Physiology of the skin--differences between women and men

Insights and mechanics-driven modeling of human cutaneous impact injuries

Cutaneous damage mechanisms related to dynamic fragment impacts are dependent on the impact angle, impact energy, and fragment characteristics including shape, volume, contact friction, and orientation. Understanding the cutaneous injury mechanism and its relationship to the fragment parameters is lacking compromising damage classification, treatment, and protection. Here we develop a high-fidelity dynamic mechanics-driven model for partial-thickness skin injuries and demonstrate the influence of fragment parameters on the injury mechanism and damage sequence. The model quantitatively predicts the wound shape, area, and depth into the skin layers for selected impact angles, kinetic energy density, and the fragment projectile type including shape and material. The detailed sequence of impact damage including epidermal tearing that occurs ahead of the fragments initial contact location, subsequent stripping of the epidermal/dermal junction, and crushing of the underlying dermis are revealed. We demonstrate that the fragment contact friction with skin plays a key role in redistributing impact energy affecting the extent of epidermal tearing and dermal crushing. Furthermore, projectile edges markedly affect injury severity dependent on the orientation of the edge during initial impact. The model provides a quantitative framework for understanding the detailed mechanisms of cutaneous damage and a basis for the design of protective equipment.

Evaluation of the effect of several moisturizing creams using the low frequency electrical susceptance approach

Moisturizers are cosmetic compounds designed to increase the moisture content of the skin. There are many types of these products in the market making it difficult for consumers to select the most effective moisturizer according to their age and gender. Hence, the aim of this study was to evaluate the effects of different moisturizers on skin hydration as well as to figure out any dependencies of the effects of these products on age or gender-related differences. We investigated the short-term moisturizing effects of five different skin moisturizers on 60 participants by using a low frequency electrical instrument. Skin surface susceptance was recorded and compared before and after the application of moisturizers. Statistically significant differences were observed in the moisturizing effect among different types of products. However, with respect to gender and age differences, there were insignificant differences in the effects of the moisturizers. Results of this study suggest that some types of moisturizers that exist in the markets are not as effective as required, which calls for a further evaluation of the moisturizers before entering markets and offering them for sale. In addition, findings suggest that gender or age differences are perhaps not important to consider in the application of moisturizers.

Artificial intelligence analysis of over a million Chinese men and women reveals level of dark circle in the facial skin aging process

BACKGROUND

To better compare the progression of dark circles and the aging process in Chinese skin. A total of 100 589 Chinese males and 1 838 997 Chinese females aged 18 to 85, without facial skin conditions, and who had access to a smartphone with a high-resolution camera all took selfies.

METHOD

Using a smartphone application with a built-in artificial intelligence algorithm, facial skin diagnostic evaluated the selfies and score the severity of the dark circles with four other facial indicators (including skin type, Pores, Acne vulgaris, and Blackheads). Basic information was collected with online questionnaire, including their age, gender, skin sensitivity, and dietary habits.

RESULTS

In users between the age of 18 and 59, the prevalence of comprehensive, pigmented, and structural type of dark circles all rose with age. However, between the age of 60 and 85, the intensity of all types of dark circles diminished. Besides, vascular dark circles progressively worsen from the age of 18 to their peak at 39, and then gradually decline with age. Females typically have more pronounced black circles under their eyes than males in China. Bad eating habits, urbanization, regular cosmetics use, and sensitive skin positively correlate with severe dark circles. Vascular, comprehensive dark circles were worse in spring. Both pigmented and structural dark circles were worse in the summer. The results indicated that the intensity of dark circles was influenced by oily skin, wide pores, severe blackheads, and severe acne.

CONCLUSIONS

Chinese men and women differed noticeably in the prevalence of each face aging indicator and the appearance of aging dark circles. Selfies could be automatically graded and examined by artificial intelligence, which is a quick and private method for quantifying signs of facial aging and identifying major problems for different populations. Artificial intelligence would assist in the development of individualized preventive and therapeutic interventions.

Gender Differences in Post-Operative Human Skin

Although the impact of age, gender, and obesity on the skin wound healing process has been extensively studied, the data related to gender differences in aspects of skin scarring are limited. The present study performed on abdominal human intact and scar skin focused on determining gender differences in extracellular matrix (ECM) composition, dermal white adipose tissue (dWAT) accumulation, and Foxn1 expression as a part of the skin response to injury. Scar skin of men showed highly increased levels of COLLAGEN 1A1, COLLAGEN 6A3, and ELASTIN mRNA expression, the accumulation of thick collagen I-positive fibers, and the accumulation of α-SMA-positive cells in comparison to the scar skin of women. However, post-injured skin of women displayed an increase (in comparison to post-injured men's skin) in collagen III accumulation in the scar area. On the contrary, women's skin samples showed a tendency towards higher levels of adipogenic-related genes (PPARγ, FABP4, LEPTIN) than men, regardless of intact or scar skin. Intact skin of women showed six times higher levels of LEPTIN mRNA expression in comparison to men intact (p < 0.05), men post-injured (p < 0.05), or women post-injured scar (p < 0.05) skin. Higher levels of FOXN1 mRNA and protein were also detected in women than in men's skin. In conclusion, the present data confirm and extend (dWAT layer) the data related to the presence of differences between men and women in the skin, particularly in scar tissues, which may contribute to the more effective and gender-tailored improvement of skin care interventions.

