Emollient structure and chemical functionality effects on the biomechanical function of human stratum corneum

OBJECTIVE

Cosmetic emollients are widely used in skincare formulations due to their ability to 'soften' the skin and modulate formulation spreadability. Though emollients are commonly used, little is known about their effects on the biomechanical barrier properties of human stratum corneum (SC), which play a critical role in consumer perception of formulation efficacy. Accordingly, our objective was to provide new insights with a study involving fourteen cosmetic emollient molecules with widely varying structures, molecular weights, SC diffusivities, topological polar surface areas (TPSAs), viscosities and chemical functionalities.

METHODS

Mechanical stress in the SC was measured in vitro using a substrate curvature measurement technique. Stress development due to SC drying was measured before and after topical treatment with cosmetic emollients. Emollient diffusivity and alterations to lipid content in SC after treatment were measured via ATR-FTIR spectroscopy. The maximum penetration volume of emollient in SC was characterized to elucidate mechanisms underlying emollient effects on stress.

RESULTS

The application of all cosmetic emollients caused a reduction in SC mechanical stress under dehydrating conditions, and a linear correlation was discovered between emollient penetration volume and the degree of stress reduction. These molecules also induced increases in stress equilibration rate, signalling changes to SC transport kinetics. Stress equilibration rate increases linearly correlated with decreasing intensity of the νCH2 band, indicating a previously unknown interaction between cosmetic emollients and SC lipids. Stress and penetration volume results were rationalized in terms of a multi-parameter model including emollient molecular weight, diffusivity, TPSA and viscosity.

CONCLUSION

We provide a new rational basis for understanding the effects of cosmetic emollient choice on biomechanical properties affecting SC barrier function and consumer perception. We demonstrate for the first time that emollients very likely reduce SC mechanical stress through their ability to take up volume when penetrating the SC, and how molecular weight, SC diffusivity, TPSA and viscosity are predictive of this ability. As cosmetic formulations continue to evolve to meet the needs of customers, emollient molecules can be selected that not only contribute to formulation texture and/or spreadability but that also leverage this novel connection between emollient penetration and SC biomechanics.

Thermal-Disrupting Interface Mitigates Intercellular Cohesion Loss for Accurate Topical Antibacterial Therapy

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.

Role of sunscreen formulation and photostability to protect the biomechanical barrier function of skin

The impact of sunscreen formulations on the barrier properties of human skin are often overlooked leading to formulations with components whose effects on barrier mechanical integrity are poorly understood. The aim of this study is to demonstrate the relevance of carrier selection and sunscreen photostability when designing sunscreen formulations to protect the biomechanical barrier properties of human stratum corneum (SC) from solar ultraviolet (UV) damage. Biomechanical properties of SC samples were assayed after accelerated UVB damage through measurements of the SC's mechanical stress profile and corneocyte cohesion. A narrowband UVB (305-315 nm) lamp was used to expose SC samples to 5, 30, 125, and 265 J cm-2 in order to magnify damage to the mechanical properties of the tissue and characterize the UV degradation dose response such that effects from smaller UV dosages can be extrapolated. Stresses in the SC decreased when treated with sunscreen components, highlighting their effect on the skin prior to UV exposure. Stresses increased with UVB exposure and in specimens treated with different sunscreens stresses varied dramatically at high UVB dosages. Specimens treated with sunscreen components without UVB exposure exhibited altered corneocyte cohesion. Both sunscreens studied prevented alteration of corneocyte cohesion by low UVB dosages, but differences in protection were observed at higher UVB dosages indicating UV degradation of one sunscreen. These results indicate the protection of individual sunscreen components vary over a range of UVB dosages, and components can even cause alteration of the biomechanical barrier properties of human SC before UV exposure. Therefore, detailed characterization of sunscreen formulation components is required to design robust protection from UV damage.

Screening sunscreens: protecting the biomechanical barrier function of skin from solar ultraviolet radiation damage

OBJECTIVE

Solar ultraviolet (UV) radiation is ubiquitous in human life and well known to cause skin damage that can lead to harmful conditions such as erythema. Although sunscreen is a popular form of protection for some of these conditions, it is unclear whether sunscreen can maintain the mechanical barrier properties of skin. The objective of this study was to determine whether in vitro thin-film mechanical analysis techniques adapted for biological tissue are able to characterize the efficacy of commonly used UV inhibitors and commercial sunscreens to protect the biomechanical barrier properties of stratum corneum (SC) from UV exposure.

METHODS

The biomechanical properties of SC samples were assayed through measurements of the SC's drying stress profile and delamination energy. The drying stresses within SC were characterized from the curvature of a borosilicate glass substrate onto which SC had been adhered. Delamination energies were characterized using a double-cantilever beam (DCB) cohesion testing method. Successive DCB specimens were prepared from previously separated specimens by adhering new substrates onto each side of the already tested specimen to probe delamination energies deeper into the SC. These properties of the SC were measured before and after UV exposure, both with and without sunscreens applied, to determine the role of sunscreen in preserving the barrier function of SC.

