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At least 775 records · Page 43Linked to original sources

PubMed1999

Type I (insulin-dependent) diabetes mellitus and cow milk: casein variant consumption.

Previously published Type I (insulin-dependent) diabetes mellitus incidence in 0 to 14-year-old children from 10 countries or areas was compared with the national annual cow milk protein consumption. Countries which were selected for study had appropriate milk protein polymorphism studies, herd breed composition information and low dairy imports from other countries. Total protein consumption did not correlate with diabetes incidence (r = +0.402), but consumption of the beta-casein A1 variant did (r = +0.726). Even more pronounced was the relation between beta-casein (A1+B) consumption and diabetes (r = +0.982). These latter two cow caseins yield a bioactive peptide beta-casomorphin-7 after in vitro digestion with intestinal enzymes whereas the common A2 variant or the corresponding human or goat caseins do not. beta-casomorphin-7 has opioid properties including immunosuppression, which could account for the specificity of the relation between the consumption of some but not all beta-casein variants and diabetes incidence.

Adolescent↗

PubMed2004

Diversity of coexisting Planktothrix (cyanobacteria) chemotypes deduced by mass spectral analysis of microystins and other oligopeptides.

Cyanobacteria are reported to produce secondary metabolites of which toxic and bioactive peptides are of scientific and public interest. Many peptides are synthesized by the non-ribosomal peptide synthesis pathway and their presence is a stable feature of individual clones. We isolated 18 clonal strains of Planktothrix from a single water sample from lake Maxsee near Berlin and analyzed them by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, HPLC, and PCR for their production of peptides and the presence of microcystin synthetase genes. Microcystins could be detected in seven of the strains with considerable variability of contents and numbers of structural variants. Other known peptides like anabaenopeptins B and E/F, microviridin I, and prenylagaramide B and new variants of known peptide classes like aeruginosins and cyanopeptolins were detected in some strains while lacking in others. The 18 strains represented 15 chemotypes with respect to their peptide patterns. In contrast, all strains were morphologically very similar with respect to cell dimensions and pigmentation. Given the diversity of chemotypes among the randomly selected isolates, an immense diversity of chemotypes in the entire population can be assumed.

Bacterial Proteins↗

PubMed2005

Tripeptide tyroserleutide enhances the antitumor effects of macrophages and stimulates macrophage secretion of IL-1beta, TNF-alpha, and NO in vitro.

Tyroserleutide (YSL) is a type of active, low molecular weight polypeptide, comprised of three amino acids, which has antitumor effects. YSL has various advantages over the other bioactive peptides such as its low molecular weight, simple construction, nonimmunogenicity, specificity, few side effects, and ease of synthesis. However, the biological activities contributing to it's antitumor effects are not yet known. We studied the effects of YSL on the in vitro cytotoxic activity of BALB/c mice peritoneal macrophages (PEMphi) against the target tumor cell lines BEL-7402 and B16-F10. We also measured the concentrations of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and nitric oxide (NO) produced by YSL-activated Mphi, and we determined the concentrations of IL-1beta and NO secreted by YSL-activated murine macrophage RAW264.7 cells. YSL activated Mphi in vitro, inhibited BEL-7402 proliferation, enhanced PEMphi antitumor effects, and stimulated IL-1beta, TNF-alpha, and NO production by RAW264.7 cells. These data suggest that YSL activates the monocyte-macrophage system, which enhances Mphi antitumor effects against BEL-7402 and B16-F10 cells and stimulates the secretion by Mphi of cytotoxic effectors such as IL-1beta, TNF-alpha, and NO.

Animals↗

PubMed2000

Expression of pituitary adenylate cyclase-activating polypeptide (PACAP) and the PACAP-selective receptor in cultured rat astrocytes, human brain tumors, and in response to acute intracranial injury.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a bioactive peptide with diverse activities in the nervous system. In addition to its more classic role as a neurotransmitter, PACAP functions as a neurotrophic factor. PACAP exerts these activities by binding to PACAP-selective (PAC1) or nonselective (VPAC1, VPAC2) receptors (-R). Glial cells also exhibit PACAP binding, which is associated with the increased proliferation of astrocytes. The present report demonstrates a distinct spatiotemporal regulation of PACAP, PAC1-R, VPAC1-R, and VPAC2-R expression in primary cultured rat astrocytes. To determine the role of PACAP and PAC1-R expression on glial proliferation, two in vivo models were examined--human brain tumors of glial origin and the reactive gliosis induced by a penetrating stab wound to the mature rat brain. Relative to normal human brain, PAC1-R expression is significantly upregulated in glioma, particularly oligodendrogliomas. While similar polymerase chain reaction (PCR) analysis does not detect PACAP expression, in situ hybridization studies reveal PACAP expression in a limited number of cells within the tumor. In sharp contrast, neither PACAP nor PAC1-R expression are upregulated consequent to injury. These results suggest a distinct role for PACAP and PAC1-R in glioma development and nervous system response to injury.

