Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Electric Capacitance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2005

Inter-instrumental variation of skin capacitance measured with the Corneometer.

BACKGROUND/PURPOSE: Measurement of skin surface and stratum corneum (SC) hydration during clinical and/or experimental trials needs devices with acceptable reproducibility and sensitivity under conditions ranging from increased and normal to low hydration. A previous study comparing Corneometer instruments (European group for Efficacy Measurement of Cosmetics and Other products--EEMCO) used for measurement of electrical capacitance of skin indicated a major difference among Corneometer instruments. The aim of this study was to assess three inter-instrumental similar Corneometer instruments (two pieces of CM820 and one CM810) in normal skin. We named them CM-A(CM820), CM-B(CM820), and CM-C(CM810). METHODS: The hydration state of SC measured as electrical capacitance of six body sites were measured in 53 subjects with three Corneometer instruments. RESULT: We found that the Corneometer instruments displayed close capacitance levels. When one Corneometer was plotted against another the regression line indicated a good correlation among instruments albeit a major and random disagreement could appear in individual sites as an exception. CONCLUSION: Three Corneometer instruments evaluated in this study gave close measurements and correlated well. Nevertheless, pretest validation of instruments should be undertaken in multicenter studies where capacitance data are compared or pooled, and concordance among instruments should be documented prior to study.

Adolescent↗
PubMed1986

Embryonic bone matrix formation is increased after exposure to a low-amplitude capacitively coupled electric field, in vitro.

In order to investigate the mechanism(s) of electric field-stimulated osteogenesis, we have developed an in vitro model in which embryonic chick tibiae have consistently demonstrated increased bone matrix formation in response to a low amplitude (estimated 10(-5) V/m in the serum-free culture medium), capacitively coupled, 10 Hz sinusoidal electric field. Initial applications of this model revealed that 72 h of continuous exposure to the electric field increased tibial collagen production by 29% compared to untreated controls, P less than 0.01. Additional studies further revealed: (a) that when electric field exposure was limited to 30 min/day during the 72 h in vitro incubation, embryonic bone matrix formation was increased by 83%, compared to non-treated controls (P less than 0.001), suggesting an inductive mechanism; (b) that the osteogenic response to electric field exposure in vitro was not unique to embryonic chick tibiae, since a similar response was also seen with newborn mouse calvaria (+133%, P less than 0.02); (c) that electric field-exposure-stimulated chick bone matrix formation was associated with increased bone cell proliferation; and (d) that this mitogenic response to in vitro electric field exposure could also be observed with embryonic chick calvarial cells in monolayer, serum-free cultures.

Animals↗
PubMedDate not supplied

[Formation of stabile cupola-like lipid bilayer membranes with a mobile plateau Gibbs boundary].

Stable bilayer lipid membrane with mobile Platear-Gibbs border have been formed. The predominant condition of the formation is the presence of lipid coverage on the teflon surface near the hole. The formation process includes transformation of the initial planar lipid bilayer into cupola-shaped one by bowing of the lipid bilayer due to hydrostatic pressure, movement of the PGb along the teflon surface. The bilayer area estimated by electric capacitance increases from 0.1 x 10(-8) F to 21 x 10(-8) F. Electric conductance of the lipid bilayer has not changed except for the phase transition and membrane collapse. The electric capacitance of the BLM formed from hydrogenated egg lecithin was changed by cooling between 60 degrees and 40 degrees C with the maximum at about phase transition range. The individual membrane sustains several scannings of the temperature without disruption which is an evidence of the stability of the cupola-shaped membranes.

Electric Conductivity↗
PubMed1995

Use of capacitive coupled electric fields in stress fractures in athletes.

The authors report the results of an open study on the treatment of stress fracture in athletes by capacitive coupling, a bone healing stimulation method promoting bone formation by application of alternating current in the form of a sinusoidal wave. Twenty-five lower-limb (navicular, 2nd and 5th metatarsal, tibia, fibula, and talus) stress fractures in 21 athletes (mean age, 21.8 years old) were treated. The mean stimulation time was 52 days (navicular fractures, 60 days). Twenty-two fractures were healed, 1 was not healed, and 2 were improved. This preliminary report shows that capacitive coupling can be used safely in the treatment of these stress fractures.

