Assessment of the skin sensitization potential of topical medicaments using the local lymph node assay: an interlaboratory evaluation

The murine local lymph node assay (LLNA) is a method for the predictive identification of chemicals that have a potential to cause skin sensitization. Activity is measured as a function of lymph node cell (LNC) proliferative responses stimulated by topical application of test chemicals. Those chemicals that induce a threefold or greater increase in LNC proliferation compared with concurrent vehicle controls are classified as skin sensitizers. In the present investigations we have evaluated further the reliability and accuracy of the LLNA. In the context of an international interlaboratory trial the sensitization potentials of six materials with a history of use in topical medicaments have been evaluated: benzoyl peroxide, hydroquinone, penicillin G, streptomycin sulfate, ethylenediamine dihydrochloride, and methyl salicylate. Each chemical was analyzed in the LLNA by all five laboratories. Either the standard LLNA protocol or minor modifications of it were used. Benzoyl peroxide and hydroquinone, both human contact allergens, elicited strong LLNA responses in each laboratory. Penicillin G, another material shown previously to cause allergic contact dermatitis in humans, was also positive in all laboratories. Streptomycin sulfate induced equivocal responses, in that this material provoked a positive LLNA response in only one of the five laboratories, and then only at the highest concentration tested. Ethylenediamine dihydrochloride dissolved in a 3:1 mixture of acetone with water, or in 4:1 acetone:olive oil (one laboratory), was uniformly negative. However, limited further testing with the free base of ethylene diamine yielded a positive LLNA response when applied in acetone:olive oil (AOO). Finally, methyl salicylate, a nonsensitizing skin irritant, was negative at all test concentrations in each laboratory. Collectively these data serve to confirm that the local lymph node assay is sufficiently robust to yield equivalent results when performed independently in separate laboratories and indicate also that the LLNA is of value in assessing the skin sensitization potential of topical medicaments.     

Is benzoquinone the prohapten in cross-sensitivity among aminobenzene compounds?

Cross-sensitivity in allergic contact dermatitis is a simultaneous allergy to 2 or more contact substances which have in common an antigenic determinant or a metabolic derivative. One of the most notable examples is the cross-sensitivity among aromatic compounds which may be oxidized in vivo to benzoquinone (BQ). However, it has also been hypothesized that the allergenicity and cross-sensitization are modulated by the chemical reactivity of the substituents in the para position. A serial dilution of BQ (from 1% to 0.1% in pet.) and three 1,4-substituted benzene derivatives (p-aminophenol, hydroquinone, metol), theoretically capable of conversion to BQ by oxidation, were patch tested in 22 p-phenylenediamine (PPD) positive patients and in 20 controls. The patients and a further 116 subjects with a positive history of sensitivity to 1 or more aminoaromatic compounds were also tested with some haptens of the para group (PPD, p-aminobenzoic acid, p-aminodiphenylamine, benzocaine, procaine chloride, p-toluenediamine sulfate). The results show that (i) the optimal patch test concentration for BQ was 0.2%, (ii) only 4 of the 22 patients allergic to PPD gave a clearly positive allergic reaction to BQ, and (iii) the number of positive reactions to the aromatic compounds was correlated with the presence of activating (-NH2, -OH, -CH3) and deactivating (-COOH) groups in the para position or, perhaps, with their effect on percutaneous penetration. The data suggest that BQ is not the only intermediate in the cross-sensitization of para group haptens. This is probably conditioned by other oxidation products and/or the chemical structure of the substituents in position 4 of the benzene ring.     

Treatment of acne with a combination clindamycin/benzoyl peroxide gel compared with clindamycin gel, benzoyl peroxide gel and vehicle gel: combined results of two double-blind investigations

BACKGROUND: It has previously been shown that a combination of erythromycin and benzoyl peroxide is superior to either ingredient when used alone in the treatment of acne. A clindamycin/benzoyl peroxide combination gel might have an advantage over erythromycin/benzoyl peroxide gel because the former does not require refrigeration after it is dispensed. OBJECTIVE: Our purpose was to determine the efficacy and safety of a combination clindamycin/benzoyl peroxide gel when compared with benzoyl peroxide, clindamycin, or vehicle gels. METHODS: In two double-blind, randomized, parallel, vehicle-controlled trials, patients were treated for 11 weeks with once-nightly application of one of the above preparations. Evaluations were performed at 2, 5, 8, and 11 weeks and included lesion counts and assessment of global responses and irritant effects. RESULTS: A total of 334 patients completed the study. All three active preparations were significantly superior to the vehicle in global improvement and in reducing inflammatory lesions and noninflammatory lesions. The combination gel was significantly superior to the two individual agents in global improvement and reduction of inflammatory lesions and also to the clindamycin gel in reducing noninflammatory lesions. There was no significant difference in tolerance to the active gels versus the vehicle gel. CONCLUSION: In the treatment of acne, topical clindamycin/benzoyl peroxide combination gel is well tolerated and superior to either individual ingredient.     

