Immunomodulating and antiviral activities of the imidazoquinoline S-28463.

Recently, a new class of immunomodulating agents, represented by the molecules imiquimod and R-842, has demonstrated potent antiviral and antitumor activities in animal models. In this study, another representative of this class, S-28463 (4-amino-2-ethoxymethyl-alpha,alpha-dimethyl-1H-imidazo[4,5-c]quinoline- 1- ethanol) was evaluated for its immunomodulating and antiviral activities. S-28463 induced IFN and other cytokines in vivo in mice, rats, monkeys and in vitro in human peripheral blood mononuclear cell cultures. S-28463 showed potent antiviral activity against herpes simplex virus-challenged guinea pigs when given subcutaneously, dermally, or intravaginally 24 h before infection. Antiviral activity in guinea pigs correlated with the induction of serum 2',5'-oligoadenylate synthetase activity. Thus, S-28463, like the other imidazoquinolines, demonstrates potent antiviral and immunomodulating effects in a number of models.

Long circulating liposomes encapsulating organophosphorus acid anhydrolase in diisopropylfluorophosphate antagonism.

These studies are focused on antagonizing organophosphorous (OP) intoxications by a new conceptual approach using recombinant enzymes encapsulated within sterically stabilized liposomes to enhance diisopropylfluorophosphate (DFP) degradation. The OP hydrolyzing enzyme, organophosphorous acid anhydrolase (OPAA), encapsulated within the liposomes, was employed either alone or in combination with pralidoxime (2-PAM) and/or atropine. The recombinant OPAA enzyme, from the ALTEROMONAS: strain JD6, has high substrate specificity toward a wide range of OP compounds, e.g., DFP, soman, and sarin. The rate of DFP hydrolysis by liposomes containing OPAA (SL)* was measured by determining the changes in fluoride-ion concentration using a fluoride ion-selective electrode. This enzyme carrier system serves as a biodegradable protective environment for the OP-metabolizing enzyme (OPAA), resulting in an enhanced antidotal protection against the lethal effects of DFP. Free OPAA alone showed some antidotal protection; however, the protection with 2-PAM and/or atropine was greatly enhanced when combined with (SL)*.

Neodymium:YAG laser interaction with Alcon IOGEL hydrogel intraocular lenses: an in vitro toxicity assay.

The objective of this study was to determine the potential toxicity generated by the interaction of the Nd:YAG laser and Alcon IOGEL intraocular hydrogel lens material. The IOGEL lens is composed of poly 2-hydroxyethylmethacrylate, containing 38% water, previously shown to be highly biocompatible in a wide range of tissue culture and implantation experiments. In this study, intraocular lenses (IOLs) immersed in serum-free cell culture medium were purposely exposed to exaggerated doses of laser energy to cause extensive damage. An IOLAB polymethylmethacrylate (PMMA) lens served as a control lens material. The resultant solutions were assayed for cytotoxicity in a bioassay system using fourth passage human corneal endothelial cells. No cytotoxicity was seen in the bioassay for the IOGEL hydrogel IOLs or the PMMA control IOL at any laser range/dosage tested over a 72-hour incubation period. Hydrogel lenses exhibited decreasing yellowing with decreasing energy levels, and no lens discoloration was apparent at the lowest level of irradiation, 5 mJ/50 laser bursts; the PMMA control lens exhibited moderate yellowing at 15 mJ/50 bursts. Lens marking was moderate for all IOGEL IOLs; the PMMA lens marking was severe at the power level tested.

A new approach to the safety assessment of pharmaceutical excipients. The Safety Committee of the International Pharmaceutical Excipients Council.

This article presents a set of proposed guidelines for the safety assessment of new pharmaceutical excipients. These guidelines were developed by the Safety Committee of the International Pharmaceutical Excipients Council and represent a new, scientifically based approach to establishing conditions for the safe use of proposed pharmaceutical excipients utilizing various routes of human exposure. They are based upon the best currently available toxicological science and have taken the deliberations of the International Conference on Harmonization into consideration. These guidelines were developed because there are no regulatory agency guidelines currently available which specifically address the toxicological testing of a material intended for use as an excipient in pharmaceutical preparations. Only materials which have been previously permitted for use in a pharmaceutical preparation or which have been permitted for use in foods may be considered safe under current practices. If implemented, these guidelines should expedite the review of a proposed new excipient by regulatory agencies.

