New biologically active ionic liquids with benzethonium cation-efficient SAR inducers and antimicrobial agents

BACKGROUND

An urgent need to find new methods for crop protection remains open due to the withdrawal from the market of the most toxic pesticides and increasing consumer awareness. One of the alternatives that can be used in modern agriculture is the use of bifunctional compounds whose actions towards plant protection are wider than those of conventional pesticides.

RESULTS

In this study, we present the investigation of the biological efficacy of nine dual-functional salts containing a systemic acquired resistance (SAR)-inducing anion and the benzethonium cation. A significant result of the presented study is the discovery of the SAR induction activity of benzethonium chloride, which was previously reported only as an antimicrobial agent. Moreover, the concept of dual functionality was proven, as the application of presented compounds in a given concentrations resulted both in the control of human and plant bacteria species and induction of SAR.

CONCLUSION

The strategy presented in this article shows the capabilities of derivatization of common biologically active compounds into their ionic derivatives to obtain bifunctional salts. This approach may be an example of the design of potential new compounds for modern agriculture. It provides plants with two complementary actions allowing to provide efficient protection to plants, if one mode of action is ineffective. © 2024 Society of Chemical Industry.

Ketamine preservative benzethonium chloride potentiates hippocampal synaptic transmission and binds neurotransmitter receptors and transporters

Benzethonium chloride (BZT) is an excipient used in numerous products including (R,S)-ketamine (ketamine) drug formulations for human and veterinary use. Emerging evidence indicates BZT is pharmacologically active. BZT may therefore contribute to some of the clinical or preclinical effects observed with ketamine. In the present study, we evaluated: (i) the affinity of BZT for neurotransmitter receptors and transporters, (ii) the effects of BZT on hippocampal synaptic transmission in vitro, and (iii) plasma and brain concentrations of BZT following its intraperitoneal administration to male CD1 mice. Radioligand binding assays determined the affinity of BZT for neurotransmitter targets. Effects of BZT on field excitatory postsynaptic potentials (fEPSPs) were established via electrophysiological recordings from slices collected from male C57BL/6J mice. The binding assays revealed that BZT binds to numerous receptors (e.g., σ2 Ki = 7 nM) and transporters (e.g., dopamine transporter Ki = 545 nM). Bath application of BZT potentiated hippocampal fEPSPs in mouse hippocampal slices with an EC50 of 2.03 nM. Following intraperitoneal administration, BZT was detected in the plasma, but not in the brain of mice. These data highlight that studies measuring peripheral endpoints or directly exposing systems, in vitro, intracerebroventricularly, or intracortically, to BZT-containing formulations should account for the direct effects of BZT. Our findings also suggest that earlier data attributing pharmacological effects to ketamine may be confounded by BZT and that additional investigation into the functional impact of BZT is warranted. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Identification and functional validation of FDA-approved positive and negative modulators of the mitochondrial calcium uniporter

The mitochondrial calcium uniporter (MCU), the highly selective channel responsible for mitochondrial Ca²⁺ entry, plays important roles in physiology and pathology. However, only few pharmacological compounds directly and selectively modulate its activity. Here, we perform high-throughput screening on a US Food and Drug Administration (FDA)-approved drug library comprising 1,600 compounds to identify molecules modulating mitochondrial Ca²⁺ uptake. We find amorolfine and benzethonium to be positive and negative MCU modulators, respectively. In agreement with the positive effect of MCU in muscle trophism, amorolfine increases muscle size, and MCU silencing is sufficient to blunt amorolfine-induced hypertrophy. Conversely, in the triple-negative breast cancer cell line MDA-MB-231, benzethonium delays cell growth and migration in an MCU-dependent manner and protects from ceramide-induced apoptosis, in line with the role of mitochondrial Ca²⁺ uptake in cancer progression. Overall, we identify amorolfine and benzethonium as effective MCU-targeting drugs applicable to a wide array of experimental and disease conditions.

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We screen an FDA-approved drug library for mitochondrial Ca²⁺ uptake modulators

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Amorolfine and benzethonium modulate MCU activity

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Amorolfine increases MCU-dependent mitochondrial metabolism and muscle size

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Benzethonium decreases MCU-dependent cancer cell growth and migration

Evaluation of an Alcohol-Based Surgical Hand Disinfectant Containing a Synergistic Combination of Farnesol and Benzethonium Chloride for Immediate and Persistent Activity Against Resident Hand Flora of Volunteers and With a Novel In Vitro Pig Skin Model

Objective.

To evaluate the immediate, persistent and sustained in vivo activity of an alcohol-based surgical hand disinfectant, consisting of a zinc gel and a preservative system containing a synergistic combination of farnesol and benzethonium chloride (ZBF disinfectant), and to develop a pig skin model for in vitro evaluation of the immediate and persistent efficacy of alcohol-based surgical hand disinfectants against resident hand flora.

Design.

The in vivo immediate, persistent, and sustained activity of ZBF disinfectant was evaluated using human volunteers and the “glove-juice” method described in the US Food and Drug Administration's Tentative Final Monograph (FDA-TFM) for Healthcare Antiseptic Products. A novel in vitro pig skin model was developed to compare the immediate and persistent activity of alcohol-based surgical hand disinfectants against resident flora usingStaphylococcus epidermidisas the test organism. Four alcohol-based surgical hand disinfectants were evaluated using this model.

Results.

The results for the ZBF disinfectant exceed the FDA-TFM criteria for immediate, persistent, and sustained activity required for surgical hand disinfectants. The reduction factors for the 4 hand disinfectants obtained using the pig skin model show good agreement with the log10reductions in concentrations of hand flora obtained using human volunteers to test for immediate and persistent activity.

Conclusion.

The ZBF disinfectant we evaluated met the FDA-TFM criteria for surgical hand disinfectants. The immediate and persistent efficacy of the surgical hand disinfectants evaluated with the novel pig skin model described in this study shows good agreement with the results obtained in vivo.

