Sulfonylurea receptor type 1 knock-out mice have intact feeding-stimulated insulin secretion despite marked impairment in their response to glucose

The ATP-sensitive potassium channel is a key molecular complex for glucose-stimulated insulin secretion in pancreatic beta cells. In humans, mutations in either of the two subunits for this channel, the sulfonylurea type 1 receptor (Sur1) or Kir6.2, cause persistent hyperinsulinemic hypoglycemia of infancy. We have generated and characterized Sur1 null mice. Interestingly, these animals remain euglycemic for a large portion of their life despite constant depolarization of membrane, elevated cytoplasmic free Ca(2+) concentrations, and intact sensitivity of the exocytotic machinery to Ca(2+). A comparison of glucose- and meal-stimulated insulin secretion showed that, although Sur1 null mice do not secrete insulin in response to glucose, they secrete nearly normal amounts of insulin in response to feeding. Because Sur1 null mice lack an insulin secretory response to GLP-1, even though their islets exhibit a normal rise in cAMP by GLP-1, we tested their response to cholinergic stimulation. We found that perfused Sur1 null pancreata secreted insulin in response to the cholinergic agonist carbachol in a glucose-dependent manner. Together, these findings suggest that cholinergic stimulation is one of the mechanisms that compensate for the severely impaired response to glucose and GLP-1 brought on by the absence of Sur1, thereby allowing euglycemia to be maintained.     

Mg-chelatase H subunit affects ABA signaling in stomatal guard cells,but is not an ABA receptor in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Mg-chelatase H subunit (CHLH) is a multifunctional protein involved in chlorophyll synthesis, plastid-to-nucleus retrograde signaling, and ABA perception. However, whether CHLH acts as an actual ABA receptor remains controversial. Here we present evidence that CHLH affects ABA signaling in stomatal guard cells but is not itself an ABA receptor. We screened ethyl methanesulfonate-treated Arabidopsis thaliana plants with a focus on stomatal aperture-dependent water loss in detached leaves and isolated a rapid transpiration in detached leaves 1 (rtl1) mutant that we identified as a novel missense mutant of CHLH. The rtl1 and CHLH RNAi plants showed phenotypes in which stomatal movements were insensitive to ABA, while the rtl1 phenotype showed normal sensitivity to ABA with respect to seed germination and root growth. ABA-binding analyses using ³H-labeled ABA revealed that recombinant CHLH did not bind ABA, but recombinant pyrabactin resistance 1, a reliable ABA receptor used as a control, showed specific binding. Moreover, we found that the rtl1 mutant showed ABA-induced stomatal closure when a high concentration of extracellular Ca²⁺ was present and that a knockout mutant of Mg-chelatase I subunit (chli1) showed the same ABA-insensitive phenotype as rtl1. These results suggest that the Mg-chelatase complex as a whole affects the ABA-signaling pathway for stomatal movements.     

Two types of maternal care for juveniles observed in Caprella monoceros Mayer, 1890 and Caprella decipiens Mayer, 1890 (Amphipoda: Caprellidae)

Spatial and seasonal patterns in phytoplankton and zooplankton communities of Lake St. Clair from June through September, 1984 are described. Phytoplankton biomass averages 586 µg l^-1 with the Diatomae and Chrysophyceae predominating. Zooplankton biomass averages 663 µg l^- with small bosminid Cladocera being the most abundant organisms. Lake St. Clair zooplankton biomass is second only to that of Lake Erie amongst the St. Lawrence Great Lakes. Biomass size spectra are typical in structure for mesotrophic lakes but low explained variance in the annual normalized spectrum is indicative of a perturbed system. Since 1972/1973 there appears to have been a slight decrease in zooplankton abundance in the lake accompanied by a shift from dominance of rotifers to dominance of cladocerans. We hypothesize that high flushing rate and seasonal variability coupled with contaminant loadings have resulted in a plankton community reduced in taxonomic diversity and dominated by small-bodied species.     

Angiotensin II and III suppress food intake via angiotensin AT(2) receptor and prostaglandin EP(4) receptor in mice

Intracerebroventricularly administered angiotensin (Ang) II and III dose-dependently suppressed food intake in mice and their anorexigenic activities were inhibited by AT(2) receptor-selective antagonist. Ang II did not suppress food intake in AT(2) receptor-knockout mice, while it did significantly in wild-type and AT(1) receptor-knockout mice. The suppression of food intake in AT(1) receptor-knockout mice was smaller than that in wild-type. The anorexigenic activities of Ang II and III were also blocked by a selective antagonist for prostaglandin EP(4) receptor. Taken together, centrally administered Ang II and III may decrease food intake through AT(2) receptor with partial involvement of AT(1) receptor, followed by EP(4) receptor activation, which is a novel pathway regulating food intake.     

Involvement of inducible costimulator-B7 homologous protein costimulatory pathway in murine lupus nephritis

Inducible costimulator (ICOS)-B7 homologous protein (B7h) is a new member of the CD28-B7 family of costimulatory molecules that regulates T cell-dependent humoral immune responses. In this study, we examined the involvement of this costimulatory pathway in the development and progression of lupus in NZB/W F(1) mice. Expression of ICOS on T cells was enhanced with disease progression, whereas B7h expression on B cells was down-regulated. Administration of anti-B7h mAb before the onset of renal disease significantly delayed the onset of proteinuria and prolonged survival. Blockade of B7h effectively inhibited all subclasses of IgG autoantibody production and accumulation of both Th1 and Th2 cells. Hypercellularity and deposition of IgG and C3 in glomeruli were significantly reduced. B7h blockade after the onset of proteinuria prevented the disease progression and improved the renal pathology. Our results demonstrated the involvement of the ICOS-B7h costimulatory pathway in the pathogenesis of lupus nephritis, and the blockade of this pathway may be beneficial for the treatment of human systemic lupus erythematosus.     

