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M Stolz

Publications and source records attributed to M Stolz.

28 records · Page 2Linked to original sources
PubMed1996

Purification, metal cofactor, N-terminal sequence and subunit composition of a 5-aminolevulinic acid dehydratase from the unicellular green alga Scenedesmus obliquus, mutant C-2A'.

5-Aminolevulinic acid dehydratase was purified to apparent homogeneity from Scenedesmus obliquus, mutant C-2A', starting with serial affinity chromatography according to Wang et al., followed by separation on DEAE-Cellulose DE 52, TSKgel Toyopearl HW-55 and FPLC on Mono Q. The enzyme was purified 117-fold compared with the initial crude soluble enzyme preparation and showed a final specific activity of 9.17 microkat/kg protein at pH 8.2 at a total recovery of 7%. Mg2+ was determined to be the metal cofactor of the enzyme. It can, to a certain extent, be substituted by other divalent cations. From the purified enzyme the first 15 amino acids of the N-terminus could be determined, showing a moderate similarity to 5-aminolevulinic acid dehydratases from spinach, pea, Escherichia coli and yeast. The molecular mass of the native protein was determined by gel filtration to be 282+/-5 kDa. 42+/-1 kDa were ascertained for the subunit size by SDS/PAGE. These investigations, supported by electron microscopy, revealed that the enzyme from Scenedesmus consists of six subunits arranged in a six-membered ring. Additionally, there is some evidence that two of the rings form a sandwich-like complex.

Amino Acid Sequence↗
PubMed1996

Identification of two distinctly localized mitochondrial creatine kinase isoenzymes in spermatozoa.

The creatine kinase (CK) isoenzyme system is essential for motility in rooster and sea urchin sperm. In the present study, biochemical characterization as well as immunofluorescence and confocal laser microscopy with highly specific antibodies against various chicken CK isoenzymes revealed that cytosolic brain-type CK isoenzyme (B-CK) is the only CK isoenzyme in rooster seminal plasma, while three isoenzymes, cytosolic B-CK, sarcomeric mitochondrial CK (Mib-CK), and a variant of ubiquitous Mi-CK ('Mia-CK variant'), are found in rooster spermatozoa. These three isoenzymes are localized in different regions of the sperm cell. B-CK and Mib-CK were localized along the entire sperm tail and in the mitochondria-rich midpiece, respectively. The 'Mia-CK variant', on the other hand, was found predominantly at the head-midpiece boundary, in a non-uniform manner in the midpiece itself and, surprisingly, at the distal end of the sperm tail as well as at the acrosome. Several lines of evidence show that the 'Mia-CK variant' shares some characteristics with purified Mia-CK from chicken brain, but also displays distinctive features. This is the first evidence for two different Mi-CK isoenzymes occurring in one cell and, additionally, for the co-expression of Mib-CK and cytosolic brain-type B-CK in the same cell. The relevance of these findings for sperm physiology and energetics is discussed.

Animals↗
PubMed1995

Adenosine triphosphate and arachidonic acid stimulate glycogenolysis in primary cultures of mouse cerebral cortical astrocytes.

Adenosine triphosphate (ATP) promotes glycogenolysis in primary cultures of mouse cerebral cortical astrocytes with an EC50 of 1.5 microM. A pharmacological analysis indicates an involvement of purinergic P2Y receptors in this action of ATP. Application of either arachidonic acid (AA), or certain unsaturated fatty acids, also results in glycogen breakdown. The EC50 of AA is approximately 50 microM. Thus ATP and AA can be added to the list of neuroactive agents that control glycogen levels in astrocytes, which includes noradrenaline, vasoactive intestinal peptide (VIP), adenosine and histamine.

Adenosine Triphosphate↗
PubMed1994

Molecular and pharmacological characterization of the human CCKB receptor.

The human cholecystokinin B (CCKB) receptor has been isolated from a human temporal cortex cDNA library. Transient transfection of the receptor into COS-M6 cells resulted in high specific binding of 125I-sulphated CCK-8 labelled with Bolton and Hunter Reagent (KD = 31 pM). Competition experiments yielded the expected CCKB receptor ligand binding profile for agonists and antagonists. Similar results were obtained in human small cell lung carcinoma cells, which express an endogenous CCKB receptor. Extensive functional characterization of the receptor was performed in stably transfected HeLa cells using intracellular calcium imaging and microphysiometry techniques. Molecular analysis of the human CCKB receptor using Southern blotting of genomic DNA suggests the presence of a single gene for the CCKB receptor with no closely related homologues. This was confirmed by the polymerase chain reaction cloning of identical receptor coding sequences from human small cell lung carcinoma cells and human gastric enterochromaffin-like cell-oma (ECLoma) tissue.

