西藏特有种温泉蛇在四川理塘县发现

最近在四川西部理塘县海拔 370 0～ 4 15 0m高山沼泽草地采到 4号 (3雄 1雌 )过去仅知我国西藏高原才有分布的温泉蛇。其鳞被各部分及数量均与西藏分布的温泉蛇一致 ,但与西藏标本尾下鳞单双不定的唯一区别是四川标本均呈双行 ,这可能与所测量四川标本数量较少 (仅 4号 )有关。作者认为这一发现有利于证明青藏高原隆起的地质学问题 ,及其对高原上动物演化发展影响的观点 ,因为西藏高原本体及四川西部高原都属于青藏高原的范围 !     

四川美姑县大风顶国家级自然保护区小型兽类生物多样性分析

为评价美姑大风顶国家级自然保护区小型兽类多样性,利用香农一威纳多样性指数和一种基于信息测度的GF指数。经计算,香农一威纳多样性指数表明：农田一耕地为主的生境类型的小型兽类,以四川短尾鼩、高山姬鼠、黄胸鼠和社鼠为主要的群落组成,其物种多样性指数(H)和均匀性指数(J)分别是1．1374和0．8599;原始森林为主的生境类型的小型兽类,以川西白腹鼠和食虫类为主,其各多样性指数H=0．3307和J=0．3465;高山草甸为主的生境类型的小型兽类,以鼠兔类和姬鼠类为主,其H=0．3704和J=0．3881。为了得到补充和对照,参考了该区小型兽类已有的资料运用G-F指数评价其生物物种多样性,首先计算科间多样性(F)和属间多样性(G),然后,再利用F指数和G指数的比值进行标准化处理,得出GF指数值,说明保护区小型兽类种属间的多样性。该区小型兽类D-F指数为0．6977,即小型兽类种属间多样性较高,但和香农一威纳指数评定多样性有一定差异。保护区的建设还需进一步加强,包括人为干扰在内的一切干扰尚需排除。     

浙江庆元槠栲林的群落学特征

利用样方法对浙江省庆元县槠栲林的群落学特征进行了分析.该槠栲林主要分为甜槠[Castanopsis eyrei (Champ. ex Benth.) Tutch.]林[含甜槠-木荷(Schima superba Gardn. et Champ.)林]、栲(C. fargesii Franch.)林、米槠[C. carlesii (Hemsl.) Hayata]林、罗浮栲(C. fabrii Hance)林、南岭栲(C. fordii Hance)林5个类型,并对各个群落类型的特征作了详细的描述.年龄结构分析表明:甜槠林和米槠林为金字塔形结构; 南岭栲林为纺锤形结构; 罗浮栲林和甜槠-木荷林部分年龄结构缺失; 栲林既有金字塔形,也有年龄结构缺失的类型.从幼苗和幼树数量分析,大多类型更新情况良好,罗浮栲林和南岭栲林更新情况较差.     

Contrasting patterns of mussel abundance at neighbouring sites: does recruitment limitation explain the absence of mussels on Cook Strait (New Zealand) shores?

Wellington Harbour (New Zealand) supports large populations of mussels (Aulacomya maoriana, Mytilus galloprovincialis and Perna canaliculus), whereas these species are absent from Cook Strait shores only a few km away. The density of planktonic mussel larvae and their recruitment rates to artificial substrates were investigated at harbour (with mussels) and Cook Strait (no mussels) sites to determine if a diminished or a zero larval supply and/or settlement explains the absence of mussels from Cook Strait shores. At both locations, larvae were collected from the plankton approximately monthly between September 1998 and February 2000, and recruitment rates to artificial substrates were estimated between March 2000 and February 2001. Planktonic larval densities were almost an order of magnitude greater within the harbour than at coastal sites (mean (±S.D.) density was 982 m⁻³ (±1478) with a peak density in September 1998 of 4207 m⁻³, compared with 106 (±94) and 381 m⁻³, respectively, in March 1999). Larval recruitment at harbour sites was also significantly greater than at coastal sites (mean (±S.D.) recruitment density was 2169 m⁻² (±4207) with a peak of ca. 211,425 m⁻² in July 2000, compared with 88 m⁻² (±86) and ca. 3700 m⁻², respectively, in February 2001). It has been suggested that “bottom up” regulation of community structure, principally via a diet of particulates low in organic matter, is the explanation for the absence of suspension feeding mussels from Cook Strait sites [Helson, J. G., 2001. An investigation into the absence of mussels (Perna canalicus, Aulacomya maoriana and Mytilus galloprovincialis) from the South Coast of Wellington, New Zealand. Unpublished PhD thesis, Victoria University of Wellington, 183 pp.], but given that planktonic larval supply and recruitment rates are much reduced at coastal sites, these data may also be important in explaining the absence. Whether current levels of recruitment are sufficient to maintain an adult population is at present unknown and requires further examination.     

