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C Witt

Publications and source records attributed to C Witt.

At least 19 recordsLinked to original sources
PubMed2002

Association between presence of HLA-B*5701, HLA-DR7, and HLA-DQ3 and hypersensitivity to HIV-1 reverse-transcriptase inhibitor abacavir.

BACKGROUND: The use of abacavir--a potent HIV-1 nucleoside-analogue reverse-transcriptase inhibitor--is complicated by a potentially life-threatening hypersensitivity syndrome in about 5% of cases. Genetic factors influencing the immune response to abacavir might confer susceptibility. We aimed to find associations between MHC alleles and abacavir hypersensitivity in HIV-1-positive individuals treated with abacavir. METHODS: MHC region typing was done in the first 200 Western Australian HIV Cohort Study participants exposed to abacavir. Definite abacavir hypersensitivity was identified in 18 cases, and was excluded in 167 individuals with more than 6 weeks' exposure to the drug (abacavir tolerant). 15 individuals experienced some symptoms but did not meet criteria for abacavir hypersensitivity. p values were corrected for comparisons of multiple HLA alleles (p(c)) by multiplication of the raw p value by the estimated number of HLA alleles present within the loci examined. FINDINGS: HLA-B*5701 was present in 14 (78%) of the 18 patients with abacavir hypersensitivity, and in four (2%) of the 167 abacavir tolerant patients (odds ratio 117 [95% CI 29-481], p(c)<0.0001), and the HLA-DR7 and HLA-DQ3 combination was found in 13 (72%) of hypersensitive and five (3%) of tolerant patients (73 [20-268], p(c)<0.0001 ). HLA-B*5701, HLA-DR7, and HLA-DQ3 were present in combination in 13 (72%) hypersensitive patients and none of the tolerant patients (822 [43-15 675], p(c)<0.0001). Other MHC markers also present on the 57.1 ancestral haplotype to which the three markers above belong confirmed the presence of haplotype-specific linkage disequilibrium, and mapped potential susceptibility loci to a region bounded by C4A6 and HLA-C. Within the entire abacavir-exposed cohort (n=200), presence of HLA-B*5701, HLA-DR7, and HLA-DQ3 had a positive predictive value for hypersensitivity of 100%, and a negative predictive value of 97%. INTERPRETATION: Genetic susceptibility to abacavir hypersensitivity is carried on the 57.1 ancestral haplotype. In our population, withholding abacavir in those with HLA-B*5701, HLA-DR7, and HLA-DQ3 should reduce the prevalence of hypersensitivity from 9% to 2.5% without inappropriately denying abacavir to any patient.

Adult↗
PubMed2002

BAX and p16INK4A are independent positive prognostic markers for advanced tumour stage of nonsmall cell lung cancer.

Clinical studies suggest prognostic relevance of p16INK4A in nonsmall cell lung cancer (NSCLC) while conflicting results for p53 have been published. However, the importance of the apoptosis regulating gene BAX, a downstream regulator of p53, on the prognosis of NSCLC is unknown. The present study investigated the prognostic relevance of BAX with respect to the status of p53 and P16INK4A in 61 patients with advanced NSCLC. Protein expression of BAX, p53 and p16INK4A was investigated retrospectively by immunohistochemistry. Tumour deoxyribonucleic acid (DNA) was screened for p53 mutations by single strand-conformation polymorphism polymerase chain reaction (PCR) and BAX frameshift mutations by fragment length analysis. Patients with positive BAX protein expression had a significantly longer median survival (14 months) than those patients without BAX expression (6 months, p=0.0004). In contrast, p53 status did not influence prognosis. Patients with p161NK4A negative tumours had a significantly shorter survival (4 months) than those with p16INK41 protein expression (15 months, p=0.0001). Furthermore, the loss of p16INK4A protein expression correlated strongly with the pressure of distant and advanced lymph-node metastases. The best survival was seen in a subgroup of 20 patients with positive p16INK4A expression and intact BAX (p=0.0002). The results of the present study suggest that the loss of BAX and p16INK4A expression are independent markers for poor prognosis in nonsmall cell lung cancer. The study suggests that multimarker analysis of genes involved in apoptosis may be useful for determining individual therapy and for identifying targets for gene-replacement therapy. This should be assessed in a prospective study with a larger cohort of patients.

Aged↗
PubMed2001

Identification and biochemical characterization of Arabidopsis thaliana sulfite oxidase. A new player in plant sulfur metabolism.

