Comparative analysis of skin surface lipids of the labia majora, inner thigh, and forearm

The purpose of this study was to develop a procedure for the collection of skin surface corneocyte lipids from the semioccluded and intimate regions of the labia majora and inner thigh of women, to evaluate the polar and nonpolar composition, and to compare the distribution of the lipid classes relative to a collection of lipids from the forearm. The solvent system of ethanol-cyclohexane was well tolerated across all sites. While the yield of polar lipids was similar across all 3 sites, there were only marginal differences in the relative abundance of ceramides, a class of lipids closely associated with skin barrier activity. The yield of neutral lipids was significantly less for the labia majora and was associated with a reduced yield of wax esters, triglycerides and free fatty acids, likely associated with reduced sebaceous gland activity. Factors that may contribute to an inferior skin barrier activity for the labia majora are discussed and suggest a possible deficiency of ω-6 fatty acid linked to the sphingosine base of ceramide EOS.     

尖锐湿疣80例误诊分析

目的探讨尖锐湿疣（CA）与外阴、阴道内壁、肛周有增生物的其他常见皮肤疾病的鉴别以及误诊原因。方法回顾性分析我院2006年9月至2011年9月问有80例误诊为CA。男32例,女48例,年龄16～70岁,平均28．5岁。皮损分布：包皮5例、龟头后缘近冠状沟处20例、大阴唇12例、小阴唇（内、外）13例、阴道前庭8例、阴阜5例、阴道内壁5例、肛周12例。病例情况：外阴及肛周有增生物73例、有白带异常6例（阴道检查中发现可疑增生物）、有不洁性交史55例。误诊情况：外阴皮内痣3例（3．75％）;阴道正常皱壁5例（6．25％）;鲍温样丘疹病5例（6．25％）;传染性软疣7例（8．75％）;扁平湿疣9例（11．25％）;皮赘10例（12．50％）;外阴假性湿疣20例（25．00％）;阴茎珍珠状丘疹21例（26．25％）。结果80例中有49例无需治疗,31例按相应病因治疗全部好转或治愈。结论尖锐湿疣的诊断应慎重对待,勿草率诊断,加强皮肤性病专业知识的培训,学习掌握尖锐湿疣的鉴别诊断,提高诊疗水平。     

Regional variations in skin barrier function and cutaneous irritation due to iontophoresis in human subjects.

The effect of saline iontophoresis on skin barrier function and irritation was investigated on three body sites (abdomen, chest and upper arm) in order to select an appropriate site for iontophoretic delivery of drugs. Thirty healthy human volunteers were recruited according to specific entry criteria. Ten subjects, five males and five females, were assigned to each body site group. Skin barrier function and irritation was examined after 4 h of saline iontophoresis at a current density of 0.2 mA/cm(2) on a 6.5 cm(2) area in terms of the measured responses: transepidermal water loss (TEWL), skin capacitance, skin temperature and visual scores. Alterations in TEWL due to iontophoresis were not observed in the upper arm and chest; however, changes in TEWL at the abdomen were observed and returned to baseline 2 h after patch removal. Similarly, changes in capacitance due to iontophoresis returned to baseline (P>0.05) at the three body sites 2 h after patch removal except under the anode at the abdomen (P<0.05). There was a significant increase in skin temperature due to iontophoresis at the anode and the cathode (P<0.05) at the upper arm. Edema was not observed. At patch removal, the erythema score was significantly (P<0.001) elevated in comparison to baseline at the three body sites. Erythema resolved within 24 h except at the chest under the anode, where the erythema score was still higher (P<0.01) than the baseline. Papules appeared in five subjects at the active anode site on the chest. In three of the subjects, these papules did not resolve until 24 h post patch removal. Thus, there was regional variation in the function of the skin and irritation due to iontophoresis. Irritation was greater at the chest than at the abdomen or upper arm.     

