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Hydrolysis of p nitrophenyl phosphate was measured in a fraction enriched in plasma membranes from pancreatic islets of non inbred ob/ob mice. Hydrolysis was stimulated by K+ (10mM) in the pH range 5-10; a small peak of K+ induced activation was observed between pH 7.5 and 8. Both the K+ induced activation and the hydrolysis in the absence of K+ were Mg2+ dependent; maximum activation was obtained
Exposing micro-dissected pancreatic islets of non-inbred ob/ob mice to 2-5 mM-alloxan for 10 min decreased the ability of the islets to accumulate Rb+. Rb+ accumulation in pieces of exocrine pancreas was unaffected by alloxan. When islets were treated with alloxan in the presence of 2-20 mM-D-glucose, the Rb+-accumulating ability was protected in a dose-dependent manner. The protective action of D
Charge transfer (CT) at avoided crossings of excited ionized states of argon dimers is observed using a two-color pump-probe experiment at the free-electron laser in Hamburg (FLASH). The process is initiated by the absorption of three 27-eV-photons from the pump pulse, which leads to the population of Ar2+*-Ar states. Due to nonadiabatic coupling between these one-site doubly ionized states and tw
Suspensions of islet cells were prepared by shaking pancreatic islets from non inbred ob/ob mice in a Ca 2+ free buffer. The cells were incubated with or without 20 mM alloxan, and subsequently with Trypan Blue. The uptake of Trypan Blue by cell nuclei was analysed by microscope photometry and by counting the frequency of cells appearing stained on visual inspection. Cells classified as stained o
The effects of N iodoacetyl 2 amino 2 deoxy (D) glucose and various N bromoacetylglycosylamines on the release of insulin from microdissected pancreatic islets of non inbred ob/ob mice were studied. N Bromoacetyl β (D) glucosylamine (10 m(M)) initiated insulin release in the absence of (D) glucose and, at concentrations of 2.5-10 m(M), but not 20 m(M), potentiated insulin release in response to 10
Methods have been developed for the isolation on a semi-micro scale of a plasma membrane-enriched fraction from rat islets of Langerhans. An important feature of these experiments is the use of 125I-labeled wheat germ agglutinin as a specific probe for plasma membrane-containing fractions. The partly purified plasma membrane fraction had a density in sucrose of about 1.10 and was enriched in the a
The overall dynamics of glucose-induced insulin release was strikingly similar in dispersed cells and intact islets perifused in parallel. Both preparations exhibited a latency of 1-2 min, after which period there was a brisk rise of insulin release followed by a sustained second phase. During the second phase, insulin release from dispersed cells attained a stable plateau rate, whereas the releas
Pancreatic islets rich in beta-cells were isolated from non-inbred ob/ob-mice and used for studying various aspects of the function of the plasma membrane. A review is given of the authors' work along the following lines: the role of transmembrane transport or membrane binding in the recognition of insulin-releasing sugars, amino acids, sulfonylureas, and sulphydryl-blocking agents; the role of cy
The effects of thiol compounds on insulin release were studied in microdissected pancreatic islets of non-inbred ob/ob mice. In control experiments the reactivity of thiols against 6,6′-dithiodinicotinic acid and the degradation of mouse insulin were measured. At a concentration of 0.1 mM, 1-thio-D-glucose or reduced glutathione potentiated the insulin-releasing action of 10 mM D-glucose without a
Six previously pancreatectomized dogs were transplanted with ductligated, pancreatic allografts. Glucagon and insulin levels in the venous outflow from the graft and in the systemic circulation were determined during the first 60 minutes after transplantation. Two of the dogs were subjected to L-arginine stimulation 5 days after transplantation and the glucagon levels in the venous outflow from th
Suspensions of dispersed islet cells were prepared by shaking collagenaseisolated pancreatic islets of ob ob-mice in Ca2+-free buffer. The dispersed cells exhibited a glucose uptake with stereospecificity for the d isomer and concentrated Rb+ about 30-fold from a medium containing 70 μm RbCl. These results compare well with previous observations on unbroken islets and indicate that the dispersion
Insulin release and the content of cAMP were studied in microdissected pancreatic islets of non inbred ob/ob (obese) mice. In the absence of 3 isobutyl 1 methylxanthine, a phosphodiesterase inhibitor, 20 mM glucose had no effect on cAMP save a very small initial rise detectable by a freeze stop perifusion technique only. However, combined with this methylxanthine, 20 mM glucose produced significan
The effects of an electron dense thiol reagent, Hg phenylazo ferritin, on β cell ultrastructure was studied in cell suspensions from mouse pancreatic islets. This type of thiol reagent induced severe damage in the β cells. The ferritin particles were traced with the electron microscope and found to be bound to the plasma membrane as well as to various cytoplasmic structures. The β cell cytotoxic a
Mouse pancreatic islets microdissected free from, or surrounded by, exocrine cells were used to study the effects of secretin and choleeystokinm-pancreozymin on insulin release. Both secretin and cholecystokinin-pancreozymin potentiated glucose-stimulated insulin release regardless of whether exocrine cells were present. The results fail to support the idea that the presence of the exocrine parenc
Pancreatic islets, isolated from the pancreas of obese-hyperglycemic mice, were used to prepare free islet cells in suspension. Batches of 100 islets were disrupted by mechanical shaking for 10 sec in a Ca2+-free HEPES-buffered Krebs-Ring'er medium containing 1 mM EGTA. From 200-500 islets, about 2.2×106 cells could be obtained in suspension, corresponding to a yield of roughly 55% as calculated f
