Semisynthesis of 6-chloropurine-2'-deoxyriboside 5'-dimethoxytrityl 3'-(2-cyanoethyl-N,N-diisopropylamino)phosphoramidite and its use in the synthesis of fluorescently labeled oligonucleotides

An efficient enzymatic synthesis of 6-chloropurine-2'-deoxyriboside from the reaction of 6-chloropurine with 2'-deoxycytidine catalyzed by nucleoside-2'-deoxyribosyltransferase (E.C. 2.4.2.6) followed by chemical conversion into the 5'-dimethoxytrityl 3'-(2-cyanoethyl-N,N-diisopropylamino) phosphoramidite derivative is described. The phosphoramidite derivative was incorporated site-specifically into an oligonucleotide and used for the introduction of a tethered tetramethylrhodamine-cadaverine conjugate. The availability of an efficient route to 6-chloropurine-2'-deoxyriboside 5'-dimethoxytrityl 3'-(2-cyanoethyl-N,N-diisopropylamino)phosphoramidite enables the facile synthesis of oligonucleotides containing a range of functional groups tethered to deoxyadenosine residues.     

Subtypes of the plasmid-encoded serine protease EspP in Shiga toxin-producing Escherichia coli: distribution, secretion, and proteolytic activity

We investigated the prevalence, distribution, and structure of espP in Shiga toxin-producing Escherichia coli (STEC) and assessed the secretion and proteolytic activity of the encoded autotransporter protein EspP (extracellular serine protease, plasmid encoded). espP was identified in 56 of 107 different STEC serotypes. Sequencing of a 3,747-bp region of the 3,900-bp espP gene distinguished four alleles (espPalpha, espPbeta, espPgamma, and espPdelta), with 99.9%, 99.2%, 95.3%, and 95.1% homology, respectively, to espP of E. coli O157:H7 strain EDL933. The espPbeta, espPgamma, and espPdelta genes contained unique insertions and/or clustered point mutations that enabled allele-specific PCRs; these demonstrated the presence of espPalpha, espPbeta, espPgamma, and espPdelta in STEC isolates belonging to 17, 16, 15, and 8 serotypes, respectively. Among four subtypes of EspP encoded by these alleles, EspPalpha (produced by enterohemorrhagic E. coli [EHEC] O157:H7 and the major non-O157 EHEC serotypes) and EspPgamma cleaved pepsin A, human coagulation factor V, and an oligopeptide alanine-alanine-proline-leucine-para-nitroaniline, whereas EspPbeta and EspPdelta either were not secreted or were proteolytically inactive. The lack of proteolysis correlated with point mutations near the active serine protease site. We conclude that espP is widely distributed among STEC strains and displays genetic heterogeneity, which can be used for subtyping and which affects EspP activity. The presence of proteolytically active EspP in EHEC serogroups O157, O26, O111, and O145, which are bona fide human pathogens, suggests that EspP might play a role as an EHEC virulence factor.     

Catalytic mechanism of the glutathione peroxidase-type tryparedoxin peroxidase of Trypanosoma brucei

Trypanosoma brucei, the causative agent of African sleeping sickness, encodes three nearly identical genes for cysteine-homologues of the selenocysteine-containing glutathione peroxidases. The enzymes, which are essential for the parasites, lack glutathione peroxidase activity but catalyse the trypanothione/Tpx (tryparedoxin)-dependent reduction of hydroperoxides. Cys47, Gln82 and Trp137 correspond to the selenocysteine, glutamine and tryptophan catalytic triad of the mammalian selenoenzymes. Site-directed mutagenesis revealed that Cys47 and Gln82 are essential. A glycine mutant of Trp137 had 13% of wild-type activity, which suggests that the aromatic residue may play a structural role but is not directly involved in catalysis. Cys95, which is conserved in related yeast and plant proteins but not in the mammalian selenoenzymes, proved to be essential as well. In contrast, replacement of the highly conserved Cys76 by a serine residue resulted in a fully active enzyme species and its role remains unknown. Thr50, proposed to stabilize the thiolate anion at Cys47, is also not essential for catalysis. Treatment of the C76S/C95S but not of the C47S/C76S double mutant with H2O2 induced formation of a sulfinic acid and covalent homodimers in accordance with Cys47 being the peroxidative active site thiol. In the wild-type peroxidase, these oxidations are prevented by formation of an intramolecular disulfide bridge between Cys47 and Cys95. As shown by MS, regeneration of the reduced enzyme by Tpx involves a transient mixed disulfide between Cys95 of the peroxidase and Cys40 of Tpx. The catalytic mechanism of the Tpx peroxidase resembles that of atypical 2-Cys-peroxiredoxins but is distinct from that of the selenoenzymes.     

