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Biomedical subjects

A Schmidt

Publications and source records attributed to A Schmidt.

At least 145 records · Page 8Linked to original sources
PubMed2000

[Establishment and evaluation of microdilution assays for the in vitro sensitivity testing of Aspergillus fumigatus].

For the in vitro sensitivity assessment of moulds different methods of micro- and macro-dilution assays as well as agar diffusion assays in different media formulations have been described so far. Until now, no standardized method has been preferred. The aim of the present study is to establish and to evaluate a microdilution assay for the in vitro chemosensitivity testing of Aspergillus fumigatus. This method should show a late onset of superficial growth and sporulation as well as a relative independency of the test inoculum. As reference substances, amphotericin B (CAS 1397-89-3) and 5-fluorocytosine (CAS 2022-85-7), which are both used for therapy of systemic mycoses, have been tested. Both substances show an excellent water solubility in liquid media. Fifty clinical isolates of A. fumigatus were used for the testings. The strains showed a better growth in Isosensitest (ISO)-medium than in Yeast-Nitrogen-Glucose (YNG)-medium. Growth was submers++ during the observation time, adherent to the bottom of the microtiter plate. Superficial growth with sporulation only occurred in a late stage of growth. Only a weak inoculum effect could be observed and the MIC (minimal inhibitory concentration) values determined macroscopically as well as using an ELISA reader showed to be almost comparable with a clearly defined breakpoint for the MIC discrimination. For amphotericin B, lower MIC values were observed in ISO-medium (0.25-2 micrograms/ml; median M = 1 microgram/ml) than in YNG-medium (0.25 microgram/ml; M = 1 microgram/ml). For 5-fluorocytosine, in both media MIC-values of > or = 32 micrograms/ml with a median of 64 micrograms/ml in ISO-medium and 128 micrograms/ml in YNG-medium were observed, respectively. With this test procedure, a standardized chemosensitivity testing can be performed for strains of A. fumigatus by a test system which is relatively easy to handle. These in vitro sensitivity data have to be correlated with clinical data as well as data obtained from animal studies. Only after this assessment final therapeutic consequences should be drawn from these in vitro findings.

Amphotericin B↗
PubMed2000

[Experiences with the alloplastic joint prosthesis of the interphalangeal joint].

The replacement of finger joints, especially of the proximal interphalangeal joint (PIP), remains an unsolved problem. Long-term results of conventional reconstructive procedures as well as previously available artificial joint implants have been disappointing. In a controlled study, 12 PIP-joints were replaced by a new type of total endoprosthesis as an alternative to joint fusion. The cementless prosthesis is unhinged and consists of metal joint surfaces. After a follow-up of 18 months, implantation of this metal prosthesis resulted in almost complete pain relief and an active range of movement of 58 degrees. The absolute gain in mobility, however, was only 6 degrees. A swan-neck deformity was found in nine out of 12 cases but corrective surgery was not required. The proximal half of the implant had to be exchanged in two cases due to loosening. All patients were satisfied with the result. The disparity between subjective acceptance by the patients, who clearly prefer joint replacement to fusion, and objective results demonstrates the necessity for further development in this field. The type of prosthesis used in this study seems to be a useful baseline tool which could be turned into a ingenious PIP-joint replacement by further development aiming at reduced abrasion, increased initial stability, a more individual configuration, to name just a few goals.

Equipment Failure Analysis↗
PubMed2000

beta-Cyanoalanine synthase is a mitochondrial cysteine synthase-like protein in spinach and Arabidopsis.