Effect of channel blockers on the smooth muscle of the adult crop of the queen blowfly, Phormia regina

Few studies have examined the various factors affecting the rate of contraction of the supercontractile muscles of the crop lobes of adult Phormia regina Meigen (Diptera: Calliphoridae). Using an in situ bioassay of the crop organ, various ion channel blockers were tested and it was demonstrated that in all cases the blockers (i.e., against the following conductances: Cl⁻, Ca²⁺, Na⁺, and a FMRF-amide action) significantly reduced the contraction rates of the crop lobes, which were filled with 4.5 µL of 1.0 M sucrose containing 10 mM of the dye amaranth. Benzyltrimethylammonium chloride, never before reported for its effect on insect muscle, was as effective in suppressing crop muscle contraction as benzethonium chloride, which is a reported agonist of dromyosuppressin.

A novel flow cytometric HTS assay reveals functional modulators of ATP binding cassette transporter ABCB6

ABCB6 is a member of the adenosine triphosphate (ATP)-binding cassette family of transporter proteins that is increasingly recognized as a relevant physiological and therapeutic target. Evaluation of modulators of ABCB6 activity would pave the way toward a more complete understanding of the significance of this transport process in tumor cell growth, proliferation and therapy-related drug resistance. In addition, this effort would improve our understanding of the function of ABCB6 in normal physiology with respect to heme biosynthesis, and cellular adaptation to metabolic demand and stress responses. To search for modulators of ABCB6, we developed a novel cell-based approach that, in combination with flow cytometric high-throughput screening (HTS), can be used to identify functional modulators of ABCB6. Accumulation of protoporphyrin, a fluorescent molecule, in wild-type ABCB6 expressing K562 cells, forms the basis of the HTS assay. Screening the Prestwick Chemical Library employing the HTS assay identified four compounds, benzethonium chloride, verteporfin, tomatine hydrochloride and piperlongumine, that reduced ABCB6 mediated cellular porphyrin levels. Validation of the identified compounds employing the hemin-agarose affinity chromatography and mitochondrial transport assays demonstrated that three out of the four compounds were capable of inhibiting ABCB6 mediated hemin transport into isolated mitochondria. However, only verteporfin and tomatine hydrochloride inhibited ABCB6's ability to compete with hemin as an ABCB6 substrate. This assay is therefore sensitive, robust, and suitable for automation in a high-throughput environment as demonstrated by our identification of selective functional modulators of ABCB6. Application of this assay to other libraries of synthetic compounds and natural products is expected to identify novel modulators of ABCB6 activity.

Leishmania major: in vitro and in vivo anti-leishmanial activity of paromomycin ointment (Leshcutan) combined with the immunomodulator Imiquimod

Paromomycin at 25, 50 and 100 microg/ml, inhibited the growth of Leishmania major amastigotes by 34.5%, 61.2%, 74.9% and 85.4%, 89.9%, 95.7% on the 2nd and the 4th day of treatment in culture, respectively. Methylbenzethonium chloride at 0.1 and 0.5 microg/ml and Imiquimod at 5 and 10 microg/ml, administered separately, inhibited the parasite development by 39.5% and 65.2% and 31.5% and 47.7%, respectively. Imiquimod (5-10 microg/ml) combined with either paromomycin (25, 50 and 100 microg/ml) or methylbenzethonium chloride (0.1 and 0.5 microg/ml) showed an anti-leishmanial additive effect. A 10 day topical treatment, twice daily, with an ointment containing 15% paromomycin and 12% methylbenzethonium chloride (Leshcutan), either undiluted or diluted 1:5 in soft white paraffin combined with 5% Imiquimod cream (Aldara), was as effective as Leshcutan given alone. The present study suggests that a combination of Aldara and Leshcutan is as effective as Leshcutan given alone in the topical treatment of CL caused by L. major.

Benzethonium chloride: a novel anticancer agent identified by using a cell-based small-molecule screen

PURPOSE

This study aims to identify a novel therapeutic agent for head and neck cancer and to evaluate its antitumor efficacy.

EXPERIMENTAL DESIGN

A cell-based and phenotype-driven high-throughput screening of approximately 2,400 biologically active or clinically used compounds was done using a tetrazolium-based assay on FaDu (hypopharyngeal squamous cancer) and NIH 3T3 (untransformed mouse embryonic fibroblast) cells, with secondary screening done on C666-1 (nasopharyngeal cancer) and GM05757 (primary normal human fibroblast) lines. The "hit" compound was assayed for efficacy in combination with standard therapeutics on a panel of human cancer cell lines. Furthermore, its mode of action (using transmission electron microscopy and flow cytometry) and its in vivo efficacy (using xenograft models) were evaluated.

RESULTS

Benzethonium chloride was identified as a novel cancer-specific compound. For benzethonium (48-hour incubation), the dose required to reduce cell viability by 50% was 3.8 micromol/L in FaDu, 42.2 micromol/L in NIH 3T3, 5.3 micromol/L in C666-1, and 17.0 micromol/L in GM05757. In vitro, this compound did not interfere with the effects of cisplatin, 5-fluorouracil, or gamma-irradiation. Benzethonium chloride induced apoptosis and activated caspases after 12 hours. Loss of mitochondrial membrane potential (DeltaPsiM) preceded cytosolic Ca2+ increase and cell death. In vivo, benzethonium chloride ablated the tumor-forming ability of FaDu cells, delayed the growth of xenograft tumors, and combined additively with local tumor radiation therapy. Evaluation of benzethonium chloride on the National Cancer Institute/NIH Developmental Therapeutics Program 60 human cancer cell lines revealed broad-range antitumor activity.

CONCLUSIONS

This high-throughput screening identified a novel antimicrobial compound with significant broad-spectrum anticancer activity.

