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PubMed1996

Central and peripheral noradrenergic responses to 14 days of spaceflight (SLS-2) or hindlimb suspension in rats.

INTRODUCTION: The purposes of this work were to assess the influence of microgravity on the central and peripheral noradrenergic activity to reevaluate SLS-1 mission findings and to compare it with that of simulated microgravity in rats. METHODS: The norepinephrine (NE) contents of the brainstem cell groups (A1, A2, A5, and A6) and organs (heart and kidneys) involved in blood pressure regulation were determined in rats after a 14-d spaceflight (SLS-2 with animals sacrificed 6 h after landing) and after a 14-d hindlimb suspension followed with 6 h of recovery. RESULTS: After SLS-2 spaceflight, NE contents were not significantly different between flight and ground-based rats either in A1 (5.2 +/- 0.5 vs. 5.7 +/- 0.4 pmol/structure), rostral A2 (12.1 +/- 0.5 vs. 11.1 +/- 0.9 pmol/structure), caudal A2 (3.2 +/- 0.6 vs. 4.3 +/- 0.5 pmol/structure) and A5 (4.4 +/- 0.4 vs. 4.3 +/- 0.5 pmol/structure) nuclei or in cardiac atria (98.6 +/- 7.5 vs. 83.4 +/- 8.9 pmol.mg-1 protein), ventricles (38.3 +/- 2.2 vs. 44.1 +/- 2.8 pmol.mg-1 protein) and kidneys (13.4 +/- 0.8 vs. 17.7 +/- 1.5 pmol.mg-1 protein). NE content was unchanged in A6 nucleus after SLS-2 comparing with control rats (respectively 4.1 +/- 0.3 vs. 4.5 +/- 0.5 pmol/structure), while it was depleted after SLS-1 mission (2.9 +/- 0.3 vs. 8.8 +/- 0.7 pmol/structure, p < 0.001) probably in relation with the stressful conditions on return to Earth. Similarly, no alterations between suspended and control rats were noted in central and peripheral NE contents after 14 d of suspension and after 6 h of recovery, whereas NE turnover studies evidenced large changes in the activities on structures on suspension and on recovery. CONCLUSION: These results suggest that only NE turnover determination will provide information about the role of the sympathetic system in the cardiovascular deconditioning. This raises the problem of the necessity to experiment inflight (injections, sacrifice) in order to avoid the recovery effects of the few hours following the landing.

Animals↗

PubMed1998

SLS-irritated human skin shows no correlation between degree of proliferation and TEWL increase.

It is well known that cutaneous irritants influence epidermal proliferation but the pathogenesis is poorly understood. Recent investigations have shown that the skin barrier integrity influences the proliferation of the basal keratinocytes. Our question was whether the proliferating activity of keratinocytes is indeed regulated by the degree of skin barrier damage or by a direct toxic action of the irritant on the keratinocytes. Therefore various degrees of skin irritation were induced by the application of 0.1%, 0.5% and 2% sodium lauryl sulphate (SLS) solution to the forearm skin of six healthy volunteers. This experiment was performed to evaluate the relationship between SLS concentration and epidermal proliferation. In a second experiment another 14 volunteers were treated with a single SLS concentration (0.5%) to look for interindividual differences in the patterns of skin reaction and susceptibility to the irritant. Skin barrier function was evaluated by measurements of transepidermal water loss (TEWL) before and after irritation. Punch biopsies were taken after 96 h from exposed areas and from unexposed normal skin. Dividing keratinocytes were identified immunocytochemically using three different monoclonal antibodies: PCNA, MIB 1 and KiS1. Exposure to SLS resulted in concentration-dependent increases in both TEWL and epidermal proliferation. However, no significant correlation could be found between the degree of hyperproliferation and the TEWL changes. The results suggest that epidermal proliferation is modulated by a direct interaction of the surfactant with the keratinocytes and/or by release of mediators rather than the consequence of a barrier disturbance.

Adult↗

PubMed2006

Combined effects of NaF and SLS on acid- and polysaccharide-formation of biofilm and planktonic cells.

