Anticonvulsant potential of Grewia tiliaefolia in pentylenetetrazole induced epilepsy: insights from in vivo and in silico studies.

Epilepsy, a chronic neurological condition, impacts millions of individuals globally and remains a significant contributor to both illness and mortality. Available antiepileptic drugs have serious side effects which warrants to explore different medicinal plants used for the management of epilepsy reported in Traditional Indian Medicinal System (TIMS). Therefore, we explored the antiepileptic potential of the Grewia tiliaefolia (Tiliaeceae) which is known for its neuroprotective properties. Aerial parts of G. tiliaefolia were subjected to extraction with increasing order of polarity viz. hexane, chloroform and methanol. Antioxidant potential of hexane, chloroform and methanol extracts of G. tiliaefolia was evaluated by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay, total antioxidant capacity (TAC) assay, reducing power assay (RPA) and DNA nicking assay. Additionally, quantitative antioxidant assays were also conducted to quantify total phenolic (TPC) and total flavonoid content (TFC). As revealed by in vitro assays, methanol extract was found to contain more phenolic content. Hence, the methanol extract was further explored for its anticonvulsant potential in pentylenetetrazole (PTZ) induced acute seizures in mice. The methanol extract (400 mg/kg) significantly increased the latency to occurrence of myoclonic jerks and generalized tonic clonic seizures (GTCS). Additionally, it also reduced duration and seizure severity score associated with GTCS. The Grewia tiliaefolia methanol extract was further screened by Ultra High-Performance Liquid Chromatography (UHPLC) for presence of polyphenolic compounds, among which gallic acid and kaempferol were present in higher amount and were further analysed by in silico study to predict their possible binding sites and type of interactions these compounds show with gamma amino butyric acid (GABA) receptor and glutamate α amino-3- hydroxyl-5-methyl-4-isoxazolepropionic acid (Glu-AMPA) receptor. It was revealed that gallic acid and kaempferol had shown agonistic interaction for GABA receptor and antagonistic interaction for Glu-AMPA receptor. We concluded that G. tiliaefolia showed anticonvulsant potential possibly because of gallic acid and kaempferol possibly mediated through GABA and Glu-AMPA receptor.

Acquired Color Vision Defects and Hexane Exposure: A Study of San Francisco Bay Area Automotive Mechanics.

Occupational exposure to solvents, including n-hexane, has been associated with acquired color vision defects. Blue-yellow defects are most common and may be due to neurotoxicity or retinal damage. Acetone may potentiate the neurotoxicity of n-hexane. We present results on nonhexane solvent and hexane exposure and color vision from a cross-sectional study of 835 automotive repair workers in the San Francisco Bay Area, California (2007-2013). Cumulative exposure was estimated from self-reported work history, and color vision was assessed using the Lanthony desaturated D-15 panel test. Log-binomial regression was used to estimate prevalence ratios for color vision defects. Acquired color vision defects were present in 29% of participants, of which 70% were blue-yellow. Elevated prevalence ratios were found for nonhexane solvent exposure, with a maximum of 1.31 (95% confidence interval (CI): 0.86, 2.00) for blue-yellow. Among participants aged ≤50 years, the prevalence ratio for blue-yellow defects was 2.17 (95% CI: 1.03, 4.56) in the highest quartile of nonhexane solvent exposure and 1.62 (95% CI: 0.97, 2.72) in the highest category of exposure to hexane with acetone coexposure. Cumulative exposures to hexane and nonhexane solvents in the highest exposure categories were associated with elevated prevalence ratios for color vision defects in younger participants.

N-hexane inhalation during pregnancy alters DNA promoter methylation in the ovarian granulosa cells of rat offspring.

