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Shape Variability and Classification of Human Hair: A Worldwide Approach
Abstract
Human hair has been commonly classified according to three conventional ethnic human subgroups, that is, African, Asian, and European. Such broad classification hardly accounts for the high complexity of human biological diversity, resulting from both multiple and past or recent mixed origins. The research reported here is intended to develop a more factual and scientific approach based on physical features of human hair. The aim of the study is dual: (1) to define hair types according to specific shape criteria through objective and simple measurements taken on hairs from 1442 subjects from 18 different countries and (2) to define such hair types without referring to human ethnicity. The driving principle is simple: Because hair can be found in many different human subgroups, defining a straight or a curly hair should provide a more objective approach than a debatable ethnicity-based classification. The proposed method is simple to use and requires the measurement of only three easily accessible descriptors of hair shape: curve diameter (CD), curl index (i), and number of waves (w). This method leads to a worldwide coherent classification of hair in eight well-defined categories. The new hair categories, as described, should be more appropriate and more reliable than conventional standards in cosmetic and forensic sciences. Furthermore, the classification can be useful for testing whether hair shape diversity follows the continuous geographic and historical pattern suggested for human genetic variation or presents major discontinuities between some large human subdivisions, as claimed by earlier classical anthropology.
... In addition, further 15 downy hair shafts were plucked from the loin from all six Mangalitza. On the day of collection, all hair shafts were treated and measured under the same environmental conditions according to the hair type-definition method suggested by De La Mettrie et al. (2007). Each hair shaft was fixed in-between two glass slides and investigated for the curvature of the hair, namely, the curve diameter (CD), using a template from Bailey & Schliebe (Bailey and Schliebe, 1986). ...
... Each hair shaft was fixed in-between two glass slides and investigated for the curvature of the hair, namely, the curve diameter (CD), using a template from Bailey & Schliebe (Bailey and Schliebe, 1986). Furthermore, the ratio of hair length when fully extended (L 2 ) over its natural length (L 1 ) was determined as the curl index (i = L 2 / L 1 ) (De la Mettrie et al., 2007). A larger curl index indicates curlier hair, whereas an index closer to one represents straighter hair. ...
... Furthermore, we highlighted the eligibility of the descriptive parameters, curve diameter, curly index, and the number of waves, for estimating the degree of curliness in pig hair. These parameters were originally developed for phenotyping human hair fibers (Bailey and Schliebe, 1986;De la Mettrie et al., 2007) and were previously used to categorize hair fibers from different parts of the body in pigs (Jiang et al., 2021). ...
Hair types have been under strong targeted selection in domestic animals for their impact on skin protection, thermoregulation and exterior morphology, and subsequent economic importance. In pigs, a very special hair phenotype was observed in Mangalitza, who expresses a thick coat of curly bristles and downy hair. Two breed-specific missense variants in TRPM2 and CYP4F3 were suggested to be associated with the Mangalitza pig’s hair shape due to their role in hair follicle morphogenesis reported for human and mice. However, the mechanism behind this expression of a curly hair type is still unclear and needs to be explored. In our study, hair shafts were measured and investigated for the curvature of the hair in Mangalitza and crossbreeds in comparison to straight-coated pigs. For molecular studies, hair roots underwent RNA sequencing for a differential gene expression analysis using DESeq2. The output matrix of normalized counts was then used to construct weighted gene co-expression networks. The resulting hair root gene expression profiles highlighted 454 genes to be significantly differentially expressed for initiation of curly hair phenotype in newborn Mangalitza piglets versus post-initiation in later development. Furthermore, 2,554 genes showed a significant differential gene expression in curly hair in comparison to straight hair. Neither TRPM2 nor CYP4F3 were identified as differentially expressed. Incidence of the genes in weighted co-expression networks associated with TRPM2 and CYP4F3, and prominent interactions of subsequent proteins with lipids and calcium-related pathways suggested calcium signaling and/or lipid metabolism as essential players in the induction of the curly hair as well as an ionic calcium-dependency to be a prominent factor for the maintenance of this phenotype. Subsequently, our study highlights the complex interrelations and dependencies of mutant genes TRPM2 and CYP4F3 and associated gene expression patterns, allowing the initiation of curly hair type during the development of a piglet as well as the maintenance in adult individuals.
