coq7/clk-1 regulates mitochondrial respiration and the generation of reactive oxygen species via coenzyme Q

coq7/clk-1 was isolated from a long-lived mutant of Caenorhabditis elegans, and shows sluggish behaviours and an extended lifespan. In C. elegans and Saccharomyces cerevisiae, coq7/clk-1 is required for the biosynthesis of coenzyme Q (CoQ), an essential co-factor in mitochondrial respiration. The clk-1 mutant contains dietary CoQ(8) from Escherichia coli and demethoxyubiquinone 9 (DMQ9) instead of CoQ(9). In a previous study, we generated COQ7-deficient mice by targeted disruption of the coq7 gene and reported that mouse coq7/clk-1 is also essential for CoQ synthesis, maintenance of mitochondrial integrity and neurogenesis. In the present study, we rescued COQ7-deficient mice from embryonic lethality and established a mouse model with decreased CoQ level by transgene expression of COQ7/CLK-1. A biochemical analysis showed a concomitant decrease in CoQ(9), mitochondrial respiratory enzyme activity and the generation of reactive oxygen species (ROS) in the mitochondria of CoQ-insufficient mice. This implied that the depressed activity of respiratory enzymes and the depressed production of ROS may play a physiological role in the control of lifespan in mammalian species and of C. elegans.     

Fc Receptor-Mediated Phagocytosis,Superoxide Production and Calcium Signaling of β2 Integrin-Deficient Bovine Neutrophils

Fc receptor for immunoglobulin G-mediated phagocytosis, superoxide production and intracellular calcium ([Ca²⁺]ⁱ) signaling of complement receptor type 3 (CR3)-deficient neutrophils from a heifer with leukocyte adhesion deficiency (BLAD) were compared to those of control heifers. The mean phagocytic activity of IgG-coated yeasts and aggregated bovine IgG (Agg-IgG)-induced superoxide production of CR3-deficient neutrophils were 10% and 77.9%, respectively, of those of control neutrophils. The [Ca²⁺]ⁱ signals in CR3-deficient neutrophils stimulated with Agg-IgG or concanavalin A were different with mean peak [Ca²⁺]ⁱ concentrations of 78% and 41.9%, respectively, of those of control neutrophils. These findings suggest that Fc receptor-mediated neutrophil functions are closely dependent on the presence of CR3 (CD11b/CD18) on the neutrophil cell surfaces.     

Geographic patterns of endemism and speciation in amphibians and reptiles of the Ryukyu Archipelago, Japan, with special reference to their paleogeographical implications

This paper analyzes the phylogeographical patterns of amphibian and reptile lineages distributed in the Ryukyu islands south of the Tokara Gap on the basis of relevant distributional data and phylogenetic hypotheses hitherto published. Results indicate the numerical dominance of highly relict lineages in the central Ryukyus, and the occurences of a few more or less relict lineages in the Miyako Group as well. On the other hand, most species and subspecies endemic to the Yaeyama Group or to the Yaeyama and Miyako Groups are considered to be direct consequences of vicariance with adjacent regions. Three major hypotheses regarding the Cenozoic paleogeography of the central and the southern Ryukyus are examined in the light of the present results and a modified hypothesis is proposed accordingly.     

A possible association between basic amino acids of position 13 of DRB1 chains and autoimmune hepatitis

Fifty-one patients with autoimmune hepatitis have been studied for HLA association by conventional serology and also by modified polymerase chain reaction-restriction fragment lenght polymorphism (PCR-RFLP) genotyping.HLA-DR4 was significantly associated with autoimmmune hepatitis (46 of 51 patients, 90.2%). DNA typing of the DRB1 gene for 43 DR4-positive patients by using the PCR-RFLP technique revealed that of 43 patients, 33 had DRB1 ^* 0405 (Dw15), five had DRB1 ^* 0406 (DwKT2), four had DRB1 ^* 0403 (Dw13a), two had DRB1 ^* 0401 (Dw4), two of 43 had DRB1 ^* 0407 (Dw13b) and one had DRB1 ^* 0408 (Dw14b). Thus, there was no significant difference in Dw frequencies between DR4-positive patients and DR4-positive healthy subjects. These findings suggest that the DR4-specific sequence (Val 11 and His 13 at amino acid positions 11 and 13, respectively), but not particular Dw-associated DR4 sequence, in the first domain of the DRB1 chain contributes to susceptibility to autoimmune hepatitis among Japanese. Interestingly, all five of the DR4-negative patients had the DR2 specificity (DRB1 ¹⁵⁰² or 1601). Taken together, these results imply that the basic amino acids at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), are most important for determining the predisposition to autoimmune hepatitis. Address correspondence and offprint requests to: M. Ota.     

