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At least 757 records · Page 42Linked to original sources

PubMed1994

Calyculin A, a non-phorbol ester type tumor promotor, induced oxidative DNA damage in stimulated human neutrophil-like cells.

Calyculin A(CA) induced 8-hydroxydeoxyguanosine (8OHdG), typical of mutagenic oxidative DNA damage, in N-Formyl-Methionyl-Leucyl-Phenylalanine (FMLP)-stimulated dimethyl sulfoxide(DMSO)-differentiated HL60(DMSO-HL60), which has characteristics similar to those of human neutrophils. CA enhanced O2-generation in FMLP-stimulated DMSO-HL60. CA by itself neither induced 8OHdG nor O2-generation. FMLP by itself induced O2-generation, however, it did not induce 8OHdG. These findings suggest that CA exerts its tumor promotion activity through modulating O2-generation and through inducing oxidative DNA damage and that a common bioactive peptide induces oxidative DNA damage under a certain condition.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1996

Proton magnetic resonance studies of methionine enkephalin.

In the literature there exist two conflicting pieces of data concerning the thermodynamics of the Cu(2+)-methionine enkephalin complex. One study utilized 1H nuclear magnetic resonance (NMR) to study the solution phase Cu(2+)-enkephalin binding and reported a strong interaction over a wide pH range. Another study utilized potentiometry to measure a log beta 101 of 4.6, a value representative of a weak metal-ligand complex. In order to resolve this discrepancy a 300 MHz 1H NMR is used to study the protonation sequence of methionine enkaphalin, a bioactive peptide, and its complexation with seven diamagnetic metals (Ba2+, Ca2+, Zn2+, La2+, Mg2+, Sr2+ and Cd2+).

Acetic Acid↗

PubMed1998

Bactericidal domain of lactoferrin: detection, quantitation, and characterization of lactoferricin in serum by SELDI affinity mass spectrometry.

Lactoferricin is a bioactive peptide fragment (3196 Da) derived from lactoferrin (80 kDa) that contains the bactericidal domain and the lymphocyte receptor-binding domain of lactoferrin. Although lactoferricin has been produced from lactoferrin by proteolytic digestion in vitro, its natural occurrence and distribution in vivo are still not clear, in part because of the absence of a suitable detection means. Surface-enhanced laser desorption/ionization (SELDI) was used to detect and characterize lactoferricin by affinity mass spectrometry. Human, porcine, and bovine lactoferricin in unfractionated serum samples were found to bind specifically to ligands presenting a terminal n-butyl group. SELDI was used to detect and quantify each species of lactoferricin in a manner that was independent of the presence of intact lactoferrin, partially degraded lactoferrin, and lactoferrin peptides containing the lactoferricin peptide sequence. The limit of detection of bovine lactofericin in serum was as low as 200 pg/ml. The FKCRRWQWR-homoserine/-homoserine lactone moiety of bovine lactoferricin, which includes the complete antimicrobial center (i.e., RRWQWR), was shown to be responsible for interaction with the n-butyl group. The SELDI procedure defined here is the only molecular recognition tool known to date that is capable of distinguishing the multi-functional lactoferricin domain located within structurally related but distinct forms of lactoferrin and its metabolic fragments. Enabling the direct quantitation of lactoferricin produced in vivo opens new opportunities to evaluate lactoferrin function.

Amino Acid Sequence↗

PubMed2000

Structure of human neutral endopeptidase (Neprilysin) complexed with phosphoramidon.

Neutral endopeptidase is a mammalian type II integral membrane zinc-containing endopeptidase, which degrades and inactivates a number of bioactive peptides. The range of substrates cleaved by neutral endopeptidase in vitro includes the enkephalins, substance P, endothelin, bradykinin and atrial natriuretic factor. Due to the physiological importance of neutral endopeptidase in the modulation of nociceptive and pressor responses there is considerable interest in inhibitors of this enzyme as novel analgesics and anti-hypertensive agents. Here we describe the crystal structure of the extracellular domain (residues 52-749) of human NEP complexed with the generic metalloproteinase inhibitor phosphoramidon at 2.1 A resolution. The structure reveals two multiply connected folding domains which embrace a large central cavity containing the active site. The inhibitor is bound to one side of this cavity and its binding mode provides a detailed understanding of the ligand-binding and specificity determinants.

