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A Schweiger

Publications and source records attributed to A Schweiger.

At least 37 records · Page 2Linked to original sources
PubMed1998

Determination of the optimum mixing time for a mixture of lactose and colloidal silicon dioxide.

The homogeneity of a mixture of colloidal silicon dioxide (CSD) and lactose is examined by quantifying the dependence of the CSD content on the mixing time. CSD concentration is determined photometrically as a blue silica-molybdic complex. Its deviation from the expected content is taken to characterize the mixture quality and the optimum mixing time. The conformity of this result with the flow properties of the same mixture is studied by measuring the dependence of the angle of repose on the mixing time.

Colloids↗
PubMed1997

Enzyme-linked immunosorbent assay for the detection of total cathepsin H in human tissue cytosols and sera.

An enzyme-linked immunosorbent assay (ELISA) was constructed for the determination of total human cathepsin H concentration in clinical samples. Utilising monoclonal and polyclonal antibodies, raised to human liver cathepsin H, the assay is able to detect a mature protein, a precursor molecule and enzyme-inhibitor complexes. The test system permits sensitive and reliable detection of analyte either in tissue cytosols or in sera. The detection limit is 2 ng/ml (n = 10, mean of zero standard +/- 3 SD). The average recovery of cathepsin H, added to the low content samples, was 95.3% +/- 1.8%. The within-run and between-run coefficient of variance (CV) varied from 2.3% to 8.9% and 12.7% to 16.4%, respectively, indicating satisfactory reproducibility of the method. The level of cathepsin H was defined in tissue cytosols of human heart, muscle and kidney and in sera from 30 healthy individuals. Additionally, cathepsin H was measured in sera from 55 patients with primary skin melanoma and from 42 patients with metastatic melanoma. The mean cathepsin H level was significantly higher for both groups of patients compared to normal sera level, being highest for metastatic melanoma patients.

Animals↗
PubMed1997

Cathepsins B, H, and L and their inhibitors stefin A and cystatin C in sera of melanoma patients.

The levels of cathepsins (Cats) B, H, and L and their inhibitors stefin A and cystatin C were determined in the sera of 43 patients with metastatic melanoma, in 54 patients with treated cutaneous melanoma with no evidence of metastatic disease, and in 30 healthy blood donors, using quantitative ELISAs. The levels of Cats B and H and cystatin C were significantly higher within the group of metastatic melanoma patients compared with the healthy controls. The median Cat B was 4.8 versus 3.6 ng/ml (P < 0.013), the median Cat H was 13.7 versus 4.9 ng/ml (P < 0.0001), and the median cystatin C was 470 versus 320 ng/ml (P < 0.02). Cat H was also significantly increased within the group of melanoma patients with no metastasis, with a median of 9.6 ng/ml. Cat B was found to correlate with Cat L (r = 0.36; P < 0.02) and cystatin C (r = 0.41; P < 0.008). The serum level of Cat H was significantly increased in patients showing no response to the chemoimmunotherapy as compared to the level in responders. Metastatic melanoma patients with high contents of Cat B and Cat H experienced significantly shorter overall survival rates than the patients with low levels of each enzyme (Cat B: P < 0.003 and relative risk, 2.5; Cat H: P < 0.006 and relative risk, 2.4, using medians as cutoff values). The other potential factors for prognosis for this group of patients revealed moderate (histological type and age) or no (tumor thickness, sex, and lymph node metastasis) prognostic significance. Similarly, no difference in survival was found for stefin A, cystatin C, and Cat L. These results suggest that the serum levels of Cats B and H could serve as prognostic factors for patients with advanced melanoma.

Adult↗
PubMed1996

Classification of tyrosine kinases from Dictyostelium discoideum with two distinct, complete or incomplete catalytic domains.

