Islet of Langerhans

In terms of membrane area used and doUar value of the membrane produced, artificial kidneys are the single largest appHcation of membranes. Similar hoUow-fiber devices are being explored for other medical uses, including an artificial pancreas, in which islets of Langerhans supply insulin to diabetic patients, or an artificial Uver, in which adsorbent materials remove bUinibin and other toxins. 

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). 

The primary hormone responsible for conversion of glucose to glycogen is insulin (Figure 6.36). Insulin is secreted by special cells in the pancreas called the islets of Langerhans. Secretion of insulin is a response to increased glucose in the... 

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. 

Rat Charles Foster) 1 or 5 d Ix/d (G) Endocr 5 (degranuiation of beta-celis of islets of Langerhans) Barooah et al. 1980 Technical... 

In addition to the direct effects of hyperglycemia in enhancing the uptake of glucose into the liver, the hormone insulin plays a central role in regulating blood glucose. It is produced by the B cells of the islets of Langerhans in the pancreas in response to hyperglycemia. The B islet cells are freely permeable to glu-... 

Insulin and glucagon are produced in the pancreas by cells known as islets of Langerhans. P-Cells make up 70% to 90% of the islets and produce insulin, whereas P-cells produce glucagon. The main function of insulin is to decrease blood glucose levels, whereas glucagon, along with other counterregulatory... 

Insulin. Insulin is a peptide hormone produced by P-cells of the islets of Langerhans. It is an important anabolic hormone secreted at times when the concentration of nutrient molecules in the blood is high, such as periods following a meal. Its overall effects include allowing the body to use carbohydrates as an energy source and to store nutrient molecules. Specifically, insulin exerts its important actions on the following tissues ... 

Glucagon. Also a peptide hormone, glucagon is produced by a-cells of the islets of Langerhans. The overall effects of glucagon include ... 

Keywords Amphiphilic polymer Cell adhesion Chimeric protein Islet of Langerhans Self-assembled monolayer Stem cell... 

Cell transplantation has shown promise as a method for treating serious diseases. Various kinds of pluripotent stem cells have been developed or identified, including embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs). Moreover, the differentiation of stem cells to functional cells has been extensively studied. Previous studies have demonstrated that the transplantation of islet of Langerhans cells (islets) could successfully treat type 1 diabetes. Islets are insulin-secreting cells found in the pancreas. Over 200 patients... 

Teramura Y, Iwata H (2010) Bioartificial pancreas microencapsulation and conformal coating of islet of Langerhans. Adv Drug Deliv Rev 62 827-840... 

Bennet W, Sundberg B, Cg G et al (1999) Incompatibility between human blood and isolated islets of Langerhans a finding with implications for clinical intraportal islet transplantation Diabetes 48 1907-1914... 

Sorenson RL, Brelje TC and Roth C. 1994. Effect of tyrosine kinase inhibitors on islets of Langerhans evidence for tyrosine kinases in the regulation of insulin secretion. Endocrinology 134(4)4975—1978. 

Glucagon is a single-chain polypeptide of 29 amino acid residues and a molecular mass of 3500 Da. It is synthesized by the A-cells of the islets of Langerhans, and also by related cells found in the digestive tract. Like insulin, it is synthesized as a high molecular mass from which the mature hormone is releases by selective proteolysis. 

Pancreas A mixed exocrine and endocrine gland situated transversely across the posterior abdominal wall in the epigastric and hypochondriac regions. The endocrine portion is comprised of the Islets of Langerhans, while the exocrine portion is a compound acinar gland that secretes digestive enzymes. [NIH]... 

Insulin is produced in the pancreas by j8 cells in the region called the islets of Langerhans. It is a polypeptide hormone consisting of two chains an A chain... 

H. F. Chou, N. Berman, and E. Ipp, Oscillations of lactate released from islets of Langerhans Evidence for oscillatory glycolysis in P-cells. Am. J. Physiol. 262, E800-E805 (1992). 

Brelje, T. C., Scharp, D. W., and Sorenson, R. L. (1989) Three-dimensional imaging of intact islets of Langerhans with confocal microscopy. Diabetes 38,808-814. 

Figure 3.20 A plot of the percentage of maximal activity of glucokinase and hexokinase against the glucose concentration. Hexokinase is present in most if not all cells. Glucokinase is only present in hepatocytes and p-cells of the Islets of Langerhans in the pancreas (known as the endocrine pancreas). The enzyme is physiologically very important in both tissues e.g. a low activity in the p-cells can be a cause of one type of diabetes mellitus.

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