Amino Acid Sequence↗

PubMed1994

Cellular distributions of the prohormone processing enzymes PC1 and PC2.

The prohormone convertases PC1 (also known as sPC3) and PC2 are known to mediate the proteolytic conversion of inactive neuropeptide and hormone precursors to bioactive peptide products. In this study we have used sucrose density centrifugation to determine the subcellular distributions of the various forms of PC1 and PC2 in three different cell types, AtT-20, beta TC3, and PC12 cells. The former two cell lines naturally express PC enzymes, while PC12 cell clones expressing PCs were obtained by stable transfection. Our data show considerable cell-line specific variation in PC processing, with PC12 cells exhibiting the most complete processing of both enzyme precursors. While in all cell lines mature forms of both enzymes were stored within particles having the same buoyant density as secretory granule markers, in some cell lines substantial amounts of mature PC1 and PC2 were also associated with the Golgi marker. Processing of the two PC precursors was not interdependent since PC12 cells expressing only one of the two PCs were fully capable of enzyme maturation. Interestingly, analysis of intracellular processing of an endogenous peptide precursor, proneurotensin, revealed that transfected PC1, but not PC2, showed enzymatic activity against this precursor.

Animals↗

PubMed1993

Role of the Na+,K+ pump in herpes simplex type 1-induced cell fusion: melittin causes specific reversion of syncytial mutants with the syn1 mutation to Syn+ (wild-type) phenotype.

To evaluate the importance of the Na+,K+ pump and ionic gradients in virus-induced cell fusion, we investigated the effects of melittin, a 26 amino acid bioactive peptide found in honey bee venom, on cell fusion caused by HSV-1 syncytial mutants. Melittin inhibited fusion of Vero cells caused by HSV-1 mutant viruses mP(MP), KOS (syn20) and KOS (FFV3) containing the syncytial mutation syn1 in glycoprotein K. However, it did not affect cell fusion caused by mutants HFEM(tsB5) or KOS amb1511-7 with mutations in glycoprotein B. Melittin caused specific reversion of syn1 mutant virus plaques to syn+ (wild-type) plaque morphology, and inhibited virus adsorption and penetration. It also inhibited the Na+,K+ pump activity, and the binding of 3H-ouabain to the Na+,K+ pump of infected Vero cells. The Na+,K+ pump activity of infected Vero cells in comparison to mock-infected cells was significantly decreased. Ouabain, a specific inhibitor of the Na+,K+ pump, inhibited fusion of Vero cells caused by all syncytial virus strains.

Animals↗

PubMed1995

Glycoproteins of the aspartyl proteinase gene family secreted by the developing placenta.

Pregnancy in cattle and sheep can be diagnosed by the presence of placentally-derived antigens (pregnancy-associated glycoproteins or PAG-1) in maternal serum soon after implantation begins at about Day 20 following conception. Molecular cloning of their cDNA has revealed that PAG-1 belong to the aspartic proteinase gene family and have about 50% amino acid sequence identity to pepsin. However, critical amino acid substitutions at the active site regions suggest that both bovine and ovine PAG-1 are enzymatically inactive. PAG-1 expression has been shown by in situ hybridization and immunocytochemistry to be localized to the trophoblast binucleate cells, which invade maternal uterine endometrium during implantation. The glycoproteins are concentrated in dense cytoplasmic granules that are discharged after the binucleate cells have migrated to the maternal side of the placental barrier. We suggest, therefore, that the PAG-1 might have an endocrine function either as carriers of other bioactive peptides or by acting as hormones themselves. Recently screening of placental libraries with nucleic acid probes has identified additional cDNA that are very abundant and code for polypeptides (PAG-2 and PAG-3) related to, but antigenically and structurally distinct from PAG-1 described above. These molecules have sequences of amino acids at their catalytic centers that are consistent with their being potentially functional proteinases but their role during pregnancy, like that of PAG-1, is unclear.