... Mathematical aspects of continua were discussed at length in Science in an essay by Luce and Narens (1987), in which they concluded, "continuous variables are the correct kind of idealization for many, if not most, of the ordered empirical situations encountered in science. " Appropriately, a shift away from categorical thinking has occurred to some extent in many scientific disciplines as they have matured over time, among them botany (Curtis, 1951;Daubenmire, 1966;Vogl et al., 1966), population genetics (Parra et al., 2004;Shriver et al., 2005;de la Mettrie et al., 2007), genomic medicine (Pittman et al., 2004;Willard et al., 2005), gender studies (Hanson, 2000), quantum mechanics (Sachs, 1999), paleontology (Elgin, 1999), and sociology (Wong, 1997). ...
Sigmund Freud, Alfred Kinsey, E.O. Wilson, and others have suggested that social pressure suppresses natural tendencies for humans to express bisexuality, the apparent norm for one of our two closest genetic relatives, the bonobo. An analysis of data obtained from a new online sample of 1,150,938 people in 215 countries and territories (63.9% from the United States, United Kingdom, and Canada) who completed the English version of a validated questionnaire of sexual orientation lends support to this idea. A histogram of scores from 0 (exclusive opposite-sex inclinations) to 18 (exclusive same-sex inclinations) forms a near-normal distribution. Although this distribution was likely caused to some extent by sampling bias, it may also reflect the unusual honesty people show when taking online tests anonymously, as an increasing body of evidence demonstrates. We present a formal mathematical expression of a social pressure theory of sexual orientation, along with empirical evidence and computational explorations that support the theory. We also present an analysis of the new data set. Among other findings: sexual orientation labels corresponded to broad, skewed, overlapping distributions of scores. Self-labeled gays/lesbians and, to a greater extent, self-labeled straights, reported that the larger the mismatch between their sexual orientation label and their actual sexual inclinations, the more distress they felt regarding their sexual orientation, a finding that is predictable from cognitive dissonance theory. Educating the public about the true nature of sexual orientation might quell the often rancorous public debates on this topic, as well as give comfort to a large number of mislabeled people.
... Differences Are also related to the hair's form, which can be Straight, helical, or wavy; color, depending on the Balance of different types of melanin (brown to black, Indolic eumelanin, and yellow to reddish brown, pheomelanin); length; diameter; and crosssectional [3,6,7] Human hair is usually classified according to three conventional ethnic human subgroups, i.e., African, Asian and European. Nevertheless, a recent study showed that it is possible to classify the various hairs found worldwide into eight main coherent hair types, by the measurements of three easily accessible parameters: curve diameter; curve index; and number of wave [8] Alopecia Alopecia is a distressing dermatological disorder characterized by hair loss. Although hair Severe no critical physiological function in humans, hair loss can be psychological Devastating and adversely affect the selfconfidence of the patient [9] . ...
To study the hair promoting activity of Helianthus annuus in testosterone induced alopecia in mice model. Objective: The objective of this research include to find an alternative for present allopathic medication to minimize side effects and adverse drug reactions, there is no study has been carried out on Helianthus annuus so far Therefore, the present study used to evaluate hair growth promoting activity using testosterone induced alopecia. Material and Method: Swiss albino mice of either sex weighing 25-30 gm were used. Minoxidil (2%) solution purchased from market. This is the standard drug used for Alopecia. Testosterone (1ml ampoule) were purchased from Matoshri medical, Walgaon. It is used to induced alopecia in mice. Result: The histological study showed that hair density was maximum i.e. 2.833 ± 0.1667 in case of standard, 2.167 ± 0.1667 in case of Helianthus annuus oil 100ml/kg, 2.667 ± 0.2108 in case of Helianthus annuus oil 200 ml/kg, 2.167 ± 0.1667 in case of Negative control group while it was minimum i.e. 1.167 ± 0.3073 in testosterone treated animals.
