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Background/purpose Existing skin mechanical testing devices focus on measuring skin elasticity and are not tailored to assess the dynamic behavior of skin. Additionally, the mathematical techniques used in existing devices are often not optimal. Methods A new dynamic mechanical device that measures the linear dynamics of skin was developed and tested. The mechanical properties of skin were evaluated in experiments in which stiffness and damping parameters were measured (i) at different locations on the arm and hand, (ii) when stratum corneum hydration was varied by controlled changes in environmental humidity, and (iii) following the application of film-forming polymers. Parallel measurements were made with the Cutometer® so that the two devices could be compared. Results The findings revealed that reliable and valid measurements of skin mechanical properties can be obtained from the device. The stiffness of the skin was shown to vary significantly as a function of skin site, changes in stratum corneum hydration and following application of the polymer films. Changes in the damping parameter were less consistently associated with varying the condition of the skin. Conclusion The high reliability and speed of measurement make this device and analytic procedure an attractive option for testing skin mechanics.

Background Oxidative stress is an important factor in the pathology of age-related hearing loss. Recent animal studies have reported that ultraviolet radiation in sunlight is related to systemic induction of oxidative stress. Chronic sun exposure leads to photodamaged skin, which is manifested as facial skin wrinkling and hyperpigmentation. We hypothesized that sunlight exposure, as assessed by the severity of facial skin photodamage, might be associated with hearing impairment through an oxidative stress mechanism. To examine this, we performed a cross-sectional analysis by using the baseline data from a community-based cohort study of older Japanese. Methods A total of 805 residents (342 men and 463 women) aged 65 years or older living in Kurabuchi Town, Gunma prefecture, Japan, were examined between 2005 and 2006. Facial skin condition was quantified by image analysis of standardized facial images. Hearing impairment was defined as a failure to hear a 30-dB signal at 1 kHz and a 40-dB signal at 4 kHz in the better ear in pure-tone audiometric tests. Results In men, facial wrinkle was positively associated with hearing impairment (for highest vs lowest: multivariate-adjusted odds ratio, 2.16; 95% confidence interval, 1.00-4.66; p for trend = .01). Stratified analysis by age, educational level, smoking status, sunscreen or foundation use, and diabetes showed results similar to those for men as a whole. This association was particularly pronounced in men with the low levels of antioxidants and without occupational noise exposure. We observed no apparent association in women. Conclusions The results support the hypothesis that chronic sun exposure is a risk factor of hearing impairment.

BACKGROUND: The number of studies that use objective and quantitative methods to evaluate facial skin aging in elderly people is extremely limited, especially in Japan. Therefore, in this cross-sectional study we attempted to characterize the condition of facial skin (hyperpigmentation, pores, texture, and wrinkling) in Japanese adults aged 65 years or older by using objective and quantitative imaging methods. In addition, we aimed to identify lifestyle factors significantly associated with these visible signs of aging. METHODS: The study subjects were 802 community-dwelling Japanese men and women aged at least 65 years and living in the town of Kurabuchi (Takasaki City, Gunma Prefecture, Japan), a mountain community with a population of approximately 4800. The facial skin condition of subjects was assessed quantitatively using a standardized facial imaging system and subsequent computer image analysis. Lifestyle information was collected using a structured questionnaire. The association between skin condition and lifestyle factors was examined using multivariable regression analysis. RESULTS: Among women, the mean values for facial texture, hyperpigmentation, and pores were generally lower than those among age-matched men. There was no significant difference between sexes in the severity of facial wrinkling. Older age was associated with worse skin condition among women only. After adjusting for age, smoking status and topical sun protection were significantly associated with skin condition among both men and women. CONCLUSIONS: Our study revealed significant differences between sexes in the severity of hyperpigmentation, texture, and pores, but not wrinkling. Smoking status and topical sun protection were significantly associated with signs of visible skin aging in this study population.

Aim: To study the relationship between age-related maculopathy (ARM) and exposure to sunlight using an objective method. Methods: In a case–control study of Japanese men aged ⩾50 years (67 controls without ophthalmic disease and 148 with ARM), those with ARM were separated into groups of early (n = 75) and late (n = 73) ARM. Facial wrinkle length and area of hyperpigmentation, which are considered to be associated with exposure to sun, were measured using imaging with computer-based image analysis. Skin tone was also measured on the upper inner arm, which is not exposed to sun. Early and late ARM association with skin measurements was then evaluated. Results: Significantly more facial wrinkling (p = 0.047, odds ratio 3.8; 95% CI 1.01 to 13.97) and less facial hyperpigmentation (p = 0.035, odds ratio 0.3; 95% CI 0.08 to 0.92) was present in late ARM cases. The relationship between skin tone and ARM risk was not statistically significant. Conclusions: This objective method showed that lifetime exposure to sunlight is an important factor in the progression of late ARM. An individual’s reaction to sunlight exposure may have a role in ARM progression in addition to total lifetime exposure to sunlight.

