大口径金属密封活套法兰

本实用新型涉及一种用于高真空密封连接的大口径（大于２５０ｍｍ）全金属密封活套法兰。本实用新型是将活套外环位于肩环的密封刀口侧的联接螺栓孔边缘与其内腔的间隔厚度控制在１～２ｍｍ，并使内腔内圆与肩环外圆间隙保持在０．１～０．３ｍｍ。本实用新型的密封活套法兰密封刀口为凹型。本实用新型的活套外环位于肩环的密封刀口侧的联接螺栓孔边缘与其内腔的最佳间隔厚度为１．１ｍｍ，这种结构可使其有最好的效果。

Physico-chemical properties of alkaline phosphatases released by a planktonic crustacean, Daphnia magna (Cladocera)

Our studies investigated the physico-chemical properties of alkaline phosphatase excreted by D. magna. This cladoceran mainly released alkaline phosphatase, though it also released a small amount of acid phosphatase. The alkaline phosphatase showed a broad pH optimum (8.05-10.0), and had a broad optimum temperature (30-35 degrees C) with a temperature coefficient (Q(10)) of 2.45. The K-m of the enzyme is 0.15 +/- 0.02 mM when p-nitrophenyl phosphate is used as a substrate, and the V-max is 0.43 +/- 0.01 mu M pNP mg(-1) DW h(-1). Even though alkaline phosphatase had been incubated in chloroform saturated with WC medium for 13 days, its activity was 54% that of the original. The enzyme was strongly inactivated by EDTA, and appeared to be zinc dependent. The alkaline phosphatase activity remained constant when D. magna was fed different quantities of Chlorella sp. The sensitivity of D. magna phosphatase activity to phosphate was time-dependent. During the first 16 hrs, the enzyme was insensitive to phosphate addition, after 24 hrs incubation the enzyme became sensitive to phosphate addition.

Population dynamics of the water mite Unionicola arcuata (Unionicolidae) in the freshwater bivalve Cristaria plicata (Unionidae) in Poyang Lake, eastern China

Population dynamics of the water mite Unionicola arcuata were investigated in the freshwater bivalve Cristaria plicata during the period from January to December 2002 in Poyang Lake, East China. A pattern of seasonal variation was observed, with prevalence and abundance peaking in early spring and autumn. The number of mites in individual hosts was significantly correlated with the size, but not with the sex, of bivalves. The change in infection level of mites on different infection sites in C. plicata was significant, with > 58% of the mites found on the outer and inner gills, indicating that U. arcuata shows site preference.

Cloning and characterization of a new multi-stress inducible metallothionein gene in Tetrahymena pyriformis

A new multi-stress-inducible metallothionein (MT) gene isoform has been cloned and characterized from the ciliate Tetrahymena pyriformis. Both the 5'- and 3'-UT regions of the Tp-MT2 gene are very different from the previously reported Tp-MT1 isoform in this organism and from other described MT genes in Tetrahymena pigmentosa and Tetrahymena thermophila. The putative protein sequence of Tp-MT2 contains cysteine clusters with characteristics of the typical Tetrahymena Cd-inducible MT genes. However, the sequence has a special feature of four intragenic tandem repeats within its first half, with a conserved structural pattern x(5/8)CCCx(6)CCx(6)CxCxNCxCCK. To investigate the transcriptional activities of both Tp-MT2 and Tp-MT1 genes toward heavy metals (Cd, Hg, Cu, Zn) and H2O2, the mRNA levels of these two isoforms were evaluated by means of real-time quantitative PCR. Results showed that Tp-MT2 had a higher basal expression level than Tp-MT1 and both genes were induced by Cd, Hg, Cu, and Zn ions after short exposure (I h), although to different extents. Cd was the most effective metal inducer of both two isoforms, but the relative expression level of Tp-MT2 was much lower than that of Tp-MT1. Different expression patterns were also shown between the two genes when treated with Cd over a period of 24 h. We suggest that TpMT-1 plays the role of a multi-inducible stress gene, while TpMT-2 may have a more specific function in basal metal homeostasis although it may have undergone a functional differentiation process. The putative functional significance and evolutionary mode of the TpMT-2 isoform are discussed. (c) 2006 Elsevier GmbH. All rights reserved.

