Nucleosides Having Quinolone Derivatives as Nitrogenated Base: Regiospecific and Stereospecific Ribosylation of 3-Carbethoxy-1,4-dihydro-4-oxoquinolines

Abstract

Ribosylation reactions of previously silylated 3-carbethoxy-8-methyl-1,4-dihydro-4-oxoquinoline (6a) and 3-carbethoxy-6-methyl-1,4-dihydro-4-oxoquinoline (6b) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (7), under Lewis acid catalysis, were studied. The method using hexamethyldisilazane (HMDS)/trimethylchlorosilane (TMCS) mixture for silylation and anhydrous stannic chloride as catalyst for ribosylation failed to give any nucleoside product. On the other hand, the protected nucleoside 3-carbethoxy-6-methyl-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-1,4-dihydro-4-oxoquinoline (8b) was obtained in good yields using bis(trimethylsilyl)trifluoroacetamide (BSTFA) containing 1% of TMCS and the same catalyst. Compound 8b was more easily isolated in higher yields with an improvement of the later method by replacing stannic chloride with trimethylsilyl trifluoromethanesulfonate (TMSOTf).

De-O-benzoylation of 8b with methanolic sodium hydroxide solution afforded the free riboside 3-carbomethoxy-6-methyl-1-β-D-ribofuranosyl-1,4-dihydro-4-oxoquinoline (9b). The structures of the obtained products were confirmed by their LTV, MS, IR, ¹H and ¹³C-NMR data.     

Hypolipidemic and antiatherosclerotic potential of Pleurotus ostreatus, cultived by submerged fermentation in the high-fat diet fed rats

The ability of Pleurotus ostreatus biomass, cultived by submerged fermentation, to produce beneficial effect on lipid profile and macrophages activity during a high-fat diet (HFD) for a long-term intake was investigated. Blood samples were collected through cardiac puncture to measure the plasma cholesterol, triglycerides, low-density protein (LDL), high-density protein (HDL), aspartate aminotransferase (AST) activity, urea-blood urea nitrogen (BUN)/creatinine ratio of rats fed on an HFD for 4 months. Dosage of lipid hydroperoxides was carried out on methanolic extract of liver tissue. Peritoneal macrophages activity was evaluated in relation to the superoxide anion, hydrogen peroxide and nitric oxide production, phagocytosis and lysosomal volume. The administration of P. ostreatus significantly altered the lipid profile and oxidative stress as related to the LDL and triglycerides decrease and inhibitory effects on superoxide anion and hydrogen peroxide production. All findings of this study lead us to suggest that the P. ostreatus maybe a beneficial agent in the hyperlipidemia and atherosclerosis treatments.     

Three new species of Fufius Simon, 1888 (Araneae,Cyrtaucheniidae) from Brazil with the redescription of Fufius funebris Vellard, 1924 and description of the female of Fufius lucasae Guadanucci & Indicatti, 2004

The mygalomorph neotropical genus Fufius Simon, 1888 comprises ten species, distributed from Guatemala in Central America to southeastern Brazil, in South America. Most of the species were described from northern South America, in the Amazonian region. Only F. funebris Vellard, 1924 and F. lucasae Guadanucci & Indicatti, 2004 are known from regions more to the south of the continent. Herein we describe three new Brazilian species, Fufius minusculus sp. n. and F. jalapensis sp. n. from the state of Tocantins, and F. candango sp. n. from Distrito Federal. The female of F. lucasae is described for first time and the male and female of F. funebris are redescribed based on specimens collected at the type locality.     

Cholesterol reduction ameliorates glucose-induced calcium handling and insulin secretion in islets from low-density lipoprotein receptor knockout mice

Aims/hypothesis

Changes in cellular cholesterol level may contribute to beta cell dysfunction. Islets from low density lipoprotein receptor knockout (LDLR^−/−) mice have higher cholesterol content and secrete less insulin than wild-type (WT) mice. Here, we investigated the association between cholesterol content, insulin secretion and Ca^2 + handling in these islets.

Methods

Isolated islets from both LDLR^−/− and WT mice were used for measurements of insulin secretion (radioimmunoassay), cholesterol content (fluorimetric assay), cytosolic Ca^2 + level (fura-2AM) and SNARE protein expression (VAMP-2, SNAP-25 and syntaxin-1A). Cholesterol was depleted by incubating the islets with increasing concentrations (0–10 mmol/l) of methyl-beta-cyclodextrin (MβCD).

Results

The first and second phases of glucose-stimulated insulin secretion (GSIS) were lower in LDLR^−/− than in WT islets, paralleled by an impairment of Ca^2 + handling in the former. SNAP-25 and VAMP-2, but not syntaxin-1A, were reduced in LDLR^−/− compared with WT islets. Removal of excess cholesterol from LDLR^−/− islets normalized glucose- and tolbutamide-induced insulin release. Glucose-stimulated Ca^2 + handling was also normalized in cholesterol-depleted LDLR^−/− islets. Cholesterol removal from WT islets by 0.1 and 1.0 mmol/l MβCD impaired both GSIS and Ca^2 + handling. In addition, at 10 mmol/l MβCD WT islet showed a loss of membrane integrity and higher DNA fragmentation.

Conclusion

Abnormally high (LDLR^−/− islets) or low cholesterol content (WT islets treated with MβCD) alters both GSIS and Ca^2 + handling. Normalization of cholesterol improves Ca^2 + handling and insulin secretion in LDLR^−/− islets.     

