Biomedical subjects

A Stolz

Publications and source records attributed to A Stolz.

At least 19 recordsLinked to original sources

PubMed2006

Preliminary crystallographic analysis of salicylate 1,2-dioxygenase from Pseudaminobacter salicylatoxidans.

Salicylate 1,2-dioxygenase, a new ring-fission dioxygenase from the naphthalenesulfonate-degrading strain Pseudaminobacter salicylatoxidans which oxidizes salicylate to 2-oxohepta-3,5-dienedioic acid by a novel ring-fission mechanism, has been crystallized. Diffraction-quality crystals of salicylate 1,2-dioxygenase were obtained using the sitting-drop vapour-diffusion method at 277 K from a solution containing 10%(w/v) ethanol, 6%(w/v) PEG 400, 0.1 M sodium acetate pH 4.6. Crystals belong to the primitive tetragonal space group P4(3)2(1)2 or P4(1)2(1)2, with unit-cell parameters a = 133.3, c = 191.51 A. A complete data set at 100 K extending to a maximum resolution of 2.9 A was collected at a wavelength of 0.8423 A. Molecular replacement using the coordinates of known extradiol dioxygenases structures as a model has so far failed to provide a solution for salicylate 1,2-dioxygenase. Attempts are currently being made to solve the structure of the enzyme by MAD experiments using the anomalous signal of the catalytic Fe(II) ions. The salicylate 1,2-dioxygenase structural model will assist in the elucidation of the catalytic mechanism of this ring-fission dioxygenase from P. salicylatoxidans, which differs markedly from the known gentisate 1,2-dioxygenases or 1-hydroxy-2-naphthoate dioxygenases because of its unique ability to oxidatively cleave salicylate, gentisate and 1-hydroxy-2-naphthoate with high catalytic efficiency.

Bacteria, Aerobic↗

PubMed2005

29Na: defining the edge of the island of inversion for Z=11.

The low-energy level structure of the exotic Na isotopes (28,29)Na has been investigated through beta-delayed gamma spectroscopy. The N=20 isotones for Z=10-12 are considered to belong to the "island of inversion" where intruder configurations dominate the ground state wave function. However, it is an open question as to where and how the transition from normal to intruder dominated configurations happens in an isotopic chain. The present work, which presents the first detailed spectroscopy of (28,29)Na, clearly demonstrates that such a transition in the Na isotopes occurs between 28Na (N=17) and 29Na (N=18), supporting the smaller N=20 shell gap in neutron-rich sd shell nuclei. The evidence for inverted shell structure is found in beta-decay branching ratios, intruder dominated spectroscopy of low-lying states, and shell model analysis.

Journal Article↗

PubMed2005

Half-life of the doubly magic r-process nucleus 78Ni.

Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r process). 78Ni is the only doubly magic nucleus that is also an important waiting point in the r process, and serves as a major bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been experimentally deduced for the first time at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University, and was found to be 110(+100)(-60) ms. In the same experiment, a first half-life was deduced for 77Ni of 128(+27)(-33) ms, and more precise half-lives were deduced for 75Ni and 76Ni of 344(+20)(-24) ms and 238(+15)(-18) ms, respectively.

Journal Article↗

PubMed2005

[Transplantation of the lung lobe].

Absolute deficiency of suitable donors and disproportions in the implant size and the pleural cavity size, limit the lung transplantation numbers and result in high mortality rates on lists. The waiting lobar lung lobes transplantation technique may help to resolve the problem of increasing the rate of satisfied patients. This work presents a case of the first lobar lung transplantation in the Czech Republic in the patient with exogenous allergic alveolitis.

Brain Death↗

PubMed2004

Shell structure of the near-dripline nucleus 23O.

Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope 23O. The 22O fragments produced in one-nucleon removal from 23O at 938 MeV/nucleon in a carbon target were detected in coincidence with deexciting gamma rays. The widths of the longitudinal momentum distributions of the 22O fragments and the one-neutron removal cross sections were interpreted in the framework of a simple theoretical model which favors the assignment of Ipi = 1/2+ to the 23O ground state.

Journal Article↗

PubMed2004

Lowest excitations in 56Ti and the predicted N=34 shell closure.

Recent experimental characterization of the subshell closure at N=32 in the Ca, Ti, and Cr isotones has stimulated shell-model calculations that indicated the possibility that the N=34 isotones of these same elements could exhibit characteristics of a shell closure, namely, a high energy for the first excited 2(+) level. To that end, we have studied the decay of 56Sc produced in fragmentation reactions and identified new gamma rays in the daughter N=34 isotone 56Ti. The first 2(+) level is found at an energy of 1127 keV, well below the expected position that would indicate the presence of an N=34 shell closure in 56Ti.