Cholangiopancreatography with magnetic resonance in the assessment of pancreatic ducts

The studies presented enable to evaluate the survival rate of the protozoa in contact with the studied polymers (foils: with polyethylene PE, polyvinyl chloride P-25, P-47, polyester E1 and irradiated collagen L7). It can also be established whether the change of certain morphodynamic parameters could be used to evaluate biological usefulness of plastics. Stereometric method and factor analysis were used in the studies. On the basis of the obtained data polyvinyl chloride P-47 was well assessed, while irradiated collagen L7 showed most negative features.     

Persulfate hair bleach reactions. Cutaneous and respiratory manifestations

Ammonium persulfate is widely used to "boost" peroxide hair bleaches. These persulfates can produce a variety of cutaneous and respiratory responses, including allergic eczematous contact dermatitis, irritant dermatitis, localized edema, generalized urticaria, rhinitis, asthma, and syncope. Some of these reactions appear to be truly allergic while others appear to be due to the release of histamine on a nonallergic basis. Patch tests may be performed with 2% to 5% aqueous solution of ammonium persulfate. Scratch tests may result in asthma and syncope. In some patients, merely rubbing a saturated solution of ammonium persulfate into the skin will evoke a large urticarial wheal. Hairdressers should be made aware that these ammonium persulfate hair bleach preparations may provoke severe reactions and should seek medical attention if the client complains of severe itching, tingling, a burning sensation, hives, dizziness, or weakness.     

Transport of Organic Contaminants in Geomembranes under Stress

The transport properties of aqueous solutions of benzene, dichloromethane, and trichloroethylene through extended polyvinyl chloride and high-density polyethylene geomembranes are investigated. It is found that extension enhances the permeation rates of the penetrants through polyvinyl chloride geomembranes, and the opposite effect is found in the case of high-density polyethylene. This difference in response is attributed to the type of structural change, which occurred as a result of the extension. The diffusivities of a mixture of the three organic solvents through the geomembranes are also determined.     

Intravascular Kaposi''s-like spindle cell proliferation of the capsular vessels of follicular-derived thyroid carcinomas

BACKGROUND: Occupational allergy to ornamental flowers is seldom reported. METHODS: We report a case of a 35-year-old male flower supplier who developed IgE-mediated allergic rhinoconjunctivitis with nasal polyps, and contact urticaria and dermatitis after handling Gypsophila paniculata. Dianthus caryophillus, and Lilium longiflorum. RESULTS: Studies revealed the presence of positive immediate skin prick tests. Rubbing tests were positive to G. paniculata and D. caryophillus. Serum specific IgE was detected against G. paniculata and L., longiflorum. In IgE immunoblot, two IgE-binding bands (15 and 17 kDa) were obtained against D. caryophillus, and two different bands (19 and 22 kDa) were visible against L. longiflorum. CONCLUSIONS: These findings suggest an IgE-mediated reaction as the mechanism responsible for the respiratory and cutaneous symptoms of the patient. No similar cases of allergy to D. caryophillus and L. longiflorum have been previously reported.     

Benzoyl peroxide stability in pharmaceutical gel preparations

The storage stability of benzoyl peroxide in the presence of both individual and combined pharmaceutical gel ingredients was investigated. Benzoyl peroxide was quite unstable in the presence of nucleophilic agents and certain acidic substances. At both 30 and 40 degrees storage temperatures, benzoyl peroxide was destroyed rapidly (within 1 month) in the presence of ethanol and acidic chelating agents. The substitution of acetone for ethanol, the elimination of chelating agents, and the addition of sodium hydroxide to gel preparations markedly reduced degradation.     

