用棉籽饼代替花生饼做幼猪蛋白饲料

导言与花生饼相比,棉子饼的总氮含量略低一些,但其蛋白质中的几种主要的必需氨基酸如赖氨酸、蛋氨酸和胱氨酸含量却很高。对于非反刍动物来说,棉子饼应当是理想的蛋白饲料。然而,由于棉子饼中含有棉酚,这是一种有毒的天然多酚物质,因而妨障了它在猪、家禽和兔子饲料中的随意使用。其中,猪对棉酚的毒性尤为敏感。猪食用棉子饼后会导致厌食、呼吸困难、体虚消瘦等症状。人们一直在寻找根除或减少棉饼用于非反刍动物饲料中所导致的棉酚中毒现象,他们分别用不同量的蛋白质、不同质量的蛋白质、含铁添加剂,以及用含微量棉酚的无腺棉子饼等做饲料进行试验,取得了不同程度的进展。在尼日利亚,尽管棉子饼产量很高,由于缺乏信息,故未对其用于猪饲料予以注意。本研究报告确立了棉子饼与花生饼相比,用于断奶后幼猪饲料中的有关参数。     

Invariant chain--a regulator of antigen presentation

MHC class II molecules present internalized antigens to the immune system. They have long been known to associate with a polypeptide called the invariant chain. Recent findings have revealed that this polypeptide performs two functions. First, it prevents class II molecules from binding antigenic peptides at the site of synthesis of class II molecules in the endoplasmic reticulum.Second, it targets class II molecules to their destination in the endocytic pathway, where they pick up antigenic peptides derived from endocytosed antigens. Short sequences in the cytoplasmic portion of the invariant chain serve as subcellular address labels.The functions of the invariant chain help to explain how the immune system divides its defence against foreign pathogens between cytotoxic T cells and antibodies.     

Mechanisms in bradykinin stimulated arachidonate release and synthesis of prostaglandin and platelet activating factor

Regulatory mechanisms in bradykinin (BK) activated release of arachidonate (ARA) and synthesis of prostaglandin (PG) and platelet activating factor (PAF) were studied in bovine pulmonary artery endothelial cells (BPAEC). A role for GTP binding protein (G-protein) in the binding of BK to the cells was determined. Guanosine 5-O- (thiotriphosphate), (GTPtauS), lowered the binding affinity for BK and increased the Kd for the binding from 0.45 to 1.99 nM. The Bmax remained unaltered at 2.25 x 10(-11) mole. Exposure of the cells to aluminium fluoride also reduced the affinity for BK. Bradykinin-induced release of ARA proved pertussis toxin (PTX) sensitive, with a maximum sensitivity at 10 ug/ml PTX. GTPtauS at 100 muM increased the release of arachidonate. The effect of GTPtauS and BK was additive at suboptimal doses of BK up to 0.5 nM but never exceeded the levels of maximal BK stimulation at 50 nM. PTX also inhibited the release of ARA induced by the calcium ionophore, A23187. Phorbol 12-myristate 13-acetate or more commonly known as tetradecanoyl phorbol acetate (TPA) itself had little effect on release by the intact cells. However, at 100 nM it augmented the BK activated release. This was downregulated by overnight exposure to TPA and correlated with down-regulation of protein kinase C (PKC) activity. The down-regulation only affected the augmentation of ARA release by TPA but not the original BK activated release. TPA displayed a similar, but more potent amplification of PAF synthesis in response to both BK or the calcium ionophore A23187. These results taken together point to the participation of G-protein in the binding of BK to BPAEC and its activation of ARA release. Possibly two types of G-protein are involved, one associated with the receptor, the other activated by Ca(2+) and perhaps associated with phospholipase A(2) (PLA(2)). Our results further suggest that a separate route of activation, probably also PLA(2) related, takes place through a PKC catalysed phosphorylation.     

beta-Glucosidase of Penicillium funiculosum. I. Purification

A strain of Penicillium funiculosum, isolated in this laboratory, produced in high yield both endo- and exo-glucanases and beta-glucosidases, which were suitable for the saccharification of cellulosic materials. The isolation of the beta-glucosidase of this organism, which differs from other beta-glucosidases of fungi in its substrate specificity, by preparative electrophoresis, is described in this article. The organism was grown on a lactose-casein medium and the culture filtrate concentrated by ammonium sulfate precipitation and dialysis. Electrophoresis was carried out on large slabs of polyacrylamide gel in an anodicrun in the presence of borate at pH 7. After elution of active fractions, a cathodic run was made at pH 6.0. Two precipitations with ammonium sulfate resulted in a homogeneous enzyme (specific activity 174 IU/mg). A second isozyme was also produced by P. funiculosum on cellulose-wheat bran medium. This isozyme was purified by electrophoresis at pH 7.0 in the absence of borate and was obtained free from other isozymes of beta-glucosidase and cellulases.     

Aspartate glucan, glycine glucan, and serine glucan for the removal of cobalt and copper from solutions and brines

Aspartate glucan, glycine glucan, and serine glucan obtained by reductive amination of oxalacetic acid, glyoxylic acid, and beta-hydroxypyruvic acid, respectively, with polyglucosamine were tested as chromatographic chelating media. Crosslinked glycine glucan exhibited high capacities for cobalt and copper, even in acidic solutions (pH 2.9). Breakthrough points for 10 mg/L solutions through 6.0 x 0.6 cm columns containing 200 mg of polymer were at 1.8 L for both ions; for 1 mg/L solutions, they were at 4.0 and 12.0 L for cobalt and copper, respectively. Crosslinked glycine glucan could remove microgram amounts of cobalt and copper from fluoride and chloride brines. Cobalt and copper could be separated by elution with 0.25M sulfuric acid.     

Conversion of organic acids to h(2) by Rhodospirillaceae grown with glutamate or dinitrogen as nitrogen source

Axenic cultures of Rhodopseudomonas capsulata. Rhodospirillum rubrum, and Rhodomicrobium vannielii grown with glutamate as the nitrogen source converted lactate, acetate, and butyrate to H(2) and CO(2). Conversion rates ranged from 100 to 926 mL H(2) L(r) (-1) day(-1) (where L(r) is the reactor contents), and efficiencies varied from 23 to 100% When grown with N(2), conversion rates up to 760 mL H(2) L(r) (-1) day(-1) and efficiencies up to 100%were achieved. Upon aging, cultures appear to rapidly increase in hydrogen uptake activity and furthermore decrease in nitrogenase activity, both factors leading to a slowdown of hydrogen production. This was particularly the case for diazotrophically grown photobacteria.