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Biomedical subjects

W E Schmidt

Publications and source records attributed to W E Schmidt.

160 records · Page 9Linked to original sources
PubMed1987

Commercially available preparations of porcine glucose-dependent insulinotropic polypeptide (GIP) contain a biologically inactive GIP-fragment and cholecystokinin-33/-39.

Commercially available preparations of natural porcine glucose-dependent insulinotropic polypeptide (GIP) were subjected to reverse phase HPLC. The material was found to give rise to 4 peaks which were characterized by HPLC-retention time and N-terminal sequence analysis. They represented: intact porcine GIP(1-42), 58% (wt/wt); the GIP-fragment des-tyr-ala-GIP(3-42), 32% (wt/wt); cholecystokinin (CCK)-33 2% (wt/wt); CCK-39 2% (wt/wt). HPLC-pure GIP(1-42) stimulated insulin release in rat isolated pre-cultured pancreatic islets in the presence of 16.7 mM glucose up to 240% vs. control, whereas the fragment des-tyr-ala-GIP(3-42) did neither increase insulin release nor exhibit antagonistic activity to GIP(1-42) at 100 ng/ml. These results indicate that commercially available porcine GIP-preparations may contain the biologically inactive des-tyr-ala-GIP(3-42) in high amounts, and in addition may be contaminated by CCK-peptides. HPLC-characterization of these peptide preparations prior to any biological study is crucial.

Amino Acids↗
PubMed1986

Characterization of an amidated form of pancreatic polypeptide from the daddy sculpin (Cottus scorpius).

The primary structure of pancreatic polypeptide from the teleostean fish, Cottus scorpius (daddy sculpin) was established as: YPPQPESPGGNASPEDWAKYHAAVRHYVNLITRQRYNH2 The presence of a COOH-terminally alpha-amidated amino acid was established using an HPLC method of general applicability. Although the peptide shows strong homology towards anglerfish pancreatic polypeptide (86%), homology towards porcine peptide YY (PYY) (61%) and porcine neuropeptide Y (NPY) (61%) was greater than towards porcine pancreatic polypeptide (PP) (47%). This result supports suggestions that the gene duplication events which led to PP, NPY and PYY formation took place after the time of divergence of fish and mammals.

Amino Acid Sequence↗
PubMed1986

Measurement and partial characterization of the multiple forms of neurokinin A-like immunoreactivity in carcinoid tumours.

An antiserum raised against neurokinin A has been used to demonstrate storage and release of neurokinin A-like immunoreactivity by carcinoid tumours. The antiserum showed reactivity towards members of the tachykinin family of polypeptides in the order: neurokinin A greater than eledoisin greater than neurokinin B greater than kassinin greater than substance P greater than physalaemin but the magnitude of the cross-reactivity with substance P and physalaemin was less than 1% of that of neurokinin A. A sensitive (IC50 238 fmol/ml; minimum detectable concentration, 9 fmol/ml) radioimmunoassay was set up using this antiserum. Extracts of metastatic tumour tissue from four patients with a primary carcinoid tumour in the midgut contained both neurokinin A-like immunoreactivity (NKA-LI) and substance P-like immunoreactivity (SP-LI). The concentrations (pmol/g wet weight) of NKA-LI and SP-LI in the tumours were: patient A 210, 201; patient B 2276, 6849; patient C 1198, 834 and patient D 424, 379. Analysis of the tumour extracts by reverse phase HPLC indicated that the NKA-LI was heterogeneous. Under two different conditions of chromatography, one component was eluted with the same retention time as neurokinin A. Two further components were more hydrophobic than neurokinin A but were not eluted with the retention time of neurokinin B. Analysis of these components by gel filtration indicated a molecular weight in the 3000-4000 range suggesting that they may be related to neuropeptide K, an N-terminally extended form of neurokinin A. NKA-LI and SP-LI were undetectable in the plasma of patients A and D but were elevated in patient B (NKA-LI 1005 +/- 114; SP-LI 345 +/- 85 fmol/ml) and patient C (NKA-LI 80 +/- 31; SP-LI 21 +/- 13 fmol/ml).

Carcinoid Tumor↗
PubMed1986

Hypersecretion of proinsulin does not explain the hyperinsulinaemia of patients with liver cirrhosis.

