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Biomedical subjects

B Wolf

Publications and source records attributed to B Wolf.

At least 91 records · Page 5Linked to original sources
PubMed1998

Delayed-onset profound biotinidase deficiency.

Children with biotinidase deficiency usually exhibit symptoms at several months to years of age. We describe four children who had symptoms later in childhood or during adolescence; they had motor limb weakness, spastic paresis, and eye problems, such as loss of visual acuity and scotomata, rather than the more characteristic symptoms observed in young untreated children with the disorder. These older children each have different mutations, but they are the same as those of children who have exhibited symptoms at an early age. Biotinidase deficiency should be considered in older children who suddenly experience limb weakness and/or spastic paresis and eye symptoms.

Acyltransferases↗
PubMed1998

Identification of rabbit immunoglobulin latent Ckappa1 allotype genes alters the concept of allelic inheritance.

In the rabbit, expression of immunoglobulin Ckappa1 light chain genes is believed to be under allelic control. Conventionally, four nominal allotypic variants, b4, b5, b6 and b9 have been shown to be co-dominantly expressed at the Ckappa1 gene locus. Analogously, the heavy chain allotypes, VHa1, VHa2 and VHa3, found in the V region, are also believed to be inherited co-dominantly. However, after our earlier discovery of non-allelic or latent allotypes in the serum and on cell surfaces. we subsequently reported that cDNA sequences for latent b5 and b6 were identical to nominal b5 and b6, respectively (Ishaq et al., 1990). The latent b5 cDNAs were from two homozygous b4,b4 rabbits; the latent b6 cDNA was found in a heterozygous b4,b9 rabbit. The cDNA sequences had been obtained from lymph nodes and spleens of rabbits which had been infected with Trypanosoma brucei in order to induce latent allotypes more consistently. In this article, employing spleen DNA from three different T. brucei-infected rabbits, (one, heterozygous b4,b9; two others, homozygous, b4,b4), we initially detected two bands by Southern analysis after Hind III digestion using a 624 base pair Ckappa1 b4 probe derived from a b4,b4 rabbit. However, the probe was non-specific allotypically as it hybridized to b5, b6 and b9 Ckappa1 DNA. Therefore, in order to search for the latent genes, we used allotype-specific oligonucleotides for b5, b6 and b9 to probe DNAs from both normal and T. brucei-infected rabbits by Southern blotting. At the outset, employing a b4 oligonucleotide probe, we detected a single 5.8 Kb segment in two b4,b4 rabbit DNAs after Bg1 II digestion. The findings, using the 624 base pair Ckappa1 b4 probe and the b4 oligomer, agreed with earlier data reported by others. Subsequently, we tested kidney, liver and spleen DNAs from one of these and other rabbits for genomic latent b5, b6 and b9 using these specific oligomeric probes. For each latent allotype, Southern analysis revealed latent-allotype specific DNA segments in the genome. After cosmid cloning and sequencing, latent kappa1, b5, b6 and b9 genes were found to be identical in their coding regions with their nominal counterparts. The genes contained at the 5' end the PyPyXPyAG RNA splice acceptor site found in immunoglobulin and many eukaryotic genes. as well as the termination codon TAG, together with AATAAA and the T-rich sites responsible for cleavage-polyadenylation in the untranslated region downstream from the 3' end. Single cosmid clones representing the b5, b6 and b9 genes were mapped for restriction sites which resulted in identifying putative Jk and enhancer regions. The results thus indicate that latent allotype genes are potentially functional. The data provide evidence that allotypes are not strictly controlled by allelic genes but must be regulated by an hierarchical mechanism which provides for synthesis of allelic allotypes mainly (10-20 mg/ml) together with non-allelic allotypes at lower concentrations (2-20 microg/ml) following activation of the latent genes. These results lay to rest the belief that Ckappa1 latent allotypes are the products of scrambled genes or idiotypic mimicry. Importantly, we now have the possibility of investigating the factors leading to latent allotype gene expression, the Vk and Jk regions associated with the genes, and therefore whether antibody diversity is expanded. We do not know, nor do we imply, that latent allotypes are present in all rabbits. However, since the four conventional Ckappa1 allotypes are present in the genome of several of our tested rabbits, and are presumably functional. we are faced with the probability that rabbit allotypes under certain conditions may in fact behave as isotypes and not allotypes.