Bacteria grow preferentially attached to surfaces embedded in an exopolysaccharide matrix to form biofilms. In this mode of growth, bacteria often show reduced susceptibility to antimicrobials. The aim of this study was to investigate whether the combination of NaF and the detergent sodium lauryl sulphate (SLS) could result in additive effects on acid formation by planktonic and biofilm cells, as well as on extracellular polysaccharide formation. An additive inhibitory effect on Streptococcus mutans acid formation was observed, both in planktonic and biofilm cells. In dental biofilms, SLS alone and in combination with NaF reduced acid formation. Extracellular polysaccharide formation by S. mutans and saliva was reduced by SLS alone and in combination with NaF. In dentifrices and mouthrinse solutions, NaF and SLS are often present in combination. It remains to be determined whether an additive effect on acid formation may also occur in dental biofilms under different concentrations from those used in the present study, and whether the effects may be selective for certain bacterial species.

Adolescent↗

PubMed2004

Combined effect of SLS and (SBE)(7M)-beta-CD on the solubilization of NSC-639829.

Complexation and micellization are two effective ways of solubilizing drugs. In this study, the combined effect of surfactant and complexant on the solubilization of a poorly water soluble compound (NSC-639829) is investigated. With increasing concentration of sodium lauryl sulphate (SLS) in solutions of fixed concentration of (SBE)(7M)-beta-CD, the total solubility of the drug decreases linearly, reaches a minimum and then increases linearly. At each minimum, the molar ratio of SLS to (SBE)(7M)-beta-CD is close to unity. The above observation is attributed to the fact that the surfactant molecule competes with the drug to "fit" in the non-polar cyclodextrin cavity. The surfactant depletes cyclodextrin to form a 1:1 complex. Once the concentration of free SLS reaches the CMC, it starts forming micelles and hence, solubilizes the drug. A slight decrease of the solubilizing power is noticed in the presence of SLS/(SBE)(7M)-beta-CD complex. The combined use of two solubilizing agents, a surfactant and a complexant, results in a much lower solubility than when either one is used alone at the same concentration. The surfactant molecule acts as a competitive inhibitor in the solubilization of the drug by the complexant. Similarly the complexant "pulls" the surfactant out of solution, making it unavailable for solubilizing the drug.

Chemistry, Pharmaceutical↗

PubMedDate not supplied

Gene expression analysis of EpiDerm following exposure to SLS using cDNA microarrays.

There is a need to investigate the mechanistic basis of the human skin irritation response if relevant in vitro test systems for the predictive identification of skin irritation hazards are to be developed. Recent progress in genomics technologies mean that tools for the identification and investigation of important biochemical events in the processes of skin irritation are now available. The aim of this work was to identify genes (for further mechanistic investigation) which may be regulated in response to skin irritation, following exposure of the EpiDerm skin model to the known skin irritant sodium lauryl sulphate (SLS). EpiDerm cultures were treated in triplicate with a non-cytotoxic dose of SLS (0.1 mg/ml, as determined by the MTT assay and histological examination) for 15 min, 30 min, 1 h, 2 h, 3 h, 4 h and 24 h. Total RNA was extracted from the pooled EpiDerm cultures and used to probe Atlas human arrays (Clontech) covering approximately 3600 genes. Preliminary data indicated an up-regulation at early time points (15-30 min) of a number of genes involved in transportation (e.g. the sodium and chloride dependent taurine transporter) and receptors (e.g. ZAP70 and protocadherin 42 precursor). The gene encoding the UV excision repair protein and other DNA repair genes (e.g. DNA-directed RNA polymerase II) were up-regulated after 1-3 h, along with TGF beta 3 and other tumour suppressors, which play a role in cellular development and wound healing. At the later time points of 4-24 h, genes involved in protein translation (e.g. Cathepsin D receptor) and metabolism (e.g. CYP27A) were up-regulated. In addition, a number of genes were down-regulated in response to treatment with SLS, although these followed less of a time dependent pattern. These results indicate the differential regulation of a number of genes in response to treatment with SLS, some of which may provide additional clues to the molecular events underpinning the irritation response to this particular surfactant and possibly to other chemical irritants.

