Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMPs mode of action”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2002

Molecular diversity in gene-encoded, cationic antimicrobial polypeptides.

Gene-encoded, ribosomally synthesised antimicrobial peptides (AMPs) are an ancient and pervasive component of the innate defence mechanisms used by multicellular organisms to control the natural flora and combat pathogens. Bacteria also produce such AMPs to maintain ecological niches free of rival strains. Several hundred different peptides have been characterised to date, and they show a marked degree of variability in both sequence and structure, having evolved to act against distinct microbial targets in different physiological contexts. Many of these peptides appear to function via a selective, but not receptor-mediated, permeabilisation of microbial membranes, while others interact with specific membrane associated or intracellular targets. This review presents a broad survey of different amp structural classes, emphasising both their molecular diversity and underlying similarities. The mode of action of these peptides and potential for biomedical and other application is also briefly discussed.

Amino Acid Sequence↗
PubMedDate not supplied

The mode of direct action of dopamine on the rabbit heart.

The effects of dopamine on the force of contraction and on cylic adenosine monophosphate (AMP) levels were investigated in isolated electrically driven left atria (32 degrees C, 1 Hz) and papillary muscles (37 degrees C, 0.5 Hz) of the rabbit. In both preparations only the combined application of phentolamine (10(-6) M) and pindolol (3 X 10(-8) M) shifted the entire dose-response curves for the positive inotropic effect of dopamine to the right, while either antagonist used separately had no effect. Similar results were obtained when the indirect action of dopamine via the release of endogenous noradrenaline was inhibited by cocaine (3 X 10(-5) M) or by pretreatment of the rabbits with reserpine (6 mg/kg, s.c., 16 hr). Increases in cyclic AMP induced by dopamine (10(-4) M in atria and 3 X 10(-4) M in papillary muscles) were prevented by cocaine or by pretreatment with reserpine, indicating that these increases are mainly evoked by released endogenous noradrenaline. It is concluded that both alpha- and beta- adrenoceptors may play roles in the direct positive inotropic action of dopamine in the rabbit heart. The failure of the direct action of dopamine to increase cyclic AMP may be due to a cyclic-AMP-decreasing effect of alpha-adrenoceptor stimulation, which may counteract cyclic AMP increases induced by dopamine via beta-adrenoceptor stimulation.

Animals↗
PubMed2005

Insect antimicrobial peptides: structures, properties and gene regulation.

Antimicrobial peptides (AMPs) are part of the armament that insects have developed to fight off pathogens. Insect AMPs are typically cationic and often made of less than 100 amino acid residues. Although their structures are diverse, most of the AMPs can be assigned to a limited number of families. The most common structures are represented by peptides assuming a alpha-helical conformation in organic solutions or disulfide-stabilized beta-sheets with or without alpha-helical domains present. The diverse activity spectrum of these peptides may indicate different modes of action. Genetic analysis in the Drosophila model evidenced that multiple signal transduction pathways are activating the genes coding AMPs.

Amino Acid Sequence↗
PubMed1973

Bicyclic phosphorus esters: high toxicity without cholinesterase inhibition.

4-Isopropyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxide has a mouse intraperitoneal lethal dose, 50 percent effective, of 0.18 milligram per kilogram of body weight. Related compounds used by many chemical researchers are also highly toxic. Brain acetylcholinesterase inhibition is not involved in their mode of action. The structural similarity of these compounds to adenosine 3',5'-monophosphate (cyclic AMP) is of interest.

Animals↗
PubMed1975

Limited hydrolysis of tRNA by phosphodiesterase.

Digestion of tRNA by electrophoretically pure phosphodiesterase is limited to a short sequence of nucleotides at the 3'-terminus. On the average, four percent of all nucleotides can be released from tRNA. The optimum Mg2 concentration is 10mM and the optimum pH 9.2. The mode of action is a random attack by the enzyme on the substrate. The terminal AMP is completely removed at 15 degrees C after short incubation; about 400 mol of AMP were removed per min by 1 mol of enzyme. The following CMP residues are released much more slowly; at 15 degrees C incompletely, and at 37 degrees C more or less completely in 1 h. In about 50% of the tRNA molecules, the fourth nucleotide could be removed in very long incubations or with very high enzyme concentrations.

