The absorption by human volunteers of glutamic acid from monosodium glutamate and from a partial enzymic hydrolysate of casein

Peripheral plasma concentrations of glutamic and aspartic acids and alanine were measured after ingestion of monosodium glutamate or a pancreatic hydrolysate of casein by human volunteers. The doses of each material were such that they contained similar amounts of glutamic acid. Plasma glutamic acid concentrations rose promptly after the monosodium glutamate but mean peak concentrations were well below those likely to cause neurological damage. Plasma aspartic acid concentrations also rose after the monosodium glutamate but the behaviour of plasma alanine concentrations suggested that intestinal transamination of glutamic acid was insufficient to cause an appreciable rise in alanine concentration in the peripheral plasma. Significant increments in plasma glutamic acid concentrations did not occur after the pancreatic hydrolysate of casein and it is probable that competition for absorptive mechanisms by other amino acids, both free and peptide-bound, causes absorption of glutamic acid to be slower from mixtures of peptides and amino acids than from monosodium glutamate itself.

The histochemistry of thiols and disulphides. III. Staining patterns in rat tissues

With the aid of new staining methods, thiol groups produced by the reduction of disulphide bonds were positively distinguished from pre-existing groups in paraffin sections of several organs of the rat. Good preservation of structures in which the natural thiol-disulphide balance had been maintained was sought by fixing the tissues in neutral formalin containing an organomercurial. After dissociation of the resulting mercaptide bonds that protected the native thiols, these were shown in one colour and then disulphide sites in another within the same sections. Intracellular granules and extracellular membranes rich in disulphides thereby stood out in red against the predominantly blue labelling of the cellular ground plasm. Intimate mixtures of the two forms in some places and the presumed transformation of thiols to disulphides in others, notably the keratinizing epithelium of the tongue, were readily seen. Supplemented by separate visualization of thiols and disulphides along with suitable controls for specificity of staining, the results obtained diverged in some major respects from those of previous investigations.

Gastrointestinal somatostatin: extraction and radioimmunoassay in different species

A radioimmunoassay capable of detecting 300 fg somatostatin has been developed and levels of the polypeptide in gastrointestinal tissues from man, dog, and rat have been measured. Rapid freezing of collected samples and careful control of extraction is necessary. Concentrations in different regions of dog antrum (425 +/- 50 to 773 +/- 254 ng/g tissue) are similar to those in antrum from duodenal ulcer patients and control subjects: 614 +/- 125 and 465 +/- 104 ng/g tissue respectively. Levels in histologically normal human pancreas (253 +/- 43 ng/g tissue) are comparable with those in dog pancreas (333 +/- 66 ng/g tissue), whereas in two cases of neonatal hypoglycaemia the concentration exceeded 3000 ng/g tissue. On gel chromatography the majority of immunoreactive somatostatin elutes as the synthetic tetradecapeptide and a small fraction as a larger species.

Electronimmunocytochemical evidence for the K cell localization of gastric inhibitory polypeptide (GIP) in man

Application of the semithin-thin section technique indicates that the previously proposed identification of the ultrastructurally-defined K cell with the immunocytochemically-defined GIP cell is essentially correct. The K cell is established as a distinct entity and the way is open for an explanation of its role in the physiology and pathology of the gastroenteropancreatic system.

Aldehyde fuchsin staining, direct or after oxidation: problems and remedies, with special reference to human pancreatic B cells, pituitaries, and elastic fibers