beta-Cyano-alanine synthase (CAS; EC 4.4.1.9) plays an important role in cyanide metabolism in plants. Although the enzymatic activity of beta-cyano-Ala synthase has been detected in a variety of plants, no cDNA or gene has been identified so far. We hypothesized that the mitochondrial cysteine synthase (CS; EC 4.2.99. 8) isoform, Bsas3, could actually be identical to CAS in spinach (Spinacia oleracea) and Arabidopsis. An Arabidopsis expressed sequence tag database was searched for putative Bsas3 homologs and four new CS-like isoforms, ARAth;Bsas1;1, ARAth;Bsas3;1, ARAth;Bsas4;1, and ARAth;Bsas4;2, were identified in the process. ARAth;Bsas3;1 protein was homologous to the mitochondrial SPIol;Bsas3;1 isoform from spinach, whereas ARAth;Bsas4;1 and ARAth;Bsas4;2 proteins defined a new class within the CS-like proteins family. In contrast to spinach SPIol;Bsas1;1 and SPIol;Bsas2;1 recombinant proteins, spinach SPIol;Bsas3;1 and Arabidopsis ARAth;Bsas3;1 recombinant proteins exhibited preferred substrate specificities for the CAS reaction rather than for the CS reaction, which identified these Bsas3 isoforms as CAS. Immunoblot studies supported this conclusion. This is the first report of the identification of CAS synthase-encoding cDNAs in a living organism. A new nomenclature for CS-like proteins in plants is also proposed.

Arabidopsis↗
PubMed2000

Molecular diversity of plaques of epithelial-adhering junctions.

In biochemical and immunocytochemical comparisons of adhering junctions of different epithelia, we have observed differences in molecular composition not only between the intermediate filament-attached desmosomes and the actin filaments-anchoring adherens junctions but also between desmosomes of different tissues and of different strata in the same stratified epithelium. In addition we now report cell type-specific differences of molecular composition and immunoreactivity in both desmosomes and adherens junctions of certain simple epithelia. Whereas the zonula adhaerens of human intestinal and colonic epithelial cells, and of carcinomas derived therefrom, contains the additional armadillo-type plaque protein ARVCF, this protein has not been detected in the zonula adhaerens of hepatocytes. Similarly, plakophilin 3 is present in the desmosomal plaques of intestinal and colonic cells but appears to be absent from the hepatocytic desmosomes. We suggest that these profound compositional differences in the junctions of related simple epithelia are correlated to functional differences of the specific type of epithelium.

Adherens Junctions↗
PubMed2000

Coronary arterial stent patency: assessment with electron-beam CT.

PURPOSE: To evaluate electron-beam computed tomography (CT) for stent localization and noninvasive assessment of stent patency in patients with coronary arterial stents and coronary bypass stents. MATERIALS AND METHODS: CT in the single-section volume mode was performed in 202 patients with 321 coronary arterial stents in 221 vessels to localize the stents. Patency was evaluated in the multisection flow mode with an intravenous bolus injection of contrast material. All electron-beam CT images were reviewed by an observer who had no knowledge of the coronary angiographic results. Electron-beam CT findings were then compared with coronary angiographic findings. RESULTS: The stents could be visualized and related to the coronary arterial segments in 216 of 221 vessels with electron-beam CT. Of the 221 vessels, 207 were correctly evaluated with electron-beam CT. Compared with coronary angiography, electron-beam CT permitted the detection of 18 of 23 high-grade stenoses (sensitivity, 78%) and correctly depicted the absence of high-grade stenoses in 189 of 193 vessels with stents (specificity, 98%). Altogether, 18 stenoses were detected correctly at electron-beam CT; the interpretation was false-positive in four vessels (positive predictive value, 82% [18/22 vessels]) and false-negative in five (negative predictive value, 97% [189/194 vessels]). CONCLUSION: Electron-beam CT may be helpful in localizing intracoronary stents and assessing stent patency noninvasively to delay the intervals between catheterizations in an increasing number of patients.

Adult↗
PubMed2000

A pulsatile flow model for in vitro quantitative evaluation of prosthetic valve regurgitation.