In mammals and birds, sulfite oxidase (SO) is a homodimeric molybdenum enzyme consisting of an N-terminal heme domain and a C-terminal molybdenum domain (EC ). In plants, the existence of SO has not yet been demonstrated, while sulfite reductase as part of sulfur assimilation is well characterized. Here we report the cloning of a plant sulfite oxidase gene from Arabidopsis thaliana and the biochemical characterization of the encoded protein (At-SO). At-SO is a molybdenum enzyme with molybdopterin as an organic component of the molybdenum cofactor. In contrast to homologous animal enzymes, At-SO lacks the heme domain, which is evident both from the amino acid sequence and from its enzymological and spectral properties. Thus, among eukaryotes, At-SO is the only molybdenum enzyme yet described possessing no redox-active centers other than the molybdenum. UV-visible and EPR spectra as well as apparent K(m) values are presented and compared with the hepatic enzyme. Subcellular analysis of crude cell extracts showed that SO was mostly found in the peroxisomal fraction. In molybdenum cofactor mutants, the activity of SO was strongly reduced. Using antibodies directed against At-SO, we show that a cross-reacting protein of similar size occurs in a wide range of plant species, including both herbacious and woody plants.

Amino Acid Sequence↗
PubMed2001

[Virtual bronchoscopy].

Flexible bronchoscopy represents a clinically well-established invasive diagnostic tool. Virtual bronchoscopies, calculated from thin-slice CT sections, allow astonishing immitations of reality although principal differences exist between both technologies: the fact that colour representation is artificial and concommitant interventions are impossible limits the clinical use of virtual bronchoscopy. However, its value increases when calculations can be attained within minutes due to technological advancements, and when virtually any chest CT is suitable for further postprocessing. Indications, findings and the clinical role of virtual bronchoscopy are discussed.

Bronchoscopy↗
PubMed2001

Endotracheal balloon dilatation and stent implantation in benign stenoses.

BACKGROUND: Tracheal reconstruction is the treatment of choice in nontumorous tracheal stenoses, but recurrences and concomitant medical conditions limit this approach. We investigated the outcome after balloon dilatation and silicone stent implantation. METHODS: Forty-two patients with inoperable tracheal stenoses underwent balloon dilatation and afterward silicone stent implantation. Patients were divided into two groups, in group A 24 patients received tracheal stents as a temporary treatment. In group B, definitive stenting was done in 18 patients with severe concomitant medical conditions that did not allow for stent removal. RESULTS: Immediate results were satisfactory in all patients. In group A, stents could be removed in 12 patients after a mean interval of 20 months. Restenting was not required during the following 18.9 months. Twelve patients are still waiting for stent removal after a mean follow-up of 20 months. In group B, mean follow-up is now 48.4 months. Complications included retained secretions, dislocation, and granuloma formation. CONCLUSIONS: Stenting after balloon dilatation is safe and effective in benign tracheal stenoses. After temporary use, stents can be removed when local and general conditions permit. In all other patients, stenting proved beneficial for 5 years as more definitive treatment.

Adult↗
PubMed2001

Titin-actin interaction in mouse myocardium: passive tension modulation and its regulation by calcium/S100A1.

Passive tension in striated muscles derives primarily from the extension of the giant protein titin. However, several studies have suggested that, in cardiac muscle, interactions between titin and actin might also contribute to passive tension. We expressed recombinant fragments representing the subdomains of the extensible region of cardiac N2B titin (tandem-Ig segments, the N2B splice element, and the PEVK domain), and assayed them for binding to F-actin. The PEVK fragment bound F-actin, but no binding was detected for the other fragments. Comparison with a skeletal muscle PEVK fragment revealed that only the cardiac PEVK binds actin at physiological ionic strengths. The significance of PEVK-actin interaction was investigated using in vitro motility and single-myocyte mechanics. As F-actin slid relative to titin in the motility assay, a dynamic interaction between the PEVK domain and F-actin retarded filament sliding. Myocyte results suggest that a similar interaction makes a significant contribution to the passive tension. We also investigated the effect of calcium on PEVK-actin interaction. Although calcium alone had no effect, S100A1, a soluble calcium-binding protein found at high concentrations in the myocardium, inhibited PEVK-actin interaction in a calcium-dependent manner. Gel overlay analysis revealed that S100A1 bound the PEVK region in vitro in a calcium-dependent manner, and S100A1 binding was observed at several sites along titin's extensible region in situ, including the PEVK domain. In vitro motility results indicate that S100A1-PEVK interaction reduces the force that arises as F-actin slides relative to the PEVK domain, and we speculate that S100A1 may provide a mechanism to free the thin filament from titin and reduce titin-based tension before active contraction.

