islets of Langerhans

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islets of Langerhans:

see pancreaspancreas
, glandular organ that secretes digestive enzymes and hormones. In humans, the pancreas is a yellowish organ about 7 in. (17.8 cm) long and 1.5 in. (3.8 cm) wide. It lies beneath the stomach and is connected to the small intestine at the duodenum (see digestive system).
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Islets of Langerhans

 

the groups of cells in the pancreas of man and vertebrates (except cyclostomes) that form the endocrine part of the organ, secreting the hormones insulin and glucagon into the blood.

The islets of Langerhans are named for the German scientist P. Langerhans, who described them in 1869. In 1901, the Russian scientist L. V. Sobolev proved their endocrine function and established the occurrence of changes in the islets with diabetes mellitus. The dimensions of the islets of Langerhans are 50 to 500 microns, and there are between ten and 20 islets per mg of gland tissue. The islets do not communicate with the gland’s effluent ducts.

The islets of Langerhans develop from tubular processes of the anterior gut and, depending on the type of animal, consist of cells of several types. All animals have α cells and β cells. The granules of α cells are considered to be a form of glucagon deposit; the β cells, of insulin. C cells and D cells (the former have been found in the islets of Langerhans of guinea pigs; the latter, in man and dogs), which lack granules, are converted to α cells and β cells. In all, the tissue of the islets of Langerhans makes up 0.9 to 3.6 percent of the mass of the pancreas in children and 0.9 to 2.7 percent in adults.

V. M. SAMSONOVA

References in periodicals archive ?
The final goal remains development of strategies of islet cell transplantation without continuous antirejection treatment of recipients.
In this study, we showed that both total Akt and p-Akt were underexpressed in human insulinomas compared to the normal pancreas islet cells. In spite of this underexpression, the predominant form of Akt was p-Akt.
Samples were fixed in glutaraldehyde (3%), and the clusters of islet cells and PGA scaffold were observed under a scanning electron microscope (SEM, S-34000N; Hitachi Inc., Tokyo, Japan).
There is some evidence showing that pancreatic beta islet cell antibodies in children are predictive for determining progression to diabetes using proportional hazards analysis [34].
The two most common forms of DM are type 1 (T1DM) and type 2 (T2DM), with the former resulting from T-cell-mediated autoimmune destruction of b-cells of the pancreas, whereas the latter is characterised by insulin resistance with a non-autoimmune insulin secretory defect.1 Autoimmune DM is characterised by the presence of one or more islet-specific autoantibodies, including islet cell autoantibodies (ICA), insulin (IAA) and autoantibodies directed against the three major islet autoantigens - glutamic acid decarboxylase 65 (GADA), protein tyrosine phosphatase IA-2A and its isoform IA-2b/phogrin (IA-2bA).2,3
A large scale analysis of gene expression in individual islet cells of the pancreas suggests insulin-producing beta cells are not the only sub-class of cells important for glucose control and diabetes treatment as previously thought.
To address this hurdle, Klearchos Papas, professor in the Department of Surgery at the University of Arizona, Tucson, is studying the efficacy of islet cells from sources other than the human pancreas--including beta cells derived from human stem cells, and islet cells from pigs.
The pancreatic islet cells used in this study were generated from human stem cells using a technique recently developed by Douglas Melton, a professor at Harvard University who is an author of the Nature Medicine paper.
According to the company, AAT (Alpha-1 Antitrypsin) is used in reducing the risk of a non-organ transplant rejection, reducing the risk of developing graft versus host disease (GvHD) and for treating GvHD in patients who have received a cornea, bone marrow, stem cell or pancreatic islet cell transplant.
According to a Baylor University, Texas research team, a major problem in islet cell transplantation is the poor condition of islet cells attributed to hypoxia cell preservation and isolation.
For researchers and clinicians, Kulkarni (Joslin Diabetes Center, Harvard Medical School) brings together endocrinologists and diabetes specialists from the US and Israel for eight chapters on islet cell regeneration.
Islet cell tumors are rare pancreatic or peripancreatic tumors which constitute a broad spectrum of endocrine neoplasms.