A pulsatile pressure-flow model was developed for in vitro quantitative color Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors controlled by a computer. The piston was connected to acrylic chambers designed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventricular" chamber, a prosthetic heart valve was placed at the inflow connection with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reservoir arranged to mimic the peripheral circulation. The flow model was filled with a 0.25% corn starch/water suspension to improve Doppler imaging. A continuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosthetic valves. This pulsatile flow model was able to generate pressure and flow in the physiological human range, with independent adjustment of pulse duration and rate as well as of stroke volume. This model mimics flow profiles observed in patients with regurgitant prosthetic valves.

Blood Pressure↗
PubMed2000

Analysis of Wilms tumor gene (WT1) expression in acute leukemia patients with special reference to the differential diagnosis between eosinophilic leukemia and idiopathic hypereosinophilic syndromes.

Continuous Wilms' tumor gene (WT1) expression is a typical feature of leukemic blasts in AML, ALL, and blast crisis CML patients. It is easily detectable by a variety of RT-PCR protocols, which differ mainly in their sensitivity. The nuclear WT1 protein can be found in blasts of approximately 50-60% of acute leukemia patients at diagnosis. Conversely, WT1 is only transiently expressed in normal hemopoiesis. Early CD34+ hemopoietic progenitors express WT1, whereas no WT1 mRNA transcripts can be found in mature blood cells and differentiation-induced committed CD34- progenitors. As a powerful complementary diagnostic tool, testing for WT1 expression can be helpful to discriminate between eosinophilic leukemia (EoL) patients and patients with idiopathic hypereosinophilic syndromes. Conflicting data about the usefulness of testing for WT1 expression to monitor minimal residual disease (MRD) in treated leukemia patients will be discussed. Finally, research strategies to circumvent shortcomings in detecting leukemia-associated WT1 expression will be outlined.

Acute Disease↗
PubMed1999

Cloning and expression of cynomolgus monkey (Macaca fascicularis) gonadotropins luteinizing hormone and follicle-stimulating hormone and identification of two polymorphic sites in the luteinizing hormone beta subunit.

The genes encoding the cynomolgus monkey gonadotropin subunits, alpha, follicle-stimulating hormone (FSH) beta and luteinizing hormone (LH) beta, were cloned by reverse transcriptase polymerase chain reaction (RT-PCR) using pituitary RNA. The predicted amino acid sequences displayed 82, 96 and 87% identity to human subunit sequences, respectively. Northern blot hybridization of monkey tissues revealed pituitary specific transcripts of 1.0 and 0.6 kb for the alpha and LHbeta subunit, respectively, and two bands of 1.8 and 0.65 kb for the FSHbeta. Upon sequencing LHbeta cDNAs from different monkeys, two polymorphic sites were detected, resulting in the amino acid transitions Ser32Thr and His60Arg. Restriction analysis revealed different homo- and heterozygous combinations of the polymorphic sites indicating linkage dysequilibrium. Transient co-expression of the alpha subunit together with the FSHbeta or LHbeta subunit in COS7 and CHO cells resulted in secretion of in vitro bioactive hormones. This work represents a further step towards production of recombinant monkey LH and FSH which can be used in a homologous experimental setting in the cynomolgus monkey.

Amino Acid Sequence↗
PubMed1999

Starvation induces vacuolar targeting and degradation of the tryptophan permease in yeast.

In Saccharomyces cerevisiae, amino acid permeases are divided into two classes. One class, represented by the general amino acid permease GAP1, contains permeases regulated in response to the nitrogen source. The other class, including the high affinity tryptophan permease, TAT2, consists of the so-called constitutive permeases. We show that TAT2 is regulated at the level of protein stability. In exponentially growing cells, TAT2 is in the plasma membrane and also accumulates in internal compartments of the secretory pathway. Upon nutrient deprivation or rapamycin treatment, TAT2 is transported to and degraded in the vacuole. The ubiquitination machinery and lysine residues within the NH(2)-terminal 31 amino acids of TAT2 mediate ubiquitination and degradation of the permease. Starvation-induced degradation of internal TAT2 is blocked in sec18, sec23, pep12, and vps27 mutants, but not in sec4, end4, and apg1 mutants, suggesting that, upon nutrient limitation, internal TAT2 is diverted from the late secretory pathway to the vacuolar pathway. Furthermore, our results suggest that TAT2 stability and sorting are controlled by the TOR signaling pathway, and regulated inversely to that of GAP1.

