Transplantation of cultured thymic fragments. VI. H-2 recombinant donors

Athymic (nude) mice were transplanted with cultured thymic fragments from syngeneic, allogeneic, and partially allogeneic (recombinant) mice. Lymphocyte proliferation and cytotoxicity in vitro were measured to assess immunologic reconstitution. Transplanted nude mice were immunocompetent whether donor and recipient were disparate for class I, class II, or both H-2 gene types. Furthermore, allotolerance for thymic H-2 class I antigens was achieved independently of class II antigen allotolerance. Class I antigen tolerance was not broken during lymphocyte responses to unrelated alloantigens, ruling out insufficient help as the tolerance mechanism. Splenocytes, isolated from nude mice transplanted with fully allogeneic or syngeneic thymic fragments and stimulated in vitro with trinitrophenyl-modified cells, displayed H-2-restricted, hapten-specific cytotoxicity. Cytotoxic cells from allotolerant mice were restricted to either host or thymic H-2 antigens, depending on the stimulating cell haplotype. Response levels for thymic and host trinitrophenyl-modified cells were comparable. We have shown that allogeneic thymic epithelium transplanted into adult nude mice can induce allotolerance to class I and II H-2 antigens equally, and permits T lymphocyte interaction with cells bearing thymic donor or host H-2 antigens. Our results are consistent with a model wherein T lymphocyte self-receptors retain their genomic repertoire but can be selectively mutated or expanded by appropriate H-2 antigen presentation by the thymus.     

The influence of dolichol, dolichol esters, and dolichyl phosphate on phospholipid polymorphism and fluidity in model membranes

The effect of dolichols, polyprenols, dolichol esterified with fatty acids, and dolichyl phosphate on the structure and fluidity of model membranes was studied using 31P NMR, small-angle x-ray scattering, differential scanning calorimetry, and freeze-fracture electron microscopy. These studies suggest that dolichol and dolichol derivatives destabilize unsaturated phosphatidylethanolamine containing bilayer structures and promote hexagonal II phase formation; high concentrations of dolichol induce lipid structures characterized by "isotropic" 31P NMR and particulate fracture faces; dolichol, contrary to cholesterol, has no effect on the thermotropic behavior of membranes consisting of phosphatidylcholine, while dolichyl-P incorporation abolishes the transition from the gel to liquid crystalline phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine; both dolichol and dolichyl-P increase the fatty acid fluidity in phosphatidylethanolamine mixtures; the effect of dolichol on bilayer structure and fluidity is more pronounced with increasing number of isoprene residues; dolichol esters are only soluble to a limited extent in the bilayer and segregates into domains at low concentrations; the results are consistent with a localization of dolichyl-P in which the phosphate group is oriented to the water interphase. The induction of hexagonal II phase by dolichyl-P may elicit the transmembrane movement of glycosylated lipid intermediate.     

Effects of p,p''-DDT on the Rat Brain Concentrations of Biogenic Amine and Amino Acid Neurotransmitters and Their Association with p,p''-DDT-Induced Tremor and Hyperthermia

Male, Fischer strain 344 adult rats were given various doses (25-100 mg/kg) of p,p'-DDT by oral gavage, and levels of biogenic amines, their metabolites, and amino acid neurotransmitters, tremor activity, and rectal temperature were measured at several intervals (2, 5, 12, and 24 h) after dosing. Dose-related increases in rectal temperature and in tremor activity were observed at 50-100 mg/kg 12 h after dosing. Tremorigenic doses of DDT increased the 5-hydroxyindoleacetic acid (5-HIAA) level in hypothalamus, brainstem, and striatum, whereas doses of 75 and 100 mg/kg increased the 3-methoxy-4-hydroxyphenylglycol (MHPG) level in hypothalamus and brainstem and the 3,4-dihydroxyphenylacetic acid level in striatum. Six amino acids were assayed in the brainstem, hypothalamus, and striatum; aspartate and glutamate levels were increased only in brainstem at 25-100 mg/kg. No consistent changes in concentrations of taurine, glutamine, glycine, or gamma-aminobutyric acid were observed in any of the regions assayed. Time-related increases in rectal temperature were seen 2-12 h after dosing, and the presence of tremor was observed 5-12 h after dosing; for both the time of peak effect was at 12 h. The DDT-induced hyperthermia and tremor were associated with dose- and time-related increases in levels of 5-HIAA, MHPG, aspartate, and glutamate. It is suggested that an increase in the turnover rate of 5-hydroxytryptamine (5-HT) may be responsible for the DDT-induced hyperthermia, whereas increases in the metabolism of 5-HT and norepinephrine may be involved in the tremor.     