The mechanism of cyanide intoxication and its antagonism.

The mechanism of cyanide intoxication has been attributed to the inhibition of cytochrome oxidase, thereby decreasing the tissue utilization of oxygen. One mechanism of cyanide antagonism is by sequestering cyanide with methaemoglobin to form cyanmethaemoglobin and another mechanism is detoxifying with a sulphur donor to thiocyanate. Questions have been raised with regard to these classical mechanisms. Oxygen with nitrite-thiosulphate antagonizes the lethal effects of cyanide. Theoretically, increased oxygen should serve no useful purpose, as it is the tissue utilization of oxygen which is inhibited. In the nitrite-thiosulphate antidotal combination, the proposal is made that the predominate antidotal action of nitrite is a vasogenic action, rather than methaemoglobin formation, because when methaemoglobin formation is inhibited by methylene blue the protective action of sodium nitrite persists. This suggests that methaemoglobin formation plays only a small part, if any, in the therapeutic antagonism of the lethal effects of cyanide. The roles and implications of sodium thiosulphate and non-rhodanese substrates in the detoxification mechanism are compared. Lastly, a new approach to cyanide antagonism has been initiated which involves the erythrocyte encapsulation of thiosulphate and sulphurtransferase as an antidote and prophylaxis against cyanide.

Recent perspectives on the toxicodynamic basis of cyanide antagonism.

The mechanism of action of nitrite-thiosulfate (Chen et al., 1933a ,b; Hug , 1933) in the antagonism of the lethal effects of cyanide is much more complex than proposed 50 years ago. Some of the recent findings concerning the mechanism of nitrite action have conceptual theoretical and practical significance, as the development of newer cyanide antagonists are dependent on the elucidation of the basic mechanism of antidotal action. There are preliminary evidence which suggest a vasogenic action rather than methemoglobin formation is the primary action of nitrite, as a cyanide antagonist. Various vasogenic compounds have been uncovered and they may play an important role in the future development of a new class of cyanide antagonists. Also recent development in thiol detoxication of cyanide suggest that rhodanese may play a more complex role. The detoxification of cyanide may be viewed from a considerably more complex perspective with the elucidation of recent mechanisms. It also may provide a newer conceptual basis for a more rational development of future compounds to antagonize the lethal effects of cyanide.

Antagonism of paraoxon intoxication by recombinant phosphotriesterase encapsulated within sterically stabilized liposomes.

This investigation effort is focused on increasing organophosphate (OP) degradation by phosphotriesterase to antagonize OP intoxication. For these studies, sterically stabilized liposomes encapsulating recombinant phosphotriesterase were employed. This enzyme was obtained from Flavobacterium sp. and was expressed in Escherichia coli. It has a broad substrate specificity, which includes parathion, paraoxon, soman, sarin, diisopropylfluorophosphate, and other organophosphorous compounds. Paraoxon is rapidly hydrolyzed by phosphotriesterase to the less toxic 4-nitrophenol and diethylphosphate. This enzyme was isolated and purified over 1600-fold and subsequently encapsulated within sterically stabilized liposomes (SL). The properties of this encapsulated phosphotriesterase were investigated. When these liposomes containing phosphotriesterase were incubated with paraoxon, it readily degraded the paraoxon. Hydrolysis of paraoxon did not occur when these sterically stabilized liposomes contained no phosphotriesterase. These sterically stabilized liposomes (SL) containing phosphotriesterases (SL)* were employed as a carrier model to antagonize the toxic effects of paraoxon by hydrolyzing it to the less toxic 4-nitrophenol and diethylphosphate. This enzyme-SL complex (SL)* was administered intravenously to mice either alone or in combination with pralidoxime (2-PAM) and/or atropine intraperitoneally. These results indicate that this carrier model system provides a striking enhanced protective effects against the lethal effects of paraoxon. Moreover when these carrier liposomes were administered with 2-PAM and/or atropine, a dramatic enhanced protection was observed.