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Pharmacological characterization of rat jejunal contractility after chronic ablation of the myenteric plexus.

The authors have pharmacologically characterized longitudinal muscle contractility of the isolated rat jejunum chronically devoid of myenteric neurons. The myenteric plexus of a 3- to 4-cm segment of rat jejunum was ablated by serosal application of the cationic surfactant benzalkonium chloride (BAC). Fifteen days after treatment, both BAC-treated and untreated control jejunal segments were removed from each animal for pharmacological studies. BAC-treated tissues did not respond to the ganglionic stimulants nicotine, 1,1-dimethyl-4-phenylpiperazinium iodide and McN-A-343 or to the acetylcholinesterase inhibitor physostigmine. Short-pulse duration transmural electrical stimulation (0.1 msec) caused a frequency-dependent, tetrodotoxin-sensitive contraction in control but not BAC-treated tissues. Long-pulse duration transmural electrical stimulation (5.0 msec) contracted both control and BAC-treated jejunum. These contractions were partially reduced but not completely blocked by tetrodotoxin. To assess smooth muscle function, the mechanical responses to the muscarinic receptor agonist carbachol were examined. Carbachol contracted both control and BAC-treated tissues with maximal responses and ED50 values that were not significantly different. In addition, the maximal tension development produced by 10(-2) M barium chloride in similar lengths of control and BAC-treated jejunal segments was not significantly different. These studies demonstrate that chronic ablation of the myenteric plexus by serosal application of BAC essentially eliminates neuronally mediated responses without a concomitant alteration in longitudinal muscle contractility. Because nerve-mediated longitudinal muscle responses are lost despite the presence of an intact submucosal plexus in the BAC-treated jejunum, our data suggest that the motor neurons innervating the rat jejunal longitudinal muscle are located in the myenteric plexus.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗

The in vitro impact of moxifloxacin and gatifloxacin concentration (0.5% vs 0.3%) and the addition of benzalkonium chloride on antibacterial efficacy.

PURPOSE: Varied concentrations of moxifloxacin (MOX) and gatifloxacin (GAT) and the addition of 0.005% benzalkonium chloride (BAK) were evaluated for eliminating Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA), and coagulase-negative Staphylococcus (CNS). DESIGN: In vitro laboratory investigation. METHODS: The time-kill survival of SA, PA, and CNS were tested at one, two, three, six, eight, and 24 hours to: (1) Mueller-Hinton broth, (2) BAK, (3) 0.5% MOX, (4) 0.5% GAT, (5) 0.3% MOX, (6) 0.3% GAT, (7) 0.3% GAT plus BAK, (8) 0.5% MOX plus BAK, (9) 8 microg/ml GAT, and (10) 8 mug/ml MOX. Antibiotic interactions (GAT and BAK) were determined by checkerboard testing. The outcome measures were (1) time-to-kill, (2) killing-rates, and (3) fractional inhibitory concentration (FIC) indices. RESULTS: MOX and GAT at either 0.5% or 0.3% had equivalent antibacterial effects. BAK alone or the addition of BAK to either antibiotic eliminated SA and CNS within one hour, whereas 0.3% GAT plus BAK eliminated bacteria faster than 0.5% MOX (P = .016). For PA, BAK alone had no antibacterial effect. The kill rates of MOX and GAT were equivalent. FIC indices indicated that GAT and BAK were indifferent against SA and CNS, but antagonistic to PA. CONCLUSION: As a preservative, MOX and GAT have equivalent antibacterial activity with similar killing rates. BAK appears to independently complement GAT for eliminating SA and CNS, but has no effect on PA. The in vitro predictive clinical effect due to varied antibiotic concentration and the addition of BAK requires confirmatory clinical studies for validation.

Anti-Infective Agents↗

Resistance of spheroplasts and whole cells of Pseudomonas aeruginosa to bactericidal activity of various biocides: evidence of the membrane implication.

