Streptozotocin-induced diabetes in the spontaneously hypertensive rat

Spontaneously hypertensive rats (SHR) were more sensitive to the diabetogenic effects of streptozotocin than normotensive Wistar-Kyoto (WKY) rats. Thus, 10 days after intravenous administration of 25 mg/kg streptozotocin in SHR, mean pancreatic insulin content was decreased by 42% (p less than 0.05), and mean plasma glucose concentration was increased from 85 to 215 mg/dl (p less than 0.001), whereas between 37.5 and 50 mg/kg of streptozotocin was required to produce similar effects in normotensive WKY rats. Also, there was a progressive decrease in blood pressure in SHR injected with 25, 35.7, or 50 mg/kg of streptozotocin, whereas blood pressure was progressively increased after streptozotocin in normotensive WKY rats. The opposite effects of streptozotocin-induced diabetes on blood pressure in SHR and WKY rats could be observed at similar degrees of hyperglycemia and are presently unexplained.

Enzyme immunoassay of pancreatic glucagon at the picogram level using beta-D-galactosidase as a label

An enzyme immunoassay of pancreatic glucagon was established by using E. coli beta-D-galactosidease [EC 3.2.1.23] as a marker. In order to increase the sensitivity of the immunoassay, different peptides obtained from glucagon fragments were used to produce the enzyme conjugate and the immunogen. Antiserum N6E raised against C-terminal fragment peptide (15-29) could be diluted to more than 1 : 100,000 in the assay and was highly specific for pancreatic glucagon. The antiserum reacted well with the C-terminal fragment peptide (21-29) as well as another fragment peptide (15-29) and pancreatic glucagon. The enzyme immunoassay using antiserum N6E and fragment peptide (21-29)-enzyme conjugate could detect as little as 1 to 2 pg of glucagon. The mean recovery of glucagon added to serum specimens was 104% and the coefficients of variation were 3.7-14.5% (within assay) and 9.0-18.5% (between assay).

Somatostatin in the pancreas and hypothalamus of obese mice

The pancreatic content of somatostatin, insulin, and glucagon and the hypothalamic content of somatostatin were examined in ob/ob mice at various ages and in goldthioglucose-obese mice. The total pancreatic content of somatostatin was increased in ob/ob mice compared to controls: 92 ng vs 75 ng (a 22% increase) at 2 months of age; 208 ng vs 131 ng (a 60% increase) at 6 months of age; and 184 ng vs 118 ng (a 60% increase) at 8 months of age. The total pancreatic content of glucagon in ob/ob mice was already enhanced by 70% over controls at 2 months of age (301 ng vs 173 ng) and did not increase further at later stages, whereas that of insulin progressively rose with age. In goldthioglucose-obese mice the pancreatic content of insulin was also increased but to a lesser extent than in ob/ob mice; the pancreatic levels of somatostatin and glucagon were unaltered. In both ob/ob mice (regardless of age) and goldthioglucose-obese mice, there was no significant change in the hypothalamic content of somatostatin compared with that of lean controls.

beta-Endorphin in the human pancreas

Using a specific antiserum, beta-endorphin was quantitated in 8 human pancreas obtained at autopsy by radioimmunoassay and localized by immunocytochemistry. The mean (+/- SE) concentration of beta-endorphin in pancreatic extracts of 5 non-diabetic adults was 13.5 +/- 9.8 ng/gm with a range of 2.1 to 52.8 ng/gm of tissue. Pancreatic beta-endorphin concentration in two premature infants were within the range found in adults. In one diabetic pancreas, there was no measurable beta-endorphin. Specific beta-endorphin immunofluorescence is localized within the pancreatic islets. This finding suggests that beta-endorphin may participate in intraislet regulation of pancreatic hormone secretion.

Does somatostatin in each organ act specifically on that particular organ?

Rats with hypercalcemia induced by injection of vitamin D2 had a decreased thyroid somatostatin content, whereas the somatostatin content in their pancreas was almost within the normal range. This suggests that somatostatin in different organs acts specifically on each particular organ as a local hormone or hormone-like substance.

Localization of pancreatic polypeptide cells in a limited lobe of the human neonate pancreas: remnant of the ventral primordium?

The localization of pancreatic polypeptide (PP) cells was studied in the pancreas of four human neonates by specific immunocytochemical techniques. PP cells were detected in all parts of the pancreas. However, examination at low magnification showed that they were considerably more numerous in a small lobe, located at the posterior-inferior part of the head region. It is suggested that this lobe corresponds to the part of the pancreas that is derived from the ventral primordium. Both in the lobe rich in PP cells and in the remainder of the pancreas, approximately 75% of PP cells were present in the islets and 25% distributed among acini and ducts.

Localization of an endogenous lectin in chicken liver, intestine, and pancreas

Extracts of adult chicken liver, pancreas, and intestine contain high levels of a lectin which appears to be identical to one previously purified from embryonic chick muscle. This lectin is virtually absent from adult muscle, but is highly concentrated in cells lining liver sinusoids, intestinal goblet cells, and the extracellular spaces surrounding pancreatic acini. These findings suggest that the lectin may play different roles in different tissues and at different times in the life of a chicken.