Hexadecyl-phosphorylcholine ointment for treatment of cutaneous leishmaniasis: an animal trial

A placebo-controlled trial compared 6% hexadecyl-phosphorylcholine (HePC) and 12% benzethonium chloride ointment with placebo ointment for treatment of cutaneous leishmaniasis. Cutaneous lesions were experimentally induced by inoculation with leishmania promastigotes in 60 golden hamsters. Forty (40) animals were treated with drug and 20 with placebo ointment applied twice daily for 15 days. After treatment, all lesions were significantly reduced in size in the treatment group compared with the placebo ointment. No parasites were detected in smears from 35/40 of the drug-treated lesions and no relapses occurred over 120 days of observation.

In vitro short-time killing activity of povidone-iodine (Isodine Gargle) in the presence of oral organic matter

In order to estimate the clinical efficacy of a povidone-iodine oral antiseptic (PVP-I) on oral bacterial infectious diseases, we studied the effect of oral organic matter on the in vitro killing activity of PVP-I. In addition, we compared the in vitro short-time killing activity of PVP-I with those of other oral antiseptics using mouth-washing and gargling samples collected from healthy volunteers. When any of the mouth-washing and gargling samples was used, the standard (0.23-0.47%) or lower concentrations of PVP-I killed methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, including multidrug-resistant strains, within 15-60 s in the presence of oral organic matter. 0.02% benzethonium chloride (BEC) and 0.002% chlorhexidine gluconate (CHG) did not show effects against MRSA and P. aeruginosa (including multidrug-resistant strains) in mouth-washing and gargling samples even after 60 s. The above-mentioned results show that the in vitro killing activity of the standard concentration of PVP-I was hardly affected by the oral organic matter and that a mouth-washing or gargling solution containing PVP-I has a stronger bactericidal activity than BEC and CHG. Although mouth-washing and gargling samples were obtained from healthy individuals in this study, PVP-I may be used for protection against infections in patients with various diseases, if proper concentrations and usage are encouraged.

Efficacy of an alcohol-based healthcare hand rub containing synergistic combination of farnesol and benzethonium chloride

Healthcare workers are required to disinfect the hands several times a day using hand disinfectants, which leads to chronic hand exposure to high levels of antimicrobials contained in the disinfectants, which could compromise the skin integrity. This problem may be addressed by developing hand disinfectants containing synergistic combinations of small amounts of antimicrobials and other agents. The synergistic effect of farnesol and essential oils with several antimicrobials was studied in vitro to select an effective antimicrobial system in preservative concentration for use in healthcare hand rub. Farnesol and lemon oil showed synergistic activity against S. aureus, in combination with benzalkonium chloride and benzethonium chloride, but not with other antimicrobials studied. All essential oils studied showed synergy with benzethonium chloride against Staphylococcus aureus and Escherichia coli. An alcohol-based healthcare hand rub (ZBF hand rub) containing this unique synergistic combination of farnesol and benzethonium chloride was then developed and its efficacy as a healthcare hand rub was evaluated in human volunteers according to the US FDA-TFM protocol using Serratia marcescens as a marker organism. The ZBF hand rub showed a 3.22 log(10) reduction in the microbial count after the first application and a 5.49 log(10) reduction after the tenth application in vivo and exceeds the US FDA-TFM criteria for healthcare hand rub. The ZBF hand rub did not irritate the hands when tested on human volunteers when applied 10 times everyday for five consecutive days. The ZBF hand rub exhibits more than 5.5 log(10) reduction in the microbial count within 15s and more than 2.8 log(10) reduction in the two types of viruses tested within 30s in vitro. When evaluated in an in vitro pig skin model, the ZBF hand rub shows better prolonged activity (20-35 min post-application) against transient bacteria (S. aureus and E. coli) compared to other alcohol-based hand rubs. These findings suggest that the use of the ZBF hand rub amongst health care workers may lower the risk of chronic hand exposure to high levels of antimicrobials without compromising the efficacy.

Cytotoxic effects of dental desensitizers on human gingival fibroblasts

The purpose of this study was to evaluate the effects of three different desensitizers on the cell viability and morphology of human gingival fibroblasts (HGF). Human gingival tissues were obtained from individuals who have clinically, healthy periodontium. HGF were grown at 37 degrees C in humidified atmosphere of 5% CO2 in Dulbecco's modified eagle's medium, supplemented with glutamine, penicillin, streptomycin, and 10% fetal bovine serum. The cells were treated with different concentrations (0.1, 0.3, and 0.5 microL/mL) of desensitizers (Gluma Desensitizer, Seal&Protect, and MicroPrime). After 24- and 48-h exposure to the desensitizer solutions, the viable cells were examined using a hemocytometer. To monitor HGF viability, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay was used and cell morphology was also observed at 48 h. Following exposure to concentrations of 0.1 microL/mL of test materials for 24 h, cell survival rates for Gluma Desensitizer (106%) and Micro Prime (62%) were not significantly different from the control, while it was significant for Seal&Protect (50%). Growing cells were significantly inhibited by all tested materials for 48 h (p < 0.05) in survival rates of 51, 47, and 31%, respectively. On the basis of the MTT assay, the cytotoxic effect of MicroPrime was more prominent, especially at high concentrations, than does Gluma Desensitizer and Seal&Protect. After exposure to Seal&Protect and MicroPrime, HGF became retracted, rounded in appearance and had loss of normal organization, leading to enlargement of intercellular space when compared with Gluma Desensitizer. As a conclusion, taking the limitations of an in vitro experiment into consideration, the cytotoxic effects were varied, depending on the chemical composition and exposure periods of the tested desensitizers.

Comparative efficacy of hand hygiene agents in the reduction of bacteria and viruses

Background

Health care-associated infections most commonly result from person-to-person transmission via the hands of health care workers.