Adolescent↗
PubMed1986

Colonic epithelial impedance analysis in a murine model of large-bowel cancer.

Death rates from large-bowel cancer have remained essentially unchanged over the past 40 years because the diagnosis is made late, after the tumor has spread to other sites. This study was undertaken to examine whether alterations in mucosal electrical capacitance precede the development of gross malignancy, since this parameter may reflect functional or structural changes in the colonocyte plasma membrane, which is of importance in the regulation of cell growth. Distal colonic mucosal capacitance was decreased at low frequencies after only four weeks of treatment with the carcinogen dimethylhydrazine in C1 mice. Alterations in electrical capacitance may be a useful marker in identifying patients with a propensity to develop large-bowel cancer.

Animals↗
PubMed1991

Skin physiological changes in employees in the fish processing industry immediately following work. A field study.

In order to explain the complaints of dry skin after work among employees in the fish processing industry, we followed the skin blood flow (SBF), skin surface temperature, transepidermal water loss (TEWL) and electrical capacitance on the volar aspect of the 3rd finger in 10 fillet workers, where measurements were performed just at the end of a working day and during the next hour. The results were compared with 10 normal controls. During work, a low SBF, temperature and TEWL, and a high capacitance were found. After work, the SBF, temperature and TEWL increased to values above normal within 10-15 min, while the electrical capacitance decreased to subnormal values. A positive relation was demonstrated between skin temperature and TEWL, negative relations between temperature and capacitance, and between capacitance and TEWL. Our results in this field study confirm our clinical findings among workers in the fish processing industry: low occurrence of chapping and eczema during work and the development of dry skin after work.

Adult↗
PubMed1996

A method of resolution improvement by the measurement of cell membrane capacitance.

When measuring cell membrane electrical capacitance in whole cell configuration using alternating currents, the resolution decreases with increasing membrane conductance and pipette resistance. Improved resolution was attained by the dual-frequency method which was modified as to control the voltage amplitude of one of the measuring frequencies. A model circuit was developed for the verification of the method. This circuit allows measurement of calibrated capacitance changes even in the range of 5 to 20 fF. Moreover, the method was applied to capacitance measurements on pancreatic exocrine acinar cells. The results of measurements on the model as well as on pancreatic acinar cells are presented. The principle can also be applied to other hardware and software methods for measuring electrical cell membrane parameters.

Animals↗
PubMed1996

Temperature dependency of skin susceptibility to water and detergents.

Exposure to water and detergents is an important factor for development of irritant contact dermatitis. The aim of the present study was to investigate the effect of temperature on the damaging effects of water and detergents on the skin. Twenty healthy volunteers participated in the study. Ten participants had right and left forearms immersed into a detergent (soap) solution for 2 days twice daily for 10 min. Another 10 participants had both forearms immersed into sterile water. Right and left forearms were randomized to immersion into 20 degrees C and 40 degrees C solutions, respectively. Reactions were evaluated clinically, and by measurement of transepidermal water loss, electrical capacitance and erythema. Immersions into 40 degrees C sodium lauryl sulphate solution caused significantly increased transepidermal water loss as compared to immersion into 20 degrees C sodium lauryl sulphate solution. Electrical capacitance and erythema were not significantly influenced by temperature. Immersion into water caused no significant changes in any observed parameter. Water temperature influences the irritant capacity of a detergent. Change of temperature may be a simple but important means for prevention of irritant contact dermatitis.

Adult↗
PubMed1989

Changes in the water holding capacity of psoriatic stratum corneum in vivo.