Glicentin immunoreactive cells: their relationship to glucagon-producing cells

The cellular and subcellular localization of one of the gut glucagon-like immunoreactants (GLI-1 or glicentin) and the relative distribution of glicentin- and glucagon-containing cells were investigated by immunocytochemistry. By immunofluorescence, the antiglicentin serum, which does not react with glucagon, revealed positive cells in the islets of Langerhans and in the gut mucosa, particularly in the terminal ileum and colon. In the intestinal mucosa, it was proven ultrastructurally that the glicentin immunoreactive cells correspond to the L cell and that the secretory granules represent the storage compartment of the immunoreactive material. In pancreatic islets, consecutive semithin sections treated with antiglicentin and specific antiglucagon sera showed that the same A cell population reacted with both sera, while immunoperoxidase staining on thin sections revealed that the immunoreactive material was confined to the secretory granules. The same results were obtained on dog oxyntic mucosa, where the glicentin- and glucagon-containing cells were identified as the gastric A cell. The immunocytochemical demonstration of a common glicentin-like material in the A and L cells together with the known presence of a common immunoreactant in glicentin and glucagon strongly support the idea that the A and L cells are ontogenetically related and synthesize their secretory product via a glicentin-like precursor which, by specific cleavage, could yield glucagon and gut glucagon-like immunoreactants.

[Zinc in the tissues: age dependence and local findings in cachexia, live cirrhosis and long-term intensive care]

Zinc concentrations in autopsy material of human heart muscle, skeletal muscle, iliac crest, pancreas and liver were analyzed by atomic absorption spectrophotometry. Age dependent differences of zinc concentrations are seen in the liver. High values shows liver of premature infants, a minimum is measured in childhood which is followed by an increase in adult and senile patients. The other organs show no significant changes. Different diseases like diabetes or liver cirrhosis do not influence the zinc concentration in skeletal muscles and iliac crest. Long-term intensive care patients show a marked decrease in zinc concentration of the heart muscle. In the cirrhotic liver the zinc pool is depleted. In diabetes mellitus zinc concentration of the whole pancreas is normal, in cachexia it is critically decreased.

Proton N.M.R. study of the conformational dynamics of porcine pancreatic colipase. Titration of aromatic residues

The low-field portion of the 360 MHz proton N.M.R. spectrum of native porcine pancreatic colipase has been studied as a function of pH over the pH range 2-12. Resonances associated with the 26 protons of the aromatic rings of the two histidines, two phenylalanines and three tyrosines have been identified and tentatively assigned to specific residues. Titrations of pH yielded apparent pKa's of 7.9, 6.9, 10.4, 10.3 and 11.3 for His I (His 30), His II (His 86), Tyr I (Tyr 56 or 57), Tyr II (Tyr 56 or 57) and Tyr III (Tyr 53) respectively (tentative assignments). The high pKa value of His 30 is attributed to the vicinity of Asp 31. The mobility of the aromatic ring of Tyr 53 is hindered and an upper bound of 500 s-1 on the rate of rotation can be estimated. The aromatic rings of the 2 other tyrosine residues and of the 2 phenylalanine residues can rotate freely on the N.M.R. time scale. The study of perturbations in titration profiles and chemical shift values reveals a specific interaction of His 86 with Tyr I and, to a lesser extent, Tyr II. The existence of this interaction indicates that the protein folding brings in close spatial vicinity two distant regions of the covalent structure to form a "hydrophobic-aromatic" site which might be involved in the binding of bile salt micelles to pancreatic colipase.

[Characterization of histones and chromatin of the hepatopancreas in Palaemon serratus (Crustacea Natantia)]

