Recombination,cryptic clades and neutral molecular divergence of the microcystin synthetase (<Emphasis Type="Italic">mcy</Emphasis>) genes of toxic cyanobacterium <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

Background  

The water-bloom-forming cyanobacterium Microcystis aeruginosa is a known producer of various kinds of toxic and bioactive chemicals. Of these, hepatotoxic cyclic heptapeptides microcystins have been studied most intensively due to increasing concerns for human health risks and environmental damage. More than 70 variants of microcystins are known, and a single microcystin synthetase (mcy) gene cluster consisting of 10 genes (mcyA to mcyJ) has been identified to be responsible for the production of all known variants of microcystins. Our previous multilocus sequence typing (MLST) analysis of the seven housekeeping genes indicated that microcystin-producing strains of M. aeruginosa are classified into two phylogenetic groups.     

Endogenous Dopamine Maintains Synchronous Oscillation of Intracellular Calcium in Primary Cultured-Mouse Midbrain Neurons

We demonstrated synchronous oscillation of intracellular Ca2+ in cultured-mouse mid-brain neurons. This synchronous oscillation was thought to result from spontaneous and synchronous neural bursts in a synaptic neural network. We also examined the role of endogenous dopamine in neural networks showing synchronous oscillation. Immunocytochemical study revealed a few tyrosine hydroxylase (TH)-positive dopaminergic neurons, and that cultured neurons expressed synaptophysin and synapsin I. Western blot analyses comfirmed synaptophysin, TH, and 2 types of dopamine receptor (DR), D1R and D2R expression. The synchronous oscillation in midbrain neurons was abolished by the application of R(-)-2-amino-5-phosphonopentanoic acid (AP-5) as an N-methyl-D-aspartate receptor (NMDAR) antagonist. This result suggests that the synchronous oscillation in midbrain neurons requires glutamatergic transmissions, as was the case in previously reported cortical neurons. SCH-12679, a D1R antagonist, inhibited synchronous oscillation in midbrain neurons, while raclopride, a D2R antagonist, induced a transient increase of intracellular Ca2+ and inhibited synchronous oscillation. We consider that endogenous dopamine maintains synchronous oscillation of intracellular Ca2+ through D1R and D2R, and that these DRs regulate intracellular Ca2+in distinctly different ways. Synchronous oscillation of midbrain neurons would be a useful tool for in vitro researches into various neural disorders directly or indirectly caused by dopaminergic neurons.     

Possible involvement of organic anion and cation transporters in renal excretion of xanthine derivatives, 3-methylxanthine and enprofylline

Whether organic anion and cation transporters are involved in the renal excretion of xanthine derivatives, 3-methylxanthie and enprofylline, remains unclear. In this study, we have investigated the effects of typically predominant substrates for organic anion and cation transporters on the tubular secretion of 3-methylxanthine and enprofylline in rats. In the renal clearance experiments using typical substrates for organic anion transporters, probenecid and p-aminohippurate, probenecid (20 mg/kg), but not p-aminohippurate (100 mg/kg), significantly decreased the renal clearance and clearance ratio of 3-methylxanthine and enprofylline. The typical substrates for organic cation transport systems, tetraethylammonium (30.6 mg/kg) and cimetidine (50 or 100 mg/kg), significantly decreased the renal clearance and clearance ratio of 3-methylxanthine and enprofylline. These results suggest that the renal secretory transport of 3-methylxanthine and enprofylline are mediated by probenecid-, cimetidine- and tetraethylammonium-sensitive transport systems. Uric acid, an organic anion, significantly inhibited the renal secretion of 3-methylxanthine, but not enprofylline, suggesting that the renal tubular transport of 3-methylxanthine is also mediated via uric acid-sensitive transport system. These findings suggest the possibility that both organic anion and cation transporters are, at least, involved in the renal tubular transport of 3-methylxanthine and enprofylline in rats.     

Effects of Cu,Cd and Zn on photosynthesis of freshwater benthic algae

One hundred and eighteen algal isolates comprising seven classes were obtained from a range of sites from polluted rivers running through Cu or Zn mining regions, and from unpolluted rivers. All the isolates were tested for photosynthetic activity when exposed to Cu, Cd or Zn. The tolerance levels of Bacillariophyceae, Charophyceae, Cyanophyceae and Chlorophyceae to Cu showed significant positive correlations with Cu concentrations in the field. However the distribution of metal sensitivities of the algae from the sites with the same metal concentration was broad. Both Bacillariophyceae and Charophyceae had a number of strains whose sensitivity to Cu differed more widely in relation to Cu levels in the environment than Cyanophyceae and Chlorophyceae. Cyanophyceae were sensitive to all three metals, whether or not isolates were obtained from polluted sites, whereas Chlorophyceae tended to have high tolerance even in isolates from unpolluted sites. For Cd and Zn the correlation between tolerance levels and concentrations in the field was not so clear as for Cu. The occurrence of Cu tolerance was shown in 4 diatom species and one Charophyceae, whereas metal resistance occurred in some Chlorophyceae. Cu-tolerant isolates tended also to be Zn-tolerant in Bacillariophyceae, and Cd-resistant isolates tended also to be Zn-resistant in Chlorophyceae.     