In order to better understand the effect of chronic sun exposure on facial skin photo-aging and to identify the factors affecting it, we planned a study in two areas in Japan, Akita and Kagoshima, which correspond to the low and high sun exposure environments, respectively. As a first step, we conducted a pilot study in the two areas, examining 195 subjects. Hyper-pigmentation and wrinkling were measured with a high-resolution digital video imaging system. As expected, people in Kagoshima had darker skin, higher visual grades of facial hyper-pigmentation, and more facial wrinkles than people in Akita, reflecting the difference of UV exposure levels in the two areas. Both the grades of hyper-pigmentation and number of wrinkles increased in a roughly linear fashion with the advancement of age. On the other hand, the effect of gender was different in those two skin photo-aging parameters. Women had higher hyper-pigmentation grades (P = 0.012) and less wrinkles (P = 0.004) than men. Interestingly, post-menopausal women had higher grades of hyper-pigmentation than pre-menopausal women. Neither sun exposure index for darkness nor wrinkling showed any significant differences by menopausal status. In this pilot study, we collected information on various factors, including life-styles. The results of detail analysis will be presented elsewhere. In the present analysis, we found that the grade of hyper-pigmentation was not related to total hours spent outside in life but was affected by various factors, including toe-nail zinc levels. On the other hand, the number of wrinkles was significantly related to total hours spent outside in life. The most important risk factors of non-melanoma skin cancer are chronic sun exposure, age and male sex. All of them are strongly related to higher levels of UV exposure. The present study confirmed that chronic sun exposure, age and male sex were strong risk factors of the wrinkle number. The number of wrinkles was significantly related to total hours of sun exposure in life, increased in a roughly linear fashion with the advancement of age, and was larger in men than in women. In epidemiological studies of UV-related skin cancer, the number of wrinkles, which can be easily measured with a high-resolution digital video imaging system as shown in this study, may be a good marker of total sun exposure in life.

High resolution gel electrophoresis was used to monitor the successive addition of dNMP residues onto the 3'-OH ends of discrete 5'-32P-primers, during DNA synthesis on natural templates. Resulting autoradiographic banding patterns revealed considerable variation in the relative rates of incorporation at different positions along the template. The pattern of "pause sites" along the template was unique for each of three different DNA polymerases (polymerase I (the "large fragment" form of Escherichia coli), T4 polymerase (encoded by bacteriophage T4), and AMV polymerase (DNA polymerase of avian myeloblastosis virus]. Most pause sites were not caused by attenuation of polymerization at regions of local secondary structure in the template. Assays of the accuracy of incorporation at different positions along the template (in which elongation was monitored in the presence of only 3 of the 4 2'-deoxynucleoside 5'-triphosphates) strongly suggested that the relative fidelity of DNA synthesis catalyzed by different polymerases depends on the position on the template at which the comparison is made. Primer-templates were constructed that permitted comparison of elongation during synthesis on a single-stranded template with that during polymerization through a double-stranded region (wherein elongation required concomitant displacement of a strand annealed adjacent to the 5'-32P-primer). Although strand displacement DNA synthesis catalyzed by polymerase I occurred approximately ten times more slowly than synthesis in the same region of a single-stranded viral template, most of the pause sites were the same in the presence or absence of "tandem" primer. Electrophoretic assays of the fidelity of DNA synthesis suggested that an increased tendency toward misincorporational "hotspots" occurred when elongation required concomitant strand displacement.

The fidelity of E. coli DNA polymerase I in the presence of Mg2+ vs Mn2+ was examined at many positions along natural DNA templates, by use of an electrophoretic assay of misincorporation. Although there was an overall greater tendency for misincorporation to occur in Mn2+-activated chain elongation, some specific sites on the template were more prone to misincorporation with Mg2+ and others with Mn2+. This sequence-dependent effect was seen in spite of the finding that the relative rate of incorporation of the correct nucleotide at different positions on the template was essentially the same with Mg2+ and Mn2+. In agreement with previous studies, the fidelity of E. coli pol I was higher at activating, than at inhibiting, concentrations of Mg2+. The results reveal new complexities regarding the role of divalent cation in the control of fidelity in DNA synthesis and attest to the dynamic nature of interactions between DNA polymerase, its substrates and divalent metal activator during the course of polymerization on natural templates.

A method has been developed for simultaneous comparison of the propensity of a DNA polymerase to misincorporate at different points on a natural template-primer. In this method elongation of a [5'-32P] primer, annealed to a bacteriophage template strand, is carried out in the presence of only three dNTPs (highly purified by HPLC). Under these conditions the rate of primer elongation (monitored by gel electrophoresis/autoradiography) is limited by the rate of misincorporation at template positions complementary to the missing dNTP. Variations in the rate of elongation (revealed by autoradiographic banding patterns) reflect variations in the propensity for misincorporation at different positions along the template. The effect on primer elongation produced by addition of a chemically modified dNTP to 'minus' reactions reveals the mispairing potential of the modified nucleotide during DNA synthesis. By use of this electrophoretic assay of misincorporation we have demonstrated that the fidelity of E. coli DNA polymerase I varies greatly at different positions along a natural template, and that BrdUTP and IodUTP can be incorporated in place of dCTP during chain elongation catalyzed by this enzyme.