Opioid receptor antagonist affinity ligands: 6β-bromoacetamido-6-desoxynaltrexone and 6β-thioglycolamido-6-desoxynaltrexone

The present study, utilizing thioglycolamido as the reactive group, describes the synthesis and pharmacology of a new opioid antagonist affinity ligand, 6-thioglycolamido-6-desoxynaltrexone (TAN) and compares TAN with a related known compound, 6-bromoacetamido-6-desoxynaltrexone (BAN). Both compounds were tested for their reversible and irreversible inhibition of [³H]naloxone binding to calf brain membranes. Reversible binding of BAN and TAN had K_i values of 1×10^–9 and 1×10^–10 M, respectively as determined by log probit plots. Irreversible binding was determined after extensive washing to remove all non-covalently bound ligand. At a concentration of 5×10^–8 and 1×10^–8 M for BAN and TAN irreversible binding was inhibited 50% of the maximum value. A study of the time course of irreversible inhibition of [³H]naloxone binding revealed that maximal inhibition occurred within 5 min with a concentration of 1×10^–7 M of either agent. TAN but not BAN when administered systematically to mice produced an antinociceptive effect as measured by the writhing test. When administered intracerebraventricularly BAN did not block morphine-induced analgesia for more than 2 hr; whereas, with a single ED₅₀ dose of 20 nmoles of TAN i.c.v. morphine-induced analgesia was almost completely blocked for a period of over 24 hr, as determined by the tail flick test. Although the SH group of TAN were required for the covalent interaction with opioid receptors, the site of TAN's interaction appears to involve other than protein SH groups.     

Galinsosides A and B,bioactive flavanone glucosides from Galinsoga parviflora

Galinsosides A (1) and B (2), new flavanone glucosides together with two known flavanones, 7,3′,4′-trihydroxyflavanone (3) and 3,5,7,3′,4′-pentahydroxyflavanone (4) have been isolated from an ethyl acetate- soluble fraction of Galinsoga parviflora. Their structures were assigned on the basis of spectral studies. Compound 1 showed significant antioxidant and urease inhibitory activity while compound 2 was moderately active. On the other hand, 2 showed inhibitory potential against α-glucosidase.     

Study of PKRBD in HCV genotype 3a infected patients in response to interferon therapy in Pakistani population

Background

Hepatitis C virus (HCV) is a major cause of liver cirrhosis and hepatocellular carcinoma and infects about 3% world population. Response to interferon therapy depends upon the genotype of the virus and factors associated with the host. Despite a good response to interferon therapy, a considerable number of genotype 3a infected patients remains unalleviated.

Results

In total forty-nine patients including twenty-five non-responders (non-SVR) and twenty-four responders (SVR) were recruited. Patients were tested for viral status at different intervals and the isolated RNA was sequenced for the NS5A region in both groups. The comparison of PKRBD of HCV between the SVR and non-SVR patients did not confirm any significant difference in the number of mutations. However, when the sequence downstream to the PKRBD of NS5A was compared, two important statistically significant mutations were observed; at positions 2309 (Ala to Ser) and 2326 (Gly to Ala). These mutations were then analysed for tertiary protein structure and important structural changes were observed. Statistically significant difference was also observed when age groups of patients were compared; younger patients showed better response than the older ones.

Conclusions

The region between PKRBD and IRRDR may be important for prediction of response to IFN therapy for genotype 3a. ISDR and PKRBD have not shown any involvement in treatment response. Further functional analyses of these findings can help in understanding the involvement of the NS5A region in interferon treatment of HCV-3a infected patients.

     

The glucose metabolite methylglyoxal inhibits expression of the glucose transporter genes by inactivating the cell surface glucose sensors Rgt2 and Snf3 in yeast

Methylglyoxal (MG) is a cytotoxic by-product of glycolysis. MG has inhibitory effect on the growth of cells ranging from microorganisms to higher eukaryotes, but its molecular targets are largely unknown. The yeast cell-surface glucose sensors Rgt2 and Snf3 function as glucose receptors that sense extracellular glucose and generate a signal for induction of expression of genes encoding glucose transporters (HXTs). Here we provide evidence that these glucose sensors are primary targets of MG in yeast. MG inhibits the growth of glucose-fermenting yeast cells by inducing endocytosis and degradation of the glucose sensors. However, the glucose sensors with mutations at their putative ubiquitin-acceptor lysine residues are resistant to MG-induced degradation. These results suggest that the glucose sensors are inactivated through ubiquitin-mediated endocytosis and degraded in the presence of MG. In addition, the inhibitory effect of MG on the glucose sensors is greatly enhanced in cells lacking Glo1, a key component of the MG detoxification system. Thus the stability of these glucose sensors seems to be critically regulated by intracellular MG levels. Taken together, these findings suggest that MG attenuates glycolysis by promoting degradation of the cell-surface glucose sensors and thus identify MG as a potential glycolytic inhibitor.     

