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961.
A cholinergic proteolipid fraction (i.e. a hydrophobic lipoprotein) was separated from the of the cow, using affinity chromatography with the lipophilic gel Sephadex LH-20 and p-phenyltrimethylamonium as the active group. High affinity binding studies showed that only the specific fraction, desorbed after an acetylcholine (or acid) pulse, and corresponding to 0,72% of the proteolipids, is the one that binds the cholinergic ligands. The binding of (3H)atropine and (14C)d-tubocurarine demonstrated that there are 814 picomoles/g fresh tissue of muscarinic sites and only 76 picomoles/g of nicotinic sites. The specific radioactivity for (3H)atropine is 10,000 nmoles/g protein, suggesting a high degree of purification of the specific cholinergic proteolipid. 相似文献
962.
963.
1. The isolation of the mitochondrial ATPase F1 and its beta-subunit from commercial baker's yeast (Saccharomyces cerevisiae) is described. 2. The molecular weight determined by ultracentrifugation is 340000 +/- 30000. Gel chromatography indicates a molecular weight of 300000 +/- 20000. 3. Fluorimetric titration of the isolated enzyme with aurovertin reveals two binding sites per molecule. The isolated beta-subunit binds aurovertin in a 1 : 1 stoicheiometry. It is concluded that the ATPase molecule contains two aurovertin-binding beta-subunits. 4. The stabilizing agent methanol influences both the measured Kd and the concentration of binding sites for aurovertin. These results fit a model in which both F1 and aurovertin are distributed between aqueous and methanol phases. 5. The effect of methanol on the ATPase activity can be described in terms of the model proposed by Recktenwald and Hess (Recktenwald, D. and Hess, B. (1977) FEBS Lett. 76, 25-28). It is proposed that methanol enhances the affinity of the regulatory site for ATP, but at higher concentrations prevents the interaction between the regulatory and catalytic sites. 6. Since HSO(-3), a typical effector of the assumed regulatory site of F1, has no effect on the binding of aurovertin, it is concluded that the binding site of aurovertin is not correlated with the regulatory site. 7. The inhibition of ATPase activity by aurovertin is slowly (t 1/2 = 70 s) induced during turnover conditions. 8. From the effect of methanol on the inhibition of ATPase activity by aurovertin it is concluded that under turnover conditions the conformation is such that the aurovertin-binding sites have a 6-fold higher affinity for methanol than under resting conditions. 相似文献
964.
965.
P Carde C Chastang E Goncalves N Mathieu-Tubiana E Vuillemin V Delwail O Corbion A Vekhoff F Isnard J M Ferrero 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1992,315(13):545-550
Seraspenide, a synthetic tetrapeptide, inhibits cell cycle entry of normal hematopoietic stem cells. In mice it protects hemopoiesis against the damage caused by cytarabine, cyclophosphamide and carboplatin. Seraspenide has been given to 53 cancer patients undergoing monochemotherapy with cytarabine and ifosfamide in a double-blind cross-over randomized study. A significant protection of peripheral blood cells has been observed. Seraspenide has been devoided of toxicity. 相似文献
966.
Chloroflexus aurantiacus can be induced to shift from respiratory to photosynthetic energy production by introducing light and/or lowering the oxygen concentration of a culture. After induction, cells synthesize bacteriochlorophyll and proteins for the formation of a functional photosynthetic apparatus. Bacteriochlorophyll is detectable within 2 h after induction. Chlorosome polypeptides are detected after 8–12 h. Two proteins, Mr 60,000 and Mr 47,000, are present in both induced and noninduced cells and react specifically with antibodies against chlorosome polypeptides. Immunological data suggest that these proteins (Mr 60,000 and 47,000) are polyproteins which are transcribed and translated in the dark. When cells are exposed to light or low oxygen tension these proteins are processed into functional polypeptides required in the assembly of the chlorosome. The reaction center polypeptide (Mr 26,000) appears to be part of a separate genetic control system.Dedicated to Prof. G. Drews on occasion of his 60th birthday 相似文献
967.
968.
969.
970.
James E. Boggan Julian T. Hoff Edwin B. Boldrey William M. Wara 《The Western journal of medicine》1980,133(2):108-114
Thirty cases of intraspinal neoplasms occurring during the first two decades of life are reviewed. Histologic examination showed 13 of these to be astrocytomas, 6 neuroblastomas, 5 sarcomas, 3 ependymomas, 2 neurofibromas and 1 a schwannoma. Orthopedic deformities developed or worsened in 60 percent of patients surviving longer than a year after diagnosis. In five patients some form of endocrine deficiency developed after irradiation. For treatment of radiosensitive extradural malignant lesions, biopsy followed by irradiation is advocated. 相似文献