Animals↗
PubMed1993

The DNA-binding properties of an artificial 42-residue polypeptide derived from a natural repressor.

Bacteriophage 434 repressor recognizes the operator sequences ACAAG and ACAAT. As the same or similar sequences occur in the enhancer region of HIV-1, 434 repressor was a potential HIV enhancer-binding protein. We found that the interaction of the DNA-binding domain of 434 repressor with a 57-bp HIV enhancer DNA was very weak whereas a 42-residue construct, comprising the recognition helix and four copies of a positively charged segment of the repressor, bound strongly. The results of footprint and cell-free in vitro transcription studies showed that the 42-residue peptide bound preferably to the enhancer region of HIV-1 and acted as an artificial repressor. Replacement of an essential glutamine of the recognition helix by glutamic acid resulted in a partial shift of the sequence specificity of the 42-residue peptide.

Amino Acid Sequence↗
PubMed1990

[Doppler ultrasound flow measurement of fetal and uteroplacental blood vessels. Study of a normal population in the 2d half of pregnancy].

Weekly Dopplersonography measurements were performed on the fetal aorta abdominalis, the umbilical artery, the fetal carotid artery and the uterine arcuate artery from the 20th to the 41st weeks of gestation, mean and maximum blood flow velocities were measured, as well as the resistance index. The mean values calculated from 20 cases per week were translated into standard graphical representations serving as a criterion for the assessment of pathological pregnancies. The vessels were examined as to their value for a screening programme of fetal circulation. A sample curve of a severe placental insufficiency showed significant deviations from the standard curves.

Arteries↗
PubMed1988

[Simultaneous radiochemotherapy of locally advanced stage T4 breast cancer].

The local efficacy of simultaneous radiochemotherapy was tested in 17 women with 18 carcinomas of the breast in stage T4 only. Treatment was conducted for a period of 6 months with 6 courses of drug therapy (A + E) coordinated simultaneously with 6 courses of radiotherapy. In 72% of the cases we found considerable (greater than 80%) or complete (100%) regression of the tumour as a result of this combined treatment. The median survival time is 35 months.

Aged↗
PubMedDate not supplied

Purification, characterization and N-terminal sequence of phosphoserine aminotransferase from the green alga Scenedesmus obliquus, mutant C-2 A'.

Phosphoserine aminotransferase (EC 2.6.1.52), an enzyme of the "phosphorylated pathway" leading to the formation of serine, was purified from Scenedesmus obliquus, mutant C-2 A'. Purification started from the soluble supernatant of a crude cell homogenate and included different affinity and DEAE chromatographic techniques, as well as gel filtration. The purified phosphoserine aminotransferase was enriched 1537-fold and identified to be a homodimer with subunit molecular masses of 40 kDa, each. The absorption spectrum is consistent with the presence of pyridoxal-5-phosphate as cofactor. From the purified enzyme 18 amino acids of the N-terminus could be determined, showing at least 67% homology with the serC gene encoding phosphoserine aminotransferases from bacterial organisms.

Amino Acid Sequence↗
PubMedDate not supplied

[The importance of pulsed Doppler sonography for prenatal diagnosis of placental insufficiency--studies of 198 patients].

Doppler sonographic measurements of the fetal aorta and the carotid artery were performed on 198 pregnant patients having been diagnosed with a placental insufficiency. A relationship between them and fetal as well as non-fetal factors was examined. For the fetal factors minus difference in weight of birth and perinatal morbidity there could be established a definite correlation with corresponding resistance-index (RI) of the examined vessels. The criteria for the fetal outcome Apgar-note and pH-value of the cord blood didn't show absolutely equal changes with a deteriorated blood perfusion, what might be due to the management of birth as well as it indicates the close correlation of these values with the course of birth. Among the non-fetal factors there could be shown close relationships between the duration of pregnancy as well as age and the values of resistance-indices. While the ones, mentioned first, decreased in an almost linear relationship with RI-deterioration, did the fetal circulatory situation ameliorate with an increasing maternal age. Possible factors of influence, especially on the duration of pregnancy as well as the relationship between the maternal age and the fetal condition of perfusion were discussed. Pulsed doppler sonographic measurement is an efficient step in diagnosing a suspected placental insufficiency and has an outstanding value in an early recognition of possible dangers for the fetus.

Aorta, Abdominal↗