Journal Article↗

PubMed2004

[Specific features of lung collection from a donor with a beating heart: criteria and technique].

Lung transplantations remain the latest organ transplantation gaining a broad spectrum of clinical applications. It has become an approved treatment method for patients suffering from lung disorders in the terminal phase. The number of transplantations is limited by a lack of suitable organs, increasing patients waiting lists mortality rates. This article provides information on criteria required for the lung collections to be accepted, and also, a detailed description of the combined lung and heart collection technique for unilateral of bilateral lung transplantations. The above technique has been used routinely, undergoing several modifications, in the Czech Republic since 1997, when the lung transplantation programme commenced. 60 lung collections from exited donors were performed until the end of 2003. The aim of the information provided in this article, is to aid mutual cooperation with M.D.s caring for the donor and cooperation of surgeons of all teams, participating in the multiorgan transplantation, which will finally allow the number and quality of the collected organs to be increased.

Brain Death↗

PubMed2004

[Lung transplantation for primary pulmonary hypertension].

Significant advances in the treatment of primary pulmonary hypertension (PPH) have been achieved in the past decade. Continuous intravenous prostacyclin and lung transplantation are complex and effective approaches in the therapy of PPH. Indication, technique, postoperative care and results of lung transplantation for PPH are discussed.

Humans↗

PubMed2003

Conversion of aliphatic 2-acetoxynitriles by nitrile-hydrolysing bacteria.

The enzymatic hydrolysis of the nitrile group of different 2-acetoxynitriles was investigated in order to obtain catalysts that chemoselectively hydrolyse nitriles in the presence of ester groups. The biotransformation of four 2-acetoxynitriles [2-acetoxybutenenitrile (ABN), 2-acetoxyheptanenitrile (AHN), 2-acetoxy-2-(2-furyl)acetonitrile (AFN), and 2-acetoxy-2,3,3-trimethylbutanenitrile (ATMB)] by different bacterial strains that synthesise nitrilases or nitrile hydratases was studied. ABN, AHN and AFN were converted by various microorganisms belonging to different bacterial genera (e.g. Pseudomonas or Rhodococcus) expressing either nitrilase or nitrile hydratase activities. In contrast, no metabolism of the sterically hindered substrate ATMB was observed. All wild-type strains investigated formed considerable amounts of cyanide and aldehydes from the 2-acetoxynitriles. This indicated the presence of esterases converting the 2-acetoxynitriles to 2-hydroxynitriles, which then spontaneously decomposed to the corresponding aldehydes and cyanide. In order to suppress unwanted side-reactions, biotransformations were performed with recombinant Escherichia coli strains that heterologously expressed nitrilase activities originating from Pseudomonas, Rhodococcus, or Synechocystis strains. The attempted conversion of the 2-acetoxynitriles to almost stoichiometric amounts of the corresponding 2-acetoxycarboxylic acids was finally achieved by using either a recombinant E. coli strain that highly overexpressed the nitrilase gene from the pseudomonad or the purified enzyme derived from this strain.

Acetonitriles↗

PubMed2003

Spin polarization of 37K produced in a single-proton pickup reaction at intermediate energies.

Spin polarization of 37K nuclei produced via single proton pickup from a 9Be target by a beam of 150 MeV/nucleon 36Ar has been observed. Positive spin polarization with magnitude (8.5+/-0.6)% was deduced near the peak of the 37K momentum distribution. The variation of the spin polarization as a function of outgoing 37K momentum is explained by a classical conservation model, as previously applied to describe the induced spin polarization observed for fragments produced in intermediate-energy heavy-ion reactions, with the condition that the picked-up proton has an average momentum equal to the Fermi momentum and is aligned along the incident beam direction.

Journal Article↗

PubMed2003

Cloning and characterization of the gene coding for the aerobic azoreductase from Pigmentiphaga kullae K24.

The gene coding for an aerobic azoreductase was cloned from Pigmentiphaga kullae K24, which is able to grow with the carboxylated azo compound 1-(4'-carboxyphenylazo)-4-naphthol (carboxy-Orange I) as sole source of carbon and energy. The gene encoded a protein with a molecular weight of 20,557 Da, with a conserved putative NAD(P)H-binding site in the amino-terminal region. The deduced amino acid sequence showed no further significant sequence homologies to previously studied aerobic azoreductases. The azoreductase was heterologously expressed in Escherichia coli and shown to convert the sulfonated azo dye Orange I and furthermore Magneson II [4-(4-nitrophenylazo)-1-naphthol].

Aerobiosis↗

PubMed2003

[A surgeon's view on the importance of positron emission tomography--PET (with emphasis on lung neoplasms)].