Effect of gender, muscle type and skinfold thickness on myometric parameters in young people

Background

The aim of the study was to compare the mechanical properties of three human skeletal muscles: biceps brachii (BB), rectus femoris (RF), and tibialis anterior (TA) at rest measured by myoton device in males (n = 16, mean age 21.2 ± 0.6 years) and females (n = 16; 21.2 ± 0.9 years) and to investigate the influence of skin and subcutaneous tissue thickness (skinfold thickness, SFT) and gender on myometric parameters of the three skeletal muscles.

Methods

We measured the following mechanical and viscoelastic muscle properties using MyotonPRO^®: frequency (F [Hz]), decrement (D [log]), stiffness (S [N/m]), relaxation time (R [ms]) and creepability (C [De]). The values of SFT for all selected muscles were assessed by caliper. A mixed-design analysis of variance with gender as between subject comparison was used for assessing the differences between gender and muscles in SFT and each of the myometric parameters separately (F, D, S, R and C). Pearson correlation coefficient or Spearman’s rank correlation coefficient between SFT and myometric parameters was conducted for males, females and males and females together. The level of statistical significance was set at α ≤ 0.05 with Bonferroni correction for multiple comparisons.

Results

The SFT over the RF, TA, and BB muscles in women was statistically significantly larger compared with that of males. In females and males, the SFT over the RF was larger than over the TA and BB, and the SFT over the TA was larger compared with over the BB. The values of F and S recorded for the TA muscle were the highest among the three muscles, while D, C, and R were lowest in TA but highest in the RF muscle in men and women. The values of F and S were smaller in females than in males. Gender comparison of D, C, and R values showed that only D for the RF was significantly lower in females than in males, and C for the RF and TA was significantly larger in females than in males. Some correlation between SFT and myometric parameters were different between males and females. For example, there was a significant, negative correlation between SFT and F for all muscles in females, and a significant, positive correlation between these parameters for BB and TA (not for RF) in males. For pooled data (males and females together), a negative significant correlation between SFT and F was observed for RF and TA (not significant for BB muscle).

Discussion

It is concluded that the TA compared with the BB and RF has significantly greater F and S but the smallest D and C and the shortest R. Gender and muscle differences in the SFT may affect the measurements of muscle properties using MyotonPRO^®. The relationship between SFT and myometric parameters is different in males and females in the RF, TA, and BB muscles. Therefore, the myometric data should be analyzed in males and females separately.

Pharmacokinetics and Tissue Distribution of Combined Triptolide and Paeoniflorin Regimen for Percutaneous Administration in Rats Assessed by Liquid Chromatography-Tandem Mass Spectrometry

Triptolide (TP) has shown potential in rheumatoid arthritis (RA) treatment, but the narrow therapeutic window limits its clinical application. In clinical practice, the compatibility of Tripterygium wilfordii and Paeonia lactiflora is often used to attenuate the toxicity of TP, but its compatibility mechanism has not been fully elucidated. The aim of this study was to investigate the pharmacokinetics and tissue distribution of a combined regimen of TP and paeoniflorin (PF) after transdermal administration in male and female Sprague Dawley (SD) rats via a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The results showed that after percutaneous administration of TP and PF, there was no significant difference in AUC _(0-t) (area under the curve) of TP, the peak concentration decreased by 58.17%, and the peak time was delayed. The AUC _(0-t) of PF increased significantly (P < 0.01), the peak-reaching concentration and AUC _(0-∞) increased, and the half-life and average retention time were shortened, indicating that TP absorption in rats may be delayed. After percutaneous administration of TP and PF, the content of TP in the heart, liver, spleen, lungs, and kidneys of male rats significantly decreased at 2 h (P < 0.05) and the drug concentration in the liver tissues significantly decreased at 2 h, 4 h, and 8 h (P < 0.05). The TP content in the spleen of female rats significantly decreased at 2 h and 4 h (P < 0.05) and also decreased in other tissues, but not significantly. After percutaneous administration of TP and PF, the PF content in the heart, liver, spleen, lungs, and kidneys of male and female rats had no significant difference. However, after percutaneous administration of TP and PF, the TP concentration in the skin increased, suggesting that the amount of TP retained in the skin increased, thereby reducing its content in blood and tissues, producing a reduction in toxicity effect.

