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PubMed2004

[Effect of pharmaceutical aids on physico-chemical indicators in solutions of substance XXII B].

Within a study of optimization of auxiliary substances in the formulation of a hydrogel containing a potential local anaesthetic agent, substance XXII B, the paper evaluated the effect of a preservative (Ajatin) and humectants (glycerol, propylene glycol, sorbitol) on selected physicochemical indices, which included the partition coefficient, surface tension, and viscosity of the solutions of potential drug XXII B. On the basis of the statistical evaluation of the results, the optimal combination of auxiliary substances in this case seems to be Ajatin + glycerol.

Anesthetics, Local↗
PubMed1990

Molecular effects of dimethylanatoxin on the peripheral nicotinic acetylcholine receptor.

N,N-dimethylanatoxin (DMAnTX), the quaternary derivative of the potent nicotinic agonist (+)-anatoxin-a (AnTX), has been evaluated for potency and efficacy at nicotinic acetylcholine receptors of frog motor endplates and Torpedo electric organs. DMAnTX was only weakly effective in eliciting contracture of the frog rectus abdominis and was orders of magnitude less potent than AnTX. Biochemical assay showed that DMAnTX was a weak inhibitor of [125I]alpha-bungarotoxin binding to the receptors in frog muscle and Torpedo electroplaque membranes: the IC50 values were 60 and 14 microM, respectively. A low frequency of single channel currents recorded from isolated interosseal fibers at concentrations from 20 to 100 microM of DMAnTX and the stimulation of [3H]perhydrohistrionicotoxin [( 3H]H12-HTX) binding (half-maximal at 0.3 microM) confirmed the weak activation of the receptor. DMAnTX also exhibited antagonist effects. In muscle twitch assays, 100 microM of DMAnTX effectively decreased the tension induced by nerve stimulation, although DMAnTX did not affect muscle membrane action potentials. The binding of [3H] perhydrohistrionicotoxin was also inhibited at high micromolar concentrations of DMAnTX. Combination of DMAnTX with acetylcholine in single channel current experiments demonstrated that DMAnTX possesses ion channel blocking properties, which become apparent at low micromolar concentrations, and DMAnTX enhances the desensitization induced by acetylcholine above 10 microM AnTX. The difference in agonist potency between AnTX and DMAnTX may be attributed to a change in conformation of the molecular skeleton induced by the N-methyl groups.

Acetylcholine↗
PubMedDate not supplied

Macrophage stimulation activity of antimicrobial N,N-dimethylaminoethyl paramylon.

Pretreatment with N,N-dimethylaminoethyl (DMAE) paramylon significantly protected mice from infection by various microorganisms. When mouse peritoneal macrophages were cultured with DMAE-paramylon, they showed morphological change (spreading) and elevated NBT-reducing activity. Macrophages prepared from DMAE-paramylon-treated mice had higher NBT-reducing activity than those from control mice. On the other hand, carboxymethyl paramylon and paramylon sulfate, which did not induce appreciable antimicrobial activity, failed to stimulate macrophage functions. The data suggest a significant role of macrophages in antimicrobial activity induction by cationized glucans.

Animals↗
PubMed1991

Pharmacological and microbiological evaluations of potential new long-acting local anaesthetics.

The results of the preliminary pharmacological and microbiological evaluations of certain new derivatives of dialkylaminoethyl-phenyl-ether hydrochloride, as potential long-acting local anaesthetics, are reported. The guinea pig intradermal wheal test was used for determining the activity and duration of local anaesthesia (WT). These were assayed at concentrations of 0.5% w/v. Lidocaine hydrochloride, 1.0% w/v, was employed as the standard and normal saline, 0.9% w/v, as the control. The compounds showed outstanding activity profiles and duration of action with no apparent signs of both local and systemic side effects. In addition, the results of inhibition of the ciliated protozoan Tetrahymena pyriformis mobility by the aforementioned compounds are presented. A general relationship between the minimum inhibitory concentration (MIC) of these compounds to inhibit mobility of the whole T. pyriformis cells and the duration of anaesthesia was observed. Moreover, derivatives with tertiary or secondary butyl substituents in the benzene ring, irrespective of position or number, were superior to others and showed prolonged duration of anaesthesia and lower MIC. The dependence of both WT and MIC on partition coefficient (log P) of these compounds indicates that in both biological systems the anaesthetics interact strongly with hydrophobic structures of the T. pyriformis cells membrane resulting in fluidisation and loss of ciliary function.