Animal Testing Alternatives↗

PubMed2004

Influence of a SLS-containing dentifrice on the anti-plaque efficacy of a chlorhexidine mouthrinse.

BACKGROUND: Chlorhexidine (CHX) and sodium lauryl sulphate (SLS), the most widely used detergent in dentifrice, may counteract. Consequently, studies about this interaction suggested that care is required when combining both these compounds, even when they are introduced separately into the oral cavity. The purpose of the present study was to investigate the effect of toothbrushing with a SLS-containing dentifrice in one jaw, on the plaque inhibition of a CHX mouthrinse in the opposite jaw during a 4-day study period. METHODS: The study was an examiner-blind, randomised two-cell, crossover design. It used a 4-day plaque accumulation model to compare two different oral hygiene regimens with a washout period of 17 days. Sixteen healthy volunteers were enrolled in the study and received a thorough dental prophylaxis at the beginning of each 4-day test period. One jaw (upper or lower) was randomly assigned as the "study" jaw. The opposite jaw was assigned as the "dentifrice" jaw and served only to introduce the effect of brushing with a dentifrice in the study model. Two oral hygiene regimens were evaluated. During one randomly assigned test period, the "dentifrice" jaw was treated by toothbrushing with a 1.5% SLS-containing dentifrice and rinsed together with the "study" jaw with 0.2% CHX, thus forming regimen 1. As a control during the other test period, both the "dentifrice" jaw and "study" jaw were only rinsed with 0.2% CHX, forming regimen 2. No other oral hygiene methods were allowed. After 4 days of undisturbed plaque accumulation, the amount of plaque was evaluated (Silness & Löe 1964). The "study" jaw was used to study the effect of the two regimens on the level of plaque accumulation at the end of the 4-day period. RESULTS: The overall plaque index was 0.36 for regimen 1 and 0.34 for regimen 2. There was no significant difference in plaque accumulation between the two regimens. CONCLUSIONS: Within the limitations of the present study design, it can be concluded that ordinary brushing with a 1.5% SLS-containing dentifrice (Colgate Bi-Fluor), followed by rinsing with water does not appear to reduce the level of plaque inhibition offered by a post-brushing CHX rinse.

Adult↗

PubMed2004

Objective interpretation of severity of SLS induced edema by stereoimaging.

BACKGROUND: In the evaluation of the severity of skin inflammations, visual scoring system is widely being used as a subjective method. However, it is well known that interobserver variations occur even between the interpretations of experienced dermatologists. OBJECTIVE: To develop a new objective and quantitative method for the evaluation of skin surface contours and for the assessment of severity in SLS-induced edema, a new investigatory tool based on the concept of "stereoimaging" was studied. Differences between binocular images were used by a stereoimage optical topometer (SOT) system capable of calculating skin surface topographic information, which was then used to produce a three-dimensional image. METHODS: We compared the results obtained by SOT with a visual scoring system after applying sodium lauryl sulfate (SLS) to skin. The degree of edema was assessed qualitatively by visual scoring (0: none, 1: mild edema, 2: moderate edema, 3: severe edema). To quantify the severity, five three-dimensional parameters (S(a), S(z), SL, SA and SV) were used in the SOT analysis. RESULTS: The means of these five parameters increased significantly in visual grade 1+ compared to visual grade 0 and the means of the five parameters decreased significantly and proportionally as the visual grades increased from 1+ to 3+. A highly significant correlation was found to exist between the visual scoring results and the five SOT parameters. CONCLUSION: SOT can be used to evaluate the severity of SLS-induced edema objectively and can be extensively applied to evaluate the degree of severity in other inflammatory skin conditions.

Adult↗

PubMed2005

Induction of a hardening phenomenon by repeated application of SLS: analysis of lipid changes in the stratum corneum.

