Single implantation of microencapsulated islets into rats with streptozotocin-induced diabetes corrected the diabetic state for 2 to 3 weeks. The microencapsulated islets remained morphologically and functionally intact throughout long-term culture studies lasting over 15 weeks.

https://science.sciencemag.org/content/sci/210/4472/908.full.pdf

Microencapsulated islets as bioartificial endocrine pancreas

The diabetes syndromes produced by the two single gene mutations, obese (ob), and diabetes (db) are identical when both genes are expressed on the same inbred background, whereas on different backgrounds the syndrome changes from a severeobesity, moderate-diabetes to a severe life-shortening diabetes. The same initial sequence of events occurs in both conditions. Increased secretion of insulin and hyperphagia is followed by moderate hyperglycaemia with a further compensatory increase in insulin secretion followed by an expansion of the beta-cell mass. On the BL/6 inbred background, hypertrophy and hyperplasia of the beta cells continues until hyperglycaemia is controlled, whereas on the BL/Ks background, beta cell expansion fails and islet atrophy occurs causing insulinopenia, marked hyperglycaemia, and severe diabetes. The data presented here suggest that hyperphagia, hyperinsulinaemia, or both, early in development trigger the abnormal sequence of metabolic events leading to the obesity-diabetes state. These primary events interact with unknown genetic modifiers to produce either a juvenile or maturity-onset type of diabetes. An understanding of the mode of action of these background modifiers influencing the severity of diabetes in mice should lead to a better understanding of the ways in which unknown genetic and environmental factors contribute to human diabetes.

/pdf/obese-and-diabetes-two-mutant-genes-causing-diabetes-obesity-yqlwh6974s.pdf

Obese and diabetes: two mutant genes causing diabetes-obesity syndromes in mice.

Publisher Summary This chapter deals with the immunologically privileged sites. Genetically alien grafts of a wide variety of both normal and malignant tissues have repeatedly been transplanted to anatomically unnatural sites in the body—that is, transplanted heterotopically—for many different though frequently interrelated purposes. The chapter presents a critical account of the status of the known or suspected privileged sites in the body and evaluates their significance from both the immunologic and therapeutic viewpoints. The chapter focuses on following considerations of privileged sites: (1) privileged sites can be created artificially, (2) it is recognized that better understanding of the modus operandi of privileged sites may lead to improvement in the results obtainable with therapeutic allografts, and (3) naturally occurring privileged sites afford important “experiments of nature” pertinent to critical evaluation of the theory of immunologic surveillance against neoplastic disease. Finally, the chapter concludes by highlighting nude mice because their basic congenital athymic status renders them “immunologically privileged” hosts that sustain on an indefinite basis both allografts and xenografts from a wide spectrum of vertebrate donors.

Immunologically Privileged Sites

Technology of mammalian cell encapsulation.

Receptors for peptide hormones and neurotransmitters are integral components of the plasma membrane of cells which serve to couple the external milieu to the intracellular regulators of metabolism. These macromolecules are usually high molecular weight glycoproteins, and in many cases appear to have more than one subunit capable of binding the hormone. The interaction of the hormone or neurotransmitter with its receptor is rapid, reversible, and of high affinity and specificity. Many receptors exhibit cooperative properties in hormone binding or biological function. The concentration of receptors on the membrane is a function of continued synthesis and degradation, and may be altered by a variety of factors including the hormone itself. The fluid mosaic nature of the membrane may allow hormone receptors and effectors to exist in free floating states. Further investigations of the hormone-receptor interaction will no doubt yield new insights into both the mechanism of hormone action and membrane structure and function.

/pdf/membrane-receptors-for-hormones-and-neurotransmitters-1mqu6naxr2.pdf

Membrane receptors for hormones and neurotransmitters.