An ultrastructural study of the retention hyperkeratosis of experimentally induced comedones in rabbits: the effects of three comedolytics

The precise pathologic processes of comedo formation in acne are not well understood. Retention hyperkeratosis may play an important role. To evaluate the effects of three topical comedolytics, 20% azelaic acid, 0.1% tretinoin and 5% benzoyl peroxide, on the retention hyperkeratosis of experimentally induced comedones (EIC), an ultrastructural study was done. After formation of EIC with 50% oleic acid in paraffin oil on the external ears of rabbits, each comedolytic was applied for 4 weeks. Biopsies were taken every week and, using a Hitachi H-600 transmission electron microscope, morphologic observations were done in the upper portion of the follicular epithelium. In EIC, after application of each comedolytic, the markedly thinned horny layer was loosely adhered by extremely few desmosomes and desmosomal bodies. The number and size of tonofilaments and keratohyaline granules decreased, but the number of variable sized Odland bodies increased in the upper epidermis. These findings appeared 1 week after application of either azelaic acid or benzoyl peroxide, and 3 weeks after application of tretinoin. For the first 2 weeks of tretinoin application, EIC showed rather compact hyperkeratosis with more desmosomes and desmosomal bodies than before. Azelaic acid tretinoin and benzoyl peroxide increased the number of Odland bodies, and the horny cells became less adhesive. This lysis of retention hyperkeratosis resulted in comedolysis. During 4 weeks of treatment with these three comedolytics, only tretinoin normalized the keratinization process.     

Obstetric and gynaecological patients in an intensive care unit: a 1 year review

BACKGROUND: Pathophysiologic events in biological tissue are characterized by a shift of the electrical impedance spectra of the tissue under study. OBJECTIVE: To discuss studies on experimental skin reactions with an improved impedance spectrometer. The instrumentation is related to noninvasive techniques based on other physical principles. METHODS: The results from studies on patients with allergic contact reactions (n = 8), prick tests (n = 10), and irritant contact reactions (benzalkonium chloride [n = 14], sodium lauryl sulfate [n = 12], and nonanoic acid [n = 14]), and an appropriate number of controls are reviewed. RESULTS: Results show statistically significant changes of the impedance parameters when compared with relevant controls, at different types of experimental cutaneous reactions, both allergic and irritant type. Each reaction type had a specific impedance index pattern. CONCLUSIONS: Current data indicate that the improved impedance technique offers a possible noninvasive alternative for characterization and perhaps differentiation, not only between the skin responses induced by either an allergen or an irritant, but also a capability to distinguish responses induced by chemically different irritants. The assumption that the impedance method is capable to distinguish allergic from irritant contact reactions has not been proven yet in direct comparative studies.     

Abnormal vascular reactions in atopic dermatitis

Vascular reactions to mechanical stroking, topical application of nicotinic acid ester, and methacholine chloride were examined in both the normal and abnormal skin of 100 patients with atopic dermatitis and 20 patients with allergic contact dermatitis. White dermographism, nicotinic acid blanching, and delayed blanch with methacholine consistently occurred in areas of skin with eczematous change of patients with atopic dermatitis and those with allergic contact dermatitis. Normal skin of atopic patients did not show the abnormal vascular reactions. It is suggested that white dermographism, nicotinic acid blanching, and delayed blanch with methacholine seen in atopic dermatitis are secondary phenomena that give no definite information concerning the diagnosis of this disease.     

Delayed and immediate orofacial reactions following contact with rubber gloves during dental treatment

Allergic reactions during or after dental examination are uncommon. However, such reactions may be serious and distressing. Allergy to local anaesthetics and dental materials may be considered, but reactions to rubber in gloves worn by the dentist should be remembered. Two patients are reported who experienced symptoms following contact with rubber gloves worn by their dentists, with skin tests subsequently showing an allergic reaction to glove constituents, and in one case latex. With the increasing use of rubber gloves by dental and medical personnel, reactions in sensitised patients are likely to become more common. In patients with a history of symptoms related to dental work, it is important to remember delayed and immediate reactions to rubber.     

