| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Wroblewski, R, et al.
(author)
-
X-ray microanalysis of in situ and isolated pancreatic islets
- 1998
-
In: Pancreas. - 0885-3177 .- 1536-4828. ; 16:2, s. 134-140
-
Journal article (peer-reviewed)abstract
- The effect of stimulation of insulin secretion in pancreatic beta cells on the elemental composition ofthese cells was investigated by x-ray microanalysis. In vitro experiments on isolated islets ofLangerhans from ob/ob mice were compared to in situ experiments. The only significant difference inthe elemental composition of beta cells from ob/ob mice versus their lean counterparts is a lower Ca concentration in the ob/ob animals. The nucleus of the beta cells has a higher concentration of P, K, and Na than the cytoplasm, which has a higher concentration of S and Cl. No polarized ion distributionin the cytoplasm of the beta cells was observed. Isolated beta cells show a higher concentration of Na and Cl and a lower concentration of K than their in situ counterparts. Stimulation of insulin secretion with glucose both in situ and in vitro showed only very small effects on the elemental composition of the beta cells: a tendency to a decreased P content was noted. In vitro experiments using stimulation with high extracellular K+ showed, in addition, a small increase in the intracellular K concentration. Inconclusion, while the elemental content of beta cells in vitro differs from that in situ, the response to glucose stimulation appears to be similar in both systems.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Barg, Sebastian, et al.
(author)
-
The stimulatory action of tolbutamide on Ca2+-dependent exocytosis in pancreatic beta cells is mediated by a 65-kDa mdr-like P-glycoprotein
- 1999
-
In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 96:10, s. 5539-5544
-
Journal article (peer-reviewed)abstract
- Intracellular application of the sulfonylurea tolbutamide during whole-cell patch-clamp recordings stimulated exocytosis >5-fold when applied at a cytoplasmic Ca2+ concentration of 0.17 microM. This effect was not detectable in the complete absence of cytoplasmic Ca2+ and when exocytosis was elicited by guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). The stimulatory action could be antagonized by the sulfonamide diazoxide, by the Cl--channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), by intracellular application of the antibody JSB1 [originally raised against a 170-kDa multidrug resistance (mdr) protein], and by tamoxifen (an inhibitor of the mdr- and volume-regulated Cl- channels). Immunocytochemistry and Western blot analyses revealed that JSB1 recognizes a 65-kDa protein in the secretory granules. This protein exhibited no detectable binding of sulfonylureas and is distinct from the 140-kDa sulfonylurea high-affinity sulfonylurea receptors also present in the granules. We conclude that (i) tolbutamide stimulates Ca2+-dependent exocytosis secondary to its binding to a 140-kDa high-affinity sulfonylurea receptor in the secretory granules; and (ii) a granular 65-kDa mdr-like protein mediates the action. The processes thus initiated culminate in the activation of a granular Cl- conductance. We speculate that the activation of granular Cl- fluxes promotes exocytosis (possibly by providing the energy required for membrane fusion) by inducing water uptake and an increased intragranular hydrostatic pressure.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Dodabalapur, A, et al.
(author)
-
Resonators and materials for organic lasers based on energy transfer
- 1998
-
In: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 4:1, s. 67-74
-
Journal article (peer-reviewed)abstract
- Optically pumped lasers have been fabricated with organic/polymeric materials capable of charge transport. The active materials employed are doped films with small molecule hosts and dye, oligomer, and conjugated polymer emitters, In these materials, the excited states created in the host are transferred nonradiatively to the guest molecules which are the emitters, This energy transfer results in very low absorption losses at the emission wavelength and relatively low-threshold powers for the onset of stimulated emission. Such gain media have been successfully included in many types of resonators including whispering-gallery mode, photonic bandgap, and distributed Bragg reflector (DBR) based resonators. A number of novel patterning and fabrication procedures have been developed for organic-based lasers.
|
|