Successful production of aldehyde fuchsin (AF) having the unique properties described by Gomori depends on each of many critical variables. AF made from basic fuchsins which contain mainly rosanilin (C.I. 42510) do not stain properly-fixed pancreatic B cells, pituitary basophils, or elastic fibers in unoxidized sections. AF made from basic fuchsins containing mainly pararosanilin (C.I. 42500) stains these entities strongly. Substances stained by AF without oxidation fall into two classes: 1) nonacidic peptides and proteins, most of which contain half-cystines, and 2) polyanions, particularly when sulfated. Group 2 substances stain rapidly, Group 1 substances stain slowly. Many modifications of aldehyde fuchsin have been described. Modified aldehyde fuchsins (MAFs) differ in the kind of aldehyde and in the amount of aldehyde and hydrochloric acid used in their formulation; they differ also in the temperature and duration of the ripening necessary before they can be used. If microsections are first oxidized by acid permanganate or other oxidant, MAF staining of pancreatic B cells, pituitary basophils and other substances containing cystines is speeded and intensified. Most modified methods prescribe oxidation, but the author's does not. The chemical basis, final result and potential side-reactions of oxidation methods (OXMAF) differ from those of direct methods (DIMAF) such as the author's. DIMAF staining is slower but inherently simpler and less destructive. The time required for optimal staining with DIMAF depends on the potency of the stain, which in turn depends on how the stain was made and its age. Detection of DIMAF--reactive peptides and proteins may be hampered by the strong staining of polyanions. This can be remedied if the polyanions are first stained with Alcian blue (AB) or other durable basic dye of contrasting color resistant to acid ethanol. Experiences with the AB-DIMAF staining of pancreatic B cells, pituitaries and elastic fibers in formalin-fixed human tissues are detailed. Proper control of the variables which affect MAF will insure useful and reliable results either directly or after oxidation. Authors and editors are urged to be more careful hereafter to distinguish the results of DIMAF from those of OXMAF methods. Published reports should always specify the parameters that affect the properties of MAF. In OXMAF methods the steps intervening between oxidation and staining should be spelled out. Such care should help dispel the confusion and uncertainty which cloud the use and reputation of aldehyde fuchsin at present. This unique dye deserves wider and wiser use.

Crystalline structures in human pancreatic beta cell adenoma

An electron microscopic observation on a pancreatic tumor removed from a 34-year-old woman revealed the fine structural morphology of a functional beta cell adenoma. Characteristic PAS positive crystalline structures were frequently observed in the cytoplasm of the tumor cells. They were not bounded by a membrane and had a rectangular or irregular hexagonal shape. Highly regular patterns were seen as such as lattice or honeycomb and parallel ripple structures. They are similar to the Reinke's crystal or crystalline structures reported in human hepatocytes suffering from several different diseases and considered as a protein-carbohydrate complex. Occasionally, small paracrystalline structures appeared to indicate an immature type of these structures in the opaque fine fibrillar mass. Crystalline or paracrystalline structures were not detected in the normal pancreatic tissue removed with the tumor from the patient.

The radioimmunoassay and physiology of somatostatin in the pancreas and gastrointestinal tract

Radioimmunoassays for somatostain have demonstrated that high concentrations of the polypeptide are present in the pancreas and gastrointestinal tract of a number of species. Although measurement in tissue extracts is relatively unproblematic, detection and characterization of somatostatin-like material in plasma has proved technically difficult. Studies of pancreatic somatostatin release in vitro suggest a possible function in the regulation of islet hormone secretion, but the mode of action remains to be elucidated. Although, at present, no clinical relevance can be attributed to the somatostain radioimmunoassay reports of somatostatin secreting tumors and changes in stomach tissue content in patients with ulcer disease indicate a contributory role in the pathophysiology of certain disease states.

Localization of four polypeptide hormones in the saurian pancreas

Glucagon, insulin, somatostatin, and pancreatic polypeptide have been localized in the anolian pancreas using peroxidase-antiperoxidase immunocytochemistry. The most abundant endocrine cell type contains glucagon. Insulin-containing cells are the next most numerous. Somatostatin-immunoreactive cells tend to be localized at the periphery of the islet cords. Pancreatic polypeptide-containing cells are a minor endocrine component scattered throughout the exocrine pancreas and occasionally within the islet areas. No staining was observed after application of antigastrin serum.

