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841.
Y Araki K Yoshioka Y Inoue Y Nakamura N Nakamura K Nakano T Yoshida M Kondo 《Endocrinologia japonica》1981,28(1):23-27
The minced pancreas of the neonatal rat was cultured for 35 days in a pancreatic chamber which was constructed of a plastic tube and an ultrafiltration membrane. Insulin and amylase secreted from this pancreatic chamber into the culture medium were measured. During the experiment, the concentration of glucose in the culture medium was changed between 5.5 and 16.5 mM at 2-3 day intervals in order to determine the insulin secretory response of the pancreatic tissue. Insulin secretion was markedly increased in response to 16.5 mM glucose. The ratio of insulin secretion to amylase secretion in the culture medium increased with the advance of culture days although secretions of both insulin and amylase decreased individually. On the 7th culture day, short term incubations were performed to test with various insulin secretagogues; obvious insulin release into the incubation medium was observed. These results show that the pancreatic chamber also in vitro secretes insulin rapidly and significantly in response to various stimuli; that by longer culture of a neonatal rat pancreas in this device, insulin secretory cells without exocrine tissue would be obtained without using digestive enzymes; that application of a pancreatic chamber for a pancreatic transplantation may be feasible. 相似文献
842.
Yoshio Honma Takashi Kasukabe Motoo Hozumi Yasuko Koshihara 《Journal of cellular physiology》1980,104(3):349-357
Mouse myeloid leukemia cells (Ml) were induced to differentiate into mature macrophages and granulocytes by various inducers. The differentiated Ml cells synthesized and released prostaglandins, whereas untreated Ml cells did not. When the cells were prelabelled with [14C]arachidonate, the major prostaglandins released into the culture media were found to be prostaglandin E2, D2, and F2α in an early stage of differentiation, but the mature cells produced predominantly prostaglandin E2. The synthesis and release of prostaglandins were completely inhibited by indomethacin. Dexamethasone, a potent inducer of differentiation of Ml cells, did not induce production of prostaglandins in resistant Ml cells that could not differentiate even with a high concentration of dexamethasone. These results suggest that production of prostaglandins in Ml cells is closely associated with differentiation of the cells. Homogenates of dexamethasone-treated Ml cells converted arachidonate to prostaglandins, but this conversion was scarcely observed with homogenates of untreated Ml cells. Dexamethasone and the other inducers stimulated the release of arachidonate from phospholipids. Therefore, induction of prostaglandin synthesis during differentiation of Ml cells may result from induction of prostaglandin synthesis activity and stimulation of the release of arachidonate from cellular lipids. Lysozyme activity, which is a typical biochemical marker of macrophages, was induced in Ml cells by prostaglandin E2 or D2 alone, as well as by inducers of differentiation of the cells, but it was not induced by arachidonate or prostaglandin F2α. These results suggest that prostaglandin synthesis is important in differentiation of myeloid leukemia cells. 相似文献
843.
Modifications of cell wall polysaccharides during auxin-induced growth in azuki bean epicotyl segments 总被引:2,自引:0,他引:2
Changes in sugar compositions and the distribution pattern ofthe molecular weight of cell wall polysaccharides during indole-3-aceticacid (IAA)-induced cell elongation were investigated. Differentialextraction of the cell wall and gel permeation chroma-tographyof wall polysaccharides indicated that galactans, polyuronides,xylans, glucans and cellulose were present in the azuki beanepicotyl cell wall. When segments were incubated in the absence of sucrose, IAAenhanced the degradation of galactans in both the pectin andhemicellulose fractions, whereas to some extent it enhancedthe polymerization of xylans and glucans in the hemicellulosefraction and an increase in the amounts of polyuronides in thepectin fraction and of -cellulose. In the presence of 50 mMsucrose, IAA caused large increases in the amounts of all thewall polysaccharides, and enhanced the polymerization of galactans,xylans and glucans in the hemicellulose fraction. These results and an important role of galactan turnover incell wall extension are discussed. (Received December 11, 1979; ) 相似文献
844.