Adult↗

PubMed2004

Distribution of apelin, the endogenous ligand of the APJ receptor, in the lizard Podarcis sicula.

Apelin is a novel bioactive peptide that has been isolated from bovine stomach extracts and identified as the endogenous ligand for the APJ receptor. Although the main physiological functions of apelin have not yet been clarified, it is known that apelin is involved in the regulation of blood pressure, central control of body fluid homeostasis and the modulation of immune response. In order to investigate the distribution of apelin in reptiles, we have performed an immunohistochemical analysis on tissues of the lizard Podarcis sicula. The peptide was found to be widely distributed, although its cellular localization differed in the various organs examined. A strong immunopositivity was found in the heart, stomach and intestine. In the spleen, an intense apelin immunopositivity was restricted to a discrete number of cells scattered throughout the red pulp and co-localized with immunoglobulin kappa and lambda chains, suggesting an analogous function of this peptide in immune responses also in reptiles. Intriguingly, apelin immunoreactivity was discretely localized in endothelial cells in the lung and thyroid gland. In the light of these data, we conclude that apelin may have multiple functions in reptiles.

Animals↗

PubMed2005

Role of angiotensin III in hypertension.

The hyperactivity of the brain renin-angiotensin system (RAS) has been implicated in the development and maintenance of hypertension in several types of experimental and genetic hypertension animal models. Among the main bioactive peptides of the brain RAS, angiotensin (Ang) II and Ang III display the same affinity for type 1 and type 2 Ang II receptors. Both peptides, injected intracerebroventricularly, similarly increase blood pressure (BP); however, because Ang II is converted in vivo to Ang III, the identity of the true effector is unknown. In this article, we review new insights into the predominant role of brain Ang III in the control of BP, underlining the fact that brain aminopeptidase A (APA), the enzyme-forming central Ang III, could constitute a putative central therapeutic target for the treatment of hypertension. This justifies the development of potent systemically active APA inhibitors, such as RB150, as prototypes of a new class of antihypertensive agents for the treatment of certain forms of hypertension.

Angiotensin III↗

PubMed1989

Radiometric assay for carboxypeptidase H (EC 3.4.17.10) and other carboxypeptidase B-like enzymes.

Carboxypeptidase H, EC 3.4.17.10, also known as enkephalin convertase, carboxypeptidase E, and crino carboxypeptidase B, is an important enzyme involved in the biosynthesis of bioactive peptides. To assay the enzyme, tissues are homogenized in at least 20 vol (ml/g) of 0.025 M Tris-HCl buffer, pH 8, with 5 mg/ml of bovine serum albumin. After centrifugation, the supernatant is brought to pH 5.6 and centrifuged again. Following a 20-min preincubation in 2 mM CoCl2, the supernatant is incubated with 0.1 mM (final concentration) of the radioactive substrate [3H]benzoyl-Phe-Ala-Arg. The 100-microliters assay is stopped by the addition of 680 microliters of acetonitrile/0.25 M HCl (0.7/1). The 1.5-ml tube is transferred into a scintillation vial and is flushed with 4 ml of Econofluor, a water-immiscible scintillation fluid. The product, [3H]benzoyl-Phe-Ala, recovered in the organic phase, is counted directly with no interference from the substrate remaining in the aqueous phase. The blank is below 1%. Expressed in nanomoles per minute per milligram of tissue, the activity of the soluble enzyme in rat is 0.34 for striatum, 21.0 for pancreatic islet, 16.6 for anterior pituitary, 46.0 for intermediate pituitary, and 10.9 for neural pituitary. In every case 25 microM guanidinoethylmercaptosuccinic acid, an active site-directed inhibitor of carboxypeptidase H, completely inhibits the activity.

Animals↗

PubMed1986

Characterization of neuromedin U like immunoreactivity in rat, porcine, guinea-pig and human tissue extracts using a specific radioimmunoassay.