Influence of quarantine mask use on skin characteristics: One of the changes in our life caused by the COVID-19 pandemic

BACKGROUND

The influence of various environmental factors on skin properties is well known. However, there is a lack of research into the effect of quarantine masks on skin properties, even though the use of masks has significantly increased after the COVID-19 outbreak. Therefore, this study aimed to investigate the influence of mask use on skin properties.

MATERIALS AND METHODS

Twenty subjects were enrolled in this study. The subjects used approved quarantine masks for 6 hours a day for 2 weeks. We measured eight skin biophysical parameters: temperature, redness, pore volume, texture, elasticity, trans-epidermal water loss (TEWL), sebum content, and pH, and evaluated acne lesions before and after using quarantine masks. The evaluation was performed on the mask-wearing area of the face.

RESULTS

Skin temperature, redness, and TEWL increased significantly after a 6-hour mask use, while the sebum content increased marginally. Skin elasticity was reduced by the use of masks over 1 and 2 weeks, whereas the pore volume and the number of acne lesions increased after a 2-week mask use. The skin changes caused by mask use showed sex-based differences in the skin elasticity (after 6 hours), redness, and roughness (after 2 weeks).

CONCLUSIONS

The use of quarantine masks causes a change in the skin temperature, redness, and TEWL in the short term and in skin elasticity, pores, and acne in the long term. This study revealed that prolonged mask use could have negative effects on the skin.

Physiological skin FDG uptake: A quantitative and regional distribution assessment using PET/MRI

Purpose

To retrospectively assess the repeatability of physiological F-18 labeled fluorodeoxyglucose (FDG) uptake in the skin on positron emission tomography/magnetic resonance imaging (PET/MRI) and explore its regional distribution and relationship with sex and age.

Methods

Out of 562 examinations with normal FDG distribution on whole-body PET/MRI, 74 repeated examinations were evaluated to assess the repeatability and regional distribution of physiological skin uptake. Furthermore, 224 examinations were evaluated to compare differences in the uptake due to sex and age. Skin segmentation on PET was performed as body-surface contouring on an MR-based attenuation correction map using an off-line reconstruction software. Bland–Altman plots were created for the repeatability assessment. Kruskal–Wallis test was performed to compare the maximum standardized uptake value (SUVmax) with regional distribution, age, and sex.

Results

The limits of agreement for the difference in SUVmean and SUVmax of the skin were less than 30%. The highest SUVmax was observed in the face (3.09±1.04), followed by the scalp (2.07±0.53). The SUVmax in the face of boys aged 0–9 years and 10–20 years (1.33±0.64 and 2.05±1.00, respectively) and girls aged 0–9 years (0.98±0.38) was significantly lower than that of men aged ≥20 years and girls aged ≥10 years (p<0.001). In women, the SUVmax of the face (2.31±0.71) of ≥70-year-olds was significantly lower than that of 30–39-year-olds (3.83±0.82) (p<0.05).

Conclusion

PET/MRI enabled the quantitative analysis of skin FDG uptake with repeatability. The degree of physiological FDG uptake in the skin was the highest in the face and varied between sexes. Although attention to differences in body habitus between age groups is needed, skin FDG uptake also depended on age.

Modeling early thermal injury using an ex vivo human skin model of contact burns

BACKGROUND

Early mechanisms underlying the progressive tissue death and the regenerative capability of burn wounds are understudied in human skin. A clinically relevant, reproducible model for human burn wound healing is needed to elucidate the early changes in the human burn wound environment. This study reports a reproducible contact burn model on human skin that explores the extent of tissue injury and healing over time, and defines the inter-individual variability in human skin to enable use in mechanistic studies on burn wound progression and healing.

METHODS

Using a customized burn device, contact burns of various depths were created on human skin by two operators and were evaluated for histologic depth by three raters to determine reproducibility. Early burn wound progression and wound healing were also evaluated histologically after the thermally injured human skin was cultured ex vivo for up to 14 days.

RESULTS

Burn depths were reproducibly generated on human skin in a temperature- or time-dependent manner. No significant difference in operator-created or rater-determined depth was observed within each patient sample. However, significant inter-individual variation was identified in burn depth in ten patient samples. Burn-injured ex vivo human skin placed into culture demonstrated differential progression of cell death and collagen denaturation for high and low temperature contact burns, while re-epithelialization was observed in superficial burn wounds over a period of 14 days.

CONCLUSION

This model represents an invaluable tool to evaluate the inter-individual variability in early burn wound progression and wound healing to complement current animal models and enhance the translation of preclinical research to improvements in patient care.

