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Biomedical subjects

M Klein

Publications and source records attributed to M Klein.

At least 325 records · Page 18Linked to original sources
PubMed1994

Isolation and characterization of a Bacillus subtilis secA mutant allele conferring resistance to sodium azide.

A mutation has been isolated in the Bacillus subtilis secA gene (secA10) which allows cell growth and residual protein translocation in the presence of 1.5 mM sodium azide. Besides conferring resistance to sodium azide, the corresponding SecA10 mutant protein, in which glutamic acid at position 338 has been changed to glycine, seems to possess a secretion defect even in the absence of azide. In addition, the secA10 mutant protein was found to be recessive to wild-type secA with regard to azide resistance. Our results strongly suggest that, like the situation in Escherichia coli, the B. subtilis SecA protein is a main target for the lethal action of sodium azide.

Azides↗
PubMed1994

Analysis of the primary structure and post-translational modifications of the Schistosoma mansoni antigen Smp28 by electrospray mass spectrometry.

The Schistosoma mansoni glutathione-S-transferase with an apparent molecular mass of 28 kDa, Smp28, has a blocked N-terminus which has been elucidated with the aid of the cDNA sequence combined with mass spectrometry and amino acid composition analysis of the N-terminal tryptic peptide. The blocked N-terminal tryptic peptide (m/z 695.8) contained an equimolar ratio of E, G, H, A, I and K3 upon amino acid composition analysis in agreement with its expected sequence AGEHIK, and showed a delta m = +41.7 Da compared to the predicted mass, which is consistent with the N-terminal alanine being acetylated (delta m = +42.0 Da). The mass of the complete molecule (23,744.5 +/- 3.3 Da) determined by electrospray mass spectrometry showed a further mass increase of 14 Da with respect to Smp28 containing an N-acetylated alanine. This result is consistent with one of the seven methionines being present as a methionine sulfoxide in ca. 90% of the Smp28 molecules in this preparation. Tryptic mapping of Smp28 showed five of the seven methionines to be partially oxidized by mass spectrometry. This is indicative of the ease with which this modification occurs. Two minor components were detected along with the intact molecule, corresponding to modified forms of the molecule, originating from reaction of the only cysteine residue either with itself forming a covalent dimer or with glutathione. On-line liquid chromatography-mass spectrometry has been compared with the off-line complete tryptic map of Smp28 confirming 97% of the primary structure in less than 2 h.

Amino Acid Sequence↗
PubMed1994

DNA ploidy in primary fallopian-tube carcinoma using image cytometry.

Determination of DNA ploidy in 61 samples of primary Fallopian-tube carcinoma (FTC) by use of image cytometry is presented. Of these samples, 48 showed an aneuploid DNA content. Patients with euploid DNA content showed a median survival time of 33.8 months compared to 24.5 months for aneuploid cases. A high incidence of aneuploid tumors was consistently observed among all FIGO stages and in all groups of histologic grading. However, no correlation between ploidy and FIGO stage or histologic grading could be demonstrated. This observation could be regarded as a marker for the high aggressiveness of FTC which has been repeatedly described in the past.

Adult↗
PubMed1994

Single-stranded regions in the genome of the Ectocarpus siliculosus virus.

The double-stranded DNA genome of the Ectocarpus siliculosus virus, EsV, is interrupted by numerous single-stranded gaps. We have investigated whether single-stranded regions occur at random or at specific sites. A brief treatment with a single-strand-specific endonuclease dissected the genome into two large fragments, but more extensive treatment produced a spectrum of nuclease-resistant fragments, mainly 10 to 70 kb in size. Native EsV DNA was also used as a substrate for gap-filling DNA synthesis. Restriction analysis revealed that essentially all of the 60 or more SacI restriction fragments became labeled but a few fragments were more intensely labeled than others. The EsV genome may contain a few extended single-stranded regions at fixed sites in addition to numerous single-stranded regions probably occurring at random and varying sites.

Chromosome Mapping↗
PubMed1994

Roles of disulfide bonds in recombinant human interleukin 6 conformation.

