PubMed Health⌕ Search

Biomedical subjects

E Wünsch

Publications and source records attributed to E Wünsch.

At least 37 records · Page 2Linked to original sources
PubMed1988

Synthesis of the bis-cystinyl-fragment 225-232/225'-232' of the human IgGl hinge region.

In human IgGl the two heavy chains are crosslinked in the central portion of the molecule by two disulfide bridges forming a double chain bis-cystinyl cyclic peptide in parallel alignment. For our synthetic studies we have chosen the sequence portion 225-232/225'-232', i.e. [H-Thr-C1ys-Pro-Pro-C1ys-Pro-Ala-Pro-OH]2. By the use of a combination of the S-tert.-butylthio and the S-acetamidomethyl groups selective cysteine pairings in two successive steps produced the hinge hexadecapeptide in parallel and antiparallel alignment as homogeneous and well characterized compounds. Thiol disulfide interchange experiments on the antiparallel dimer led to over 90% conversion to the parallel isomer. Similarly random air-oxidation was found to generate again mainly the parallel dimer, thus strongly suggesting that this sequence portion contains sufficient structural information for a correct assembly of the two heavy chains of immunoglobulins without decisive contribution of a protein disulfide isomerase.

Amino Acid Sequence↗
PubMed1987

Synthesis of human [15-norleucine]little-gastrin-II and des-1-tryptophan-[12-norleucine]minigastrin-II.

By the use of a newly developed procedure for the synthesis of tyrosine-O-sulfate peptides based on the direct incorporation of the suitably N alpha-protected tyrosine-O-sulfate residue along the synthetic route, the synthesis of two human gastrin-II analogues was successfully accomplished. Thereby acid labile side chain protection was applied in combination with the N alpha-benzyloxycarbonyl group in the intermediate chain elongation steps. Despite the pronounced acid-lability of the sulfate ester moiety, its hydrolysis during the final acidolytic deprotection step was significantly reduced under optimized conditions. Subsequent chromatographic purification led to the two gastrin analogues in satisfactory yields as highly pure compounds as judged by various indicative analytical assays.

Amino Acid Sequence↗
PubMed1987

Studies on immunoassays of peptide factors. II. Fluorescence enzyme immunoassay for human little-gastrin.

The fluorogenic chymotrypsin substrate N alpha-(4-carboxybutyryl)-L-phenylalanine (4-methyl-7-coumaryl)amide was converted to a thiol-containing compound via its condensation at the carboxyl function with cystamine followed by reduction of the resulting disulfide compound to a cysteamine derivative. By subsequent reaction of the thiol group with N alpha-maleoyl-beta-alanyl-human-little-gastrin-I-[2-17] a fluorogenic substrate-labeled gastrin, fully immunoreactive against antigastrin antisera, was obtained. This tracer was then applied for developing a fluorescence immunoassay based on separation of bound and free tracer followed by chymotryptic digestion of the fluorogenic substrate in the supernatant. The fluorescence intensity of the extracted fluorophore i.e., 7-amino-4-methyl-coumarin, was found to monitor gastrin concentrations in a reproducible manner. With the model peptide hormone human little-gastrin-I the sensitivity of this alternative immunoassay procedure was well documented.

Amino Acids↗
PubMed1987

Influence of vasoactive intestinal peptide, secretin, and Ala4, Val5-secretin on the net movements of electrolytes, fluid, and mucus in the rat colon in vivo.

The effect of vasoactive intestinal peptide (VIP), secretin, and VIP-secretin (Ala4, Val5-secretin) on the net movements of sodium, potassium, fluid, and mucus was investigated in the rat colon perfused in vivo. Peptides (1-100 micrograms/kg.h) were infused intra-arterially. VIP influenced electrolyte and fluid movements at a threshold dose 10- to 100-fold lower than secretin, whereas the secretory efficacy was not significantly different. Replacing the NH2-terminal hexapeptide of secretin by that of VIP did not markedly alter the effect of secretin. Mucus output was stimulated weakly by all three peptides. The results indicate that the larger colonic secretory activity of VIP as compared to secretin is not primarily due to the difference in their NH2-terminal sequence but probably requires the intact molecule.

Animals↗
PubMed1987

Studies on immunoassays of peptide factors. III. Gastrin/iso-1-cytochrome C as immunogen for raising anti-gastrin antisera.