Alleles↗
PubMed1998

Co-existence of somatic hypermutation and gene conversion in hypervariable regions of single Igkappa clones.

In the rabbit, recent investigations have provided evidence that gene conversion leads to the generation of diversity of heavy chain rearranged VH-DH-JH genes. No data have been published on a similar mechanism for rabbit light chains. In our laboratory, we initially infected rabbits with Trypanosoma brucei, which stimulates B-cell hyperplasia and hypergammaglobulinaemia. The heterozygous rabbits exhibited the Ckappa1 b4 and b9 kappa light chain allotypes. After reverse transcription of mRNA, and cloning and sequencing of cDNA, the Vkappa-Jkappa-Ckappa genes provided evidence for both somatic hypermutation and gene conversion. We saw that in each of the b4 and b9 kappa light chain cDNA, CDR1 and CDR3 carried both point mutation and provisional gene conversion traits. In the CDR2 region, point mutation and gene conversion inserts were observed in the b4 genes, with only gene conversion in two b9 genes. In the CDR regions, although some genes exhibited only somatic hypermutation or gene conversion, others showed linkage of both somatic hypermutation and gene conversion in the same sequence. This also marks the first time that somatic hypermutation and gene conversion in the same cloned CDR region has been observed in Vkappa1 genes; however, it has been seen earlier in rabbit heavy chain VH sequences. Furthermore, the addition of several codons to the CDR3 segment by gene conversion may have provided a mechanism for length variation. In addition, we demonstrated that Jkappa and framework region segments contained examples of somatic hypermutation. Confirmation of gene conversion necessitates that donor sequences be identified as providing the templated inserts. Thus after cloning two pseudogenes we found putative CDR3 donor segments for two CDR3 rearranged genes. The results offer additional mechanisms for the generation of diversity among rearranged rabbit kappa light chain genes. Whether there is a relationship or influence of gene conversion upon somatic hypermutation or vice versa is not discernable at present.

Amino Acid Sequence↗
PubMed1998

Neurological status in severely jaundiced Zimbabwean neonates.

Neurological status was studied in 50 jaundiced infants with a total serum bilirubin of > 400 mumol/l (23.4 mg/dl). Infants were assessed in the neonatal period with the Neonatal Neurological Examination and 4 months of age with the Infant Motor Screen. Twenty-six (52 per cent) infants were premature. Analysis of variance did not show a significant difference between gestational age, birth weight, and maximum total serum bilirubin or between gestational age, birth weight, and neurological optimality score. Based on the presence of abnormal neurological syndromes the infants were classified as normal (n = 27), suspect (n = 11), or abnormal (n = 12). Serum bilirubin levels were higher (p < 0.0001) and the neonatal neurological examination scores lower (p < 0.0001) in the seven (14 per cent) infants who received an exchange transfusion. In the transfused group four out of seven infants and in the non-transfused group seven out of 43 infants were classified as abnormal (p < 0.03). The Neonatal Neurological Examination was shown to be sensitive in detecting neurodevelopmental abnormalities in the neonatal period, with a sensitivity of 83 per cent, specificity of 88 per cent, positive predictive value of 62 per cent, and negative predictive value of 96 per cent.

Analysis of Variance↗
PubMed1998

Microsensor-aided measurements of cellular signalling and metabolism on tumor cells. The cell monitoring system (cms(R)).

Microsensors provide instruments particularly suited for the rapid, noninvasive and on-line analysis of cell and tissue cultures. The microsensor system presented in this paper is a modular arrangement of various planar and nonplanar sensor elements for the measurement of physiological parameters of cell cultures. An optic access to the cultures (e.g. for light microscopy and spectrophotometric techniques) is also provided for a parallel and comparative data acquisition. The system was originally designed for biomedical research in chemotherapy (predicative chemotherapy assays) and pharmacology but it turned out to be also an effective tool for toxicological and environmental research.