Two novel bioactive peptides termed neuromedin U-8 and neuromedin U-25 have recently been isolated from porcine spinal cord but nothing is known of their occurrence and molecular forms in other species. Following gel permeation chromatography, a specific radioimmunoassay detected only a single molecular form of neuromedin U-like immunoreactivity (NmU-LI) in rat, porcine and human central nervous system and gastrointestinal tract. Only guinea pig tissue extracts revealed two molecular forms of NmU-Li. Reverse phase high performance liquid chromatographic (HPLC) analysis demonstrated that porcine NmU-LI co-eluted with synthetic neuromedin U-25 standard. Human and rat NmU-LI however, was more hydrophobic on HPLC thus indicating species differences.

Animals↗

PubMed1989

An arginine specific carboxypeptidase generated in blood during coagulation or inflammation which is unrelated to carboxypeptidase N or its subunits.

An unstable carboxypeptidase N or B like enzyme is generated as a result of coagulation. This enzyme is derived from some plasma component (s) and not from blood cells or platelets. Furthermore, the activity generated is specific for arginine substrates insofar as small synthetic substrates are concerned. The enzyme is unrelated to CPN or any of its subunits or subunit fragments. This transient carboxypeptidase may be involved in the processing and/or scheduling of different functions of bioactive peptides generated during inflammation.

Arginine↗

PubMed1991

Isolation of four novel tachykinins from frog (Rana catesbeiana) brain and intestine.

In a survey for unknown bioactive peptides in frog (Rana catesbeiana) brain and intestine, we isolated four novel peptides that exhibit potent stimulant effects on smooth muscle preparation of guinea pig ileum. By microsequencing and synthesis, these peptides were identified as Lys- Pro- Ser- Pro- Asp- Arg- Phe- Tyr- Gly- Leu- Met- NH2 (ranatachykinin A), Tyr- Lys- Ser- Asp- Ser- Phe- Tyr- Gly- Leu- Met- NH2 (ranatachykinin B), His- Asn- Pro- Ala- Ser- Phe- Ile- Gly- Leu- Met- NH2 (ranatachykinin C) and Lys- Pro- Ans- Pro- Glu- Arg- Phe- Tyr- Ala- Pro- Met- NH2 (ranatachykinin D). Ranatachykinin (RTK) A, B and C conserve the C- terminal sequence, Phe- X- Gly- Leu- Met- NH2, which is common to known members of the tachykinin family. On the other hand, RTK-D has a striking feature in its C-terminal sequence, Phe- Tyr- Ala- Pro- Met- NH2, which has never been found in other known tachykinins, and may constitute a new subclass in the tachykinin family.

Amino Acid Sequence↗

PubMed1988

Comparison of a carboxypeptidase E-like enzyme in human, bovine, mouse, Xenopus, shark and Aplysia neural tissue.

Several diverse species contain an enzyme with many properties in common with those of bovine carboxypeptidase E (CPE), a neuropeptide processing carboxypeptidase B-like enzyme. This enzyme has been designated EC 3.4.17.10, and is also known as enkephalin convertase and carboxypeptidase H. All tissues that are known to contain bioactive peptides also contain CPE-like enzymatic activity. In Xenopus laevis, enzyme activity is highest in the brain and pituitary, lower in the skin, and undetectable in liver and gut. In Aplysia californica, enzyme activity is highest in the atrial gland, but is also present in moderate amounts in the various neural tissue. CPE extracted from human, bovine, mouse, Xenopus, shark, and Aplysia neural tissue is substantially purified using substrate affinity chromatography and concanavalin A sepharose columns. The partially purified enzyme from all species examined possess very similar enzymatic properties. These properties include a pH optimum of 5.6, a stimulation by cobalt chloride, and an inhibition by chelating agents (1,10-phenanthroline). Arginine-derived active site-directed inhibitors show similar inhibition constants (Ki's) towards enzyme from the various species, whereas lysine-derived inhibitors are substantially less potent towards the Aplysia carboxypeptidase than towards enzyme isolated from the other species. The similar properties of the carboxypeptidase isolated from the various species suggests that a CPE-like is involved in the biosynthesis of many peptide neurotransmitters and hormones in a wide range of organisms.

Animals↗

PubMed1989

A bag cell neuron-specific antigen localizes to a subset of dense core vesicles in Aplysia californica.

