水土保持耕作法是治理黄土高原地区坡耕地的根本措施

坡耕地所造成的土壤侵蚀,已成为全世界共同关注的问题。黄土高原地区,沟壑纵横,地形破碎,沟深坡陡,是世界上水土流失最强烈的地区。坡耕地的水土流失不仅是造成河流水库淤积的一个重要原因,更重要的是每年要丧失大量的肥沃表土,导致农业减产和土壤退化。一遇暴雨,人民的生命财产将遭受到巨大的威胁。黄土高原地区每年水力侵蚀土层深度达0.2—2cm,每1ha 损失表土120t 左右,损失     

感染流行性出血热病毒家兔病毒血症的研究

本文采用流行性出血热病毒114株实验感染家兔,用免疫荧光法及病毒培养技术研究了家兔病毒血症动态,发现感染后第6天,病毒抗原首先在淋巴细胞及单核细胞中出现;次日,亦可见于粒细胞中,第10—12天的抗原反应较强,第15天则明显减弱至消失。而在红细胞及血小板中始终未见明显的抗原反应。从感染后第3—13天的血浆中分离出病毒;感染后第6—15天,外周血单核细胞病毒分离阳性。结果表明,流行性出血热病毒在接种局部增殖后,侵入血液,并在白细胞中复制增殖,可能使病毒随血循环播散至全身其它组织脏器,造成因血传播引起的靶器官感染。     

氟化物对桑蚕幼虫中肠ATP酶活性影响的电镜细胞化学定位

氟化物对桑蚕幼虫中肠ＡＴＰ酶活性影响的电镜细胞化学定位陈玉银,包焕盛,吴玉澄（浙江农业大学杭州３１００Ｎ）桑蚕Ｂｏｍｂｙｘｍｏｒｉ（Ｌ．）氟中毒导致蚕茧严重减产是目前蚕业界最为关切的问题,有关桑蚕幼虫氟中毒的机理研究也从各方面展开［１１］。已知桑蚕氟...     

福建武夷山甜槠群落能量的研究

在生物量、生产力研究基础上,对武夷山甜槠（Ｃａｓｔａｎｏｐｓｉｓ ｅｙｒｅｉ（Ｃｈａｍ ｐ．ｅｘ Ｂｅｎｔｈ．） Ｔｕｔｃｈ．）群落各组分的热值、群落能量现存量、能量年净固定量以及太阳能转化效率进行了研究。结果表明：（１）甜槠群落各组分样品的干重热值具有一定的差异,树皮热值最高,细根热值最低。（２）甜槠群落的能量现存量达７８０５８４．１ ｋＪ·ｍ － ２,其中地上部分为６７８９１３．８ ｋＪ·ｍ － ２,占总量的８６．９８％ ;地下部分为１０１６７０．３ ｋＪ·ｍ － ２,占１３．０２％ 。（３）甜槠群落的能量年净固定量（１９９２年）为２６８５６．２ ｋＪ·ｍ － ２·ａ－ １,林地太阳光合有效辐射能的转化效率为１．２９６％ 。     

Production of a novel copolyester of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids by Pseudomonas sp. 61-3 from sugars

 Pseudomonas sp. 61-3 (isolated from soil) produced a polyester consisting of 3-hydroxybutyric acid (3HB) and of medium-chain-length 3-hydroxyalkanoic acids (3HA) of C₆, C₈, C₁₀ and C₁₂, when sugars of glucose, fructose and mannose were fed as the sole carbon source. The polyester produced was a blend of homopolymer and copolymer, which could be fractionated with boiling acetone. The acetone-insoluble fraction of the polyester was a homopolymer of 3-hydroxybutyrate units [poly (3HB)], while the acetone-soluble fraction was a copolymer [poly(3HB-co-3HA)] containing both short- and medium-chain-length 3-hydroxyalkanoate units ranging from C₄ to C₁₂:44 mol% 3-hydroxybutyrate, 5 mol% 3-hydroxyhexanoate, 21 mol% 3-hydroxyoctanoate, 25 mol% 3-hydroxydecanoate, 2 mol% 3-hydroxydodecanoate and 3 mol% 3-hydroxy-5-cis-dodecenoate. The copolyester was shown to be a random copolymer of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoate units by analysis of the ¹³C-NMR spectrum. The poly(3HB) homopolymer and poly (3HB-co-3HA) copolymer were produced simultaneously within cells from glucose in the absence of any nitrogen source, which suggests that Pseudomonas sp. 61-3 has two types of polyhydroxy-alkanoate syntheses with different substrate specificities. Received: 9 June 1995/Received last revision: 30 October 1995/Accepted: 6 November 1995     

α-Lipoic acid dependent regeneration of ascorbic acid from dehydroascorbic acid in rat liver mitochondria

