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PubMed1994

Electrical impedance compared with other non-invasive bioengineering techniques and visual scoring for detection of irritation in human skin.

A new, non-invasive device, which enables local measurements of electrical impedance to a controlled depth, has been used to evaluate the degree of irritation in human skin. The results have been compared with those obtained using other non-invasive techniques, i.e. with transepidermal water loss (TEWL), electrical capacitance moist measurement (ECM), laser-Doppler flowmetry (LDF), and visual scoring. Sodium lauryl sulphate solutions (0.1-5.0%), and a blank, were applied in Finn Chambers for 24 h on the volar forearm of 10 healthy volunteers. Values were recorded before application of the test chambers, and at 1 h, 24 h, 1 week and 2 weeks after removal. Thus, both the degree of initial damage and the healing process were monitored. There was close agreement among values obtained using electrical impedance, TEWL and visual readings. Results obtained using ECM and LDF were not consistent with the other three methods. In evaluating irritation of the skin, the practical situation may influence the choice of bioengineering tools. In most circumstances, a combination of methods would be preferable.

Adult↗
PubMed1999

Correlation between the greasiness and the plasticizing effect of moisturizers.

Moisturizers are used as cosmetics and as adjuvant therapy in dermatology. The strength or relative efficacy of moisturizers is poorly described and thus advising patients is difficult. It has been suggested that lipidization of the skin by moisturizers and the changes in skin mechanics following the application of a moisturizer may be useful measures of outcome. The aim of this study is to describe the relative efficacy of 5 different moisturizers, a barrier cream and a gel in terms of changes in skin mechanics and electrical capacitance before and after application. Assessment of the greasiness or absorption of the cream was made by standardized blotting of unabsorbed residue. Lipid-rich creams (Vaseline, Locobase and Decubal creme) caused increased skin distensibility, while no differences were found in hysteresis changes. In contrast, the relative efficacy in increasing skin capacitance was significantly greater in the moisturizers with a lower lipid content (Clinique, Nivea) and gel. The results suggest that lipidization is of major importance to the plasticity of the skin. When moisturizers are used to improve skin plasticity it is suggested that lipid-rich formulations be used. Cosmetically more acceptable creams and gel were however better at increasing skin capacitance which has been interpreted as a measure of skin hydration. The difference may reflect a design adaptation of these creams to a specific outcome measure and our results raise the question of appropriate outcome measures and our results raise the question of appropriate outcome measures in future moisturizer studies.

Adult↗
PubMed1984

Electrophysiology of Necturus urinary bladder: II. Time-dependent current-voltage relations of the basolateral membranes.

As reported previously (S.R. Thomas et al., J. Membrane Biol. 73:157-175, 1983) the current-voltage (I-V) relations of the Na-entry step across the apical membrane of short-circuited Necturus urinary bladder in the presence of varying mucosal Na concentrations are (i) time-independent between 20-90 msec and (ii) conform to the Goldman-Hodgkin-Katz constant field flux equation for a single cation over a wide range of voltages. In contrast, the I-V relations of the basolateral membrane under these conditions are (i) essentially linear between the steady-state, short-circuited condition and the reversal potential (Es); and (ii) are decidedly time-dependent with Es increasing and the slope conductance, gs, decreasing between 20 and 90 msec after displacing the transepithelial electrical potential difference. Evidence is presented that this time-dependence cannot be attributed entirely to the electrical capacitance of the tissue. The values of gs determined at 20 msec are linear functions of the short-circuit current, Isc, confirming the relations reported previously, which were obtained using a more indirect approach. The values of Es determined at 20 msec are significantly lower than any reasonable estimate of the electromotive force for K across the basolateral membrane, indicating that this barrier possesses a significant conductance to other ions which may exceed that to K. In addition, these values increase linearly with decreasing Isc and approach the value of the electrical potential difference across the basolateral membrane observed when Na entry across the apical membrane is blocked with amiloride or when Na is removed from the mucosal solution. A possible explanation for the time-dependence of Es and gs is offered and the implications of these findings regarding the interpretation of previous microelectrophysiologic studies of epithelia are discussed.