Adaptation of the skin to repeated influence of exogenous irritants is called the hardening phenomenon. We investigated the stratum corneum lipid composition before and after induction of a hardening phenomenon. Irritant contact dermatitis was induced in 23 non-atopic volunteers by repeated occlusive application of 0.5% sodium lauryl sulfate (SLS) over 3 weeks. At 3, 6 and 9 weeks after irritation, the SLS responses of pre-irritated skin and normal skin were compared. The horny layer lipid composition (ceramides 1-7, cholesterol and free fatty acids) was assessed before irritation and 3, 6 and 9 weeks after irritation. During the first 2 weeks of irritation the transepidermal water loss increased continuously and seemed to decrease during the third week (effect of adaptation). The barrier function of pre-irritated sites was more stable to SLS challenge. Three weeks after irritation, there was a significant increase of ceramide 1 (p<0.001). The only volunteer without hardening phenomenon showed no increase of ceramide 1. Ceramide 1 seems to play a key role as a protection mechanism against repeated irritation.

Administration, Cutaneous↗

PubMed1997

Atomic force microscopy of collagen molecules. Surface morphology of segment-long-spacing (SLS) crystallites of collagen.

Three-dimensional structures of laterally aggregated bundles of collagen molecules, segment-long-spacing (SLS) crystallites, were imaged by atomic force microscopy (AFM) in atmosphere. The overall image of the type I collagen SLS in a height-amplified mode was semi-cylindrical, approximately 300 nm in length, with two bands of elevation near both N- and C- ends of the molecule. Its 'cross-sectional' profile (across the molecular axis) was a smooth arch. The 'axial' profile (along the molecular axis) had two prominent peaks approximately 250 nm apart, corresponding to the two bands of elevation. There were several minor peaks between these two prominent peaks. The elevation near both ends may be due to the presence of covalently bound sugars near both N- and C- ends of the helical part of type I collagen alpha chains. The AFM images of SLS presented here indicate that the type I collagen molecule is not uniform in diameter and has two bulged parts within its triple helix.

Animals↗

PubMed1997

Guidelines on sodium lauryl sulfate (SLS) exposure tests. A report from the Standardization Group of the European Society of Contact Dermatitis.

This report reviews the clinical and histopathological reactions caused by sodium lauryl sulfate (SLS), and the non-invasive methods that can characterize these reactions. Furthermore, SLS exposure techniques and factors that may influence the outcome of these exposures are discussed. Finally, guidelines are introduced for each exposure technique in order to have a uniform approach to SLS testing in man. Since different study aims warrant different testing conditions, we have proposed 2 categories, namely susceptibility testing and provocative testing, tailored to the aim with which the study is performed.

Dermatitis, Contact↗

PubMed1998

Clinical morphology of sodium lauryl sulfate (SLS) and nonanoic acid (NAA) irritant patch test reactions at 48 h and 96 h in 152 subjects.

In this study of 152 women, comparison of patch test responses between 2 irritants over 96 h at 2 symmetrical anatomical sites is studied. 2 irritants, each at 4 different concentrations (nonanoic acid (NAA) 80%, 40%, 20%, 10%; sodium lauryl sulfate (SLS) 3%, 2%, 1% and 0.5%) and using propan-1ol and 'water for injection' as the respective controls, were placed as 15 microl aliquots, soaked onto filter paper discs in Finn Chambers, on the volunteer's left and right lower back. The patches were removed at 47, and read at 48 and 96 h. Irritant reactions were evaluated for erythema and surface changes by degree and area affected. Statistical analysis of the results showed that erythema decreased with time for all concentrations of NAA, and at higher concentrations for SLS. Surface changes increased with time for SLS and at higher concentrations of NAA. There was no statistically significant difference comparing left and right sides. Traditionally in patch testing, reactions which fade after 48 h have been regarded as irritant rather than allergic. This study refutes that assumption. Data from our left to right comparisons, made in the same individuals at the same time, show that irritant reactions may be more reproducible than previously appreciated.

Adolescent↗

PubMed2006

The development and validation of the Self-directed Learning Scales (SLS).

This article describes the development and validation of the Self-directed Learning Scales (SLS) using data from 14,846 secondary students. Self-directed learning refers to a process whereby the learner consciously and actively directs his/her actions in the learning process. The SLS comprised a battery of subscales measuring students' goal setting, planning, academic motivation, academic self-efficacy, inquiry and information processing, strategic help-seeking, management of learning resources, and self-monitoring. Rasch analysis following factor analyses provided evidence in support of the validity of SLS for use with secondary students. Two original subscales were merged with other subscales on the basis of the analyses, resulting in 19 subscales with strong psychometric properties in the Self-directed Learning Scales.

