Suppression of the transformed phenotype of breast cancer by tropomyosin-1

Gap junctional intercellular communication (GJIC) is thought to play a crucial role in cell differentiation. Small gap junction plaques are frequently associated with tight junction strands in hepatocytes, suggesting that gap junctions may be closely related to the role of tight junctions in the establishment of cell polarity. To examine the exact role of gap junctions in regulating tight junctions, we transfected connexin 32 (Cx32), Cx26, or Cx43 cDNAs into immortalized mouse hepatocytes derived from Cx32-deficient mice and examined the expression and function of the endogenous tight junction molecules. In transient wild-type Cx32 transfectants, immunocytochemistry revealed that endogenous occludin was in part localized at cell borders, where it was colocalized with Cx32, whereas neither was detected in parental cells. In Cx32 null hepatocytes transfected with Cx32 truncated at position 220 (R220stop), wild-type Cx26, or wild-type Cx43 cDNAs, occludin was not detected at cell borders. In stable wild-type Cx32 transfectants, occludin, claudin-1, and ZO-1 mRNAs and proteins were significantly increased compared to parental cells and all of the proteins were colocalized with Cx32 at cell borders. Treatment with a GJIC blocker, 18 beta-glycyrrhetinic acid, resulted in decreases of occludin and claudin-1 at cell borders in the stable transfectants. The induction of tight junction proteins in the stable transfectants was accompanied by an increase in both fence and barrier functions of tight junctions. Furthermore, in the stable transfectants, circumferencial actin filaments were also increased without a change of actin protein. These results indicate that Cx32 formation and/or Cx32-mediated intercellular communication may participate in the formation of functional tight junctions and actin organization.     

A first record of Phlebotominae from Argentinean Patagonia (Diptera: Psychodidae: Phlebotominae)

A species of the Lutzomyia oswaldoi group is recorded from the Valcheta stream basin, Somuncura plateau, Patagonia. It represents the World southermost record of a species of Phlebotominae, apparently supporting the hypothesis about the relictual character of several components of the Somuncura plateau biota, particularly for those species belonging to the Paranaense lineages.     

Origin of human immunodeficiency virus type 1 quasispecies emerging after antiretroviral treatment interruption in patients with therapeutic failure

The emergence of antiretroviral (ARV) drug-resistant human immunodeficiency virus type 1 (HIV-1) quasispecies is a major cause of treatment failure. These variants are usually replaced by drug-sensitive ones when the selective pressure of the drugs is removed, as the former have reduced fitness in a drug-free environment. This was the rationale for the design of structured ARV treatment interruption (STI) studies for the management of HIV-1 patients with treatment failure. We have studied the origin of drug-sensitive HIV-1 quasispecies emerging after STI in patients with treatment failure due to ARV drug resistance. Plasma and peripheral blood mononuclear cell samples were obtained the day of treatment interruption (day 0) and 30 and 60 days afterwards. HIV-1 pol and env were partially amplified, cloned, and sequenced. At day 60 drug-resistant variants were replaced by completely or partially sensitive quasispecies. Phylogenetic analyses of pol revealed that drug-sensitive variants emerging after STI were not related to their immediate temporal ancestors but formed a separate cluster, demonstrating that STI leads to the recrudescence and reemergence of a sequestrated viral population rather than leading to the back mutation of drug-resistant forms. No evidence for concomitant changes in viral tropism was seen, as deduced from env sequences. This study demonstrates the important role that the reemergence of quasispecies plays in HIV-1 population dynamics and points out the difficulties that may be found when recycling ARV therapies with patients with treatment failure.     

Citrate synthase and pyruvate kinase activities during early life stages of the shrimp Farfantepenaeus paulensis (Crustacea,Decapoda, Penaeidae): effects of development and temperature