The N-hexane-induced impact on the reproductive system of the offspring of animals exposed to n-hexane has caused great concern. Pregnant Wistar rats inhaled 500, 2 500 or 12 500 ppm n-hexane during gestational days 1-20. Clinical characteristics and developmental indices were observed. Ovarian granulosa cells were extracted from F1 rats, the number of follicles was determined in ovarian slices and promoter methylation was assessed using MeDIP-Chip. Several methods were used to analyze the scanned genes, including the Gene Ontology Consortium tools, the DAVID Functional Annotation Clustering Tool, hierarchical clustering and KEGG pathway analysis. The results indicated that the live pups/litter ratio was significantly lowest in the 12 500 ppm group. A significant decrease in secondary follicles and an increase in atresic follicles were observed in the 12 500 ppm group. The number of shared demethylated genes was higher than that of the methylated genes, and the differentially methylated genes were enriched in cell death and apoptosis, cell growth and hormone regulation. The methylation profiles of the offspring from the 500 ppm and control groups were different from those of the 2500 and 12 500 ppm groups. Furthermore, the methylation status of genes in the PI3K-Akt and NF-kappa B signaling pathways was changed after n-hexane exposure. The Cyp11a1, Cyp17a1, Hsd3b1, Cyp1a1 and Srd5a1 promoters were hypermethylated in the n-hexane-exposed groups. These results indicate that the developmental toxicity of n-hexane in F1 ovaries is accompanied by the altered methylation of promoters of genes associated with apoptotic processes and steroid hormone biosynthesis.

Inhaled pan-selectin antagonist Bimosiamose attenuates airway inflammation in COPD.

Selectins, a family of cell adhesion molecules, are involved in leukocyte extravasation to sites of inflammation. We investigated the safety and efficacy of the inhaled pan-selectin antagonist Bimosiamose in patients with chronic obstructive pulmonary disease (COPD). 77 COPD patients (mean forced expiratory volume in 1 s, 57% pred.) were enrolled in a cross-over, double-blind, randomized, Placebo-controlled, multi-center trial. Bimosiamose (10 mg) or Placebo was inhaled twice daily via the breath actuated nebulizer Akita2 Apixneb™ for 28 days on top of standard bronchodilator therapy. Efficacy was assessed by measurement of inflammatory parameters in induced sputum (differential cell count, interleukin-8, matrix-metalloproteinase-9, myeloperoxidase) and lung function at day 28 of both treatment periods. The total adverse event ratio of Bimosiamose compared to Placebo treatment was balanced. Compared to Placebo, treatment with Bimosiamose led to a decrease of the interleukin-8 concentration (-9.49 ng/mL, 95%CI -18.8 to -2.7 ng/mL, p = 0.008), for the neutrophil count a difference of -0.368 × 10(6) cells/mL (95%CI -1.256 to 0.407 × 10(6)/mL, p = 0.313) was found. The macrophage count decreased by -0.200 × 10(6) cells/mL (95%CI -0.365 to -0.044 × 10(6) cells/mL, p = 0.012). Most lung function parameters showed a small numeric increase. Inhalation of Bimosiamose for 28 days was safe and well tolerated in patients with COPD. It led to an attenuation of airway inflammation (EudraCT 2009-017257-35; NCT ID: NCT01108913).

Gas-producing cellulitis from injection of spot remover fluid (n-Hexane).

BACKGROUND: Subcutaneous administration of hydrocarbons, categorized according to their toxicological profiles, is rare compared to oral, inhalational, and cutaneous routes of exposure. Furthermore, injection of n-hexane in humans has not been described. OBJECTIVES: This report demonstrates a singular case of subcutaneous administration of n-hexane. CASE REPORT: A 21-year-old man presented to the Emergency Department (ED) 7 h after injecting his left antecubital fossa with approximately 5 cc of spot remover fluid, which contained more than 95% n-hexane, in a suicide attempt. There was redness in the left forearm, but no apparent swelling was observed. He was administered tetanus prophylaxis and discharged with follow-up. However, the patient returned to the ED 14 h later, complaining of progression of the swelling around the injection site extending to the axilla. Significant volume of air in the soft tissue of the affected extremity was noted on both the radiograph and computed tomography scan; therefore, an immediate extensive incision and debridement of the diseased limb was performed. The postoperative course was uneventful, and a complete resolution of emphysema without any functional deficits was obtained for 5 months of follow-up. CONCLUSION: In patients suffering from n-hexane injection, initial physical examination findings may not be apparent. Thus, the patient must be monitored closely for evidence of a spread of subcutaneous gas with elevation and immobilization. If increase in tissue pressure or spread of gas is not prevented, as in our case, immediate incision and removal of the toxic substances should be planned.