Amino Acid Sequence↗

PubMed1995

Endocrine, paracrine and autocrine regulation of testicular steroidogenesis.

Testicular steroidogenesis takes place almost exclusively in Leydig cells. Some metabolism of the androgens produced by Leydig cells takes place in seminiferous tubules, especially in the immature animal (e.g. aromatization and 5 alpha- reduction). Luteinizing hormone (LH) is the main tropic regulator of Leydig cell function, without which quantitatively important androgen production is not possible. LH acts through a receptor that belongs to the seven times cell membrane spanning, G protein associated, receptor family, and cyclic AMP is the main second messenger of its signal transduction. Information about the involvement of other signal transduction systems in LH action has also emerged recently. The action of LH is under manyfold modulation by other hormones (e.g. prolactin, growth hormone and insulin), growth factors and bioactive peptides. In this modulation, various paracrine and autocrine mechanisms play an important role. Seminiferous tubules influence the development and function of adjacent Leydig cells through several growth factors. When germ cells are damaged, Leydig cells in the vicinity proliferate faster. Leydig cell morphology also depends on the germ cell composition in the neighbouring seminiferous tubules, and certain stages of the seminiferous epithelial cycle increase the Leydig cell capacity to produce testosterone. Also negative modulation of Leydig cells by Sertoli/germinal cell derived factors has been demonstrated. However, the physiological importance of the paracrine and modulatory influences of the different hormones and growth factors still remains obscure since almost all information has so far been obtained from in vitro studies. In the study of testicular steroidogenesis, the main switch of the function, LH action, is well known whereas the role of the "in house" circuits of paracrine and autocrine regulation remain to be elucidated.

Amino Acid Sequence↗

PubMed1987

Serotonin-immunoreactive cells of peculiar shape in the urethral epithelium of the human penis.

The present study deals with endocrine-like cells in the urethra of human penis. A large number of basal-granulated cells immunoreactive for serotonin were dispersed in the urethral epithelium. No cellular elements were stained positively with antisera against bioactive peptides. The serotonin-immunoreactive cells consisted of a small oval perikaryon and slender processes, and resembled neurons in shape. An apical process reached the urethral lumen. The basal processes frequently branched out in a dendritic fashion, some running laterally for a considerable distance. The number of cells immunoreactive for serotonin was remarkably reduced in subjects over 60 years of age.

Aged↗

PubMed1989

Development of Xenopus laevis skin glands producing 5-hydroxytryptamine and caerulein.

The granular glands in Xenopus laevis skin are known to contain large quantities of biogenic amines and bioactive peptides which closely resemble mammalian brain-gut peptides. We studied the development of glands producing 5-hydroxytryptamine (5-HT) and caerulein using immunohistochemistry, HPLC-fluorometric systems and RIA. The immunoreactivities of 5-HT and caerulein were first detected in the spherical gland rudiments in the stratum spongiosum at St. 58 (Nieuwkoop and Faber stage), or at the beginning of metamorphosis. Both immunoreactivities appeared in the same rudiment at the same time. Some of the gland rudiments have a small lumen filled with both immunoreactive materials at St. 58-59. During the rest of the metamorphic period, the glands grow in size, accumulating immunoreactive materials in the lumen. The concentrations of 5-HT and caerulein in the skin of tadpoles were below 1 ng per mg wet tissue at St. 58-59, increased as metamorphosis proceeded and reached 63 and 134 ng per mg wet tissue at St. 66, or at the end of metamorphosis, respectively. The amphibian granular glands where large quantities of biogenic amines and hormone-like peptides are rapidly synthesized may provide a useful model for the study of the development of amine- and peptide-producing cells including neurons and paraneurons.