Cutaneous and sensory effects of feminine hygiene pads among women with recent genital infection

We compared the skin compatibility of two menstrual pad technologies in a single-center, parallel, randomized, examiner-blinded study involving adult women. This report presents the results of a subset of 10 participants who had a genital infection within 12 months prior to the start of the study. In a blinded fashion, participants were randomized to receive one of the two pads for use over two menstrual periods. Participants' skin erythema was graded 24-48 hours following cessation of menstrual flow and on day 14 of each menstrual cycle. Participants subjectively reported any sensory effects. Vulvar erythema scores for the mons pubis, labia majora, labia minora, perineum, buttocks, left medial thigh, and right medial thigh assessed after both menstrual cycles were not statistically different between groups or between the two different products. A low incidence of itching and burning occurred in both groups without statistical significance; none of the participants experienced a recurrent or new genital infection. These preliminary results show that participants with recent genital infections included in clinical studies do not exhibit greater vulvar erythema or sensory effects than participants without recent genital infection. The study showed that the safety profile of the products tested remained acceptable in women with recent genital infection.     

In vitro and in vivo comparison of dermal irritancy of jet fuel exposure using EpiDerm (EPI-200) cultured human skin and hairless rats

The purpose of this study was to evaluate an in vitro EpiDerm human skin model (EPI-200) to study the irritation potential of jet fuels (JP-8 and JP-8+100). Parallel in vivo studies on hairless rats on the dermal irritancy of jet fuels were also conducted. Cytokines are an important part of an irritation and inflammatory cascade, which are expressed in upon dermal exposures of irritant chemicals even when there are no obvious visible marks of irritation on the skin. We have chosen two primary cytokines (IL-1alpha and TNF-1alpha) as markers of irritation response of jet fuels. Initially, the EPI-200 was treated with different quantities of JP-8 and JP-8+100 to determine quantities which did not cause significant cytotoxicity, as monitored using the MTT assay and paraffin embedded histological cross-sections. Volumes of 2.5-50 microl/tissue (approximately 4.0-78 microl/cm2) of JP-8 and JP-8+100 showed a dose dependent loss of tissue viability and morphological alterations of the tissue. At a quantity of 1.25 microl/tissue (approximately 2.0 microl/cm2), no significant change in tissue viability or morphology was observed for exposure time extending to 48 h. Nonetheless, this dose induced significant increase in IL-1alpha and TNF-alpha release versus non-treated controls after 24 and 48 h. In addition, IL-1alpha release for JP-8+100 was significantly higher than that observed for JP-8, but TNF-alpha release after 48 h exposure to these two jet fuels was the same. These findings parallel in vivo studies on hairless rats, which indicated higher irritation levels due to JP-8+100 versus JP-8. In vivo, transepidermal water loss (TEWL) and IL-1alpha expression levels followed the order JP-8+100 > JP-8 > control. Further, in vivo TNF-alpha levels for JP-8 and JP-8+100 were also elevated but not significantly different from one another. In aggregate, these findings indicate that EPI-200 tissue model can be utilized as an alternative to the use of animals in evaluating dermal irritation.     

In vitro penetration and subchronic toxicity of alpha-methyl-1,3-benzodioxole-5-propionaldehyde.

alpha-Methyl-1,3-benzodioxole-5-propionaldehyde (methyl-3,4-methylene-dioxy-hydrocinnamic Aldehyde, MMDHCA) is a widely used commercially available fragrance material. Because of the wide range of product availability, there is dermal exposure associated with its use. The objective of this study was to determine the in vitro human skin absorption of (14)C MMDHCA and subchronic toxicity of the material. Twenty mL of a 1% solution of radiolabeled MMDHCA in ethanol was applied to the surface of epidermal membranes isolated from full thickness human skin samples and placed in diffusion cells. Samples of the receptor fluid (50% ethanol/water) were harvested at 2, 8, 24, and 48 h and analyzed by liquid scintillation chromatography to assess dermal absorption. At 24 and 48 h, respectively, 42% and 50% of the applied dose of MMDHCA had permeated the human skin in vitro. Only 67% of the applied dose was recovered by 48 h. For the subchronic toxicity, MMDHCA was applied dermally once daily to male and female Sprague-Dawley rats (15/sex/group) at 50, 150, or 300 mg/kg/day (0.043, 0.129, or 0.259 mL/kg/day applied neat to 5 cm(2) dorsal skin) for at least 90 consecutive days. A control group (15/sex) was given vehicle (reverse osmosis water) at 0.259 mL/kg/day for a similar duration. Rats were necropsied at the end of treatment (10/sex/group) or following a 4-week recovery period (5/sex/group). The following parameters were evaluated: dermal irritation, estrous cycle, ophthalmologic examinations, body weight, feed consumption, hematology, blood coagulation, serum chemistry, organ weights, macroscopic and histopathologic examinations, and male reproductive assessment. No test article-related mortalities or effects on, estrous cycles, ophthalmic exams, mean body weights, mean body weight change, feed consumption, absolute or relative organ weights, macroscopic observations, or male reproductive morphology/function were observed. MMDHCA-related dermal irritation was observed across all dose levels with increased incidence and severity at 300 mg/kg/day. Dermal irritation that initially ranged from slight to marked improved to slight or resolved completely during the recovery phase. Based on the findings in this study, it can be concluded that (1) MMDHCA exhibits moderately high human skin permeation; (2) the NOEL for dermal irritation is below 50mg/kg/day when applied undiluted to 5 cm(2) dorsal skin and (3) the NOEL for systemic toxicity is greater than 300 mg/kg/day. During the 4-week recovery period of the 90-day study, the animals had largely recovered from MMDHCA induced dermal irritation and the associated microscopic findings.     