Iso-1-cytochrome c contains in penultimate position of its sequence a cysteine residue which in analogy to the known tertiary structures of cytochromes c should be exposed on the surface of the protein. Its selective reaction with N alpha-maleoyl-beta-alanyl-human-little-gastrin-I-[2-17] led to a well characterized and homogeneous gastrin conjugate to be used as immunogen in rabbits. The antisera raised by this procedure exhibited a degree of specificity for the hormone gastrin parallel to that of the gastrin receptor. This is clearly documented by comparison of the immune crossreactivities of gastrin-peptides of increasing chain length and of fragments corresponding to various regions of the hormone molecule with their biological activity. The immune response provoked in the animals by the use of an homogeneous immunogen was found to be highly reproducible in terms of specificity of the antigastrin antibodies.

Binding, Competitive↗
PubMed1987

Studies on immunoassays of peptide factors. V. Synthesis of cholecystokinin-58-[1-11]/iso-1-cytochrome c conjugate.

In previous studies on model compounds we have found that the maleimide function is sufficiently stable under the conditions of peptide synthesis to allow its incorporation at preselected positions of a peptide chain in earlier steps of the synthetic route. Taking advantage of this observation the N-terminal undecapeptide of canine cholecystokinin-58 containing at its N-terminus the maleimide group became accessible in high yields as chromatographically homogenous and analytically well characterized compound. Via the incorporated anchor group the undecapeptide was linked selectively at its N-terminus to the cysteine residue 107 of iso-1-cytochrome c to yield a well characterized conjugate of 1:1 stoichiometry for immunization experiments.

Cholecystokinin↗
PubMed1987

Studies on immunoassays of peptide factors. IV. New synthesis of a gastrin/peroxidase conjugate.

We have shown that structurally well-defined homogeneous maleoyl-peptides are synthetically accessible. These anchor-modified peptide derivatives allow their selective covalent linkage to thiol-containing proteins via the maleimide-thiol procedure. Correspondingly mercaptosuccinylated horseradish peroxidase was reacted with N alpha-maleoyl-beta-alanyl-human-little gastrin-I-[2-17] to produce the gastrin/peroxidase conjugate in good yields at 1:1 stoichiometry. The conjugate exhibited full enzymatic activity and identical binding affinity to antigastrin antisera as the parent gastrin. This approach proved to be well suited for the preparation of enzyme labeled peptide factors as tracers for immunoassays.

Enzyme-Linked Immunosorbent Assay↗
PubMed1987

Synthesis of the trypsin fragment 10-25/75-88 of mouse nerve growth factor. I. The protected tetradecapeptide 75-88.

Cyanogen bromide cleavage followed by trypsin digestion of mouse nerve growth factor (NGF) allowed the isolation of a double chain unsymmetrical cystine peptide of high neurotrophic activity. The presence of tryptophan residues severely limits the synthetic approaches for selective disulfide bridging. The strategy applied for such a purpose as well as the preparation of the suitably protected tetradecapeptide corresponding to sequence 75-88 as key intermediate for the synthesis of the NGF fragment 10-25/75-88 are described.

Amino Acid Sequence↗
PubMed1986

Synthesis of human des-tryptophan-1,norleucine-12-minigastrin-II and its biological activities.

A human minigastrin-II analog was prepared by conventional methods in solution using N-benzyloxycarbonyltyrosine O-sulfate as starting material in the synthetic route. Upon removal of the acid-labile protecting groups and purification by preparative reversed-phase chromatography the sulfated gastrin peptide was obtained in satisfactory overall yields as homogeneous material. It was found to be about twice as active as the non-sulfated form in stimulating gastric acid secretion and to exhibit a 10-fold higher affinity to gastrin receptors of purified parietal cells.

Animals↗
PubMed1986

Permeability of epidural somatostatin and morphine into the intrathecal space of dogs.

In an in vivo saline perfusate of the intrathecal space of 6 dogs, the concentration of somatostatin was determined by radioimmunoassay before and over 2 h after epidural administration of 3 mg somatostatin. The total recovered amount of somatostatin was negligible, about 0.02%. However, within 50 min after the bolus epidural injection of somatostatin, the concentration per ml perfusate increased from 0.1 +/- 0.02 ng/ml to 138 +/- 102 ng/ml (P less than 0.001) and declined to 4 +/- 1.7 ng/ml after 120 min. This increase of the somatostatin concentration by 3 orders of magnitude might explain why epidurally administered somatostatin is effective in treatment of acute and chronic pain. In a control investigation with epidural morphine in another 6 dogs to prove the feasibility of the method, the total recovered amount of morphine in the intrathecal perfusate over 2 h was about 12%.

