Cyclin‐dependent kinase‐activating kinases CDKD;1 and CDKD;3 are essential for preserving mitotic activity in Arabidopsis thaliana

For the full activation of cyclin‐dependent kinases (CDKs), not only cyclin binding but also CDK phosphorylation is required. This activating phosphorylation is mediated by CDK‐activating kinases (CAKs). Arabidopsis has four genes showing similarity to vertebrate‐type CAKs, three CDKDs (CDKD;1‐CDKD;3) and one CDKF (CDKF;1). We previously found that the cdkf;1 mutant is defective in post‐embryonic development, even though the kinase activities of core CDKs remain unchanged relative to the wild type. This raised a question about the involvement of CDKDs in CDK activation in planta. Here we report that the cdkd;1 cdkd;3 double mutant showed gametophytic lethality. Most cdkd;1‐1 cdkd;3‐1 pollen grains were defective in pollen mitosis I and II, producing one‐cell or two‐cell pollen grains that lacked fertilization ability. We also found that the double knock‐out of CDKD;1 and CDKD;3 caused arrest and/or delay in the progression of female gametogenesis at multiple steps. Our genetic analyses revealed that the functions of CDKF;1 and CDKD;1 or CDKD;3 do not overlap, either during gametophyte and embryo development or in post‐embryonic development. Consistent with these analyses, CDKF;1 expression in the cdkd;1‐1 cdkd;3‐1 mutant could not rescue the gametophytic lethality. These results suggest that, in Arabidopsis, CDKD;1 and CDKD;3 function as CAKs controlling mitosis, whereas CDKF;1 plays a distinct role, mainly in post‐embryonic development. We propose that CDKD;1 and CDKD;3 phosphorylate and activate all core CDKs, CDKA, CDKB1 and CDKB2, thereby governing cell cycle progression throughout plant development.     

Substitution in Amino Acid 70 of Hepatitis C Virus Core Protein Changes the Adipokine Profile via Toll-Like Receptor 2/4 Signaling

Background & Aims

It has been suggested that amino acid (aa) substitution at position 70 from arginine (70R) to glutamine (70Q) in the genotype 1b hepatitis C virus (HCV) core protein is associated with insulin resistance and worse prognosis. However, the precise mechanism is still unclear. The aim of this study was to investigate the impact of the substitution at position 70 in HCV core protein on adipokine production by murine and human adipocytes.

Methods

The influence of treatment with HCV core protein (70R or 70Q) on adipokine production by both 3T3-L1 and human adipocytes were examined with real-time PCR and enzyme-linked immunosorbent assay (ELISA), and triglyceride content was also analyzed. The effects of toll-like receptor (TLR)2/4 inhibition on IL-6 production by 3T3-L1 induced by HCV core protein were examined.

Results

IL-6 production was significantly increased and adiponectin production was reduced without a change in triglyceride content by treatment with 70Q compared to 70R core protein in both murine and human adipocytes. IL-6 induction of 3T3-L1 cells treated by 70Q HCV core protein was significantly inhibited with anti-TLR2 antibody by 42%, and by TLR4 inhibitor by 40%.

Conclusions

Our study suggests that extracellular HCV core protein with substitution at position 70 enhanced IL-6 production and reduced adiponectin production from visceral adipose tissue, which can cause insulin resistance, hepatic steatosis, and ultimately development of HCC.     

Streptococcus panodentis sp. nov. from the oral cavities of chimpanzees

Three strains TKU9, TKU49 and TKU50^T, were isolated from the oral cavities of chimpanzees (Pan troglodytes). The isolates were all gram‐positive, facultative anaerobic cocci that lacked catalase activity. Analysis of partial 16S rRNA gene sequences showed that the most closely related species was Streptococcus infantis (96.7%). The next most closely related species to the isolates were S. rubneri, S. mitis, S. peroris and S. australis (96.6 to 96.4%). Based on the rpoB and gyrB gene sequences, TKU50^T was clustered with other member of the mitis group. Enzyme activity and sugar fermentation patterns differentiated this novel bacterium from other members of the mitis group streptococci. The DNA G + C content of strain TKU50^T was 46.7 mol%, which is the highest reported value for members of the mitis group (40–46 mol%). On the basis of the phenotypic characterization, partial 16S rRNA gene and sequences data for two housekeeping gene (gyrB and rpoB), we propose a novel taxa, S. panodentis for TKU 50^T (type strain = CM 30579^T = DSM 29921^T), for these newly described isolates.     

