Quantitative evaluation of skin barrier function using water evaporation time related to transepidermal water loss.

BACKGROUND: Transepidermal water loss (TEWL) is often used as an index for skin barrier function. The skin barrier tester, SBT-100 (Rousette Strategy Inc), measures the TEWL, water evaporation time, and time constant by contacting the skin and diffusing water into the closing measurement chamber. However, the relationship between the TEWL and time constant has not been sufficiently investigated. This study involved analyzing the underlying measurement principle and obtaining data through two experiments. MATERIALS AND METHODS: The TEWL and time constant were measured using SBT-100. Experiment 1 produced a simple simulation model for continuous water evaporation from the skin using a moisture-permeable film. In experiment 2, four skin sites of 43 healthy volunteers were examined from May to September 2018. RESULTS: In experiment 1, the TEWL increased and time constant decreased, following an increase in humidity in the external environment. Both parameters demonstrated significant negative correlation (drying: ρ = -0.832, p < 0.001). For the 43 healthy volunteers who participated in experiment 2, their TEWL increased and time constant decreased in summer. For all skin measurement sites, both data demonstrated significant negative correlation (forehead: ρ = -0.909, p < 0.001; back of the left hand: ρ = -0.829, p < 0.001; left lateral elbow: ρ = -0.896, p < 0.001; left lateral malleolus: ρ = -0.865, p < 0.001). CONCLUSION: Results indicated that the time constant is significantly correlated with TEWL. Furthermore, the time constant can be used as a parameter for evaluating skin barrier function.

Factors Affecting and Adjustments for Sex Differences in Current Perception Threshold With Transcutaneous Electrical Stimulation in Healthy Subjects.

OBJECTIVE: Current perception threshold (CPT) measurement is a noninvasive, easy, and semi-objective method for determining sensory function using transcutaneous electrical stimulation. Previous studies have shown that CPT is determined by physical characteristics, such as sex, age, physical sites, and presence of neuropathy. Although the CPT reported in males is clearly higher than that in females, the reason for this difference remains unclear. This study investigates the cause of sex-based differences in CPT and suggests an adjustment method, which may suppress the sex difference in CPT. MATERIALS AND METHODS: Electrical stimulation was applied with PainVision® via five sizes of circular surface electrodes. Seventy healthy participants were examined thrice under each electrode. The relationship among body water percentage, body fat percentage, and CPT was then analyzed. RESULTS: CPT values are higher in males than that in females, with statistically significant sex differences with each electrode pairs (EL 1: p < 0.001; EL 2: p = 0.006; EL 3: p < 0.001; EL 4: p < 0.001; EL 5: p < 0.001). By adjusting for body fat percentage or body water percentage, the log-transformation values (CPT values) no longer exhibit sex differences with any electrode pairs (body fat: p = 0.09; body water: p = 0.08). CONCLUSION: We conclude that sensitivity for perceiving electrical stimulation can be influenced by the subjects' characteristics, such as body fat or body water percentages.

Drug delivery and transmission of lidocaine using iontophoresis in combination with direct and alternating currents.

The present study investigates how effectively lidocaine ions are transported across a cellophane membrane through the application of either a direct current (DC) or alternating current (AC). The cellophane membrane was set on a parallelplate- type acrylic cell with platinum electrodes at both ends, filled with a donor cell of a 1 % aqueous solution of lidocaine and a receptor cell with distilled water. Lidocaine concentrations were measured for 60 min while the following voltages were applied, with changes every 10 min: 3 V DC and 7.5 V sine wave AC; frequency at 1 kHz. As a result, lidocaine concentrations in the receptor cell increased in a time-dependent manner. Significant increases in lidocaine concentrations were observed in groups where the voltage combination consisted of DC 30 min/AC 30 min, DC 50 min/AC 10 min, DC 60 min and AC 10 min/DC 50 min, compared with the passive diffusion group or in groups where voltage application was performed for 20, 30 , 40, 50 and 60 min. Significant increases were also observed in groups where the voltage combination consisted of A C 6 0 min, D C 10 min/AC 5 0 min, AC 3 0 min/ DC 30 min and AC 50 min/DC 10 min, compared with the passive diffusion group or in groups where voltage application was performed for 40, 50 and 60 min. These results suggest that lidocaine was delivered more rapidly with DC than with AC, and that its ions are transported faster when voltage is switched from DC to AC than from AC to DC, which is presumably due to the contribution of electrorepulsion by DC voltage application and the vibration energy infiltration mechanism owning to AC. Iontophoresis in combination with DC and AC was found to enable highly efficient drug delivery that shares the benefits of both forms of current application.