Review of Modern Techniques for the Assessment of Skin Hydration

Skin hydration is a complex process that influences the physical and mechanical properties of skin. Various technologies have emerged over the years to assess this parameter, with the current standard being electrical probe-based instruments. Nevertheless, their inability to provide detailed information has prompted the use of sophisticated spectroscopic and imaging methodologies, which are capable of in-depth skin analysis that includes structural and composition details. Modern imaging and spectroscopic techniques have transformed skin research in the dermatological and cosmetics disciplines, and are now commonly employed in conjunction with traditional methods for comprehensive assessment of both healthy and pathological skin. This article reviews current techniques employed in measuring skin hydration, and gives an account on their principle of operation and applications in skin-related research.

Male versus female skin: What dermatologists and cosmeticians should know

Introduction

The skin is important for the perception of health and beauty. Knowledge of the physiological, chemical, and biophysical differences between the skin of male and female patients helps dermatologists develop a proper approach not only for the management of skin diseases but also to properly take care of cosmetic issues. The influence of genetic and environmental factors on skin characteristics is also critical to consider.

Methods

A literature search of PubMed and Google was conducted to compare the biophysical and biomechanical properties of the skin of male and female patients using the keywords "skin", "hydration", "water loss", "sebum", "circulation", "color", "thickness", "elasticity", "pH", "friction", "wrinkle", "sex", "male", and "female".

Results

A total of 1070 titles were found. After removing duplications and non-English papers, the number was reduced to 632. Of the 632 titles, 57 were deemed suitable for inclusion in this review. The studies show that the skin parameters of hydration, transepidermal water loss, sebum, microcirculation, pigmentation, and thickness are generally higher in men but skin pH is higher in women.

Conclusions

These parameters can be considered as age markers in some cases and are susceptible to change according to environment and life style. Biometrological studies of the skin provide useful information in the selection of active principles and other ingredients of formulations to develop a specific approach for cosmetic treatments.

Gender differences in the fluorescence of human skin in young healthy adults

BACKGROUND

Human skin naturally contains many endogenous fluorophores; therefore, fluorescence techniques can be used for monitoring of the human skin even in in vivo mode. The aim of this work was to study skin autofluorescence in vivo regarding the possible effect of gender.

MATERIALS AND METHODS

Fluorescence emission spectra of young healthy Caucasian adults in 3 anatomical regions (forehead, hand, and inner upper arm) were taken with excitation at 280, 325, or 400 nm.

RESULTS

Three emission bands were found in the spectra for both men and women: (1) an intensive band peaked at 340/280 nm (peak emission/excitation wavelength), corresponding to aromatic amino acids of proteins in epidermis; (2) a broad band with emission between 360 nm and 480 nm (excitation 325 nm) with a base peak around 390 nm and 2 side peaks at 420 and 450 nm, mainly due to collagen cross-links in dermis with a possible weak contribution of elastin and mitochondrial NADPH; (3) a weak but distinct peak at 600/400 nm corresponding presumably to skin unmetalled porphyrins.

CONCLUSION

The intensity of skin autofluorescence showed differences between genders and among anatomical regions. The 340 nm intensity was 1.4 times higher in the male group in all 3 anatomical regions studied. The highest intensity of skin autofluorescence for the peaks at 340/280 nm and 600/400 nm was found on the forehead, whereas the 390/325 nm band was most intensive on the inner upper arm in both genders.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Postnatal changes and sexual dimorphism in collagen expression in mouse skin

To investigate sexual dimorphism and postnatal changes in skin collagen expression, mRNA levels of collagens and their regulatory factors in male and female skin were examined during the first 120 days of age by quantitative realtime PCR. Levels of mRNAs encoding extracellular matrices did not show any differences between male and female mice until day 15. Col1a1 and Col1a2 mRNAs noticeably increased at day 30 and remained at high levels until day 120 in male mice, while those in female mice remained at low levels during the period. Consistent with the mRNA expression, pepsin-soluble type I collagen contents in skin was very high in mature male as compared to female. Col3a1 mRNA in male mice also showed significantly high level at day 120 as compared to female. On the other hand, expression of mRNAs encoding TGF-ßs and their receptors did not show apparent sexual dimorphism although small significant differences were observed at some points. Castration at 60 days of age resulted in a significant decrease in type I collagen mRNA expression within 3 days, and noticeably decreased expression of all fibril collagen mRNAs examined within 14 days, while administration of testosterone tube maintained the mRNA expression at high levels. Despite the in vivo effect of testosterone, administration of physiological concentrations of testosterone did not affect fibril collagen mRNA expression in either human or mouse skin fibroblasts in vitro, suggesting that testosterone does not directly affect collagen expression in fibroblasts. In summary, present study demonstrated dynamic postnatal changes in expression of collagens and their regulatory factors, and suggest that testosterone and its effects on collagen expression are responsible for the skin sexual dimorphism but the effects of testosterone is not due to direct action on dermal fibroblasts.

