Dermatology in black skin

The vast majority of publications in dermatology refer to lightly pigmented skin, with few addressing the peculiarities of black skin. In addition there is no consensus on what it means to be black in different regions of the world. The lack of knowledge on the subject makes it difficult to recognize and manage dermatoses in this type of skin. This article aims to review the literature on intrinsic characteristics, as well as epidemiological and clinical aspects of the cutaneous manifestations of different dermatoses in black skin. It was found that there are sometimes striking differences, in the structural, biological, and functional aspects when comparing lightly pigmented and black skin. There are also physiological changes that need to be recognized to avoid unnecessary interventions. Some dermatoses have a higher incidence in black skin, such as acne, eczema, dyschromia and dermatophytosis. On the other hand, several dermatoses are more specific to black skin, such as pseudofolliculitis barbae, keloid, dermatosis papulosa nigra, ulcers caused by sickle-cell anemia, dactylolysis spontanea, confluent and reticulated papillomatosis of Gougerot and Carteaud, and some diseases of the hair and scalp (including fragile and brittle hair, traction alopecia, folliculitis keloidalis nuchae, folliculitis dissecans and central centrifugal cicatricial alopecia). A spectrum of peculiar aspects of specific dermatoses, including sarcoidosis, lichen planus (with emphasis on the pigmentosus variant), psoriasis, lupus erythematosus, vitiligo, syphilis, pityriasis versicolor, and neoplasms are highlighted. In the latter, characteristics of basal cell carcinoma, squamous cell carcinoma, and melanoma are compared, in addition to highlighting unusual aspects of primary cutaneous T-cell lymphoma, endemic Kaposi sarcoma, and dermatofibrosarcoma protuberans.

Linear hair growth rates in preschool children

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.

Strain and Strain Recovery of Human Hair from the Nano- to the Macroscale

In this study, in operandi SAXS experiments were conducted on samples of human hair with a varying degree of strain (2% within the elastic region and 10% beyond). Four different features in the SAXS patterns were evaluated: The intermediate filament distance perpendicular to and the distance from the meridional arc in the load direction, as well as the distances of the lipid bilayer peak in and perpendicular to the load direction. From the literature, one concludes that polar lipids in the cuticle are the origin of the lipid peak in the SAXS pattern, and this study shows that the observed strain in the lipids is much lower than in the intermediate filaments. We support these findings with SEM micrographs, which show that the scales in the cuticle deform much less than the cortex. The observed deformation of the intermediate filaments is very high, about 70% of the macrostrain, and the ratio of the transverse strain to the longitudinal strain at the nanoscale gives a Poisson ratio of νnano = 0.44, which is typical for soft matter. This work also finds that by varying the time period between two strain cycles, the typical strain recovery time is about 1000 min, i.e., one day. After this period, the structure is nearly identical to the initial structure, which suggests an interpretation that this is the typical time for the self-healing of hair after mechanical treatment.

Recent omics advances in hair aging biology and hair biomarkers analysis

Aging is a complex natural process that leads to a decline in physiological functions, which is visible in signs such as hair graying, thinning, and loss. Although hair graying is characterized by a loss of pigment in the hair shaft, the underlying mechanism of age-associated hair graying is not fully understood. Hair graying and loss can have a significant impact on an individual's self-esteem and self-confidence, potentially leading to mental health problems such as depression and anxiety. Omics technologies, which have applications beyond clinical medicine, have led to the discovery of candidate hair biomarkers and may provide insight into the complex biology of hair aging and identify targets for effective therapies. This review provides an up-to-date overview of recent omics discoveries, including age-associated alterations of proteins and metabolites in the hair shaft and follicle, and highlights the significance of hair aging and graying biomarker discoveries. The decline in hair follicle stem cell activity with aging decreased the regeneration capacity of hair follicles. Cellular senescence, oxidative damage and altered extracellular matrix of hair follicle constituents characterized hair follicle and hair shaft aging and graying. The review attempts to correlate the impact of endogenous and exogenous factors on hair aging. We close by discussing the main challenges and limitations of the field, defining major open questions and offering an outlook for future research.