Human IL-6 has two disulfide bonds linking Cys45 to Cys51 and Cys74 to Cys84, respectively. Previous site-directed mutagenesis studies have demonstrated that the Cys74-Cys84 bond is essential for full biological and receptor binding activities. To address the structural importance of these disulfide bonds in the formation and stabilization of IL-6 secondary and tertiary structures, we have generated a panel of disulfide bond-deficient rIL-6 analogs both by chemical reduction and alkylation as well as by site-directed mutagenesis. Conformational changes affecting these rIL-6 analogs were probed by circular dichroism spectroscopy, as well as reactivity with monoclonal antibodies, and correlated with changes in biological activities. We have shown that the first disulfide bridge (Cys45-Cys51) is highly sensitive to reduction and, therefore, more solvent-exposed or less thermodynamically stable. Contrary to previous reports, this bridge contributes, although minimally, to the full biological activity of the cytokine. However, no significant changes in secondary or tertiary structures were observed upon removal of this bond. In marked contrast, analogs lacking the disulfide bridge between Cys74 and Cys84 exhibited as little as 0.5% and 0.05% wild-type biological and receptor binding activities, respectively. These dramatic changes correlated with a slight reduction in alpha-helical content and a decreased reactivity with the neutralizing monoclonal antibody mAb8 which recognizes a conformational epitope associated with the active site. Our results suggest that the second disulfide bridge plays a critical role in maintaining the spatial relationship between the putative IL-6 A and D helices.

Alkylation↗
PubMed1994

[Lead poisoning in pregnancy].

Endemic areas of lead poisoning have recently been rediscovered raising an important public health problem, particularly for pregnant women and their offspring. Theoretically, pregnant women can no longer be exposed to occupational sources with the application of public health regulations but other sources including water contamination, wall paint, industrial wastes and automobile exhaust fumes cannot be ignored. The placental barrier is permeable to free serum lead and levels in cord blood reaches 5 to 10% of the maternal blood level. In addition, lead may be released from maternal bone reserves during pregnancy and thus become a major source of intoxication for the fetus. Lead content in fetal organs increases with gestational age and may affect the nervous system and calcium dependent organs. Moderate lead levels of 100 micrograms/L can inhibit fetal haeme and erythropoiesis. Besides the classical signs of lead poisoning, pregnant women risk spontaneous abortion and increased blood pressure. Manifestations in the fetus and newborn include prematurity, fetal hypotrophy and malformations. Other manifestations are not seen until several years after birth and include retarded mental development and muscular and behaviour disorders. Diagnosis is based on screening tests which should be used in cases of suspected accidental or environmental intoxication. Tests should include assay of zinc protoporphyrins and aminolevulinic acid dehydrase. A search for the source of the contamination should be undertaken when blood levels above 250 micrograms/L are observed. Treatment with metal chelators is not recommendable (except in extreme life-threatening cases) during pregnancy due to their teratogenic effect. Prevention is the only adequate treatment.

Bone and Bones↗
PubMed1994

Effects of haloperidol and reduced haloperidol on binding to sigma sites.

The s.c. administration of a single dose of 0.1 mg/kg of reduced haloperidol to guinea pigs produced a marked inhibition of the binding of [3H]dextromethorphan and [3H]3-(3-hydroxyphenyl)-N-(n-propyl)piperidine ([3H](+)-3-PPP) to brain. The inhibition was still evident 10 days later, and it was accompanied by residual brain levels of reduced haloperidol, and much lower levels of haloperidol. Scatchard and computer-assisted analysis demonstrated that the inhibition was due to a reduction in the number of binding sites without changes in the affinity. In the rat, haloperidol and reduced haloperidol also produced a rapid inhibition of binding to sigma sites. Interestingly, the brain of the reduced haloperidol-treated rats contained both haloperidol and reduced haloperidol, but the levels of reduced haloperidol in the haloperidol-treated rats were undetectable. However, the inhibition observed was of comparable magnitude, indicating that the haloperidol remaining in the brain is also inhibitory. In vitro experiments showed that the inhibition produced by haloperidol and reduced haloperidol was apparently competitive, but when brain membranes were preincubated with either drug, the inhibition was noncompetitive. By contrast, the inhibition produced by dextromethorphan was always competitive. Moreover, the inhibition produced by haloperidol and reduced haloperidol could not be reversed by washing. This investigation strongly suggests that the inhibition observed after the administration of haloperidol or reduced haloperidol is not a classic agonist-induced receptor down-regulation. The results indicated that the inhibition produced is a complex phenomenon, and suggest the formation of a slowly reversible or irreversible complex with reduced haloperidol or haloperidol.