Kinetic study of the radical scavenging of capsaicin in homogeneous solutions and aqueous Triton X-100 micellar suspensions.

A kinetic study of capsaicin (CAP) toward radicals has been performed using stopped-flow spectrophotometry in detail. The second-order rate constants (k2) for the reaction of CAP toward 2,2-diphenyl-1-picrylhydrazyl (DPPH) and galvinoxyl have been measured in methanol, ethanol, 2-propanol/water (5:1, v/v), and aqueous micellar suspensions containing 5% Triton X-100 (pH 4.0 to 10.0), respectively. The decay rates of DPPH and galvinoxyl for the reaction with CAP increased linearly in a concentration-dependent manner in homogeneous solutions and aqueous micellar suspensions. However, the k2 for CAP obtained in an aqueous micellar suspension showed notable pH dependence; that is, the reactivity of CAP increased with an increasing pH value from 4 to 10. In addition, a good correlation between the k2 value and the molar fraction of CAP (phenolate anion (CAP-O(-))/undeprotonated form (CAP-OH)) was observed. These properties are associated with the pKa of CAP. Furthermore, it was found that the CAP-O(-) reacts with galvinoxyl about 6 times as fast as the CAP-OH. These results indicate that sequential proton loss electron transfer from the phenolic hydrogen of CAP may be responsible for the scavenging of radicals in an aqueous micellar suspensions.

A population-based study of arterial stiffness index in relation to cardiovascular risk factors.

We investigated the relation of arterial stiffness, considered an independent predictor of cardiovascular events, to cardiovascular risk factors in a population-based study of 1023 subjects. An Arterial Stiffness Index (ASI) was developed to evaluate arterial stiffness based on an analysis of the pulse wave amplitude pattern acquired from measurements of brachial blood pressure. In control subjects (n = 266) without any major risk factors, the ASI was 46 +/- 11, and increased with age (r = 0.346). The ASI was significantly higher in women ranging from 50 to 54 years of age than in age-matched men. The ASI rose in correlation with the number of risk factors. Subjects with two risk factors showed a significantly higher ASI than those without any risk factors (54 +/- 26 vs. 46 +/- 11). The ASI was significantly increased in diabetic subjects with hypertension in comparison to those without hypertension. Furthermore, hyperlipidemic subjects with hypertension showed significantly higher values than those without hypertension. ASI could be a useful predictor of cardiovascular events in hypertensive subjects with multiple risk factors.

An experimental study of vascular dynamics by an acceleration plethysmogram using artificial circulation devices.

Plethysmogram has been widely known as a conventional non-invasive simple method to obtain information on peripheral circulatory kinetics. We made a quantitative assessment of the relationships between the various circulatory parameters, using the simple conventional measurement method of treating acceleration plethysmograms (the second derivatives of digital plethysmograms) as indicators of peripheral circulation kinetics. We designed a prototype model peripheral circulatory circuit, using an artificial heart, for the purpose of clarifying the relationship between physical factors and plethysmograms. In our models of the peripheral circulatory system, we made use of various types of matching silicon tubes, as well as canine carotid arteries, as substitutes for human arteries. We evaluated the mechanical characteristics, such as the pressure and volume characteristics of the silicon tubes and canine carotid arteries. Plethysmogram alterations were measured using a photoelectric digital plethysmogram. When we examined the acceleration plethysmogram b/a values, which indicate blood vessel extensibility and hardness, and the d/a values, which we were able to use as an index of peripheral circulatory kinetics, it was clear from out model testing that canine carotid arteries displayed b/a values that were closest to those found in the human fingertip; among artificial tubes, the closest was a tube with a diameter of 4 mm (0.18 mm in thickness). The b/a values of all types of tubes declined when the compliance of the arterial system was increased, and it was confirmed through model testing that b/a values are an indicator of blood vessel extensibility.