A radioimmunoassay using a proinsulin-specific antiserum that does not react preferentially with the split forms of proinsulin has been used to compare the response of circulating proinsulin to low (25 g) and high (75 g) oral glucose loads in healthy subjects and in patients with liver cirrhosis. The patients were divided into two groups: Group A (n = 7) with normal glucose tolerance and Group B with diabetic (n = 5) and impaired (n = 1) glucose tolerance. There was no apparent correlation between glucose tolerance and the results of quantitative liver function tests. In the fasted state, the concentrations of serum proinsulin did not differ significantly in patients of Group A (0.022 +/- 0.002 nmol/l) or Group B (0.026 +/- 0.004 nmol/l) from those in healthy subjects (0.021 +/- 0.002 nmol/l). After 75 g glucose, the rise in serum proinsulin to a maximum concentration of 0.082 +/- 0.012 nmol/l in patients of Group A and to 0.070 +/- 0.019 nmol/l in Group B was not significantly different at any time point up to 180 min from the rise in healthy subjects (to 0.063 +/- 0.005 nmol/l). After 25 g glucose, the response of serum proinsulin in Group B patients (maximum concentration 0.035 +/- 0.003 nmol/l) was not significantly different from that in healthy subjects (maximum concentration 0.032 +/- 0.003 nmol/l) but a slightly enhanced release was observed in the Group A patients (maximum concentration 0.049 +/- 0.003 nmol/l) that was significantly greater (P less than 0.05) at 60 min post-glucose. In contrast, the concentrations of serum immunoreactive insulin and immunoreactive C-peptide in all patients with cirrhosis were significantly elevated compared with healthy subjects both in the fasted state and at several time points following high and low oral glucose. In the fasted state, the serum proinsulin/C-peptide molar ratio, an index of the relative state of secretion of proinsulin and insulin, was significantly lower (P less than 0.05) in both groups of cirrhotic patients than in healthy subjects. After high and low glucose, this ratio fell in all patients and in the healthy subjects. We conclude that cirrhosis of the liver is associated with a hypersecretion of insulin but hyperproinsulinaemia does not contribute appreciably to the elevated concentration of immunoreactive insulin in the peripheral circulation.

Adult↗
PubMed1985

Isolation and characterization of proSS1-32, a peptide derived from the N-terminal region of porcine preprosomatostatin.

A peptide derived from the N-terminal region of porcine prosomatostatin, proSS1-32, has been purified to homogeneity from extracts of porcine upper intestine. Amino acid analysis revealed that the peptide consists of 32 residues. The complete primary structure was determined as: A P S D P R L R Q F L Q K S L A A A A G K Q E L A K Y F L A E L. This sequence obviously comprises residues 1-32 of porcine prosomatostatin since it is identical to the corresponding sequence in human preprosomatostatin. The postulated cleavage site in porcine prosomatostatin is a Leu-Leu bond between residues 32 and 33, thus confirming previous studies of the processing of the somatostatin precursor in the rat and transgenic mouse.

Amino Acid Sequence↗
PubMed1985

Valosin: isolation and characterization of a novel peptide from porcine intestine.

The isolation and primary structure of a novel gastrointestinal peptide, designated valosin, is described. The peptide was purified from porcine upper gut extracts using an HPLC and N-terminal sequence screening strategy which depends on chromatographic and structural characteristics as isolation criterion. The amino acid sequence of this peptide consists of 25 amino acid residues:

Amino Acid Sequence↗
PubMed1985

The site of cyclic AMP-dependent protein kinase catalyzed phosphorylation of cytochrome P-450 LM2.

The phenobarbital-inducible form of cytochrome P-450 purified from rabbit liver microsomes is phosphorylated by cAMP-dependent protein kinase at a single site, the serine residue in position 128 of the amino acid sequence. The serine is located in a characteristic recognition sequence for cAMP-dependent protein kinase and is part of a primary structure which is conserved during evolution, present also in phenobarbital-inducible rat cytochrome and cytochrome P-450 CAM from Pseudomonas putida. The contribution of these findings to our understanding of the structure and membrane topology of cytochrome P-450 LM2 and its turnover regulated by phosphorylation is discussed.

Amino Acid Sequence↗
PubMed1985

Glucagon-like peptide-1 but not glucagon-like peptide-2 stimulates insulin release from isolated rat pancreatic islets.