A systematic review on the lipid composition of human hair

Hair lipid composition varies by ethnic hair type and by hair layer. Lipids in the cuticle, cortex, and medulla of the hair shaft provide a protective barrier to environmental and chemical damage, prevent hair breakage and desorption, and affect the elastic and tensile properties of hair. The aim of this systematic review is to provide an overview of the lipid composition and ethnic differences of human hair, effects of external damage on lipid content and properties, and changes in hair lipid composition associated with disease states. PubMed/MEDLINE was searched up to March 2021 according to PRISMA guidelines for articles discussing the lipid content of human hair and effects of physical, chemical, or environmental damage, and disease. Fifty-nine articles investigating the lipid content of hair were included for review. Lipids affect fluid permeability, hydration, strength, and texture of ethnic hair fibers. Lipid loss is accelerated by hair-damaging treatments such as bleach, dye, perm, straightening, and surfactant use, and sun and aging processes, leading to dehydrated, breakable, disordered, and dull hair. Diseases including acne, alopecia, and breast, gastric, prostate, lung, and rectal cancers display elevated hair lipid levels. Lipids are vital in protection against damage and maintenance of healthy hair. Further studies are needed to investigate the effects of lipids on the structural properties of ethnic hair, and changes in hair lipid composition with various dermatologic and systemic diseases.

RNA-Seq Reveals the Roles of Long Non-Coding RNAs (lncRNAs) in Cashmere Fiber Production Performance of Cashmere Goats in China

Long non-coding RNAs (lncRNAs) are a kind of non-coding RNA being >200 nucleotides in length, and they are found to participate in hair follicle growth and development and wool fiber traits regulation. However, there are limited studies reporting the role of lncRNAs in cashmere fiber production in cashmere goats. In this study, Liaoning cashmere (LC) goats (n = 6) and Ziwuling black (ZB) goats (n = 6) with remarkable divergences in cashmere yield, cashmere fiber diameter, and cashmere color were selected for the construction of expression profiles of lncRNAs in skin tissue using RNA sequencing (RNA-seq). According to our previous report about the expression profiles of mRNAs originated from the same skin tissue as those used in the study, the cis and trans target genes of differentially expressed lncRNAs between the two caprine breeds were screened, resulting in a lncRNA-mRNA network. A total of 129 lncRNAs were differentially expressed in caprine skin tissue samples between LC goats and ZB goats. The presence of 2 cis target genes and 48 trans target genes for the differentially expressed lncRNAs resulted in 2 lncRNA-cis target gene pairs and 93 lncRNA-trans target gene pairs. The target genes concentrated on signaling pathways that were related to fiber follicle development, cashmere fiber diameter, and cashmere fiber color, including PPAR signaling pathway, metabolic pathways, fatty acid metabolism, fatty acid biosynthesis, tyrosine metabolism, and melanogenesis. A lncRNA-mRNA network revealed 22 lncRNA-trans target gene pairs for seven differentially expressed lncRNAs selected, of which 13 trans target genes contributed to regulation of cashmere fiber diameter, while nine trans target genes were responsible for cashmere fiber color. This study brings a clear explanation about the influences of lncRNAs over cashmere fiber traits in cashmere goats.

How different is human hair? A critical appraisal of the reported differences in global hair fibre characteristics and properties towards defining a more relevant framework for hair type classification

This review critically appraises the reported differences in human hair fibre within three related domains of research: hair classification approaches, fibre characteristics and properties. The most common hair classification approach is based on geo-racial origin, defining three main groups: African, Asian and Caucasian hair. This classification does not account sufficiently for the worldwide hair diversity and intergroups variability in curl, shape, size and colour. A global classification into eight curl types has been proposed but may be too complex for reproducibility. Beyond that, hair cross-sectional shape and area have been found to have an inverse relation to curl: straighter fibres are circular with larger cross-sectional area, whilst the curlier fibres are elliptical with smaller cross-sectional area. These geometrical differences have been associated with bilateral vs homogenous distribution of cortical cell in curly vs straight hair respectively. However, there is no sufficient data demonstrating significant differences in hair amino composition, but proteomic studies are reporting associations of some proteins with curly hair. Eumelanin's relative abundance has been reported in all hair colours except for red hair which has a high pheomelanin content. Higher tensile and fatigue strength of straight hair are reported, however, curly hair fragility is attributed to knotting, and crack and flow formations rather than the structural variations. African hair has been found to have the highest level of lipids, whilst the water sorption of Caucasian hair is the highest, and that of Asian hair the lowest. Not all comparative studies clearly report their hair sampling approaches. Therefore, to strengthen the robustness of comparative studies and to facilitate cross-study data comparisons, it is recommended that the following hair defining characteristics are reported in studies: hair cross sectional diameter/area, curl type, hair assembly colour, as well as where possible donor data (age/gender) and sample pooling approach.