The endocrine pancreas in chronic pancreatitis. Immunocytochemical and ultrastructural studies

The endocrine pancreatic tissue from patients with severe primary chronic pancreatitis (n=6). secondary chronic pancreatitis due to duct obstruction by carcinoma (n=6) and non-diabetic, non-pancreatitic controls (n=4) was studied qualitatively and quantitatively using specific immunocytochemistry and electron microscopy. Grouping of variously sized islets in the sclerotic tissue (sclerosis islets), islet neoformation by ductuloinsular proliferation, and intrainsular fibrosis were the main qualitative findings. Immunocytochemical quantitation of the distribution of insulin (B), glucagon (A), somatostatin (D) and pancreatic polypeptide (PP) producing cells revealed a significant relative increase in the number of A cells and a decrease in the number of B cells of the sclerosis islets in primary chronic pancreatitis ((B-44.1+/-9.3%:A-38.3+/-2.4%:D-8.6+/-5.1%:PP-4.6+/-4.1%) as well as in secondary chronic pancreatitis B-38.0+/-14.3%:A-38.4+/-19.0%:D-9.1+/-5.8%:PP-14.5+/-23.4%) compared with controls (B-71.1+/-8.1%:A-24.3+/-5.5%:D-8.0+/-2.8%:PP-0.5+/-0.4%). The number of PP cells was significantly increased in primary chronic pancreatitis only. It is suggested that scarring of the exocrine pancreas affects islet composition, probably by impairment of the local circulation and of glucose diffusion, thus leading to reduction of the number and glucose sensitivity of B cells. The hyperplasia of A and PP cells appears to be a secondary phenomenon due to the loss of B cells.

Characterization of Triton X 100 extracted colipase from porcine pancreas

Colipase was isolated from porcine pancreas homogenate prepared in the presence of detergent (Triton X 100). After precipitation by ammonium sulfate and ethanol, the cofactor was purified by chromatography on SP-Sephadex in the presence of Triton X 100 and on DEAE-cellulose in the absence of detergent. Two molecular forms of porcine colipase were obtained. They represent 80 per cent (colipase A) and 20 per cent (colipase B), respectively, of the total colipase. Valine is the N-terminal residue of both proteins. Their aminoacid composition is similar to that found by Borgstrom for the two forms of porcine colipase. Determination of the sequence of the first sixteen residues at the N-terminal end of colipase A indicates that the cofactor undergoes no proteolytic degradation in this region of the molecule when extraction is carried out in the presence of detergent. The recovery of colipase is about 30 per cent.

Acute hemorrhagic pancreatic necrosis in mice bile acids in gallbladder bile, serum and pancreas

Mice develop acute hemorrhagic pancreatic necrosis with fat necrosis after 4 days of feeding on a choline deficient-ethionine supplemented (CDE) diet. The diameter, weight and histopathology of the gallbladder were determined in mice fed laboratory chow (LC), a choline-supplemented (CS) diet, a choline-deficient (CD) diet, or the CDE diet for 1, 2 or 3 days. A progressive distension of the gallbladder due to accumulation of bile, was observed in mice fed the CS, CD and CDE diets. An analysis of the bile acid composition of the pancreas, serum and gallbladder bile of mice fed the same diets for 3 days was performed. No differences between control and experimental animals were seen in the concentration and distribution of bile acids in the pancreas. It is concluded that: 1) alterations in bile acid constituents are produced by the diets; and, 2) regurgitation of bile into the pancreas of mice fed the CDE diet does not occur. Thus, bile acids do not seem to initiate or participate in the extensive cellular damage that precedes and accompanies the onset of acute hemorrhagic pancreatic necrosis with fat necrosis in mice fed the CDE diet.

Heterogeneity of circulating human C-peptide

Values reported for serum C-peptide immunoreactivity in healthy individuals vary considerably. To assess factors that contribute to this finding, three human C-peptide assay systems were developed utilizing three distinct antisera that react differently with various C-peptide fragments. Preparations of natural pancreatic and synthetic human C-peptide standards were compared immunologically in these systems. The curves of the natural C-peptide and the synthetic preparations were not identical. The relative immunoreactivity of each standard varied, depending on the particular antiserum used. Serum C-peptide concentrations varied when measured in the different assay systems. Furthermore, the results of dilution and recovery tests and stability of the C-peptide during storage showed differences among the three assays. Gel filtration of serum indicated heterogeneity within the major C-peptide peak, and in addition, a smaller peak of lower molecular weight material was present in some samples. Although degradation of serum C-peptide may occur during storage, fragments of C-peptide may also be secreted or arise during in-vivo metabolism. Thus, the present studies indicate the need for careful standardization and checking of each particular assay system before its use in clinical studies.

Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency

Cobalamin (Cbl; vitamin B(12)) malabsorption in pancreatic insufficiency can be partially corrected by bicarbonate and completely corrected by pancreatic proteases but the mechanisms involved are unknown. Because saliva contains enough R-type Cbl-binding protein (R protein) to bind all of the dietary and biliary Cbl, it is possible that R protein acts as an inhibitor of Cbl absorption and that pancreatic proteases are required to alter R protein and prevent such inhibition. To test this hypothesis we studied the ability of R protein and intrinsic factor (IF) to compete for Cbl binding and ability of pancreatic proteases to alter this competition. Human salivary R protein bound Cbl with affinities that were 50- and 3-fold higher than those of human IF at pH 2 and 8, respectively. Cbl bound to IF was transferred to an equal amount of R protein with t((1/2))'s of 2 and 90 min at pH 2 and 8, respectively, and within several hours respective ratios of R protein-Cbl/IF-Cbl of 50 and 2 were observed. Cbl bound to R protein was not transferred to IF at either pH 2 or 8. Incubation of R protein with pancreatic proteases at pH 8 led to a 150-fold decrease in its affinity for Cbl. Incubation of R protein-Cbl with pancreatic proteases led to complete transfer of Cbl to IF within 10 min. Gel filtration studies with R protein-[(57)Co]Cbl and (125)I-R protein showed that pancreatic proteases partially degraded R protein. Pancreatic proteases differed in their ability to effect these changes with trypsin > chymotrypsin > elastase. Pancreatic proteases did not alter IF in any of the parameters mentioned above. Pepsin failed to alter either R protein or IF. THESE STUDIES SUGGEST THE FOLLOWING: (a) that Cbl is bound almost exclusively to R protein in the acid milieu of the stomach, rather than to IF as has been assumed previously; (b) that Cbl remains bound to R protein in the slightly alkaline environment of the intestine until pancreatic proteases partially degrade R protein and enable Cbl to become bound exclusively to IF; and (c) that the primary defect in Cbl absorption in pancreatic insufficiency is a lack of pancreatic proteases and a failure to alter R protein and effect the transfer of Cbl to IF. These studies also suggest that the partial correction of Cbl malabsorption observed with bicarbonate is due to neutralization of gastric HCl, since at slightly alkaline, pH IF can partially compete with R protein for the initial binding and retention of Cbl.

The preparation of trypsins and chymotrypsins from bovine and porcine residues after insulin extraction

Bovine and porcine pancreatic residue, remaining after the extraction of insulin, has been used to prepare a proteinase powder. This powder was used as a source of trypsin and chymotrypsin. The individual enzymes were isolated and purified by chromatography on sulfopropyl (SP) - Sephadex C-25 and affinity chromatography on soybean trypsin inhibitor (STI) - Sepharose. The bovine proteinase powder contained alpha-chymotrypsin, trypsin and chymotrypsin B in the ratio 5 : 2 : 1. The porcine powder contained cationic trypsin, anionic trypsin and cationic chymotrypsin in the ratio 5 : 1.4 : 3. The isolated enzymes were characterized and found to be identical with enzymes isolated from fresh tissue with the exception of porcine chymotrypsin. Porcine cationic chymotrypsin was isolated as two distinct forms, A-1 and A-2, which appear to be different activation products of porcine chymotrypsinogen A. Both forms resemble bovine alpha-chymotrypsin, a three chain structure, rather than porcine chymotrypsin Api, a two chain structure. Futhermore, the B-chain appears to be cleaved, possibly at residues Phe89-Lys90.