Combined prenatal and postnatal protein restriction influences adult kidney structure, function, and arterial pressure

The effects of prenatal protein restriction on adult renal and cardiovascular function have been studied in considerable detail. However, little is known about the effects of life-long protein restriction, a common condition in the developing world. Therefore, we determined in rats the effects of combined pre- and postnatal protein restriction on adult arterial pressure and renal function and responses to increased dietary sodium. Nephron number was also determined. Male Sprague-Dawley rats were born to mothers fed a low [8% (wt/wt), LP] or normal [20% (wt/wt), NP] isocaloric protein diet throughout pregnancy and maintained on these diets after birth. At postnatal day 135, nephron number, mean arterial pressure (MAP), and renal function were determined. A high-NaCl [8.0% (wt/wt), high-salt] diet was fed to a subset of rats from weaning. MAP was less in LP than in NP rats (120 +/- 2 vs. 128 +/- 2 mmHg, P < 0.05) and was not significantly altered by increased salt intake. Nephron number was 31% less in LP than in NP rats (P < 0.001). The volume of individual glomeruli was also less in LP than in NP rats, as were calculated effective renal plasma flow and glomerular filtration rate. Glomerular filtration rate, but not effective renal plasma flow, appeared to be increased by high salt intake, particularly in LP rats. In conclusion, protein restriction induced a severe nephron deficit, but MAP was lower, rather than higher, in protein-restricted than in control rats in adulthood. These findings indicate that the postnatal environment plays a key role in determining the outcomes of developmental programming.     

Wnt-3a utilizes a novel low dose and rapid pathway that does not require casein kinase 1-mediated phosphorylation of Dvl to activate beta-catenin

The current view of canonical Wnt signalling is that following Wnt binding to its receptors (Frizzled-Lrp5/6), dishevelled (Dvl) becomes hyperphosphorylated, and the signal is transduced to the APC-GSK3beta-axin-beta-catenin multiprotein complex, which subsequently dissociates. As a result beta-catenin is not phosphorylated, escapes proteosomal degradation and activates its target genes after translocation to the nucleus. Here, we analyzed the importance of the Wnt-3a-induced phosphorylation and shift in electrophoretic migration of Dvl (PS-Dvl) for the activation of beta-catenin. Analysis of Wnt-3a time- and dose-responses in a dopaminergic cell line showed that beta-catenin is activated rapidly (within minutes) and at a low dose of Wnt-3a (1 ng/ml). Surprisingly, PS-Dvl appeared only after 30 min and at greater doses (> or =20 ng/ml) of Wnt-3a. Moreover, we found that a casein kinase 1 inhibitor (D4476) or siRNA for casein kinase 1 delta/epsilon (CK1delta/epsilon) blocked the Wnt-3a-induced PS-Dvl. Interestingly, CK1 inhibition or siRNA for CK1delta/epsilon did not ablate the activation of beta-catenin by Wnt-3a, indicating that there is a PS-Dvl-independent path to activate beta-catenin. The increase in beta-catenin activation by Wnt-3a (PS-Dvl-dependent or -independent) were blocked by Dickkopf1 (Dkk1), suggesting that the effect of Wnt-3a is in both cases mediated by Lrp5/6 receptors. Thus, our results show that Wnt-3a rapidly induce a partial activation of beta-catenin in the absence of PS-Dvl at low doses, while at high doses induce a full activation of beta-catenin in a PS-Dvl-dependent manner.     

Dentinogenesis imperfecta

Dentinogenesis imperfecta is a congenital dentin dysplasia that occurs either isolated or associated with a genetic disorder known as osteogenesis imperfecta. Dentinogenesis imperfecta is inherited in an autosomal dominant pattern. Clinically the teeth color of both dentitions varies from brown to a translucent gray with an opalescent sheen. Shields et al. (1973) proposed a classification of Dentinogenesis imperfecta into three types: type I, associated with osteogenesis imperfecta; type II, hereditary opalescent dentin; type III Brandywine-type. The phenotypes of Dentinogenesis imperfecta are described in regard to their genetic defects, pathology, radiology and histopathology as well as their dental treatment.     

Effects of Ethanolic Extract of Cynara cardunculus (Artichoke) Leaves on Neuroinflammatory and Neurochemical Parameters in a Diet-Induced Mice Obesity Model

Neurochemical Research - This study aimed to evaluate the effect of Cynara cardunculus leaf ethanol extract on inflammatory and oxidative stress parameters in the hypothalamus, prefrontal cortex,...