Glucagon-like peptide-1 and glucagon-like peptide-2 are encoded by the m-RNA of pancreatic preproglucagon. They show high conservation in different species and substantial sequence homology to glucagon. Because no definite biological activity of these peptides has been reported, we investigated the effect of synthetic C-terminally amidated glucagon-like peptide-1 [1-36] and synthetic human glucagon-like peptide-2 [1-34] with a free C-terminus on insulin release from isolated precultured rat pancreatic islets in the presence of glucose. Glucagon-like peptide-1 stimulates insulin release at 10 and 16.7 mmol/l glucose in a dose-dependent manner. Significant stimulation starts at 2.5 nmol/l in the presence of 10 mmol/l glucose and near maximal release is observed at 250 nmol/l, with approximately 100% increase over basal at both glucose concentrations. The peptide reaches 63% of the maximal stimulatory effect of glucagon. No stimulation occurs in the presence of 2.8 mmol/l glucose. Glucagon-like peptide-2 has no effect on insulin secretion at any glucose concentration tested. It is concluded that glucagon-like peptide-1, in contrast to glucagon-like peptide-2, exhibits a glucose-dependent insulinotropic action on isolated rat pancreatic islets similar to that of glucagon and gastric inhibitory polypeptide.

Amino Acid Sequence↗
PubMed1985

Chemical and immunochemical characterisation of substance P-like immunoreactivity and physalaemin-like immunoreactivity in a carcinoid tumour.

Extracts of a carcinoid tumour, resected from the mid-portion of the ileum of a patient with no symptoms of endocrine disorder, were associated with a high concentration of substance P-like immunoreactivity. Using reverse-phase high performance liquid chromatography and antisera specifically directed against the C-terminal and N-terminal regions of substance P and against the N-terminal region of physalaemin, the following components were isolated and identified: substance P and its oxidised form, [pGlu5]substance P-(5-11) peptide and its oxidised form, and the oxidised form of physalaemin. The identity of tumour substance P with the undecapeptide was confirmed by amino acid analysis and high performance ion-exchange chromatography. In vitro incubation of tumour tissue from a lymph node metastasis from the same patient with [3H]leucine resulted in incorporation of radioactivity into newly synthesised substance P.

Carcinoid Tumor↗
PubMed1985

Scheduled breeding of gilts after estrous synchronization with altrenogest.

Fertility of 104 gilts artificially inseminated (AI) at a predetermined time (scheduled AI) after estrous synchronization with altrenogest (15 mg X gilt-1 X d-1 for 18 d) was compared with that of 103 gilts checked for estrus (estrus checked) and inseminated after altrenogest. Scheduled-AI gilts were inseminated once on d 5, 6 and 7 after the last altrenogest feeding (d 0). Estrus-checked gilts were exposed to a boar twice daily at 0830 and 1630 h and inseminated after the second and third estrous detection period following first detected estrus. Percentage of gilts assigned to treatment that farrowed (72.8 vs 67.3%), total pigs farrowed (11 +/- .4 vs 11.3 +/- .4) and pigs born alive (10.1 +/- .4 vs 10.5 +/- .4) were similar for estrus-checked and scheduled-AI gilts, respectively. We conclude that scheduled AI can be used with estrous synchronization for gilts and may have advantages in breeding herd management and the use of AI in swine.

Animals↗
PubMed1985

Reproductive traits of sows penned individually or in groups until 35 days after breeding.

We compared estrous and farrowing traits in 274 Duroc X Yorkshire sows penned either in individual gestation stalls or in groups (four or five sows/group) during the intervals from weaning to breeding and from breeding to 30 to 35 d after breeding. Sows were assigned to treatment by parity (primiparous vs multiparous), checked twice daily for estrus from 3 to 10 d after weaning and artificially inseminated (AI) twice during estrus. Ovaries of anestrous sows were examined at laparotomy. No major treatment effects on estrous response were detected and 88% (45/51) of anestrous sows had only small ovarian follicles. Litter traits were not affected by penning treatments. However, penning sows in groups postbreeding resulted in a 50% reduction (P less than .05) in early pregnancy losses as indicated by low serum progesterone 19 to 23 d after AI or return to estrus by 23 d after AI. This resulted in a 12 percentage point higher (P less than .05) farrowing rate for group-penned (78%) than for individually penned sows (66%).

Animals↗
PubMed1984

Phytoalexin synthesis in soybean cells: elicitor induction of phenylalanine ammonia-lyase and chalcone synthase mRNAs and correlation with phytoalexin accumulation.

