根据孢粉资料确定伏尔加地区弗拉阶和法门阶界线

俄罗斯伏尔加格勒伏尔加地区上泥盆统弗拉阶和法门阶的界线以3种剖面类型为代表。第一种类型的界线剖面广泛分布于俄罗斯地台,但两阶之间有沉积间断。第二种类型剖面地层发育较完整,即Volgogradian层直覆于Livendian层之上。前者以Corbulispora viminea-Geminospora vasjamica孢子组合带为特征。第三种类型剖面存在于前里海(Pre-Caspian)凹陷的西侧,是最近根据孢粉资料确定的;地层剖面不完整,在中弗拉阶的Semilukian层有剥蚀面,上覆以不同时代的(弗拉期或法门期)盖层。     

Role of nuclear PKC delta in mediating caspase-3-upregulation in Jurkat T leukemic cells exposed to ionizing radiation

The suppressive role of endogenous regucalcin (RC), which is a regulatory protein of calcium signaling, in the enhancement of protein phosphatase activity (PPA) in the cytosol and nucleus of kidney cortex in calcium-administered rats was investigated. Calcium content in the kidney cortex was significantly increased at 0.5-5 h after a single intraperitoneal administration of calcium chloride solution (10 mg Ca/100 g body weight) to rats. The analysis with Western blotting of RC protein showed that RC levels in the cytosol and nucleus were significantly increased 0.5-5 h after the administration of calcium (10 mg/100 g). PPA toward phosphotyrosine, phosphoserine, and phosphothreonine was found in the cytosol and nucleus of kidney cortex. PPA toward three phosphoamino acids in the cytosol and nucleus was significantly increased by the administration of calcium (10 mg/100 g). The presence of anti-RC monoclonal antibody (25 ng/ml) in the enzyme reaction caused a significant increase in PPA toward phosphotyrosine, phosphoserine, and phosphothreonine in the cytosol and nucleus of kidney cortex in normal rats. The effect of anti-RC monoclonal antibody (25 ng/ml) in increasing PPA toward three phosphoamino acids in the cytosol and nucleus was significantly enhanced in calcium-administered rats. The effect of anti-RC monoclonal antibody (25 ng/ml) in increasing PPA in the cytosol and nucleus of normal rats and calcium-administered rats was completely abolished by the addition of RC (10(- 6) M) in the enzyme reaction mixture. The present study suggests that endogenous RC suppresses the enhancement of PPA in the cytosol and nucleus of kidney cortex in calcium-administered rats.     

Variant mannose-binding lectin alleles are associated with celiac disease

In this study, we investigated the role of mannose-binding lectin (MBL) in celiac disease, by performing genotype analysis for the three point mutations in the first exon of the gene in 117 Italian celiac patients (characterized by flat biopsy and positive for anti-endomysium antibody and human transglutaminase antibodies) and 130 pan-ethnic healthy controls. The frequency of homozygous mutant 0/ 0 was significantly higher in the 117 Italian celiac patients (0.13) than in the 130 pan-ethnic healthy controls (0.05; P=0.0405). An increased frequency of homozygous 0/0 allele was found among patients with celiac disease compared with controls. These results suggest an involvement of MBL in the pathophysiology of celiac disease.     

Nitric oxide synthase-mediated phytoalexin accumulation in soybean cotyledons in response to the Diaporthe phaseolorum f. sp. meridionalis elicitor

Phytoalexin biosynthesis is part of the defense mechanism of soybean (Glycine max) plants against attack by the fungus Diaporthe phaseolorum f. sp. meridionalis (Dpm), the causal agent of stem canker disease. The treatment of soybean cotyledons with Dpm elicitor or with sodium nitroprusside (SNP), a nitric oxide (NO) donor, resulted in a high accumulation of phytoalexins. This response did not occur when SNP was replaced by ferricyanide, a structural analog of SNP devoid of the NO moiety. Phytoalexin accumulation induced by the fungal elicitor, but not by SNP, was prevented when cotyledons were pretreated with NO synthase (NOS) inhibitors. The Dpm elicitor also induced NOS activity in soybean tissues proximal to the site of inoculation. The induced NOS activity was Ca(2+)- and NADPH-dependent and was sensitive to the NOS inhibitors N(G)-nitro-L-arginine methyl ester, aminoguanidine, and L-N(6)-(iminoethyl) lysine. NOS activity was not observed in SNP-elicited tissues. An antibody to brain NOS labeled a 166-kD protein in elicited and nonelicited cotyledons. Isoflavones (daidzein and genistein), pterocarpans (glyceollins), and flavones (apigenin and luteolin) were identified after exposure to the elicitor or SNP, although the accumulation of glyceollins and apigenin was limited in SNP-elicited compared with fungal-elicited cotyledons. NOS activity preceded the accumulation of these flavonoids in tissues treated with the Dpm elicitor. The accumulation of these metabolites was faster in SNP-elicited than in fungal-elicited cotyledons. We conclude that the response of soybean cotyledons to Dpm elicitor involves NO formation via a constitutive NOS-like enzyme that triggers the biosynthesis of antimicrobial flavonoids.     