Acrossocheilus spinifer, a new species of barred cyprinid fish from south China (Pisces : Teleostei)

Acrossocheilus spinifer sp. nov. is described from the river basins in Fujian Province and the Han Jiang basin in Guangdong Province, south China. It is one of the barred Acrossocheihis species sharing five or six vertical bars on the flanks, with each bar being two scales in width. Acrossocheilus spinifer sp. nov. is morphologically most similar to Acrossocheilus wenchowensis. but distinguished from it by: a colour pattern of all vertical bars extending ventrally to the second scale row below the lateral line, and having the second bar placed posterior to the base of the last simple dorsal-fin ray, a blunt snout; and a stout, last simple dorsal-fin ray. Acrossocheilus spinifer sp. nov. resembles Acrossocheilus kreyenbergii and Acrossocheilus stenotaeniatus with which it shares a stout, last simple dorsal-fin ray with a serrated posterior edge, but is separated from both species by having a narrow median interruption in the lower lip, a lower jaw fully covered by the lower lip when viewed ventrally and the second vertical bar placed posterior to the base of the last simple dorsal-fin ray. The absence of a longitudinal stripe extending along the lateral line on the flanks in males readily distinguishes A. spinifer sp. nov. from Four other species, namely Acrossocheilus fasciatus, Acrossocheilus paradoxus, Acrossocheilus parallens, and Acrossocheilus jishouensis. (c) 2006 The Authors Journal compilation (c) 2006 The Fisheries Society of the British Isles.

EST-based identification of genes expressed in the hypothalamus of male orange-spotted grouper (Epinephelus coioides)

The orange-spotted grouper, Epinephelus coioides, is an important marine aquaculture fish, but its large-scale aquaculture has been hindered by the rarity of natural males because it is a protogynous hermaphroditic fish. Hypothalamus-pituitary-gonad is an important endocrine axis in regulating reproduction and sex differentiation. To reveal the molecular mechanism of hypothalamic physiological functions, we performed he studies on identification of genes expressed in the hypothalamus of male orange-spotted grouper using EST and RT-PCR strategy. A total of 1006 ESTs were sequenced, and 402 (39.96%) clones were identified as known genes and 604 (60.04%) as unknown genes. The 402 clones of known gene products represent transcripts of 18 1 genes. Moreover, the expression patterns of 26 unknown genes were analyzed in various tissues, such as liver, kidney, spleen, fat, heart, muscle, pituitary, hypothalamus, telencephalon, cerebellum, midbrain, medulla oblongata, ovary and testes. Five different categories of expression patterns were observed from them. Several unknown ESTs, such as DN551996, DN551998, DN552082, and DN552070, were detected to be hypothalamus-specific, brains-specific, or hypothalamus and gonad-specific genes. Interestingly, DN551996, not only exhibiting expression differences between ovary and testis, but also showing sex-dependent differences in hypothalamus of grouper, might play significant role in grouper reproduction or sex inversion. Further functional studies on these genes will provide more information on molecule regulation mechanism of sex inversion in groupers. (c) 2006 Elsevier B.V All fights reserved.

Effects of the phytoplanktivorous silver carp (Hypophthalmichthys molitrixon) on plankton and the hepatotoxic microcystins in an enclosure experiment in a eutrophic lake, Lake Shichahal in Beijing

The responses of nutrients, water transparency, zooplankton, phytoplankton and microcystins to a gradient of silver carp biomass (0, 18, 55, 110 g/m(3)) were assessed using enclosures in Lake Shichahai (Beijing). Picophytoplankton biomass increased with increasing fish stocking density (r=0.64, p=0.09). Silver carp significantly depressed zooplankton biomass, and thus, zooplankton grazing was too low to control phytoplankton. Intracellular microcystin (MC) content in the enclosures was correlated only to Microcystis biomass in the present study. Microcystis spp. biomass and intracellular microcystins content were much higher in lake water than those of enclosures with and without stocking fish. Stocking of silver carp could be an appropriate in highly productive Lake Shichahai, which naturally lacks of large cladoceran zooplankton. A fish stocking density of 55 g/m(3) was most efficient at controlling Microcystis blooms and increasing water clarity. Mean extracellular MC concentration in the lake water was almost the same with that of the enclosures with fish. (c) 2006 Elsevier B.V. All rights reserved.