Isolation of Ceramides from Tagetes patula L. Yellow Flowers and Nematicidal Activity of the Fractions and Pure Compounds against Cyst Nematode,Heterodera zeae

Investigation of yellow flower extract of Tagetes patula L. led to the identification of an aggregate of five phytoceramides. Among them, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]icosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]heneicosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]docosanamide, and (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tricosanamide were identified as new compounds and termed as tagetceramides, whereas (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tetracosanamide was a known ceramide. A steroid (β‐sitosterol glucoside) was also isolated from the subsequent fraction. The structures of these compounds were determined on the basis of spectroscopic analyses, as well as chemical method. Several other compounds were also identified by GC/MS analysis. The fractions and some commercial products, a ceramide HFA, β‐sitosterol, and stigmasterol were evaluated against an economically important cyst nematode, Heterodera zeae. Ceramide HFA showed 100 % mortality, whereas, β‐sitosterol and stigmasterol were 40–50 % active, at 1 % concentration after 24 h of exposure time, while β‐sitosterol glucoside revealed no activity against the nematode.     

Enhancing the Open‐Circuit Voltage of Perovskite Solar Cells by up to 120 mV Using π‐Extended Phosphoniumfluorene Electrolytes as Hole Blocking Layers

Four π‐extended phosphoniumfluorene electrolytes (π‐PFEs) are introduced as hole‐blocking layers (HBL) in inverted architecture planar perovskite solar cells with the structure of ITO/PEDOT:PSS/MAPbI₃/PCBM/HBL/Ag. The deep‐lying highest occupied molecular orbital energy level of the π‐PFEs effectively blocks holes, decreasing contact recombination. It is demonstrated that the incorporation of π‐PFEs introduces a dipole moment at the PCBM/Ag interface, resulting in significant enhancement of the built‐in potential of the device. This enhancement results in an increase in the open‐circuit voltage of the device by up to 120 mV, when compared to the commonly used bathocuproine HBL. The results are confirmed both experimentally and by numerical simulation. This work demonstrates that interfacial engineering of the transport layer/contact interface by small molecule electrolytes is a promising route to suppress nonradiative recombination in perovskite devices and compensates for a nonideal energetic alignment at the hole‐transport layer/perovskite interface.     

Prior serum- and AICAR-induced AMPK activation in primary human myocytes does not lead to subsequent increase in insulin-stimulated glucose uptake

Exposing isolated rat skeletal muscle to 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside [AICAR, a pharmacological activator of AMP-activated protein kinase (AMPK)] plus serum leads to a subsequent increase in insulin-stimulated glucose transport (Fisher JS, Gao J, Han DH, Holloszy JO, and Nolte LA. Am J Physiol Endocrinol Metab 282: E18-E23, 2002). Our goal was to determine whether preincubation of primary human skeletal muscle cells with human serum and AICAR (Serum+AICAR) would also induce a subsequent elevation in insulin-stimulated glucose uptake. Cells were preincubated for 1 h under 4 conditions: 1) without AICAR or serum (Control), 2) with serum, 3) with AICAR, or 4) with Serum+AICAR. Some cells were then collected for immunoblot analysis to assess phosphorylation of AMPK (pAMPK) and its substrate acetyl-CoA carboxylase (ACC). Other cells were incubated for an additional 4 h without AICAR or serum and then used to measure basal or insulin-stimulated 2-deoxyglucose (2-DG) uptake. Level of pAMPK was increased (P < 0.01) for myotubes exposed to Serum+AICAR vs. all other groups. Phosphorylated ACC (pACC) levels were higher for both Serum+AICAR (P < 0.05) and AICAR (P < 0.05) vs. Control and Serum groups. Basal (P < 0.05) and 1.2 nM insulin-stimulated (P < 0.005) 2-DG uptake was higher for Serum vs. all other preincubation conditions at equal insulin concentration. Regardless of insulin concentration (0, 1.2, or 18 nM), 2-DG was unaltered in cells preincubated with Serum+AICAR vs. Control cells. In contrast to results with isolated rat skeletal muscle, increasing the pAMPK and pACC in human myocytes via preincubation with Serum+AICAR was insufficient to lead to a subsequent enhancement in insulin-stimulated glucose uptake.     

Partial nuclear pore complex disassembly during closed mitosis in Aspergillus nidulans

BACKGROUND: Many organisms undergo closed mitosis and locate tubulin and mitotic kinases to nuclei only during mitosis. How this is regulated is unknown. Interestingly, the NIMA kinase of Aspergillus nidulans interacts with two nuclear pore complex (NPC) proteins and NIMA is required for mitotic localization of the Cdk1 kinase to nuclei. Therefore, we wished to define the mechanism by which the NPC is regulated during A. nidulans' closed mitosis. RESULTS: The structural makeup of the NPC is dramatically changed during A. nidulans' mitosis. At least five NPC proteins disperse throughout the cell during mitosis while at least three structural components remain at the NPC. These modifications correlate with marked changes in the function of the NPC. Notably, during mitosis, An-RanGAP is not excluded from nuclei, and five other nuclear or cytoplasmic proteins investigated fail to locate as they do during interphase. Mitotic modification of the NPC requires NIMA and Cdk1 kinase activation. NIMA appears to be particularly important. Most strikingly, ectopic induction of NIMA promotes mitotic-like changes in NPC structure and function during S phase. Furthermore, NIMA locates to the NPC during entry into mitosis, and a dominant-negative version of NIMA that causes G2 delay dwells at the NPC. CONCLUSIONS: We conclude that partial NPC disassembly under control of NIMA and Cdk1 in A. nidulans may represent a new mechanism for regulating closed mitoses. We hypothesize that proteins locate by their relative binding affinities within the cell during A. nidulans' closed mitosis, analogous to what occurs during open mitosis.