Methods

We studied the efficacy of hand hygiene agents (n = 14) following 10-second applications to reduce the level of challenge organisms (Serratia marcescens and MS2 bacteriophage) from the hands of healthy volunteers using the ASTM-E-1174-94 test method.

Results

The highest log₁₀ reductions of S marcescens were achieved with agents containing chlorhexidine gluconate (CHG), triclosan, benzethonium chloride, and the controls, tap water alone and nonantimicrobial soap and water (episode 1 of hand hygiene, 1.60-2.01; episode 10, 1.60-3.63). Handwipes but not alcohol-based handrubs were significantly inferior from these agents after a single episode of hand hygiene, but both groups were significantly inferior after 10 episodes. After a single episode of hand hygiene, alcohol/silver iodide, CHG, triclosan, and benzethonium chloride were similar to the controls in reduction of MS2, but, in general, handwipes and alcohol-based handrubs showed significantly lower efficacy. After 10 episodes, only benzethonium chloride (1.33) performed as well as the controls (1.59-1.89) in the reduction of MS2.

Conclusions

Antimicrobial handwashing agents were the most efficacious in bacterial removal, whereas waterless agents showed variable efficacy. Alcohol-based handrubs compared with other products demonstrated better efficacy after a single episode of hand hygiene than after 10 episodes. Effective hand hygiene for high levels of viral contamination with a nonenveloped virus was best achieved by physical removal with a nonantimicrobial soap or tap water alone.

In vitro analysis of the digestive enzymes amylase and alpha-glucosidase in the midguts of Locusta migratoria L. in response to the myosuppressin, SchistoFLRFamide

We have investigated the effect of the locust myosuppressin, SchistoFLRFamide, on the activity of amylase and alpha-glucosidase in the midgut of 2-week old male locusts. Total enzyme activity in the lumen contents and tissue extracts of midguts responds to SchistoFLRFamide in a dose-dependent manner that appears to vary with the feeding state of the locust and duration of exposure to the peptide. Starvation for 24h prior to assessment alters the distribution of enzyme activity between the midgut lumen contents and tissue extracts in response to SchistoFLRFamide when compared with fed locusts. Duration of exposure to SchistoFLRFamide also alters the distribution of total amylase and alpha-glucosidase activity; as duration of exposure increases, lower concentrations of SchistoFLRFamide increase total enzyme activity in the lumen contents while decreasing total enzyme activity in the tissue extracts. We suggest that the minimum amino acid sequence in SchistoFLRFamide necessary to increase both amylase and alpha-glucosidase activity is DHVFLRFamide. We have determined that two other peptides endogenous to the locust, AFIRFamide and GQERNFLRFamide, increase amylase and alpha-glucosidase activity in midgut lumen contents.

Comparative analysis of antibiotic and antimicrobial biocide susceptibility data in clinical isolates of methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa between 1989 and 2000*

AIMS

To analyse population minimum inhibitory concentrations (MICs) data from clinical strains of Staphylococcus aureus and Pseudomonas aeruginosa for changes over a 10-year period and to look for correlations between the antimicrobials tested.

METHODS AND RESULTS

Data from the MIC study of 256 clinical isolates of Staph. aureus [169 methicillin-sensitive Staph. aureus (MSSA), 87 methicillin-resistant Staph. aureus (MRSA)] and 111 clinical isolates of Ps. aeruginosa against eight antimicrobial biocides and several clinically relevant antibiotics was analysed using anova, Spearman-Rho correlation and principal component analysis. Comparisons suggest that alterations in the mean susceptibility of Staph. aureus to antimicrobial biocides have occurred between 1989 and 2000, but that these changes were mirrored in MSSA and MRSA suggests that methicillin resistance has little to do with these changes. Between 1989 and 2000 a sub-population of MRSA has acquired a higher resistance to biocides, but this has not altered the antibiotic susceptibility of that group. In both Staph. aureus and Ps. aeruginosa several correlations (both positive and negative) between antibiotics and antimicrobial biocides were found.

CONCLUSIONS

From the analyses of these clinical isolates it is very difficult to support a hypothesis that increased biocide resistance is a cause of increased antibiotic resistance either in Staph. aureus or in Ps. aeruginosa.

SIGNIFICANCE AND IMPACT OF THE STUDY

The observation of negative correlations between antibiotics and biocides may be a useful reason for the continued use of biocides promoting hygiene in the hospital environment.

Total Synthesis and Preliminary Biological Evaluation of cis-Solamin Isomers

An efficient total synthesis of cis-solamin (1) has been achieved in 21% overall yield and with a longest linear sequence of just 11 steps from aldehyde 8. A key feature of the approach was the use of asymmetric permanganate-promoted oxidative cyclization to introduce four of the five required stereocenters in a single step. The use of robust and chemoselective methodology meant that the use of protecting groups could be avoided during the assembly of cis-solamin (1) from the three fragments 23, 6, and 4. The methodology was also applied to the synthesis of three further cis-solamin isomers 2, ent-1, and ent-2. Cytotoxicity and hemolytic properties of cis-solamin isomers and synthetic intermediates are reported.

A nonpeptide provides insight into mechanisms that regulate Drosophila melanogaster heart contractions

Here we report the effect of a nonpeptide, benzethonium chloride (bztc), on Drosophila melanogaster larval, pupal, and adult heart rates in vivo. Benzethonium chloride reduced the frequency of spontaneous contractions in the D. melanogaster pupal heart, but not in the larval heart or the adult heart as measured in noninvasive whole animal preparations. When applied directly to the D. melanogaster heart, in the absence of hemolymph, bztc reduced the frequency of spontaneous contractions in larval, pupal, and adult hearts. These findings are consistent with the conclusion that bztc acts through or is regulated by different mechanisms in these three developmental stages. An alternative explanation is that larval hemolymph and adult hemolymph contain a material that interferes with the effect of the nonpeptide on heart contractions. Bztc mimicked the effect of the peptide dromyosuppressin (DMS) on the heart at an equivalent concentration; in contrast, 103-fold more nonpeptide is required to mimic the effect of DMS on fly gut. These findings are consistent with the presence of tissue-specific myosuppressin receptors or mechanisms.