翅果油树根瘤超微结构及其内生菌的观察

作者用光学显微镜,透射电镜和扫描电镜对翅果油树(Eldaeagnus mollis D.)根瘤侵染细胞的超微结构及其内生菌的形态进行了观察研究。翅果油树根瘤中的内生菌具有五种不同的发育形态:菌丝、固氮泡囊、孢囊、孢囊孢子和拟类菌体。内生菌的这些不同形态以及它们在共生固氮中的作用,本文也作了讨论。     

柱孢鱼腥藻的铁蛋白与棕色固氮菌的钼铁蛋白的交叉互补作用

纯化的柱孢鱼腥藻铁蛋白能够与棕色固氮菌的钼铁蛋白有效地交叉反应,展现较高的活性。此异源交叉反应的乙炔还原比活及放氢比活,分别是蓝藻同源互补比活的83.8及66.7％。比较藻铁蛋白与菌钼铁蛋白异源交叉反应及藻固氮酶组分之间的同源反应的动力学特点时发现,铁蛋白对钼铁蛋白的最佳克分子比数前者(异源交叉反应)较后者(藻同源反应)为高,前者为5,后者为1;但反应的时间进程两者差别不大。     

Sugar cane bagasse as a possible source of fermentable carbohydrates. I. Characterization of bagasse with regard to monosaccharide, hemicellulose, and amino acid composition

Individual monosaccharides present in bagasse hemicellulose were determined using HPLC and other chromatographic procedures. The presence of higher oligomers of the monosaccharides could also be determined. No single procedure can separate and identify all the naturally occurring monosaccharides. The pentosan fraction of bagasse wa successfully hydrolyzed and extracted with 5% (m/v)HCl, and the rate of release of individual monosaccharides was determined. Xylose was the main component in the hydrolyzates, while glucose, arabinose, and galactose present in the side chains of the pentosans were initially released at a fast rate. This treatment resulted in obtaining 229 mg/g xylose (85% of theoretical maximum) and 44 mg/g glucose from bagasse. Only arabinose (2.8 mg/g) and galactose (0.75 mg/g) was also present in detectable quantities. A total of 309 mg monosaccharides were obtained from 1 g of bagasse by this treatment. The results indicated that hydrolysis conditions for specific plant materials depend on the composition of the specific material being utilized. A part of the pentosan fraction (77.1%) was hydrolyzed at a high rate, while 22.9% was more stable and hydrolyzed more slowly. Although 39.8% dry bagasse could be obtained in solution by treatment with dilute alkali, only about 72% of the available hemicelluloses could be extracted in this way if the bagasse was not delignified beforehand. Amino acids and peptides or proteins were also extracted to very much the same with the alkali.     

甜菊不同叶龄细胞结构及其甜菊糖甙含量分布的研究

本文报道甜菊(Stevia rebaudiana Bertoni)不同叶龄细胞结构与甜菊糖苷含量分布。应用电镜技术观察表明,现蕾期成叶细胞内具有内含物丰富的巨大液泡,这些内含物呈大小不一的颗粒或小泡。应用差速离心法,对甜菊成叶的叶肉细胞进行亚细胞分离,并对各部分进行甜菊糖苷的提取与微量测定。结果表明,甜菊糖苷主要存在于12000g的上清液(这部分主要包括液泡内含物和可溶性细胞质)。结合细胞结构和细胞化学研究结果,表明细胞质是合成UDPG的主要场所,在甜菊糖苷合成中具有重要作用。对不同叶龄叶片甜菊糖苷测定表明,现蕾期成叶的甜菊糖苷含量最高。从甜菊不同叶龄细胞结构和甜菊糖苷含量测定结果,现蕾期是甜菊叶片收割的最适时期。     

油松茎次生结构中树脂道的结构分布和发育的研究

油松茎的次生结构中树脂道存在于次生维管组织中。其中,次生木质部内具有水平的和垂直的两类树脂道,而次生韧皮部内则仅有水平的树脂道。两类树脂道都由上皮细胞和鞘细胞包围着胞间道构成,其中木质部内的树脂道具有死鞘细胞,而韧皮部中的则都系生活细胞。在心材中,垂直树脂道形成拟侵填体。在次生木质部内,垂直树脂道常分布于早材的外部区域和最初形成的晚材中,它们与水平树脂道连接,腔道贯通,从而形成二维网状结构。垂直树脂道来源于纺锤状原始细胞的衍生细胞,而水平树脂道来源于射线原始细胞,两者都以裂生方式发生。