Energy metabolism in early life stages of the shrimp Farfantepenaeus paulensis subjected to temperature reduction (26 and 20 °C) was determined using the activities of citrate synthase (CS) and pyruvate kinase (PK). At both temperatures, weight-specific activity of CS decreased throughout the ontogenetic development from protozoea II (PZ II) to postlarva XII–XIV (PL XII–XIV). PK activity reached a pronounced peak in PL V–VI, followed by a further decrease in PL XII–XIV. Temperature reduction produced variation in oxygen consumption rates (QO₂), ammonia–N excretion and in enzyme activities. Ammonia–N excretion was higher at 20 °C in mysis III (M III), PL V–VI and PL XII–XIV, resulting in substantially lower O:N ratios in these stages. QO₂ was increased in protozoea II (PZ II) and mysis I (M I) at 26 °C, while no difference in QO₂ was detected in the subsequent stages at either temperature. This fact coincided with higher CS and PK activities in M III, PL V–VI and PL XII–XIV at 20 °C compared with 26 °C. Regressions between individual enzyme activities and dry weight exhibited slope values of 0.85–0.92 for CS and 1.1–1.2 for PK and temperature reduction was reflected by higher slope values at 20 than at 26 °C for both enzymes. Weight-specific CS activity was positively correlated with QO₂ at 20 and 26 °C, and may thus be used as an indicator of aerobic metabolic rate throughout the early stages of F. paulensis. The variation in enzyme activities is discussed in relation to possible metabolic adaptations during specific ontogenetic events of the F. paulensis life cycle. Here, the catalytic efficiency of energy-metabolism enzymes was reflected in ontogenetic shifts in behaviour such as larval settlement and the adoption of a benthic existence in early postlarvae. In most cases, enhanced enzyme activities appeared to counteract negative effects of reduced temperature.     

Effects of temperature on the respiration rates and the kinetics of citrate synthase in two species of Idotea (Isopoda, Crustacea)

The two species of isopods, Idotea baltica (Pallas) and Idotea emarginata (Fabricius), co-occur frequently near Helgoland, North Sea, occupying different ecological niches. Respiration rates and kinetic properties of citrate synthase (CS) were compared in these species in order to identify possible mechanisms of temperature adaptation. Specimens were acclimated to 5 and 15 degrees C prior to further investigations. Respiration rates were measured under normoxic conditions at 5, 10 and 15 degrees C. CS was partly purified chromatographically and influences of temperature, pH, substrate saturation and ATP-concentration on enzyme activity were examined. In both species, rising temperatures led to linearly increasing oxygen consumption, with estimated Q10 values between 3.2 and 4.2. Only I. baltica showed an effect of short term acclimation: warm adapted animals had always higher respiration rates than cold adapted ones. In I. emarginata, the acclimation temperature had no effect on oxygen consumption. Furthermore, its CS slightly indicates higher affinity to oxaloacetic acid when specimens were adapted to 15 degrees C compared to those maintained at 5 degrees C. Any effect of the experimental temperature on CS in I. baltica was negligible. The results are discussed in view of the different habitats occupied by the species compared.     

Uptake and washout of borocaptate sodium and borono-phenylalanine in cultured melanoma cells: a multi-nuclear NMR study

The cellular uptake and washout of the two principal boron neutron capture therapy (BNCT) agents, borocaptate sodium (BSH) and borono-phenylalanine (BPA), were monitored on-line, noninvasively, using nuclear magnetic resonance (NMR) spectroscopy. The uptake and washout of inorganic borate (B(i)) was also followed for comparison. M2R mouse melanoma cells grown on polystyrene microspheres were perfused inside the NMR sample tube. (11)B NMR was used to detect the presence of B(i), BSH and BPA, and (19)F NMR was applied to detect fluorinated BPA ((19)F-BPA). The results revealed chemical modifications of BSH due to spontaneous formation of the borocaptate dimer, BSSB, in the culture medium. BPA readily formed a complex with glucose contained in the culture medium but was also converted in the cells to a yet unidentified compound in a reaction that probably involves the hydrolysis of BPA and the release of B(i). The cellular accumulation ratio for BPA was significantly higher than 1 and was also significantly higher than that for BSH. On the other hand, the cellular retention time observed for BSH was much longer than for BPA, indicating a strong trapping of BSH in cells.     

Doxorubicin-induced ovarian toxicity

Background  

Young cancer patients may occasionally face infertility and premature gonadal failure. Apart from its direct effect on follicles and oocytes, chemotherapy may induce ovarian toxicity via an impact on the entire ovary. The role of doxorubicin in potential ovarian failure remains obscure. Our intention was to elucidate doxorubicin-related toxicity within ovaries.