Animals↗
PubMed1994

Distinct effects of thioredoxin and antioxidants on the activation of transcription factors NF-kappa B and AP-1.

The transcription factors NF-kappa B and AP-1 have been implicated in the inducible expression of a variety of genes involved in responses to oxidative stress and cellular defense mechanisms. Here, we report that thioredoxin, an important cellular protein oxidoreductase with antioxidant activity, exerts different effects on the activation of NF-kappa B and AP-1. Transient expression or exogenous application of thioredoxin resulted in a dose-dependent inhibition of NF-kappa B activity, as demonstrated in gel shift and transactivation experiments. AP-1-dependent transactivation, in contrast was strongly enhanced by thioredoxin. A similar increase of AP-1 activity was also observed with other, structurally unrelated antioxidants such as pyrrolidine dithiocarbamate and butylated hydroxyanisole, indicating that the thioredoxin-induced increase of AP-1 activation was indeed based on an antioxidant effect. Moreover, the stimulatory effect on AP-1 activity was found to involve de novo transcription of the c-jun and c-fos components but to be independent of protein kinase C activation. These results suggest that thioredoxin plays an important role in the regulation of transcriptional processes and oppositely affects NF-kappa B and AP-1 activation.

Animals↗
PubMed1994

[Tumor-associated myasthenia gravis and myasthenia syndrome].

Out of 700 patients operated on account of myasthenia gravis, 144 cases with tumours (20.57%) were evaluated. Classification took place in five groups: 1. Thymoma and myasthenia gravis; 2. Thymic cysts and myasthenia gravis; 3. Thymoma and latent myasthenia gravis; 4. Paraneoplastic myasthenia-syndrome; 5. Thymoma, myasthenia gravis and myasthenia-syndrome. Up-to-date classification of thymomas is: epithelioma with minimal, marked or overwhelming lymphatic reaction. Dark-cell and light-cell epitheliomas equally associate with myasthenia. Concerning prognosis, location of the tumour to thymic capsula, surrounding, perithymic tissue is more important than the histologic structure of the tumour. Previous examination in the case of mediastinal tumour can reveal latent, mild myasthenia which was not known till that time. Term of postthymectomic myasthenia can be excluded on the basis of these examinations. Heterogeneity is considerable among myasthenia-syndromes concerning both histopathologic and clinical features. There is a double indication of operation in the case of myasthenia with tumour: the tumour and the disease. Good results can be achieved in myasthenia gravis associated with tumour by means of total operation, post-operative radiation and by other up-to-date therapeutical procedures. The results are hardly beyond those of non-tumours myasthenia gravis.

Adolescent↗
PubMed1994

Prognostic factors in primary fallopian tube carcinoma. Austrian Cooperative Study Group for Fallopian Tube Carcinoma.

A retrospective nationwide evaluation of primary fallopian tube carcinomas for a period of 10 years (1980-1990) was performed to evaluate the prognostic impact of various factors. Sixty-six cases were investigated for the prognostic influence of estrogen (ER) and progesterone (PgR) status, mitotic activity, degree of nuclear anaplasia, and inflammatory reaction. ER and PgR receptors were detected by immunohistochemistry from paraffin sections. Forty-two percent were PgR-positive and 26% were ER-positive. However, no correlation of steroid receptors with survival could be found. Ninety-two percent of all tumors showed a moderate and high degree of nuclear anaplasia and only 8% showed a low degree of nuclear anaplasia. Thirty-four (52%) samples from all patients revealed low mitotic activity compared to 32 (48%) with an intermediate and high mitotic rate. Twenty-four (37%) tissue samples showed a positive inflammatory reaction which correlated with a significantly better outcome compared with tumors without this feature. This finding was also confirmed in multivariate analysis as an independent prognostic factor.