Enhanced mtDNA repair capacity protects pulmonary artery endothelial cells from oxidant-mediated death

In rat cultured pulmonary arterial (PA), microvascular, and venous endothelial cells (ECs), the rate of mitochondrial (mt) DNA repair is predictive of the severity of xanthine oxidase (XO)-induced mtDNA damage and the sensitivity to XO-mediated cell death. To examine the importance of mtDNA damage and repair more directly, we determined the impact of mitochondrial overexpression of the DNA repair enzyme, Ogg1, on XO-induced mtDNA damage and cell death in PAECs. PAECs were transiently transfected with an Ogg1-mitochondrial targeting sequence construct. Mitochondria-selective overexpression of the transgene product was confirmed microscopically by the observation that immunoreactive Ogg1 colocalized with a mitochondria-specific tracer and, with an oligonucleotide cleavage assay, by a selective enhancement of mitochondrial Ogg1 activity. Overexpression of Ogg1 protected against both XO-induced mtDNA damage, determined by quantitative Southern analysis, and cell death as assessed by trypan blue exclusion and MTS assays. These findings show that mtDNA damage is a direct cause of cell death in XO-treated PAECs.     

Selective fitness of four episomal shuttle-vectors carrying HIS3, LEU2, TRP1, and URA3 selectable markers in Saccharomyces cerevisiae

A comparison of the selective fitness of four 2-microm-based shuttle-plasmids carrying the yeast genes HIS3, LEU2, TRP1, and URA3 was performed. The effect of each marker on long-term growth rate and plasmid maintenance was measured. In selective medium, the LEU2 and URA3 plasmids were maintained at the lowest and the highest levels, respectively, while the HIS3 and TRP1 plasmids were maintained at an intermediate level. In synthetic complete medium, plasmid loss rate was lower for the genes TRP1 and URA3 than for the other two markers, and a similar pattern was observed for cells growing in rich medium. These results were confirmed by competition experiments among transformants with different plasmids in complete and rich media, indicating a different degree of fitness for the markers used. A potential correlation of the energy cost of plasmid maintenance with the secondary DNA structure and the level of expression of the selective markers is also investigated.     

Covalent incorporation of selenium into oligonucleotides for X-ray crystal structure determination via MAD: proof of principle. Multiwavelength anomalous dispersion

Selenium was incorporated into an oligodeoxynucleotide in the form of 2'-methylseleno-uridine (U(Se)). The X-ray crystal structure of the duplex left open bracket d(GCGTA)U(Se)d(ACGC) right open bracket (2) was determined by the multiwavelength anomalous dispersion (MAD) technique and refined to a resolution of 1.3 A, demonstrating that selenium can selectively substitute oxygen in DNA and that the resulting compounds are chemically stable. Since derivatization at the 2'-alpha-position with selenium does not affect the preference of the sugar for the C3'-endo conformation, this strategy is suitable for incorporating selenium into RNA. The availability of selenium-containing nucleic acids for crystallographic phasing offers an attractive alternative to the commonly used halogenated pyrimidines.     

Occurrence of Cu-ATPase in Dictyostelium: possible role in resistance to copper

Dictyostelium discoideum amoebae showed an uncommon resistance to Cu(2+), as pointed out through cell growth rate (EC(50) = 469 +/- 30 microM) and the neutral red cytotoxicity assay (EC(50) = 334 +/- 45 microM). Although no evidence of Cu-inducible metallothionein was found, Cu-dependent ATPase activity was cytochemically detected on pelletted, resin-embedded amoebae. This activity required Cu(2+) in the incubation medium, was sensitive to TPEN, vanadate and temperature, and showed dose-dependent increase after exposure of amoebae to 10-500 microM Cu(2+) for 7 days. Accordingly, immunofluorescence and Western blotting revealed the occurrence of a Cu-inducible, putative homologue of human Menkes (MNK) Cu-P-type ATPase. To verify if Cu-ATPase is involved in copper resistance, amoebae were exposed to low concentrations of Cu(2+) and vanadate followed by the neutral red assay. Exposure to either treatment showed no effect, while a combination caused a dramatic increase of Cu toxicity, possibly depending on Cu-ATPase inhibition.     

