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S Heimann

Publications and source records attributed to S Heimann.

6 recordsLinked to original sources
PubMed2000

Movement of the Rieske iron-sulfur protein in the p-side bulk aqueous phase: effect of lumenal viscosity on redox reactions of the cytochrome b6f complex.

Based on the atomic structures of the mitochondrial cytochrome bc(1) complex, it has been proposed that the soluble domain of the [2Fe-2S] Rieske iron-sulfur protein (ISP) must rotate by ca. 60 degrees and translate through an appreciable distance between two binding sites, proximal to cytochrome c(1) and to the lumen-side quinol binding site. Such motional freedom implies that the electron-transfer rate should be affected by the lumenal viscosity. The flash-induced oxidation of cytochrome f, the chloroplast analogue of cytochrome c(1), was found to be inhibited reversibly by increased lumenal viscosity, as was the subsequent reduction of both cytochrome b(6) and cytochrome f. The rates of these three redox reactions correlated inversely with lumenal viscosity over a viscosity range of 1-10 cP. Reduction of cytochrome b(6) and cytochrome f was not concerted. The rate of cytochrome f reduction was observed to be approximately half that of cytochrome b(6) regardless of the actual viscosity, implying that the path length traversed by the ISP in reduction of cytochrome f is twice that of cytochrome b(6). This suggests that upon initiation of electron transfer by a light flash, cytochrome b(6) reduction requires movement of reduced ISP from an initial position predominantly proximal to cytochrome f, apparently favored by the reduced ISP, to the quinol binding site at which the oxidant-induced reduction of cytochrome b(6) is initiated. Subsequent reduction of cytochrome f requires the additional movement of the ISP back to a site proximal to cytochromef. There is no discernible viscosity dependence for cytochrome b(6) reduction under oxidizing conditions, presumably because the oxidized ISP preferentially binds proximal to the quinone binding niche. The dependence of the cytochrome redox reaction on ambient viscosity implies that the tethered diffusional motion of the ISP is part of the rate limitation for charge transfer through the b(6)f complex.

Chloroplasts↗
PubMed1999

Low-grade metaplastic carcinoma of the thymus.

AIMS: Five cases of a characteristic low-grade thymic epithelial tumour are described that we suggest calling metaplastic carcinoma of the thymus. METHODS AND RESULTS: The patients' ages ranged from 44 to 71 (mean 56.2) years. Four of the patients were male. Three of five tumours showed invasion into mediastinal fat or pleura but, otherwise, all were well circumscribed. No metastases were present. Histologically, the tumours showed a biphasic pattern with solid carcinomatous areas merging gradually with a spindle cell component. Lymphocytes were rare. Cytological atypia and mitotic activity were variable in the solid areas, but slight or absent in the spindle cell component. On immunohistochemistry, the tumours showed expression of cytokeratin, vimentin and/or epithelial membrane antigen, both in the carcinomatous and spindle cell components. In two cases, actin expression was also present in both components. In one case, chromogranin, S100 protein, glial fibrillary acidic protein and neuron-specific enolase were expressed in at least some cells of both components. None of the patients had myasthenia gravis. All patients are alive without evidence of recurrence or metastasis. CONCLUSION: Metaplastic carcinoma of the thymus is a distinct clinicopathological entity that should be distinguished from the usually benign medullary thymomas and from the clinically aggressive carcinosarcomas and sarcomatoid carcinomas.

Aged↗
PubMed1998

Two distinct states of the thylakoid bf complex.

Under normal physiological conditions the state of the cyt bf complex is characterized by rapid reoxidation kinetics of cyt b-563 following flash-illumination. It is known that these kinetics are dramatically slowed down under oxidizing conditions. Here we show that this slow-down of cyt b-563 oxidation is the consequence of a relatively slow (half-time of several minutes) transformation of the cyt bf complex into a distinctly different state (termed state-s). Reversal to the normal state requires strong reductive treatment or light-induced electron transport. The results are in line with a recent model of functional cyt bf dimers [Cramer et al., Annu. Rev. Plant Physiol. Plant Mol. Biol. 47 (1996), 477-5081, if it is assumed that state-s reflects the monomeric state of the bf complex.

Chloroplasts↗
PubMed1991

Group comparison of serum ethinyl estradiol, SHBG and CBG levels in 83 women using two low-dose combination oral contraceptives for three months.

Serum ethinyl estradiol (EE2), sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) concentrations were studied in healthy young women randomly allocated to one of two low-dose combination oral contraceptives containing 30 micrograms EE2 and either 75 micrograms gestodene (F) or 150 micrograms desogestrel (M) per unit. There was either no (formerly non-pill users) or one (pill users) wash-out cycle before the study started with a pill-free pretreatment cycle in which the hormone status and basal SHBG and CBG levels were measured. Treatment was for three months. During treatment cycles 1 and 3, there were three test days each. Seven serum samples were obtained up to four hours and one sample 24 hours after intake of the first, tenth and the last (21st) pill. Additional samples were taken prior to morning ingestion of pills 5 and 15. For each individual and each test day, a representative serum pool has been constructed for SHBG and CBG analysis. EE2 concentrations were analyzed in all individual samples by means of a specific and sensitive RIA using anti-EE2-6 beta-CMO-BSA antiserum. Area under the curves (AUC) up to 4 and 24 hours, Cmax and tmax were evaluated and compared between the two treatment groups (n = 40 for F, n = 43 for M). SHBG and CBG concentrations were measured using commercially available immunoassay kits. Groups were large enough to detect a difference in group means of 75% of one standard deviation (alpha = 0.05, 1-beta = 0.9) of target variables, which is equivalent to 28 pg EE2/ml for Cmax, 69 pg.h.ml-1 for AUCEE2 0-4h, 257 pg.h.ml-1 for AUCEE2 0-24h, 39 nmol/l SHBG and 13.4 micrograms CBG/ml. Results clearly demonstrate that there were no differences between the two treatment groups in any of the target variables at any of the six test days distributed over a three-month period. Mean SHBG and CBG pretreatment levels of about 70 nmol/l and 37 micrograms/ml, respectively, increased to about 210 nmol/l and 88 micrograms/ml during the first treatment cycle and to about 230 nmol/l and 93 micrograms/ml during the third treatment cycle. Whereas the time of maximum EE2 serum levels did not differ significantly between test days, Cmax, AUCEE2 0-4h and AUCEE2 0-24h values increased by 30-35% or 40-50%, respectively, when test days 10 and 21 were compared to test day 1. Similar results were found for the third treatment cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

[Transitional homes as a special form of rehabilitation of psychiatric patients].

Transitional residences are of particular importance among the rehabilitative facilities for the mentally ill that had been called for by the Psychiatry Enquete. Their primary objective is to enable clients cope with (relatively) self-reliant living. Along with achievement, or restoration, of working capacity and its consolidation through (part-time) work, emotional growth, self-assertion, and social skills are to be developed. In view of practical implementation of the theoretical concept outlined in the Psychiatry Enquete, and based on their long years of experience in the field, the authors have drafted guidelines for meaningful professional work in a transitional setting, in view of overcoming recurrent initial difficulties and living up to the high goals envisaged. Client selection and careperson qualification are indispensable prerequisites in the sequenced provision of rehabilitative care, directed both at the vocational and leisure domain and the personal growth of the clients.

Adolescent↗