An in vitro model for detecting skin irritants: methyl green-pyronine staining of human skin explant cultures.

We evaluated the potential of human organotypic skin explant cultures (hOSECs) for screening skin irritants. Test chemicals were applied to the epidermis of the skin explants which were incubated for 4, 24 or 48 h in tissue culture medium. A decrease in epidermal RNA staining, visualised in frozen sections using a modified methyl-green pyronine (MGP) staining procedure, was used as a marker of irritancy. A decrease in epidermal RNA after a 4-, 24- or 48-h exposure to a certain concentration of a test chemical equated to a MGP score of 3, 2 or 1, respectively. The MGP score was 0 if there was no keratinocyte cytotoxicity after a 48-h exposure. A minimum of three donors were used per chemical and the average MGP score was used to classify the chemical as irritant or not. Chemicals with an average MGP score > or =1.5 were classified as irritants (R38), at that concentration. Chemicals with a MGP score <1.5 were not classified (NC), at that concentration. The results obtained using human skin in vitro were compared with published data obtained using cultured porcine skin, the cutaneous Draize test (from this point referred to as the "rabbit skin irritation test") and volunteer studies. There was an excellent correlation between the classification of a chemical, as R38 or NC, based on hOSEC and results of volunteer studies. The hOSEC model predicted perfectly the irritation hazard of the 22 chemicals for which volunteer data were available. The porcine OSEC correctly predicted the classification of 21 of 22 (95%) chemicals and the rabbit skin irritation test correctly predicted the classification of 14 of 15 chemicals (93%) for which data were available. In conclusion, MGP staining of human skin explant cultures can be used to predicted human skin irritancy in vivo. In addition, the data validate the use of porcine skin as an alternative to human skin for screening for dermal irritants in vitro.     

Effect of jet fuels on the skin morphology and irritation in hairless rats

Jet A and JP-8 are the major jet fuels used in civilian and military (US Air Force) flights, respectively. JP-8+100 is a new jet fuel recently introduced by US Air Force in some of its locations. The purpose of this study was to investigate the effects of dermal exposure of jet fuels (Jet A, JP-8, and JP-8+100) on the skin morphology, barrier function, moisture content, blood flow, and skin irritation (erythema and edema) in hairless rats. Jet fuels were applied by both occlusive and unocclusive methods. The skin of treated and control (untreated) sites were excised and analyzed by magnetic resonance imaging (MRI) (500 MHz, 11.7 Tesla). Unocclusive application of JP-8, Jet A, and JP-8+100 increased the transepidermal water loss (TEWL) gradually and the values at 120 h were significantly greater than the baseline value (P<0.05). Both occlusive and unocclusive application of jet fuels decreased the skin moisture content significantly (P<0.05). Unocclusive application of JP-8, Jet A, and JP-8+100 increased the skin blood flow, though the values returned to the baseline levels within 24 h. Occlusive application of jet fuels (8 h/day for 2 days) caused a substantial increase in the skin blood flow and the values at 48 h were about 6-fold greater than the baseline value. Occlusive application of jet fuels caused a moderate to severe erythema and a moderate edema. MRI was used to obtain proton images and water self-diffusion maps of hairless rat skin exposed to jet fuel. Exposure to JP-8 showed the largest difference from the control with regards to visual observations of the stratum corneum and hair follicles, while JP-8+100 appeared to affect the hair follicle region. The results of the present study demonstrate that exposure to jet fuels can disrupt the skin barrier function, cause skin irritation, and alter the skin structure (stratum corneum and viable epidermis) and MRI can be used as a tool to investigate the alterations in the skin morphology after exposure to toxic chemicals.     

