Pancreatic islets

The absorption of sulfonylureas from the upper gastrointestinal tract is faidy rapid and complete. The agents are transported in the blood as protein-bound complexes. As they are released from protein-binding sites, the free (unbound) form becomes available for diffusion into tissues and to sites of action. Specific receptors are present on pancreatic islet P-ceU surfaces which bind sulfonylureas with high affinity. Binding of sulfonylureas to these receptors appears to be coupled to an ATP-sensitive channel to stimulate insulin secretion. These agents may also potentiate insulin-stimulated glucose transport in adipose tissue and skeletal muscle. 

Another biomedical appHcation of mictocapsules is the encapsulation of Hve mammalian ceUs for transplantation into humans. The purpose of encapsulation is to protect the transplanted ceUs or organisms from rejection by the host. The capsule sheU must prevent entrance of harmful agents into the capsule, aUow free transport of nutrients necessary for ceU functioning into the capsule, and aUow desirable ceUular products to freely escape from the capsule. This type of encapsulation has been carried out with a number of different types of Hve ceUs, but studies with encapsulated pancreatic islets or islets of Langerhans ate most common. The alginate—poly(L-lysine) encapsulation process originally developed in 1981 (54) catalyzed much of the ceU encapsulation work carried out since. A discussion of the obstacles to the appHcation of microencapsulation in islet transplantation reviewed much of the mote recent work done in this area (55). Animal ceU encapsulation has also been researched (56). 

Hepoxylins are metabolites of arachidonic acid which arise from 12-HPETE in tissues such as pancreatic islet cells (where they stimulate glucose-dependent insulin release) and brain (where they appear to have a neuromodulatory role). The structure of the hepoxylins was confirmed by synthesis which also has provided this scarce material for biological investigation. 

Type 2 diabetes is a heterogeneous and progressive endocrine disorder associated with insulin resistance (impaired insulin action) and defective function of the insulin-secreting (3-cells in the pancreatic islets of Langerhans. These endocrine disorders give rise to widespread metabolic disturbances epitomised by hyperglycaemia. The present classes of antidiabetic agents other than insulin act to either increase insulin secretion, improve insulin action, slow the rate of intestinal... 

The predominant cell type in the pancreatic islets of Langerhans. The main secretory product of the (3 -cell is the peptide hormone insulin which has vital actions for the control of nutrient homeostasis and cellular differentiation. 

OTRs are mainly expressed in myoepithelial cells of the galactiferus channels and the myometrium. The OTRs in vascular endothelial cells, renal epithelial cells (macula densa, proximal tubule) and cardiomyocytes induce the production of NO (vasodilation), natriuresis and release of ANP, respectively. The endometrium, ovary, amnion, testis, epididymis, prostate and thymus also express the OTR supporting a paracrine role of this peptide. Osteoblasts, osteoclasts, pancreatic islets cells, adipocytes, and several types of cancer cells also express OTRs. More over, expression of the OTR... 

Pancreatic islets of Langer- Cell replacement for diabetes, Parkinson s disease. 

Margulis, B.A., Sandler, S., Eizirik, D.L., Welsh, N., Welsh, M. (1991). Liposomal delivery of purified heat shock protein hsp70 in rat pancreatic islets as protection against interleukin I beta-induced impaired beta cell function. Diabetes 40, 1418-1422. 

Another condition involving ceruloplasmin is aceru-loplasminemia. in this genetic disorder, levels of ceruloplasmin are very low and consequently its ferroxidase activity is markedly deficient. This leads to failure of release of iron from cells, and iron accumulates in certain brain cells, hepatocytes, and pancreatic islet cells. Affected individuals show severe neurologic signs and have diabetes mellitus. Use of a chelating agent or administration of plasma or ceruloplasmin concentrate may be beneficial. 

CF-related diabetes shares characteristics of both type 1 and type 2 diabetes mellitus but is categorized separately. The primary cause of CFRD is insulin deficiency resulting from both reduced functional pancreatic islet cells and increased islet amyloid deposition. Insulin secretion is delayed in response to glucose challenge, and absolute insulin secretion over time is reduced. Some insulin resistance may also be present in CFRD however, sensitivity may be increased in CF patients without diabetes.8... 

E3. Eto, K., Sakura, H., Yasuda, K., Hayakawa, T Kawasaki, E Moriuchi, R., Nakataki, S., Yaza-ki, Y., and Kadowaki, T Cloning of a complete protein-coding sequence of human platelet-type phosphofructokinase isozyme from pancreatic islet. Biochem. Biophys. Res. Commun. 198, 990-998 (1994). 

Petrik J, Pell JM, Arany E et al 1999 Overexpression of insulin-like growth factor-II in transgenic mice is associated with pancreatic islet cell hyperplasia. Endocrinology 140 2353-2363... 

Resting cells do not express iNOS but the capacity to express this enzyme after specific stimuli is present in several tissues. Cells such as macrophages, endothelial cells, kidney cells, chondrocytes, cardiac myocytes, pancreatic islets and fibroblasts... 

Boninsegna, S., Bosetti, P., Carturan, G., Dellagiacoma, G., Dal Monte, R. and Rossi, M. (2003) Encapsulation of individual pancreatic islets by sol-gel Si02 A novel procedure for perspective cellular grafts. Journal of Biotechnology, 100, 277-286. 

Krol S, Del Guerra S, Gmpillo M et al (2006) Multilayer nanoencapsulation. New approach for immune protection of human pancreatic islets. Nano Lett 6 1933-1939... 

Moberg L, Johansson H, Lukinius A et al (2002) Production of tissue factor by pancreatic islet cells as a trigger of detrimental thrombotic reactions in clinical islet transplantation. Lancet 360 2039-2045... 

Altman JJ, Legrelle M, Penformis A, Mallegol S, Fakir M, Chapa O, Capron F (1992) In Ricordi C (ed) Pancreatic islet cell transplantation. RG Landes, Austin, TX, p 215... 

Goosen MFA (1994) In Lanza RP, Chick WM (eds) Pancreatic islet transplantation, vol III immunoisolation of pancreatic islets. RG Landes, Austin, TX... 

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