Cutaneous melanoma in women

BACKGROUND

Gender disparity in melanoma outcome is consistently observed, suggesting that gender is as an important prognostic factor. However, the source of this gender disparity in melanoma remains unclear.

OBJECTIVE

This article reviews advances in our understanding of gender differences in melanoma and how such differences may contribute to outcomes.

METHODS

A broad literature search was conducted using the PubMed database, with search terms such as 'gender differences in melanoma' and 'sex differences in melanoma.' Additional articles were identified from cited references.

RESULTS

Herein, we address the gender-linked physiologic differences in skin and melanoma. We discuss the influence of estrogen on a woman's risk for melanoma and melanoma outcomes with regard to pregnancy, oral contraceptives, hormone replacement therapy, and UV tanning.

CONCLUSIONS

The published findings on gender disparities in melanoma have yielded many advances in our understanding of this disease. Biological, environmental, and behavioral factors may explain the observed gender difference in melanoma incidence and outcome. Further research will enable us to learn more about melanoma pathogenesis, with the goal of offering better treatments and preventative advice to our patients.

Skin Resistivity Value of Upper Trapezius Latent Trigger Points

Introduction. The skin resistivity (SkR) measurement is commonly recommended for acupoints measurement, but for trigger points (TrPs) only one study is available. The purpose of the study was to evaluate SkR for latent TrPs compared to non-TrPs and the surrounding tissue. Material and Methods. Forty-two healthy volunteers with unilateral latent upper trapezius TrPs (12 men, 30 women) aged 21–23 (mean age: 22.1 ± 0.6 y) participated in the study. Keithley electrometer 610B was used for measuring SkR (Ag/AgCl self-adhesive, disposable ground electrode: 30 mm diameter). SkR was measured for latent TrPs and compared to opposite non-TrPs sites and the surrounding tissue. Results. The SkR decrease of TrPs-positive sites as compared to TrPs-negative sites and the surrounding tissue was confirmed. However, no statistically significant difference in the SkR value occurred when all data were analyzed. The same was confirmed after gender division and for TrPs-positive subjects examined for referred pain and twitch response presence. Conclusion. SkR reactive changes at latent TrPs are possible but the results were not consistent with the previous study. Thus, caution in applying SkR to latent TrPs isolation is recommended and its clinical use should not be encouraged yet. Further studies, especially on active TrPs, are yet required.

Cutaneous Melanoma in Women

Background

Gender disparity in melanoma outcome is consistently observed, suggesting that gender is as an important prognostic factor. However, the source of this gender disparity in melanoma remains unclear.

Objective

This article reviews advances in our understanding of gender differences in melanoma and how such differences may contribute to outcomes.

Methods

A broad literature search was conducted using the PubMed database, with search terms such as ‘gender differences in melanoma’ and ‘sex differences in melanoma.’ Additional articles were identified from cited references.

Results

Herein, we address the gender-linked physiologic differences in skin and melanoma. We discuss the influence of estrogen on a woman’s risk for melanoma and melanoma outcomes with regard to pregnancy, oral contraceptives, hormone replacement therapy, and UV tanning.

Conclusions

The published findings on gender disparities in melanoma have yielded many advances in our understanding of this disease. Biological, environmental, and behavioral factors may explain the observed gender difference in melanoma incidence and outcome. Further research will enable us to learn more about melanoma pathogenesis, with the goal of offering better treatments and preventative advice to our patients.

Accounting for sex-related differences in the estimation of breath alcohol concentrations using transdermal alcohol monitoring

RATIONALE

Previously, we reported methods to estimate peak breath alcohol concentrations (BrAC) from transdermal alcohol concentrations (TAC) under conditions where alcohol consumption was controlled to produce similar BrAC levels in both sexes.

OBJECTIVE

This study characterized differences in the relationship between BrAC and TAC as a function of sex and developed a model to predict peak BrAC that accounts for known sex differences in peak BrAC.

METHODS

TAC and BrAC were monitored during the consumption of a varying number of beers on different days. Both men (n=11) and women (n=10) consumed one, two, three, four, and five beers at the same rate in a 2-h period. Sex and sex-related variables were considered for inclusion in a multilevel model to develop an equation to estimate peak BrAC levels from TAC.

RESULTS

While peak BrAC levels were significantly higher in women than men, sex differences were not significant in observed TAC levels. This lack of correspondence was evidenced by significant sex differences in the relationship between peak TAC and peak BrAC. The best model to estimate peak BrAC accounted for sex-related differences by including peak TAC, time-to-peak TAC, and sex. This model was further validated using previously collected data.