The bag cell neurons of Aplysia govern egg-laying through the release of a number of bioactive peptides which are processed from a common precursor. Immunoelectron microscopic studies suggest that sorting at the trans-Golgi segregates peptides from the amino terminal and carboxy terminal of the precursor into distinct classes of dense-cored vesicles (DCVs). Here we identify a novel bag cell-specific antigen (4F6 antigen) using monoclonal antibodies (MAbs). Immunoprecipitations and Western blots demonstrate that the MAb4F6 specifically recognizes a protein of 80 kDa and does not react with the egg-laying hormone precursor, processing intermediates or final products. The 4F6 antigen is localized in a subset of DCVs which also contain peptides derived from the amino terminus of the precursor. These results further demonstrate the complexity of vesicular sorting in the bag cells and also identify a novel tissue specific antigen localized to DCVs.

Animals↗

PubMed1992

Immunocytochemical localization of endopeptidase 24.15 in rat brain.

Endopeptidase 24.15 (EC 3.4.24.15; EP 24.15), a zinc-metalloendopeptidase highly active in rat testes, brain and pituitary, converts some prodynorphin- and proenkephalin-derived oligopeptides into the corresponding enkephalins and degrades a variety of bioactive peptides including bradykinin, neurotensin, and both angiotensin I and II. The immunocytochemical localization of the enzyme was studied in rat brain using a polyclonal antibody raised in rabbits against a homogeneous preparation of the enzyme isolated from rat testes. The distribution of EP 24.15 immunoreactivity in the brain was widespread, being present in both neurons and glial cells. Surprisingly, however, staining was predominantly nuclear, and not cytoplasmic as expected based on the biochemical demonstration that EP 24.15 activity is predominantly associated with the soluble protein fraction of brain homogenates. Cytoplasmic staining was detected in large neurons but was less intense than the nuclear staining. The highest density of EP 24.15-staining was detected in nuclei of cerebellar Purkinje cells and in hippocampal dentate gyrus cells. High levels of immunoreactivity were also noted in brain areas which contain peptides known to be substrates of the enzyme in vitro. This localization supports a role for EP 24.15 in neuropeptide metabolism, but also suggests an as yet undefined role in nuclear function.

Animals↗

PubMed1995

[3H]BQ-123, a highly specific and reversible radioligand for the endothelin ETA receptor subtype.

The mode of binding of [3H]BQ-123 (cyclo(-D-Trp-D-Asp-[prolyl-3,4 (n)-[3H]]Pro-D-Val-Leu)), an endothelin receptor antagonist radioligand, was evaluated in the human neuroblastoma cell line SK-N-MC at 37 degrees C. Scatchard analysis indicated the presence of a single class of [3H]BQ-123 binding sites with a high affinity of 3.2 nM. [3H]BQ-123 binding achieved steady state within 7 min and dissociated with a half-time of 1.4 min, while [125I] endothelin-1 binding barely reached a steady state even after 6 h and showed little dissociation. [3H]BQ-123 binding was sensitive to endothelin-1 and endothelin-2 (Ki values = 0.058 and 0.10 nM, respectively) and the endothelin ETA receptor-selective antagonist BQ-123 (Ki = 3.3 nM), while showing low affinity for endothelin-3 (Ki = 50 nM), the endothelin ETB receptor-selective agonist BQ-3020 (Ki = 970 nM) and other bioactive peptides. Thus, [3H]BQ-123 is a specific and reversible radioligand for endothelin ETA receptors. The rapid reversibility of [3H]BQ-123 binding should provide a tool for estimating the equilibrium inhibition constants (Ki values) of various compounds for endothelin ETA receptors.

Amino Acid Sequence↗

PubMed1996

Ramiprilat attenuates hypoxia/reoxygenation injury to cardiac myocytes via a bradykinin-dependent mechanism.

