Inhibition by sulfhydryl agents of arachidonic acid-induced platelet aggregation and release of potential inflammatory substances

Sulfhydryl agents (mercaptoethanol, thioglycerol, dithiotreitol, and sodium diethyldithiocarbamate) prevented aggregation of rabbit platelets and the accompanying generation of pharmacologically active substances due to arachidonic acid. Inhibition was also found after administration of the antagonists. This antagonism was suppressed if the inhibitors were removed from the platelet suspension by washing procedures, whereas inhibition by indomethacin was irreversible. Amino-thiol reagents either failed to antagonize the effects of AA or potentiated them. CuCl₂ increased the amounts of pharmacologically active substances generated in incubates of intact platelets with arachidonic acid, and reversed the inhibition due to thiol agents, but did not interfere with inhibition by indomethacin. Platelets suspended in Tyrode solution generated unstable pharmacologically active substances upon incubation with arachidonic acid ; stability of these substances could be maintained at 4°C. Generation of this temperature — sensitive material was inhibited by indomethacin and by thiol agents. Interference with a copper-containing component of PG synthetase or reduction of an intermediate lipoperoxide appear as two possible mechanisms of action of thiol agents.     

Enhancing effect of a protein from <Emphasis Type="Italic">Lonomia obliqua</Emphasis> hemolymph on recombinant protein production

Gene expression in animal cells allows large scale production of proteins used for either structure and function studies or therapeutic purposes. Maximizing recombinant protein production is necessary to optimize cell growth and protein expression. Some studies have demonstrated the presence of pharmacologically active substances in insect hemolymph. In this work, we have identified and purified a protein from Lonomia obliqua hemolymph able to increase the production of the rabies virus glycoprotein, expressed in Drosophila melanogaster S2 cells, by about 59%.     

Penetration rates of osmium tetroxide with different fixation vehicles

Summary The presence of any substance other than OsO₄ in osmium tetroxide fixation mixtures causes a decrease in the penetration rate of the fixative. Fixation times should therefore be prolonged whenever a fixation mixture containing osmotically active substances is used.With I Figure in the Text     

Pancreatic islet cell tumors metastatic to the liver: treatment by hepatic artery chemo-embolization

The embolization of hepatic metastases of pancreatic islet cell tumors achieves a tumor necrosis without liver failure owing to double hepatic blood supply. The arterial chemotherapy performed at the same time delivers a large amount of cytotoxic agent directly into the tumor. Tumor bulk reducing and decreasing of production of pharmacologically active substances may be obtained to some degree. Although an objective documentation of the therapeutic effect is difficult to obtain, several series emphasize that the embolization provides a partial and transient palliative remission. Therefore, the chemo-embolization should be included in a multidisciplinary approach of metastatic endocrine malignancies in combination with surgical resection, systemic antineoplastic chemotherapy, and antihormonal therapy.     

A receptor model for binary mixtures applied to the sweetness of fructose and glucose: De Graaf and Frijters revisited

Assuming that two substances (e.g. tastants or odorants) sharea common type of receptor, a binary mixture model is derivedfrom the equations for the equilibrium constants for the separateand combined reactions of the substances and the hypothesizedreceptor(s). It is assumed that a multimolecular interactionbetween stimulant molecules and a receptor or between a stimulantmolecule and several receptors may occur forming a stimulant–receptorcomplex. This model provides a significantly superior fit tothe sweetness data of De Graaf and Frijters (1986) on mixturesof fructose and glucose than an alternative model based on Beidler's(1962) theory of taste stimulation applied to mixtures. (InBeidler's model a unimolecular interaction is assumed betweena stimulant molecule and a receptor.) Estimates of the parametersof the model provide information on the relative stoichiometriccoefficients of the reactants and the relative equilibrium constantsfor the reactions between the receptor and the substances alone.The derived model should have a broad domain of applicationin studying the interaction between ligands and receptors, andis not limited to applications in the chemical senses or topsychophysical experiments in particular.     