Two new kinases of Dictyostelium discoideum were identified by screening of a (lambda)gt11 expression library with a phosphotyrosine specific antibody. Amino-acid sequences derived from cDNA and genomic clones indicate that DPYK3 is a protein of 150 kDa and DPYK4, a protein of 75 kDa. The C-terminal fragments of each protein were produced in Escherichia coli and shown to be autocatalytically phosphorylated at tyrosine residues. A common feature of these kinases is the presence of two different sequence stretches in tandem that are related to kinase catalytic domains. The sequence relationships of DPYK3 and 4 to other protein kinases, and the positions of their catalytic domain sequences within the phylogenetic tree of protein kinases were analysed. Domains I of both kinases and domain II of DPYK3 constitute, together with the catalytic domains of two previously described tyrosine kinases of D. discoideum, a branch of their own, separate from the tyrosine kinase domains in sensu strictu. Domain II in DPYK4 is found on a different branch close to serine/threonine kinases.

Amino Acid Sequence↗
PubMed1995

Stress-induced tyrosine phosphorylation of actin in Dictyostelium cells and localization of the phosphorylation site to tyrosine-53 adjacent to the DNase I binding loop.

Actin is known to be phosphorylated at tyrosine, serine, or threonine residues in various cells. In cells of Dictyostelium discoideum, a rise in the tyrosine phosphorylation of actin is observed in response to ATP depletion. An actin fraction rich in phosphotyrosine was obtained by chromatography on the weak anion exchanger Mono-P. Mass spectrometry and amino acid sequencing of protease cleavage products indicated that a single tyrosine residue was phosphorylated. Localization of this residue to position 53 of the actin sequence attributed the modification to a site that is critical for the capability of actin to polymerize. Induction of the tyrosine phosphorylation by heat shock and Cd2+ ions indicates that this modification of actin is implicated in the response of Dictyostelium cells to stress.

Actins↗
PubMed1994

Strong increase in the tyrosine phosphorylation of actin upon inhibition of oxidative phosphorylation: correlation with reversible rearrangements in the actin skeleton of Dictyostelium cells.

When oxidative phosphorylation is inhibited in cells of Dictyostelium discoideum, the phosphorylation of tyrosine residues on actin is strongly increased. This increase is fully reversible. Under the same conditions the amoeboid cells undergo a series of shape changes. Within three minutes the pseudopods are withdrawn and replaced by cell surface blebs. Subsequently, the cells are rounding up to become immobile. In parallel with the changes in cell shape, the distribution of actin filaments is grossly altered within the cells. The cortical network of actin filaments of normal cells is broken down, and the F-actin forms large, irregular clusters deep within the cytoplasm. In these clusters the actin is associated with myosin II and with the heterodimeric F-actin capping protein cap32/34. After restoration of oxidative phosphorylation the actin returns within less than four minutes to its normal cortical position. A causal relationship between tyrosine phosphorylation and changes in the distribution of actin remains to be established. The rearrangements in the actin system that result from the inhibition of oxidative phosphorylation indicate that the organisation of this system and its maintenance in a functional state depend on the continuous supply of energy by ATP.

Actins↗
PubMed1992

Stage-specific tyrosine phosphorylation of actin in Dictyostelium discoideum cells.

A 45 kDa protein in Dictyostelium discoideum cells that was recognized by a phosphotyrosine-specific antibody was identified by its binding activity to DNase I and its 2D-electrophoretic behavior as actin. The reactivity of actin with the antibody was transiently enhanced for about 30 minutes shortly after starving cells were reintroduced into nutrient medium. This effect indicates a modification of actin that is regulated under physiological conditions. A similar effect was obtained when growing cells were treated with phenylarsine oxide (PAO), an inhibitor of phosphotyrosine phosphatases. This effect was reversed and the cells fully recovered upon addition of the PAO antagonist 2,3-dimercaptopropanol. Starved cells did not show this enhancement of antibody labelling, which indicates that the response to PAO depends on the developmental stage. Phosphorylated amino acid residues were identified after in vivo labelling with [32P]phosphate in the presence of PAO. Part of the radioactivity in the actin band was recovered as phosphotyrosine, another part as phosphoserine. PAO caused the cells to form elongated blebs, to round up and finally to become immobilized. Fluorescence labelling with phalloidin of cells that were fixed at different times of PAO treatment revealed a progressive decrease in the staining for actin filaments and showed that these alterations in cytoskeleton organization were readily reversible, in accordance with the reversal of tyrosine phosphorylation at actin.