Comparison of vitrification and slow cooling for umbilical tissues

The tissue cryopreservation maintains the cellular metabolism in a quiescence state and makes the conservation possible for an indefinite period of time. The choice of an appropriate cryopreservation protocol is essential for maintenance of cryopreserved tissue banks. This study evaluated 10 samples of umbilical cord, from which small fragments of tissue (Wharton’s jelly and cord lining membrane) were subjected to two protocols of cryopreservation: slow cooling and vitrification. The samples were frozen for a period of time ranging from 5 to 78 days. The efficiency of cryopreservation was evaluated by testing cell viability, histological analysis, cell culture, cytogenetic analysis and comparison with the results of the fresh samples. The results showed that the slow cooling protocol was more efficient than the vitrification for cryopreservation of umbilical cord tissue, because it has caused fewer changes in the structure of tissue (edema and degeneration of the epithelium) and, despite the significant decrease cell viability compared to fresh samples, the ability of cell proliferation in vitro was preserved in most samples. In conclusion, this study showed that it is possible to cryopreserve small fragments of tissue from the umbilical cord and, to obtain viable cells capable of proliferation in vitro after thawing, contributing to the creation of a frozen tissue bank.     

Demographic bottlenecks in tropical plant regeneration: A comparative analysis of causal influences

Mortality factors that act sequentially through the demographic transitions from seed to sapling may have critical effects on recruitment success. Understanding how habitat heterogeneity influences the causal factors that limit propagule establishment in natural populations is central to assess these demographic bottlenecks and their consequences. Bamboos often influence forest structure and dynamics and are a major factor in generating landscape complexity and habitat heterogeneity in tropical forests. To understand how patch heterogeneity influences plant recruitment we studied critical establishment stages during early recruitment of Euterpe edulis, Sloanea guianensis and Virola bicuhyba in bamboo and non-bamboo stands in the Brazilian Atlantic forest. We combined observational studies of seed rain and seedling emergence with seed addition experiments to evaluate the transition probabilities among regeneration stages within bamboo and non-bamboo stands. The relative importance of each mortality factor was evaluated by determining how the loss of propagules affected stage-specific recruitment success. Our results revealed that the seed addition treatment significantly increased seedling survivorship for all three species. E. edulis seedling survival probability increased in the addition treatment in the two stand types. However, for S. guianensis and V. bicuhyba this effect depended strongly on artificially protecting the seeds, as both species experienced increased seed and seedling losses due to post-dispersal seed predators and herbivores. Propagules of all three species had a greater probability of reaching subsequent recruitment stages when protected. The recruitment of large-seeded V. bicuhyba and E. edulis appears to be much more limited by post-dispersal factors than by dispersal limitation, whereas the small-seeded S. guianensis showed an even stronger effect of post-dispersal factors causing recruitment collapse in some situations. We demonstrated that E. edulis, S. guianensis and V. bicuhyba are especially susceptible to predation during early compared with later establishment stages and this early stage mortality can be more crucial than stand differences as determinants of successful regeneration. Among-species differences in the relative importance of dispersal vs. establishment limitation are mediated by variability in species responses to patch heterogeneity. Thus, bamboo effects on the early recruitment of non-bamboo species are patchy and species-specific, with successional bamboo patches exerting a far-reaching influence on the heterogeneity of plant species composition and abundance.     

Life‐history costs associated with resistance to lambda‐cyhalothrin in the predatory ladybird beetle Eriopis connexa

• 1 The present study assessed the fitness of a lambda‐cyhalothrin‐resistant population of Eriopis connexa (Germar) with respect to development, reproduction, survival under prey scarcity and prey consumption.
• 2 Nontreated resistant females (R0) and females recovered after the topical application of 0.05, 0.10 and 0.25 mg active ingredient/mL of lambda‐cyhalothrin (R0.05, R0.10 and R0.25) produced, on average, 50% less eggs than susceptible females (S0), irrespective of the applied dose. All of the other traits evaluated remained similar. With respect to developmental characteristics, the larval viability and weight of adult male R0.25 progeny were statistically lower compared with the R0 and S0 progenies. Prey scarcity between days 3 and 13 of adulthood did not affect R0 and R0.25 survival, although egg production was significantly lower for R0 females, followed by R0.25 females, compared with S0 females.
• 3 The mean consumption of cotton aphids Aphis gossypii Glover over 5 consecutive days was significantly higher for S0, followed by R0 and R0.25, up to day 3 of observation. However, after day 4, prey consumption was similar among the three populations.
• 4 The results obtained in the present study show that resistant females have a lower reproductive output than susceptible females and that this is not related to the knockdown effect; however, the costs of recovering from knockdown interfere with the survival of offspring and also slightly with prey consumption. Thus, we conclude that the lambda‐cyhalothrin‐resistant E. connexa population exhibits an egg production disadvantage relative to the susceptible population and that this is increased when the population is subjected to prey scarcity.

     

Alcohol Impairs Predation Risk Response and Communication in Zebrafish

The effects of ethanol exposure on Danio rerio have been studied from the perspectives of developmental biology and behavior. However, little is known about the effects of ethanol on the prey-predator relationship and chemical communication of predation risk. Here, we showed that visual contact with a predator triggers stress axis activation in zebrafish. We also observed a typical stress response in zebrafish receiving water from these conspecifics, indicating that these fish chemically communicate predation risk. Our work is the first to demonstrate how alcohol effects this prey-predator interaction. We showed for the first time that alcohol exposure completely blocks stress axis activation in both fish seeing the predator and in fish that come in indirect contact with a predator by receiving water from these conspecifics. Together with other research results and with the translational relevance of this fish species, our data points to zebrafish as a promising animal model to study human alcoholism.