A glucan elicitor from cell walls of the fungus Phytophthora megasperma f. sp. glycinea, a pathogen of soybean (Glycine max), induced large and rapid increases in the activities of enzymes of general phenylpropanoid metabolism, phenylalanine ammonia-lyase, and of the flavonoid pathway, acetyl-CoA carboxylase and chalcone synthase, in suspension-cultured soybean cells. The changes in phenylalanine ammonia-lyase and chalcone synthase activities were correlated with corresponding changes in the mRNA activities encoding these enzymes, as determined by enzyme synthesis in vitro in a mRNA-dependent reticulocyte lysate. The time courses of the elicitor-induced changes in mRNA activities for both enzymes were very similar with respect to each other. Following the onset of induction, the two mRNA activities increased significantly at 3 h, reached highest levels at 5 to 7 h, and subsequently returned to low values at 10 h. Similar degrees of induction of mRNA activities and of the catalytic activities of phenylalanine ammonia-lyase and chalcone synthase were observed in response to three diverse microbial compounds, the glucan elicitor from P. megasperma, xanthan, an extracellular polysaccharide from Xanthomonas campestris, and endopolygalacturonase from Aspergillus niger. However, whereas the glucan elicitor induced the accumulation of large amounts of the phytoalexin, glyceollin, in soybean cells, endopolygalacturonase induced only low, albeit significant, amounts; xanthan did not enhance glyceollin accumulation under the conditions of this study. This result might imply that enzymes other than phenylalanine ammonia-lyase or chalcone synthase exert an important regulatory function in phytoalexin synthesis in soybean cells.

Acyltransferases↗
PubMed1983

[Three-dimensional structure determination of antibodies. Primary structure of crystallized monoclonal immunoglobulin IgG1 KOL, I].

The crystallizable myeloma immunoglobulin IgG1 KOL [allotype Gm(-1,4), (gamma 1, gamma)2] which is well characterized in its three-dimensional structure by X-ray diffraction analysis of high resolution has been proved to be homogenous by polyacrylamide gel electrophoresis. The H- and L-chains were separated by gel filtration after complete reduction and carboxymethylation and were characterized by amino acid analysis, end group determination and polyacrylamide gel electrophoresis, respectively. The intact IgG1 KOL was cleaved by cyanogen bromide and all CNBr-fragments were isolated and characterized. The reduced and carboxymethylated H-chain was digested by trypsin and the tryptic hydrolysate was separated by ion-exchange chromatography. Using different procedures of rechromatography 35 out of 37 tryptic H-chain peptides could be isolated in sufficient amounts, the missing 2 peptides were produced by tryptic digestion of 2 CNBr-fragments. The amino acid sequences of all tryptic peptides were determined using a modified Edman degradation method after separation of the enzymatic cleavage products by high-performance liquid chromatography (HPLC). The complete primary structure of the VH-part of the H-chain was established by isolation and partial sequence determination of overlapping peptides obtained from cleavage of the intact H-chain by Staphylococcus aureus proteinase. The gamma 1-H-chain KOL comprises 455 amino acid residues and belongs to subgroup III. The switch from the variable to the constant part occurs at position 126/127, thus making VH-KOL one of the longest variable parts among the yet known immunoglobulin H-chains. This is due to the hypervariable region Hhv4 which is made up by 17 amino acid residues (4-9 residues more compared with other VH-parts). Within this region a so far not described additional intrapeptidal disulfide bridge could be localized (Cys 105-Cys 110) that creates a short loop with antiparallel running peptide strains in beta-pleated sheet conformation. Its role in the three-dimensional structure of the antigen-binding site of the IgG1 KOL molecule is discussed using the data obtained from X-ray diffraction analysis.

Amino Acid Sequence↗
PubMedDate not supplied

Pituitary adenylate cyclase activating polypeptide (PACAP) is a potent relaxant of the rat ileum.

The effect and mode of action of pituitary adenylate cyclase activating polypeptide (PACAP) were studied in rat ileal strips. PACAP relaxed, concentration dependently, rat ileum and was 50 times more potent than the structurally related vasoactive intestinal polypeptide (VIP). The inhibitory action of PACAP was not modified by TTX, omega-conotoxin, adrenergic, or ganglionic blockade, antagonists of adrenoreceptors and muscarinic receptors, indicating a direct myogenic effect probably through specific PACAP receptors. The lack of cross-tachyphylaxis between PACAP and VIP suggests that both peptides act by activation of distinct receptors. Structure-function analysis revealed that the N-terminal region of the PACAP molecule is crucial for biological activity.

Amino Acid Sequence↗