Impact of hair type, hair sample weight, external hair exposures, and race on cumulative hair cortisol

The biomarker cortisol assesses the impact of biopsychosocial stressors that activate the stress response system. Hair has emerged as a valid and non-invasive means of gauging cumulative cortisol deposited over month-long periods of time. Established protocols for the extraction of hair cortisol are being validated and refined in humans, yet methodological information about hair characteristics on cortisol remains limited. In addition to external hair exposures (e.g. dye, time spent outside), we examined hair categorization or type (e.g. kinky, straight) by extending a hair typing methodology for scientific use that is currently popular among hair care professionals. We then examined the interaction between hair type and race on cortisol levels with a hair questionnaire. Three studies were pooled to investigate how sample weight, hair type, race, heat exposures, and hair treatments impacted cumulative hair cortisol concentrations. Study 1 consisted of Adult Kenyan Medical Workers (N = 44); Study 2 Mexican and Mexican Americans (N = 106); and Study 3 American Youth (N = 107). We found significantly higher cortisol in 5 mg of hair when compared to larger sample weights, and higher cortisol in those who spent more time outdoors. Cortisol concentrations differed between racial groups and varied by hair type; moreover, there were directional differences in cumulative cortisol from straighter to curlier hair types which depended on racial group. In addition to demonstrating the impact of relatively novel control factors like hair sample weight, outdoor exposure, and hair type, the present study illustrates the importance of disentangling hair type and race to understand variability in cumulative hair cortisol. These influences should be included in future studies that measure hair cortisol.

Impact of Processing Conditions on Rheology, Tribology and Wet Lubrication Performance of a Novel Amino Lipid Hair Conditioner

The objective of this work was to carry out a comprehensive evaluation of the performance of a novel cationic amino lipid surfactant, Brassicyl Valinate Esylate (BVE), in contrast to conventional alkyl quaternary ammonium surfactants (quats), through a study of the effects of process mixing speed on its overall rheological, tribological and wet lubrication performance in comparison to BTAC and CTAC, two cationic surfactants widely used in cosmetics. The major cosmetic application of cationic surfactants is in the preparation of hair conditioners. Hence, this analysis was done firstly by conducting tensile combing tests to evaluate reduction in wet lubrication which translates to conditioning performance. The combing results serve as a testing metric that adequately corresponds to consumer perception of conditioned hair. To correlate this technically, yield stress measurements were conducted to establish rheologic profiles of the conditioner formulations, and in vitro tribological testing of the emulsion systems between two steel surfaces were done to technically simulate the spreading and rubbing of conditioner on the hair. The effect of processing conditions on the formulations was then evaluated. BVE was found to be an effective conditioning surfactant suitable as an eco-friendly replacement for BTAC and CTAC in hair conditioner formulations. The results showed that higher shear mixing rates during formulation lead to poorer performance effects evident through decreased yield stress values, lower percentage reduction in combing force and a higher coefficient of friction.

Investigation of the molecular signature of greying hair shafts

OBJECTIVE

Hair greying (i.e. canitie) is a physiological process occurring with the loss of melanin production and deposition within the hair shafts. Many studies reported the oxidation as the main biological process underlying this defect of pigmentation. Even though the overall appearance and biomechanical properties of hairs are reported to be altered with greying, there is a lack of information about molecular modifications occurring in grey hair shafts. The aim of this study was thus to investigate the molecular signature and associated changes occurring in greying hair shafts by confocal Raman microspectroscopy.

METHODS

This study was conducted on pigmented, intermediate (i.e. grey) and unpigmented hairs taken from 29 volunteers. Confocal Raman microspectroscopy measurements were acquired directly on hair shafts.

RESULTS

Automatic classification of Raman spectra revealed 5 groups displaying significant differences. Hence, the analysis of the molecular signature highlighted the existence of 3 sub-groups within grey hair: light, medium and dark intermediate. Among molecular markers altered in the course of greying, this study identified for the first time a gradual modification of lipid conformation (trans/gauche ratio) and protein secondary structure (α-helix/β-sheet ratio), referring respectively to an alteration of barrier function and biomechanical properties of greying hair.