An Equiratio Mixture Model for Non-additive Components: A Case Study for Aspartame/Acesulfame-K Mixtures

The Equiratio Mixture Model predicts the psychophysical functionfor an equiratio mixture type on the basis of the psychophysicalfunctions for the unmixed components. The model reliably estimatesthe sweetness of mixtures of sugars and sugar-alchohols, butis unable to predict intensity for aspartame/sucrose mixtures.In this paper, the sweetness of aspartame/acesulfame-K mixturesin aqueous and acidic solutions is investigated. These two intensivesweeteners probably do not comply with the model's originalassumption of sensory dependency among components. However,they reveal how the Equiratio Mixture Model could be modifiedto describe and predict mixture functions for non-additive substances. To predict equiratio functions for all similar tasting substances,a new Equiratio Mixture Model should yield accurate predictionsfor components eliciting similar intensities at widely differingconcentration levels, and for substances exhibiting hypo- orhyperadditivity. In addition, it should be able to correct violationsof Stevens's power law. These three problems are resolved ina model that uses equi-intense units as the measure of physicalconcentration. An interaction index in the formula for the constantaccounts for the degree of interaction between mixture components.Deviations from the power law are corrected by a nonlinear responseoutput transformation, assuming a two-stage model of psychophysicaljudgment. Chem. Senses 21: 1–11, 1996.     

Compounds of Mo, V and W in biochemistry and their biomedical activity.

Molybdenum, vanadium and tungsten compounds are widely applied as analytical reagents for determination of numerous pharmacologically active substances and different biochemical parameters. Recent data from the available literature pointed to a very potent biomedical activity of compounds containing these trace elements. The present paper represents a survey on the structure and chemical properties of these compounds, as well as on their biological activity, mostly based on their interaction with cations of biomolecules, such as phospholipids and proteins. Besides, their potent inhibitory effects on cellular targets, bacterial and viral DNA and RNA polymerases will be discussed, as well. Numerous authors clearly demonstrated the antiviral (especially anti-HIV), anticoagulant and antineoplastic properties of the compounds containing the above trace elements. It has been also shown that these compounds act on some cellular enzymatic systems leading to the normalisation of blood pressure, blood glucose and serum lipid levels. Also, compounds of these trace elements represent potent antiobesity agents and express hepatoprotective and antioxidative stress activity.     

Kinase-independent phosphoramidate S1P1 receptor agonist benzyl ether derivatives

Previously published S1P receptor modulator benzyl ether derivatives have shown potential as being viable therapeutics for the treatment of neurodegenerative diseases, however, two of the most S1P₁-selective compounds are reported as being poorly phosphorylated by kinases in vivo. Phosphoramidates of BED compounds (2a, 2b) were synthesised with the aim of producing kinase-independent S1P receptor modulators. Carboxypeptidase, human serum and cell lysate processing experiments were conducted. ProTide BED analogues were found to have an acceptable level of stability in acidic and basic conditions and in vitro metabolic processing experiments showed that they are processed to the desired pharmacologically active monophosphate. The research describes the development of an entirely novel family of therapeutic agents.     

Antimicrobial proline-rich peptides from the hemolymph of marine snail Rapana venosa

Hemolymph of Rapana venosa snails is a complex mixture of biochemically and pharmacologically active components such as peptides and proteins. Antimicrobial peptides are gaining attention as antimicrobial alternatives to chemical food preservatives and commonly used antibiotics. Therefore, for the first time we have explored the isolation, identification and characterisation of 11 novel antimicrobial peptides produced by the hemolymph of molluscs. The isolated peptides from the hemolymph applying ultrafiltration and reverse-phase high-performance liquid chromatography (RP-HPLC) have molecular weights between 3000 and 9500 Da, determined by mass spectrometric analysis. The N-terminal sequences of the peptides identified by Edman degradation matched no peptides in the MASCOT search database, indicating novel proline-rich peptides. UV spectra revealed that these substances possessed the characteristics of protein peptides with acidic isoelectric points. However, no Cotton effects were observed between 190 and 280 nm by circular dichroism spectroscopy. Four of the Pro-rich peptides also showed strong antimicrobial activities against tested microorganisms including Gram-positive and Gram-negative bacteria.     

Interaction of human 3-phosphoglycerate kinase with L-ADP, the mirror image of D-ADP

l-Nucleoside-analogues, mirror images of the natural d-nucleosides, are a new class of antiviral and anticancer agents. In the cell they have to be phosphorylated to pharmacologically active triphosphate forms, the last step seems to involve human 3-phosphoglycerate kinase (hPGK). Here we present a steady state kinetic and biophysical study of the interaction of the model compound l-MgADP with hPGK. l-MgADP is a good substrate with k_cat and K_m values of 685 s⁻¹ and 0.27 mM, respectively. Double inhibition studies suggest that l-MgADP binds to the specific adenosine-binding site and protects the conformation of hPGK molecule against heat denaturation, as detected by microcalorimetry. Structural details of the interaction in the enzyme active site are different for the d- and l-enantiomers (e.g. the effect of Mg²⁺), but these differences do not prevent the occurrence of the catalytic cycle, which is accompanied by the hinge-bending domain closure, as indicated by SAXS measurements.     