Application of chimeric glucanase comprising mutanase and dextranase for prevention of dental biofilm formation

Water‐insoluble glucan (WIG) produced by mutans streptococci, an important cariogenic pathogen, plays an important role in the formation of dental biofilm and adhesion of biofilm to tooth surfaces. Glucanohydrolases, such as mutanase (α‐1,3‐glucanase) and dextranase (α‐1,6‐glucanase), are able to hydrolyze WIG. The purposes of this study were to construct bi‐functional chimeric glucanase, composed of mutanase and dextranase, and to examine the effects of this chimeric glucanase on the formation and decomposition of biofilm. The mutanase gene from Paenibacillus humicus NA1123 and the dextranase gene from Streptococcus mutans ATCC 25175 were cloned and ligated into a pE‐SUMOstar Amp plasmid vector. The resultant his‐tagged fusion chimeric glucanase was expressed in Escherichia coli BL21 (DE3) and partially purified. The effects of chimeric glucanase on the formation and decomposition of biofilm formed on a glass surface by Streptococcus sobrinus 6715 glucosyltransferases were then examined. This biofilm was fractionated into firmly adherent, loosely adherent, and non‐adherent WIG fractions. Amounts of WIG in each fraction were determined by a phenol‐sulfuric acid method, and reducing sugars were quantified by the Somogyi–Nelson method. Chimeric glucanase reduced the formation of the total amount of WIG in a dose‐dependent manner, and significant reductions of WIG in the adherent fraction were observed. Moreover, the chimeric glucanase was able to decompose biofilm, being 4.1 times more effective at glucan inhibition of biofilm formation than a mixture of dextranase and mutanase. These results suggest that the chimeric glucanase is useful for prevention of dental biofilm formation.     

Zinc homeostasis and signaling in health and diseases

The essential trace element zinc (Zn) is widely required in cellular functions, and abnormal Zn homeostasis causes a variety of health problems that include growth retardation, immunodeficiency, hypogonadism, and neuronal and sensory dysfunctions. Zn homeostasis is regulated through Zn transporters, permeable channels, and metallothioneins. Recent studies highlight Zn’s dynamic activity and its role as a signaling mediator. Zn acts as an intracellular signaling molecule, capable of communicating between cells, converting extracellular stimuli to intracellular signals, and controlling intracellular events. We have proposed that intracellular Zn signaling falls into two classes, early and late Zn signaling. This review addresses recent findings regarding Zn signaling and its role in physiological processes and pathogenesis.     

Different Impacts of Neck Circumference and Visceral Obesity on the Severity of Obstructive Sleep Apnea Syndrome

Our aim was to investigate the significance of neck circumference (NC) on the presence and severity of obstructive sleep apnea (OSA) syndrome independent of visceral fat (VF) obesity. A total of 219 subjects with suspected OSA underwent a complete polysomnography (PSG) study, along with the measurement of NC, and total body fat (TF) and VF levels (VFLs) measured by bioelectrical impedance analysis. We proposed NC divided by height (NC/H) as the simple index for height‐corrected NC in Japanese subjects. NC/H exhibited a significantly stronger correlation than NC per se with BMI (r = 0.781 vs. 0.675, P = 0.0178), TF (r = 0.531 vs. 0.156, P < 0.0001), and VF (r = 0.819 vs. 0.731, P = 0.0203), indicating that NC/H is a better indicator of visceral obesity than NC per se. Interestingly, despite the strong correlation between NC/H and VFL, VFL was significantly associated with the apnea‐hypopnea index (AHI) ≥5, ≥15, and ≥30, but not with ≥40 or ≥50, whereas NC/H was significantly associated with higher AHI values, i.e., AHI ≥50 but not with lower AHI value. Furthermore, multiple regression analyses revealed that VFL and NC/H were independently associated with the square root of AHI (AHI^0.5) levels in obese and nonobese patients, respectively. In conclusion, NC is associated with the severity of OSA independently of visceral obesity, especially in nonobese patients.     