Fallopian Tube Neoplasms↗
PubMed1994

Lymphogenous metastasis in the primary carcinoma of the fallopian tube.

The bad prognosis of primary Fallopian tube carcinoma (FTC) is mostly ascribed to early lymphogenous metastasis. Yet, there is a lack of information on the tumor size at which lymph node metastasis must be expected to occur. Our study was therefore designed to correlate the anatomopathologic substratum and the histologic results with the lymph node status. Data were obtained from 21 women who received primary surgery, during which additional total pelvic and para-aortic lymphadenectomy was performed as well. The "surgical" staging was compared to the final clinical staging after histologic inspection of the lymph nodes according to the FIGO classification. Lymph node metastases never occurred as long as the tumor was confined to the tube (stage I). Lymphogenous dissemination set in only after further, local expansion of the tumor, involving the ovaries, the peritoneum, or the uterus (surgical stage II); 3 of the 7 patients of surgical stage II had to be reclassified to stage III because of manifest lymph node metastases. After the onset of intra-abdominal or general metastasis (stage IV), lymph node metastases occurred significantly more often (P = 0.048). Due to the specific lymphatic drainage, lymphogenous metastasis must be expected to spread as far as to the para-aortic region even in the early stages. Highly differentiated tumors (G I) do not disseminate into the lymphatic system, not even in advanced stages, whereas anaplastic tumors (G II and III) metastasize relatively early. As soon as metastasis has occurred, prognosis of life diminishes markedly, but not significantly (49 versus 24 months, P = 0.19). Correct FTC-staging is obtained only on the basis of pelvic and para-aortic lymphadenectomy.

Adolescent↗
PubMed1994

Evaluation of adjuvant therapy after surgery for primary carcinoma of the fallopian tube.

OBJECTIVE: To evaluate the impact of postoperative therapy (chemotherapy vs. irradiation) on overall survival. DESIGN: A nationwide retrospective analysis. SETTING: Hanusch-Krankenhaus, Department of Gynaecology, SUBJECTS: 115 patients with histologically proved primary carcinoma of the Fallopian tube: 49 received six treatment cycles of a cis-platinum regimen (group I), 24 patients were treated by full irradiation using 50 Gray minimum (group II). The two groups had a similar distribution of stage I and II; in the more advanced stages chemotherapy was the predominant method of treatment. RESULTS: The five-year survival rate was 53% for women receiving irradiation as against 27% for those given cis-platinum. If the analysis was restricted to those patients with comparable stage I and stage II lesions, the p-value (0.07) was of borderline significance. There was no advantage in adding abdominal to pelvic irradiation (P = 0.62). CONCLUSIONS: Stage I and stage II carcinoma is probably better treated postoperatively by radiotherapy than chemotherapy. Chemotherapy may have more therapeutic potential in patients with more advanced lesions.

Adult↗
PubMed1994

Primary fallopian tube carcinoma--a retrospective survey of 51 cases. Austrian Cooperative Study Group for Fallopian Tube Carcinoma.

OBJECTIVE: To evaluate retrospectively the importance of invasion beyond the basement membrane on overall survival in Fallopian tube carcinoma and its influence on the necessity of postoperative adjuvant therapy (stage 0 vs. stage I). DESIGN: In a nationwide analysis the data of 51 patients were evaluated. The participating departments provided the study center with histologic specimens. A re-staging was done according to the FIGO-classification for Fallopian tube carcinomas. Stage 0 patients received no further postoperative therapy, in stage I patients were divided in 2 groups to evaluate the impact of postoperative adjuvant therapy (chemotherapy vs. irradiation). RESULTS: Patients of stage 0 had a significantly better prognosis than patients of stage I (p = 0.035). Stage I patients treated by irradiation showed a significantly better prognosis than patients treated by chemotherapy (p = 0.017). CONCLUSION: Tumour penetration through the basement membrane causes prognosis to deteriorate significantly (5-year survival rate about 50% in stage I). Postoperative therapy is thus indicated with stage I disease. Irradiation seems to give better results than chemotherapy.