CONCLUSIONS

The relationship between peak TAC and actual peak BrAC differs between men and women, and these differences can be accounted for in a statistical model to better estimate peak BrAC. Further studies are required to extend these estimates of peak BrAC to the outpatient environment where naturalistic drinking occurs.

Characterization of sex-based differences in the mechanical properties of human finger glabrous tissue using a fiberoptic sensor

TAC-Cell is a custom-built somatosensory stimulator that delivers pneumatic cutaneous tactile inputs to virtually any skin target on the body and by virtue of its non-ferrous materials is compatible with functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) brain scanners. In this study, we describe the method to measure apparent skin displacement induced by TAC-Cell stimulation of the glabrous surface of the distal phalanx of the index finger. Specifically, we studied the effect of four servo controller input voltages (0.4V-1.0 V) on resultant skin displacement among eighteen, neurotypical adult male and female participants. A fiberoptic displacement sensor, commonly used in industrial applications, was coupled to the TAC-Cell to measure the glabrous skin׳s kinematic response to different stimulus amplitudes. Skin displacement was significantly dependent on stimulus amplitudes and sex (p<0.0001). Power spectrum and kinematic analysis of skin displacement showed that the pneumatic TAC-Cell stimulus consists of a spectrally rich, high velocity signal. In related work, we have shown that this dynamic pneumocutaneous stimulus is highly effective in evoking a cortical brain response for neurodiagnostic applications and somatosensory pathway analysis in health and disease.

Biology and function of fetal and pediatric skin

The development of the integumentary system is a series of events that starts in utero and continues throughout life. Although at birth, skin in full-term infants is anatomically mature, functional maturity develops during the first year of life. Pediatric skin transitions again with the onset of puberty. At each stage, there are changes in transepidermal water loss, skin hydration, and skin acidity that define the specific period of development.

Age-related changes in cutaneous sensation in the healthy human hand

Cutaneous sensation deteriorates with age. It is not known if this change is consistent over the entire hand or if sensation is affected by changes in skin mechanics. Cutaneous perceptual thresholds were tested at eight sites in the glabrous skin and two in the hairy skin of both hands in 70 subjects (20-88 years), five male and five female per decade, using calibrated von Frey filaments, two-point discrimination, and texture discrimination. Venous occlusion at the wrist (40 ± 10 mmHg) and moisturizer were used to alter skin mechanics. Cutaneous thresholds increased significantly with age (p < 0.001); von Frey thresholds were 0.04 g [0.02-0.07] (median and interquartile range) in the 20s and 0.16 g [0.04-0.4] in the 80s, with differences between hands for older females (p = 0.044) but not males. The pattern of changes in cutaneous sensation varied according to the site tested with smaller changes on the fingers compared to the palm. Two-point discrimination deteriorated with age (p = 0.046), but with no interaction between sex, handedness, or changes in skin mechanics. There were no significant differences for texture discrimination. Changes in skin mechanics improved cutaneous thresholds in the oldest males after moisturizing (p = 0.001) but not otherwise. These results emphasize the complex pattern of age-related deterioration in cutaneous sensation with differences between sexes, the hands, sites on the hand, and the mode of testing. As the index fingertip is not a sensitive indicator of sensory decline, the minimum assessment of age-related changes in cutaneous sensation should include both hands, and sites on the palm.

Gender aspects in skin diseases

Gender differences in medicine have been recognized in anatomy, physiology, as well as in epidemiology and manifestations of various diseases. With respect to skin disorders, males are generally more commonly afflicted with infectious diseases while women are more susceptible to psychosomatic problems, pigmentary disorders, certain hair diseases, and particularly autoimmune as well as allergic diseases. Significantly, more female sex-associated dermatoses can be identified than the male sex-associated dermatoses. Dermatoses in the genital area differ between men and women. Gender differences also exist in the occurrence and prognosis of certain skin malignancies. The mechanisms underlying gender differences in skin diseases remain largely unknown. Differences in the skin structure and physiology, effect of sex hormones, ethnic background, sociocultural behaviour and environmental factors may interact to exert the influences. A better understanding of gender differences in human health and diseases will allow the development of novel concepts for prevention, diagnosis and therapy of skin diseases.

Gender variations in the optical properties of skin in murine animal models

Gender is identified as a significant source of variation in optical reflectance measurements on mouse skin, with variation in the thickness of the dermal layer being the key explanatory variable. For three different mouse strains, the thickness values of the epidermis, dermis, and hypodermis layers, as measured by histology, are correlated to optical reflectance measurements collected with elastic scattering spectroscopy (ESS). In all three strains, males are found to have up to a 50% increase in dermal thickness, resulting in increases of up to 80% in reflectance values and higher observed scattering coefficients, as compared to females. Collagen in the dermis is identified as the primary source of these differences due to its strong scattering nature; increased dermal thickness leads to a greater photon path length through the collagen, as compared to other layers, resulting in a larger scattering signal. A related increase in the observed absorption coefficient in females is also observed. These results emphasize the importance of considering gender during experimental design in studies that involve photon interaction with mouse skin. The results also elucidate the significant impact that relatively small thickness changes can have on observed optical measurements in layered tissue.