Efficacy of the pan-selectin antagonist Bimosiamose on ozone-induced airway inflammation in healthy subjects--a double blind, randomized, placebo-controlled, cross-over clinical trial.

Selectins, a family of cell adhesion molecules, are involved in the activation and extravasation of leukocytes in inflammatory diseases. Inhalation of ozone induces an inflammation of the airways, which is dominated by neutrophils. We investigated the effect of repeated inhalations of the pan-selectin antagonist Bimosiamose on ozone-induced airway inflammation in healthy volunteers. In a double-blind, placebo-controlled, randomized, cross-over study Bimosiamose (10 mg bid) was inhaled via a breath actuated nebulizer (AKITA2 APIXNEB(®)) for 4 days. Treatment was followed by inhalation of ozone (250 ppb) for 3 h with intermittent exercise. Induced sputum was collected 3 h post ozone challenge for analysis of cellular and non-cellular composition. 18 subjects were randomized and completed the study. All treatments were safe and well tolerated. Compared to placebo Bimosiamose reduced the numbers of sputum neutrophils by 40% (p = 0.068) and concentrations of interleukin-8 and matrix-metalloproteinase-9 in sputum supernatant by 35% (p = 0.004) and 46% (p = 0.022), respectively. Inhalation of Bimosiamose showed favourable anti-inflammatory effects on ozone-induced airway inflammation in healthy volunteers. Further studies have to proof and translate this anti-inflammatory effect of Bimosiamose into a clinical benefit in patients with chronic obstructive pulmonary disease. (ClinTrialgov Ident: NCT01108913).

[Effects of n-hexane exposure on human serum myelin basic proteins].

OBJECTIVE: To explore the effects of n-hexane on expression of serum myelin proteins (MBP) in workers occupationally exposed to n-hexane. METHODS: In this study, 269 workers exposed to n-hexane for more than one year and 104 subjects not exposed to n-hexane served as the exposure group and the control group, respectively. The urinary 2,5-hexanedione levels in all subjects were detected. On the basis of urinary 2,5-hexanedione levels, the exposure group was divided into the high exposure sub-group and low exposure sub-group. The serum myelin basic protein (MBP) levels were measured by ELISA kit. RESULTS: The mean concentration of urinary 2,5-hexanedione in the exposed group was (3.10 +/- 1.35) mg/L. The concentration of urinary 2,5-hexanedione in the control group was undetectable. The levels of serum MBP in the high exposure sub-group and low exposure sub-group were (2.43 +/- 0.24) and (1.62 +/- 0.23) microg/L, respectively, which were significantly higher than that (0.78 +/- 0.12) microg/L in the controls (P < 0.01). Pearson correlation analysis showed the positive correlation between serum MBP levels and urinary 2,5-hexanedione levels (r = 0.781, P < 0.01). CONCLUSION: The results of present study showed that the serum MBP levels of workers occupationally exposed to n-hexane significantly elevated, and the serum MBP can serve as the effective biomarker of n-hexane exposure.

[Effects on serum myelin proteins of n-hexane exposure].