Animals↗

PubMed1977

The ventricular system in neuroendocrine mechanisms. III. Supraependymal neuronal networks in the primate brain.

This investigation has utilized a correlative scanning-transmission electron microscopic technique in the analysis of the primate cerebral ventricular system. This approach has demonstrated a complex network of supraependymal cellular elements upon the walls of the third cerebral ventricle in direct contact with the ventricular lumen. Type I neuronal-like cells and type II histiocytic-like cells with potential phagocytic capabilities have been observed in large numbers throughout the third ventricle. Type I neuron-like cells are discussed in the context that they may represent a population of receptor-cells which serve to assess ambient changes in the composition of bioactive peptides in the cerebrospinal fluid and may serve as a supraependymal network that integrates the endocrine hypothalamus with other circumventricular organs which may also be sites of neuroendocrine transduction.

Animals↗

PubMed1992

Localization of xenopsin and xenopsin precursor fragment immunoreactivities in the skin and gastrointestinal tract of Xenopus laevis.

Xenopsin (Xp) and xenopsin precursor fragment (XPF) are bioactive peptides derived from a single precursor molecule; both were isolated previously from extracts of Xenopus laevis skin. The present immunohistochemical study was undertaken to determine the specific cellular localization of these two peptides in the skin and also in the gastrointestinal tract of adult Xenopus. We report here that Xp-like and XPF-like immunoreactivities co-exist in the granular glands of the skin and specific granular cells in the lower esophagus and stomach. However, only Xp-like immunoreactivity, not XPF-like immunoreactivity, was detected in tall, thin cells of the duodenum and in club-shaped cells of the large intestine. The immunochemical co-localization of the two peptides in specific cells of the skin, lower esophagus and stomach suggests that the same gene is expressed in each of these cells, and that the precursor molecule undergoes similar post-translational processing. In contrast, the observation that certain cells of the duodenum and large intestine display only one peptide immunoreactivity suggests an alternative phenomenon, possibly involving selective peptide accumulation or expression of a different gene.

Amino Acid Sequence↗

PubMed1995

Binding between lipopolysaccharide and cecropin A.

Cecropin A (CA), a bioactive peptide, produced significant lethality to Pantoea agglomerans (PA) at low concentrations. Significant mortality occurred immediately after addition of CA. Separate preincubations of lipopolysaccharides (LPS) from the following bacteria: PA, Serratia marcescens, Escherichia coli (EC), and Salmonella typhimurium with CA were performed prior to the bioassay. CA was also preincubated with diphosphoryl lipid A (DPL-A) from EC and S. minnesota (SM), trilinolein, palmitic, lauric and myristic acids (fatty acids contained in the lipid A of PA-LPS) and bovine brain gangliosides. Spectral analysis to determine the interaction between glycosphingolipids (sphingomyelin, bovine brain gangliosides, and galactocerebrosides) and CA were performed. Results showed that all types of LPS and DPL-A as well as gangliosides studied blocked CA lethality to PA. The level of inhibition of CA antibacterial properties was dependent on LPS and DPL-A concentration. The individual fatty acids and trilinolein did not affect CA lethality to PA. Spectral studies showed complexation between CA and PA-LPS, both types of DPL-A, and the glycosphingolipids. Biological and chemical analyses confirm that CA binds to the diphosphoryl lipid A moiety of LPS.

Animals↗

PubMed1991

Islet amyloid polypeptide in insulinoma and in the islets of the pancreas of non-diabetic and diabetic subjects.

