Successful treatment of Acanthamoeba keratitis by hexamidine.

Acanthamoeba keratitis remains very difficult to treat because of the lack of antiamoebic agents completely effective against cysts. Currently, the recommended treatment includes the use of topical neomycin sulfate, various imidazoles, and propamidine isethionate (Brolene) 0.1% eye drops, a compound of the diamidine family. In the present article, we describe the successful management of two patients with an Acanthamoeba keratitis, treated with hexamidine diisethionate (Desomedine) 0.1% eye drops, another diamidine derivative, which was found amoebicidal in vitro on the isolated Acanthamoeba strains. This is to our knowledge the first report on the amoebicidal effectiveness of hexamidine, simultaneously in vitro and in vivo.

Synthesis and pharmacological activities of some 2,3,4,5-tetrahydro[1,5]benzo[f]thiazepines.

In search of new biological active agents in the series of [1,5]benzothiazepines, some 2,3,4,5-tetrahydro-N-(5-morpholinopentanoyl)-[1,5]benzo[f] thiazepines were synthesized and examined in vitro for their calcium antagonist activity compared to the Diltiazem one.

[In vitro changes induced by phenylmercury nitrate on fungi causing keratitis. Scanning electron microscopy study]. / Modifications induites in vitro par le nitrate de phénylmercure sur des champignons responsables de kératites. Examen en microscopie électronique à balayage.

Antifungal activity of phenylmercury nitrate was studied on fungi from keratitis. Important deterioration and bursting were observed with 2 mg/100 ml phenylmercury nitrate concentration on Aspergillus flavus, Scedosporium and Candida albicans spores.

[Possibility of the survival of free-living amoebae which cause keratitis in decontamination solutions used for the maintenance of contact lenses]. / Possibilité de survie d'amibes libres responsables de kératites dans les solutions décontaminantes proposées pour l'entretien des lentilles de contact.

Because Acanthamoeba keratitis associated with contact lenses were described, several solutions used in stationary eye wash stations were contaminated by free-living amoebae. 0.9% sodium chloride rinsing solutions allowed cyst and trophozoite growth and only one solution for decontamination using hydrogen peroxide led to rapid elimination of cysts and trophozoites. Antiseptic solutions containing ammonium derivatives or chlorhexidine killed only trophozoites. Because of the constant contamination of tap water with Acanthamoeba cysts resistant to chlorine, the prevention of amoebic keratitis in wearers of contact lenses needs: use of sterile solutions for decontamination or rinsing, choice, if possible, of oxidizing solutions, suppression of tap water for rinsing.

[The efficacy of water ozonation on the inactivation of oocysts of Cryptosporidium]. / Efficacité de l'ozonation des eaux sur l'inactivation des oocystes de Cryptosporidium.

Cryptosporidium oocysts are currently found in surface waters. Their incomplete removal by sand filtration and their high resistance to chlorinated disinfectants make possible waterborne cryptosporidiosis outbreaks after drinking treated water. Because ozone is an alternative to chlorine for final drinking water disinfection the aim of our study was to determine the ozonation conditions able to eliminate the infectivity of oocysts. Feces from horses naturally infected by C. parvum were mixed with distilled water. The obtained suspension was clarified by passing through a graded series of four sieves (pore sizes, 315, 200, 125 and 63 microns). The clarified suspension was decontaminated by adding a 10% sodium hypochlorite solution. After a 10 minute contact time at room temperature, the chlorine residual was neutralised by the exactly requisite volume of a 0.01 N sodium thiosulfate solution. Oocysts in the suspension were purified by centrifugation and washing of pellets in distilled water. Oocysts in the finally obtained suspension were numerated by counting in a Malassez haemocytometer. Ozonated water containing dissolved ozone residuals ranging from 0.44 mg/l to 1.09 mg/l were inoculated with a number of oocysts ranging from 1.10(6) to 1.10(8). Contact times with ozone were 4.6 or 8 minutes. After destroying the ozone residual by sodium thiosulfate, ozonated oocysts were administered by oral route to male Sprague-Dawley rats weighing between 180 to 200 g and beforehand immunosuppressed by a regimen of 25 mg hydrocortisone acetate subcutaneously twice a week, 5 weeks before and 3 weeks after Cryptosporidium challenge. Oocyst shedding was daily controlled by phase contrast microscoy in smears of fecal suspension mixed with carbolfuchsine solution.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of acetylcholine on the heart ventricle of the goldfish Carassius auratus, Teleosts, Cyprinidae. Modification of the response as a function of temperature]. / Activité de l'acétylcholine sur le ventricule du coeur de poisson rouge Carassius auratus, Téléostéen, Cyprinidé. Modification de la réponse en fonction de la température.

