Carbon monoxide stimulates insulin release and propagates Ca2+ signals between pancreatic beta-cells

A key question for understanding the mechanisms of pulsatile insulin release is how the underlying beta-cell oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i) are synchronized within and among the islets in the pancreas. Nitric oxide has been proposed to coordinate the activity of the beta-cells by precipitating transients of [Ca2+]i. Comparing ob/ob mice and lean controls, we have now studied the action of carbon monoxide (CO), another neurotransmitter with stimulatory effects on cGMP production. A strong immunoreactivity for the CO-producing constitutive heme oxygenase (HO-2) was found in ganglionic cells located in the periphery of the islets and in almost all islet endocrine cells. Islets from ob/ob mice had sixfold higher generation of CO (1 nmol.min-1.mg protein-1) than the lean controls. This is 100-fold the rate for their constitutive production of NO. Moreover, islets from ob/ob mice showed a threefold increase in HO-2 expression and expressed inducible HO (HO-1). The presence of an excessive islet production of CO in the ob/ob mouse had its counterpart in a pronounced suppression of the glucose-stimulated insulin release from islets exposed to the HO inhibitor Zn-protoporhyrin (10 microM) and in a 16 times higher frequency of [Ca2+]i transients in their beta-cells. Hemin (0.1 and 1.0 microM), the natural substrate for HO, promoted the appearance of [Ca2+]i transients, and 10 microM of the HO inhibitors Zn-protoporphyrin and Cr-mesoporphyrin had a suppressive action both on the firing of transients and their synchronization. It is concluded that the increased islet production of CO contributes to the hyperinsulinemia in ob/ob mice. In addition to serving as a positive modulator of glucose-stimulated insulin release, CO acts as a messenger propagating Ca2+ signals with coordinating effects on the beta-cell rhythmicity.     

Impaired insulin secretion and glucose tolerance in beta cell-selective Ca(v)1.2 Ca2+ channel null mice

Insulin is secreted from pancreatic beta cells in response to an elevation of cytoplasmic Ca(2+) resulting from enhanced Ca(2+) influx through voltage-gated Ca(2+) channels. Mouse beta cells express several types of Ca(2+) channel (L-, R- and possibly P/Q-type). beta cell-selective ablation of the gene encoding the L-type Ca(2+) channel subtype Ca(v)1.2 (betaCa(v)1.2(-/-) mouse) decreased the whole-cell Ca(2+) current by only approximately 45%, but almost abolished first-phase insulin secretion and resulted in systemic glucose intolerance. These effects did not correlate with any major effects on intracellular Ca(2+) handling and glucose-induced electrical activity. However, high-resolution capacitance measurements of exocytosis in single beta cells revealed that the loss of first-phase insulin secretion in the betaCa(v)1.2(-/-) mouse was associated with the disappearance of a rapid component of exocytosis reflecting fusion of secretory granules physically attached to the Ca(v)1.2 channel. Thus, the conduit of Ca(2+) entry determines the ability of the cation to elicit secretion.     

TPN-evoked dysfunction of islet lysosomal activity mediates impairment of glucose-stimulated insulin release

We examined the relation between nutrient-stimulated insulin secretion and the islet lysosome acid glucan-1,4-alpha-glucosidase system in rats undergoing total parenteral nutrition (TPN). During TPN treatment, serum glucose was normal, but free fatty acids, triglycerides, and cholesterol were elevated. Islets from TPN-infused rats showed increased basal insulin release, a normal insulin response to cholinergic stimulation but a greatly impaired response when stimulated by glucose or alpha-ketoisocaproic acid. This impairment of glucose-stimulated insulin release was only slightly ameliorated by the carnitine palmitoyltransferase 1 inhibitor etomoxir. However, in parallel with the impaired insulin response to glucose, islets from TPN-infused animals displayed reduced activities of islet lysosomal enzymes including the acid glucan-1,4-alpha-glucosidase, a putative key enzyme in nutrient-stimulated insulin release. By comparison, the same lysosomal enzymes were increased in liver tissue. Furthermore, in intact control islets, the pseudotetrasaccharide acarbose, a selective inhibitor of acid alpha-glucosidehydrolases, dose dependently suppressed islet acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase activities in parallel with an inhibitory action on glucose-stimulated insulin secretion. By contrast, when incubated with intact TPN islets, acarbose had no effect on either enzyme activity or glucose-induced insulin release. Moreover, when acarbose was added directly to TPN islet homogenates, the dose-response effect on the catalytic activity of the acid alpha-glucosidehydrolases was shifted to the right compared with control homogenates. We suggest that a general dysfunction of the islet lysosomal/vacuolar system and reduced catalytic activities of acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase may be important defects behind the impairment of the transduction mechanisms for nutrient-stimulated insulin release in islets from TPN-infused rats.     