OBJECTIVE: Exploring the effects of n-hexane on expression of serum myelin proteins in occupational exposure workers, and finding the early biomarker of n-hexane exposure. METHODS: In the study, 373 subjects were recruited, 269 exposure workers (work experience of more than1 year) and 104 non-exposure workers were selected. Firstly examined the level of urinary 2,5-hexanedione in the two groups, based on urinary 2,5-hexanedione biological limit value (4 mg/L), the exposed group was divided into high-exposed group and low-exposed group. And then collected blood samples and extracted serum. Human peripheral myelin protein zero (P0) antibody (IgG, IgM) and human peripheral myelin protein two (P2) antibody (IgG, IgM) analysis was performed according to ELISA kit. RESULTS: The concentration of urinary 2,5-hexanedione in the exposed group was (3.10 ± 1.35) mg/L. The level of P0 antibody (IgG, IgM) and P2 antibody (IgG, IgM) in the high-exposed group and low-exposed group were both higher than that in the controls (P < 0.01). CONCLUSION: P0 antibody and P2 antibody could be used as the early biomarkers of n-hexane exposure, which not only evaluate the occupational hazards in the early, but also provide the policy maker with scientific evidence.

Immunomodulation property of hexane fraction of leaves of Cinnamomum tamala Linn. in rats.

The leaves of Cinnamomum tamala Linn. (CT) (Lauraceae) clinically used in Ayurveda as antidiabetic and diuretic, but no reports are available towards immunomodulating property. Its hexane fraction (CTH) was orally given to rats for 10 days and delayed type of hypersensitivity (DTH), antibody production against sheep red blood cells (SRBCs), mitotic index in bone marrow cells and concanavalin A (Con A) mediated proliferation of lymphocytes were assessed. Further on 30 days treatment, change in body weight (BW), spleen weight, thymus weight, bone marrow cellularity and hematological changes were observed. It inhibited significantly the DTH response (IC(50) 1475 +/- 57.19 mg kg(-1) BW), antibody production, suppressed mitotic index in bone marrow cells along with the suppression of lymphocyte proliferation against Con A (IC(50) 63.33 +/- 1.95 microg mL(-1)). In all experiments, cyclophasphamide and dexamethasone had been used as reference drug for in vivo and in vitro studies, respectively. On 30 days treatment, the CTH (800 mg kg(-1) BW and above) significantly suppressed growth rate, increase of spleen and thymus weight and low bone marrow cellularity. In hematological examination, it inhibited total white blood cell and lymphocytes count and increased per cent of polymorphs. Thus, it could be suggested that the fraction possesses immunosuppressive property at doses, higher than 800 mg kg(-1) BW in rats.

Evaluation of a novel polihexanide-preserved wound covering gel on dermal wound healing.

OBJECTIVE: Daily wound assessment, including dressing changes and the removal of old ointments causes discomfort for the patient. We therefore developed a new thermoreversible and transparent gel formulation that allows for filling wounds of different shapes and depths. The aim of the study was to investigate the effect of a wound covering gel on wound healing and the skin's microcirculation. MATERIALS AND METHODS: Investigations were carried out in a standardized and reproducible wound model (hairless mice SKH1/hr, n = 30). Three groups were studied by intravital fluorescence microscopy: treatment with polihexanide-preserved wound covering gel, a formulation containing 3% povidone (PVP)-iodine, and physiological saline for control. Microcirculatory standard parameters were analysed. RESULTS: The non-perfused area vanished within 14 days due to angiogenesis. The venular diameter, oedema formation and functional capillary density showed no significant differences between the three groups. CONCLUSION: The use of the newly developed wound covering gel has no toxic effects on microcirculation and angiogenesis and reveals no significant differences in the overall assessment of microcirculation compared to the control group and the well-established PVP-iodine. The transparent antibacterial wound covering gel allows for direct wound assessment. Due to its thermoreversible gel formulation it enables good wound contact and easy handling.

Occupational ototoxicity of n-hexane.