聚氯乙烯加工用稀土助剂研究进展

稀土在聚氯乙烯(Pvc)助剂上显示出了优良的性能，本文综述了PVc用稀土助剂，特别是稀土热稳定剂的开发、研究进展以及发展前景，并讨论了稀土热稳定剂的作用机制。确定稀土化合物是一种可以替代传统稳定剂的新型稳定剂，具有广阔的应用前景。     

Adverse effects of neuromuscular blockers and their antagonists

Among all the drugs used for general anaesthesia, neuromuscular blockers appear to play a prominent role in the incidence of severe adverse reactions. It now seems likely that most serious adverse drug reactions occurring during anaesthesia are immunological in type. The frequency of life-threatening anaphylactic or anaphylactoid reactions occurring during anaesthesia has been estimated to be between 1 in 1000 and 1 in 25,000 anaesthetic procedures, with the neuromuscular blockers being involved in 80% of cases. The mortality from such serious reactions is reported to be in the range of 3.4 to 6%. The highly immunogenic drug, suxamethonium chloride (succinylcholine), was found to be the most hazardous agent. Drug-specific immunoglobulin E antibodies to suxamethonium chloride and other neuromuscular blockers have been demonstrated. This sensitivity to neuromuscular blockers seems to be a long-lasting phenomenon. During anaesthesia, the clinical features of an allergic reaction are often masked. Tachycardia and circulatory collapse may be the only signs of an allergic reaction, and they are easily misdiagnosed. Bronchospasm is reported to be present in about 40% of cases. Successful management of these patients includes stabilisation during the acute reaction and avoidance of future reactions. The latter is based on the identification of the causative drug and potentially cross-reacting compounds. The use of suxamethonium chloride is associated with many other adverse effects, such as fasciculations, myalgia, potassium release, changes in the heart rate, increases in intragastric and intraocular pressures, and malignant hyperthermia. Because of the dangers of hyperkalaemic cardiac arrest after suxamethonium chloride administration in children with unrecognised muscular dystrophy, there have now been moves to limit the use of this drug in children. Although neuromuscular blockers are designed to specifically block nicotinic cholinergic receptors at the neuromuscular junction, many bind to muscarinic cholinergic receptors on ganglia and smooth muscle, and alter parasympathetically mediated heart rate and airway calibre. Most benzylisoquinolinium muscle relaxants can induce histamine release, especially when they are administered rapidly, which can lead to disturbances of cardiovascular function. In addition, nondepolarising neuromuscular blockers have been implicated in causing generalised weakness following their long term administration to patients on an intensive care unit. The problem with these adverse drug reactions is their unpredictable nature. Therefore, prompt recognition with appropriate therapy can help to improve the outcome.     

Isolation of three species of mites from house dust of atopic dermatitis patients in Qualyobia Governorate, Egypt

Dermatitis or inflammation of the skin caused by an outside agent, is a condition with many causes. It may result from direct irritation of the skin by a substances (chemical or insecticide) or it may be an allergic reaction to a particular substance that has been in contact with the skin as soap or detergent or insect urticating hairs; injected as insect saliva or faeces or sting or taken by mouth as food or drug. In general, treatment of dermatitis depends mainly upon the cause. In the present study, three species of mites were isolated from the dust collected from houses of atopic dermatitis patients. These mites were Dermatophagoides pteronyssinus, Ornithonyssus bacoti and Haemogamasus pontiger. The former species was the predominant one which is known to produce the most potent allergen. It was concluded that house dust mites are one of the aetiological factors of atopic dermatitis and that genera of mites other than Dermatophagoides may be considered as allergen in house dust mites.     

Skin sensitization thresholds: determination in predictive models

For many years, test methods for the prospective identification of skin sensitizing chemicals have been widely available. However, although these techniques have permitted the identification of the great majority of skin sensitizers, their use in assessing the relative potency of a particular chemical as a human contact allergen has not been well described. A primary reason for this is the inherent difficulty of such an exercise. A complex phenomenon involving interactions between the vehicle, the allergen, the skin and its inflammatory responses takes place during the induction and elicitation of sensitization. All these factors can have a profound effect on the threshold values determined for a skin sensitizer. Consequently, whether the assessment is conducted in humans or in animal models, a threshold concentration is always a function of the method of measurement as much as the potency of the allergen. Although an exhaustive review has not been carried out, this paper considers the attempts that have been made to assess relative potency by the measurement of dose-response relationships and the determination of induction and elicitation thresholds in both animal models and in humans. The latter has special relevance for regulatory toxicology and this matter is given particular attention in this article. Finally, recommendations are made: (a) that threshold concentrations for skin sensitizers should be determined on a case by case basis in relation to the likely mode of skin contact; (b) where the data are used in comparisons of skin sensitization potency, then there should be standardization of the method used for the determinations.     