Humans↗

PubMed2005

Surfactant/nonionic copolymer interaction: a SLS, DLS, ITC, and NMR investigation.

The interactions between an oxyphenylethylene-oxyethylene nonionic diblock copolymer with the anionic surfactant sodium dodecyl sulfate (SDS) have been studied in dilute aqueous solutions by static and dynamic light scattering (SLS and DLS, respectively), isothermal titration calorimetry (ITC), and 13C and self-diffusion nuclear magnetic resonance techniques. The studied copolymer, S20E67, where S denotes the hydrophobic styrene oxide unit and E the hydrophilic oxyethylene unit, forms micelles of 15.6 nm at 25 degrees C, whose core is formed by the styrene oxide chains surrounded by a water swollen polyoxyethylene corona. The S20E67/SDS system has been investigated at a copolymer concentration of 2.5 g dm(-3), for which the copolymer is fully micellized, and with varying surfactant concentration up to approximately 0.15 M. When SDS is added to the solution, two different types of complexes are observed at various surfactant concentrations. From SLS and DLS it can be seen that, at low SDS concentrations, a copolymer-rich surfactant mixed micelle or complex is formed after association of SDS molecules to block copolymer micelles. These interactions give rise to a strong decrease in both light scattering intensity and hydrodynamic radius of the mixed micelles, which has been ascribed to an effective reduction of the complex size, and also an effect arising from the increasing electrostatic repulsion of charged surfactant-copolymer micelles. At higher surfactant concentrations, the copolymer-rich surfactant micelles progressively are destroyed to give surfactant-rich-copolymer micelles, which would be formed by a surfactant micelle bound to one or very few copolymer unimers. ITC data seem to confirm the results of light scattering, showing the dehydration and rehydration processes accompanying the formation and subsequent destruction of the copolymer-rich surfactant mixed micelles. The extent of interaction between the copolymer and the surfactant is seen to involve as much as carbon 3 (C3) of the SDS molecule. Self-diffusion coefficients corroborated light scattering data.

Journal Article↗

PubMed2001

Pathological findings in cumulative irritation induced by SLS and croton oil in hairless mice.

It is known that the pathological features of acute irritant contact dermatitis are specific according to the irritant. However, in chronic irritant contact dermatitis, it is not clear whether specific patterns exist. To investigate whether the specific pathology of acute irritant contact dermatitis is sustained in chronic irritant contact dermatitis, sodium lauryl sulfate (SLS) and croton oil were applied 3x a week for 2 weeks on the dorsal skin of hairless mice using Finn Chambers. The pathologic changes induced by irritants at various concentrations were evaluated using H&E and Luna's staining, as well as immunohistochemistry for 5-bromo-2-deoxyuridine (BrdU), keratin 6 and loricrin. Our results showed that epidermal hyperplasia and inflammatory infiltration were relatively marked in the groups treated with higher concentrations of irritants. These features were more prominent in the 1% croton oil treated group than in the 0.25% SLS treated group. However, lower concentrations of irritants resulted in very similar histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical. Our results suggest that the histological responses to irritants vary with concentration in cumulative irritation, as in acute irritation, but repetitive mild irritation may evoke common histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical used.

Animals↗

PubMed2002

Clinical manifestations of hand eczema compared by etiologic classification and irritation reactivity to SLS.

Hand eczema is a common skin disease. Because of its variable etiologies and clinical manifestations, it is difficult to determine the etiology from the clinical manifestation. Among the contact allergens, nickel is the most common. Patients with hand eczema and a nickel allergy have a poorer prognosis than patients without a nickel allergy. The reason is still uncertain; suggestions include persistent exposure to nickel or a weak skin barrier. The purpose of our study was to identify the characteristic clinical manifestations by etiology and to compare the skin barrier state between patients with nickel allergies and those without them. Ninety-three patients were classified into 4 types; irritation contact type, allergic contact type, atopic type and mixed type. After the sodium lauryl sulfate (SLS) test to compare the skin barrier state, visual score and transepidermal water loss (TEWL) were measured and analyzed statistically. From this study, it was not possible to ascertain a statistical difference, however a few characteristic clinical manifestations according to etiology can be stated. There was no difference in the visual scoring system or the TEWL after the SLS irritation test between the nickel-allergy group and the non-allergy group. Therefore, we believe that the poor prognosis of hand eczema with nickel allergy may be due to the nickel allergy itself rather than skin barrier state.

