiolated by glutathione (form a mixed disulfide with glutathione) in intact liver. The protein has been identified as carbonic anhydrase III by sequence analysis of tryptic peptides from the pure protein. The two "reactive" sulfhydryls on this protein can produce three different S-thiolated forms of the protein that can be separated by isoelectric focusing. Using this technique it was possible to study the S-thiolation and dethiolation reactions of the pure protein. The reduced form of this protein was S-thiolated both by thiol-disulfide exchange with glutathione disulfide and by oxyradical-initiated S-thiolation with reduced glutathione. The S-thiolation rate of this 30-kDa protein was somewhat slower than that of glycogen phosphorylase b by both S-thiolation mechanisms. The S-thiolated form of this protein was poorly dethiolated (i.e., reduced) by glutathione, cysteine, cysteamine, or coenzyme A alone. Enzymatic catalysis by two different enzymes (glutaredoxin and thioredoxin-like) greatly enhanced the dethiolation rate. These experiments suggest that carbonic anhydrase III is a major participant in the liver response to oxidative stress, and that the protein may be S-thiolated by two different non-enzymatic mechanisms and dethiolated by enzymatic reactions in intact cells. Thus, the S-thiolation/dethiolation of carbonic anhydrase III resembles glycogen phosphorylase and not creatine kinase.

Amino Acid Sequence↗
PubMed1991

Intracellular localization of a lipopeptide macrophage activator: immunocytochemical investigations and EELS analysis on ultrathin cryosections of bone marrow-derived macrophages.

Synthetic lipopeptides, structurally derived from the N-terminal part of bacterial lipoprotein, constitute macrophage and B-lymphocyte activators. The molecular mechanism of macrophage activation by lipopeptides still remains unclear. The purpose of our study was to determine the route and kinetics of lipopeptide distribution in bone marrow-derived macrophages. The intracellular localization of the C-terminally biotinylated lipodipeptide Pam3Cys-Ser was investigated on ultrathin cryosections using the biotinstreptavidin-gold system. Our findings indicate that the lipopeptide penetrates the plasma membrane and can already be found within the cytoplasm, the nuclear membrane, and within the nucleus after 2 min of stimulation. The pattern of lipopeptide distribution obtained 2 min after stimulation resembles that obtained after longer incubation times (8 and 20 min). Correlating distribution patterns were observed when using the method of electron energy loss spectroscopy (EELS). These findings are a clear indication for the rapid uptake of lipopeptides into eukaryotic cells, and are of importance for further studies of the immunostimulating properties of the bacterial lipopeptides and vaccines derived therefrom.

Animals↗
PubMed1991

Microvascular phenomena during pancreatic islet graft rejection.

Transplantation of insulin secreting tissue as a free graft has the potential to become a safe and simple procedure to cure diabetes. However, clinical results, i.e. achievement of insulin independency, are poor, in spite of the use of immunosuppressive regimens, which are regularly successful in whole organ transplantation. In contrast to whole organ grafts, which are revascularized immediately after transplantation, free pancreatic islet grafts require the process of revascularization in order to establish a microvascular network, sufficient for the nutritional blood supply. We have demonstrated for the first time in vivo images of the process of revascularization of free islet xenografts including microvascular phenomena during graft rejection. Rat islet xenografts were isolated by collagenase digestion and transplanted into hamster dorsal skinfold chambers. After 6, 10 and 14 days the microvasculature of the islet grafts was analyzed by means of intravital fluorescence microscopy. Xenogeneic grafts were revascularized during the first 6 days similarly compared to syngeneic grafts; however, on day 10 after transplantation a reduction in size of the microvascular network as well as a decrease in functional capillary density and a reduction in capillary red blood cell velocity were observed, accompanied by microvascular rejection phenomena, such as an increase of microvascular permeability, edema formation, capillary widening and intravascular accumulation of white blood cells (WBCs) with concomitant WBC-endothelium interaction in post-capillary venules. Treatment with 2.5 mg/kg/d (+/-)-15-deoxyspergualin could not completely alleviate these microvascular rejection phenomena.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Worldwide survey of neonatal screening for biotinidase deficiency.