CONCLUSION

This study thus reports for the first time a highly specific molecular signature as well as molecular modifications within grey hair shaft.

Endogenous 1-H-Pyrrole-2,3,5-Tricarboxylic Acid (PTCA) in Hair and Its Forensic Applications: A Pilot Study on a Wide Multi-Ethnic Population

Over the years, several studies have shown that many factors are likely to affect the results of forensic hair analyses and complicate their interpretation. Among these factors, one of the major drawbacks in hair analysis is the affectability of deposited xenobiotics by cosmetic treatments, which could be eventually used to adulterate the sample. It is well known that some cosmetic treatments containing hydrogen peroxide, such as permanent dyeing or bleaching, lead to the formation of 1-H-pyrrole-2,3,5-tricarboxylic acid (PTCA), a melanin degradation product. Considering that PTCA is also an endogenous compound, spontaneously formed by natural oxidation of melanin, its only detection in hair is not enough to confirm a cosmetic oxidative treatment. For this reason, the aim of the present work was to develop and validate a reliable liquid-liquid extraction method in ultra-high-performance liquid chromatographic-tandem mass spectrometry for the determination of endogenous PTCA in hair from a wide multi-ethnic population (African, Arab, Asian-Pacific, Caucasian, Hispanic and Indian). According to previous studies, untreated hair samples showed a PTCA content of 8.54 ± 5.72 ng/mg (mean ± standard deviation [SD]), ranging between 0.44 and 23.7 ng/mg; after in vitro cosmetic bleaching, PTCA increased to 16.8 ± 6.95 ng/mg (range: 4.16-32.3 ng/mg). Comparing baseline PTCA levels of each subgroup with the others, we could not observe any statistically significant difference, except for Caucasians (P < 0.05), wherein the concentrations were lower. Further studies and a wider sampling are necessary to elucidate the role of PTCA as diagnostic marker of cosmetic hair treatment in forensic field.

Preliminary comparison of skin transcriptome from sheep with different wool fibre diameters

Context Wool is one of the most important animal fibres for the textile industry, and its diameter directly affects its economic value. However, the molecular mechanisms underlying wool fibre diameter (FD) in sheep have not been fully elucidated. Aims The aims of the work were to make an initial comparison of skin transcriptomes from sheep with wool of high and low FD, and to identify key genes affecting FD. Methods High-throughput RNA-Seq technology was employed to explore the skin transcriptome, using three sheep with fine wool (FD &lt;21.0 μm) and three sheep with coarse wool (FD &gt;27.0 μm). Key results We obtained 28607228 bp of clean sequence data, 78.9% (±3.8%) of which uniquely aligned to the reference genome across the six samples. In total, 19914 mRNA transcripts were expressed (FPKM &gt;0) in the six skin samples, among which were certain well-known genes involved in the skin–hair cycle, such as KRTAP7-1, KRT14, Wnt10b, Wnt2b, β-catenin and FGF5. Furthermore, 467 genes were significantly differentially expressed between the fine-wool and coarse-wool groups, including 21 genes with upregulated and 446 genes with downregulated expression in the sheep with lower FD. These differentially expressed genes were particularly enriched in the gene ontology processes related to lipid metabolism, skin development, differentiation and immune function (P &lt; 0.05). The biological processes were involved in collagen catabolism, negative regulation of macromolecule metabolism, steroid hormone stimulation and lipid metabolism. A significant Kyoto Encyclopedia of Genes and Genomes pathway involving the metabolism of lipids and lipoproteins was also enriched, revealing that lipid metabolism might be one of the key factors affecting FD. The expression of these differentially expressed genes that were involved in the metabolism of lipids and lipoproteins pathway was verified by quantitative real-time PCR (qPCR). The correlation between the mRNA expression level from qPCR and RNA-Seq data was 0.999 (P &lt; 0.001). Conclusions The 467 differentially expressed genes, especially those involved in lipid metabolism and immune function, may play key roles in wool follicle metabolism and the expression of wool FD. Implications This study provided valuable data for future studies aimed at elucidating the mechanisms that underlie wool follicle metabolism and wool FD. The work may also have implications for studies of the human hair follicle.