Adenosine Monophosphate↗
PubMed2005

Antimicrobial peptides: new candidates in the fight against bacterial infections.

Antimicrobial peptides (AMPs) of innate origin are agents of the most ancient form of defense systems. They can be found in a wide variety of species ranging from bacteria through insects to humans. Through the course of evolution, host organisms developed arsenals of AMPs that protect them against a large variety of invading pathogens including both Gram-negative and Gram-positive bacteria. At a time of increasing bacterial resistance, AMPs have been the focus of investigation in a number of laboratories worldwide. Although recent studies show that some of the peptides are likely to have intracellular targets, the vast majority of AMPs appear to act by permeabilization of the bacterial cell membrane. Their activity and selectivity are governed by the physicochemical parameters of the peptide chains as well as the properties of the membrane system itself. In this review, we will summarize some of the recent developments that provide us with a better understanding of the mode of action of this unique family of antibacterial agents. Particular attention will be given to the determinants of AMP-lipid bilayer interactions as well as to the different pore formation mechanisms. The emphasis will be on linear AMPs but representatives of cysteine-bridged AMPs will also be discussed.

Amino Acid Sequence↗
PubMed1978

Inhibition of noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes by purified phospholipase C and theta-toxin from Clostridium perfringens.

Purified phospholipae C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) and theta-toxin from Clostridium perfringens both inhibited noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes in a dose-dependent manner. The action of phospholipase C was gradual in onset, while the effect of theta-toxin was almost immediate. Phospholipase C, but not theta-toxin, hydrolyzed membrane phospholipids and inhibited adenylate cyclase (EC 4.6.1.1) in a crude membrane fraction from fat cells. The inhibitory effects of phospholipase C were associated with morphological alterations detectable by electron microscopy, whereas effects of theta-toxin were observed at a time when no clearcut morphological alterations could be observed. It is concluded that the two purified principles from C. perfringens, which are both present in commercial preparations of phospholipase C, antagonize noradrenaline-stimulated cyclic AMP accumulation and lipolysis. Although their exact mechanisms of action have not been elucidated, phospholipase C and theta-toxin have different modes of attack.

Adenylyl Cyclases↗
PubMed1980

Yeast mating pheromone alpha factor inhibits adenylate cyclase.

The pheromone alpha factor, secreted by Saccharomyces cerevisiae cells of the alpha mating type, serves to synchronize the opposite mating type (a cells) at G1 as a prelude to fusion of the two cell types. We found that, in vitro, alpha factor inhibited the membrane-bound adenylate cyclase of these cells in a dose-dependent manner. Moreover, one class (ste5) of a cell mutants that grow normally at either 23 degrees or 34 degrees C but that are unable to respond to alpha factor or to mate at the higher temperature possessed an adenylate cyclase activity that was not inhibited by alpha factor at 34 degrees C but was fully sensitive to inhibition at 23 degrees C. Furthermore, addition of cyclic AMP to a cell culture medium shortened the period of pheromone-induced G1 arrest. We conclude that inhibition of adenylate cyclase activity by alpha factor may constitute, at least in part, the biochemical mode of action of the pheromone in vivo.

Adenylyl Cyclase Inhibitors↗
PubMed1980

Inhibition of histamine release induced by compound 48/80 and peptide 401 in the presence and absence of calcium. Implications for the mode of action of anti-allergic compounds.

Histamine may be released from rat peritoneal mast cells by compound 48/80 and peptide 401 in the presence and absence of extracellular calcium. The process is non-cytolytic and requires an intact cell metabolism. The release produced under both conditions is inhibited by disodium cromoglycate, theophylline, dibutyryl cyclic AMP and (at high concentrations) quercetin. The efficacy of the drugs in the absence of extracellular calcium cannot be explained in terms of their postulated effect on the calcium-gating mechanism operative in anaphylactic secretion. Alternative modes of action of the compounds are thus considered.