Human hair is a natural fiber with keratin and keratin-related proteins as a main component. Externally, hair is a thin, pliable tube of dead, fully keratinized epithelial cells, while inside the skin, it is part of a single living hair follicle. In addition to a large amount of protein, hair also contains low levels of lipids and pigments. The hair also has its own ecological balance system. Although the lipid content in hair is much lower than the protein content, it plays an important role in hair and influences hair texture to some extent. For example, prevent hair breakage and thinning; To act as a barrier to moisture loss; and improve the gloss, elasticity and tensile strength of the hair stem. Environment, hair dressing and daily care can all cause hair damage to varying degrees. Factors such as ultraviolet light and chemicals can make hair dry, rough, dull, stiff and brittle by destroying the proteins, pigment sand lipid sin the hair. In this paper, the composition, classification and influencing factors of hair were reviewed. The composition and function of lipids in hair were investigated emphatically. It aims to improve people's understanding of the physical and chemical properties and structure of hair. It provides reference value for the research and development of hair cosmetics for different hair states and washing purposes. The function of hair lipids on hair is not accurate. In addition, there is still some controversy on the existing role of hair lipids, which needs further research.
Background:
Human scalp hair is a validated bio-substrate for monitoring various exposures in childhood including contextual stressors, environmental toxins, prescription or non-prescription drugs. Linear hair growth rates (HGR) are required to accurately interpret hair biomarker concentrations.
Methods:
We measured HGR in a prospective cohort of preschool children (N = 266) aged 9-72 months and assessed demographic factors, anthropometrics, and hair protein content (HPC). We examined HGR differences by age, sex, race, height, hair pigment, and season, and used univariable and multivariable linear regression models to identify HGR-related factors.
Results:
Infants below 1 year (288 ± 61 μm/day) had slower HGR than children aged 2-5 years (p = 0.0073). Dark-haired children (352 ± 52 μm/day) had higher HGR than light-haired children (325 ± 50 μm/day; p = 0.0019). Asian subjects had the highest HGR overall (p = 0.016). Younger children had higher HPC (p = 0.0014) and their HPC-adjusted HGRs were slower than older children (p = 0.0073). Age, height, hair pigmentation, and HPC were related to HGR in multivariable regression models.
Conclusions:
We identified age, height, hair pigment, and hair protein concentration as significant determinants of linear HGRs. These findings help explain the known hair biomarker differences between children and adults and aid accurate interpretation of hair biomarker results in preschool children.
Impact:
Discovery of hair biomarkers in the past few decades has transformed scientific disciplines like toxicology, pharmacology, epidemiology, forensics, healthcare, and developmental psychology. Identifying determinants of hair growth in children is essential for accurate interpretation of hair biomarker results in pediatric clinical studies. Childhood hair growth rates define the time-periods of biomarker incorporation into growing hair, essential for interpreting the biomarkers associated with environmental exposures and the mind-brain-body connectome. Our study describes age-, sex-, and height-based distributions of linear hair growth rates and provides determinants of linear hair growth rates in a large population of children. Age, height, hair pigmentation, and hair protein content are determinants of hair growth rates and should be accounted for in child hair biomarkers studies. Our findings on hair protein content and linear hair growth rates may provide physiological explanations for differences in hair growth rates and biomarkers in preschool children as compared to adults.