OBJECTIVE: PET became a successful method in preoperative evaluation of patients with cancer. We question whether PET scan can answer critical surgeons' requests such as distinguish benign and malign lesions, evaluation of cancer dissemination, evaluation of the pleural effusions, and also to detect early cancer recurrence. METHODS: Between September 1999 and December 2001, 39 patients underwent a PET scan and we evaluated its benefit in further treatment of patients. Standard PET techniques were used. RESULTS: In 20 patients (52%) results of PET scan were in correlation of clinical diagnosis and stage of cancer disease, partial difference between FDG-PET and clinical diagnosis was in 8 patients (20%), next treatment was changed in 11 patients (28%). CONCLUSION: We conclude, that dedicated PET could be valuable tool in the diagnosis and staging of cancer disease, especially in verifying cancer dissemination, recurrence of the cancer. PET scan can be misleading in evaluation of the mediastinal lymphnodes and pleural effusions.

Fluorodeoxyglucose F18↗

PubMed2003

[Lung transplantation--present status worldwide and in the Czech Republic].

Lung transplantation has evolved to a standard treatment modality for patients suffering from end-stage lung diseases and it provides very good short- and satisfactory long-term survival. Accepted indications for lung transplantation include chronic obstructive pulmonary disease (COPD) and other causes of emphysema (i.e., alpha-1-antitrypsin deficiency), parenchymal diseases (i.e., idiopathic pulmonary fibrosis), genetic disorders such as cystic fibrosis, vascular diseases (i.e., primary pulmonary hypertension), chronic infectious diseases (i.e., bronchiectasis), as well as rare indications such as lymphangioleiomyomatosis or sarcoidosis. Presented article reviews the current strategies in the treatment of lung transplant recipients, surgical techniques, limitations of and effects of lung transplantation.

Czech Republic↗

PubMed2002

Enhanced anaerobic degradation of polymeric azo compounds by Escherichia coli in the presence of low-molecular-weight redox mediators.

The effects of the redox mediator lawsone (2-hydroxy-1,4-naphthoquinone) on the ability of Escherichia coli to reduce anaerobically polymeric azo compounds were analysed. Two types of polymeric azo compounds were tested, that have been proposed as putative tools for the site-specific targeting of drugs to the colon. The first group of polymers consisted basically of linear chains of polymethacrylic acid or polymethylmethacrylate which were interrupted by subunits of 4,4'-bis(methacryloylamino)azobenzene. These polymers differed significantly in their hydrophilicity according to the relative proportion of polymethacrylic acid used for the polymerization procedure. The second group of polymers consisted of almost water-insoluble poly(ether-ester)azo polymers that were composed of 4-(6-hydroxyhexyl)oxy-phenylazobenzoate and 16-hydroxyhexadecanoate. The addition of lawsone to the anaerobically incubated cultures of E. coli resulted in a pronounced increase in the reduction rates of the water-soluble poly(methacrylate-co-4,4'-bis(methacryloylamino)azobenzene) and in a much smaller, but significant, increase in the reduction rates of the hydrophobic poly(ether-ester)azo polymers. An increase in the amount of azo groups resulted, for the hydrophobic poly(ether-ester)azo polymers, in an increased reduction rate in the presence of the redox mediator lawsone.

Azo Compounds↗

PubMed2001

Differential modulation of cellular death and survival pathways by conjugated bile acids.

BACKGROUND: The liver-derived McNtcp.24 cells transport bile acids and show distinctive responses to the two classes of conjugated bile acids. Whereas taurine-conjugated bile acids are non-toxic, glycine-conjugated bile acids efficiently induce apoptosis. The aim of this study was to determine if the differential sensitivity is limited to cells that normally transport bile acids and if bile acid binding proteins could reduce bile acid-mediated apoptosis. The apical sodium/bile acid co-transporter (asbt) was expressed in Chinese hamster ovary (CHO) cells to establish active bile acid transport in a non-liver-derived cell model (CHO.asbt). A high-affinity bile acid binder was expressed in McNtcp.24 cells. RESULTS: The tolerance of McNtcp.24 cells to taurine-conjugated bile acids was associated with the stimulation of phosphatidylinositol 3-kinase (PI3K) activity. Treatment of CHO.asbt cells with taurine- and glycine-conjugated bile acids resulted in apoptosis. Unlike in McNtcp.24 cells, PI3K activity was not increased in CHO.asbt cells treated with taurine-conjugated bile acids. High level expression of a bile acid binder did not attenuate bile acid-induced cytotoxicity in McNtcp.24 cells. CONCLUSION: The data suggest that McNtcp.24 cells possess a mechanism that can elaborate distinctive responses to the different classes of bile acids. Additionally, activation of a signaling pathway involving PI3K appears to be the dominant mechanism responsible for the tolerance of McNtcp.24 cells to taurine-conjugated bile acids.