Integration of double-fluorescence expression vectors into zebrafish genome for the selection of site-directed knockout/knockin

Production of zebrafish by modifying endogenous growth hormone (GH) gene through homologous recombination is described here. We first constructed the targeting vectors pGHT1.7k and pGHT2.8k, which were used for the knockout/knockin of the endogenous GH gene of zebrafish, and injected these two vectors into the embryos of zebrafish. Overall, the rate of targeted integration with the characteristic of germ line transmission in zebrafish was 1.7x10(-6). In one experimental patch, the integrating efficiency of pGHT2.8k was higher than that of pGHT1.7k, but the lethal effect of pGHT2.8k was stronger than that of pGHT1.7k. The clones with the correct integration of target genes were identified by a simple screening procedure based on green fluorescent protein (GFP) and RFP dual selection, which corresponded to homologous recombination and random insertion, respectively. The potential homologous recombination zebrafish was further bred to produce a heterozygous F-1 generation, selected based on the presence of GFP. The potential targeted integration of exogenous GH genes into a zebrafish genome at the P-0 generation was further verified by polymerase chain reaction and Southern blot analysis. Approximately 2.5% of potential founder knockout and knockin zebrafish had the characteristic of germ line transmission. In this study, we developed an efficient method for producing the targeted gene modification in zebrafish for future studies on genetic modifications and gene functions using this model organism.

Akrokolioplax, a new genus of Southeast Asian labeonine fishes (Teleostei : Cyprinidae)

Akrokolioplax, new genus, is erected for the reception of Epalzeorhynchos bicornis Wu, 1977. It shares with the remaining species of Epalzeorhynchos what have usually been called "rostral lateral lobes" on the snout, which are non-homologous structures used to distinguish the two genera from all other Labeoninae genera. Akrokolioplax and Epalzeorhynchos differ in the position and structure of these lobes, and also in the morphology of the oromandibular structures. A detailed redescription is also provided for the type species of this monotypic genus, A. bicornis. It is presently known from the upper Salween River (=Nu Jiang in Chinese) basin in Yunnan (South China), Myanmar and Thailand.

Identification of differentially expressed genes in Tetrahmena thermophila in response to dichlorodiphenyltrichloroethane (DDT) by suppression subtractive hybridization

The insecticide dichlorodiphenyltrichloroethane (DDT) is persistent in the environment, and continues to cause health problems. Tetrahymena has potential as a model organism for assaying low levels of DDT and for analysing the mechanisms of its toxicity. We constructed the suppression subtractive hybridization library of T thermophila exposed to DDT, and screened out 90 Expressed Sequence Tags whose expressions were significantly up- or downregulated with DDT treatment. From this, a series of important genes related to the DDT metabolism and detoxification were discovered, such as P450 gene, glutathione S-transferase gene and sterol carrier protein 2 gene. Furthermore, their expressions under different concentrations of DDT treatment were detected by real-time fluorescent quantitative PCR. The results show that Tetrahymena is a relevant and useful model organism for detecting DDT in the environment and for discovering biomarkers that can be used to develop specific bio-reporters at the molecular and genomic levels.

Reproductive seasonality and maturity of male Neophocaena phocaenoides asiaeorientalis in captivity: A case study based on the hormone evidence

To provide hormone evidence on reproductive seasonality and maturity of the Yangtze finless porpoise, the authors monitored the monthly variations of serum reproductive hormones of a male Yangtze finless porpoise in captivity via radioimmunoassay from 1997 to 2003. It was demonstrated that the immature animal had a serum T level of 28-101ngdL -1 (6552ngdL -1 ), reached puberty with the serum T concentration ranging between 250 and 590ngdL -1 (390130ngdL -1 ), and attained reproductive maturity when the serum T level went beyond 1120180ngdL -1 in the breeding season. The body length growth of the animal showed a pattern similar to the serum T variations during its adolescent period from the age of 4 to 6 years. Moreover, the serum T concentration of the male porpoise exhibited significant seasonal variations, indicating that its breeding season may start as early as March and end as late as September.