Skin permeation enhancement effect and skin irritation of saturated fatty alcohols

Though the skin permeation enhancement effect of chemical penetration enhancers has been studied extensively, their skin irritation potential has not been adequately investigated. The objective of this study was to evaluate the skin permeation enhancement effect and skin irritation of saturated fatty alcohols using melatonin as a model compound. A saturated solution of melatonin in a mixture of water and ethanol (40:60) containing 5% w/v of saturated fatty alcohol was used in the skin permeation studies using Franz diffusion cells. For skin irritation studies, 230 microl of fatty alcohol solution was applied on the dorsal surface of the hairless rats using Hill top chamber. The skin irritation was evaluated by visual scoring method and bioengineering methods such as measurement of transepidermal water loss (TEWL) and skin blood flow. The flux of melatonin across hairless rat skin was found to be dependent on the carbon chain length of the fatty alcohols, with decanol showing the maximum permeation of melatonin. All fatty alcohols increased the TEWL and skin blood flow significantly compared with the vehicle. The fatty alcohols (decanol, undecanol and lauryl alcohol), which showed greater permeation of melatonin, also produced greater TEWL, skin blood flow and erythema. Tridecanol and myristyl alcohol showed lower permeation enhancement effect but caused greater skin irritation. Octanol and nonanol may be the most useful enhancers for the transdermal delivery of melatonin considering their lower skin irritation and a reasonably good permeation enhancement effect. However, further studies are needed to ascertain their safety as skin penetration enhancers. Skin permeation and skin irritation in experimental animals such as rats are generally higher compared with human skin. Further studies in human volunteers using fatty alcohols at the concentrations of 5% or lower may provide useful information on the utility of these fatty alcohols as permeation enhancers.     

Dermatotoxicity of cutting fluid mixtures:in vitro and in vivo studies

Cutting fluids are widely used in the metal-machining industry to lubricate and reduce heat generation when metals are cut by a metal-cutting tool. These cutting fluids have caused occupational irritant contact dermatitis (OICD), and many of the additives used in these cutting fluid mixtures are thought to be responsible for OICD in workers. The purpose of this study was to assess single or various combinations of these additives in initiating the OICD response following an acute 8-hour exposure in porcine skin in vivo and in vitro using the isolated perfused porcine skin flap (IPPSF) and human epidermal keratinocytes (HEK). Pigs (n = 4) were exposed to 5% mineral oil (MO) or 5% polyethylene glycol (PEG) aqueous mixtures containing various combinations of 2% triazine (TRI), 5% triethanolamine (TEA), 5% linear alkylbenzene sulfonate (LAS), or 5% sulfurized ricinoleic acid (SRA). Erythema and edema were evaluated and skin biopsies for histopathology were obtained at 4 and 8 hours. IPPSFs (n = 4) were exposed to control MO or PEG mixtures and complete MO or PEG mixtures, and perfusate samples were collected hourly to determine interleukin- (IL-) 8 release. The only significant (p < 0.05) mixture effects observed in IPPSFs were with SRA + MO that caused an increase in IL-8 release after 1 or 2 hours' exposure. In vivo exposure to TRI alone appeared to increase erythema, edema, and dermal inflammation compared to the other additives, while SRA alone was least likely to initiate a dermal inflammatory response. In 2-component mixture exposures, the presence of TRI appeared to increase the dermal inflammatory response at 4 and 8 hours especially with the PEG mixtures. In the 3- and 4-component mixtures, MO mixtures are more likely to incite an inflammatory response than PEG mixtures. TRI exhibited the highest toxicity toward HEK, which correlates well to the in vivo irritation and morphology results. In summary, these preliminary studies suggest that the biocide, TRI, is the more potent of the 4 performance additives in causing dermal irritation, and this may vary depending on whether the worker is exposed to a synthetic (PEG)- or MO-based fluid. These findings will however require further clinical studies to validate these acute dermal effects as well as human cumulative irritation following exposure to similar cutting fluid formulations in the workplace.     

Relationship between eye and skin irritation in rabbits using a series of textile fiber finishes.

