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At least 1,081 records · Page 60Linked to original sources
PubMed1975

Glucose inhibiton of the permeation of chloromercuribenzene-p-sulphonic acid in the plasma membrane of pancreatic beta-cells.

The transport of chloromercuribenzene-p-sulphonic acid (CMBS) was studied in microdissected pancreatic islets of ob/ob mice incubated in Krebs-Ringer bicarbonate medium. Glucose inhibited the islet uptake of CMBS. The initial binding of CMBS to superficial thiol groups was inhibited to a lesser extent than was its further permeation into the interior of the plasma membrane. The non-metabolized glucose analogue 3-0-methyl glucose had no effect on the permeation of CMBS. Whereas mannoheptulose, epinephrine and diazoxide lacked any effect in themselves, they tended to counteract the glucose inhibition of CMBS permeation. The ability of glucose to inhibit CMBS permeation is related to its insulin-releasing action rather than to its membrane transport or further metabolism.

4-Chloromercuribenzenesulfonate↗
PubMedDate not supplied

[Adrenaline and cyclic AMP stimulation of ketopentose and sedoheptulose formation in rat liver homogenates].

Formation of sedoheptulose-7-phosphate and ketopentose phosphate was studied in vitro as affected by epinephrine and cAMP. No effect of epinephrine on the activity of transketolase was found with ribose-5-phosphate as a substrate of the nonoxidative reactions of the pentose phosphate ccyle. Epinephrine and cAMP enhance the formation of ketopentoses and sedoheptulose with glycogen as a main carbohydrate source, which is most pronounced in the experiments with cold preincubation. The phosphorylase system mediate influence of epinephrine and cAMP on the nonoxidative reactions products may be assumed.

Animals↗
PubMed1979

Comparative chemical, biological and clinical studies of 99mtc-glucoheptonate and 99mtc-dimercaptosuccinate as used in renal scintigraphy.

The renal radiopharmaceutical preparations 99mTc-DMS and 99mTc-GH were examined chemically, biologically and clinically. Both preparations are of high radiochemical purity. The biodistribution of both preparations was examined in experimental animals at different time intervals, from 15 min to 4 hr; the precentage of incorporation of 99mTc-DMS into kindeys is much higher (29.4% to 52.0%) than that of 99mTc-GH (12.80% to 22.20%). Both preparations accumulate to a greater extent in the renal cortex than in the medulla. The most suitable time for renal scintigraphy for 99mTc-DMS is 90--150 min while for 99mTc-GH it is 60--90 min. It is concluded that 99mTc-DMS is more suitable for static scintigrams on the scanner and 99mTc-GH for dynamic studies with the gamma camera.

Animals↗
PubMed1978

5-Dehydro-3-deoxy-D-arabino-heptulosonic acid 7-phosphate. An intermediate in the 3-dehydroquinate synthase reaction.

3-Dehydroquinate synthase was purified to homogeneity from Escherichia coli. It was found to be a single polypeptide chain of Mr = approximately 57,000. Reaction mixtures of pure enzyme and the substrate, 3-deoxy-D-arabino-heptulosonic acid 7-phosphate, were incubated for short times and treated with NaB3H4. The resulting 3-deoxyheptonic acid 7-phosphate was degraded with sodium periodate, and formic acid representing C-5 of the substrate was isolated. The presence of 3H in the formate corresponding to 15% of the enzyme was interpreted as indicating a 5-dehydro derivative of the substrate as an intermediate of the reaction. Quinic acid, resulting from reduction of 3-dehydroquinate with NaB3H4, was also isolated and degraded with periodate. The formate from C-4 of the quinate was unlabeled, indicating that 3,4-bisdehydroquinate is not an intermediate.

Borohydrides↗
PubMed1985

Interaction of lipid vesicles with an heptoseless strain of Escherichia coli.

The conditions for uptake of lipid vesicles by the deep rough mutant of Escherichia coli, strain D21F2, and the parent strain, K12 were studied. A variety of lipids including phosphatidylcholine, phosphatidylethanolamine, diglyceride, cholesterol and palmitic acid were taken up much more readily by the deep rough mutant than the K12 strain. The uptake of lipid in the mutant strain was enhanced by Ca2+ at an optimal concentration of 2 mM, by alkaline pH and by growth of the cells up to the late exponential phase. With K12 cells, cholesterol and phosphatidylethanolamine were taken up from equimolar mixtures at similar rates thus suggesting the involvement of a fusion process. With D21F2 cells, the endogenous lipids of which had been labelled by growth in [3H] acetate, the uptake of exogenous [32P] phosphatidylethanolamine and [32P] lysophosphatidylethanolamine was not accompanied by a loss of endogenous lipid to the incubation medium. This precluded the involvement of an exchange mechanism. The absorbed exogenous lipid and the endogenous lipids of D21F2 cells displayed the same susceptibility to hydrolysis by added phospholipase C. This indicated that the exogenous lipid is inserted into lipid core of the membrane rather than adsorbed at the cell surface.

Calcium↗
PubMed1985

Selective detection of 3-deoxymannooctulosonic acid in intact lipopolysaccharides by spin-echo 13C NMR.

The 3-deoxy-D-mannooctulosonic acid (KDO) region of lipopolysaccharides (LPS) from the heptoseless mutant Salmonella minnesota R595 and inner core and heptoseless mutants derived from Escherichia coli K12 was studied by 13C NMR spectroscopy. A spin-echo spectral editing technique was employed for the selective detection of the quaternary anomeric carbon of ketosidically linked KDO. Only two quaternary carbon resonances attributable to KDO were detected in the anomeric carbon spectral region of each LPS from heptoseless mutants E. coli D31m4 (99.7 and 100.8 ppm) and S. minnesota R595 (100.0 and 100.9 ppm). Integrated signal intensities from fully relaxed normal 13C spectra showed that equivalent molar quantities of KDO and glucosamine (i.e. 2 mol of each) were present in each of these samples. Similarly, only two KDO anomeric carbon resonances were detected in the LPS from the inner core mutants E. coli D21f1 (100.8 and 101.2 ppm) and E. coli D21e7 (100.8 and 101.2 ppm). These data confirm the presence of a KDO disaccharide structure rather than a trisaccharide as determined by others using thiobarbituric acid-based assays. The LPS of E. coli D21 (complete inner core oligosaccharide) exhibited four quaternary anomeric carbon resonances (99.4, 100.7, 101.8, and 102.7 ppm). The unequal intensities of these resonances, however, demonstrated that significant heterogeneity exists with respect to KDO substitution in this LPS. A third KDO moiety present in substoichiometric amounts could be consistent with this observation. However, this possibility could not be distinguished from other modes of substitutional heterogeneity involving only 2 KDO residues.

Escherichia coli↗