Crystal and solution structure studies on insulins of different sequences and of widely different receptor binding affinities are reported. Bovine insulin, studied as a control, has a circular dichroism spectrum which is dependent both on protein concentration and zinc concentration. The spectrum appears to be related to the level of association of the insulin molecules. This implies that when using circular dichroism to compare solution structures of insulin derivatives or species variants one must make the comparison at equivalent levels of association and not merely at the same concentration. Changes in circular dichroism are related to the known crystal structure of zinc insulin hexamers. The chinchilla insulin spectrum shows a reduced zinc dependence in low-salt conditions which correlates with the inability to form crystals in similar conditions. This is attributed to an amino acid substitution at position B4. Crystals are obtained in high-salt conditions and X-ray diffraction patterns show these to be isomorphous with bovine 4Zn insulin crystals. Guinea pig insulin failed to crystallise under conditions which are normally conducive to the formation of crystals of zinc insulin hexamers and the circular dichroism showed no zinc dependence. This is consistent with a monomeric structure. The significance of the association behaviour of chinchilla and guinea pig insulins may be in the storage of the hormone in vivo. Whereas the monomeric form of chinchilla insulin has a structure closely related to bovine insulin, the circular dichroism indicates a gross structural difference for guinea pig insulin. This may be similar to that in des-A21, des-B30-insulin, as both lack the Arg-B22--Asn-A21 carboxylate ion pair. The similarity of structure of chinchilla and bovine insulins is reflected in their receptor binding whereas the low receptor binding of guinea pig insulin probably results from the changes in its conformation rather than an alteration in residues of a receptor binding region.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1975.tb02190.x

The relation of conformation and association of insulin to receptor binding; x-ray and circular-dichroism studies on bovine and hystricomorph insulins.

Because islet-cell tumors of the pancreas produce proinsulin-like material in vitro, the plasma of 11 patients with functioning insulinomas was studied to determine the immunoreactive insulin proportion contributed by circulating proinsulin-like material. The plasma of nine patients with insulinomas showed on gel filtration an increased proinsulin-like material (28 to 89 per cent) as compared to subjects of normal weight, those who were obese, and those with functional hypoglycemia (less than 20 per cent). Polyacrylamide-gel electrophoresis of serum showed material compatible with proinsulin, insulin and an intermediate component. Considering the data so far reported, any patient with hypoglycemia who shows an elevated percentage of proinsulin-like material should be suspected of having an insulinoma. In one patient, surgical removal of an islet-cell adenoma resulted in a fall of serum proinsulin-like material from 65 to 0 per cent. Determination of plasma proinsulin-like material may provide dia...

https://www.nejm.org/doi/pdf/10.1056/NEJM197105062841803?listPDF=true

Circulating proinsulin-like material in patients with functioning insulinomas.

Isolated rat islets of Langerhans were incubated for 60, 120, and 180 min and the incorporation of leucine-3H into proinsulin and insulin moieties was followed. Synthesis and release of these hormones could be followed by separate extractions of islets and incubation media.

Release of newly synthesized proinsulin and insulin occurred under the following conditions: (a) incubation for greater than 60 min; (b) glucose concentrations above 5.3 mmoles/liter; (c) incubation with 5 mM dibutyryl cyclic AMP or theophylline in 5.3 mM glucose (potentiated by 16 mM glucose); and (d) incubation with 5 mM tolbutamide and 16 mM glucose.

Synthesis of proinsulin and insulin was enhanced by time of incubation, high glucose concentrations, by dibutyryl cyclic AMP or theophylline, and by tolbutamide only at 16 mM glucose. Synthesis was totally inhibited by tolbutamide at 5.3 mM glucose.

https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/106357/JCI70106357.pdf

Synthesis and release of proinsulin and insulin by isolated rat islets of Langerhans

Return to normal of blood-glucose, plasma-insulin, and weight gain in New Zealand obese mice after implantation of islets of Langerhans.

INSULIN receptors have been thought to have remained unaltered despite evolutionary changes in the hormone1. Because insulins from hystricomorph rodents are known to be highly substituted compared with other mammalian insulins, we decided to investigate the insulin receptor of some hystricomorphs to determine whether evolutionary change had occurred within the receptor itself. Here we present the first evidence that hystricomorph rodent insulin receptors have undergone evolutionary change.

Norman R. Lazarus

Papers

The relation of conformation and association of insulin to receptor binding; x-ray and circular-dichroism studies on bovine and hystricomorph insulins.

Circulating proinsulin-like material in patients with functioning insulinomas.

Synthesis and release of proinsulin and insulin by isolated rat islets of Langerhans

Return to normal of blood-glucose, plasma-insulin, and weight gain in New Zealand obese mice after implantation of islets of Langerhans.

Evolutionary change in the insulin receptors of hystricomorph rodents