Neonatal screening for biotinidase deficiency has been conducted in 14 countries since 1984. To 31 December 1990, 8,532,617 newborns were screened. One hundred and forty-two infants with biotinidase deficiency were identified; 76 infants with profound deficiency (less than 10% of mean normal serum activity) and 66 infants with partial deficiency (10-30% of mean normal activity). The estimated incidence of profound biotinidase deficiency is 1:112,271 (1:85,000 to 1:145,000; 95% confidence limits) and the incidence of partial deficiency is 1:129,282 (1:112,700 to 1:177,000). The incidence of combined profound and partial deficiency is 1:60,089 newborns (1:49,500 to 1:73,100). The estimated frequency of the allele for biotinidase deficiency is 0.004 and an estimated 1 in 123 individuals is heterozygous for the disorder.

Amidohydrolases↗
PubMed1991

Effects of age and biotin status on postnatal development of plasma biotinidase activity in rats.

Biotinidase activity was measured in plasmas of 1-, 7-, 14-, and 21-day-old rats from control dams and dams that had been fed a biotin-depleting diet from Day 15 of gestation. Biotinidase activity increased significantly in the plasma of rats from control and depleted mothers until Postnatal Day 14, after which there was a small but significant decline at Day 21. Differences between the mean activities of the two groups of pups on each sampling day were not significant and there were no significant differences in activity levels attributable to sex. Plasma albumin concentrations increased from birth until Day 21, and plasma biotinidase activity and albumin concentration were significantly correlated (r = +/- 0.43). We suggested that these two proteins may be controlled by a common mechanism in the early postnatal period, and that biotin deficiency does not affect the development of biotinidase activity. Because biotin-depleted neonatal pups show developmental changes in biotinidase activity similar to those of human newborns, and they can be produced reliably by depleting dams from Day 15 of gestation, they may be useful models for studying the developmental abnormalities associated with human biotinidase deficiency.

Age Factors↗
PubMed1991

Biotin uptake, utilization, and efflux in normal and biotin-deficient rat hepatocytes.

Biotin uptake, utilization, and efflux were studied in normal and biotin-deficient cultured rat hepatocytes. Biotin-deficient cells accumulate about 16-fold more biotin than do normal cells when incubated with a physiological concentration of biotin for 24 h. This difference is due to the greater amount of protein-bound biotin relative to free biotin in biotin-deficient hepatocytes, and is attributable to the presence of more apocarboxylases in deficient cells. The rate of biotin uptake and the rate of activation of the carboxylases, acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, and beta-methylcrotonyl-CoA carboxylase, are proportional to the concentration of exogenous biotin. Increases in carboxylase activities are proportional to the concentration of biotin only at exogenous biotin concentrations of less than 410 nM. Concentrations of 410 nM or more biotin increase carboxylase activities to normal or near normal. Biocytin inhibits biotin uptake at very high concentrations, whereas desthiobiotin and lipoic acid have no effect. Biocytin in the medium results in carboxylase activation either intracellularly or extracellularly by conversion to biotin by biotinidase. Investigation of the efflux of biotin from normal and biotin-deficient cells preincubated with the vitamin showed greater retention of biotin by biotin-deficient cells than by normal cells over 24 h. Retention of free biotin is similar in biotin-deficient and normal cells. The greater amount of biotin retained by biotin-deficient cells is accounted for by the greater amount of bound biotin in these cells. These results suggest that the free and bound biotin pools are independently regulated. The ready loss of free biotin from these cells has implications for the treatment of inherited, biotin-responsive carboxylase deficiencies.

Animals↗
PubMed1991

Phospholipid hydroperoxide glutathione peroxidase is a selenoenzyme distinct from the classical glutathione peroxidase as evident from cDNA and amino acid sequencing.

The primary structure of phospholipid hydroperoxide glutathione peroxidase (PHGPx) was partially elucidated by sequencing peptides obtained by cyanogen bromide cleavage and tryptic digestion and by isolating and sequencing corresponding cDNA fragments covering about 75% of the total sequence. Based on these data PHGPx can be rated as a selenoprotein homologous, but poorly related to classical glutathione peroxidase (GPx). Peptide loops constituting the active site in GPx are, however, strongly conserved in PHGPx. This suggests that the mechanism of action involving an oxidation/reduction cycle of a selenocysteine residue is essentially identical in PHGPx and GPx.

Amino Acid Sequence↗
PubMed1991

Bardet-Biedl syndrome in a Zimbabwean child.

An isolated case of Bardet-Biedl syndrome in a 12 year-old Zimbabwean boy is described. The patient presented with retinitis pigmentosa, polydactyly, mental retardation, obesity and hypogenitalism. To the best of the author's knowledge, it is the first paediatric case described in the African literature.

Child↗