Adenocarcinoma↗
PubMed1994

Preoperative and postoperative CA-125 serum levels in primary fallopian tube carcinoma.

Levels of CA-125 were determined pre- and postoperatively in 13 patients with fallopian tube cancer. Values before surgery were significantly higher (Median 1220 IU/ml, 90-5000 IU/ml) compared with postoperative levels (Median 194 IU/ml, 67-880 IU/ml) (P = 0.0052). Correlation analysis with FIGO stage and grading failed to show any statistical significance, but a trend for a positive correlation with FIGO stage and preoperative values could be observed. The CA-125 antigen is expressed by fallopian tube carcinoma and should therefore be used in diagnosis and follow-up.

Adenocarcinoma, Mucinous↗
PubMed1994

Prognostic value of neurohumoral activation in patients with an acute myocardial infarction: effect of captopril.

OBJECTIVES: This study attempted to evaluate whether neurohumoral activation at the time of hospital discharge in postinfarction patients helps to predict long-term prognosis and whether long-term therapy with the angiotensin-converting enzyme inhibitor captopril modifies this relation. BACKGROUND: Neurohumoral activation persists at the time of hospital discharge in a large number of postinfarction patients. The Survival and Ventricular Enlargement (SAVE) study demonstrated that the angiotensin-converting enzyme inhibitor captopril improves survival and decreases the development of severe heart failure in patients with left ventricular dysfunction (left ventricular ejection fraction < or = 40%) but no overt postinfarction heart failure. METHODS: In 534 patients in the SAVE study, plasma neurohormone levels were measured a mean of 12 days after infarction. Patients were then randomized to receive captopril or placebo and were followed up for a mean (+/- SD) of 38 +/- 6 months (range 24 to 55). The association between activation of plasma neurohormones at baseline and subsequent cardiovascular mortality or the development of heart failure was assessed with and without adjustment for other important prognostic factors. RESULTS: By univariate analysis, activation of plasma renin activity and aldosterone, norepinephrine, atrial natriuretic peptide and arginine vasopressin levels were related to subsequent cardiovascular events, whereas epinephrine and dopamine levels were not. By multivariate analysis, only plasma renin activity (relative risk 1.6, 95% confidence interval [CI] 1.0 to 2.5) and atrial natriuretic peptide (relative risk 2.2, 95% CI 1.3 to 3.8) were independently predictive of cardiovascular mortality, whereas the other neurohormones were not. Only plasma renin activity and aldosterone, atrial natriuretic peptide and arginine vasopressin were independent predictors of the combined end points of cardiovascular mortality, development of severe heart failure or recurrent myocardial infarction. Except for 1-year cardiovascular mortality, the use of captopril did not significantly modify these relations. CONCLUSIONS: Neurohumoral activation at the time of hospital discharge in postinfarction patients is an independent sign of poor prognosis. This is particularly true for plasma renin activity and atrial natriuretic peptide. Except for 1-year cardiovascular mortality, captopril does not significantly modify these relations.

Aged↗
PubMed1994

Synaptic augmentation by 5-HT at rested Aplysia sensorimotor synapses: independence of action potential prolongation.

Short-term augmentation of synaptic transmission at sensory neuron synapses of Aplysia contributes to behavioral sensitization and is one of the current models for a cellular mechanism of learning. This neuromodulatory process, mediated at least in part by the facilitatory neurotransmitter serotonin (5-HT) acting through cAMP, has been thought to result largely from prolongation of the sensory neuron action potential (AP). The quantitative contribution of AP prolongation to synaptic augmentation was examined using a new culture preparation that is favorable for controlling the voltage at the presynaptic terminals. Preventing AP prolongation by using unvarying voltage-clamp commands in place of triggered APs did not reduce augmentation significantly, and pharmacological prolongation of APs caused by a high concentration of 5-HT led to a negligible increase in the synaptic response. Together with earlier evidence against the involvement of changes in Ca2+ current, these results suggest that synaptic augmentation may result from modulation of steps in the secretory process that lie distal to the flow of ion currents across the nerve terminal membrane.

Action Potentials↗