RESULTS

The drying stress in SC starts increasing sooner and rises to a higher plateau stress value after UVA exposure as compared to non-UV-exposed control specimens. For specimens that had sunscreen applied, the UVA-exposed and non-UV-exposed SC had similar drying stress profiles. Additionally, specimens exposed to UVB without protection from sunscreen exhibited significantly lower delamination energies than non-UV-exposed controls. With commercial sunscreen applied, the delamination energy for UV-exposed and non-UV-exposed tissue was consistent, even up to large doses of UVB.

CONCLUSION

In vitro thin-film mechanical analysis techniques can readily characterize the effects of SC's exposure to UV radiation. The methods used in this study demonstrated commercial sunscreens were able to preserve the biomechanical properties of SC during UV exposure, thus indicating the barrier function of SC was also maintained.

Social networks, stress and health-related quality of life

Although evidence suggests that social networks reduce the risk of mortality and are negatively associated with severe mental disability, little is known about their relationship to everyday functioning and health-related quality of life (HRQoL). In addition, the importance of social networks in the presence of chronic stress remains unclear. We examined the association between social networks and aspects of mental functioning (mental health, vitality and role-emotional functioning) and the relationship between social networks and mental functioning in the presence of stressors. Multiple linear and logistic regression models were used to examine data in 47,912 middle-aged and older healthy women. The Medical Outcomes Study Shortform Health Survey measured dimensions of quality of life. We observed strong associations between levels of social networks and multivariate-adjusted quality of life scores, particularly in potentially high stress situations. Compared to the most socially integrated, women who were socially isolated had reductions in mental health and vitality scores of 6.5 and 7.4 points, respectively and a 60% increased risk of limitation in role-emotional functioning. Social networks are positively associated with mental functioning in women. This association is strongest for women reporting high levels of home and work stressors.

Functional electrostimulation in poststroke rehabilitation: a meta-analysis of the randomized controlled trials

OBJECTIVE

To assess the efficacy of functional electrical stimulation (FES) in the rehabilitation of hemiparesis in stroke.

DESIGN

A meta-analysis combined the reported randomized controlled trials of FES in stroke, using the effect size method of Glass, and the DerSimonian-Laird Random Effects Method for pooling studies.

SETTING

The included studies were published between 1978 and 1992. They were conducted in academic rehabilitation medicine settings.

PATIENTS

In all included studies, patients were in poststroke rehabilitation. The mean time after stroke varied from 1.5 to 29.2 months.

INTERVENTION

FES applied to a muscle or associated nerve in a hemiparetic extremity was compared to No FES.

MAIN OUTCOME MEASURE

Change in paretic muscle force of contraction following FES was compared to change without FES.

RESULTS

For the four included studies, the mean effect size was .63 (95% CI: .29, .98). This result was statistically significant (p < .05).

CONCLUSION

Pooling from randomized trials supports FES as promoting recovery of muscle strength after stroke. This effect is statistically significant. There is a reasonable likelihood of clinical significance as well.

Meta-analysis of randomized controlled trials of cranial electrostimulation. Efficacy in treating selected psychological and physiological conditions

To clarify the diverse published results of cranial electrostimulation (CES) efficacy, we conducted an extensive literature review that identified 18 of the most carefully conducted randomized controlled trials of CES versus sham treatment. For the 14 trials that had sufficient data, we used the techniques of meta-analysis to pool the published results of treating each of four conditions: anxiety (eight trials), brain dysfunction (two trials), headache (two trials), and insomnia (two trials). Because studies utilized different outcome measures, we used an effect size method to normalize measures which we then pooled across studies within each condition. The meta-analysis of anxiety showed CES to be significantly more effective than sham treatment (p < .05). Pooling did not affect results that were individually positive (headache and pain under anesthesia) or negative (brain dysfunction and insomnia). Most studies failed to report all data necessary for meta-analysis. Moreover, in all but two trials, the therapist was not blinded and knew which patients were receiving CES or sham treatment. We strongly recommend that future trials of CES report complete data and incorporate therapist blinding to avoid possible bias.

Biofeedback therapy in poststroke rehabilitation: a meta-analysis of the randomized controlled trials

OBJECTIVE

To assess the efficacy of biofeedback therapy in poststroke rehabilitation.

DESIGN

A meta-analysis of the reported randomized control trials of biofeedback therapy in poststroke rehabilitation was performed. Data were analyzed using the effect size method and pooled using the Der Simonian-Laird Random Effects Model. Study quality was assessed according to the method of Chalmers.

SETTING

All included studies were conducted in academically based rehabilitation settings.

PATIENTS

Patients were in the rehabilitative phase of their illness. The timing of the intervention from the acute event did vary greatly between and within studies.

INTERVENTION

Biofeedback therapy was applied to a paretic limb of patients in the study group. Both treatment and control groups received standard physical therapy.

MAIN OUTCOME MEASURE

Change in range of motion of a joint of a paretic limb as a result of treatment was examined. This measure was chosen after the eligible studies were evaluated for combinable end points.