Biosensing Techniques↗
PubMed1998

Commissureless endocytosis is correlated with initiation of neuromuscular synaptogenesis.

We show that the Commissureless (COMM) transmembrane protein is required at neuromuscular synaptogenesis. All muscles in the Drosophila embryo express COMM during the period of motoneuron-muscle interaction. It is endocytosed into muscles before synaptogenesis. In comm loss-of-function mutants, motoneuron growth cones fail to initiate synaptogenesis at target muscles. This stall phenotype is rescued by supplying wild-type COMM to the muscles. Cytoplasmically truncated COMM protein fails to internalize. Expressing this mutant protein in muscles phenocopies the synaptogenesis defects of comm mutants. Thus, synaptogenesis initiation is positively correlated with endocytosis of COMM in postsynaptic muscle cells. We propose that COMM is an essential part of the dynamic cell surface remodeling needed by postsynaptic cells in coordinating synaptogenesis initiation.

Animals↗
PubMed1998

Hydrophilic-lipophilic drug carrier systems of bead cellulose and isopropyl myristate.

Solid carrier systems of bead cellulose (BC) and isopropyl myristate (IPM) as a lipophilic excipient showed high release rates for low prednisolone and high IPM content and decreasing rates for increasing drug and decreasing IPM content. The release of griseofulvin was decreased by increasing IPM content. The release was controlled by the solubility of the drugs in IPM and water, the crystalline state of the drugs, and the weight ratio of the components and was varied in a wide range by change of the prescriptions. The products were prepared according to a dispersion-coevaporation process and were received as flowable powders consisting of spherical porous particles. IPM with dispersed drug was incorporated into the pores of the beads and also precipitated on the bead surface. Depending on the ratio of IPM to drug, more or less crystalline drug particles were suspended in the liquid IPM film or the drug was amorphous dissolved. Investigations of wettability and water uptake gave hints to more lipophilic properties. The advantage of the coprecipitates was the combination of a hydrophilic carrier and a lipophilic excipient as a flowable system for controlled release.

Cellulose↗
PubMed1998

Prenatal diagnosis of heterozygosity for biotinidase deficiency by enzymatic and molecular analyses.

Biotinidase deficiency is characterized by neurological and cutaneous abnormalities that can be prevented or ameliorated by oral biotin therapy. A child with biotinidase deficiency went undiagnosed for a long period and has irreversible neurological deficits despite biotin treatment. This child is homozygous for the most common mutation (G98:d7i3) found in symptomatic children with the disorder. The parents insisted on having prenatal diagnosis in a subsequent pregnancy to alleviate their anxiety about having another affected child. Mutation analysis of DNA obtained directly from amniotic fluid and from cultured amniocytes revealed that the fetus was heterozygous for the mutation. Maternal cell contamination of the amniocytes was excluded by genotype analysis. Biotinidase activity in extracts of cultured amniocytes revealed 40 per cent of mean normal activity. At birth, the infant was confirmed to be heterozygous by serum enzyme analysis. This is the first report of the use of molecular analysis for the prenatal diagnosis for biotinidase deficiency.

Amidohydrolases↗
PubMed1998

Screening for diabetes on a vascular ward: lessons from an audit.

Owing to the high prevalence of diabetes mellitus in patients with peripheral arterial disease, screening for this disorder is necessary on a vascular ward. Our current practice of random plasma glucose (RPG) testing on every admission was reviewed. This test, although crude, excludes diabetes if the cutoff level is set as low as 6.0 mmol/L. A total of 36% of our patients had an abnormal result, but this was not further acted upon. A further 19% had no test result recorded at all. This practice is inadequate and has resulted in the following implementations: (1) every patient with clinical evidence of arterial disease should have their RPG level measured; (2) patients with a level > 6.0 mmol/L should have a fasting plasma glucose level estimated; and (3) patients with an abnormal fasting plasma glucose level should be referred to the diabetic clinic.

Aged↗
PubMed1998

The predictive value of developmental testing of extremely jaundiced African infants.

