Novel C-ring analogues of 20(S)-camptothecin. Part 3: synthesis and their in vitro cytotoxicity of A-, B- and C-ring analogues

Several 5-substituted alkoxy 20(S)-camptothecin analogues having A- and B-ring substituents were prepared via semi-synthesis. Most of these compounds were found to exhibit potent anti-cancer activity based on their in vitro cytotoxicity data obtained against human tumor cell lines.     

Design, synthesis, and biological activity of novel factor Xa inhibitors: 4-aryloxy substituents of 2,6-diphenoxypyridines

A novel series of triaryloxypyridines have been designed to inhibit factor Xa, a serine protease strategically located in the coagulation cascade. Inhibitor 5e has a K(I) against factor Xa of 0.12nM and is greater than 8000- and 2000-fold selective over two related serine proteases, thrombin and trypsin, respectively. The 4-position of the central pyridine has been identified as a site that tolerates various substitutions without deleterious effects on potency and selectivity. This suggests that the 4-position of the pyridine ring is an ideal site for chemical modifications to identify inhibitors with improved pharmacokinetic characteristics. This investigation has resulted in inhibitor 5d, which has an oral availability of 6% in dogs. The synthesis, in vitro activity, and in vivo profile of this class of inhibitors is outlined.     

Sequestosome 1/p62, a Scaffolding Protein, Is a Newly Identified Partner of IRS-1 Protein

Defects in the insulin-signaling pathway may lead to the development of skeletal muscle insulin resistance, which is one of the earliest abnormalities detected in individuals with the metabolic syndrome and predisposes them to develop type 2 diabetes. Previous studies have shown that deletion of the mouse sequestosome 1/p62 gene results in mature-onset obesity that progresses to insulin and leptin resistance and, ultimately, type 2 diabetes. Sequestosome 1/p62 is involved in receptor-mediated signal transduction and functions as an intracellular signal modulator or adaptor protein. Insulin receptor substrate-1 (IRS-1) plays a central role in transducing the insulin signal via phosphorylation, protein-protein interactions, and protein modifications. Mapping studies demonstrated that the SH(2) domain at the amino terminus of sequestosome 1/p62 interacts with IRS-1 upon insulin stimulation. Further, IRS-1 interacts with p62 through its YMXM motifs at Tyr-608, Tyr-628, and/or Tyr-658 in a manner similar to its interaction with p85 of phosphoinositol 3-kinase. Overexpression of p62 increased phosphorylation of Akt, GLUT4 translocation, and glucose uptake, providing evidence that p62 participates in the insulin-signaling pathway through its interactions with IRS-1.     

Identification and characterization of a novel Ribose 5-phosphate isomerase B from Leishmania donovani

Leishmaniasis is a group of tropical diseases caused by protozoan parasites of the genus Leishmania. Due to the emergence of resistance to the available antileishmanial drugs there is an immediate need to identify molecular targets on which to base future treatment strategies. Ribose 5-phosphate isomerase (Rpi; EC 5.3.1.6) is a key enzyme of the pentose phosphate pathway (PPP) which catalyses the reversible aldose-ketose isomerization between Ribose 5-phosphate (R5P) and Ribulose 5-phosphate (Ru5P). It exists in two isoforms A and B. These two are completely unrelated enzymes catalyzing the same reaction. Analysis of the Leishmania infantum genome revealed that though the RpiB gene is present, RpiA homologs are completely absent. An absence of RpiBs in the genomes of higher animals makes this enzyme a possible target for the chemotherapy of Leishmaniasis. In this paper, we report for the first time the presence of B isoform of the Rpi enzyme in Leishmania donovani (LdRpiB) by cloning and molecular characterization of the enzyme. An amplified L. donovani RpiB gene is 519 bp and encodes for a putative 172 amino acid protein with a molecular mass of ～19 kDa. An ～19 kDa protein with poly-His tag at the C-terminal end was obtained by heterologous expression of LdRpiB in Escherichia coli. The recombinant form of RpiB was obtained in soluble and active form. The LdRpiB exists as a dimer of dimers i.e. the tetramer form. The polyclonal antibody against Trypanosoma cruzi RpiB could detect a band of ～19 kDa with the purified recombinant RpiB as well as native RpiB from the L. donovani promastigotes. Recombinant RpiB obeys the classical Michaelis-Menten kinetics utilizing R5P as the substrate with a K(m) value of 2.4±0.6 mM and K(cat) value of 30±5.2 s(-1). Our study confirms the presence of Ribose 5-phosphate isomerase B in L. donovani and provides functional characterization of RpiB for further validating it as a potential drug target.     