A series of 76 fiber finishes, typically composed of blends of lubricants, emulsifiers, antistatic agents and fatty acid soaps, were tested in rabbits to determine both the eye and the skin irritation potential. Each finish was classified as being either non-, slightly, mildly, moderately or severely irritating to the target tissue during a 48-h post-treatment period. Seven (9.2%) of the finishes tested were severely irritating to both the skin and the eye; two (2.6%) were determined to be non-irritating to both tissues. While occasionally finishes produced equal degrees of damage resulting in similar irritancy classifications, seven (9.2%) finishes were found to be severely irritating to the skin without producing any irritation in the eye. Conversely, one finish was found to be a severe eye irritant without producing any skin irritation. The suggested use of the skin irritation data to predict the ocular reaction needs to be carefully examined, particularly with materials such as these fiber finishes. The prediction that a severe skin irritant is also a severe eye irritant was demonstrated to be in error with 8 of 75 (10.5%) of the finishes studied. Further, there is little predictive association between the skin and eye irritation for these compounds.     

Unexpected skin barrier influence from nonionic emulsifiers

Skin disorders are often treated with creams containing various active substances. The creams also contain emulsifiers, which are surface-active ingredients used to stabilize the emulsion. Emulsifiers are potential irritants and in the present study the influence of stearic acid, glyceryl stearate, PEG-2, -9, -40, and -100 stearate, steareth-2, -10 and -21 on normal as well as on irritated skin have been evaluated with non-invasive measurements. Test emulsions were created by incorporating 5% emulsifiers in a water/mineral oil mixture (50:50). The emulsions and their vehicle were then applied to normal skin for 48 h and to sodium lauryl sulfate (SLS) damaged skin for 17 h in aluminum chambers. Twenty-four hours after removal of the chambers the test sites were evaluated for degree of irritation. In normal skin, the emulsifiers induced significant differences in TEWL but not in skin blood flow. Five of the emulsifiers increased TEWL. In SLS-damaged skin an aggravation of the irritation was expected. However, no differences regarding skin blood flow was noted from the emulsifiers. Furthermore, three emulsifiers unexpectedly decreased TEWL. These results highlight the possibility of absorption of these emulsifiers into the lipid bilayer, which increase TEWL in normal skin and decrease TEWL in damaged skin.     

Local irritation study of miporamicin in male rabbits

Local irritation effect of miporamicin (MPM), a new macrolide antibiotics for animal use, on skin and ocular tissues was determined in rabbits by the primary skin irritation test and ocular irritation test, respectively. In the former test, P.I.I. and inflammatory findings increased with increasing exposure time to MPM. A short-time contact with MPM caused relatively little effect on ocular tissues. Contrarily, a long-time contact with MPM caused medium or high degree of inflammatory reactions on cornea, iris and conjunctiva tissues. The increased inflammation was naturally accompanied with increases of the DRAIZE score. All these results suggest that MPM per se has local irritation effect on both skin and ocular tissues.     

Cutaneous effects of transdermal levonorgestrel

The irritation of transdermal devices delivering levonorgestrel and the permeation enhancer ethyl acetate with or without ethanol was evaluated in rabbits. Erythema and oedema were assessed 24, 48 and 72 hr and 7 days after application of the 24-hr delivery system. The devices were found to be mild to moderately irritating, with erythema the primary manifestation. No differences were observed between devices using pure ethyl acetate or ethyl acetate-ethanol (7:3, v/v) as enhancers. Devices using pure ethanol as an enhancer gave levels of irritation similar to those using ethyl acetate-ethanol (7:3) or pure ethyl acetate. Control devices containing only water (no drug) were also found to be mildly irritating to rabbits following a 24-hr exposure period. A histological evaluation of the application sites of two of the formulations confirmed the visual observations of mild subacute irritation. The changes produced by transdermal levonorgestrel were reversible. The problems of skin irritation of transdermal devices is discussed with particular reference to the use of ethyl acetate and ethanol as skin penetration enhancers.     