Calcium-regulated GTPase activity in the calcium-binding protein calexcitin

Calexcitin (CE) is a calcium-binding protein, closely related to sarcoplasmic calcium-binding proteins, that is involved in invertebrate learning and memory. Early reports indicated that both Hermissenda and squid CE also could bind GTP; however, the biochemical significance of GTP-binding and its relationship to calcium binding have remained unclear. Here, we report that the GTPase activity of CE is strongly regulated by calcium. CE possessed a P-loop-like structure near the C-terminal similar to the phosphate-binding regions in other GTP-binding proteins. Site-directed mutagenesis of this region showed that Gly¹⁸², Phe¹⁸⁶ and Gly¹⁸⁷ are required for maximum affinity, suggesting that the GTP-binding motif is G-N-x-x-[FM]-G. CE cloned from Drosophila CNS possessed a similar C-terminal sequence and also bound and hydrolyzed GTP. GTPase activity in Drosophila CE was also strongly regulated by Ca²⁺, exhibiting over 23-fold higher activity in the presence of 0.3 μM calcium. Analysis of the conserved protein motifs defines a new family of Ca²⁺-binding proteins representing the first example of proteins endowed with both EF-hand calcium binding domains and a C-terminal, P-loop-like GTP-binding motif. These results establish that, in the absence of calcium, both squid and Drosophila CE bind GTP at near-physiological concentrations and hydrolyze GTP at rates comparable to unactivated ras. Calcium functions to increase GTP-binding and GTPase activity in CE, similar to the effect of GTPase activating proteins in other low-MW GTP-binding proteins. CE may, therefore, act as a molecular interface between Ca²⁺ cytosolic oscillations and the G protein-coupled signal transduction.     

Regeneration processes of a boreal forest in Kamchatka with special reference to the contribution of sprouting to population maintenance

We studied regeneration patterns of three tree species Picea ajanensis, Betula platyphylla and Populus tremula from 1998 to 2000 in the Central Depression of the Kamchatka Peninsula. We paid special attention to the contribution of sprouting to their regeneration. P. ajanensis was the only species that regenerated by seedling. In a 40 × 40 m study plot, the density of P. ajanensis saplings < 2.0 cm in diameter at basal area (DBH) was 1132, and this was the highest among the three species studied. The number of saplings 2 cm in DBH declined sharply with size class. The spatial distribution of P. ajanensis saplings (< 2 cm in DBH) showed a significant positive correlation with that of adult trees and a negative correlation with that of gaps. These trends were not changed after re-measurement in 2000, although nearly half of the juveniles had died or been injured during the two years. These results suggest that small Picea saplings prefer habitats under the canopy of adult trees rather than in gaps for establishment. Most small individuals of B. platyphylla were produced from sprouts. The number of saplings in the smallest size class (< 2 cm in DBH) was much less than that of P. ajanensis, although the number of larger individuals did not decrease remarkably. The spatial distribution of B. platyphylla saplings showed a positive correlation with that of adult trunks and a negative correlation with that of canopy trees of P. ajanensis. These results suggest an effective contribution of sprouts to the regeneration of B. platyphylla. P. tremula was the only species that could invade big gaps and produce many root suckers efficiently. There were 181 suckers of P. tremula in the smallest size class (< 2 cm in DBH) in the study plot, although the number of saplings 2 cm in DBH declined abruptly. The spatial distribution of saplings of this species showed a slight positive correlation with that of gaps, and negative correlation with that of adult trees of B. platyphylla, P. ajanensis, and P. tremula. The root suckering strategy of P. tremula might be adaptive under severe conditions in high-latitude regions. Our data suggest, however, that it does not necessarily contribute to regeneration in mature forests. The three component species in this forest did not seem to utilize canopy gaps for regeneration; we suggest that gap dynamics do not work in this forest. The sparse canopy, which is a typical character of forests in high-latitude regions, might be a consequence of high mortalities of seedlings and root suckers inside gaps.