Myrtenal, a natural monoterpene, down-regulates TNF-α expression and suppresses carcinogen-induced hepatocellular carcinoma in rats

Hepatocellular carcinoma is one of the most common cancers and lethal diseases in the world. Recently, many researchers focused to identify novel chemotherapeutic agents from natural sources against hepatocarcinogenesis. The diverse therapeutic potential of essential oils has drawn the attention of researchers to test them for anticancer activity, taking advantage of the fact that their mechanism of action is dissimilar to that of chemotherapeutic agents. Earlier reports indicated that essential oil components, especially monoterpenes, have multiple pharmacological effects which could account for the terpene-tumor suppressive activity. In the present study, it is shown that myrtenal, a natural monoterpene, which acts as an antineoplastic agent against diethylnitrosamine induced phenobarbital promoted experimental hepatocellular carcinoma. The results revealed an elevated level of microsomal lipid peroxidation in the liver, which was found to be significantly reduced by myrtenal treatment. On the contrary, the Phase I hepatic drug metabolizing enzymes' (cytochrome P(450), cytochrome b (5), NADPH-cytochrome c reductase, NADH-cytochrome b ( 5 ) reductase) levels were decreased and the Phase II enzymes (glutathione-S-transferase, uridine 5'-diphospho-glucuronyl transferase) were increased in carcinogen-administered animals, which were reverted to near normalcy upon myrtenal administration. Our findings also showed that myrtenal restrains the liver cancer by preventing the DEN-PB induced up-regulation of TNF-α protein expression by immunoblot. Furthermore, transmission electron microscopic examination also indicated that myrtenal prevents the carcinogen-induced changes in the architecture of liver tissue and cell structure. Thus, this study shows that myrtenal has the ability to suppress the hepatocellular carcinoma in rats.     

Phototrophic Phylotypes Dominate Mesothermal Microbial Mats Associated with Hot Springs in Yellowstone National Park

The mesothermal outflow zones (50-65°C) of geothermal springs often support an extensive zone of green and orange laminated microbial mats. In order to identify and compare the microbial inhabitants of morphologically similar green-orange mats from chemically and geographically distinct springs, we generated and analyzed small-subunit ribosomal RNA (rRNA) gene amplicons from six mesothermal mats (four previously unexamined) in Yellowstone National Park. Between three and six bacterial phyla dominated each mat. While many sequences bear the highest identity to previously isolated phototrophic genera belonging to the Cyanobacteria, Chloroflexi, and Chlorobi phyla, there is also frequent representation of uncultured, unclassified members of these groups. Some genus-level representatives of these dominant phyla were found in all mats, while others were unique to a single mat. Other groups detected at high frequencies include candidate divisions (such as the OP candidate clades) with no cultured representatives or complete genomes available. In addition, rRNA genes related to the recently isolated and characterized photosynthetic acidobacterium "Candidatus Chloracidobacterium thermophilum" were detected in most mats. In contrast to microbial mats from well-studied hypersaline environments, the mesothermal mats in this study accrue less biomass and are substantially less diverse, but have a higher proportion of known phototrophic organisms. This study provides sequences appropriate for accurate phylogenetic classification and expands the molecular phylogenetic survey of Yellowstone microbial mats.     