Chemical exposure and occupational symptoms among Portuguese hairdressers

Hairdressing is predominantly a female activity, in which several chemicals are handled, some of which are known to be allergenic and potentially carcinogenic. Several epidemiological studies showed an association between occupational exposure to chemicals in hairdressing salons and skin and respiratory-tract conditions. The aim of this study were to characterize the occupational exposure to total volatile organic compounds (VOC) and ammonia (NH?) in 50 Portuguese hairdressers' salons and to analyze the prevalence of respiratory and skin symptoms in 134 hairdressing professionals. Data indicated that internal sources of total VOC are mainly due to indoor sources, with average concentrations (1.4 mg/m3) above the Portuguese reference levels (0.6 mg/m3). Of the hairdressers' salons studied, 4% had a mean NH? concentration higher than Portuguese (20 ppm) and American Conference of Industrial Hygienists (ACGIH) (25 ppm) reference levels. Hand dermatitis was the occupational symptom most reported by hairdressers (50%), followed by eye irritation (43%). The results of this study suggest that hairdressers' occupational activities are linked with higher risk of developing hand and wrist/arm dermatitis and symptoms in the upper respiratory tract. The proper use of disposable gloves, hands, wrists, and arms skin monitoring, and the frequent use of moisturizers in the workplace are effective measures to prevent the occurrence of dermatitis in these professionals. Displacement ventilation and/or local exhaust with adequate air exchange rate are recommended particularly in technical areas where hairdressing chemicals are mixed.     

复方咪康唑乳膏豚鼠皮肤刺激性试验观察

目的:探讨复方眯康唑乳膏使用的安全性.方法:以1次给药和多次给药方法,将复方咪康唑乳膏外涂于白色豚鼠背部正常或破损去毛区皮肤,观察豚鼠皮肤刺激性反应.结果:复方咪康唑乳膏对豚鼠正常皮肤平均反应分值均低于0.5分,对豚鼠破损皮肤平均反应分值在给药后1 h和24 h均高于0.5分,但低于2.99分,48 h后平均反应分值均低于0.5分.结论:复方眯康唑乳膏对豚鼠正常皮肤无刺激性,对破损皮肤有轻度刺激性,但给药后48 h,这种刺激性消失.     

Trichloroethylene induced cutaneous irritation in BALB/c hairless mice: histopathological changes and oxidative damage

Trichloroethylene (TCE), a colorless and volatile organic solvent, has long been a major chemical hazard during occupational exposure because of its extensive use in industry. Exposure to TCE can cause significant skin lesions, but the effect of TCE on skin irritation has received little attention. We therefore investigated the effect of TCE on skin irritation and oxidative stress using hairless mice. BALB/c hairless mice were subjected to acute and cumulative topical TCE treatment. Skin reactions were evaluated by visual inspection, histopathology examined by microscopy and oxidative stress assessed by measurement of malondialdehyde (MDA) levels, superoxide dismutase (SOD) activities and nitric oxide (NO) production. Under acute and cumulative TCE irritation, the skin developed erythema and edema, and the predominant histopathological features were hyperkeratosis, spongiosis and inflammatory cell infiltrates. In parallel to these morphological changes, acute TCE irritation also concentration-dependently increased MDA levels and inhibited SOD activities of the skin. However, in cumulative irritation, the MDA levels and SOD activities were initially elevated with increased TCE concentrations, but thereafter reduced with further concentration increments; the linear dose-response relationship was not preserved. TCE also concentration-dependently increased NO production both in acute and cumulative irritation. These results suggest that TCE is capable of producing skin irritation effect in vivo, with histopathological changes characterized by hyperkeratosis, spongiosis and inflammatory cell infiltrates. Moreover, oxidative stress may be associated with the clinical manifestations and histopathological abnormalities in TCE-induced skin irritation.     

Evaluation of dermal and eye irritation and skin sensitization due to carbon nanotubes

The present paper summarizes the results of our studies on dermal and eye irritation and skin sensitization due to carbon nanotubes (CNTs), whose potential applications and uses are wide and varied, including CNT-enhanced plastics, electromagnetic interference/radio-frequency (EMI/RFI) shielding, antistatic material, flexible fibers and advanced polymers, medical and health applications, and scanning probe microscopy. Skin and eyes have the highest risk of exposure to nanomaterials, because deposition of nanomaterials to the surficial organs has the potential to be a major route of exposure during the manufacturing, use, and disposal of nanomaterials. Two products composed of single-walled carbon nanotubes (SWCNTs) and two products composed of multi-walled carbon nanotubes (MWCNTs) were tested regarding acute dermal and acute eye irritation using rabbits, and skin sensitization using guinea pigs. The concentrations of the CNTs in the substances were the maximum allowable for administration. The two products of SWCNTs and one of the products of MWCNTs were not irritants to the skin or eyes. The other product of MWCNTs caused very slight erythema at 24 h, but not at 72 h, after patch removal in the dermal irritation experiments and conjunctival redness and blood vessel hyperemia at 1 h, but not at 24 h, in eye irritation experiments. These findings showed that one product of MWCNTs was a very weak acute irritant to the skin and eyes. No products of SWCNTs and MWCNTs exhibited skin-sensitization effects. Our knowledge of the toxicological effects of CNTs is still limited. Further information is needed to clarify the potential for irritation and sensitization given the complex nature of CNTs.     

