Islets of Langerhans
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Islets_of_Langerhans".

This photograph shows a mouse pancreatic islet, an often spherical group of hormone-producing cells. Insulin is labelled here in green, glucagon in red, and the nuclei in blue.

The diagram shows the structural differences between rat islets (top) and humans islets (bottom) as well as the ventral part (left) and the dorsal part (right) of the pancreas. Different cell types are colour coded. Rodent islets, unlike the human ones, show the characteristic insulin core.

A porcine islet of Langerhans. The left image is a brightfield image created using hematoxylin stain; nuclei are dark circles and the acinar pancreatic tissue is darker than the islet tissue. The right image is the same section stained by immunofluorescence against insulin, indicating beta cells.

Islets of Langerhans, hemalum-eosin stain.

Illustration of dog pancreas. 250x.

The endocrine (i.e., hormone-producing) cells of the pancreas are grouped in the islets of Langerhans. Discovered in 1869 by the famous German pathological anatomist Paul Langerhans, the islets of Langerhans constitute approximately 1 to 2% of the mass of the pancreas. There are about one million islets in a healthy adult human pancreas, which are distributed evenly throughout the organ; their combined weight is 1 to 1.5 grams.

Cell types

Hormones produced in the Islets of Langerhans are secreted directly into the blood flow by (at least) five different types of cells:^[1]

• Alpha cells producing glucagon (15-20% of total islet cells)
• Beta cells producing insulin and amylin (65-80%)
• Delta cells producing somatostatin (3-10%)
• PP cells producing pancreatic polypeptide (3-5%)
• Epsilon cells producing ghrelin. (<1%)

Islets can influence each other through paracrine and autocrine communication, and beta-cells are coupled electrically to beta cells (but not to other cell types).

Paracrine feedback

The paracrine feedback system of the islets of Langerhans has the following structure:^[2]

• Insulin: Activates beta cells and inhibits alpha cells.
• Glucagon: Activates alpha which activates beta cells and delta cells.
• Somatostatin: Inhibits alpha cells and beta cells

Electrical activity

Electrical activity of pancreatic islets has been studied using patch clamp techniques, and it has turned out that the behavior of cells in intact islets differs significantly from the behavior of dispersed cells^[3].

As a treatment for type I diabetes

Because the beta cells in the islets of Langerhans are destroyed in type I diabetes, clinicians and researchers are actively pursuing islet transplantation technology as a means of curing this disease^[4]. Rachel Harris, islet cell recipient, was transplanted at the Diabetes Research Institute in Miami, Florida. In June of 2004, Rachel became the world's longest surviving insulin-free diabetic according to the Miami Herald (published Feb. 13, 2004).^[5]

Islet transplantation currently requires potent immunosuppression to prevent host rejection of donor islets. An alternative source of beta cells, such an islets derived from adult stem cells or progenitor cells of a diabetic would eliminate the need for immuosuppressive therapy, and be safer for diabetics.^[6].

Transplantation

With the possibility of restoring beta cells, the Chicago Project headed at University of Illinois at Chicago Medical Center is investigating ways to regenerate beta cells in vivo. With that being said, beta cells experience apoptosis early and thus are destroyed within a normal-functioning pancreas. The source of this seems to come from the transfer of Pander, a gene that works by attaching to RNA^[7]. Pander, when active, causes the beta cells to be blocked at S phase, which induces apoptosis. This loss of beta cell mass eventually leads to a loss of most of the transplanted beta cells.

References in pop culture

• A Harlan Ellison short story titled "Adrift Just Off the Islets of Langerhans: Latitude 38° 54' N, Longitude 77° 00' 13" W" appears in his collection Deathbird Stories. (Those coordinates locate the intersection of H and 2nd N.E. in Washington, D.C., behind Union Station)
• American parodist "Weird Al" Yankovic released a song entitled Pancreas on his album Straight Outta Lynwood, which continually repeats the lyrics "Insulin, Glucagon, comin' from the Islets of Langerhans" during the final minute of the song.
• On their comedy album How Can You Be in Two Places at Once When You're Not Anywhere at All, The Firesign Theatre referred to immigrants who came "from little towns with strange names like Smegma, Spasmodic, Frog, and the far-flung Isles of Langerhans".
• In the Lord of the Rings parody book Bored of the Rings by the Harvard Lampoon, the map features two islands situated close to each other labled "The Isles of Langerhans".

External links

• MeSH A03.734.414
• Histology at OU 80_14 - "Pancreas"
• Diabetes Research Institute [1]
• Islet Cell Transplant Recipients [2]

Gallery

Hormones/Islet Architecture

Mouse islet immunostained for pancreatic polypeptide.

Mouse islet immunostained for insulin.

Mouse islet immunostained for glucagon.

References