Anesthetics, Local↗
PubMed1991

Subcellular fractions of rat organs contain nitroreductases which reduce N-nitrodimethylamine to N-nitrosodimethylamine.

The nasal carcinogen N-nitrodimethylamine was reduced to its N-nitroso analogue N-nitrosodimethylamine in vivo. Liver-soluble fraction and brain mitochondria contained enzymes capable of reducing this compound. The activity was only partly inhibited by oxygen; NADPH and NADH served as cosubstrates. N-Nitromethylamine is also carcinogenic and was reduced by liver cytoplasm to a protein binding species (methyldiazohydroxide?).

Animals↗
PubMed1991

Some approaches to prevention of endogenous formation of N-nitrosamines in humans.

In a series of experiments on formation of N-nitrosamines from precursors in the gastric juice, we investigated individual nitrosation capacity and the influence of inhibitors on this process. In the presence of a molar ratio of 2:1 ascorbic acid:NaNO2, we found increased nitrosamine formation in 34% of gastric juice samples. Ferulic acid and caffeic acid generally suppressed nitrosation at high concentrations and stimulated it at low concentrations. The concentration at which the transition from a stimulating to an inhibitory effect occurs depends on individual differences in the gastric juice.

Antioxidants↗
PubMed1991

Pharmacological evaluation of certain novel prolonged-acting local anaesthetics. In vivo rat sciatic nerve block.

Some new 2-phenoxyethyldialkylamines in previous studies had proved to be superior to other standard drugs in respect of local anaesthetic activity. To confirm their intensity and duration of action, the two outstanding compounds were selected for further pharmacological studies on the rat sciatic nerve preparation in vivo. Their activity and duration of action were determined by a double-blind controlled trial (at the later stage) and in two stages. The test compounds showed comparable rates of onset of motor analgesia (5-10 min). They also displayed quick recovery from complete analgesia, typically being around 10 min after the first sign of a recovery of motor function was observed. In addition, no systemic or local untoward effects were noticed. Bupivacaine produced drowsiness in the rats.

Anesthetics, Local↗
PubMed1991

Studies on the drug binding of certain novel potential local anaesthetics.

One of the many factors affecting the response of an individual to a drug is the modification of its action by tissue and plasma proteins. Plasma proteins can be divided into three categories, viz., fibrinogen, globulins and albumin. Fibrinogen exhibits little reactivity with respect to drugs, being concerned solely with blood clotting, whereas globulins may have affinity for various endogenous compounds. Albumin, which constitutes around 4% of human serum, has the capability to bind reversibly or irreversibly to a wide range of substances. Generally, it has been found that albumins are particularly responsible for binding of local anaesthetics in plasma, but another binding factor may be lipoproteins present in blood cell membranes. Moreover, the transport of local anaesthetics to the site of action in the nerve membrane is influenced by their affinity for proteins present in extracellular fluids either at the site of injection, or surrounding the nerve fibres. Accordingly, systematic investigations on the protein binding characteristics of certain novel potential local anaesthetics was initiated with a view to ascertaining whether the duration of action of local anaesthetics could be correlated with their affinity for protein. The technique of equilibrium dialysis was used for measurements of drug-protein binding. This consists basically of two compartments separated by a semi-permeable cellulose membrane through which only free, unbound drug molecules can diffuse. The results indicate that there is no significant relationship between the extent of drug-protein binding and duration of local anaesthesia produced by these test compounds in the intradermal wheal test on the guinea-pig.

Anesthetics, Local↗
PubMed1990

Antibacterial activity of new synthesized amino-oxides and quaternary ammonium salts.

An amino oxide and three quaternary ammonium salts were investigated for antimicrobial activity. All compounds had low MIC against gram positive bacteria. Despite high MIC the ammonium salts gave good killing of Pseudomonas aeruginosa in time kill experiments. These quaternary ammonium salts may be useful for disinfection as they are easily broken down in the environment.

Bacteria↗
PubMed1990

Crystallization of membrane proteins: bovine rhodopsin.