The chromatin of shrimp hepatopancreas has been extracted from isolated nuclei and characterized. Nuclei were prepared in the presence of Cu++ and phenyl methyl sulfonyl fluoride in order to inhibit the nuclease and protease activities throughout the different purification steps. The purified nuclei are heterogenous in size and show a density of 1,367 g/ml determined on saccharose - glucose gradients. After washing in 0,14 M NaCl and then in 10(-2) M Tris-HCL, pH = 7,6, the nuclei were disrupted in water. The solubilized chromatin was precipitated in 0,15 M.NaCl. This chromatin is characterized by a high level of RNA (RNA/DNA = 0,38) and of non histone proteins (NHP/DNA = 0,6). The denaturation curve showed only one Tm at 69 degrees in 2.10(-4) M.EDTA. When the chromatin was extracted in the presence of staphylococcal nuclease, the Tm reached 80 degrees C. The kinetics of the digestion by the staphylococcal nuclease have been studied and show that 10 per cent of hydrolysis occurs within the first minute. The repeat length of DNA as determined with the polymers of higher order is 189 +/- 5 base pairs. The existence of nucleosomes was confirmed by electron microscopy. The superstructure of chromatin was not completely destroyed after solubilisation with a Potter. The histones were studied by gel electrophoresis after differential staining. The most important feature consists in the presence of two H1, two H2A and two H4. The acetylation levels of the histones were followed after injection of 14C-acetate in vivo. The subfraction H1, 0 was acetylated. Only one H3 was present and the two H2A fractions showed the same level of acetylation. H2B migrated faster than the H2A fractions like in Echinoderms. The two H4 fractions corresponded to two differently acetylated forms. Shrimp hepatopancreas histones were fractionated by molecular sieving on Biogel P 100 and characterized according to their electrophoretic properties as well as their amino-acid content. The amino-acid compositions of the different histone fractions were nearer to Echinoderm and Sipunculid histones, than Calf thymus homologue histones. All the fractions show a weaker basicity. The H3 fraction was the only one showing a lesser variability when compared to Calf thymus H3. The non histone proteins were extracted in 10(-2) M Tris-HCL, pH = 8 and 0.1 per cent SDS. A series of 50 proteins was detected. 80 per cent of the total amount of protein was localized in a molecular weight range comprised between 40 000 and 80 000 daltons. These proteins were compared to the histones and total proteins of sonicated chromatin solubilized by SDS in order to detect proteasic effects.

Isolation and characterization of somatostatin from pigeon pancreas

Most of the somatostatin-like activity from pigeon pancreas was found to correspond to small species with an apparent molecular weight of 1500--2500. This species was isolated under conditions minimizing intermolecular interactions and protease activities. The isolated product was characterized by two somatostatin radioimmunoassays, a bioassay, endgroup determination, and amino acid analysis. The structure of the isolated compound was determined to be H-Ala-Gly-cyclo-(Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys)-OH. Additionally, small amounts of des-Ala1-somatostatin, a possible degradation product of pancreatic somatostatin, and a large somatostatin-like species with an apparent molecular weight of 11,000--12,500 were detected. It is concluded that the main somatostatin-like polypeptide isolated from pigeon pancreas is identical to the mammalian hypothalamic tetradecapeptide somatostatin.

High molecular weight substances with insulin immunoreactivity

Substances which react with anti-insulin antibodies, but have a higher molecular weight than insulin are described. They have been studied by various authors in pancreatic adenomas, pancreas extracts, serum and cell-free systems. Proinsulin was the first of these products to be discovered, followed by its precursor, pre-proinsulin, and subsequently by a whole series of substances of ill-defined composition and more or less similar properties, grouped under the heading of "high molecular weight immunoreactive insulin" (HWIRI).

C-peptide, insulin and proinsulinlike components in diabetic and nondiabetic human pancreas

The contents of insulin and C-peptide extractable with acid alcohol from the tail of the pancreas and insulinoma were investigated, using gel filtration in seven nondiabetics including two patients with insulinoma and eight diabetics. The gel filtration patterns of both C-peptide and insulin in pancreatic extract were fairly stable even after the pancreas had been left for 14 hrs in the room temperature. In nondiabetics except cases of insulinoma the content of insulin in pancreas ranged from 1.42 to 4.56 U per gram and that of C-peptide from 8.76 to 25.63 microgram per gram wet pancreas. The proportion of proinsulinlike components (PLC) ranged from 0.01 to 2.04% of insulin plus PLC. In diabetics insulin content was low and ranged from 0 to 1.68 U per gram and that of C-peptide from 0 to 14.48 microgram per gram wet pancreas. In insulinoma, both insulin and C-peptide increased and PLC occupied 5.48 and 5.96%, respectively.

On the immunocytochemical localization of the vasoactive intestinal polypeptide

The distribution of vasoactive intestinal polypeptide (VIP) immunoreactive nerves and endocrine cells in the gastrointestinal tract and pancreas of a number of mammalian and submammalian species has been examined in order to throw light on the exact localization of this peptide. Seven out of 8 VIP antisera demonstrated numerous nerve fibers in the gut, whereas one antiserum (TR2) revealed only scattered, few nerve fibers. The distribution of endocrine cells demonstrated by the different VIP antisera varied considerably. Thus, some antisera demonstrated only endocrine cells in the feline antrum, others only colonic endocrine cells and still others only endocrine cells of the upper gut and pancreas. The variability in staining pattern of endocrine cells as well as recent radioimmunological data makes it opportune to suggest that true VIP is a neuronal peptide and that endocrine cells store peptides resembling, but not being identical with, VIP (VIPoids).

Immunohistochemical characterization of monolayer cell cultures of embryonic chicken pancreas and measurement of somatostatin release

Monolayer cell cultures of embryonic chicken pancreas contain functionally active insulin, glucagon and somatostatin-containing cells as evidenced by immunohistochemical and radioimmunoassay techniques. Hormone release is in relation to the number of each cell type present and responds to known specific secretory stimuli. The relatively high numbers of D-cells and amounts of immunoreactive somatostatin released by this preparation makes this system a suitable model for studies of somatostatin function and secretion.