Ketamine and its preservative, benzethonium chloride, both inhibit human recombinant alpha7 and alpha4beta2 neuronal nicotinic acetylcholine receptors in Xenopus oocytes

1. Ketamine is a dissociative anaesthetic that is formulated as Ketalar, which contains the preservative benzethonium chloride (BCl). We have studied the effects of pure racemic ketamine, the preservative BCl and the Ketalar mixture on human neuronal nicotinic acetylcholine receptors (nAChRs) composed of the alpha7 subunit or alpha4 and beta2 subunits expressed in Xenopus laevis oocytes. 2. Ketamine inhibited responses to 1 mM acetylcholine (ACh) in both the human alpha7 and alpha4beta2 nAChRs, with IC(50) values of 20 and 50 microM respectively. Inhibition of the alpha7 nAChRs occurred within a clinically relevant concentration range, while inhibition of the alpha4beta2 nAChR was observed only at higher concentrations. The Ketalar formulation inhibited nAChR function more effectively than was expected given its ketamine concentration. The surprising increased inhibitory potency of Ketalar compared with pure ketamine appeared to be due to the activity of BCl, which inhibited both alpha7 (IC(50) value of 122 nM) and alpha4beta2 (IC(50) value of 49 nM) nAChRs at concentrations present in the clinical formulation of Ketalar. 3. Ketamine is a noncompetitive inhibitor at both the alpha7 and alpha4beta2 nAChR. In contrast, BCl causes a parallel shift in the ACh dose-response curve at the alpha7 nAChR suggesting competitive inhibition. Ketamine causes both voltage-dependent and use-dependent inhibition, only in the alpha4beta2 nAChR. 4. Since alpha7 nAChRs are likely to be inhibited during clinical use of Ketalar, the actions of ketamine and BCl on this receptor subtype may play a role in the profound analgesia, amnesia, immobility and/or autonomic modulation produced by this anaesthetic.

Effectiveness of manual cleaning and disinfection of gastroendoscopes with 3% glutaraldehyde for decreasing risk of transmission of hepatitis C virus

OBJECTIVES

The effectiveness of manual cleaning and disinfection of gastroendoscopes with 3% glutaraldehyde in decreasing the risk of transmission of hepatitis C virus (HCV) was examined.

METHODS

Gastroendoscopes used for treatment of endoscopic esophageal variceal ligation in patients with HCV infection were manually cleaned and disinfected with 3% glutaraldehyde (n = 25), 2% glutaraldehyde (n = 17), or 0.1% benzethonium chloride (n = 25). Samples were obtained by pouring 20 ml of 0.9% NaCl solution into the biopsy-suction channel of the scope before and after cleaning and disinfection. HCV was detected with the polymerase chain reaction.

RESULTS

Of the 25 scopes in 3% glutaraldehyde group, nine (36%) were positive for HCV before cleaning and disinfection, but all became negative after cleaning and disinfection; the difference was statistically significant (p < 0.01). In contrast, in 2% glutaraldehyde group and in the routine cleaning group, there were no significant differences in the number of positive samples between before and after cleaning and disinfection.

CONCLUSION

Manual cleaning and disinfection of gastroscopes with 3% glutaraldehyde is useful for decreasing the risk of transmission of HCV among patients.

[Appraisal of fungistatic and fungicidal activities of quaternary compounds towards yeasts belonging to the genera Candida and Cryptococcus]

The fungistatic and fungicidal activities of five quaternary ammonium compounds towards Candida and Cryptococcus strains were determined using a bacteriological method adapted to mycological experiments. It could be deduced from this study that Cryptococcus in spite of the capsule around the cell were more sensitive than Candida and that the benzethonium chloride (BC) exhibited the most effective action against the whole yeasts. No resistance appeared, only Cryptococcus strain was less sensitive than the others.

Innervation of dromyosuppressin (DMS) immunoreactive processes and effect of DMS and benzethonium chloride on the Phormia regina (Meigen) crop

Antibody to the dipteran myosuppressin peptide, dromyosuppressin, TDVDHVFLRFamide, stained cells and fibers in the brain, optic lobes, subesophageal ganglion, and thoracico-abdominal ganglion of the blow fly, Phormia regina (Meigen). Dromyosuppressin-like immunoreactive fibers were detected in the cardiac recurrent nerve, hypocerebral ganglion/corpora cardiaca complex, crop duct, and crop. In order to explore the mechanisms involved in regulating crop movement, we established an in vitro bioassay. The basal rate of crop movement was 50.8 +/- 1.5 contractions per minute. Application of 1 microl of saline to the crop did not significantly affect the rate of movement compared to the basal rate (46.1 +/- 1.1 contractions per minute, P < 0.05). Application of 1 microl 10(-6) M dromyosuppressin or 1 microl 10(-3) M benzethonium chloride to the crop slowed the rate to 2.2 +/- 0.2 and 6.1 +/- 0.7 contractions per minute, respectively. Although other data have previously been interpreted to suggest that dipteran crop contractions do not include a neural component, the neuropeptide dromyosuppressin affected P. regina crop motility. Innervation of the crop and crop duct by dromyosuppressin immunoreactive processes that originated in the central nervous system and the effect of dromyosuppressin on crop muscle contractions suggest that dromyosuppressin is released locally to modulate crop contractions and that crop motility is under neural regulation. Myosuppressins isolated from numerous insects have a high degree of structure identity and reduce spontaneous muscle contractions of the hindgut, oviduct, and heart. Benzethonium chloride, previously identified as a myosuppressin agonist on the cockroach hindgut and locust oviduct, mimicked the effect of dromyosuppressin on the crop. This suggests that structural requirements for myosuppressin receptor binding in the cockroach hindgut, locust oviduct, and fruit fly crop are similar.