To emphasise the role of outer and inner membranes in the resistance of Pseudomonas aeruginosa to bactericidal activity of various disinfectants, spheroplasts and whole cells were compared. Spheroplasts are more sensitive than whole cells to quaternary ammonium compounds such as didecyl dimethyl ammonium bromide (DDAB) and C16-benzalkonium chloride. The outer membrane acts as a barrier to prevent these disinfectants from entering the cell. It seems to have no influence on activities of smaller molecules such as C12, C14-benzalkonium chlorides and sodium dichloroisocyanurate. For tri-sodium phosphate, the presence of outer membrane emphasized the action of the molecule. Moreover, resistance of DDAB-adapted spheroplasts to bactericidal activity of DDAB is higher than the resistance of non-adapted spheroplasts. This suggests that the inner membrane could also play a role in resistance to DDAB.

Anti-Infective Agents, Local↗

Correlation of impedance response patterns to histological findings in irritant skin reactions induced by various surfactants.

We have explored the use of measurements of electrical impedance to discriminate between the effects of different irritant substances upon the skin, and have studied the relationships between impedance and histopathological change. Three compounds with different chemical profiles were tested on volunteers: sodium lauryl sulphate, benzalkonium chloride and nonanoic acid. The concentrations selected were such that each irritant produced responses of a similar order, as judged by visual scores. The magnitude and phase of electrical impedance were measured and, for comparison, also the transepidermal water loss. Four physically distinct aspects (indices) were devised from the impedance data, and the values obtained were statistically analysed. The three irritants produced different effects, giving distinctive impedance patterns. These were also found to be reflected by three different types of histopathological skin response. Our results suggest that the indices can be used to classify irritant contact reactions, which it is difficult or impossible to achieve by other non-invasive techniques.

Adult↗

Nitrosation of quaternary ammonium compounds in vivo in the Wistar rat.

Animals dosed orally with nitrite (1.5 X 10(-3) mol/kg) and nonyl dimethylbenzylammonium bromide (2.9 X 10(-4) mol/kg) exhibit liver damage within two hours; cetyl trimethylammonium bromide plus nitrite was not significantly hepatotoxic. Both nonyl dimethylbenzyl ammonium bromide and cetyl trimethylammonium bromide were demethylated by rat-liver microsomal preparations; substrate concentrations of 1 mM or more were inhibitory. Bile from rats given i.p. doses of cetyl trimethylammonium bromide, nonyl dimethylbenzylammonium bromide or dodecyl dimethylbenzylammonium bromide contains only metabolites, no unchanged compounds were detected.

Administration, Oral↗

Effects of surfactants on the permeability of canine oral mucosa in vitro.

The effect of 3 cationic, 1 anionic, and 1 non-ionic surfactant on the permeability of oral frenulum removed from anesthetized dogs was determined in vitro. Permeability to 12 organic compounds was measured in the presence and absence of surfactant. Cetylpyridinium chloride, cetyltrimethylammonium bromide, benzalkonium chloride and sodium lauryl sulfate, at concentrations from 0.025-1.0% caused dose-related increases in permeability to each of the solutes tested, whereas polysorbate 80 caused an increase in permeability to only 3 solutes, and this occurred only at the highest surfactant concentration employed.

Animals↗

The feasibility of replacing antibiotics by quaternary ammonium compounds in topical antimicrobial acne therapy.

Determinations of the minimum inhibitory concentrations for various antimicrobial surfactants with reference to the bacteria P. acnes, P. granulosum, and St. epidermidis are reported. The results show that quaternary ammonium compounds can display minimum inhibitory concentrations corresponding to those of relevant antibiotics. With the especially effective substance fractionated dimethylcocobenzalkoniumchloride )ARQUAD DMMCD-B), it could be further shown that with in vivo application in 70% isopropanol or in an ethanol-containing film mask ointment suppression can be obtained of P. acnes, all propionibacteria added, and all pilosebaceous duct bacteria which can be cultured under anaerobic conditions. The studies may point out a way of replacing antibiotics in the antimicrobial therapy of acne by quaternary ammonium compounds.

Acne Vulgaris↗