Effectiveness of Tai Chi for Health Promotion of Older Adults: A Scoping Review of Meta-Analyses.

Background. Tai Chi is a form of exercise that is accessible to people from different socioeconomic backgrounds, making it a potentially valuable activity for health promotion of older adults. Purpose. The objective of this scoping review was to summarize the current knowledge about the effectiveness of Tai Chi for older adults across a range of general health outcomes from published, peer reviewed, unique meta-analyses. Methods. Meta-analyses were retrieved from Medline, Embase, AMED, CINAHL, SPORTDiscus, PsychINFO, Web of Science, PubMed Health, and the Cochrane Library from database inception to late August 2019. Multistage deduplication and screening processes identified eligible full-length meta-analyses. Two people independently appraised 27 meta-analyses based on the GRADE system and organized results into 3 appendices subsequently collated into heterogeneous, statistically significant, and statistically insignificant tables. Results. "High" and "moderate" quality evidence extracted from these meta-analyses demonstrated that practicing Tai Chi can significantly improve balance, cardiorespiratory fitness, cognition, mobility, proprioception, sleep, and strength; reduce the incidence of falls and nonfatal stroke; and decrease stroke risk factors. Conclusions. Health care providers can now recommend Tai Chi with high level of certainty for health promotion of older adults across a range of general health outcomes for improvement of overall well-being.

Effect of shampoo, conditioner and permanent waving on the molecular structure of human hair.

The hair is a filamentous biomaterial consisting of the cuticle, the cortex and the medulla, all held together by the cell membrane complex. The cortex mostly consists of helical keratin proteins that spiral together to form coiled-coil dimers, intermediate filaments, micro-fibrils and macro-fibrils. We used X-ray diffraction to study hair structure on the molecular level, at length scales between ∼3-90 Å, in hopes of developing a diagnostic method for diseases affecting hair structure allowing for fast and noninvasive screening. However, such an approach can only be successful if common hair treatments do not affect molecular hair structure. We found that a single use of shampoo and conditioner has no effect on packing of keratin molecules, structure of the intermediate filaments or internal lipid composition of the membrane complex. Permanent waving treatments are known to break and reform disulfide linkages in the hair. Single application of a perming product was found to deeply penetrate the hair and reduce the number of keratin coiled-coils and change the structure of the intermediate filaments. Signals related to the coiled-coil structure of the α-keratin molecules at 5 and 9.5 Å were found to be decreased while a signal associated with the organization of the intermediate filaments at 47 Å was significantly elevated in permed hair. Both these observations are related to breaking of the bonds between two coiled-coil keratin dimers.

The structure of people's hair.

Hair is a filamentous biomaterial consisting mainly of proteins in particular keratin. The structure of human hair is well known: the medulla is a loosely packed, disordered region near the centre of the hair surrounded by the cortex, which contains the major part of the fibre mass, mainly consisting of keratin proteins and structural lipids. The cortex is surrounded by the cuticle, a layer of dead, overlapping cells forming a protective layer around the hair. The corresponding structures have been studied extensively using a variety of different techniques, such as light, electron and atomic force microscopes, and also X-ray diffraction. We were interested in the question how much the molecular hair structure differs from person to person, between male and female hair, hair of different appearances such as colour and waviness. We included hair from parent and child, identical and fraternal twins in the study to see if genetically similar hair would show similar structural features. The molecular structure of the hair samples was studied using high-resolution X-ray diffraction, which covers length scales from molecules up to the organization of secondary structures. Signals due to the coiled-coil phase of α-helical keratin proteins, intermediate keratin filaments in the cortex and from the lipid layers in the cell membrane complex were observed in the specimen of all individuals, with very small deviations. Despite the relatively small number of individuals (12) included in this study, some conclusions can be drawn. While the general features were observed in all individuals and the corresponding molecular structures were almost identical, additional signals were observed in some specimen and assigned to different types of lipids in the cell membrane complex. Genetics seem to play a role in this composition as identical patterns were observed in hair from father and daughter and identical twins, however, not for fraternal twins. Identification and characterization of these features is an important step towards the detection of abnormalities in the molecular structure of hair as a potential diagnostic tool for certain diseases.

Hierarchical, self-similar structure in native squid pen.

The structure of native squid pen (gladius) was investigated in two different species on different length scales. By combining microscopy, atomic force microscopy (AFM), and X-ray diffraction, the experiments probed length scales from millimetres down to nanometres. The gladii showed a hierarchical, self-similar structure in the optical experiments with fibres of different size oriented along the long axis of the gladius. The fibre-like structure was reproduced at the nanoscale in AFM measurements and fibres with diameters of 500 µm, 100 µm, 10 µm, 2 µm and 0.2 µm were observed. Their molecular structure was determined using X-ray diffraction. In the squid gladius, the chitin molecules are known to form nano-crystallites of monoclinic lattice symmetry wrapped in a protein layer, resulting in ß-chitin nano-fibrils. Signals corresponding to the α-coil protein phase and ß-chitin crystallites were observed in the X-ray experiments and their orientation with respect to the fibre-axis was determined. The size of a nano-fibril was estimated from the X-ray experiments to be about 150 × 300 Å. About 100 of these nano-fibrils are needed to form a 0.2 µm thick micro-fibre. We found that the molecular structure is highly anisotropic with ∼90% of the α-coils and ß-chitin crystallites oriented along the fibre-axis, indicating a strong correlation between the macroscale structure and molecular orientation.

Self-assembly enhances the strength of fibers made from vimentin intermediate filament proteins.

Hagfish slime threads were recently established as a promising biomimetic model for efforts to produce ecofriendly alternatives to petroleum polymers. Initial attempts to make fibers from solubilized slime thread proteins fell short of achieving the outstanding mechanics of native slime threads. Here we tested the hypothesis that the high strength and toughness of slime threads arise from the ability of constituent intermediate filaments to undergo a stress-induced α-to-ß transition. To do this, we made fibers from human vimentin proteins that were first allowed to self-assemble into 10 nm intermediate filaments. Fibers made from assembled vimentin hydrogels underwent an α-to-ß transition when strained and exhibited improved mechanical performance. Our data demonstrate that it is possible to make materials from intermediate filament hydrogels and that mimicking the secondary structure of native hagfish slime threads using intermediate filament self-assembly is a promising strategy for improving the mechanical performance of biomimetic protein materials.