Animals↗
PubMed2005

[In vivo impedance of the aerial organs of some mono- and dicotyledonous plants].

In vivo impedance of the aerial organs of some mono- and dicotyledonous plants. We measure in this paper the electrical capacitance and resistance of aerial organs of some plants, grown in the laboratory (sunflower, pumpkin, and maize, of different ages) or bought at the market (sorrel), in a range of 34 frequencies, from 40 Hz to 100 kHz. The electrospectrometric curves of the leaves aged 14 days of the dicotyledoneous studied are close to each other.

Electric Impedance↗
PubMed2001

Effect of different moisturizers on SLS-irritated human skin.

Moisturizers are widely used to treat irritant contact dermatitis (ICD). Their use is, however, not well-documented and standardized models for testing skin care products are needed to acquire documentation of their efficacy. The present study was undertaken to evaluate the effect of 6 commonly-used moisturizers on the recovery of irritated human skin. No commercial interests were involved in the study. 36 healthy volunteers had patch tests with SLS 0.5% applied on their forearms/upper arms for 24 h. After irritation of the skin, all volunteers had a moisturizer applied on one forearm/upper arm, respectively, 3 x daily for the following 5 days. The other forearm/upper arm served as an untreated control. Each moisturizer was tested on 12 volunteers and each volunteer tested 2 moisturizers at the same time. Evaluation was done on days 1, 3 and 8 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry, DermaSpectrometry and clinical scoring. All 6 moisturizers were found to accelerate regeneration of the skin barrier function when compared to irritated non-treated skin. The most lipid-rich moisturizers improved barrier restoration more rapidly than the less lipid-rich moisturizers. We suggest this experimental model for further moisturizer efficacy testing.

Dermatitis, Contact↗
PubMed1977

Control and monitoring system for clinically employed pneumatic blood pumps.

Instantaneous position of the flexing member in pneumatic blood pumps is monitored on-line by measuring the electrical capacitance across the gas space within the pump. Monitor output is utilized in closed-loop pump control and for automatic pump shutdown in response to operational abnormalities. Thus, safety and efficacy are enhanced through operational optimization, automatic safety features, and facilitated evaluation.

Assisted Circulation↗
PubMed1978

The mechanism of anaesthesia: a new hypothesis based on the effects on electrical properties of a model membrane: preliminary studies.

Changes induced by inhalational anaesthetic agents were investigated in a simple membrane model. All the agents tested increased the membrane's electrical capacitance and conductance linearly, proportional to concentration and potency, and decreased its dialectric strength independently of concentration. When protein was substituted for lipid, the same agents had no significant effect on capacitance, conductance, or dielectric strength. Based on these findings, the following hypothesis is presented. Anaesthetic agents exert their influence on the lipid portion of nerve membranes. They enhance excitability by reducing the dielectric strength of the membrane and depress excitability by increasing the membrane's dielectric constant and passive conductance. The degree of excitability or narcosis at any instant depends upon the relative magnitude of these opposing effects.

Anesthesia, Inhalation↗
PubMed1997

Effect of water on experimentally irritated human skin.

The effect of water on experimentally irritated skin was studied in 21 healthy volunteers to evaluate water as a primary irritant. Volunteers had one hand exposed to water 15 min twice daily for 2 weeks, while the other hand served as control. The transepidermal water loss and the electrical capacitance were measured reflecting skin barrier function and skin hydration, respectively. The blood flow and the erythema index were measured reflecting inflammation. Water did not significantly influence transepidermal water loss, but caused a significant increase in skin blood flow, as evaluated by laser Doppler flowmetry. It is concluded that exposure to water 30 min daily for 2 weeks does not influence the barrier of previously subclinically irritated skin. It does, however, elicit an increase in skin blood flow.

Adult↗
PubMed1996

Effect of glove occlusion on human skin. (I). short-term experimental exposure.