RESULTS

A total of eight studies were included in the analysis. The mean effect size for change in lower extremity range of motion as a result of biofeedback therapy was 1.50 (95% confidence interval [CI]: -0.59, 3.59). For the upper extremity the effect size was 2.30 (95% CI: -1.06, 5.66). Both results were not significant at the p < .05 level. Statistical tests showed significant heterogeneity among studies, validating the use of the Random Effects Model.

CONCLUSION

Results of pooling available randomized control trials do not support the efficacy of biofeedback in restoring the range of motion of hemiparetic joints. Nevertheless, because the calculated mean effect sizes were large, with associated wide confidence intervals, the possibility of a type II error masking an important clinical benefit needs to be considered in evaluating this result.

Barnett continent intestinal reservoir. Multicenter experience with an alternative to the Brooke ileostomy

PURPOSE

Since 1988, surgeons at five hospitals have been performing the Barnett continent intestinal reservoir (BCIR). The BCIR includes modifications to the original Kock pouch, designed to reduce the incidence of valve slippage and fistula formation. Principle modifications include an intestinal collar, an isoperistaltic valve, and a lateral pouch design.

METHOD

This unique collaborative study includes 510 ulcerative colitis or familial polyposis patients, with a follow-up time from one to five years postoperatively.

RESULTS

Ninety-two percent still have functioning reservoirs. Six and one-half percent have had their pouches removed and replaced with conventional Brooke ileostomies. Reoperation rate for major pouch-related complications (other than pouch removal) was 12.8 percent. These complications included slipped valve (6.3 percent), valve fistulas (4.5 percent), and pouch fistulas (6.3 percent). Several questions were administered to patients whose responses revealed a significant improvement in general quality of life, state of mind, and overall health.

CONCLUSIONS

The BCIR represents a successful alternative to patients with a conventional Brooke ileostomy or those who are not candidates for the ileal pouch-anal anastomosis.

Early angiography and angioplasty following thrombolytic therapy of acute myocardial infarction. Metaanalysis of the randomized control trials

STUDY OBJECTIVE

There have been at least 10 randomized control trials (RCTs) of early intervention in patients with acute myocardial infarction published, and all are inconclusive with regard to impact on mortality. Metaanalysis offers an opportunity to assess the efficacy of an early intervention following thrombolytic therapy in the treatment of acute myocardial infarction.

DESIGN

Data on the number of patients who died in the hospital, and the total number of patients randomized to aggressive versus conservative therapies, were drawn from 9 publications and combined using both a fixed and a random-effects metaanalysis model. Quality of the trials was assessed under blinded conditions.

SETTING

The 10 RCTs to be combined were each carried out in individual institutions.

PATIENTS

A total of 5882 patients have been randomized, with 305 deaths (5.2%), indicating that this group of patients had a relatively low mortality rate compared to patients in general with acute myocardial infarction. COMPARISON OF TREATMENTS: No matter how the 10 trials were combined for analysis, there was no evidence that aggressive intervention was trending towards saving lives. Data on other endpoints such as need for repeat percutaneous transluminal coronary angioplasty (PTCA), coronary artery bypass grafting (CABG), or recurrent myocardial infarction were sparse, but the same adverse trend was apparent.

CONCLUSION

In spite of the fact that early angiography and PTCA when indicated have been advocated for more than a decade, there is still no evidence that they reduce overall mortality after fibrinolysis in a specific subgroup. Further studies of early intervention should be done in an effort to answer subgroup questions which include the search for appropriate timing and patient selection for PTCA after fibrinolysis. As more RCTs with mortality data are published they will be added to these metaanalyses in The Online Journal of Current Clinical Trials.

Survival from localized breast cancer. Variability across trials and registries

Age-specific (< 50, 50-69 years) 10-year survival proportions in four European trials for node-negative, Stage I and II breast cancer patients differ significantly. These patients, identified as having the same stage as localized-breast cancer patients in the End Results Registry of the U.S. National Cancer Institute, had pooled survival proportions for the two age groups (0.713, 0.579) close to those of the registry (0.713, 0.607).

Growth in "new" vegetarian preschool children using the Jenss-Bayley curve fitting technique

Length and weight measurements obtained on 142 vegetarian and 229 nonvegetarian school children from a normative population were fitted to growth curves using the asymptotic nonlinear regression equation of Jenss and Bayley. All of the children were Caucasian and age ranged from a few weeks to 6 yr. The growth curves obtained for vegetarian children were from 0.5 to 1.0 kg and 1 to 2 cm lower, depending on age, sex, and diet, than were curves for reference populations of nonvegetarian children. Length was affected more than weight. Macrobiotic vegetarian children's curves were more depressed than those of the other vegetarian children, indicating that there was a good deal of heterogeneity in growth within vegetarians which was associated with dietary group characteristics. Measurements of females were more consistently affected than males, and their diets were also more far reaching with respect to animal food avoidances. The analysis of food records available provided evidence that energy intakes of the vegetarians were below recommended levels, whereas protein intakes did not appear to be limiting.