Physiologically Based Pharmacokinetics and the Dermal Absorption of 2-Butoxyethanol Vapor by Humans

It has generally been assumed that the skin contributes onlyminor amounts to the total uptake of solvent vapors, relativeto the respiratory tract. Contrary to this assumption, the widelyused glycol ether solvent, 2-butoxyethanol (BE), has been reportedto be more effectively absorbed through the skin (75% of thetotal uptake) than through the lungs of humans (Johanson andBoman, 1991, Br. J. lad. Med. 48, 788). The possibility thatthe finger prick blood sampling technique used in the Johansonand Boman study was confounded by locally high concentrationsof BE at the site of absorption was suggested using a previouslydeveloped PBPK model (Corley et al., 1994, Toxicol. Appl. Pharmacol.129, 61). The current study was conducted to verify the PBPKanalysis and to determine whether or not the skin was the majorsite for absorption of BE vapor by exposing one arm from eachof six human volunteers to 50 ppm 13C₂-BE vapor for 2 hr. Toevaluate the potential consequences of blood sampling techniques,samples were taken from both the unexposed arm (catheter; duringand after exposure) and the exposed arm (finger prick; end ofthe exposure only) for analysis of both BE and its major metabolite,butoxyacetic acid (BAA). Butoxyacetic acid is responsible forthe hemolysis observed in toxicity studies with laboratory animals.Humans, however, are significantly less sensitive to this effect.The concentration of BE in the finger prick blood samples averaged1500 times higher than the corresponding concentration in venousblood sampled from a catheter installed in the unexposed armat the end of the exposure. Blood BAA levels were generallywithin a factor of 4 of each other for the two techniques and,therefore, was considered a better indicator of systemic absorption.Urine was collected for 24 hr and analyzed for the followingmetabolites found in rat metabolism studies: free and conjugatedBE, BAA, ethylene glycol (EG), and glycolic acid (GA), withonly BAA detected in the human urine. More importantly, urinaryBAA was found to be extensively conjugated (67%) with glutamine,confirming recent reports. These results, coupled with PBPKmodeling of worst-case exposure scenarios (no clothing, 100%of the body was exposed), demonstrated that no more than 15–27%(low-to-high relative temperatures and humidities), not 75%,of the total uptake of BE could be attributed to the skin ofhumans during simulated 8-hr exposures to the ACGIH TLV concentrationof 25 ppm. Even less of the total uptake was attributed to theskin during simulations of exercise with whole-body exposures(5–9%) or by more realistic exposures of only the armsand head (1–8%). As a result, humans are unlikely to reachhemolytic concentrations of the metabolite BAA in blood followingvapor exposures to BE.     

The use of hairless (IAF/HA-HO) guinea pigs for the determination of delayed-type hypersensitivity to tuberculin

Guinea pigs are a classic animal model for studying delayed-type hypersensitivity (DTH) reactions. However, skin irritation due to hair removal can interfere with the evaluation of the modulation of these responses by various mediators. A DTH model using hairless (IAF/HA-HO) guinea pigs, sensitized with complete Freund's adjuvant and repeatedly skin tested with tuberculin, purified protein derivative, (PPD) has therefore been developed. At 10 weeks after sensitization, intradermal PPD elicited minimal erythema at 6 h, which increased over the next 18 h to a maximum at 24 h, and declined by 48 h. The response could be quantified by bioassay using graded doses of PPD. Reactions at 24 h were characterized by predominantly mononuclear cell deep and superficial dermal infiltrates. Dermal DTH in hairless guinea pigs is thus, grossly and histologically similar to that seen in Hartley guinea pigs.