Biosensor analysis of the interaction of potential dimerization inhibitors with HIV-1 protease

Inhibitors of protein-protein interactions are currently considered as perspective prototypes of a new generation of drugs. The most attractive targets for such inhibitors are the oligomeric enzymes which active sites are formed by amino acid residues from different subunits. HIV-1 protease (HIVp), which is active only as a homodimer form, is the classic example of such enzymes. We have developed a new approach for experimental screening of HIVp dimerization inhibitors. It is based on an original biosensor test-system for differential analysis of interaction of tested substances with HIVp dimers and monomers. Using this test-system we have analyzed the most perspective candidate substances predicted by the method of virtual screening, and also some derivatives of glycyrrhizin, triterpenic and steroid glycosides. In the results of this study we have found one compound, which preferentially interacts with HIVp monomers and inhibits in vitro activity of this enzyme with the IC₅₀ value of about 10^?6 M.     

A search for an 'ouabain-like' substance from the electric organ of Electrophorus electricus which led to arachidonic acid and related fatty acids

The electric organ of Electrophorus electricus contains substances which inhibit (Na+ + K+)-ATPase activity, the specific binding of [3H]ouabain to purified (Na+ + K+)-ATPase and 86Rb+ uptake by chick cardiac cells in culture. The active organic material was extracted from microsomal membranes. Its purification was carried out by chromatography on Sep-Pak C-18 and thin-layer chromatography. Reverse-phase liquid chromatography and mass spectrometry identified the active material as a mixture of unsaturated fatty acids. Linoleic (18:2), arachidonic (20:4), linolenic (18:3) and docosahexaenoic acids (22:6) contributed to about 60% of the total activity of the active material. The other active substances could be arachidonic analogs, since they have both a lipophilic and carboxylic character. Pure unsaturated fatty acids have been shown to be active in the different biological assays used to analyze the endogenous 'ouabain-like' activity. Linolenic, arachidonic and docosahexaenoic acids were the most active, whereas saturated fatty acids and glyceryl esters or methyl esters of unsaturated fatty acids were inactive. It is possible that in pathological situations in which the level of unsaturated fatty acids increases, these molecules may then act as physiological inhibitors of the sodium pump.     

Prostaglandin Production by Experimental Tumours and Effects of Anti-inflammatory Compounds

THE presence of small quantities of prostaglandin-like material has been demonstrated in medullary carcinoma of the thyroid¹ and in Kaposi's sarcoma²; the diarrhoea often associated with these tumours has been attributed to prostaglandins. Diarrhoea is also often present in mice bearing the BP8/P₁ tumour. Preliminary investigations of the ascitic fluid from mice inoculated with this tumour showed the presence of pharmacologically active substances and prostaglandin E₂-like activity was found in small amounts³. Subsequent examination of the BP8/P₁ cells has revealed concentrations of prostaglandin E₂ in excess of 100 times that of the fluid. Significant amounts have also been found in another tumour, sarcoma 180 (S180).     

A review of the herbal phosphodiesterase inhibitors; Future perspective of new drugs

Phosphodiesterase inhibitors (PDEIs) are a class of drugs that are widely used because of their various pharmacological properties including cardiotonic, vasodilator, smooth muscle relaxant, antidepressant, antithrombotic, bronchodilator, antiinflammatory and enhancer of cognitive function. In the recent years, interest in drugs of plant origin has been progressively increased. Some pharmacologically active substances that come from plants demonstrate PDEI activity. They mainly belong to alkaloids, flavonoids, and saponins. In this review, studies on herbal PDEI were reviewed and their possible therapeutic applications were discussed. Screening plants for PDE inhibitory activity may help to develop standardized phytotherapeutic products or find new sources for new lead structures with PDEI pharmacological activity. The studies discussed in this paper are mainly in vitro and for more reasonable and conclusive results, it is required to conduct in vivo and finally human and clinical tests.     