The modulation of skeletal muscle contraction by FMRFamide-related peptides of the locust

The external ventral protractor muscle of the VIIth abdominal segment, M234, is a skeletal muscle that possesses receptors that recognize a range of FMRFamide-related peptides and application of these peptides results in an increase in the amplitude of neurally evoked contractions with little or no effect on basal tonus. FLRFamide itself has the same biologic activity as the extended peptides, whereas truncation to LRFamide or RFamide results in a peptide with no biologic activity. The receptors recognizing these extended FLRFamides, which include SchistoFLRFamide, seem to be different from the SchistoFLRFamide receptors found on locust oviduct visceral muscle. SchistoFLRFamide and the non-peptide mimetic, benzethonium chloride (Bztc), increase the frequency and amplitude of miniature endplate potentials, increase the amplitude of neurally evoked excitatory junction potentials, and result in a hyperpolarisation of resting membrane potential. Bztc, however, also abolishes the active membrane response that may explain its ability to decrease neurally evoked contractions.

Wet decontamination-induced stratum corneum hydration--effects on the skin barrier function to diethylmalonate

Decontamination of chemical agents from the skin uses both dry and wet decontamination processes. Recent studies have shown that wet decontamination frequently results in stratum corneum hydration. To evaluate the hydration effect of wet decontamination on the skin barrier function and hence on the decontamination efficiency, a series of comparative studies were carried out on human skin contaminated with the nerve agent simulant diethylmalonate, using decontamination media having different salinity and surfactants. The results showed that, compared to non-decontaminated skin, remnant diethylmalonate on decontaminated skin penetrated at an accelerated rate in the immediate 2 h following decontamination. This transient enhancement effect, ranging from 20 to 98%, was depended on the nature of the decontamination media used and was more obvious in skin samples that were decontaminated 1 h postexposure. All decontamination media exhibited this effect, with the greatest enhancement observed in the following order: anionic surfactant > cationic surfactant > non-ionic surfactant > deionized water > 0.9% saline > 9% saline.

Effect of intravenous anesthetics on spontaneous and endotoxin-stimulated cytokine response in cultured human whole blood

BACKGROUND

Various anesthetics have been suggested to interfere with the immune system. The ability of leukocytes to express surface receptors and mediators is fundamental to a successful host defense. Therefore, the effects of intravenous anesthetics on cytokine release by leukocytes and expression of surface molecules known to modulate this response were determined.

METHODS

Concentration-dependent effects of thiopentone, etomidate, propofol, ketamine, midazolam, and fentanyl on spontaneous and endotoxin (lipopolysaccharide; 1 microg/ml)-stimulated cytokine release were studied in whole blood from volunteers (n = 6) cultured for 25 h. In addition, expression of the lipopolysaccharide-recognition molecule CD14 and the major histocompatibility complex class II molecule human leukocyte locus A system-DR (HLA-DR) on monocytes were assessed using flow cytometry.

RESULTS

All anesthetics studied elicited only minor effects on spontaneous cytokine release even at pharmacologic concentrations. However, expression density of CD14 was reduced in the presence of thiopentone, etomidate, and propofol, whereas HLA-DR was unaffected. Lipopolysaccharide-stimulated tumor necrosis factor response was inhibited by thiopentone (12.8% [median]; 7.6-18.8 [25-75 percentile]) of control, and ketamine (46.4% [median]; 44.4-56.4 [25-75 percentile]), at pharmacologic concentrations, whereas it was augmented even in the presence of low concentrations of propofol (172.3% [median]; 120.5-200.7 [25-75 percentile]). Ketamine additionally decreased the concentration of interleukin (IL)-1beta (14.8% [median]; 12.0-18.0 [25-75 percentile]). Release of IL-1 receptor antagonist (IL-1ra) was inhibited by thiopentone, etomidate, and propofol, whereas the same anesthetics increased IL-10 concentration simultaneously. Midazolam and fentanyl did not alter the concentrations of any cytokine.

CONCLUSIONS

These results suggest a complex modulation of the cytokine response by the studied anesthetics in cultured whole blood. Although effects on spontaneous cytokine release by leukocytes were negligible, some anesthetics affected their ability to respond to lipopolysaccharide.

Inactivation of human viruses by povidone-iodine in comparison with other antiseptics

Inactivation of a range of viruses, such as adeno-, mumps, rota-, polio- (types 1 and 3), coxsackie-, rhino-, herpes simplex, rubella, measles, influenza and human immunodeficiency viruses, by povidone-iodine (PVP-I) and other commercially available antiseptics in Japan was studied in accordance with the standardized protocol in vitro. In these experiments, antiseptics such as PVP-I solution, PVP-I gargle, PVP-I cream, chlorhexidine gluconate, alkyldiaminoethyl-glycine hydrochloride, benzalkonium chloride (BAC) and benzethonium chloride (BEC) were used. PVP-I was effective against all the virus species tested. PVP-I drug products, which were examined in these experiments, inactivated all the viruses within a short period of time. Rubella, measles, mumps viruses and HIV were sensitive to all of the antiseptics, and rotavirus was inactivated by BAC and BEC, while adeno-, polio- and rhinoviruses did not respond to the other antiseptics. PVP-I had a wider virucidal spectrum, covering both enveloped and nonenveloped viruses, than the other commercially available antiseptics.