The ability of chemicals to produce hearing loss themselves or to promote noise-induced hearing loss has been reported for some organic solvents. The objective of this study was to review the literature on the effects of low-level exposure to n-hexane on the auditory system and consider its relevance for occupational settings. Both human and animal investigations were evaluated only for realistic exposure concentrations based on the permissible inhalation exposure limits. In Quebec, the time-weighted average exposure value (TWAEV) for 8 h is 50 ppm. In humans, the upper limit for considering ototoxicity data relevant to the occupational exposure situation was set at five times the TWAEV. Animal data were evaluated only for exposure concentrations up to 100 times the TWAEV. There is no convincing evidence of n-hexane-induced hearing loss in workers. In rats, n-hexane seems to affect auditory function; however, the site of these alterations cannot be determined from the present data. Further studies with sufficient data on the exposure of workers to n-hexane are necessary to make a definitive conclusion. In the interim, we recommend considering n-hexane as a possibly ototoxic agent.

Inhalant abuse detection and evaluation in young Tunisians.

Occupational exposure biological monitoring techniques were applied for the diagnosis of inhalation abuse and for the evaluation of the levels of exposure to benzene, toluene, ethylbenzene, xylenes, and n-hexane, in 44 Tunisian adolescents and children suspected for volatile substance addiction. Urinary trans,trans-muconic acid, hippuric acid (HA), mandelic acid, and methylhippuric acids determinations were performed by high performance liquid chromatography with a photodiode array detector, and urinary o-cresol (o-Cr) and 2,5-hexanedione (HD) were extracted simultaneously and measured using gas chromatography with a flame ionization detector. Given the high linearity ranges, HD and o-Cr occupational exposure monitoring techniques could be applied without modification. However, urinary sample dilution was necessary before HA analysis. Concentrations were compared with the maxima of normal values (MNVs) in the general population and to the biological exposure indices (BEIs) used in occupational toxicology. Values as high as 6610-fold the MNV and 68 times the BEI were registered. The subjects showed high exposure to toluene and hexane. Measured metabolites HA and/or o-Cr and HD enabled the easy detection and evaluation of exposure levels. The problem of inhalant abuse should be given more attention and treated through an effective prevention strategy.

Bone marrow mesenchymal stem cells protect against n-hexane-induced neuropathy through beclin 1-independent inhibition of autophagy.

Chronic exposure to n-hexane, a widely used organic solvent in industry, induces central-peripheral neuropathy, which is mediated by its active metabolite, 2,5-hexanedione (HD). We recently reported that transplantation of bone marrow-mesenchymal stem cells (BMSC) significantly ameliorated HD-induced neuronal damage and motor deficits in rats. However, the mechanisms remain unclear. Here, we reported that inhibition of HD-induced autophagy contributed to BMSC-afforded protection. BMSC transplantation significantly reduced the levels of microtubule-associated protein 1 light chain 3-II (LC3-II) and the degradation of sequestosome-1 (p62) in the spinal cord and sciatic nerve of HD-intoxicated rats. Downregulation of autophagy by BMSC was also confirmed in VSC4.1 cells exposed to HD. Moreover, inhibition of autophagy by PIK III mitigated the neurotoxic effects of HD and, meanwhile, abolished BMSC-afforded neuroprotection. Furthermore, we found that BMSC failed to interfere with Beclin 1, but promoted activation of mammalian target of rapamycin (mTOR). Unc-like kinse 1 (ULK1) was further recognized as the downstream target of mTOR responsible for BMSC-mediated inhibition of autophagy. Altogether, BMSC transplantation potently ameliorated HD-induced autophagy through beclin 1-independent activation of mTOR pathway, providing a novel insight for the therapeutic effects of BMSC against n-hexane and other environmental toxicants-induced neurotoxicity.

N-hexane neuropathy in screen printers.