Transdermal drug pharmacokinetics in man: Interindividual variability and partial prediction

A database of human dermatopharmacokinetic parameters of 12 transdermal patches is established. The effect of system design, application site, and metabolism on pharmacokinetic data is discussed, and interindividual variability of data and its possible sources evaluated. Using multiple regression analysis, two equations based on drugs physicochemical characteristics are suggested for partial prediction of peak plasma concentration (C(max)) after patch application. Patch application presumably decreases variance as rub-off, wash and exfoliation steps are diminished. The results showed that interindividual variation, in terms of coefficient of variation (CV) of C(max), is inversely correlated with drugs molecular weight and lipophilicity in the range of 200<MW<400 and 1.6<logK(oct)<4.3. Multiple regression analysis of C(max) against physichochemical parameters demonstrated the prominent contribution of hydrogen bonding acceptability of the molecules on their maximal plasma concentration after patch administration. The findings suggest that the serum concentration profile for transdermal therapeutic systems (TTS) is a net result of the system performance, drug absorption and elimination. Thus, the variability in serum concentration is a function of variability of each process involved. This should be noted in explanation of effect of molecular features of drugs on their plasma concentration profile.

Factors affecting corneal and conjunctival sensitivity measurement

PURPOSE

Measurement of sensitivity provides important clues about sensation on the ocular surface. This study aimed to evaluate whether measurements of threshold of sensation to an air stimulus are affected by corneal/conjunctival location, gender, age, time of day, ambient temperature or humidity.

METHODS

A retrospective analysis is reported of ocular surface threshold measurements made by one examiner using the CRCERT-Belmonte esthesiometer. Multiple corneal measurements for 49 normal subjects (24M:25F) and conjunctival measurements for 33 subjects (16M:17F) were included in the analysis. Threshold was measured at the corneal apex and at the inferior conjunctiva 2 mm from the limbus. Measurements were made between 9 AM and 6 PM, at ambient temperature 20 to 26 degrees C and humidity 52 to 87%. Mixed model analysis of variance, paired-t-test and Pearson's correlation were used to examine effects of various factors on threshold.

RESULTS

Mean group corneal threshold was 76.2+/-26.8 mL/min and conjunctival threshold 123.7+/-49.1 mL/min (n=33, p<0.001). Corneal and conjunctival threshold were well correlated (r=0.66, p<0.001). Thresholds were significantly higher for male than female subjects at both the cornea (M 82.2+/-23.5 mL/min, F 67.6+/-24.1 mL/min, p=0.04) and conjunctiva (M 144.1+/-40.7 mL/min, F 105.8+/-50.2 mL/min, p=0.02). A significant reduction in corneal threshold with age was apparent for females (n=25, r= -0.49 p=0.01) but not males. A similar effect on conjunctival sensitivity was not shown. No effect of time of day, ambient humidity or temperature was found on threshold at either site.

CONCLUSIONS

Corneal and conjunctival sensitivity were found to be associated. Corneal and conjunctival sensitivity is higher in female subjects, who also show an age-related increase in corneal sensitivity. No change in sensitivity of either tissue is apparent within normal levels of ambient temperature or humidity or over the course of a working day.

Endothelial function in patients with type 1 diabetes evaluated by skin capillary recruitment

The aim of the present study was to evaluate skin capillary density and recruitment of the upper and lower extremities of patients with type 1 diabetes under chronic treatment without clinical manifestations of diabetes-related complications. This cross-sectional observational study included 59 (27.1+/-10.6 years) consecutive outpatients with type 1 diabetes [duration 10 (1; 45) years] and 41 age- and sex-matched healthy controls. We used intravital video-microscopy to measure basal and maximal (during venous congestion) skin capillary densities as well as capillary recruitment using post-occlusive reactive hyperemia (PORH) in the dorsum of the fingers and toes. Mean capillary density (MCD) of the fingers at baseline was not different between controls and patients (123.02+/-22.6 and 132.3+/-28.9 capillaries/mm(2), respectively; P=0.08). In contrast, baseline MCD of the toes was lower in controls, when compared to patients (84.6+/-19.8 and 96.2+/-23.4 capillaries/mm(2), respectively; P=0.01). Capillary recruitment during PORH (% increase of the number of capillaries/mm(2)) was significantly higher in controls compared to patients both in fingers [7 (-8; 33) and -1.0 (-35, 13), respectively; P=0.000] and toes [6 (-20; 46) and 0 (-24; 20), respectively; P=0.000]. During venous occlusion, capillary density increase (% increase of the number of capillaries/mm(2)) was also higher in controls compared to patients both in fingers [3 (-14; 23) and 0.0 (-30; 29.2), respectively; P=0.02] and toes [9.3 (-18; 51) and -7 (-34; 22), respectively; P=0.000]. Our results showed that patients with type 1 diabetes, although not presenting skin capillary rarefaction, display skin microvascular functional alterations in both extremities characterized by an absence of capillary reserve.