Actins↗
PubMed1991

The macrophage response to bacteria: flow of L-arginine through the nitric oxide and urea pathways and induction of tumoricidal activity.

The consequences of the interaction of heat-killed bacteria and lipopolysaccharide (LPS) with a pure population of bone marrow-derived mononuclear phagocytes (BMMø) were investigated, utilizing changes in the flow of L-arginine and expression of tumoricidal activity as parameters of macrophage (mø) function. Gram negative bacteria and LPS proved potent in inducing the flow of L-arginine through the nitric oxide and the urea pathways but were mostly poor in eliciting tumoricidal activity. Gram positive bacteria affected the metabolism of L-arginine only little but were often efficient in triggering tumoricidal activity. The findings show that the mø response to bacteria, which may determine the outcome of their interaction with the host, may differ considerably depending on the type of bacteria.

Animals↗
PubMed1991

Individual and family characteristics of middle class adolescents hospitalized for alcohol and other drug abuse.

The frequency of alcohol and drug use, abuse and severity of dependence, and personality and family characteristics in 280 female and male hospitalized adolescents in treatment for chemical dependence and 120 middle class adolescents were examined. A MANOVA showed that parents' drug and alcohol use was a main effect, increasing frequency of use and severity of dependence upon alcohol and drugs in both groups of adolescents. Sexual and physical abuse studied in the patient group also functioned as a main effect. Patients reported significantly less family interests, and participation in intellectual, cultural and social activities, but more control than the comparison group. It was concluded that adolescent alcohol and other drug abuse is part of a biopsychosocial syndrome of problem behavior, which includes the problem behavior of parents and the interacting family unit.

Alcoholism↗
PubMed1990

Extremely thermostable D-glyceraldehyde-3-phosphate dehydrogenase from the eubacterium Thermotoga maritima.

D-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Thermotoga maritima, a hyperthermophilic eubacterium, has been isolated in pure crystalline form. The enzyme is a homotetramer with a subunit molecular mass of 37 kDa. The sedimentation coefficient of the native enzyme is 7.3 X 10(-13)s, the isoelectric point is 4.6, and the specific absorption coefficient A1%, 1cm 280nm = 8.4. The enzyme shows extreme thermal stability: differential scanning calorimetry yields a transition temperature (Tm) of 109 degrees C for the NAD-saturated enzyme. Thermal deactivation occurs at T greater than 90 degrees C. The physicochemical characteristics of the enzyme suggest that its gross structure must be very similar to the structure of GAPDHs from mesophilic sources. The amino acid composition does not confirm the known "traffic rules" of thermal adaptation, apart from the Lys----Arg exchange. One reactive and at least two buried SH groups can be titrated with 5,5'-dithiobis(2-nitrobenzoate). The highly reactive SH group is probably the active-site cysteine residue common to all known GAPDHs. The activation energy of the glyceraldehyde 3-phosphate oxidation reaction decreases with increasing temperature. This functional behavior can be correlated with the temperature-dependent changes of both the intrinsic fluorescence and the near-UV circular dichroism; both indicate a temperature-dependent structural reorganization of the enzyme. Hydrogen-deuterium exchange reveals significantly increased rigidity of the thermophilic enzyme if compared to mesophilic GAPDHs at 25 degrees C, thus indicating that the conformational flexibility is similar at the corresponding physiological temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Phosphotyrosine-containing proteins in Dictyostelium discoideum.

Phosphotyrosine-containing proteins in Dictyostelium discoideum were detected by immunoblot analysis and immunoprecipitation using a monoclonal anti-phosphotyrosine antibody. The iodinated antibody recognized on bots a cluster of 205-220 kDa polypeptides and bands of 107 and 60 kDa. The 107 and 60 kDa polypeptides and, in addition, a 82 kDa one became phosphorylated on tyrosine when the immunoprecipitate was incubated with [gamma-32P]ATP. In preparations from differentiating cells the intensity of the label was increased in the 60 kDa band and decreased in the 107 and 205-220 kDa bands.

Antibodies, Monoclonal↗