Polyamines promote the development of embryonal-suspensor masses and the formation of somatic embryos in <Emphasis Type="Italic">Picea glehnii</Emphasis>

Effects of polyamines on the development of embryonal-suspensor masses (ESMs) and the formation of somatic embryos were examined in an effort to improve the frequency of somatic embryogenesis in Picea glehnii. Exogenous spermidine at 100 and 300 μM promoted the elongation of suspensors and the formation of somatic embryos. Exogenous putrescine at 100 μM increased the number of somatic embryos and decreased the time required for formation of somatic embryos. Thus, exogenous polyamines improved the maturation capacity of ESMs and promoted the formation of somatic embryos in P. glehnii. Light microscopy revealed that ESMs with high maturation capacity consisted of the three following cells: round or oval cells, elongated cells, and protean cells. These components might be related to the capacity for formation of somatic embryos.     

Development of an ultrasensitive immunoassay using affinity maturated antibodies for the measurement of rodent insulin

The measurement of plasma insulin is important for clinical diagnosis of diabetes and for preclinical research of metabolic diseases, especially in rodent models used in drug discovery research for type 2 diabetes. Fasting immunoreactive insulin (F-IRI) concentrations are used to calculate the homeostasis model assessment ratio (HOMA-R), an index of insulin sensitivity. However, even the most sensitive commercially available enzyme-linked immunosorbent assay (ELISA) kits cannot measure the very low F-IRI concentrations in normal rats and mice. Therefore, we sought to develop a new rodent insulin ELISA with greater sensitivity for low F-IRI concentrations. Despite repeated efforts, high-affinity antibodies could not be generated by immunizing mice with mouse insulin (self-antigen). Therefore, we generated two weak monoclonal antibodies (13G4 and 26B2) that were affinity maturated and used to develop a highly sensitive ELISA. The measurement range of the sandwich ELISA with the affinity maturated antibodies (13G4m1 and 26B2m1) was 1.5 to 30,000 pg/ml, and its detection limit was at least 10 times lower than those of commercially available kits. In conclusion, we describe the development of a new ultrasensitive ELISA suitable for measuring very low plasma insulin concentrations in rodents. This ELISA might be very useful in drug discovery research in diabetes.     

Habitat associations with topography and canopy structure of tree species in a tropical montane forest on Mount Kinabalu,Borneo

Habitat associations with topography and canopy structure of 42 abundant tree species were studied in a 2.74-ha plot of tropical montane forest on Mount Kinabalu, Borneo. Many of these species belong to the same higher taxa including eight families and four genera. Analysis of intraspecific spatial distributions for stems ≥ 10 cm diameter revealed that 28 species (including all six species of Fagaceae) showed aggregated distributions at the 100-m² and/or 400-m² scales, and that 20 species showed habitat associations with topography by torus-translation tests; 17 species showed both characteristics. Species' associations with the local canopy structure were characterized by crown position index (CPI), which was defined relative to neighbour trees. The CPI differed greatly among individual stems at 10–40 cm diameter, and 19 species showed significantly different frequencies of crowns exposed vertically versus those shaded beneath the canopy. Mean growth rates at 10–40 cm diameter and size distributions of species were not related to topographic associations, but were explained by the associations with canopy structure; species with more exposed crowns grew faster and had less positively skewed distributions. Diversity in habitat associations was manifest between two genera (Syzygium and Tristaniopsis) in the family Myrtaceae and among species in these genera, but was less evident in other families and two genera (Garcinia and Lithocarpus). This revised version was published online in June 2006 with corrections to the Cover Date.