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At least 271 records · Page 15Linked to original sources
PubMed1993

Electrical measurement of the water content of the stratum corneum in vivo and in vitro under various conditions: comparison between skin surface hygrometer and corneometer in evaluation of the skin surface hydration state.

Two commercially available electrical instruments which evaluate the hydration state of the skin surface were compared in in vitro and in vivo experiments. The skin surface hygrometer (Skicon-200) employs high-frequency conductance, whereas the corneometer (CM 420, CM 820) uses electrical capacitance to determine the level of hydration. In a simulation model of in vivo stratum corneum (SC), the high frequency conductance device showed a much closer correlation with the hydration state of the surface SC (r = 0.99) than the capacitance device (r = 0.79), suggesting that the former can accurately assess the hydration dynamics of SC, particularly that due to the accumulation of easily releasable secondary bound water and free water. Both devices were insensitive to changes of hydration taking place in deeper viable skin tissues, e.g. the accumulated tissue fluids in suction blisters. Although the capacitance device correlated poorly with the hydration dynamics in normal SC, its sensitivity to changes occurring in extremely dry skin, such as scaly psoriatic lesions, suggests its measurements characteristics at an extremely low state of hydration, consisting of mostly bound water, such as noted in pathologic SC.

Adolescent↗
PubMed1997

Preventive and therapeutic effects of a moisturizer. An experimental study of human skin.

The effect of a moisturizer was tested on experimentally irritated human skin in two studies. In a prevention study, 12 volunteers had both hands immersed into a 0.375% sodium lauryl sulphate solution, 10 min twice daily for 2 days. Before each immersion one hand was treated with the moisturizer; the other hand served as control. In a therapeutic study, 12 volunteers had both hands immersed in the same way as mentioned above. After the last immersion one hand was treated for 5 days with the moisturizer; the other hand served as control. Skin barrier function was evaluated by transepidermal water loss (Evaporimeter), and blood flow was evaluated by laser Doppler flowmetry and skin hydration by electrical capacitance (Corneometer). A significant preventive effect was obtained on the treated hand, compared to the control hand, judged by all measured parameters. A significant therapeutic effect was observed on skin barrier function and on skin hydration on the treated hand, compared to the control hand, while no difference between the hands in blood flow was observed after the end of treatment. The moisturizer could prevent irritant skin reactions induced by a detergent, and it could also accelerate regeneration of the barrier function of irritated skin.

Administration, Topical↗
PubMed1992

Scaling, dry skin and gender. A bioengineering study of dry skin.

Dry skin and scaling was studied in a group of 72 healthy volunteers by using subjective self-assessment and by clinical assessment by a dermatologist, as well as application of noninvasive bioengineering techniques to measure scaling and epidermal hydration. The study revealed that 67% of the volunteers had subjective complaints, while only 5.6% had definite clinical signs of dry skin at the time of examination. Subjective complaints were more common in women than in men (p < 0.001), though neither clinical nor objective measurements showed any sex difference, which suggests that other factors may play a role in the way men and women perceive dry skin. Subjective and clinical scores were correlated (p < 0.02), though neither was significantly correlated to objective measurements. Grading of skin scaling on D-squame tapes correlated with densitometry of the tapes (p < 0.001), as did the electrical capacitance (p < 0.001). Both clinical and objective methods can identify dry skin. However, the study showed that in healthy persons a number of irrational factors play a role in the use of moisturizers, and while these factors cannot be measured, they must be taken into account. Healthy, but dry skin is a vaguely defined clinical entity, which may explain the generally poor correlation between the two methods. This underlines the need for several methods to be used simultaneously in order to elicit complementary information.

Adult↗
PubMedDate not supplied

A pressure-sensitive mat for measuring contact pressure distributions of patients lying on hospital beds.

The authors describe a novel system for sensing and displaying the distribution of contact pressure caused by a patient's lying on a hospital bed. The system includes a flexible, pressure-sensitive mat, electronics to activate the mat, a small computer to process data, and a color video display. The present prototypes can sense pressure at 1,536 discrete locations in a rectangular grid of 24 x 64 nodes, each node representing an area of 4 cm2. The computer receives data from each node and displays the results as a false-color map, refreshable every 5 seconds. The pressure-sensitive mat itself includes two orthogonal arrays of ribbon-like conductors, composed of silver-coated nylon fabric, which are separated by insulating open-cell foam rubber. The system monitors the electrical capacitance between selected pairs of horizontal and vertical conductors on opposite sides of the foam. The crossing points form pressure-sensitive nodes. Increased contact pressure compresses the foam, thereby decreasing the distance between the conductors and increasing the capacitance. Node capacitance is determined by measuring the current through it from a voltage source. The outputs of the various nodes are scanned, normalized, and converted to pressures using the known compressive stress-strain relationship for the foam, and the data are then displayed as a false-color image of the pressure distribution.

Beds↗
PubMed1989

Uremic pruritus. Clinical and experimental studies.