Adolescent↗

PubMed1997

Skin roughness is negatively correlated to irritation with DMSO, but not with NaOH and SLS.

While many endogenous and exogenous factors have been found to influence skin irritant reactivity, the role of skin roughness in irritation has not yet been studied. In this study we measured skin roughness by visiometry and performed irritation tests on the flexural side of the forearm with sodium hydroxide (NaOH), sodium lauryl sulphate (SLS) and dimethyl sulfoxide (DMSO) in two different concentrations in a population of 151 volunteers between 15 and 25 years of age. The results showed a significant negative correlation between most roughness parameters and DMSO irritation. The correlation between roughness parameters and irritation tests with SLS and NaOH was not significant. We conclude that smoother skin is more prone to DMSO irritation than rougher skin and that this may be due to differences in percutaneous penetration of the compound.

Adolescent↗

PubMed1994

Development studies of Aurelia (jellyfish) ephyrae which developed during the SLS-1 mission.

Aurelia polyps (scyphistomae) and ephyrae were exposed to microgravity for nine days aboard the space shuttle during the SLS-1 mission. During strobilation, polyps segment transversely and each segment develops into an ephyra. Polyps were induced to strobilate at 28 degrees C, using iodine or thyroxine, at L(Launch)-48h, L-24h, and L+8h. Ephyrae developed in the groups tested in space and on Earth. The number of ephyrae formed per polyp was slightly higher in the L+8h groups as compared with those induced at L-24h and L-48h. On Earth, iodine is used by jellyfish to synthesize jellyfish-thyroxine (Jf T4), needed for ephyra production. Since iodine-treated polyps strobilated and formed ephyrae in space, it appears that jellyfish can synthesize Jf-T4 in space. Indeed, two groups of polyps not given inducer formed ephyrae [correction of ephryae] in space, presumably due to enhanced Jf-T4 synthesis, utilization or accumulation. Some ephyrae that formed in space were also fixed in space on Mission Day (MD) 8; others were fixed post-flight. Examination of living ephyrae with the light microscope and fixed ones with the Scanning and Transmission Electron Microscopes revealed that those which developed in space were morphologically very similar to those which developed on Earth. Quantitation of arm numbers determined that there were no significant differences between space and Earth-developed ephyrae. Pulsing abnormalities, however, were found in greater numbers (18.3%) in space-developed ephyrae than in Earth-developed controls (2.9%). These abnormalities suggest abnormal development of the graviceptors, the neuromuscular system, or a defect in the integration between these systems in apparently microgravity-sensitive animals.

Animals↗

PubMed2004

Vehicle-controlled effect of urea on normal and SLS-irritated skin.

It is known that, depending on the concentration, treatment with urea could improve skin barrier function, despite its penetration-enhancing properties. This controversial skin effect of urea has been explored systematically in this study in terms of the effect of vehicle on the performance of urea. In the first part, a series of four semi-solid emulsions with 5% (w/w) urea, varying in the type of emulsion, nature of emulsifier and polarity of oil ingredients, have been evaluated with regard to their skin hydrating and transepidermal water loss (TEWL)-modifying properties. Placebo samples were tested alongside the urea-containing ones. Two best performing moisturisers from the above were chosen for the second part of the study, in which sodium lauryl sulphate (SLS)-irritated skin was treated with both placebo and urea-containing samples. In addition to TEWL and skin hydration level, the erythema index (EI) was measured before, during and after the treatment. The results have shown that barrier-improving and hydrating abilities of urea are bi-directional and dependent on both the type of vehicle used for its delivery and the state of skin.

Adult↗