Inhibition of acetylcholine esterase and choline esterase by benzethonium chloride and avoidance of the benzethonium chloride carry-over inhibitory effect

It has been shown that benzethonium chloride produces linear mixed-type inhibition of choline esterase and acetylcholine esterase. These enzymes also show-reagent-carry-over inhibition if the enzyme activities are measured in plastic cuvettes in which previously protein has been determined by the alkaline benzethonium chloride method. Choline esterase is about 10-fold more sensitive to benzethonium chloride than acetylcholine esterase. With acetylthiocholine as substrate Michaelis-Menten constants for choline esterase and acetylcholine esterase are 85 mumol/l and 102 mumol/l, respectively. Carry-over inhibitory effect of benzethonium chloride can be avoided by washing the cuvettes, after protein determination by the benzethonium chloride method, with 5 ml/l Triton X-100, 5 ml/l Tween 20 or 10 g/l sodium dodecyl sulphate. The latter has a disadvantage in that it precipitates out at low temperatures. The dry slide method (Johnson & Johnson) for serum choline esterase is free of the inhibitory effect until the concentration of benzethonium chloride in the sample reaches about 200 mumol/l.

Synergistic inhibition of muscarinic signaling by ketamine stereoisomers and the preservative benzethonium chloride

BACKGROUND

Ketamine (Ketalar; Parke-Davis, Morris Plains, NJ) has been shown to inhibit muscarinic signaling with a median inhibitory concentration (IC50) of 5.7 microM. Whereas Ketalar is a racemic mixture, recent interest has focused on clinical use of the S(+) ketamine isomer, which is three times as potent an analgesic as the R(-) isomer yet seems to be associated with fewer psychoactive side effects. Therefore, the authors studied the effects of S(+) and R(-) ketamine and the preservative benzethonium chloride on muscarinic signaling.

METHODS

Rat ml muscarinic acetylcholine receptors were expressed recombinantly in Xenopus laevis oocytes. Ca2(+)-activated Cl- currents in response to 10(-7) M acetyl-beta-methylcholine were determined by two-electrode voltage clamping in the presence of various concentrations of ketamine and benzethonium. Concentration-inhibition curves were constructed and used for algebraic and isobolographic analysis.

RESULTS

The IC50. was 125 +/- 33 microM for S(+) ketamine, and 91 +/- 19 microM for R(-) ketamine. This difference was not statistically significant, indicating that muscarinic inhibition by ketamine is not stereoselective. The R(-)/S(+) mixture had an IC50 of 48 +/- 1 microM, and thus the stereoisomers interact synergistically. When appropriate concentrations of benzethonium were added, an IC50 of 15 +/- 2 microM resulted.

CONCLUSIONS

The muscarinic inhibitory action of ketamine isomers is not stereoselective. Because S(+) ketamine is a significantly more potent analgesic, it should have less muscarinic inhibitory action than R(-) ketamine when used in clinically equivalent doses. A significant fraction of the muscarinic inhibitory action of Ketalar is due to the preservative benzethonium. If reconstituted with a different preservative, Ketalar might be a less potent muscarinic antagonist.

A nonpeptidal peptidomimetic agonist of the insect FLRFamide myosuppressin family

Benzethonium chloride (Bztc) is the first totally nonpeptide ligand for an insect, indeed an invertebrate, peptide receptor. Bztc mimics the inhibitory physiological activity of the myosuppressins, a subfamily of the FLRFamides, in three different insect bioassay systems. The inhibitory action of leucomyosuppressin and the nonpeptide Bztc in both the cockroach hindgut and the mealworm neuromuscular junction can be blocked by the lipoxygenase inhibitor, nordihydroguaiaretic acid, providing evidence for similar modes of action. Lipoxygenase metabolites of arachidonic acid may mediate inhibition of neuromuscular transmission by these two factors. In addition, Bztc competitively displaces a radiolabeled myosuppressin analogue from high- and low-affinity receptors of the locust oviduct. Thus, the nonpeptide interacts with both binding and activating regions of myosuppressin receptors. Molecular dynamics experiments in which selected functional groups of Bztc were fit onto corresponding functional groups of low-energy myosuppressin pentapeptide structures indicate how Bztc may mimic the myosuppressins at a molecular level. The discovery of Bztc as a nonpeptidal peptidomimetic analogue provides an opportunity to develop new pest management strategies by targeting an insect's own peptide receptor.

A nonpeptide agonist of the invertebrate receptor for SchistoFLRFamide (PDVDHVFLRFamide), a member of a subfamily of insect FMRFamide-related peptides

We describe a nonpeptide mimetic analog of an invertebrate peptide receptor. Benzethonium chloride (Bztc) is an agonist of the SchistoFLRFamide (PDVDHVFLRFamide) receptors found on locust oviducts. Bztc competitively displaces [125I-labeled Y1]SchistoFLRFamide binding to both high- and low-affinity receptors of membrane preparations. Bztc mimics the physiological effects of SchistoFLRFamide on locust oviduct, by inhibiting myogenic and induced contractions in a dose-dependent manner. Bztc is therefore recognized by the binding and activation regions of the SchistoFLRFamide receptors. This discovery provides a unique opportunity within insects to finally target a peptide receptor for the development of future pest management strategies.

Antiplaque activity of some antimicrobial agents using a simple in vitro method

Some antimicrobial compounds were tested for their antiplaque activity by a simple method involving measurement of the weight of Streptococcus sobrinus plaque on a glass surface. Chlorhexidine, cetylpyridinium chloride, and n-tetradecylamine reduced the weight of plaque produced by S. sobrinus in vitro; some N-palmityl and palmitoyl derivatives of polymethylenediamines were also found to possess antiplaque activity. The results suggest that an antiplaque effect does not necessarily depend on high bactericidal activity.

Inhibition of synaptosomal serotonin uptake by Ketalar

The effects of the clinical preparation of ketamine, Ketalar and its preservative, benzethonium chloride on [3H]5-hydroxytryptamine uptake were studied using rat brain synaptosomes. Ketalar caused a concentration-dependent inhibition of substrate uptake by the high affinity transport site (I50 = 20.2 +/- 2.75 microM) while benzethonium chloride had no effect. Kinetic analysis indicated the inhibition to be competitive with serotonin; the apparent km (54 nM) was increased nearly two-fold at 10 microM ketamine. This action may represent a mechanism involved in ketamine anesthesia.