Gas-liquid chromatographic headspace technique for determination of vinyl chloride in corn oil and three food-simulating solvents

A gas-liquid chromatographic headspace technique for the determination of vinyl chloride (VC) in corn oil, 50% ethanol, 3% acetic acid, and n-heptane is described. These food-simulating solvents and the corn oil are placed in septum-sealed bottles and heated to 90 degrees C, and aliquots of headspace vapor are injected into a gas-liquid chromatograph equipped with a flame ionization detector. VC may be quantitated at concentrations of 1 ppb or less. This technique was used to measure the migration of VC into corn oil and 50% ethanol from 2 unplasticized polyvinyl chloride sheets containing 0.28 and 0.44 ppm residual monomer.     

Microscopic Visualization Technique to Predict the Permeation of Organic Solvents through PVC Pipes in Water Distribution Systems

Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe.     

Mechanisms of resolution of allergic contact dermatitis

Photoallergic and allergic contact dermatitis are examples of type IV hypersensitivity reactions that involve T cell-mediated immune responses against haptens that come into contact with the skin. These two types of allergies differ in that for routine contact allergens, the hapten is usually a chemically reactive species that readily couples to host proteins; for photoallergic reactions, UV light (320 - 400 nm) is necessary to generate ("photoactivate") the chemically reactive hapten. From this point on, both photoallergic and allergic contact dermatitis are likely to proceed along the same pathways. For both types of cutaneous delayed-type hypersensitivity, there are naturally occurring mechanisms that terminate this type of T cell-mediated inflammation (tolerance induction). An important tolerance mechanism in the skin involves the induction of T-cell clonal anergy by "amateur" antigen-presenting cells such as keratinocytes. Advances in the understanding of the molecular pathways of T-cell activation and inactivation by antigen-presenting cells have identified critical signaling molecules such as B7/BB-1 antigen. The overexpression of these signaling molecules by the keratinocytes of transgenic mice disrupts the normal kinetics of resolution of murine contact hypersensitivity. These animals have prolonged contact hypersensitivity reactions that resemble some chronic dermatologic conditions in humans. This animal model may be a useful tool to better understand chronic allergic and photoallergic contact dermatitis.     

Investigation of substrate activation by 4-chlorobenzoyl-coenzyme A dehalogenase

4-Chlorobenzoyl-coenzyme A (4-CBA-CoA) dehalogenase catalyzes the hydrolysis of 4-CBA-CoA to 4-hydroxybenzoyl-coenzyme A (4-HBA-CoA), using the carboxylate side chain of aspartate 145 to displace the chloride from C(4) of the benzoyl ring. Previous UV-visible, Raman, and 13C NMR studies of enzyme-bound substrate analog or product ligand indicated that the environment of the enzyme active site induces a significant reorganization of the benzoyl ring pi-electrons. This observation was interpreted as evidence for electrophilic catalysis [viz. active-site-induced polarization of electron density away from the ring C(4)] [Taylor, K. L., Liu, R.-Q., Liang, P.-H., Price, J., Dunaway-Mariano, D., Tonge, P. J., Clarkson, J., & Carey, P. R. (1995) Biochemistry 34, 13881]. The recent crystal structure of the dehalogenase-4-HBA-CoA complex reveals two hydrogen bonds contributed to the benzoyl C=O by the backbone amide protons of Gly114 and Phe64 and a possible dipolar interaction with the positive pole of the 114-121 alpha-helix. Residues closely surrounding the benzoyl ring include W137, D145, W89, F64, F82, and H90. In the present study, the mutants D145A, H90Q, W137F, W89F, W89Y, F64L, F82L, and G114A were prepared to examine the effect of amino acid substitution on catalysis and on perturbation of the UV-visible spectral properties of the substrate benzoyl ring. Substitution of the two catalytic residues D145 and H90 inhibited catalysis but not ligand binding or the induction of the red shift in the benzoyl ring absorption. These two residues do not appear to contribute to substrate benzoyl ring binding or polarization. The F64L, F82L, W89F, and W137F mutants retained substantial catalytic activity and the ability to induce the red shift. The W89Y mutant, on the other hand, is inhibited in catalysis and ligand binding, suggesting that hydrophobicity more than packing may be critical for the benzoyl ring binding/activation. The G114A mutant was shown to be strongly inhibited in both substrate binding and activation, indicating that H-bonding and/or interaction with the dipole of the 114-121 alpha-helix may be crucial.