BACKGROUND: To study the clinical and electrophysiological profile of n-hexane neuropathy in a tertiary care center of India. METHODS: Twenty five screen printers from five different factories, with peripheral neuropathy were included in the study. A detailed general physical, systemic and neurological examination was conducted Visual acuity, color vision and field charting was done in all the subjects. All patients were subjected to Folstein mini mental scale examination. Electrophysiological evaluation included motor and sensory conduction studies of the conventionally studied nerves of upper and lower limbs, Needle EMG of various distal and proximal muscles and patterned visual evoked responses. The electrophysiological profile was repeated every three months till one year. Sural nerve biopsy was studied in six patients. The patients were followed for a maximum of 4 years. RESULTS: Twenty three [92%] patients had sensory- motor neuropathy, while pure sensory neuropathy was seen in two. The sensory conductions were affected almost equally in upper as well as the lower limbs, while the motor conductions were affected more in the lower limbs than the upper limbs. The sensory conductions were not recordable in both the upper and the lower limbs in 18 [72%] patients. Motor conduction studies revealed an asymmetric and patchy involvement. Proximal conduction block was seen in 3 patients [12%]. On needle EMG features of denervation were seen in all patients. P100 latency was normal in all. Sural nerve biopsy showed a selective decrease in large myelinated axons with demyelination. Axonal swelling with focal areas of demyelination was observed in two patients. CONCLUSIONS: The electrophysiological patterns as well as the histopathology reflect the pathophysiology of n-hexane neuropathy.

Physiochemical properties, safety and pharmacokinetics of bimosiamose disodium after intravenous administration.

OBJECTIVE: Bimosiamose is a novel synthetic panselectin antagonist being developed for the treatment of acute and chronic inflammatory disorders. Therefore, we have studied the pharmacokinetics and tolerability and determined the pharmacokinetically relevant physicochemical characteristics of bimosiamose. METHOD: A randomized, double-blind, placebo-controlled dose-escalation trial in healthy male subjects has been carried out. The subjects received intravenous infusions of 0.5-30 mg/kg bimosiamose disodium. RESULTS AND CONCLUSIONS: The maximum plasma concentration (Cmax) was 675 +/- 11 microg/ml with a tmax of 0.36 +/- 0.13 h (mean +/- SD). The elimination half-life t1/2 was 4.1 +/- 1.0 h, and the AUC(o-inf) was 1,360 +/- 393 h microg/ml after the 30 mg/kg dose. The clearance and the apparent volume of distribution decreased with increasing dose to 22 +/- 6 ml/kg/h and 40 +/- 13 ml/kg/h at the highest dose, respectively, and the mean residence time increased to 1.8 +/- 0.35 h. Bimosiamose was safe and well-tolerated.

Hypoglycaemic and antidiabetic activity of acetonic extract of Vernonia colorata leaves in normoglycaemic and alloxan-induced diabetic rats.

The aqueous extract of Vernonia colorata (Willd.) Drake (Composeae) leaves is used by African traditional medicine practitioners as a remedy for the treatment of diabetes. Our previous studies have shown the hypoglycaemic activity of the aqueous extract of Vernonia colorata leaves (300 mg/kg, per os) in normoglycaemic rats. The aim of the present study was to investigate the hypoglycaemic and antidiabetic activity of acetonic and hexanic extracts of the leaves of Vernonia colorata in order to further discriminate the type of extract which provides a better antidiabetic activity. Experiments were performed in normoglycaemic and alloxan-induced diabetic rats. The acetonic extract of the leaves of Vernonia colorata (AELVC) (100 mg/kg, per os) induced a significant decrease of blood glucose in normoglycaemic rats. The glycaemia varied from 4.72+/-0.11 to 3.72+/-0.22 mmol/l (p<0.05, n=5) 3 h after AELVC administration per os. In contrast, the hexanic extract of the leaves of Vernonia colorata (HELVC) increased significantly the glycaemia in normoglycaemic rats. Like glibenclamide, AELVC has an antihyperglycaemic effect in oral glucose tolerance test (OGTT) and alloxan-induced diabetic rats. These results have shown that: (i) AELVC and HELVC have an opposite effect on basal blood glucose in normoglycaemic rats, suggesting that the mechanisms of action of both above-mentioned extracts are different; (ii) AELVC has also an antidiabetic activity in hyperglycaemic rat models.