The relationship of 4-aminobutyric acid metabolism to ammoniagenesis in renal cortex

Mitochondrial 4-aminobutyrate aminotransferase in rat kidney can utilize pyruvate as the acceptor for the amino group of 4-aminobutyrate. Renal 4-aminobutyrate aminotransferase activity at saturating equimolar concentration of 4-aminobutyrate and 5 mM pyruvate is 42.8 ± 2.5 μmol/g protein per h (mean ± S.E.M.) or 70% of 4-aminobutyrate aminotransferase activity with equimolar α-ketoglutarate. 4-Aminobutyrate aminotransferase in brain does not transaminate with pyruvate. Since pyruvate is an important mitochondrial metabolite in kidney, net disposal of glutamate via the 4-aminobutyrate pathway is possible. The renal 4-aminobutyrate pathway in the rat has other distinctive features when compared with the pathway in rat brain. Most inhibitors of rat neuronal glutamate decarboxylase were ineffective against the renal form of the enzyme, but 20 mM semicarbazide inhibited the latter form by 80% (P < 0.001) in vitro and reduced renal 4-aminobutyrate content by 75% (P < 0.001) in vivo. In the presence of 20 mM semicarbazide, ammoniagenesis by rat renal cortex slices incubated in 1 mM glutamine was inhibited 26% (P < 0.01). Semicarbazide was proportionately less effective (15% inhibition) when ammoniagenesis was stimulated (+243%) in slices prepared from chronically acidotic animals, and was no deterrant to ammoniagenesis when non-acidotic slices were incubated in supraphysiologic concentrations of 10 mM glutamine. We conclude that whereas integrity of the renal 4-aminobutyrate pathway may contribute to glutamate disposal and thus ammoniagenesis under physiologic conditions, the pathway is a passive participant in the overall process of ammoniagenesis.     

Cord-factor analogs: synthesis of 6,6'-di-O-mycoloyl- and -corynomycoloyl-(alpha-D-galactopyranosyl alpha-D-galactopyranoside)

Appropriate solvolysis of 2,3,2',3'-tetra-O-benzyl-4,6,4', 6'-tetra-O-mesyl-alpha,alpha-trehalose gave 2,3,2',3' -tetra-O-benzyl-(alpha-D-galactopyranosyl alpha-D-galactopyranoside) (2). Selective tosylation or mesylation of 2 respectively gave the 6, 6'-ditosylate (3) and 6,6'-dimesylate (4), the structures of which were confirmed by the 1H-n.m.r. spectra of the corresponding 4,4'-di-O-acetyl derivatives. Treatment of 3 with potassium mycolate in toluene, and subsequent hydrogenolysis, gave the 6'-mycolate 6-tosylate derivative. Treatment of 3 with potassium mycolate or potassium corynomycolate in hexamethylphosphoric triamide, followed by catalytic hydrogenolysis, yielded the respective cord-factor analogs 6,6'-di-O-mycoloyl-(alpha-D-galactopyranosyl alpha-D-galactopyranoside) and 6,6'-di-O-corynomycoloyl-(alpha-D-galactopyranosyl alpha-D-galactopyranoside). The same 6,6'-diesters were obtained from the 6,6'-dimesylate 4. Putative 4,6-anhydro-6'-monomycolates are also described.     

Direct stimulatory effect of ethanol on 17 alpha-hydroxylase activity of rat testis interstitial cells

These studies examined the in vitro effects of ethanol on the activities of steroidogenic enzymes involved in the conversion of progesterone to testosterone in 10,000xg supernatants of rat testis interstitial cells. 17 alpha-Hydroxylase activity of interstitial cells increased in direct relation to the final concentration of ethanol added (2.2 - 652 mM); however, 17,20-lyase and 17-ketosteroid reductase activities were not affected. These studies, together with a previous study, where we showed that testosterone accumulation by intact interstitial cells was inhibited by ethanol when either progesterone or 17 alpha-hydroxyprogesterone (but not androstenedione) were added as exogenous substrates, suggest that ethanol, in addition to stimulating 17 alpha-hydroxylase activity, inhibits the normal coupling of 17, 20-lyase activity with the 17-ketosteroid reductase activity.     

Subcellular localization of enterokinase (Enteropeptidase EC 3.4.21.9) in rat small intestine

The subcellular localization of enterokinase is controversial. In this study, enterokinase was extracted from a soluble fraction and a brush border fraction of rat small intestine by differential centrifugation. The soluble fraction contained 41% of the initial enterokinase activity while the brush border fraction contained only 4.6% of the initial activity. In contrast, alkaline phosphatase monitored as a brush border marker, yielded 26.3 in the brush border fraction and only 6% in the soluble fraction. Further separation of the soluble fraction on a Sepharose 4B column revealed three peaks of enterokinase activity. One small peak (3%) of a bound enzyme (M_r, 2·10^?6) and two larger peaks of free enzyme (M_r, 3·10⁵ and 9·10⁵). In contrast, alkaline phosphatase major fraction was in a high molecular weight peak of bound enzyme. When the brush border fraction was chromatographed only a single peak of bound enterokinase and alkaline phosphatase were found. In the lower part of the small intestine, no brush border-bound enterokinase was found, while the peak of alkaline phosphatase was the same as in the upper intestine. These data suggest that enterokinase activity in the rat intestine is mainly in a free form localized in the mucin and soluble fraction and to a negligible extent in the brush border.     

Helper factor(s) augment in vitro induction of tumor-specific immunity

Helper factor supernatants derived from alloantigen-activated murine lymphocytes augment the generation of cytolytic effector cells to syngeneic tumor cells. The effects are dose dependent and vary with the syngeneic tumor cell system studied. The effector cells are specific for the tumor-associated antigen(s) utilized for their induction, and are sensitive to lysis with anti-T-cell serum (Thy 1.2), but are insensitive to lysis with an allogeneic anti-NK-cell serum. The helper factor supernatants also augment the production of a “tissue-culture-induced” cytolytic cell (cultured NK cell), which is resistant to treatment with both anti-Thy 1.2 and anti-NK serum.