This study investigated the functional capacity of the stratum corneum of psoriatic skin to bind water in vivo during a relatively long period of time (water holding capacity--WHC). An electrical capacitance test was applied to the psoriatic skin on the elbows, perilesional skin and apparently normal skin of 11 patients and the elbows of 10 controls. Measurements of electrical capacitance were performed using a Corneometer Schwarzhaupt for 25 min. The WHC levels were calculated for this period. Our results demonstrate that the WHC of psoriatic stratum corneum does not differ from controls in the first 10 min. Only after the 20th min do the WHCs differ significantly (p less than 0.02). Despite the biochemical keratin changes in psoriatic plaque, the latter is highly hygroscopic, in particular in the first minute after bathing. Perilesional skin binds water like the stratum corneum of controls, though not beyond the 20th minute after bathing.

Adult↗
PubMed1992

Clinical and non-invasive evaluation of 12% ammonium lactate emulsion for the treatment of dry skin in atopic and non-atopic subjects.

Clinical dryness of the leg skin is a common problem among dermatological patients. The efficacy and safety of 12% ammonium lactate emulsion (Keratisdin) for the treatment of dry skin on the legs of atopic and non-atopic subjects has been assessed by clinical criteria and by five different non-invasive methods. These methods measure biophysical parameters such as electrical capacitance of stratum corneum, skin surface lipids, transepidermal water loss (TEWL), skin surface topography (scanning electron microscopy and image analysis) as well as the biomechanical properties of the skin. Treatment with the test emulsion significantly reduced the severity scores for dryness, desquamation and pruritus when measured 15 days later. All patients tested showed a significant increase in electrical capacitance, skin surface lipids, extensibility and firmness of the skin, and an improvement in the skin barrier function and skin surface topography. This study showed that non-invasive techniques are excellent complementary tools in clinical studies.

Adult↗
PubMed1995

Immediate irritant reactions to benzoic acid are enhanced in washed skin areas.

Factors affecting immediate irritant skin reactions are poorly understood. Our purpose was to study the effect of washing on reactions to benzoic acid, a well-known immediate-type irritant. 12 test subjects washed their left upper arms with a diluted dishwashing liquid 2X daily for 6 days. Benzoic acid in a dilution series was tested on both upper arms on days 0, 3 and 6. The reactions were graded visually, and the blood flow, skin color, transepidermal water loss and electrical capacitance of the test sites were measured. On days 3 and 6, the benzoic acid reactions were stronger on the washed arm than on the control arm. This was clinically visible and was associated with changes in blood flow and skin color measurements. Washing itself did not usually cause visible erythema, but transepidermal water loss increased and electrical capacitance decreased. Low concentrations of irritant substances, such as benzoic acid, may cause clinically relevant reactions in repeatedly washed skin. This should be taken into consideration in assessing product safety in the cosmetic, medical and household chemical industries, and when tests for chemical skin irritancy are designed and the results of such tests interpreted.

Adult↗
PubMed1995

Skin barrier properties in patients with recessive X-linked ichthyosis.

Patients with X-linked recessive ichthyosis (RXLI) were studied as a model of the effect of disturbed epidermal lipid composition on skin barrier function. Thirteen patients with RXLI and 15 age- and sex-matched controls were patch-tested with sodium lauryl sulphate (SLS) 0.5% for 24 h. Basal skin properties and skin response to SLS were studied by measurement of transepidermal water loss (TEWL), electrical capacitance and erythema index. No statistically significant difference in basal TEWL was found between the two groups. The skin response to SLS was found to be statistically significantly increased in controls compared to ichthyosis patients, when evaluated by TEWL. When evaluated by erythema index a statistically significant increase in redness was found in controls, but not in ichthyosis patients. Electrical capacitance, reflecting skin hydration, was significantly reduced in RXLI patients as compared to controls. The water permeability barrier in RXLI patients was not found to be impaired, and skin reactivity was found to be decreased in RXLI patients as compared to controls.

Adult↗
PubMedDate not supplied

Topical sulfamylon reduces engraftment of cultured skin substitutes on athymic mice.