Gender-Related Differences in the Physiology of the Stratum Corneum

BACKGROUND

Only few studies on gender-related differences in skin physiology have been performed--and they provided conflicting results.

OBJECTIVE

In the present study, the effect of gender on the physiology of the stratum corneum was studied.

METHODS

The physiological parameters transepidermal water loss, pH value, hydration and sebum content were determined on the flexor forearms of 6 female and 6 male volunteers. In addition, stratum corneum samples, removed by tape stripping, were studied for amount, spectroscopic properties, protein content, and mass.

RESULTS

The skin of women was characterized by a significantly higher pH value (5.6 +/- 0.4) than that of men (4.3 +/- 0.4, p < 0.05). Protein absorption was the only other parameter significantly dependent on gender (p < 0.05). Both effects might be caused by differences in human biology, such as hormonal status.

CONCLUSION

Therefore, the gender of the volunteers should be considered in dermatologic studies.

Persistent skin colonization with Staphylococcus aureus in atopic dermatitis: relationship to clinical and immunological parameters

BACKGROUND

Staphylococcus aureus has important implications for the pathogenesis of atopic dermatitis (AD). In some patients S. aureus can be eradicated from the skin during anti-inflammatory treatment, while in others bacterial colonization is persistent. Potential mechanisms and features of these two distinct groups of patients are not known.

OBJECTIVE

Accordingly, we studied relationships between the ability to eliminate S. aureus during an anti-inflammatory treatment and selected clinical and immunological features.

METHODS

Quantitative assessment of S. aureus on the skin, in nasal vestibule and throat, serum IgE levels, CD4/CD8 T-cell ratio, lymphocyte proliferation and phagocyte oxidative burst were determined during the exacerbation and after 4 and 12 weeks of the treatment using topical steroid and oral antihistamine in 34 patients with AD.

RESULTS

S. aureus was found on the skin of all 34 patients during exacerbation. Disease severity scoring of atopic dermatitis (SCORAD) correlated with the density of bacteria. Treatment with oral antihistamine and topical steroid resulted in a significant alleviation of symptoms, which correlated with the elimination of S. aureus from the skin in 70% of patients. In the remaining 30% of patients, dense (more than 10(10)/cm2) S. aureus skin colonization, persisted despite the treatment. Patients with persistent S. aureus presented with higher serum IgE levels, lower lymphocyte proliferation in response to staphylococcal enterotoxin B, phytohaemagluttinin and anti-CD3. Persistence of S. aureus was more common in men.

CONCLUSIONS

Patients with AD differ in the ability to clear S. aureus from the skin during anti-inflammatory treatment, which appears to be related to the abnormalities in immunological parameters. Local antibiotic therapy should be considered only in patients with persistent S. aureus colonization.

Estudo clínico aberto multicêntrico da efetividade e tolerabilidade do gel de adapaleno a 0,1%* em pacientes com acne vulgar

FUNDAMENTOS: O adapaleno é um derivado do ácido naftóico, com propriedades biológicas similares às do ácido retinóico e utilizado no tratamento da acne vulgar. OBJETIVOS: Avaliar a eficácia e a tolerabilidade do adapaleno 0,1% gel no tratamento da acne vulgar leve à moderada, em pacientes residentes no Brasil. MATERIAIS E MÉTODOS: Os pacientes aplicaram o gel à noite, durante 12 semanas, e foram avaliados quanto à efetividade pelo número de lesões em cada visita e quanto à tolerabilidade ao produto nas consultas da segunda e da décima segunda semana. RESULTADOS: Dos 125 pacientes, 81,6% completaram as 12 semanas de tratamento, e 10,4% dos casos terminaram o estudo antes do período estabelecido por estarem livres de lesões. Os resultados permitem confirmar a marcante atividade antiinflamatória, antiproliferativa e na diferenciação celular dos ceratinócitos. Houve diminuição dos comedões e das lesões inflamatórias, com resposta satisfatória no eritema, no ressecamento e na descamação da pele. Efeitos adversos pouco graves foram relatados em apenas 9,6% dos pacientes. CONCLUSÕES: O adapaleno, neste estudo e nos vários que o antecederam, vem-se mostrando uma das melhores opções de tratamento tópico para os casos leves a moderados de acne vulgar.