The conditions for crystallization of the integral membrane protein bovine rhodopsin were determined. Crystals form over a wide range of protein concentration (0.4-15 mg ml-1) and pH (5.5-7.5) in detergent solutions of octyl-polyoxyethylene (o-POE) that contain inorganic salts as precipitants. Crystallization occurs in the detergent-rich phase under conditions of phase separation. This corroborates the results of experiments on the phase behavior of the detergent solution and on the distribution of rhodopsin between the salt-rich and detergent-rich phases formed at high salt concentrations. Crystals were needle shaped, and the best crystals were obtained by vapour diffusion, at room temperature, of a 2.5 mg ml-1 protein solution in a 1.5% (v/v) o-POE solution containing 1.5 M ammonium sulphate (pH 7.0) against unbuffered 2.85 M ammonium sulphate. The crystals thus produced had dimensions of approximately 70 microns x 70 microns x 1000 microns. These crystals were too small to allow X-ray diffraction studies of rhodopsin structure, but electron microscopic studies of negatively stained thin crystals allowed the definition of the projection belonging to the two-sided plane group p21, and showed unit cell parameters alpha (50 A), b (72 A), and gamma (90 degrees).

Animals↗
PubMed1986

A rapid versatile microassay for cellular retinol-binding protein using Lipidex-1000 microcolumns.

A new, rapid and versatile microassay for cellular retinol-binding protein has been developed based on separation of bound and free ligand by means of Lipidex-1000, a hydrophobic Sephadex derivative. This requires quantitative manipulation of retinol in aqueous solution. The tendency of retinol to adhere to glass and plastic surfaces was overcome by addition of the detergent Ammonyx LO, which yields a micellar dispersion. Detergent concentrations up to 10 mM did not interfere with binding of retinol to Lipidex-1000 or binding protein. The binding capacity of Lipidex-1000 was found to exceed 400 nmol of retinol per ml of gel. Retinal pigment epithelium (RPE) cells were used as a source for cRBP (cellular retinol-binding protein). The binding protein is saturated with ligand by incubation for 60 min at room temperature at concentrations of free retinol over 180 nM. Separation of protein-bound retinol from free retinol is achieved via Lipidex-1000: protein-bound (specific and nonspecific) retinol is not retained and is eluted by buffer with the protein fraction. Free retinol is retained by Lipidex and is subsequently recovered by elution with methanol. Total recovery of ligand approaches 100%. Analysis time is about 4 hr for a maximum of ca. 50 samples. Nonspecific protein binding can be determined equally effectively either by incubation with 3 mM PCMBS or by addition of a 100-fold molar excess of nonlabeled retinol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effect of some 4-alkyl-5-dimethylamino-1-phenyl-1-penten-3-one hydrochlorides and related compounds on respiration in mouse liver mitochondria.

5-Dimethylamino-1-phenyl-1-penten-3-one hydrochloride (1a) has high inhibiting properties in mitochondria isolated from mice liver. Substitution at the 4-methylene group of 1a by different alkyl substituents lead to compounds with wide variation in respiration-inhibiting properties. No correlations were found between either the Charton steric parameter (v), Taft inductive value (f*) or fragmental constant (f) of the substituents at position 4 of the Mannich bases with inhibition of respiration. However the biological results suggested two receptor sites were present in the mitochondria which may interact with the Mannich bases namely a common receptor for all compounds and in addition a narrow hydrophobic binding area which can accommodate a n-butyl or higher alkyl groups which are present in some of the compounds.

Animals↗
PubMed1987

[Determination of N-nitroso compounds in the gastric juice for evaluation of the individual nitrosating capacity of the body].

The article deals with a comparison of the results of human body nitrosating ability determination by two methods: (a) nitroso compound (NC) assay in diurnal urine after oral administration of its precursors, and (b) assay of the same in gastric juice after in vitro addition of precursors. The data for the first part of the investigation were obtained from the literature, and for the second one--from the experiments by the authors. Both studies used essentially identical groups of patients, primarily those suffering gastrointestinal pathology. Since the results matched to a considerable degree, it was inferred that (1) gastric juice is a factor of body nitrosating ability, and (2) in vitro determinations of said ability in gastric juice are fully justified. Moreover, the latter procedure is sometimes more practicable, particularly, in view of the marked relationship between nitrosating ability, and, especially, the efficacy of inhibitors of NC endogenous synthesis, on the one hand, and the individual characteristics of the body, on the other.

Aminopyrine↗