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Biomedical subjects

A Iu Semenov

Publications and source records attributed to A Iu Semenov.

7 recordsLinked to original sources
PubMed2001

[Radical surgical treatment of Barrett's esophagus].

In the light of modern scientific knowledge, pathogenesis of Barrette's esophagus (BE) is presented as an integral neoplastic process. Indications to operation and policy of radical surgical treatment in BE, including in combined esophageal diseases (burn and peptic strictures, reflux esophagitis, short esophagus) were developed. From 1990 to 2000 radical operations were performed in 14 patients (11 males, 3 females) with BE. Mean age was 54.1 years. About 80% patients had clinical signs of reflux esophagitis at the moment of hospitalization. In all the patients the diagnosis of BE was verified in microscopic examination of operative material. 4 patients with cylindrical metaplasia associated with ulcers and esophageal peptic strictures were operated, 3 patients--with epithelium dysplasia, 7 patients--with adenocarcinoma. All the patients underwent extirpation of thoracic portion of esophagus with one-stage plasty with isoperistaltic gastric tube, supplemented with mediastinal and abdominal lymphodissection in cancer. Affection of the regional lymph nodes was revealed in 43% patients with esophageal adenocarcinoma. 50% patients had complications in postoperative period. There were no cases of hospital lethality. The expansion of indications for early surgical treatment of BE at the stage of meta-, and dysplasia, before adenocarcinoma development, is thought valid.

Adult↗
PubMed1980

[Reversible electric current generation by reconstituted mitochondrial transhydrogenase].

A direct measurement of the electrogenic activity of purified mitochondrial transhydrogenase has been carried out. For this purpose beef heart transhydrogenase was isolated and reconstituted with phospholipids to form proteoliposomes. The transhydrogenase proteoliposomes were incorporated into a membrane filter impregnated with a decane solution of phospholipids. It was shown that the addition of substrates of either forward (NADPH and NAD+) or reverse (NADH and NADP+) transhydrogenase reaction gives rise to formation of electric potential difference across the proteoliposome-treated membrane filter. The electric vector depends on the direction of the reaction. The proteoliposome-supplemented compartment charges negatively in the case of the reverse one. The addition of the reaction products after substrate equalizes the potentials. The transhydrogenase-treated membrane retains the ability to the transhydrogenase-linked electrogenesis after removal of an excess of non-incorporated proteoliposomes.

Animals↗
PubMedDate not supplied

[Electrogenic reactions in cytochrome bf-complexes in a model system].

By using the direct electrometric technique, the flash-induced generation of the difference in electrical potentials in hybrid proteoliposomes containing photosystem 1 and cytochrome bf complexes from cyanobacteria Synechocystis sp. PCC 6803 was studied. It was shown that the primary donor P700 in photosystem I and cytochrome f are predominantly localized near the outer surface of the proteoliposomal membrane, which made it possible to study for the first time electrogenic reactions of cytochrome bf complexes in a model system. In the presence of decyl plastoquinol and cytochrome c6, besides the fast electrogenic phase determined by the separation of charges in photosystem I, additional electrogenic phases in the submillisecond and millisecond ranges were observed. These phases were partially depressed in the presence of the inhibitor of the plastoquinone reductase site NQNO and fully disappeared after the addition of the inhibitor of the plastoquinol oxidase site stigmatellin. A possible mechanism of the electrogenic reactions in cytochrome bf complexes was considered.

Cyanobacteria↗
PubMedDate not supplied

[Electrogenic reactions in the photosystem I].

The processes of electron transfer in cyanobacterial photosystem I (PS I) and photoelectric methods of the studies were reviewed. Particular emphasis was placed on structural and kinetic characteristics of the electron transport chain. The electrogenicity in PS I complex and its interaction with natural donors (plastocyanin, cytochrome c6), natural acceptors (ferredoxin, flavodoxin), and artificial acceptors and donors (methyl viologen and other redox dyes) were studied. On the basis of photoelectric measurements and the X-ray structural data, the operating dielectric constants in the vicinity of charge carriers in situ were calculated. The profile of distribution of the dielectric constant along the PS I pigment-protein complex (from plastocyanin or cytochrome c6 through the chlorophyll dimer P700 to the acceptor complex) was estimated, and possible mechanisms of correlation between the local dielectric constant and the electron transfer rate constant in the corresponding segment of the chain were discussed.

Cyanobacteria↗
PubMedDate not supplied

[Kinetics of the generation of a photo-induced electric potential in chromatophores of photosynthetizing bacteria].

Flash-induced formation of an electric potential difference (delta psi) was monitored by a direct method in chromatophores associated with the collodion phospholipid membrane. In Rhodospirillum rubrum and Rhodopseudomonas sphaeriodes chromatophores, the kinetics of delta psi generation exhibit fast (tau less than or equal to 0.3 microseconds) and slow (tau congruent to 200 microseconds) phases, the latter observed in the presence of exogenous quinones. Comparison of the kinetic and potentiometric characteristics of the process with those of electron transport reactions suggests that the fast phase of delta psi rise is due to charge separation between the primary electron donor, P870, and primary electron acceptor QIFe; the slow phase, which is inhibited by o-phenanthroline, is due to electron donation from QIFe to the secondary acceptor, quinone QII. The kinetics of delta psi decay include components arising form the recombination of primary separated charges (tau congruent to 30 ms) and from the passive discharge of the membrane (tau congruent to 400 ms; tau congruent to 1400 ms). From a redox titration of the photo-induced electric signal and the photo-induced absorption changes of P870 at different pH meanings, the value of pK for the primary acceptor FeQI was found to be 7.4 in Rps. sphaeroides chromatophores. In Chromatium minutissimum, a phase ( tau congruent to 20 microseconds) was observed in addition to those seen in Rps. sphaeroids and R. rubrum which was explained by the reduction of P890+ from the high potential cytochrome c555. Possible distribution of the electron transport components in the chromatophore membrane are discussed.

Bacterial Chromatophores↗