Animals↗
PubMed1979

Inhibition of fundic strips from guinea-pig stomach: the effect of theophylline on the membrane potential, muscle contraction and ion fluxes.

The effect of theophylline on the smooth muscle cells of the fundic part of the stomach of the guinea pig was investigated. Theophylline hyperpolarized the membrane, inhibited spike discharges and slow waves and produced relaxation of the muscle cells. Furthermore, the theophylline-induced relaxation was not affected in low sodium solution or during inhibition of the sodium pump. Partial inhibition of the theophylline relaxation was seen in muscle depolarized by a high potassium solution and also when ATP was the relaxant. The potassium efflux was enhanced by ATP, but was not markedly changed by theophylline. A change in calcium efflux in the presence of theophylline could not be measured in quiescent preparations. The calcium influx was not changed by theophylline in Krebs, by low Ca, or by high K solution. Furthermore, the tissue content of cyclic AMP was increased by 59.6% in the presence of theophylline (2 x 10(-3) M). The conclusion is reached that the most likely mode of action of theophylline is a suppression of spontaneous activity and an extensive calcium binding to internal sites.

Animals↗
PubMed1990

Inhibitory effects of loading with the calcium-chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) on amylase release and cellular ATP level in rat parotid cells.

Rat parotid cells were loaded with the Ca2(+)-chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), by incubation with the acetoxymethyl ester of BAPTA (BAPTA-AM). The BAPTA loading inhibited amylase release induced by beta-adrenergic receptor stimulation without affecting the basal release, and the IC50 value was 25 microM. Incubation of cells with BAPTA-AM also suppressed cellular ATP levels considerably. At 100 microM BAPTA-AM, the ATP level fell to about 50% of the control. A decrease in ATP levels by incubation with oligomycin, a mitochondrial inhibitor, correlated well with the inhibition of amylase release. Although these results do not exclude the possibility that cytosolic free Ca2+ is involved in the regulation of cyclic AMP-mediated amylase release, they suggest that the amylase release inhibition with BAPTA loading may be due, in part, to a decrease in cellular ATP levels. Therefore, the exact mode of the BAPTA action must be interpreted with caution.

Adenosine Triphosphate↗
PubMed1993

On the mechanism of action of sodium orthovanadate in inducing histamine release from rat peritoneal mast cells.

Sodium orthovanadate produced a dose-dependent release of histamine and prostaglandin D2 from rat peritoneal mast cells. The release of histamine was selectively inhibited by the anion channel blockers SITS and DIDS, and by theophylline and dibutyryl cyclic-AMP, but was unaffected by disodium cromoglycate and lanthanum ions. Unlike IgE-directed ligands, vanadate did not produce any change in the intracellular concentration of cyclic-AMP but did promote a substantial uptake of calcium-45 from the incubation medium. This effect paralleled the release of histamine. These results are discussed in terms of the possible mode of action of vanadate.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Galaninergic signalling and adenylate cyclase.

Galanin is a hyperpolarizing, inhibitory neurotransmitter; its recognition by seven transmembrane spanning G-protein-coupled receptors leads to a change in accumulation of cAMP (3'5'-cyclic AMP). Different subtypes of galanin receptor and G-proteins could be manifested in the mode of inhibitory action of galanin receptor on the production of cAMP by adenylate cyclase. Galanin analogues, acting at the adenylate cyclase level as subtype-specific galanin antagonists, can selectively block the inhibitory effect of endogenous galanin and thereby have potential as therapeutic agents for several endocrine, neuroendocrine and neuronal disorders. In this review, the latest results in the field of interplay between galanin-initiated signal transduction and the cAMP pathway are summarized.

Adenylyl Cyclases↗