The predictive value of the Neonatal Neurological Examination (NNE) adapted from Prechtl (1977) and the Infant Motor Screen (IMS) from Nickel (1989) at 4 months was studied in severely jaundiced infants in Zimbabwe. Fifty infants were examined with the NNE, 41 with the IMS and 43 with the Bayley Scales of Infant Development (BSID) (Bayley 1969). Five infants had choreoathetosis and six had a motor delay at age 1 year. The NNE and IMS proved to be sensitive instruments particularly when two infants who became malnourished after the neonatal period were excluded. Logistic regression was used to investigate the relation between the BSID and five selected predictors from the NNE. This resulted in a correct classification of 93%. By using only the predictors acoustic blink and traction response, 80% of the infants were correctly classified but the number of false negatives was reduced from three to one.

Black People↗
PubMed1997

Profound biotinidase deficiency in two asymptomatic adults.

Biotinidase deficiency is an autosomal-recessive disorder of biotin recycling. Children with profound biotinidase deficiency usually have neurological and cutaneous symptoms in early childhood, but they may not develop symptoms until adolescence. We now report on a man and a woman with profound biotinidase deficiency who are asymptomatic and who were diagnosed only because their biotinidase-deficient children were identified by newborn screening. These adults have never exhibited symptoms of the disorder and are homozygous for two different mutations resulting in different aberrant enzymes. There is no evidence of an increased dietary intake of biotin to explain why they have remained asymptomatic. Although these adults may still be at risk for developing symptoms, they could represent a small group of individuals with profound biotinidase deficiency who will never develop clinical problems. Their lack of symptoms suggests that there are probably epigenetic factors that protect some enzyme-deficient individuals from developing symptoms. These individuals broaden the spectrum of expression of biotinidase deficiency.

Adult↗
PubMed1997

Mutation (Q456H) is the most common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States.

Biotinidase deficiency is an autosomal recessive disorder that can result in neurologic and cutaneous symptoms if not treated with biotin supplementation. We have identified the most common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States. 1368A-->C results in a substitution of histidine for glutamine 456 (Q456H) in exon D of the biotinidase gene. This mutation was found in at least one allele in 14 unrelated children from 27 different families or 15 of 54 alleles studied (28%). This mutation was not identified in 41 normal adults using SSCA, nor was it found in 296 normal newborns using allele-specific oligonucleotide analysis, suggesting that this change is not a polymorphism. In addition, biochemical data from a child homozygous for Q456H suggest that the aberrant enzyme has very low biotinyl-hydrolase activity, lacks biotinyl-transferase activity, and is not recognized by antibody prepared to purified, normal human biotinidase. The ethnic backgrounds of the parents contributing the Q456H allele are varied but are generally northern European.

Acyltransferases↗
PubMed1997

[Microsensor-controlled feedback bioactuators as a semi-integrated basis for biophysical cancer treatment].

Acidic microenvironmental conditions combined with large hypoxic areas are ubiquitous hallmarks of most solid tumors. They result from a poorly organized vascularization and a deviant energy metabolism. There is convincing evidence supporting the hypothesis that such physico-chemical conditions promote the microevolution of malignant cells, inhibit the cellular immune response, and favor tumor cell invasion. In agreement with published data, our cell biological analyses and computer simulations indicate that treatment schemes which restore a tumor microenvironment reflecting that one found in normal tissues might improve the efficiency of immunotherapies and classical methods for cancer treatment. We suggest that the tumor microenvironment could be effectively monitored and manipulated by means of silicon-based feedback bioactuators which are controlled by integrated microsensors. In principle, miniaturized bioactuators can be implanted directly at the sites of inoperable tumors and metastases where they function as a "pH clamp" and thereby can reconstitute normal physicochemical conditions. Drug application could be precisely controlled by an integrated microprocessor. Our paper summarizes the current state of development of microsensor-based feedback bioactuators and outlines possible applications in biophysical cancer treatment.

Automation↗
PubMed1997

Extreme hyperbilirubinaemia in Zimbabwean neonates: neurodevelopmental outcome at 4 months.