Amino Acid Sequence↗
PubMed1999

Transcription control and neuronal differentiation by agents that activate the LXR nuclear receptor family.

LXR and PPAR receptors belong to the nuclear receptor superfamily of transcriptional activating factors. Using ligand-dependent transcription assays, we found that 5-tetradecyloxy-2-furancarboxylic acid (TOFA) transactivates chimeric receptors composed of the glucocorticoid receptor DNA binding domain and the ligand binding regions of PPARalpha, PPARbeta (NUC-1) and LXRbeta (NER) receptors. In the same assays, ligands for PPARs (oleic acid, WY-14643 and L-631,033) and LXRs (hydroxycholesterols) maintain their respective receptor selectivity. TOFA and hydroxycholesterols also stimulate transcription from a minimal fibrinogen promoter that is under the control of AP-1 or NF-kappaB transcription factor binding sites. In addition to their effects on transcription, these LXRbeta activators induce neuronal differentiation in rat pheochromocytoma cells. TOFA and the natural LXR agonist, 22 (R)-hydroxycholesterol, stimulate neurite outgrowth in 55 and 28% of cells, respectively. No neurite outgrowth was induced by the related 22(S)-hydroxycholesterol, which does not activate the LXR family. These results suggest that the hydroxycholesterol signaling pathway has a complex effect on transcription that mediates the activity of TOFA and hydroxycholesterol on neuronal differentiation in pheochromocytoma cells.

Animals↗
PubMed1999

Endophilin I mediates synaptic vesicle formation by transfer of arachidonate to lysophosphatidic acid.

Endophilin I is a presynaptic protein of unknown function that binds to dynamin, a GTPase that is implicated in endocytosis and recycling of synaptic vesicles. Here we show that endophilin I is essential for the formation of synaptic-like microvesicles (SLMVs) from the plasma membrane. Endophilin I exhibits lysophosphatidic acid acyl transferase (LPAAT) activity, and endophilin-I-mediated SLMV formation requires the transfer of the unsaturated fatty acid arachidonate to lysophosphatidic acid, converting it to phosphatidic acid. A deletion mutant lacking the SH3 domain through which endophilin I interacts with dynamin still exhibits LPAAT activity but no longer mediates SLMV formation. These results indicate that endophilin I may induce negative membrane curvature by converting an inverted-cone-shaped lipid to a cone-shaped lipid in the cytoplasmic leaflet of the bilayer. We propose that, through this action, endophilin I works with dynamin to mediate synaptic vesicle invagination from the plasma membrane and fission.

Acyl Coenzyme A↗
PubMed1999

The presence of two DnaA-binding sequences is required for an efficient interaction of the Escherichia coli DnaA protein with each particular weak DnaA box region.

Using an electron microscopic method for visualizing interactions of the Escherichia coli DnaA protein with weak DnaA-binding DNA sequences, we found that DnaA binds effectively to two separated weak DnaA box regions located on the same DNA fragment. As expected, no DnaA-DNA interactions were detected when both DnaA box regions were mutagenized to the sequence totally incapable of binding DnaA. However, when only one of these two regions was mutagenized, the lack of interactions between DnaA and DNA was observed not only at the scrambled DnaA box but also at the second weak DnaA box region. These results indicate that for the efficient binding of DnaA to a weak DnaA box region, the presence of at least two such DNA sequences is necessary. Our finding also suggests that binding of DnaA protein to weak DnaA box sequences may be cooperative. In addition, we found that DnaA-mediated transcription termination in vivo requires two DnaA boxes, one of them is a weak one. It seems, therefore, that some mechanisms of regulation of transcription and DNA replication by DnaA, that involve interactions of DnaA with weak DnaA boxes, may be more complicated than initially proposed.

Bacterial Proteins↗