Application of one-step liquid chromatography–electrospray tandem MS/MS and collision-induced dissociation to quantification of ezetimibe and identification of its glucuronated metabolite in human serum: A pharmacokinetic study

A new one-step liquid chromatography–electrospray tandem MS/MS method is described to quantify ezetimibe (EZM) a novel lipid lowering drug in human serum. Also using collision-induced dissociation (CID) of the analyte, identification and chromatographic separation of its major metabolite, ezetimibe glucuronide (EZM-G) is achieved in this study. A thawed serum aliquot of 100 μL was deproteinated by addition of 500 μL methanol containing omeprazole as internal standard (I.S.). Separation of the drug, its metabolite and the I.S. were achieved using acetonitrile–water (70:30, v/v) as mobile phase at flow rate of 0.5 mL/min on a MZ PerfectSil target C18 column. Multiple reaction monitoring (MRM) mode of precursor–product ion transition (408.7 → 272.0 for EZM and 345 → 194.5 for the I.S.) was applied for detection and quantification of the drug while, EZM-G was chromatographically separated and identified using CID. The analytical method was linear over the concentration range of 1–32 ng/mL of EZM in human serum with a limit of quantification of 1 ng/mL. The coefficient variation values of both inter- and intra-day analysis were less than 8% whereas the percentage error was less than 3.7. The validated method was applied in a randomized cross-over bioequivalence study of two different EZM preparations in 24 healthy volunteers.     

Proline-Functionalized Graphene Oxide Nanoparticles (GO–Pro NPs) Mitigate Salt-Induced Adverse Effects on Morpho-Physiological Traits and Essential Oils Constituents in Moldavian Balm (Dracocephalum moldavica L.)

Many methodologies have been established to lessen negative impacts of salinity on plants. Of those methodologies, nanoparticles (NPs) application has achieved great importance thanks to their unique physico-chemical properties. Consequently, formerly respecting encouraging impacts of graphene oxide (GO) and proline (Pro) on different plant processes under non-stress and stress conditions, proline-functionalized graphene oxide nanoparticles “GO–Pro NPs” were synthesized and characterized. Graphite powder, as starting material, was used to synthesize GO using modified Hummers method followed by functionalization of its surface by proline in basic media. Afterward, GO–Pro NPs, GO and Pro, each at 0, 50 and 100 mg L^?1 concentrations with three replications, were applied on Moldavian balm (Dracocephalum moldavica L.) plants to assay their effects under non-stress (0 mM) and salt stress (50 and 100 mM) conditions. GO–Pro NPs and Pro effectively alleviated negative effects of salinity through increasing morphological parameters, photosynthetic pigments, chlorophyll fluorescence parameters, chlorophyll index (SPAD), and membrane stability index (MSI) and decreasing hydrogen peroxide and malondialdehyde, as well. Also application of GO–Pro NPs enhanced proline, antioxidant enzymes activities, and most dominant constituents of essential oil. The highest MSI (48.87%) and proline content (15.36 µM g^?1 FW) were observed in plant treated with GO–Pro NPs (50 mg L^?1) under 100 mM NaCl salinity stress. The GO–Pro NPs treatment at lower dose (50 mg L^?1) could be introduced as the best preservative treatment for Moldavian balm under salt stress. GO application mostly had no effect on the measured parameters announcing it as carrier for Pro to enhance its efficiency. In conclusion, GO–Pro NPs application could promote Moldavian balm performance and essential oil under salinity presenting GO–Pro NPs as new treatment against stress conditions.