Transient Elastography-Based Liver Profiles in a Hospital-Based Pediatric Population in Japan

Background & Aims

The utility of transient elastography (FibroScan) is well studied in adults but not in children. We sought to assess the feasibility of performing FibroScans and the characteristics of FibroScan-based liver profiles in Japanese obese and non-obese children.

Methods

FibroScan examinations were performed in pediatric patients (age, 1–18 yr) who visited Osaka City University Hospital. Liver steatosis measured by controlled attenuation parameter (CAP), and hepatic fibrosis evaluated as the liver stiffness measurement (LSM), were compared among obese subjects (BMI percentile ≥90%), non-obese healthy controls, and non-obese patients with liver disease.

Results

Among 214 children examined, FibroScans were performed successfully in 201 children (93.9%; median, 11.5 yr; range, 1.3–17.6 yr; 115 male). CAP values (mean±SD) were higher in the obese group (n = 52, 285±60 dB/m) compared with the liver disease (n = 40, 202±62, P<0.001) and the control (n = 107, 179±41, P<0.001) group. LSM values were significantly higher in the obese group (5.5±2.3 kPa) than in the control (3.9±0.9, P<0.001), but there were no significant differences in LSM between the liver disease group (5.4±4.2) and either the obese or control group. LSM was highly correlated with CAP in the obese group (ρ = 0.511) but not in the control (ρ = 0.129) or liver disease (ρ = 0.170) groups.

Conclusions

Childhood obesity carries a high risk of hepatic steatosis associated with increased liver stiffness. FibroScan methodology provides simultaneous determination of CAP and LSM, is feasible in children of any age, and is a non-invasive and effective screening method for hepatic steatosis and liver fibrosis in Japanese obese children.     

Wolbachia infections in world populations of bean beetles (Coleoptera: Chrysomelidae: Bruchinae) infesting cultivated and wild legumes

Wolbachia endosymbionts are widespread among insects and other arthropods, often causing cytoplasmic incompatibility and other reproductive phenotypes in their hosts. Recently, possibilities of Wolbachia-mediated pest control and management have been proposed, and the bean beetles of the subfamily Bruchinae are known as serious pests of harvested and stored beans worldwide. Here we investigated Wolbachia infections in bean beetles from the world, representing seven genera, 20 species and 87 populations. Of 20 species examined, Wolbachia infections were detected in four species, Megabruchidius sophorae, Callosobruchus analis, C. latealbus and C. chinensis. Infection frequencies were partial in M. sophorae but perfect in the other species. In addition to C. chinensis described in the previous studies, C. latealbus was infected with two distinct Wolbachia strains. These Wolbachia strains from the bean beetles were phylogenetically not closely related to each other. Among world populations of C. chinensis, some Taiwanese populations on a wild leguminous plant, Rhynchosia minima, exhibited a peculiar Wolbachia infection pattern, suggesting the possibility that these populations comprise a distinct host race or a cryptic species.     

Properties of NACP/alpha-synuclein and its role in Alzheimer's disease

The precursor of the non-amyloid beta/A4 protein (non-Abeta) component of Alzheimer's disease amyloid (NACP)/alpha-synuclein is the human homologue of alpha-synuclein, a member of a protein family which includes alpha-, beta- and gamma-synuclein. This protein is thought to be involved in neuronal plasticity because of its unique expression, mainly in the telencephalon during maturation. Consequently, disarrangement of NACP/alpha-synuclein might disrupt synaptic activity, resulting in memory disturbance. Previous studies have shown that damage to synaptic terminals is closely associated with global cognitive impairment and is an early event in the pathogenesis of Alzheimer's disease. Although the relationship between synaptic damage and amyloidogenesis is not clear, some proteins at the synaptic site have been implicated in both neuronal alteration and amyloid formation. Indeed, abnormal accumulation of both NACP/alpha-synuclein and Abeta precursor protein occurs at synapses of Alzheimer's patients. Other evidence suggests that NACP/alpha-synuclein is a component of the Lewy bodies found in patients with Parkinson's disease or dementia with Lewy bodies, and that a point mutation in this protein may be the cause of familial Parkinson's disease. Consequently, abnormal transport, metabolism or function of NACP/alpha-synuclein appears to impair synaptic function, which induces, at least in part, neuronal degeneration in several neurodegenerative diseases.     

Coenzyme specificity of enzymes in the oxidative pentose phosphate pathway of Gluconobacter oxydans

The coenzyme specificity of enzymes in the oxidative pentose phosphate pathway of Gluconobacter oxydans was investigated. By investigation of the activities of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) in the soluble fraction of G. oxydans, and cloning and expression of genes in Escherichia coli, it was found that both G6PDH and 6PGDH have NAD/NADP dual coenzyme specificities. It was suggested that the pentose phosphate pathway is responsible for NADH regeneration in G. oxydans.