We present an isotropic, hyperelastic model specifically designed for the efficient simulation of tightly coiled hairs whose curl radii approach 5 mm. Our model is robust to large bends and torsions, even when they appear at the scale of the strand discretization. The terms of our model are consistently quadratic with respect to their primary variables, do not require per-edge frames or any parallel transport operators, and can efficiently take large timesteps on the order of ~1/30 of a second. Additionally, we show that it is possible to obtain fast, closed-form eigensystems for all the terms in the energy. Our eigenanalysis is sufficiently generic that it generalizes to other models. Our entirely vertex-based formulation integrates naturally with existing finite element codes, and we demonstrate its efficiency and robustness in a variety of scenarios.
Cosmetics for perming hair are commonly used but have negative impacts on hair fibers. Repairing damaged hair with conditioners, hair oil, and hair masks can provide relief but cannot prevent injuries. Recent research has shown that proteins and amino acids can remodel hair's disulfide bonds. However, the permeation ability of proteins is limited, and amino acids may disrupt the secondary structure of hair keratins. Our study demonstrates that peptides can be safely, efficiently, and promisingly used for hair perming. A bioinspired peptide, PepACS (PepA-PepC-SPB), was designed through bioinformatics. It can interact with keratin's sulfhydryl group in situ to remodel disulfide bonds without affecting hair fiber's tensile properties. The potential of PepACS to repair cuticle injuries is also observed through scanning electron microscope visualization. Besides, linking PepACS with mCherry enables hair dyeing. This research suggests that biomaterials can be applied in the hair care industry. STATEMENT OF SIGNIFICANCE: Chemical perming products can have negative impacts on people's health and hair fibers, making it essential to explore alternative methods. Peptides treatment is a promising option, but synthesizing sulfur-rich short peptides for hair perming has not been demonstrated before. In this paper, we utilized bioinformatics to design bio-inspired peptides that can interact with hair keratins and form curled shapes. Our study demonstrates that bioinformatics tools can be utilized to design bioinspired peptides with unique functions. Sulfur-rich short peptides can be heterologously expressed with fusion strategies, and PepACS can securely bind hair fibers through disulfide bonds. Importantly, perming hair with 0.01% PepACS maintains the mechanical properties of hair, and dyeing hair with the fusion protein PepACS_mCh can be facilitated by ethanol. These findings suggest that the strategy of perming and dyeing hair through peptides is non-injurious, and the peptides used for repairing hair damage show tremendous potential.
Facial hair is a commonly desired feature for many individuals. Despite a breadth of dermatology literature covering strategies for removing facial hair, there are no known articles summarizing strategies for facial hair growth or reviewing common facial hair pathologies. Here, we assess Google Trends to describe significant increases in terms related to facial hair growth and maintenance over the last decade, suggesting an increased public interest on this topic. Next, we review ethnic differences in facial hair growth that may affect facial hair distribution, growth, and predisposition to certain facial hair pathologies. Lastly, we review studies on agents used for facial hair growth and review common facial hair pathologies.
ConspectusHair is a natural polymeric composite primarily composed of tight macrobundles of keratin proteins, which are highly responsive to external stimuli, similarly to the hydrogels and other natural fibrous gel systems like collagen and fibrin.Hair and its appearance play a significant role in human society. As a highly complex biocomposite system, it has been traditionally challenging to characterize and thus develop personal care products. Over the last few decades, a significant societal paradigm shift occurred among those with curly hair, accepting the natural morphological shape of their curls and styling their hair according to its innate, distinct, and unique material properties, which has given rise to the development of new hair classification systems, beyond the traditional and highly limited race-based distinction (Caucasian, Mongolian, and African). L'Oréal developed a hair typing taxonomy based on quantitative geometric parameters among the four key patterns─straight, wavy, curly, and kinky, but it fails to capture the complex diversity of curly and kinky hair. Acclaimed celebrity hair stylist Andre Walker developed a classification system that is the existing gold standard for classifying curly and kinky hair, but it relies upon qualitative classification measures, making the system vague and ambiguous of phenotypic differences. The goal of this research is to use quantitative methods to identify new geometric parameters more representative of curly and kinky hair curl patterns, therefore providing more information on the kinds of personal care products that will resonate best with them and thus maximize desired appearance and health, and to correlate these new parameters with its mechanical properties. This was accomplished by identifying new geometric and mechanical parameters from several types of human hair samples.Geometric properties were measured using scanning electron microscopy (SEM), photogrammetry, and optical microscopy. Mechanical properties were measured under tensile extension using a texture analyzer (TA) and a dynamic mechanical analyzer (DMA), which bears similarity to the common act of brushing or combing. Both instruments measure force as a function of applied displacement, thus allowing the relationship between stress and applied stretch ratio to be measured as a hair strand uncurls and stretches to the point of fracture. From the resulting data, correlations were made between fiber geometry and mechanical performance. This data will be used to draw more conclusions on the contribution that fiber morphology has on hair fiber mechanics and will promote cultural inclusion among researchers and consumers possessing curly and kinky hair.