Sulfamylon (mafenide acetate) remains extremely valuable for the control of the bacterial contamination of burn wounds, but it is cytotoxic to cultured keratinocytes used for wound closure. Because composite skin substitutes develop a partial epidermal barrier in vitro, they may hypothetically tolerate the use of topical Sulfamylon. To test this hypothesis, cultured skin substitutes were prepared from cultured human fibroblasts; keratinocytes were attached to these collagen-based substrates, which were grafted to full-thickness wounds in athymic mice (n = 8 per group). Wounds were irrigated twice daily with 5% (wt/vol) Sulfamylon solution or with a formulation of noncytotoxic antimicrobials (0% Sulfamylon). On day 9 after grafting, the wounds were treated with dry dressings and assessed at 4 weeks for expression of human leukocyte antigens-A, B, C and at 2, 3, and 4 weeks for percentage of original wound area and surface electrical capacitance in picofarads (pF). Data were analyzed for statistical significance (P < .05) by Fisher's exact test, Student's t test, and repeated measures analysis of variance: [table: see text] The data demonstrate that irrigation of cultured skin substitutes with a solution of 5% Sulfamylon results in smaller wound area, fewer wounds that contain human cells, and greater surface hydration (higher surface electrical capacitance) than irrigation with noncytotoxic antimicrobial agents. These results support the conclusion that cultured skin substitutes of this type do not tolerate the chemical toxicity of Sulfamylon as well as skin autografts. Further improvements in the properties of the epidermal barrier of cultured skin substitutes may facilitate the use of Sulfamylon or other potent antimicrobial agents for the management of microbial contamination during engraftment of transplanted skin cells.

Animals↗
PubMed1994

Surfactant-induced skin irritation and skin repair: evaluation of a cumulative human irritation model by noninvasive techniques.

BACKGROUND: Although surfactant-induced acute irritant dermatitis has been extensively studied, our understanding about the induction and repair of the clinically more relevant chronic form is limited. OBJECTIVE: Our purpose was to investigate qualitative and quantitative differences in surfactant-induced irritant skin reactions from cumulative exposure to structurally unrelated surfactants and to compare the maximal irritant responses from this model with corresponding reactions noted in a previously reported acute irritation model. METHODS: Sodium lauryl sulfate (SLS), dodecyl trimethyl ammonium bromide (DTAB), and potassium soap were the model irritants. Surfactant solutions (7.5%) were applied for 20 minutes daily (for 8 consecutive days excluding the weekend) to the volar aspect of the forearm of 11 volunteers. Irritant reactions were repeatedly assessed until complete healing was indicated by visual assessment and by measurements of transepidermal water loss (TEWL), erythema (skin color reflectance), and stratum corneum hydration (electrical capacitance). Maximum irritant responses were compared with corresponding reactions from an acute irritation model. RESULTS: TEWL was increased by SLS and DTAB to the same extent, but erythema was significantly higher in DTAB-treated skin. Skin dryness, as demonstrated by decreased capacitance values and increased scores for scaling and fissuring, was significantly more pronounced than in an acute irritation model for SLS and DTAB, although no difference was detected between the two surfactants. Potassium soap led to a slight increase in TEWL, whereas the remaining features were not significantly changed. CONCLUSION: This chronic irritation model appears to represent the clinical situation of irritant contact dermatitis with pronounced skin dryness more closely than the acute irritation model. The present study confirms that an extended time is needed for complete healing of irritant skin reactions. We also demonstrated that the evaluation of the irritation potential of diverse surfactants depended significantly on the feature evaluated (erythema vs electrical capacitance and TEWL), on the mode of application (acute vs cumulative), and, in the cumulative model, on the point of observation.

Adult↗
PubMed1993

The efficacy of a moisturizer (Locobase) among cleaners and kitchen assistants during everyday exposure to water and detergents.