Isolated rat neonatal cardiac myocytes were subjected to immersion in hypoxic (PO2 < 2 mm Hg), glucose-free Tyrode's solution for 5 h followed by concomitant reoxygenation and staining with the membrane-impermeant fluorophore, propidium iodide, in normoxic (PO2 > 150 mm Hg), serum-free culture media for 15 min in order to assess sarcolemmal damage indicative of myocyte viability due to hypoxia/reoxygenation injury. Prior to hypoxic exposure, cells were pretreated for 90 min with the angiotensin-converting enzyme inhibitor cyclopenta[b]pyrrole-2-carboxylic acid, 1-[2-[(1-carboxy-3-phenylpropyl)amino]-l-oxopropyl]octahydro-[2S-[1[R* (R*)]2 alpha, 3a beta, 6a beta]] (ramiprilat), concomitantly with ramiprilat and H-D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg-OH (bradykinin B2 receptor antagonist HOE 140), the bioactive peptide Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (bradykinin) or concomitantly with bradykinin and HOE 140. Hypoxia/reoxygenation injury to untreated control cardiac myocytes was characterized by a significant loss of sarcolemmal integrity measured at 75 +/- 4% of total cell fluorescence (mean +/- S.E., n = 42 cultures). Compared to propidium iodide staining of the above untreated control myocytes, those pretreated with 30 or 100 microM ramiprilat showed a significant reduction of propidium iodide staining to 45 +/- 9% and 40 +/- 8% (n = 9, P < 0.05) of untreated controls, respectively. Pretreatment with the protective concentrations of ramiprilat concomitant with 10 microM HOE 140 abolished the significant reduction in propidium iodide staining observed with ramiprilat alone. Similarly, pretreatment with 10 or 100 nM bradykinin significantly reduced propidium iodide staining to 35 +/- 5% and 60 +/- 10% (n = 6, P < 0.05) of the untreated hypoxic controls, respectively. In addition, concomitant pretreatment with protective concentrations of bradykinin and 10 microM HOE 140 also abolished the significant reduction in propidium iodide staining observed with bradykinin alone. The results indicate that the angiotensin-converting enzyme inhibitor ramiprilat has a protective effect on isolated cardiac myocytes exposed to hypoxia/reoxygenation and that this effect is most likely related to a local action of bradykinin on the cardiac myocyte via the activation of the kinin B2 receptor.

Analysis of Variance↗

PubMed1994

Distribution and characterization of immunoreactive rat adrenomedullin in tissue and plasma.

Adrenomedullin is a new bioactive peptide recently isolated from pheochromocytoma. We report on the rat adrenomedullin distribution and molecular forms in various tissues and plasma. Using a sensitive radioimmunoassay system for rat adrenomedullin, high concentrations of immunoreactive rat adrenomedullin were detected in adrenal gland, lung and cardiac atrium. In lung and atrium, the immunoreactivity concentration in rat was about 6-10 times higher than that in human. The mean plasma concentration of immunoreactive rat adrenomedullin was 3.60 +/- 0.34 fmol/ml (mean +/- S.D.). Analysis in adrenal gland, lung and atrium with reverse-phase and gel-filtration high-performance liquid chromatography showed that most immunoreactive rat adrenomedullin emerged as a single peak at a position exactly identical to that of the authentic rat adrenomedullin peptide, synthesized according to the sequence predicted from the cDNA.

Adrenal Glands↗

PubMed1995

cDNA and deduced amino acid sequence of human PK-120, a plasma kallikrein-sensitive glycoprotein.

PK-120 is a substrate for plasma kallikrein (PK), recently purified from human plasma. Here we have established the cDNA sequence for human PK-120 mRNA. The deduced amino sequence of PK-120 revealed that it consists of 902 amino acid residues with a calculated mass of 116,423 Da. The putative cleavage sites by PK have been proposed, suggesting that PK-120 may be a precursor of a bioactive peptide. Most interestingly, PK-120 showed significant sequence identities to heavy chains (HCs) of the inter-alpha-trypsin inhibitor (ITI) superfamily.

Amino Acid Sequence↗

PubMed1990

Effect of ingested carbohydrate, fat, and protein on the release of somatostatin-28 in humans.

The level of somatostatin-28, a bioactive peptide derived from pro-somatostatin in gastrointestinal epithelial cells, increases in human plasma after food intake. To determine if an equivalent response occurs with individual components of a mixed meal, somatostatin-28 and prosomatostatin, somatostatin-14, and somatostatin-13, in combination, were measured in healthy men before and after intake of (a) a mixed meal (715 kcal), (b) carbohydrate (100 g equivalent glucose), (c) protein (22 and 45 g), and (d) fat (25 and 50 g). After the mixed meal, somatostatin-28 levels doubled within 120 min and gradually declined by 4 h. With carbohydrate, somatostatin-28 levels were unaltered. After 22 and 45 g of protein, somatostatin-28 increased equivalently within 60 min, representing 30% of the amount with the mixed meal. With 25 g fat, a somatostatin-28 increase similar to that with the meal was seen; this response was doubled with 50 g fat. No changes in prosomatostatin, somatostatin-14, or somatostatin-13 were observed with the mixed meal or with the separate macronutrients. The authors conclude that fat is the major stimulus for somatostatin-28 secretion in humans and hypothesize that somatostatin-28 is an inhibitor of the endocrine and exocrine pancreas during nutrient absorption.

Adult↗