Rat liver mitochondria were examined for their ability to reduce dehydroascorbic acid to ascorbic acid in an -lipoic acid dependent or independent manner. The a-lipoic acid dependent reduction was stimulated by factors that increased the NADH dependent reduction of -lipoic acid to dihydrolipoic acid in coupled reactions. Optimal conditions for dehydroascorbic acid reduction to ascorbic acid were achieved in the presence of pyruvate, -lipoic acid, and ATP. Electron transport inhibitors, rotenone and antimycin A, further enhanced the dehydroascorbic acid reduction. The reactions were strongly inhibited by 1 mM iodoacetamide or sodium arsenite. Mitoplasts were qualitatively similar to intact mitochondria in dehydroascorbate reduction activity. Pyruvate dehydrogenase and -ketoglutarate dehydrogenase reduced dehydroascorbic acid to ascorbic acid in an -lipoic acid, coenzyme A, and pyruvate or -ketoglutarate dependent fashion. Dehydroascorbic acid was also catalytically reduced to ascorbic acid by purified lipoamide dehydrogenase in an -lipoic acid (K _0.5=1.4±0.8 mM) and lipoamide (K _0.5=0.9±0.3 mM) dependent manner.     

T cells in murine lupus: propagation and regulation of disease

MRL/Mp-lpr/lpr mice develop a spontaneous lupus syndrome, including hypergammaglobulinemia, autoantibodies, glomerulonephritis, and lymphadenopathy. To investigate the role of lymphocyte subsets in the pathogenesis of disease, lupus-prone MRL mice deficient in T cells, T cells, or both were generated. Mice deficient in T cells developed a partially penetrant lupus syndrome, characterized by lymphadenopathy, elevated levels of class-switched immunoglobulins, an increased incidence of antinuclear antibodies, and immune deposits in kidneys which progressed to renal insufficiency over time. In comparison to wild type animals, T cell-deficient animals developed an accelerated and exacerbated disease phenotype, characterized by accelerated hypergammaglobulinemia and enhanced autoantibody production and mortality. Repertoire analysis of these latter animals identified polyclonal expansion (V) of CD4+B220-cells. Mice lacking both and T cells failed to generate class-switched autoantibodies and immune complex renal disease. First, these findings demonstrate that murine lupus in the setting of Fas-deficiency does not absolutely require the presence of T cells, and they also suggest that a significant basis for MRL/lpr disease, including renal disease, involves T cell-independent, T cell dependent, polyreactive B cell autoimmunity, upon which T cell-dependent mechanisms aggravate specific autoimmune responses. Second, these data indicate that T cells partake in the regulation of systemic autoimmunity, presumably via their effects on CD4+B220-T cells that provide B cell help. Finally, these results demonstrate that MRL/lpr B cells, despite their intrinsic abnormalities, cannot per se cause tissue injury without T cell help.Abbreviations snRNPs small nuclear ribonucleoprotein particles     

酸水解蚕蛹制备复合氨基酸的研究

采用硫酸水解法,以蚕蛹制取复合氨基酸产品,得到氨基酸态氮分别为９．０５％和１３．４５％的食用复合氨基粉和精制复合氨基酸粉。食用复合氨基酸粉含有１８种氨基酸,其中必需氨基酸含量为３９．２％。食用复合氨基酸粉的制备方法经工厂小批量生产证实,其工艺简单易行,适合于中小企业采用,该产品的质量优良,生产成本低廉,具有市场竞争力。     

Characterization of cis-acting elements in light regulation of the nuclear gene encoding the A subunit of chloroplast isozymes of glyceraldehyde-3-phosphate dehydrogenase from Arabidopsis thaliana.

We have characterized cis-acting elements involved in light regulation of the nuclear gene (GapA) encoding the A subunit of chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in Arabidopsis thaliana. Our results show that a 1.1-kb promoter fragment of the GapA gene is sufficient to confer light inducibility and organ specificity in transgenic Nicotiana tabacum (tobacco) plants, using the beta-glucuronidase gene of Escherichia coli as the reporter gene. Deletion analysis indicates that the -359 to -110 bp region of the GapA gene is necessary for light responsiveness. Within this region there are three copies of a decamer repeat (termed the Gap box) having the consensus sequence 5'-CAAATGAA(A/G)A-3', which has not been characterized in the promoter regions of other light-regulated genes. A deletion (to -247) producing loss of one copy of these elements from the GapA promoter reduces light induction by two- to threefold compared with a promoter deletion (to -359) with all three Gap boxes present, while deletion of all three Gap boxes (to -110) abolishes light induction completely. Gel mobility shift experiments using tobacco nuclei as the source of nuclear proteins show that GapA promoter fragments that contain these repeats bind strongly to a factor in the nuclear extract and that binding can be abolished by synthetic competitors consisting only of a monomer or dimer of the Gap box. Furthermore, a trimer, dimer, and monomer of the Gap box show binding activity and, like the authentic GapA promoter-derived probes, show binding activities that are correlated with Gap box copy number. These results strongly suggest that these repeats play important roles in light regulation of the GapA gene of A. thaliana.