Animals↗
PubMed1986

Secretin receptor activity in rat gastric glands. Binding studies, cAMP generation and pharmacology.

We measured 125I-secretin binding to membranes prepared from rat fundic glands and compared the abilities of natural and synthetic secretin (SN) analogs to inhibit 125I-secretin binding and to activate the cAMP generating system in glandular and subcellular preparations from the fundus and antrum. The natural peptides structurally related to porcine secretin (pSN) included: chicken secretin (cSN), vasoactive intestinal peptide (VIP), porcine peptide with N-terminal histidine and C-terminal isoleucine amide (PHI), helodermin, growth hormone releasing factors isolated from the rat hypothalamus (rhGRF-43, rhGRF-29) or from a human pancreatic tumour (hpGRF-40). These peptides inhibited the binding of 125I-secretin to rat fundic membranes: pSN greater than cSN greater than PHI, VIP and activated the cAMP generating system in fundic glands, according to the following order of potency; pSN greater than cSN greater than PHI, VIP greater than rhGRF-29 greater than rhGRF-43. Porcine peptide with N-terminal tyrosine and C-terminal tyrosine (PYY), GIP, SOM and hpGRF-40 were inactive. Structural requirements for secretin receptor activity were evaluated with four synthetic secretin analogs corresponding to porcine secretin substituted at the N-terminal end by sequence portion of VIP, GIP, GLU and SOM: Ala4-Val5-SN(VIP-SN); Tyr1-Ala2-Glu3-SN (GIP-SN); Gln3-SN (GLU-SN) and Phe1-Phe1-Trp3-Lys4-SN (SOM-SN). The relative potencies of the analogs in fundic and antral preparations were: pSN greater than VIP-SN greater than VIP, GIP-SN greater than GLU-SN greater than SOM-SN for 125I-secretin displacement and cAMP production (glandular cAMP generation and adenylate cyclase activation).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1985

Behavior of somatostatin-immunoreactive cells in the gastric mucosa before and after selective proximal vagotomy and pyloroplasty in treatment of gastric and duodenal ulcers.

Antral somatostatin-immunoreactive cells (D cells) were counted pre- and postoperatively in 20 patients with duodenal ulcer and in 8 patients with gastric ulcer. Counts were obtained either over a 2-yr postoperative period (duodenal ulcer patients) at intervals of 0.5, 1, and 2 yr or over a greater than or equal to 4-yr postoperative period (gastric ulcer patients) at intervals of 1-2 yr. In patients with a normal population of gastrin-immunoreactive cells (G cells), the D cells were within the normal range (mean value 0.53% in duodenal ulcer patients and 0.67% in gastric ulcer patients). High G-cell values were accompanied by high D-cell values (e.g., in gastrin-cell hyperplasia) and low G-cell values were accompanied by low D-cell values. The G-cell to D-cell ratio was 8:1 and 6.6:1 in duodenal and gastric ulcer patients, respectively. After selective proximal vagotomy and pyloroplasty, the following observations were made: the relation of number of G cells to number of D cells remained unchanged; the postoperative rise in G-cell population was accompanied by a rise in D-cell population; hypertrophy of the D cells was apparent as was postoperative hyperplasia, with a postoperative increase in D-cell size. Morphologic coupling of the gastrin-somatostatin system in the antrum is assumed. This is constant in ulcer disease both before and after vagotomy.

Adult↗
PubMed1985

Site-specific antibodies to rat myelin proteolipids directed against the C-terminal hexapeptide.

A site-specific antiserum against the rat myelin proteolipids was produced in rabbits by injection of a synthetic polypeptide composed of the C-terminal amino acids of the proteolipid sequence. The immunogenic hexapeptide H-Gly-Arg-Gly-Thr-Lys-Phe-OH was coupled to chicken egg-albumin with dimethylsuberimidate. Antibodies specific for this peptide reacted with the 2 myelin proteolipid protein bands after SDS polyacrylamide gel electrophoresis and electrophoretic transfer onto nitrocellulose. Immunocytochemical investigations with this anti-peptide antiserum showed that the Golgi complexes of the oligodendrocytes were highly labeled as noted previously with multivalent antibodies. Labeling of vesicles and discontinuous staining of the plasmalemma were also observed in the most actively myelinating oligodendrocytes. In contrast to previous results, the major dense line was free of staining; this may indicate that at this site the C-terminal hexapeptide is inaccessible to these antibodies and perhaps buried in the lipid bilayer, in disagreement with the proposed organization of the myelin proteolipid in the myelin membrane.

Amino Acid Sequence↗