UNLABELLED: Skin barrier function was studied after use of occlusive gloves on normal and compromised skin. 2 studies were performed (Study A and B), and the effects were evaluated by non-invasive methods. Participants in the studies were instructed to wear an occlusive glove on one hand, while the other hand served as control. The gloves used were hypoallergenic, non-latex. Study A: 20 volunteers wore a glove on normal skin 6 h/day for 3 days. Study B: 20 volunteers wore a glove on sodium lauryl sulfate(SLS)-compromised skin 6 h/day for 3 days. Skin barrier function was evaluated by measurement of transepidermal water loss (TEWL) (Evaporimeter), skin hydration by electrical capacitance (Corneometer) and inflammation was evaluated by erythema index (DermaSpectrometer). RESULTS: Study A. Glove occlusion on normal skin 6 h/day for 3 days caused no significant influence on the water barrier function. Study B: Glove occlusion on SLS-compromised skin for the same period of time had a significantly negative effect on the water barrier function. It is concluded that occlusion may be an additional factor in the pathogenesis of cumulative irritant contact dermatitis.

Adult↗
PubMed1996

Interaction of adrenocorticotropin-(1-24)-tetracosapeptide with lipid bilayers.

The interaction of the peptide hormone adrenocorticotropin with solvent-free planar lipid bilayers (BLM) and liposomes was studied by measurements of elasticity modulus perpendicular to the plane of the membrane (E perpendicular, measured by electrostriction), surface potential difference (delta phi m), electrical capacitance, capacitance relaxation following a voltage jump (yielding relaxation times for molecular dipoles or dipolar domains), and fluorescence polarization. Addition of the 6-fold positively charged peptide to one side of the membrane leads to a more positive membrane surface potential, an increase of BLM capacitance, a decrease of elasticity modulus, and faster relaxation time constants. This also caused a decrease of DPH fluorescence anisotropy of the liposome suspension modified by fluorescent dye DPH. Mixed BLM of palmitoyl-oleoyl-phosphatidylcholine (POPC)+soybean phosphatidylcholine (SBPC) (10:1 w/w), which carry a negative surface charge, exhibit considerably larger changes than electroneutral POPC membranes. Our results confirm that ACTH1-24 binds to BLM and interacts with the hydrophobic part of the bilayer.

Cosyntropin↗
PubMed1995

Irritant effects of a detergent in wash and chamber tests.

Irritant properties of detergents can be tested by using patch and chamber tests and various kinds of use tests. The aim of the present study was to compare the results of use and 12 mm Finn Chamber tests. Study subjects (10 atopic and 11 non-atopic medical students) washed the outer aspect of 1 upper arm with liquid detergent for 1 minute 2 x daily for 1 week. 48-h chamber test with 5 concentrations of the same detergent in water were concurrently applied to upper back skin. Transepidermal water loss (TEWL), electrical capacitance and skin blood flow were measured to quantify reactions on days 0, 2, 5 and 7. Irritant contact dermatitis developed equally in atopics and non-atopics in the wash test, whereas in the chamber test with a 10% aq. solution of the detergent, increase in TEWL was significantly higher in atopics than in non-atopics. The chamber test results thus predicted poorly the result of the wash test. This might indicate that the wash test and the chamber test measure different aspects of skin barrier function.

Adult↗
PubMed2002

Evaluation of skin surface hydration in Korean psoriasis patients: a possible factor influencing psoriasis.

Psoriasis is recognized as a chronic, relapsing disorder of the skin, and its clinical course is influenced by various environmental factors. However, only a few articles have addressed the effect of low epidermal hydration status as an exacerbating factor of psoriasis. Our study was performed to investigate the relationship between subjective assessment and quantified data regarding dryness parameters in psoriasis patients. Seventy psoriasis patients were enrolled in our study. Subjective assessments were undertaken by evaluating the extent of involvement, erythema, scale and infiltration of individual lesions. Functional status of stratum corneum was evaluated by measuring electrical capacitance and conductance of the lesional and uninvolved skin of psoriatic patients. In addition, measurement of trans-epidermal water loss was performed. The results showed poor hydration status and barrier function in involved psoriatic epidermis compared with the uninvolved skin. Subjective assessment showed fairly good correlation with the quantified values. In conclusion, the degree of dryness in psoriatic skin lesions--which we presume to be one of the aggravating factors of psoriasis--seemed to be related to disease severity.