The aim of the study was to investigate clinical aspects of pruritus in maintenance hemodialysis patients and to evaluate factors of putative pathogenic importance. 60-65% of the patients in a maintenance hemodialysis program during a two-year period suffered from itching. Patients with pruritus tended to have been on dialysis treatment longer than those without pruritus (p = 0.05), otherwise there was no difference in clinical data or routine laboratory tests. Measurement of itch intensity continuously over one week in 28 patients using a computerized method showed that itching peaked at night after two days without dialysis, was relatively high during treatment and lowest during the day following dialysis. Our results suggest that the accumulation of pruritogens between dialysis sessions influences the intensity of itching. Most patients had "dry" skin. Recording of the stratum corneum water content by measurement of electrical capacitance, in 31 patients (19 with pruritus) and 12 controls, disclosed no significant difference between dialysis patients and controls, but a tendency that pruritic patients had a lower water content than the other subjects. In different body areas, there was a positive correlation in all groups between the clinical estimation of xerosis and hydration. Serum concentrations of parathyroid hormone (PTH) were significantly higher in dialysis patients with pruritus than in those without, but there was no correlation between the degree of symptoms and the PTH level. Indirect immunohistochemistry revealed no immunoreactivity for different parts of the PTH molecule in skin biopsies from uremic patients. Intradermal injections of PTH fragments did not evoke itching or other cutaneous reactions in patients or controls. Our results do not support PTH as a peripheral mediator of uremic itching. Flare reactions induced by intradermal histamine injections were significantly smaller in 26 dialysis patients (18 with pruritus) than in 9 healthy subjects. However, the itch responses were greater in patients with pruritus than in the other subjects, indicating an augmented sensitivity to pruritogens. Repeated histamine injections induced tachyphylaxis in both uremic patients and controls. Indirect immunohistochemistry revealed neuron-specific enolase (NSE) immunoreactive nerve fibers sprouting throughout the layers of the epidermis in 12 dialysis patients (9 with pruritus) but in none of 15 controls. This finding suggests that hemodialysis patients develop an abnormal pattern of cutaneous innervation.

Adult↗
PubMed1996

Effects of calcipotriol on stratum corneum barrier function, hydration and cell renewal in humans.

Calcipotriol, a vitamin D analogue utilized for psoriasis, has irritation as its most frequent reported adverse event. However, studies on its irritant properties in humans have produced conflicting data. This study evaluates the effect of calcipotriol on stratum corneum barrier function, hydration and cell turnover in healthy volunteers, compared with sodium lauryl sulphate (SLS) as a model irritant. Calcipotriol 0.005% ointment and 1% aqueous SLS solution were applied for 60 min once daily for 2 weeks (5 consecutive days weekly) on untreated and on dansyl-chloride-labelled skin. Irritant responses were documented by visual scoring and by measurement of the transepidermal water loss (TEWL) and stratum corneum hydration (electrical capacitance), until day 18. Stratum corneum turnover time (SCTT) was the time in days between staining (day 0) and the disappearance of dansyl fluorescence. SLS caused more erythema, scaling, and a significant TEWL increase for 18 days. In contrast, calcipotriol induced erythema, and slightly but significantly increased TEWL on day 11 only, as compared with the vehicle control (P < 0.05). SLS, but not calcipotriol, caused skin dryness from day 4 to day 18. The shortest SCTT was obtained at SLS-exposed sites (11.2 +/- 0.7 days: mean +/- SD). Calcipotriol significantly shortened SCTT (16.3 +/- 1.1 days) when compared with its vehicle. Compared with the skin irritation induced by SLS, under these test conditions, calcipotriol is a far weaker irritant on normal human skin. In addition, calcipotriol accelerates stratum corneum turnover to a significantly greater extent than its vehicle.

Adult↗
PubMed2005

A modified Poisson-Boltzmann analysis of the capacitance behavior of the electric double layer at low temperatures.

The modified Poisson-Boltzmann theory is used to analyze the anomalous behavior of the electric double layer capacitance for small surface charge at low temperatures and densities. Good agreement is found with simulation and recent density-functional theory results. Negative adsorption is also found in line with theory and simulation. An unsatisfactory feature is the relatively poor structure in this region due to the inherent approximations in the theory. This feature is unimportant in relation to the capacitance results but has implications when calculating adsorption properties.

Journal Article↗
PubMed1977

[Response of splenic resistance and capacitance vessels to electrical stimulation of the hypothalamus and reticular formation in cats].

The effect of electrical stimulation of anterior, medial, and posterior hypothalamus and of midbrain RF on the spleen resistance and capacitance vessels was studied in 48 anesthetized cats. The stimulatin of all the structures but the anterior hypothalamus evoked constrictory responses of the resistance vessels and decreased the blood volume in the spleen. Apart from the constriction, the stimulation of the anterior hypothalamus decreased the tonus of both kinds of vessels in some cases. The highest perfusion pressure was observed during the stimulation of anterior hypothalamus while the greatest rise of venous outflow with the briefest latency was found during the stimulation of the midbrain RF.

Animals↗
PubMed2001

Electrical stimulation influences mineral formation of osteoblast-like cells in vitro.

The aim of the present study was to assess the structure of newly formed mineral crystals after electrical stimulation of osteoblast-like cells in vitro. Pulsed electrical stimulation was coupled capacitively or semi-capacitively to primary osteoblast-like cells derived from bovine metacarpals. Computer calculations revealed that the chosen input signal (saw-tooth, 100 V, 63 ms width, 16 Hz repetition rate) generated a short pulsed voltage drop of 100 microV (capacitive coupled mode) and of 350 microV (semi-capacitive coupled mode) across the cell-matrix layer. Stimulated cultures showed an enhanced mineral formation compared to the non stimulated controls. In cultures exposed to capacitively coupled electric fields and in control cultures nodules and mineralized globules were found. Nodules with a diameter of less than 200 nm covered the cell surface, whereas mineral globules with a diameter of up to 700 nm formed characteristic mineral deposits in the vicinity of the cells similar to biomineral formations occurring in mineralizing tissues. In contrast, large rod-shaped crystals were found in cultures stimulated by semi-capacitive coupled electric fields, indicating a non-physiological precipitation process. In conclusion, osteoblasts in culture are sensitive to electrical stimulation resulting in an enhancement of the biomineralization process.

Animals↗