N-hexane neuropathy with vertigo and cold allodynia in a silk screen printer: A case study.

N-hexane neuropathy is an occupational disease caused by exposure to n-hexane, which is used as a solvent in silk screen printing. Here, we describe a 35-year-old man, a silk screen printer by profession, who presented with dizziness, distal swelling of both lower limbs for 10 months and tingling and burning sensation in both feet for 9.5 months along with cold allodynia. The patient had normal results of a motor and sensory system examination, apart from an impaired temperature sense. Nerve conduction tests showed a conduction block in bilateral common peroneal nerves and absence of conduction in bilateral sural nerves. These symptoms resolved when further exposure to n-hexane was ceased but cold allodynia remained. Thus, cold allodynia and impaired temperature sense can be a manifestation of n-hexane neuropathy. Hence, abnormalities on nerve conduction studies can be detected in n-hexane neuropathy patients, even before clinical examination detects any such abnormalities. In the case of the patients presenting with sensory motor neuropathy, history of occupational exposure to n-hexane becomes important, as the sooner the disease is detected, the better the chances of recovery.

Biomarker research in neurotoxicology: the role of mechanistic studies to bridge the gap between the laboratory and epidemiological investigations.

There is an increasing interest in the development and validation of biomarkers for use in biochemical/molecular epidemiological studies. Though the area of neurotoxicology has received much attention in the past several years, it still lags behind with regard to the development of biomarkers, particularly those of health effects and susceptibility. This review discusses several aspects of biomarker research as it relates to neurotoxic compounds and focuses on selected agents (organophosphorus insecticides, styrene, n-hexane, carbon disulfide, acrylamide), which have been the subject of a number of investigations in animals and humans. While traditional biomonitoring approaches and novel techniques (e.g., hemoglobin adducts) provide several measurements for monitoring exposure to neurotoxic chemicals, potential markers of genetic susceptibility have been seldom investigated in a neurotoxicology context. Furthermore, the complexity of the nervous system, together with the multiplicity of end points and the limited knowledge of the exact mechanism(s) of action of neurotoxicants, has led to only limited advancements in the development of biomarkers for neurotoxic effects. Significant progress in this area will depend upon an increased understanding of the cellular, biochemical, and molecular targets directly involved in neurotoxicity.

A new HPLC-based method for the quantitative analysis of inner stratum corneum lipids with special reference to the free fatty acid fraction.

The inner stratum corneum is likely to represent the location of the intact skin barrier, unperturbed by degradation processes. In our studies of the physical skin barrier a new high-performance liquid chromatography (HPLC)-based method was developed for the quantitative analysis of lipids of the inner stratum corneum. All main lipid classes were separated and quantitated by HPLC/light scattering detection (LSD) and the free fatty acid fraction was further analysed by gas-liquid chromatography (GLC). Mass spectrometry (MS) was used for peak identification and flame ionization detection (FID) for quantitation. Special attention was paid to the free fatty acid fraction since unsaturated free fatty acids may exert a key function in the regulation of the skin barrier properties by shifting the physical equilibrium of the multilamellar lipid bilayer system towards a noncrystalline state. Our results indicated that the endogenous free fatty acid fraction of the stratum corneum barrier lipids in essence exclusively consisted of saturated long-chain free fatty acids. This fraction was characterized as a very stable population (low interindividual peak variation) dominated by saturated lignoceric acid (C24:0, 39 molar%) and hexacosanoic acid (C26:0, 23 molar%). In addition, trace amounts of very long-chain (C32-C36) saturated and monounsaturated free fatty acids were detected in human forearm inner stratum corneum. Our analysis method gives highly accurate and precise quantitative information on the relative composition of all major lipid species present in the skin barrier. Such data will eventually permit skin barrier model systems to be created which will allow a more detailed analysis of the physical nature of the human skin barrier.