Adult↗
PubMed1996

Effect of glove occlusion on human skin (II). Long-term experimental exposure.

Gloves are indispensable in many occupations. Irritant skin reactions from gloves have, however, been reported. In the present study, the effect of long-term glove occlusion on normal skin (6 h/day for 14 days) was studied and, in addition, the effect of a cotton glove worn under the occlusive glove was also studied. 2 studies were performed (studies A and B). Study A: 19 volunteers wore an occlusive glove on normal skin 6 h/day for 14 days. They wore the glove on one hand only, while the other hand served as control. Study B: 18 volunteers wore occlusive gloves on both hands on normal skin. A cotton glove was worn under the occlusive glove on either the left or the right hand. Skin barrier function was evaluated by measurement of transepidermal water loss (TEWL) (Evaporimeter), skin hydration by electrical capacitance (Corneometer) and inflammation by erythema index (Derma-Spectrometer). The gloves used were hypoallergenic non-latex gloves. Results. Study A: glove occlusive on normal skin 6 h/day for 14 days had a significant negative effect on skin barrier function, as measured by TEWL. Study B: the negative effect on skin barrier function from occlusive gloves was prevented by the use of a cotton glove. It is concluded that gloves may be a substantial factor in the pathogenesis of cumulative irritant contact dermatitis, and that recommendations as to their use are important.

Adult↗
PubMed1992

Comparison of 9-aminoacridine and atebrine induced changes in optical, electrical and mechanical characteristics of lipid bilayers.

The effects of fluorescent probes 9-aminoacridine (9AA) and atebrine (AT) on physical properties of liposomes and planar bilayer lipid membranes (BLM) were studied. The method of fluorescence spectroscopy and the electrostriction method based on measurement of higher current harmonics were used. At low concentrations (10(-5)-5 x 10(-5) mol/l), 9AA increased fluorescence intensity, while in liposomes from soybean phosphatidylcholine fluorescence quenching occurred at higher probe concentration. Fluorescence quenching occurred over the entire concentration range tested (10(-5)-10(-4) mol/l) in liposomes made from a mixture of egg phosphatidylcholine and cardiolipin. In contrast to 9AA, AT, thanks to its hydrophobic chain, penetrates deeper into the hydrophobic membrane moiety; thus, immobilization of the molecule and an increase in fluorescence intensity was always observed. Probes adsorbed to membranes, leaving their electric capacitance effectively unchanged. Adsorption of charged dye particles induced small changes in transmembrane potential. In the presence of 10(-5) mol/l AT, the modulus of elasticity E perpendicular increased somewhat for soft membranes (E perpendicular approximately 2.5 x 10(7) Pa), whereas it decreased for hard membranes (E perpendicular approximately 5 x 10(7) Pa). pH gradient present on the membrane affected the ability of the dyes to incorporate into the membranes. Our results provide evidence against the proposed model of the quenching mechanism introduced by Rottenberg and Lee (1975).

Aminacrine↗
PubMed1999

Comparison between 2 test models in evaluating the effect of a moisturizer on irritated human skin.

The purpose of the present study was to compare 2 experimental models of moisturizer efficacy on the recovery of irritated skin on the hands and the volar forearms. 12 healthy volunteers had their hands immersed in sodium lauryl sulfate (SLS) 10 min 2x daily for 2 days, and at the same time the volunteers had patch tests with SLS (0.125%, 0.25% and 0.5%) applied on their forearms for 24 h. After irritation of the skin, the volunteers had a moisturizer applied on one arm/hand 3x daily for the following 9 days. The other arm/hand served as untreated control. Evaluation was done on days (D) 1, 3, 5, 8 and 12 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry and DermaSpectrometry. Both models were found useful, and the moisturizer was found to accelerate regeneration of the skin barrier function in both the hands (D8, p<0.05) and the volar forearms (0.5% SLS, D5 and D8, p<0.01). When the forearm model is used in the present set-up, a relatively high concentration of SLS (>0.25%) should be used and evaluation measurements are best performed on D5-D8. The forearm model proved reliable and easy to handle and we suggest that this model is used in future studies on moisturizer evaluation.