Actins↗
PubMed2001

Morphological characterization of microspheres, films and implants prepared from poly(lactide-co-glycolide) and ABA triblock copolymers: is the erosion controlled by degradation, swelling or diffusion?

Erosion of biodegradable parenteral delivery systems (PDS) based on ABA copolymers consisting of poly(L-lactide-co-glycolide) (PLGA) A-blocks attached to polyethylene oxide (PEO) B-blocks, or PLGA is important for the release of macromolecular drugs. The degradation behavior of four types of PDS, namely extruded rods, tablets, films and microspheres, was studied with respect to molecular weight, mass, polymer composition and shape and microstructure of the PDS. For each device the onset time of bulk erosion (t(on)) and the apparent rate of mass loss (k(app)) were calculated. In the case of PLGA, the t(on) was 16.2 days for microspheres, 19.2 days for films and 30.1 days for cylindrical implants and tablets. The k(app) was 0.04 days(-1) for microspheres, 0.09 days(-1) for films, 0.11 days(-1) for implants and 0.10 days(-1) for tablets. The degradation rates were in the same range irrespective of the geometry and the micrographs of eroding PDS demonstrated pore formation; therefore, a complex pore diffusion mechanism seems to control the erosion of PLGA devices. In contrast, PDS based on ABA copolymers showed swelling, followed by a parallel process of molecular weight degradation and polymer erosion, independent of the geometry. The contact angles of ABA films increased either with decreasing PEO content or with increasing chain length of the PEO B-blocks. In summary, the insertion of a hydrophilic B-block leads to an erosion controlled by degradation of ABA copolymers, whereas for PLGA a complex pore diffusion of degradation products controls the rate of bulk erosion.

Biodegradation, Environmental↗
PubMed2001

Gene transfer into solid tumours--is a special application device beneficial?

The replacement of inactivated tumour suppressor genes is a promising approach in cancer therapy. The aim of this study was to evaluate the influence of technical determinants on the efficiency of adenoviral-mediated gene transfer into solid tumours. Therefore, we compared the efficacy of two different injection needle types, a conventional needle and a modified needle characterised by perforations at the side of the shaft in vivo. The total amount of adenoviral vector DNA and the activity of the transferred reporter gene were quantitatively analysed by polymerase chain reaction (PCR) specific for the E4 region of the Ad vector genome and the beta-galactosidase assay, respectively. The levels of adenoviral DNA, as well as the total beta-galactosidase activity, varied widely, but were not significantly different for the two groups. These results suggest, that the efficiency of intratumoral gene transfer cannot be improved by the design of the application device.

Adenoviridae↗
PubMed2001

HLA-DRB1 DNA sequencing based typing: an approach suitable for high throughput typing including unrelated bone marrow registry donors.

The HLA-DRB1 sequencing based typing strategies reported to date require separate amplifications of each sample with a series of group-specific primers followed by sequencing of any resulting polymerase chain reaction (PCR) products. Whilst this results in high resolution typing in the majority of cases, a number of unnecessary amplifications are performed. We report here a novel approach where amplification of the second exon of HLA-DRB1 is performed in a single tube for all alleles. Retrospective analysis of 642 consecutive Western Australian unrelated bone marrow registry donors has shown that this approach results in unambiguous typings in 71.1% of cases. Ambiguities can be readily resolved if necessary with a single additional sequencing reaction on the original PCR product.

Alleles↗
PubMed2001

Lymphatic filariasis: an infection of childhood.

Lymphatic filariasis (LF), already recognized as a widespread, seriously handicapping disease of adults, was generally thought to occur only sporadically in children. New, highly sensitive diagnostic tests (antigen detection, ultrasound examination) now reveal, however, that LF is first acquired in childhood, often with as many as one-third of children infected before age 5. Initial damage to the lymphatic system by the parasites generally remains subclinical for years or gives rise only to non-specific presentations of adenitis/adenopathy; however, especially after puberty the characteristic clinical features of the adult disease syndromes (lymphoedema, hydrocoele) manifest themselves. Recognizing that LF disease starts its development in childhood has immediate practical implications both for management and prevention of the disease in individual patients and for the broader public health efforts to overcome all childhood illnesses. For the new World Health Organization (WHO)-supported, public-/private-sector collaboration (Global Alliance) to eliminate LF through once-yearly drug treatment, this recognition means that children will be not only the principal beneficiaries of LF elimination but also a population particularly important to target in order for the programme to achieve its twin goals of interrupting transmission and preventing disease.

Adolescent↗
PubMed2001

Quantification of the effect of inhaled budesonide on airway inflammation in intermittent asthma by bronchitis index.