UNLABELLED: As part of a prospective study of severely jaundiced Zimbabwean infants, the relationship between maximum total serum bilirubin (TSB) concentration in the neonatal period and neurodevelopmental outcome at the corrected age of 4 months was studied. Fifty infants with a TSB of > 400 micromol/l (23.4 mg/dl) were enrolled and screened with a neonatal neurological examination (NNE). The cause of jaundice was low birth weight in 22 (44%), ABO incompatability in 8 (16%), sepsis in 8 (16%) and congenital syphilis (6%) in 3 infants. In 9 infants a cause could not be determined. At 4 months, 2 infants had died and 3 were lost to follow up, leaving 45 infants for the infant motor screen (IMS) at 4 months of age. Mean TSB in the neonatal period was 485 micromol/l (28.2 mg/dl), and 7 infants received an exchange transfusion. Mean TSB of the infants with an exchange transfusion was 637 micromol/l (37.2 mg/dl) (range 429-865 micromol/l (25-50.3 mg/dl)) and of the infants without transfusion 459 micromol/l (26.8 mg/dl) (range 400 740 micromol/l (23.4-43 mg/dl)) (P < 0.0001). The TSB was not associated with birth weight, gestational age, gender or head circumference of the baby. On the IMS, 6 of 45 (13.3%) infants scored abnormal, 6 (13.3%) suspect and 33 (73%) scored normal. Three of the six (50%) remaining infants who received an exchange transfusion scored abnormal on the IMS while only 3 of the 39 (8%) infants without exchange transfusion were abnormal. CONCLUSION: More than 25% of infants with a TSB of > 400 micromol/l (23.4 mg/dl) scored abnormal or suspect at 4 months of age and half of these infants already showed irreversible neurological symptoms. All infants who scored abnormal or suspect on the IMS with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) had haemolytic disease or were premature.

Bilirubin↗
PubMed1997

Arg538 to Cys mutation in a CpG dinucleotide of the human biotinidase gene is the second most common cause of profound biotinidase deficiency in symptomatic children.

Biotinidase deficiency is an autosomal recessively inherited disorder in the recycling of the vitamin biotin. The most common mutation that causes profound biotinidase deficiency in symptomatic individuals is a deletion/insertion (G98:d7i3) that occurs in exon B of the biotinidase gene. We now report the second most common mutation, a C-to-T substitution (position 1612) in a CpG dinucleotide in exon D of the biotinidase gene. This mutation results in the substitution of a cysteine for arginine538 (designated R538C) and was found in 10 of 30 symptomatic children with profound biotinidase deficiency, 5 of whom also have the G98:d7i3 mutation. This mutation was not found in DNA samples from 32 individuals with normal biotinidase activity, but was found in one individual with enzyme activity in the heterozygous range. This mutation was not detected in 371 randomly selected, normal individuals using allele-specific oligonucleotide hybridization analysis. Aberrant biotinidase protein was not detectable in extracts of fibroblasts from a child who is homozygous for the R538C mutation, but was present in less than normal concentration in identical extracts treated with beta-mercaptoethanol. Because there is no detectable biotinidase protein in sera of children who are homozygous for the R538C mutation and in combination with the deletion/insertion mutation, the R538C mutation likely results in inappropriate intra- or intermolecular disulfide bond formation, more rapid degradation of the aberrant enzyme, and failure to secrete the residual aberrant enzyme from the cells into blood.

Acyltransferases↗
PubMed1997

Monitoring of cellular behaviour by impedance measurements on interdigitated electrode structures.

A new method for on-line and real-time monitoring of concentration, growth and physiological state of cells in culture is described. This biosensor is based on impedance measurements of adherently growing cells on interdigitated electrode structures (IDES). The measurements can be performed for several days as there is no detectable electrical influence on the cells. The versatility of this new sensor is shown with some exemplary experiments. Cell density, growth and long-term behaviour of cells on the electrodes clearly change the impedance of the IDES. Both, the global influence of serum components (deprivation of foetal bovine serum) and the toxic effects of heavy metal ions (cadmium) result in changes of the sensor signal and can be visualized.

Animals↗