Adult↗
PubMed1999

Effects of ELF capacitively coupled weak electric fields on metabolism of 6B1 cells.

In this study, we adopted several methods of MTT colorimetry, DAPI fluorimetry and ELISA to study the effects of extremely low frequency (ELF) capacitively coupled electric fields (EFs) on the metabolism of 6B1 cells. The result shows that 50 mV cm(-1) ELF EF (10-100 Hz) has no significant effect on proliferation, DNA synthesis and activity of succinate dehydrogenase of 6B1 cells, indicating that the effect of ELF (10-100 Hz) EF on the metabolism of 6B1 cells is not obvious. However, 50 mV cm(-1), 50 Hz EF significantly promotes the HBs-Ab (Hepatitis B surface antibody) secretion of 6B1 cells, implying that under this situation, EF has some distinctive effect on the outerface of 6B1 cell membrane.

Cell Division↗
PubMed1992

Determination of electric field threshold for electrofusion of erythrocyte ghosts. Comparison of pulse-first and contact-first protocols.

Rabbit erythrocyte ghosts were fused by means of electric pulses to determine the electrofusion thresholds for these membranes. Two protocols were used to investigate fusion events: contact-first, and pulse-first. Electrical capacitance discharge (CD) pulses were used to induce fusion. Plots of fusion yield vs peak field strength yielded curves that intersected the field strength axis at positive values (pseudothresholds) which depended on the protocol and decay half time of the pulses. It was found that plots of pseudothreshold vs reciprocal half time were linear for each protocol; when extrapolated to reciprocal half time = 0 (i.e., t----infinity), these lines intersected the ordinate at values of the field strength considered to be the true electrofusion thresholds. In this fashion, the contact-first protocol gave an electrofusion threshold of 46.5 +/- 11.5 V/mm for hemoglobin-free ghosts (white ghosts) and 40.9 +/- 8.8 V/mm for ghosts with fractional hemoglobin (pink ghosts), while the threshold for the pulse-first protocol applied to pink ghosts was determined to be 93.4 +/- 11.0 V/mm. Although the thresholds depended on the electrofusion protocol, plots of critical field strength vs reciprocal time had the same slopes, i.e., approximately 24 Vs/mm. The results suggest that the fusogenic state induced by an electric pulse in either the contact-first protocol or the pulse-first protocol (long-lived fusogenic state) may in fact share a common mechanism, if the two states are not actually identical.

Animals↗
PubMed2001

Assessment of the water content of the stratum corneum using a sorption-desorption test.

BACKGROUND/AIM: Various instruments based on electrical properties of the skin are currently used to assess the stratum corneum (SC) hydration state or water holding capacity. However, no direct relation with the quantity of water measured is provided. The objective of the present study was to calibrate the Corneometer, a device displaying electrical-capacitance-related values (which reflect the skin hydration state), and the amount and behaviour of the water taken up by the outer part of the SC during a sorption-desorption test. METHODS: The experiment was performed on the ventral forearms of 20 healthy volunteers after a rest in an environmentally controlled room. Corneometer and transepidermal water loss (TEWL) values were measured at intervals over the desorption process. The areas under the TEWL-versus-time curve provided the absolute amounts of residual sorbed water. RESULTS: The decrease kinetics of both signals after subtraction of prehydration values were very similar and bi-exponential, both showing a rapid, then a slower phase. The absolute amount of water taken up by the SC (hygroscopicity) and the two desorption rates were obtained. The Corneometer values were mono-exponentially related to the amount of water remaining within the SC. This allowed the in vivo calibration of the Corneometer in terms of absolute amount of water over the desorption range. CONCLUSION: The method may be used to calibrate in vivo other electrical devices aimed at assessing SC hydration during a sorption-desorption test. It may also provide new ways to measure SC water uptake and water holding capacity following application of products.

Absorption↗