Solid phase peptide synthesis of human endothelin precursor peptide using two-step hard acid deprotection/cleavage methods

Syntheses are described for the putative human and porcine biosynthetic precursors (hET-38 and pET-39) of endothelin, with the sequence previously deduced from human- and porcine-cDNA coding for prepro-endothelin. The Boc based solid phase synthetic method was applied, followed by weak hard acid, trimethylsilyl bromide, cleavage. The peptide removal from the resin was optimally accomplished with hydrogen fluoride. Disulfide bridges were formed by air-oxidation, and the linkage modes determined by enzymic (Endoproteinase Asp-N) digestion and HPLC. Five additional C-terminally elongated endothelin homologs were also synthesized. For alternative synthesis of pET-39, the use of trimethylsilyl tri-fluoromethanesulfonate for the removal of peptide from the resin generated a major side product, which was characterized. hET-38 was found to be less effective in vitro, when compared to endothelin. The vasoconstrictor activity in vitro of other related peptides was comparable to that of hET-38.     

Measurement of β-Adrenergic Receptors on Lymphocytes in Normal Subjects and Asthmatics in Relation to β-Adrenergic Hyperglycaemic Response and Bronchial Responsiveness

The numbers of beta-adrenergic receptors on lymphocytes in normal subjects and asthmatic patients were measured by the use of [125I]hydroxybenzylpindolol. The numbers of beta-adrenergic receptors per lymphocyte in normal subjects, drug-free asthmatics and patients taking beta-stimulants were 1146 +/- 98, 845 +/- 114 and 582 +/- 47 sites/cell (mean +/- SE), respectively. The differences were statistically significant (P less than 0.05) among these groups, while no statistically significant differences were found in dissociation constants. A 42% decrease in the number of beta-adrenergic receptors per lymphocyte after administration of 6 mg/day of terbutaline for 7 days was noted in four volunteers. There was significant correlation (r = 0.68, P less than 0.01) between the number of beta-adrenergic receptors per lymphocyte and the percentage increase in blood sugar 20 min after subcutaneous injection of 4 micrograms/kg epinephrine. There was also significant correlation (r = 0.78, P less than 0.005) between the number of beta-adrenergic receptors per lymphocyte and the respiratory threshold for acetylcholine. These results suggest that beta-blockade and bronchial hypersensitivity in asthmatic patients may in part be due to a decreased number of beta-adrenergic receptors.     

A Case of Neurofibromatosis of the Whole Gastrointestinal Tract

An unusual case of neurofibromatous of the gastrointestinaltract is described. Diffuse neurofibromatous involvement ofthe whole gastrointestinal tract was incidentally found in acancer patient at autopsy. Immunohistochemical examination fornervous tissue-specific S100 protein was helpful in identifyingthe tumor cells as neurogenic cells.     

Exocrine Pancreatic Function Test by a Synthetic Peptide

A new synthetic substance, N-Benzoyl-L-tyrosyl-p-aminobenzoic acid, is specially cleaved by pancreatic chymotrypsin after oral administration and the released p-aminobenzoic acid (P.A.B.A.) is absorbed and excreted in the urine. The P.A.B.A. recovery in the urine was examined to evaluate its diagnostic value as an exocrine pancreatic function test. The data permit the following conclusions: 1. There is a significant correlation between this test and maximal bicarbonate concentration, amylase output and volume of P.Z./C.C.K. secretin test. 2. More than one-half to two-thirds proximal or one-third distal of the pancreas must be removed before one can expect an abnormal result in this test. 3. This is a simple and useful test to detect exocrine pancreatic insufficiency of more than moderate degree but normal results may be obtained in minimal to mild exocrine pancreatic insufficiency. Only six of 11 cases (54.5%) with one abnormal factor of P-S test showed decreased P.A.B.A. recpvery, whereas 22 of 23 cases (95.7%) with two or three abnormal factors of P-S test showed decreased or borderline P.A.B.A. recovery.