Elucidation of neuroprotective role of endogenous GABA and energy metabolites middle cerebral artery occluded model in rats

The excitatory amino acids (EAA) like glutamate, aspartate and inhibitory neurotransmitter GABA (gama amino butyric acid) play an important role in the pathophysiology of cerebral ischemia. The objective of the present study is to elucidate the role of endogenous GABA against EAA release in different regions during ischemia. The transient focal ischemia was induced in rats by using middle cerebral artery occlusion model (MCAo). The results indicate gradual elevation of brain glutamate, aspartate and GABA level at different brain regions and attained peak level at 72 h of ischemic reperfusion (IR). At 168 h of IR the EAA levels declined to base line but GABA level was found to be still elevated. The biochemical analysis shows the depleted brain ATP, Na+K+ATPase content and triphasic response of glutathione activity. It can be concluded that time dependent variation in the EAA and GABA release, endogenous GABA can be neuroprotective and earlier restoration of energy deprivation is essential to prevent further neurodegeneration. To have efficient treatment in ischemic condition, multiple approaches like energy supply, antagonism of EAA, controlling calcium function are essential.     

Sequence Analysis of 16S rRNA and secA Genes Confirms the Association of 16SrI‐B Subgroup Phytoplasma with Oil Palm (Elaeis guineensis Jacq.) Stunting Disease in India

During January 2010, severe stunting symptoms were observed in clonally propagated oil palm (Elaeis guineensis Jacq.) in West Godavari district, Andhra Pradesh, India. Leaf samples of symptomatic oil palms were collected, and the presence of phytoplasma was confirmed by nested polymerase chain reaction (PCR) using universal phytoplasma‐specific primer pairs P1/P7 followed by R16F2n/R16R2 for amplification of the 16S rRNA gene and semi‐nested PCR using universal phytoplasma‐specific primer pairs SecAfor1/SecArev3 followed by SecAfor2/SecArev3 for amplification of a part of the secA gene. Sequencing and BLAST analysis of the ～1.25 kb and ～480 bp of 16S rDNA and secA gene fragments indicated that the phytoplasma associated with oil palm stunting (OPS) disease was identical to 16SrI aster yellows group phytoplasma. Further characterization of the phytoplasma by in silico restriction enzyme digestion of 16S rDNA and virtual gel plotting of sequenced 16S rDNA of ～1.25 kb using iPhyClassifier online tool indicated that OPS phytoplasma is a member of 16SrI‐B subgroup and is a ‘Candidatus Phytoplasma asteris’‐related strain. Phylogenetic analysis of 16S rDNA and secA of OPS phytoplasma also grouped it with 16SrI‐B. This is the first report of association of phytoplasma of the 16SrI‐B subgroup phytoplasma with oil palm in the world.     

Design and synthesis of 3,5-diarylpiperidin-2,6-diones as anticonvulsant agents

The present Letter describes a one-pot multi-component method that allows the efficient and mild preparation of 3,5-diphenylpiperidin-2,6-dione and a new series of 3,5-diarylpiperidin-2,6-dione derivatives from ethyl 2-arylacetates, formaldehyde and ammonia/aliphatic/aromatic amines. The structures of the compounds were elucidated by IR, NMR spectroscopic data and microanalyses. The anticonvulsant activities of these compounds were evaluated by maximal electroshock seizure test and were also evaluated for motor impairment. Among the synthesized compounds, 5a, 5b, 5d, and 5e could be considered potentially the most useful and safe therapeutic compound and 5g, 5i, 5j, 5m, and 5o exhibit potent activities.     

Genome-enabled prediction of genetic values using radial basis function neural networks

The availability of high density panels of molecular markers has prompted the adoption of genomic selection (GS) methods in animal and plant breeding. In GS, parametric, semi-parametric and non-parametric regressions models are used for predicting quantitative traits. This article shows how to use neural networks with radial basis functions (RBFs) for prediction with dense molecular markers. We illustrate the use of the linear Bayesian LASSO regression model and of two non-linear regression models, reproducing kernel Hilbert spaces (RKHS) regression and radial basis function neural networks (RBFNN) on simulated data and real maize lines genotyped with 55,000 markers and evaluated for several trait-environment combinations. The empirical results of this study indicated that the three models showed similar overall prediction accuracy, with a slight and consistent superiority of RKHS and RBFNN over the additive Bayesian LASSO model. Results from the simulated data indicate that RKHS and RBFNN models captured epistatic effects; however, adding non-signal (redundant) predictors (interaction between markers) can adversely affect the predictive accuracy of the non-linear regression models.