Leishmania major: antileishmanial activity of methylbenzethonium chloride

Methylbenzethonium chloride (MBCl) decreased the growth of Leishmania major promastigotes and amastigotes in vitro. This decrease occurred during 4 days of exposure to the drug at concentrations of 0.1 to 2.5 micrograms ml-1. MBCl at 2 micrograms ml-1 killed almost 100% of the free living promastigotes and 87% of amastigotes within 4 days of treatment. Electron microscopy studies showed marked swelling of mitochondria in treated parasites. A possible additional effect on the parasite surface membrane is discussed.

Benzethonium chloride resistance in Pseudomonas aeruginosa isolated from clinical lesions

The benzethonium chloride resistance of 341 strains of Pseudomonas aeruginosa isolated from Jikei University Hospital was determined. The distribution pattern of the susceptibility to benzethonium chloride clearly revealed two peaks, and the resistance was differentiated by 1000 micrograms/ml (0.1%) of benzethonium chloride. The frequency of resistance to benzethonium chloride was 51.6%. Furthermore, the frequencies of resistance to SM, TC, CP, KM, GM, PIP, Hg, Cd, As and chlorhexidine were 42.5, 15.8, 41.3, 29.6, 14.0, 8.2, 88.3, 97.9, 97.1, and 74.5%, respectively.

Intrathecal ketamine with preservative - histological effects on spinal nerve roots of baboons

Ketamine, an analgesic-cataleptic drug, provides pain relief without respiratory depression. Ketamine with the preservative benzethonium chloride 0.1 mg/ml was injected intrathecally into 4 baboons under Ketamine anaesthesia. A control group of 2 baboons received intrathecal saline. No assessment as to relief from experimental pain was possible, but all the baboons recovered normally from anaesthesia and were found moving about in their enclosures without gross evidence of neurological impairment. No adverse reactions were noted. One month after the intrathecal injection the baboons were sacrificed, and an autopsy was performed within 30 minutes. No macroscopic abnormally of the cord was noticed. Microscopic examination revealed oedema of a few nerve roots in all animals irrespective of whether ketamine or saline had been injected intrathecally. No other changes attributable to ketamine were seen, and its is therefore concluded that, in the doses given, intrathecally injected ketamine would seem to be safe.

Long-term antiplaque, anticalculus, and antigingivitis effects of benzethonium/polymer complex in beagle dogs

An electrostatic complex of 0.1% benzethonium chloride (BTC) plus 0.05% copolymer of methoxyethylene and maleic acid was evaluated in vitro for antibacterial effect. The complex by itself showed as much antibacterial activity as 0.1% BTC. The adsorption of 14C-BTC on saliva-coated hydroxyapatite disks and teeth in vitro was lower from the complex than the BTC solution, although in vivo activity was the same. The complex, BTC, and polymer solutions were evaluated in a 28-week study in 16 beagle dogs against plaque, gingivitis, and calculus formation. BTC and the complex significantly (alpha = 0.05) reduce plaque and gingivitis. There was no significant difference between the two active groups. BTC (0.1%) significantly increased calcified deposits at 22-28 wk compared to the water control group, while the complex and the polymer groups showed significantly (alpha = 0.05) less calculus. Thus, the complex was not only effective in vivo, but also significantly (alpha = 0.05) reduced tendencies of cationic antibacterials to induce calcified deposits on teeth.

[Differences in strains of tick-borne encephalitis virus with respect to the sensitivity of their hemagglutinins to the action of detergents]

Tick-borne encephalitis virus strains (TBE) differ in sensitivity of their hemagglutinating properties (HA) to the detergents: giamine 10-x triton X-100, bridge-58, sodium deoxycholate. These characteristics of different sensitivity to detergents were stable in virus passages in mice and apparently may be used as markers in comparative studies of different strains.

Long-term multicentre trial with TA-RO CAP, a new spermicidal product

326 healthy couples were selected to enter the trial of a new intravaginal contraceptive called the TA-RO CAP. The trial lasted three years. Clinical and laboratory examinations were performed periodically to determine the long-term effectiveness, tolerability and acceptance. Statistical evaluation of results was performed by life-table analysis.

Assessment of spermicides by a stripping technique against human spermatozoa

Fifty-two (52) compounds were tested for spermicidal activity by titration against human spermatozoa. The gradual decrease in mean sperm size was measured against increasing concentration of spermicide and the end-point was taken as the point at which all the peripheral cytoplasm had been removed and only the sperm core of nucleus and tail fibres remained. There were 14 compounds that produced this total effect. All were detergents, of various types, and the effect was purely physical. The most potent compounds caused complete stripping at 0.5-50 pmol/cell and most are already used in spermicidal preparations. A further 11 compounds, including sodium hypochlorite and some phenols, caused partial stripping, while 4 compounds caused sperm swelling. The test was not suitable for assessment of metabolic cell poisons.

Effects of local anesthetics on tactile sensitivity thresholds for cutaneous and mucous membranes

New, reliable, and precise methods for measuring absolute pressure sensitivity in mucous membranes and on intact skin are described. Studies were conducted to determine how local anesthetics (phenol and sodium phenolate and Benzocaine) affect tactile sensitivity thresholds in the oropharynx and on the intact skin of the volar surface of the forearms, ankles, knees, elbows, and dorsum of the hands. Gargling and expectorating a solution containing phenol had a significantly greater anesthetic effect on the mucous membranes of the oropharynx than spraying and swallowing, which, in turn, had a greater effect than drinking the solution. Compared with ethanol and petroleum jelly (Vaseline), the topical application of Benzocaine (0, .5, 1, 3, and 5% solutions in 100% ethanol) significantly increased the tactile sensory thresholds on the volar surface of the forearm. A highly significant loss of tactual sensitivity of the oropharynx was demonstrated in smokers.