Workers exposed to various irritants are widely advised to use moisturizers. To evaluate the efficacy of a moisturizer (Locobase), we studied 111 cleaners and kitchen workers during everyday exposure to water and detergents. All took part in a standardized interview. After randomization, 1/2 the workers (n = 56) used Locobase during a period of 2 weeks (period L), followed by a period without any emollient (period C), or vice versa (n = 55). Clinical assessment and measurements of the skin surface temperature, electrical capacitance and transepidermal water loss (TEWL) were performed on the fingers, hands and arms on entry to the study, after 2 weeks and 4 weeks, or at drop out. The final evaluation showed that 70 (63%) were able to complete the study; 23 (21%) completed period L, but withdrew from period C after a mean of 6 days because of progressive dryness of the skin and eczema; and 12 (11%) were excluded because they used topical corticosteroids or emollients. The remaining 6 (5%) participants were lost to follow-up. Clinically, we observed a significant increase in dryness (p < 0.001) during periods of no treatment (period C), and normalization of the skin texture during use of Locobase. Clinical observations were confirmed by statistically significant differences (p < 0.001) in the electrical capacitance (epidermal hydration), which decreased during period C and increased to pre-study values during period L. No significant differences were found in skin temperatures and TEWL rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2004

Automated multi-well device to measure transepithelial electrical resistances under physiological conditions.

Measurement of transendothelial or transepithelial electrical resistances (TERs) is a straightforward in situ experimental approach to monitor the expression or modulation of barrier-forming cell-to-cell contacts (tight junctions) in cultured cells grown on porous filters. Although widely accepted, there is currently no device available to automatically measure the time course of TERs under ordinary cell culture conditions (37 degrees C, 5% or 10% CO2). This paper describes a development from our laboratory that is capable of following in parallel the TERs of several filter-grown cell layers with time and in an entirely computer-controlled fashion. The cell cultures can be followed even in long-term experiments without any manual assistance or opening of the incubator Besides reading TER values, this approach also returns the electrical capacitance of the cell layers, which is indicative of the expression of microvilli and other membrane extrusions. The device is based on reading the frequencydependent impedance of the cell layer, followed by equivalent circuit modeling to extract the cell-related parameters. It is compatible with several multi-well formats (up to 96 wells) and controlled by custom-designed software that reads, analyzes, and presents the data.

Animals↗
PubMed2000

Skin irritation and dryness associated with two hand-hygiene regimens: soap-and-water hand washing versus hand antisepsis with an alcoholic hand gel.

OBJECTIVE: To compare the frequency of skin irritation and dryness associated with using an alcoholic-hand-gel regimen for hand antisepsis versus using soap and water for hand washing. DESIGN: Prospective randomized trial with crossover design. Irritation and dryness of nurses' hands were evaluated by self-assessment and by visual assessment by a study nurse. Epidermal water content of the dorsal surface of nurses' hands was estimated by measuring electrical capacitance of the skin. SETTING: Miriam Hospital, a 200-bed university-affiliated teaching hospital. PARTICIPANTS: Thirty-two nurses working on three hospital wards participated in the trial, which lasted 6 weeks. RESULTS: Self-assessment scores of skin irritation and dryness decreased slightly during the 2 weeks when nurses used the alcoholic-hand-gel regimen (mean baseline score, 2.72; mean final score, 2.0; P=.08) but increased substantially during the 2 weeks when nurses used soap and water (mean baseline score, 2.0; mean final score, 4.8; P<.0001). Visual assessment scores by the study nurse of skin irritation and dryness did not change significantly when the alcoholic-hand-gel regimen was used (mean baseline and final scores were both 0.55), but scores increased substantially when nurses used soap and water (baseline score, 0.59; mean final score, 1.21; P=.05). Epidermal water content of the dorsal surface of nurses' hands changed little when the alcoholic-hand-gel regimen was used (mean+/-standard deviation baseline electrical capacitance reading, 24.8+/-6.8; mean final reading, 25.7+/-7.3), but decreased significantly (skin became dryer) with soap-and-water hand washing (mean baseline, 25.9+/-7.5; mean final reading, 20.5+/-5.4; P=.0003). CONCLUSIONS: Hand antisepsis with an alcoholic-hand-gel regimen was well tolerated and did not result in skin irritation and dryness of nurses' hands. In contrast, skin irritation and dryness increased significantly when nurses washed their hands with the unmedicated soap product available in the hospital. Newer alcoholic hand gels that are tolerated better than soap may be more acceptable to staff and may lead to improved hand-hygiene practices.

Antisepsis↗