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71.
72.
A baculovirus expression vector was constructed with the tissue plasminogen activator (TPA) cDNA under the control of the viral polyhedrin promoter. After infection of insect cells with the recombinant baculovirus, active TPA was secreted into the medium in which these cells were grown. TPA was isolated from the conditioned media using metal chelate affinity chromatography followed by immunoaffinity purification using mouse monoclonal anti-human TPA coupled to Sepharose. Sodium dodecyl sulfate-gel electrophoresis under reducing conditions and sequence analysis of recombinant human TPA have revealed a two-chain form of the enzyme. The N-terminal amino acid was identified to be serine, indicating that it was processed at its N-terminus by the insect cell culture in a manner similar to that observed for mammalian cells. The relative specific activity of recombinant TPA from insect cells is comparable to that of Bowes melanoma TPA standard. Its activity is stimulated in the presence of fibrinogen fragments, but by a factor about 2.3-fold lower than the Bowes melanoma TPA. The apparent molecular weight of recombinant TPA from insect cells was about 60K by fibrin agar activity gels, suggesting less complex glycosylation than recombinant TPA from mammalian cells.  相似文献   
73.
An extracellular chitosanase produced by Rhodotorula gracilis CFR-1 that catalyses a limited degradation of chitosan with no detectable generation of glucosamine or reducing groups was identified. Ultracentrifugation, polyacrylamide gel electrophoresis and gel permeation studies suggest that chitosan of average molecular mass 36000 Da was reduced by the enzymic catalysis to nearly one-fourth this size without further hydrolysis of the products. The enzyme, produced constitutively by this yeast, was partially purified and some of its properties were studied.  相似文献   
74.
Egg yolk, a large proportion of the egg, was studied for the preparation ofN-acetylneuraminic acid (Neu5Ac). The delipidated hen egg yolk (DEY; 500 kg containing 0.2% w/w, Neu5Ac) was hydrolysed with HCl (pH 1.4) at 80 °C and neutralized with NaOH (pH 6.0). The mixture was filtered and electrodialysed until the conductivity was 240 µS cm–1. The filtrate was applied on a column of Dowex HCR-W2 (20–50 mesh), followed by a column of Dowex 1-X8 (200–400 mesh). The latter column was washed with water, and then eluted with a linear gradient of HCO2H (0–2m). The eluates containing Neu5Ac were concentrated using a reverse osmosis membrane and, finally, rotary evaporated at 40 °C. The residue was then lyophilized to yield 500 g Neu5Ac. The purity of Neu5Ac was >98% (TBA method). HPLC, NMR spectroscopy and TLC chromatography of the product obtained from the DEY showed that Neu5Ac was the sole derivative present in egg yolk. The DEY, a byproduct from egg processing plants, was found to be an excellent source for the large-scale preparation of Neu5Ac.Abbreviations Neu5Ac N-acetylneuraminic acid - Neu5Gc N-glycolylneuraminic acid - DEY delipidated egg yolk - HPLC high performance liquid chromatography - TLC thin layer chromatography - NMR nuclear magnetic resonance - IR infrared spectroscopy Presented at the 11th International Symposium on Glycoconjugates, Toronto, Canada.  相似文献   
75.
Summary We have recently reported that autologous tumor-specific cytotoxic T lymphocyte (CTL) lines and clones can be developed from lymphocytes infiltrating ovarian malignant ascites (TAL). In this study, we investigated the biological effects of tumor necrosis factor (TNF) in the induction, expansion, long-term proliferation and lytic function of CD8+ TAL. TNF up-regulated the IL-2 receptor (IL-2R) chain (Tac antigen) on the surface of CD3+ CD8+ CD4 TAL, enhanced the proliferation of autologous tumor-specific CTL, and potentiated their lytic function in long-term cultures. Furthermore, in the induction and expansion phase of CD8+ TAL, the presence of TNF was associated with a selective increase in CD8+ IL-2R+ (Tac+) cells, and subsequent decrease in CD4+ IL-2R+ (Tac+) cells. These results suggest that the observed facilitation of the outgrowth of CD8+ cells in TAL cultures may be due, at least in part, to the up-regulation of IL-2R, and indicate the usefulness of TNF in the analysis of signalling in autologous tumor-reactive CTL.  相似文献   
76.
Several investigations have been made for the heat flow problems in skin and subdermal tissues under normal physiological and atmospheric conditions. This paper considers the existence of a malignant tumour in the underlying tissues of epidermis of a human body. The surrounding tissues are assumed to have normal physiological functions, namely self-controlled metabolic activity, variable blood flow and perspiration. For the malignant portion the metabolic activity is taken to be continuous and uncontrolled. The effect of this factor is studied on the temperature profiles of the skin.  相似文献   
77.
The effect of dimethoate on gingival and uteral collagen crosslinking was studied in normal and high protein diets fed female albino rats. The gingival and uteral samples were collected from all the groups of rats and percent reversibility of neutral salt soluble collagen gel and the solubility of insoluble collagen in KCNS or urea were determined. The analysis of gingival and uteral samples showed alpha 1 and alpha 2 sub units of neutral salt soluble collagen appreciably increased beta chains and aldehyde content significantly decreased in dimethoate treated animals compared to controls. The results indicate that due to the effect of dimethoate, the crosslinking and maturation of collagen are impaired.  相似文献   
78.
Chromosomal aberrations induced by cobaltous chloride in mice in vivo   总被引:1,自引:0,他引:1  
The effects of cobaltous chloride in inducing chromosomal aberrations were observed on laboratory bred mice in vivo after single oral administration of different fractions (1/10, 1/20, 1/40) of the lethal toxic dose of the salt. Bone marrow cells were flushed out and processed for chromosome studies following colchicine, hypotonic, giemsa, air drying procedure. The parameters screened were chromosomal aberrations, with and without gaps and break per cell. Slides were screened after the expiry of 6, 12, 18, and 24 h. Statistical analysis indicated the clastogenic effects of the salt. The degree of chromosome damage was directly related to the concentration, and also to the period after administration. The different stages of the cell cycle were affected.  相似文献   
79.
Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Out data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.Part of this work was carried out during a leave at the Laboratory of Chemical Evolution.  相似文献   
80.
Of 18 commercially used textile dyes, eight were degraded by the white rot fungus,Phanerochaete chrysosporium, by 40 to 73% based on decrease of colour. Both the lignin-degrading enzyme system ofP. chrysosporium and adsorption to its cell mass were involved in the degradation of the diazo dye, Reactofix Gold Yellow. Degradation was best achieved by adding the dye to the medium and then inoculating with pre-grown mycelium; inoculation with spores resulted mainly in dye adsorption.  相似文献   
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