     

The HHEX rs1111875A/G gene polymorphism is associated with susceptibility to type 2 diabetes in the iranian population

The illuminating picture of genetic mechanisms underlying the development of type 2 diabetes (T2DM) includes differently accumulated genetic polymorphisms that increase the risk along with environmental factors. A number of single nucleotide polymorphisms (SNPs) are indicated to be linked with T2DM, but also conflicting results have been found. To examine the contribution of these polymorphisms in conferring susceptibility to T2DM, the association of HHEX rs1111875A/G and CDKN2A/B rs10811661C/T common gene polymorphisms with the risk of T2DM in an Iranian population was evaluated. In this study participated 140 patients and 140 controls. Genomic DNA was extracted from samples and genotyping of the polymorphisms was performed by the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) technique. A significant association was found with the G allele (OR = 1.729, CI = 1.184–2.523, P = 0.004) and GG genotype (OR = 2.921, 95% CI = 1.789–4.771, P< 0.001) of the rs1111875A/G SNP for susceptibility to T2DM in the recessive model. Furthermore, compared with the GG genotype, individuals with the GA genotype had a lower risk to develop T2DM (OR = 0.237, 95% CI = 0.137–0.408, P< 0.001) in the additive model. In addition, an association between the polymorphism and BMI in regard to the risk of T2DM was identified. The genotype and allele frequencies of the rs10811661C/T polymorphism did not show a statistically significant association with T2DM in any genetic model. Our results show that the rs1111875A/G polymorphism is an important susceptibility polymorphism for the development of T2DM in the Iranian population. Also, these findings support that this polymorphism is a key genetic risk factor for the development of T2DM in multiple ethnic populations.

     

Ammonia removal from a waste air stream using a biotrickling filter packed with polyurethane foam through the SND process

This paper presents the results of a bench-scale biotrickling filter (BTF) on the removal of ammonia gas from a waste stream using a simultaneous nitrification/denitrification (SND) process. It was found that the developed BTF could completely remove 100 ppm ammonia from a waste stream, with an empty bed retention time of 60 s and 98.4% nitrogen removal through the SND process under the tested conditions. It was elucidated that both autotrophic and heterotrophic bacteria were involved in the nitrogen removal trough the SND process in the BTF. Additionally, the elimination capacity of total nitrogen by the BTF increased from 3.5 to 18.4 g N/m³ h with an inlet load of 20.6 g N/m³ h (73.6%). The findings of this study suggest that the BTF can be operated to attain complete ammonia removal through the SND process, thereby making the treatment of ammonia-laden gas streams both short and cost-effective.     

Occurrence,Molecular Characterization and Vector Transmission of a Phytoplasma Associated with Rapeseed Phyllody in Iran

Symptoms of rapeseed phyllody were observed in rapeseed fields of Fars, Ghazvin, Isfahan, Kerman and Yazd provinces in Iran. Circulifer haematoceps leafhoppers testing positive for phytoplasma in polymerase chain reaction (PCR) successfully transmitted a rapeseed phyllody phytoplasma isolate from Zarghan (Fars province) to healthy rapeseed plants directly after collection in the field or after acquisition feeding on infected rapeseed in the greenhouse. The disease agent was transmitted by the same leafhopper from rape to periwinkle, sesame, stock, mustard, radish and rocket plants causing phytoplasma‐type symptoms in these plants. PCR assays using phytoplasma‐specific primer pair P1/P7 or nested PCR using primers P1/P7 followed by R16F2n/R2, amplified products of expected size (1.8 and 1.2 kbp, respectively) from symptomatic rapeseed plants and C. haematoceps specimens. Restriction fragment length polymorphism analysis of amplification products of nested PCR and putative restriction site analysis of 16S rRNA gene indicated the presence of aster yellows‐related phytoplasmas (16SrI‐B) in naturally and experimentally infected rapeseed plants and in samples of C. haematoceps collected in affected rapeseed fields. Sequence homology and phylogenetic analysis of 16S rRNA gene confirmed that the associated phytoplasma detected in Zarghan rapeseed plant is closer to the members of the subgroup 16SrI‐B than to other members of the AY group. This is the first report of natural occurrence and characterization of rapeseed phyllody phytoplasma, including its vector identification, in Iran.