A further inquiry on modern human origins, based on common genetic pool surveys of rigorously selected population samples and highly informative immunological polymorphisms, provides new evidence of an Occidental-Oriental population split as the origin of human gene pool divergencies. The most likely ancestral genetic profile is discussed in the context of the debate raised by preliminary DNA restriction fragment length polymorphism studies, which contradict the conclusions drawn from classical blood group analyses.
The alleged relationship between the cross sectional shape of the hair shaft and the form of the hair, eg, curly or straight hair, has been challenged. By serial sections of human hair follicles from ten patients representing the three biological races, the relation between the follicle form and the hair form was studied. Using three-dimensional computer-aided reconstruction it was demonstrated that the follicle form determines the hair form, eg, the Negroid follicle has a helical form, whereas that of the Oriental follicle is completely straight. The caucasoid follicle represent variation between these extremes. However, even a straight caucasoid follicle may produce a hair shaft that has an oval cross section.
Human hair is the subject of a remarkably wide range of scientific investigations. Its chemical and physical properties are of importance to the cosmetics industry, forensic scientists and to biomedical researchers. The fifth edition of this book confirms its position as the definitive monograph on the subject. Previous editions were recognized as “concise and thorough” (Journal of the American Chemical Society), “an invaluable resource” (Canadian Forensic Science Society Journal), and “highly recommended” (Textile Research Journal). Chemical and Physical Behavior of Human Hair is a teaching guide and reference volume for cosmetic chemists and other scientists in the hair products industry, academic researchers studying hair and hair growth, textile scientists and forensic specialists. Features of the Fifth Edition: Recent advances in the classification and characterization of the different proteins and genes in IF and keratin associated proteins in human hair are described. The mechanism and incidence of hair growth and loss and hair density vs. age of males & females are described for Asians, Caucasians and Africans in different scalp regions. Details of hair surface lipids and cuticle membranes provide a better understanding of the surface and organization of the CMC and its involvement in stress strain is presented. Recent evidence demonstrates a more bilateral structure in curly hair and a more concentric arrangement of different cortical proteins in straighter hair. SNPs involved in hair form (curl and coarseness) and pigmentation and genes in alopecia and hair abnormalities are described. The latest biosynthetic scheme for hair pigments and structures for these and the different response of red versus brown-black pigments to photodegradation is described. A new method for curvature on 2,400 persons from different countries and groups is used to assign curvature throughout this book. Additional data for age and effects on diameter, ellipticity, elastic modulus, break stress and other parameters are presented with much larger data sets featuring statistical analyses. Hair conditioning, strength, breakage, split ends, flyaway, shine, combing ease, body, style retention, manageability and feel parameters are defined and described. A new section of different life stages by age groups considering collective and individual changes in hair fiber properties with age and how these affect assembly properties.
We present first the main basic choices which are preliminary to any clustering and then the dynamic clustering method which gives a solution to a family of optimization problems related to those choices. We show then how these choices interfere in pattern recognition using three approaches: the syntactic approach, the logical approach and the numerical approach. For each approach we present a practical application.