Acetylcholine (Ach) is more efficient on the red fish heart at 14 degrees C than at 5 degrees C or 8 degrees C. It does not probably exist a cholinesterasic system and high concentrations of Ach are to be used to obtain significant variations of the heart frequency. Ach does not appear as a physiological mediator and temperature seems to be an essential factor in heart regulation and modulation of the pharmacological effects of eventual mediators. A thermal adaptation exists but the fast increase of the temperature, in the presence of Ach, results in heart blocage, whose contractions reappear spontanously during cooling. This is at the present time no valuable hypothesis could be made to explain this phenomenon.

[Comparative in vitro activity of chlorine and bromine on the cysts of free-living amoebae]. / Activité comparée in vitro du chlore et du brome sur les kystes d'amibes libres.

A continuous flow type apparatus is used for investigation of the chlorine and bromide activity in vitro on the cysts of two free-living amoeba strains : Naegleria gruberi and Acanthamoeba polyphaga. The Naegleria cysts are sensitive more to chlorine than to bromine ; those of Acanthamoeba are perfectly resistant to these disinfectants in the limit of the available concentrations in swimming-pools. The sensibility to these disinfectants stays the same at 25 degrees C and 35 degrees C.

Sequence-selective binding to DNA of bis(amidinophenoxy)alkanes related to propamidine and pentamidine.

The DNA sequences targeted by a complete homologous series of aromatic diamidines have been determined at single-nucleotide resolution via protection from cutting by the endonucleases DNase I, DNase II and micrococcal nuclease. Propamidine, pentamidine and to a lesser extent hexamidine bind selectively to nucleotide sequences composed of at least four consecutive A-T base pairs. In contrast, the binding to DNA of butamidine, heptamidine, octamidine and nonamidine is poorly sequence-selective. Sequences composed of only three consecutive A-T base pairs do not afford a potential binding site for propamidine or the longer homologues, and none of the drugs tolerate the presence of a G-C base pair within the binding site. Experiments with DNA molecules containing inosine in place of guanosine and 2,6-diaminopurine in place of adenine reveal that the lack of binding of propamidine to GC-containing sites is attributable to an obstructive effect of the exocyclic 2-amino group of guanosine. The present data support the view that the local conformation of the double helix (in particular the width of the minor groove) plays a dominant role in the binding reaction and that the capacity of diamidines to recognize AT-rich sequences selectively varies considerably depending on the length of the alkyl chain. The evidence indicates that binding to AT-tracts in DNA must play a role in the biological activity of these diamidines, but there is no simple correlation between binding and pharmacological efficacy.

Amoebicidal efficiencies of various diamidines against two strains of Acanthamoeba polyphaga.

