The purpose of this study was to investigate the characteristics of transport of endogenous nucleosides into cardiac tissue from coronary circulation. The study was performed on the isolated perfused guinea pig heart, using the rapid paired tracers single-pass technique. The maximal cellular uptake (U(max)) and total cellular uptake (U(tot)) of adenosine, deoxyadenosine, thymidine, uridine, and cytidine were determined. The cellular uptake of adenosine was significantly higher than the cellular uptake of other studied nucleosides. To elucidate the mechanisms of nucleoside transport, competition studies were performed and the influence of S-(p-nitrobenzyl)-6-thioinosine (NBTI) and sodium ion absence on U(max) and U(tot) was investigated. Self- and cross-inhibition studies indicated the saturable mechanism of nucleosides transport into cardiac tissue and the involvement of different transport mechanisms for purine and pyrimidine nucleosides. The study also showed that both equilibrative-sensitive (es) and sodium-dependent transport were responsible for adenosine and thymidine cellular uptake.

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This pa per pres ents the re sults of an ex am i na tion of func tion sta bil ity of high-volt age asynchron ous mo tors ex posed to am bi ent strain caused by com bined neu tron and gamma ra di ation. This prob lem ap pears in prac tice when a high-volt age asyn chron ous mo tor is used in nuclear power plants where it can be ex posed to this type of am bi ent strain. The fail ure of the en gine's op er a tion un der such con di tions may have un ex pected con se quences. As more than 50 % of fail ure (mal func tion) of high-volt age asyn chron ous mo tors is caused by dam age to stator in su la tion, the fo cus of the pa per was on test ing the ef fects of com bined neu tron and gamma ra di a tion on stator in su la tion. The tests were car ried out un der well-con trolled lab ora tory con di tions on sam ples taken from both new and used fac tory coil wind ings. Two-layer sam ples were used to re cord par tial dis charge thresh old volt age and break down volt age. By com par ing the ex per i men tally ob tained re sults with the ap pli ca ble math e mat i cal-sta tis ti cal pro ce dure, an es ti mate was made of the ag ing ac cel er a tion of stator in su la tion and the time du ra tion of re li able op er a tion of high-volt age asyn chron ous mo tor was de ter mined by lifetime ex po nent.

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