Isao Karube Ikuo Satoh Yuichi Araki Shuichi Suzuki Hideaki Yamada 《Enzyme and microbial technology》1980,2(2):117-120
Monoamine oxidase (monoamine: oxygen oxidoreductase, EC 1.4.3.4 from Aspergillus niger and beef plasma) was immobilized in a collagen membrane. An enzyme electrode consisting of a monoamine oxidase - collagen membrane (10 units) and an oxygen electrode was prepared for the determination of monoamines. Monoamines were oxidized to aldehydes by the immobilized enzyme and oxygen consumption was monitored amperometrically by the oxygen electrode. The response time of the electrode was 4 min. The optimum conditions for the enzyme electrode were pH 7.4 and 30°C. A linear relationship was observed between the amine (tyramine) concentration in the range 50–200 μm and the difference in current. No decrease in the output current was observed over an observation period of one week. The difference in current was reproducible with an average relative error of 8%. Monoamines in meat extracts were determined by the enzyme electrode. 相似文献
845.
The mechanism by which malate synthesis from CO2 is increasedunder low concentrations of CO2 was investigated in C3 plants.A number of metabolites were administered to illuminated tomatoleaves, and their effects on the incorporation of 14CO2 intomalate were determined. Compared with water as a control, glycolate,glyoxylate, D,L-glycerate, glycine, phosphoglycolate and L-serineincreased malate synthesis by factors of 6.8, 3.8, 3.3, 2.5,2.3 and 2.2, respectively. The effect of exogenous glycolateon malate synthesis from CO2 was dependent on its concentrationup to 100 mu, but was independent of ambient CO2 concentration.The feeding of l-14C-glycolate in the light indicated that glycolatestimulated the carbon flow from CO2 to malate. The analysis of the products of 14CO2 fixation in illuminatedleaves supplied with glycolate showed increases in malate andsugar and decreases in serine and phosphate esters. However,this stimulated malate synthesis ceased when malonate was suppliedsimultaneously with glycolate. Treatment with glycolate didnot affect the dark 14CO2-fixation, but increased the 14C-malatesynthesis, with a corresponding decrease in 14C-aspartate and14C-glutamate. These results suggest that exogenous glycolateactivates malate dehydrogenase in leaves, and that the increasedglycolate formation at low CO2 concentrations is associatedwith the increased malate synthesis from CO2. (Received January 12, 1981; Accepted May 20, 1981) 相似文献
846.
The effect of the intraparticle diffusion resistance on the apparent stability of the immobilized enzyme suffering from the first-order deactivation has been studied quantitatively. A general expression for the relationship between the decreasing observed enzymatic reaction rate and the intrinsic enzyme deactivation rate has been introduced. The method to estimate the intrinsic deactivation rate constant also has been proposed. Using the invertases immobilized on a anion-exchange resin, the theory proposed in this work has been verified experimentally. 相似文献
847.
Biscyclo(Cys-Sar) [I] and biscyclo(Cys-Pro) [II] were prepared by the extension of amino acid moieties from cystine. Compound I equilibrates between two rotamers around the CSSC bond of the cystine residue in methanol, showing dual negative CD transitions (CS-SC) at 270 and 255 nm, and dual S-S vibrations at 507 and 539 cm?1 in Raman spectra. In contrast, a conformation of P-helix type is suggested in CH3CN, which shows a distinct negative CD at 270 nm and only one Raman band at 507 cm?1 for the S-S bond. Compound II rotates freely in dimethylsulfoxide (Me2SO) but takes a relatively stable conformer of P-helix type in methanol, chloroform/Me2SO (9:1), and chloroform/trifluoroacetic acid (9:1). The conformation in chloroform is retained even on addition of trifluoroacetic acid. A more complete conformation of compound II in water was determined from the negative CD of S-S transition and 1H-nmr spectra of the Cys-β-CH2 protons. 相似文献
848.
The structures of two capsular polysaccharides elaborated by Haemophilus influenzae type e, strains NCTC 8455 and 8472, respectively, have been investigated, methylation analysis and n.m.r. spectrometry being the principal methods used. It is concluded that the polysaccharides are composed of repeating-units having the following structure: In the polysaccharide from strain NCTC 8472, all of the repeating-units contain the β-dfructofuranosyl group. The polysaccharide from strain NCTC 8455, however, contains only traces of d-fructose, corresponding to approximately one group per 100 repeating-units. 相似文献
849.
850.