The first medical cure of Acanthamoeba keratitis was obtained by use of propamidine isethionate. Since then, it has been the basic drug recommended for use in treatment. Because some Acanthamoeba strains have been reported to be resistant to propamidine and propamidine was found to be only weakly cysticidal, superior homologs such as butamidine, pentamidine, hexamidine, heptamidine, octamidine, and nonamidine were tested for their amoebicidal effects on two Acanthamoeba strains isolated from patients with keratitis. Trophozoicidal and cysticidal efficiencies were found to be increased from propamidine to nonamidine; i.e., when the alkyl chain connecting the two benzene rings in their molecular structures was elongated, in comparison with propamidine, hexamidine and octamidine were the most amoebicidal molecules. As a result of these data, a kinetic study carried out on propamidine, hexamidine, and octamidine demonstrated that the amoebicidal effects resulted from two events: the diffusion of molecules through the plasma membrane or the double wall of trophozoites or cysts, respectively, and the lethal effects of molecules on amoebic protoplasm. The diffusion kinetics were increased when the alkyl chain was elongated, i.e., with an increase in the lipophilic properties of molecules. In contrast, the lethal effect kinetics were found to be unchanged by this elongation, indicating that they originated from the cationic surface-active properties induced by the protonated amidine groups attached to each benzene ring, which themselves remained unchanged from one molecule to the other. These results strongly advocate the immediate replacement of propamidine by hexamidine in the medical treatment of Acanthamoeba keratitis; in France, 0.1% hexamidine eyedrops are available (Desomedine). The results also advocate clinical investigations on the efficiency and toxicity of octamidine, which appears to be the most amoebicidal diamidine in vitro.

Parasitic hazard with sewage sludge applied to land.

A modification of the FAUST technique allowed a highly regular recovery of Taenia saginata eggs from sewage sludge, as well as their quantification. Despite the low viability (8%) noted, the viable T. saginata egg level remains high (20.10(6)/ha) and offers a serious risk for cattle even after a 3-week "no-grazing" period.

Light-dependent effects of alpha-terthienyl in eggs, larvae, and pupae of mosquitoAedes aegypti.

Alpha-terthienyl is toxic toAedes aegypti larvae in the dark, but its activity is much enhanced in the presence of ultraviolet light. The development of first-instar larvae treated with alpha-terthienyl and ultraviolet light was followed until the emergence of adults. The LC50 value for first instars was about 0.002 ppm. Practically all the larvae which survived 24 hr reached adulthood. Fourth-instar larvae were also sensitive to photochemical treatment. When their development into adults was followed, the LC50 value was 0.45 ppm. Contrary to earlier reports, alpha-terthienyl was also phototoxic in pupae, but not when the adults were about to emerge. The LC50 value was ca. 0.06 ppm for pupae which were 1 or 2 days old. This is the first example where the activity of a photoinsecticide has been demonstrated in pupae. Alpha-terthienyl did not affect the hatching of eggs.

Amide derivatives with H1-antihistaminic effect.

The synthesis and the structure-activity correlation of a series of N-aminoalkylacetamides as H1-antihistaminic agents have been carried out. The compounds were tested in vitro by measurement of the inhibition of histamine-induced contractions on isolated guinea pig ileum; the results are expressed as pA2.

In vivo inhibition of nitric oxide synthase by bisisothiouronium and bisguanidinium salts.

The ability of two S,S'-(alkane-1,omega-diyl) bisisothiouronium dibromides, three N,N'-(alkane-1, omega-diyl) bis guanidinium dinitrates and N,N'-bis (3-guanidinopropyl)piperazine dinitrate to inhibit constitutive (i.e. endothelial and neuronal forms) and inducible forms of nitric oxide synthases has been evaluated in vivo. These compounds, synthesized by two of us (J. C. L. and C. S.), have been tested in vivo; they were administered simultaneously with an irritant (carrageenan lambda) into the pleural cavity. The amount of nitrites collected 0.5 and 7 hours after this injection can be considered as an indicator of nitric oxide (NO) production. According to previous data, the first harvesting time can be related to activation of constitutive NO synthases and the second to activation of inducible NO synthases. These substances significantly inhibited nitrite production as did 2-methyl-2-thiopseudourea sulphate, previously described as a potent inhibitor of NO synthases and considered as the reference compound. The inhibiting effect varied according to the chemical structure of the compounds. Results were significantly different from controls at 0.5 h only with the S,S'-(octane-1,8-diyl) bisisothiouronium dibromide and the S,S'-(nonane-1,9-diyl) bisisothiouronium dibromide at the highest concentration, N,N'-(heptane-1,7-diyl) bisguanidinium dinitrate and N,N'-bis (3-guanidinopropyl)piperazine dinitrate. At 7 h, all the results were significantly different from controls, with a major effect observed with N,N'-(heptane-1,7-diyl) bisguanidinium dinitrate. The most active substances exerted similar effects to the reference substance.