Optimization of 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidines to generate a highly selective PI3Kδ inhibitor

Chemical optimization of the 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine (THPP) scaffold was conducted with a focus on cellular potency while maintaining high selectivity against PI3K isoforms. Compound 11f was identified as a potent, highly selective and orally available PI3Kδ inhibitor. In addition, 11f exhibited efficacy in an in vivo antibody production model. The desirable drug-like properties and in vivo efficacy of 11f suggest its potential as a drug candidate for the treatment of autoimmune diseases and leukocyte malignancies.     

Regional heterogeneities in the production of uric acid from adenosine in the bivascularly perfused rat liver

The heterogeneity of the liver parenchyma in relation to uric acid production from adenosine was investigated using the bivascularly perfused rat liver in the anterograde and retrograde modes. Adenosine was infused in livers from fed rats during 20 min at four different concentrations (20, 50, 100 and 200 M) according to four experimental protocols as follows: (A) anterograde perfusion, with adenosine infusion into the portal vein; (B) anterograde perfusion, with adenosine in the hepatic artery, (C) retrograde perfusion, with adenosine in the hepatic vein; (D) retrograde perfusion, with adenosine in the hepatic artery. With protocols A, B, and D uric acid production from adenosine was always characterized by initial bursts followed by progressive decreases toward smaller steady-states. With protocol C the initial burst was present only when 200 M adenosine was infused. The initial bursts in uric acid production were accompanied by simultaneous increases in the ratio of uric acid production/adenosine uptake rate. These initial bursts are thus representing increments in the production of uric acid that are not corresponded by similar increments in the metabolic uptake rates of adenosine. Global analysis of uric acid production revealed that the final steady-state rates were approximately equal for all infusion rates with protocols A, B and C, but smaller with protocol D. This difference, however, can be explained in terms of the differences in accessible cellular spaces, which are much smaller when protocol D is employed. When the analysis was performed in terms of the extra amounts of uric acid produced during the infusion of adenosine, where the initial bursts are also taken into account, different dose-response curves were found for each experimental protocol. These differences cannot be explained in terms of the accessible cell spaces and they are likely to reflect regional heterogeneities. From the various dose-response curves and from the known characteristics of the microcirculation of the rat liver it can be concluded that the initial bursts in uric acid production are generated in periportal hepatocytes. The reason for this heterogeneity could be related to the metabolic effects of adenosine, especially to oxygen uptake inhibition, which is likely to produce changes in the ATP/AMP ratios.     

Gastrointestinal helminth parasitism in fruit-eating bats (Chiroptera, Stenodermatinae) from western Amazonian Brazil

In this paper we report endoparasites from a sample of 50 stenodermatine bats collected mainly over lick sites at the Parque Nacional da Serra do Divisor, westernmost extremity of Amazonian Brazil. Four helminth species were recovered (Hasstilesia tricolor, Vampirolepis elongatus, Cheiropteronema globocephala. and Capillaria sp.), most of them from small intestines. Overall helminth prevalence achieved 26% (13/50) and the more prevalent species was H. tricolor (20%). Previously unknown in bats and reported for the first time in Brazil, this digenetic trematode was found in seven of the 18 bat species studied here. We argue that the drinking behaviour of stenodermatines at lick sites may be implicated in the dissemination of helminth infection among these bats.     

L1-dependent neuritogenesis involves ankyrinB that mediates L1-CAM coupling with retrograde actin flow

The cell adhesion molecule L1 (L1-CAM) plays critical roles in neurite growth. Its cytoplasmic domain (L1CD) binds to ankyrins that associate with the spectrin-actin network. This paper demonstrates that L1-CAM interactions with ankyrinB (but not with ankyrinG) are involved in the initial formation of neurites. In the membranous protrusions surrounding the soma before neuritogenesis, filamentous actin (F-actin) and ankyrinB continuously move toward the soma (retrograde flow). Bead-tracking experiments show that ankyrinB mediates L1-CAM coupling with retrograde F-actin flow in these perisomatic structures. Ligation of the L1-CAM ectodomain by an immobile substrate induces L1CD-ankyrinB binding and the formation of stationary ankyrinB clusters. Neurite initiation preferentially occurs at the site of these clusters. In contrast, ankyrinB is involved neither in L1-CAM coupling with F-actin flow in growth cones nor in L1-based neurite elongation. Our results indicate that ankyrinB promotes neurite initiation by acting as a component of the clutch module that transmits traction force generated by F-actin flow to the extracellular substrate via L1-CAM.