Non-invasive technique for examining the respiratory proprioceptor system in man

Our technique enables non-invasive experiments to be conducted on the proprioceptor part of respiratory control, while eliminating misleading responses due to interaction with the chemoreceptor system; interaction was prevented by stabilizing arterial P_O2 and P_CO2 with the aid of an optimal regulator based on a mini-computer which controlled the inspired gas mixture. The proprioceptor system in a human was disturbed by applying positive pressure pulses at the mouth, responses were derived from continuous air-flow measurement. The classical inflation inhibiting reflex and an effect akin to Head's paradoxical reflex were demonstrated.     

9-aminoacridine inhibits the B-Z transition of poly(dA-dT).

9-Aminoacridine is the parent compound of a family of pharmacologically active model substances that bind to DNA through intercalation between base pairs. In the present study we show that 9-aminoacridine inhibits the B-to-Z isomerization of poly(dA-dT) in conditions that otherwise cause it to occur (5 M NaCl and 123 mM Ni(ClO4)2). Higher concentrations of Ni(ClO4)2 (155 mM) are able to induce the Z-form due to the disruption of the drug-polynucleotide interaction by the metal ion. Additionally, the dye reverses the Z-form in certain conditions. Thus, the data from this study indicate that 9-aminoacridine binds preferentially to the B-form of poly(dA-dT).     

NMR observation of the interaction of small oligopeptides with phospholipid vesicles

Using proton spin-lattice relaxation times, the interaction of small oligopeptides with sonicated vesicles of synthetic β-γ-dimyristoyl L-α-lecithin has been monitored at 29°C in D₂O. The measured relaxation times for the lecithin choline methyl, alkyl chain, and terminal methyl protons were observed to shorten markedly with increasing concentration of peptide, the relaxation remaining exponential. Noticeable resonance broadening was observed at the highest peptide concentration studied. The data reported are for the effect of the pharmacologically active pentapeptide methionine-enkephalin. Similar results have been observed for the effect of tetraglycine. The relaxation of the observable resonances of the added peptide appear to be unaffected. The results are discussed in terms of peptide-vesicle interactions.     

Interaction of chromatin with NaCl and MgCl2: Solubility and binding studies,transition to and characterization of the higher-order structure

Chicken erythrocyte chromatin containing histones H1 and H5 was carefully separated into a number of well-characterized fractions. A distinction could be made between chromatin insoluble in NaCl above about 80 mm, and chromatin soluble at all NaCl concentrations. Both chromatin forms were indistinguishable electrophoretically and both underwent the transition from the low salt “10 nm” coil to the “30 nm” higher-order structure solenoid by either raising the MgCl₂ concentration to about 0.3 mm or the NaCl concentration to about 75 mm. The transitions were examined in detail by elastic light-scattering procedures. It could be shown that the 10 nm form is a flexible coil. For the 30 nm solenoid, the assumption of a rigid cylindrical structure was in good agreement with 5.7 nucleosomes per helical turn. However, disagreement of calculated frictional parameters with values derived from quasielastic light-scattering and sedimentation introduced the possibility that the higher-order structure, under these conditions, is more extended, flexible, or perhaps a mixture of structures. Values for density and refractive index increments of chromatin are also given.To understand the interaction of chromatin with NaCl and with MgCl₂, a number of experiments were undertaken to study solubility, precipitation, conformational transitions and binding of ions over a wide range of experimental conditions, including chromatin concentration.     

Simulation of the ignition of a methane-air mixture by a high-voltage nanosecond discharge

The ignition dynamics of a CH₄: O₂: N₂: Ar = 1: 4: 15: 80 mixture by a high-voltage nanosecond discharge is simulated numerically with allowance for experimental data on the dynamics of the discharge current and discharge electric field. The calculated induction time agrees well with experimental data. It is shown that active particles produced in the discharge at a relatively low deposited energy can reduce the induction time by two orders of magnitude. Comparison of simulation results for mixtures with and without nitrogen shows that addition of nitrogen to the mixture leads to a decrease in the average electron energy in the discharge and gives rise to new mechanisms for accumulation of oxygen atoms due to the excitation of nitrogen electronic states and their subsequent quenching in collisions with oxygen molecules. Acceleration of the discharge-initiated ignition is caused by a faster initiation of chain reactions due to the production of active particles, first of all oxygen atoms, in the discharge.