Animals↗

PubMed2001

Vitamin C transport in human lens epithelial cells: evidence for the presence of SVCT2.

Vitamin C [ascorbic acid (AA)] is an important antioxidant present in m M amounts in the aqueous humor. Recently, two specific transporters for vitamin C (SVCT1, SVCT2) have been cloned in the rat and the human. The aim of the present study was to characterize vitamin C transport in an immortalized human lens epithelial cell line (HLE-B3). AA uptake was linear for 120 min in experiments conducted with 14C AA + 40 microM unlabelled AA. Uptake was measured at varying AA concentrations (0.04-1 m M) in Na+-containing and Na+-free buffers for 30 min at 37 degrees C. Effect of potential inhibitors of AA transport was also examined. Presence (or absence) of SVCT1 and SVCT2 was studied by RT-PCR of HLE-B3 poly (A)+ RNA using gene specific primers. Uptake studies revealed that AA uptake was highly Na+-dependent and exhibited saturation. Na+-dependent 14C-AA uptake was strongly inhibited (85-90%) by 10 m M unlabelled AA. Incubation of HLE-B3 cells with cAMP (0.1 m M), cytocholasin B (0.1 m M) and phorbol dibutyrate (1 microM) resulted in partial inhibition (36-51%) of AA uptake. Under similar conditions, D -glucose (10 m M) and staurosporine (0.1 microM) had no effect. RT-PCR showed the presence of SVCT2 while SVCT1 could not be amplified. Exposure to the chemical oxidant tert-butylhydroperoxide (TBH) up-regulated SVCT2 gene expression in HLE-B3 cells. Our data suggest that Na+-dependent transport of AA in normal lens epithelium is most likely mediated by SVCT2 rather than by SVCT1. This transport system may be subject to regulation by oxidant stress and by various second messenger signals.

Antioxidants↗

PubMed2001

Purification and characterization of the enantioselective nitrile hydratase from Rhodococcus equi A4.

The nitrile hydratase from Rhodococcus equi A4 consisted of two kinds of subunits which slightly differed in molecular weight (both approximately 25 kDa) and showed a significant similarity in the N-terminal amino acid sequences to those of the nitrile hydratase from Rhodococcus sp. N-774. The enzyme preferentially hydrated the S-isomers of racemic 2-(2-, 4-methoxyphenyl)propionitrile, 2-(4-chlorophenyl)propionitrile and 2-(6-methoxynaphthyl)propionitrile (naproxennitrile) with E-values of 5-15. The enzyme functioned in the presence of 5-98% (v/v) of different hydrocarbons, alcohols or diisopropyl ether. The addition of 5% (v/v) of n-hexane, n-heptane, isooctane, n-hexadecane, pristane and methanol increased the E-value for the enzymatic hydration of 2-(6-methoxynaphthyl)propionitrile.

Amino Acid Sequence↗

PubMed2001

Basic and applied aspects in the microbial degradation of azo dyes.

Azo dyes are the most important group of synthetic colorants. They are generally considered as xenobiotic compounds that are very recalcitrant against biodegradative processes. Nevertheless, during the last few years it has been demonstrated that several microorganisms are able, under certain environmental conditions, to transform azo dyes to non-colored products or even to completely mineralize them. Thus, various lignolytic fungi were shown to decolorize azo dyes using ligninases, manganese peroxidases or laccases. For some model dyes, the degradative pathways have been investigated and a true mineralization to carbon dioxide has been shown. The bacterial metabolism of azo dyes is initiated in most cases by a reductive cleavage of the azo bond, which results in the formation of (usually colorless) amines. These reductive processes have been described for some aerobic bacteria, which can grow with (rather simple) azo compounds. These specifically adapted microorganisms synthesize true azoreductases, which reductively cleave the azo group in the presence of molecular oxygen. Much more common is the reductive cleavage of azo dyes under anaerobic conditions. These reactions usually occur with rather low specific activities but are extremely unspecific with regard to the organisms involved and the dyes converted. In these unspecific anaerobic processes, low-molecular weight redox mediators (e.g. flavins or quinones) which are enzymatically reduced by the cells (or chemically by bulk reductants in the environment) are very often involved. These reduced mediator compounds reduce the azo group in a purely chemical reaction. The (sulfonated) amines that are formed in the course of these reactions may be degraded aerobically. Therefore, several (laboratory-scale) continuous anaerobic/aerobic processes for the treatment of wastewaters containing azo dyes have recently been described.

Anaerobiosis↗