The bronchitis index (BI) is a scoring system for the visual quantification of airway inflammation by flexible bronchoscopy. A prospective study was carried out to determine whether patients with intermittent asthma present a considerable visible airway inflammation. Ten steroid-naive patients with intermittent asthma taking only inhaled beta2-agonists were enrolled and received budesonide (800 microg/day) over a period of 4 weeks. The airway inflammation was assessed by flexible electronic videobronchoscopy before and after the steroid treatment phase and quantified using the BI. Despite normal pulmonary function, all patients with intermittent asthma showed a marked visible airway inflammation that was reversed by a 4-week treatment with the inhaled steroid budesonide. The present study demonstrates that the BI may be useful as a clinical research tool for the assessment and quantification of airway inflammation in asthma. Furthermore, our results support the widely recognized theory that airway inflammation is present even in patients with mild asthma, and emphasize the necessity of an early therapy with inhaled steroids.

Administration, Inhalation↗
PubMed2001

Tobacco plants that lack expression of functional nitrate reductase in roots show changes in growth rates and metabolite accumulation.

When tobacco is provided with a high nitrate supply, only a small amount of the nitrate taken up by the roots is immediately assimilated inside the roots, while the majority is transported to the leaves where it is reduced to ammonium. To elucidate the importance of root nitrate assimilation, tobacco plants have been engineered that showed no detectable nitrate reductase activity in the roots. These plants expressed the nitrate reductase structural gene nia2 under control of the leaf-specific potato promoter ST-LS1 in the nitrate reductase-mutant Nia30 of Nicotiana tabacum. Homozygous T2-transformants grown in sand or hydroponics with 5.1 mM nitrate had approximately 55-70% of wild-type nitrate reductase acivity in leaves, but lacked nitrate reductase acivity in roots. These plants showed a retarded growth as compared with wild-type plants. The activation state of nitrate reductase was unchanged; however, diurnal variation of nitrate reductase acivity was not as pronounced as in wild-type plants. The transformants had higher levels of nitrate in the leaves and reduced amounts of glutamine both in leaves and roots, while roots showed higher levels of hexoses (3-fold) and sucrose (10-fold). It may be concluded that the loss of nitrate reductase acivity in the roots changes the allocation of reduced nitrogen compounds and sugars in the plant. These plants will be a useful tool for laboratories studying nitrate assimilation and its interactions with carbon metabolism.

Biological Transport↗
PubMed2000

Series of exon-skipping events in the elastic spring region of titin as the structural basis for myofibrillar elastic diversity.

Titins are megadalton-sized filamentous polypeptides of vertebrate striated muscle. The I-band region of titin underlies the myofibrillar passive tension response to stretch. Here, we show how titins with highly diverse I-band structures and elastic properties are expressed from a single gene. The differentially expressed tandem-Ig, PEVK, and N2B spring elements of titin are coded by 158 exons, which are contained within a 106-kb genomic segment and are all subject to tissue-specific skipping events. In ventricular heart muscle, exons 101 kb apart are joined, leading to the exclusion of 155 exons and the expression of a 2.97-MDa cardiac titin N2B isoform. The atria of mammalian hearts also express larger titins by the exclusion of 90 to 100 exons (cardiac N2BA titin with 3.3 MDa). In the soleus and psoas skeletal muscles, different exon-skipping pathways produce titin transcripts that code for 3.7- and 3.35-MDa titin isoforms, respectively. Mechanical and structural studies indicate that the exon-skipping pathways modulate the fractional extensions of the tandem Ig and PEVK segments, thereby influencing myofibrillar elasticity. Within the mammalian heart, expression of different levels of N2B and N2BA titins likely contributes to the elastic diversity of atrial and ventricular myofibrils.

Amino Acid Sequence↗
PubMed2000

Molecular tools for the study of titin's differential expression.

Although vertebrate genomes appear to contain only one titin gene, a large variety of quite distinct titin isoforms are expressed in striated muscle tissues. The isoforms appear to be generated by a series of complex, not yet fully characterized differential splicing mechanisms. Here, we provide an overview of the titin-specific antibodies that have been raised by our laboratory to study individual differentially expressed isoforms of titin. The staining patterns obtained in different tissues will contribute to the identification of both the particular titin isoforms that are expressed in the different tissues, as well as their intracellular distributions. In addition, antibodies to titin that are available are rapidly allowing for the refinement of our knowledge of titin's elastic spring properties. Knowledge of the nature and structure of vertebrate titins that may also be expressed in nonmuscle tissues may be broadened using these antibodies.

Actin Cytoskeleton↗