Chemiluminescence enzyme immunoassay of dehydroepiandrosterone and its sulfate using peroxidase as label

We report a highly sensitive enzyme immunoassay for dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) using horseradish peroxidase as the label enzyme. Separation of free and bound DHEA-peroxidase conjugate was by insolubilized antibody, prepared by coupling purified IgG of goat anti-rabbit IgG serum with Sepharose 4B or a polystyrene tube. The enzyme activity was measured by the chemiluminescence reaction using luminol and hydrogen peroxide as substrate. The faint chemiluminescence was measured by a photon counter. The sensitivity was 25 pg/assay tube for DHEA and 100 pg/assay tube for DHEA-S. Upon comparison, results obtained by radioimmunoassay and this method showed good agreement; r = 0.86 for free DHEA, r = 0.92 for acid-hydrolyzed DHEA-S and r = 0.91 for solvolyzed DHEA-S. The present method is applicable in the routine determination of DHEA and DHEA-S in biological fluid.     

Female reproductive cycles in the northernmost populations of the two gekkonid lizards,Hemidactylus frenatus andLepidodactylus lugubris

Lepidodactylus lugubris, a parthenogenetic gekkonid lizard of possible tropical origin, occurs on Kita-Daitojima Island of the Ryukyu Archipelago and lays eggs almost throughout the year. The oviposition season of the sympatric population of another primary tropical, but bisexual gecko,Hemidactylus frenatus, is confined to between April and September. Laboratory experiments indicate that the hatching ratio of the egg reduces with the decrease of incubation temperature in both species. Some eggs ofL. lugubris develop at 14°C of ambient temperature, wheras eggs ofH. frenatus always die at temperatures of 18°C or lower. Examinations of stomach contents and fat body mass in the monthly samples suggest that food availability is not severely low for the geckos even during the winter, rejecting the previous assumption that food stress suppresses vitellogenesis inH. frenatus. No other environmental factors that may induce reproductive seasonality as phenotypic physiological responses were detected either. Tropical populations ofH. frenatus andL. lugubris are known to lack distinct annual reproductive cyclicity. Thus, it is probable that the East AsianH. frenatus has evolved the winter quiescence of reproduction, presumably due to the poor embryonic tolerance of low temperatures. The absence of such seasonality in the sympatricL. lugubris seems to be attributable to its clonal nature which predicts the low genetic variability of the population from the colonization stage.     

Differential Effects of Prostaglandin E1 and Prostaglandin E2 on Growth and Differentiation of Murine Myeloid Leukemic Cell Line,M1

Effects of prostaglandins (PGs) of the E series on growth and differentiation of murine myeloid leukemic cell line M1 were studied. PGE₁, but not PGE₂, inhibited the growth of M1 cells. PGE₂ neither inhibited nor augmented the antiproliferative effect of PGE₁. PGE₁ augmented the differentiation of M1 cells into macrophage-like cells induced by interleukin 6. PGE₂, however, did not exhibit any effect on the differentiation. PGE₁ caused a marked increase in intracellular cAMP level in M1 cells, whereas PGE₂ had no effect. These results indicate that M1 cells are able to respond only to PGE₁. Radiolabeled PGE₁ binding experiments, however, revealed that there was no specific binding in M1 cells, suggesting that the cells express low numbers of receptors or very low affinity receptors specific for PGE₁. Stable agonists of PGI₂, iloprost, cicaprost or carbacyclin, also potently inhibited the growth of M1 cells. These findings suggest that PGE₁ as well as PGI₂ may play a role in the differentiation of monocyte-macrophage lineage cells.     

Regulatory role of cinnamyl alcohol dehydrogenase in the formation of guaiacyl and syringyl lignins

The substrate specificities of cinnamyl alcohol dehydrogenase (CAD) of angiosperms and gymnosperms were examined using coniferaldehyde and sinapaldehyd