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。     

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％ 。     

Stable carbon isotopes as indicators of increased water use efficiency and productivity in white spruce (Picea glauca (Moench) Voss) seedlings

The relationship among water use efficiency (WUE), productivity and carbon isotopic composition (δ¹³C) in white spruce (Picea glauca (Moench) Voss) seedlings was investigated. Sixteen hundred seedlings representing 10 controlled crosses were planted in the field in individual buried sand-filled cylinders. The soil water content in the cylinders was measured using time domain reflectometry over two growing seasons and seedling water use determined by water balance. Two watering treatments were imposed: irrigation and dry land. There was significant (1.6–2.0%c) genetic variation in needle δ¹³C. Ranking of crosses in terms of δ¹³C was generally maintained over watering treatments and there was not a significant genetic versus environmental interaction. There was a positive correlation between δ¹³C and both intrinsic and long-term WUE (more positive δ¹³C with increased WUE) and between δ¹³C and productivity, suggesting a correlation due to variation in photosynthetic capacity. Root to shoot ratios did not increase in water-stressed plants, indicating that responses to drought were primarily at the level of gas exchange, rather than through morphological changes. Our results indicate that it should be possible to use δ¹³C as a surrogate for WUE and to select white spruce genotypes for high WUE without compromising yield.     

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     

兔核移植胚胎起始发育的超微结构研究

对兔核移植胚胎起始发育的超微结构变化进行电镜观察,并与供体桑椹胚细胞,受体卵母细胞及同期正常受精胚胎的超微结构进行比较,“原核”期兔核移植胚胎的超微结构明显不同于供体桑椹胚细胞及受体卵母细胞的超微结构,而与同期正常受精胚胎相似,但有些核移植胚胎中皮质反应,及核仁和线粒体中出电子致密的网眼结构,与正常受精卵存在差别,分裂至２－细胞期时,与正常２－细胞胚超微结构更相似,结果提示,兔胚胎细胞核移植后,供     

猪精子凝集素的纯化,性质及其作用

用胎球蛋白－Ｓｅｐｈａｒｏｓｅ亲和层析和凝胶过滤层析从精子和精浆中分离纯化了猪精子凝集素（简称ＢＳＬ）。ＢＳＬ的血凝活性只被若干糖蛋白和聚糖所抑制。ＢＳＬ的分子量为５６ｋｄ,由分子量分别为１３．６ｋｄ（β）和１６．０ｋｄ（α）的两个不同的亚基以α１β３所组成。ＢＳＬ为糖蛋白,含中性糖３．２％,不含唾液酸。用ＥＬＩＳＡ法测定猪精子中ＢＳＬ的含量及分布,表明７０％嵌入在精子膜中,２５％结合在精子表面,     

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。