Amyloid deposition is a common pathological feature in insulinoma and in the islets of the pancreas in type-2 diabetic patients. The present immunohistochemical study revealed that normal B-cells, insulinoma, and amyloid deposits in insulinoma and diabetic pancreatic islets were commonly immunoreactive with antiserum to C-terminal synthetic tetradecapeptide of human islet amyloid polypeptide (IAPP) (24-37). Amyloid fibrils in insulinoma were also positive to IAPP by immunoelectron microscopy. A high level of IAPP was detected in the plasma and tissue of a insulinoma patient by radioimmunoassay suggesting that amyloid deposition in insulinoma is due to overproduction of IAPP. Amyloid deposits immunoreactive to IAPP were also seen in all diabetic pancreatic islets, but in no non-diabetic islets. There was much amyloid deposition in the islets of severe diabetics, whose B-cells demonstrated decreased immunoreactivities for IAPP and insulin. The IAPP content of the pancreas was 649.0 and 847.7 pg/mg wet weight in each of two diabetic patients, and 1034.6 and 1447.7 pg/mg wet weight in two non-diabetic patients. The present study revealed that IAPP is a bioactive peptide secreted from islet B-cells and are amyloidogenic peptide concerned in diabetogenensis and/or the progression of type-2 diabetes mellitus.

Adult↗

PubMedDate not supplied

Age-related changes in adenohypophyses of mice with the hereditary obese hyperglycemic syndrome (ob/ob) in relation to the diabetic state of the animals.

Mice with hereditary, monogenic obese-hyperglycemic syndrome (ob/ob) were shown to have smaller adenohypophyses in comparison to their normal littermates from an age of 4 weeks onward. The size of the pars intermedia of obese mice was not, however, significantly different from that of normal littermates. Morphometric criteria strongly suggest hyperactivity of the cells of the pars intermedia of obese hyperglycemic mice. The enhanced secretion of bioactive peptides of the pars intermedia may contribute to the diabetic aspects of the obese-hyperglycemic syndrome. The hyperactivity of the pars intermedia is likely to be allophenic.

Aging↗

PubMed1990

Application of immobilized growing cells.

Immobilized living and growing cells are attracting worldwide attention because these biocatalysts have self-proliferating and self-regenerating properties of catalytic systems and are able to catalyze efficiently multifunctional and multistep reactions involving coenzyme regeneration. This article summarizes the application of microbial, plant, and mammalian cells, genetically improved or not, immobilized by different methods to the production of amino acids, organic acids, antibiotics, steroids, medicines, enzymes, bioactive peptides, etc., emphasizing the recent results. Effects of the gel properties on the efficient performance of bioprocesses are also discussed.

Amino Acid Sequence↗

PubMed2001

Melanocortin receptors: their functions and regulation by physiological agonists and antagonists.

The melanocortins are a family of bioactive peptides derived from proopiomelanocortin, and share significant structural similarity. Those peptides are best known for their stimulatory effects on pigmentation and steroidogenesis. Melanocortins are synthesized in various sites in the central nervous system and in peripheral tissues, and participate in regulating multiple physiological functions. Research during the past decade has provided evidence that melanocortins elicit their diverse biological effects by binding to a distinct family of G protein-coupled receptors with seven transmembrane domains. To date, five melanocortin receptor genes have been cloned and characterized. Those receptors differ in their tissue distribution and in their ability to recognize the various melanocortins and the physiological antagonists, agouti signaling protein and agouti-related protein. These advances have opened new horizons for exploring the significance of melanocortins, their antagonists, and their receptors in a variety of important physiological functions.

Animals↗

PubMed2005

Conotoxins and the posttranslational modification of secreted gene products.

The venoms of predatory cone snails (genus Conus) have yielded a complex library of about 50-100,000 bioactive peptides, each believed to have a specific physiological target (although peptides from different species may overlap in their target specificity). Conus has evolved the equivalent of a drug development strategy that combines the accelerated evolution of toxin sequences with an unprecedented degree of posttranslational modification. Some Conus venom peptide families are the most highly posttranslationally modified classes of gene products known. We review the variety and complexity of posttranslational modifications documented in Conus peptides so far, and explore the potential of Conus venom peptides as a model system for a more general understanding of which secreted gene products may have modified amino acids. Although the database of modified conotoxins is growing rapidly, there are far more questions raised than answers provided about possible mechanisms and functions of posttranslational modifications in Conus.

Amino Acid Sequence↗