Asian Hair: A Review of Structures, Properties, and Distinctive Disorders

Asian hair is known for its straightness, dark pigmentation, and large diameter. The cuticle layer in Asians is thicker with more compact cuticle cells than that in Caucasians. Asian hair generally exhibits the strongest mechanical properties, and its cross-sectional area is determined greatly by genetic variations, particularly from the ectodysplasin A receptor gene. However, knowledge on Asian hair remains unclear with limited studies. This article aimed to review and summarize the characteristics and properties of Asian hair. It also aimed to discuss hair disorders including linear lupus panniculitis and pseudocyst of the scalp that occur distinctively in Asian populations.

The what, why and how of curly hair: a review

An attempt to understand and explain a peculiarity that was observed for curly fibres during experimentation revealed disparate literature reporting on several key issues. The phenotypical nature of curly fibres is only accurately understood within the larger scope of hair fibres, which are highly complex biological structures. A brief literature search produced thousands of research items. Besides the large amount of information on the topic, there was also great variability in research focus. From our review, it appeared that the complexity of hair biology, combined with the variety of research subtopics, often results in uncertainty when relating different aspects of investigation. During the literature investigation, we systematically categorized elements of curly hair research into three basic topics: essentially asking why fibres curl, what the curly fibre looks like and how the curly fibre behaves. These categories were subsequently formalized into a curvature fibre model that is composed of successive but distinctive tiers comprising the elements in curly hair research. The purpose of this paper is twofold: namely to present (i) a literature review that explores the different aspects of curly human scalp hair and (ii) the curvature fibre model as a systemized approach to investigating curly hair.

Cholesterol homeostasis: Links to hair follicle biology and hair disorders

Lipids and lipid metabolism are critical factors in hair follicle (HF) biology, and cholesterol has long been suspected of influencing hair growth. Altered cholesterol homeostasis is involved in the pathogenesis of primary cicatricial alopecia, mutations in a cholesterol transporter are associated with congenital hypertrichosis, and dyslipidaemia has been linked to androgenic alopecia. The underlying molecular mechanisms by which cholesterol influences pathways involved in proliferation and differentiation within HF cell populations remain largely unknown. As such, expanding our knowledge of the role for cholesterol in regulating these processes is likely to provide new leads in the development of treatments for disorders of hair growth and cycling. This review describes the current state of knowledge with respect to cholesterol homeostasis in the HF along with known and putative links to hair pathologies.

Lipid loses and barrier function modifications of the brown-to-white hair transition

BACKGROUND

The main objective of this study was to determine the lipid profile of brown and white Caucasian hair fibres and the effects of lipids on the properties of fibres.

MATERIALS AND METHODS

To determine the structures of white and brown hair lipid bilayers, cross sections of fibres of both hair types were examined using synchrotron-based μ-FTIR mapping. Dynamic vapour sorption (DVS) analyses were also performed to determine the differences in the barrier function of both fibres.

RESULTS

Spatial identification of lipids showed that a great amount of lipids was present in the medulla of fibres of both hair types, but important differences were also observed between cuticles of the different fibres. The cuticle of a white hair fibre showed a significant decrease in its lipid content, but did not show differences in the lateral packing order with respect to the cuticle of a brown hair fibre. The cortex and medulla of the white hair fibre also exhibited a significant decrease in its lipid content but with a higher lateral packing order than brown hair. Using DVS analysis, it was found that the water dynamics of white hair fibres differed from those of brown hair fibres, showing a decrease in their total capacity to absorb water and an increase in the velocity of the exchange of water with the environment.

CONCLUSION

The results of both techniques demonstrated a high correlation between the characteristics of the lipids located in the cuticle and the water dynamics of the fibres.

Structure of intermediate filament assembly in hair deduced from hydration studies using small-angle neutron scattering

Intermediate filaments (IFs) are ubiquitous in biological structures including hair. Small-angle neutron scattering (SANS) data from hydrated samples were used in this study to investigate the distribution of water in hair, and model the structure of the IF assembly. A main diffraction peak at a d-spacing of ∼90 Å, and two weaker reflections show that IFs are arranged in a ∼105 Å quasi-hexagonal lattice. Changes in the diffraction peaks show that only a small fraction of the water absorbed by hair enters between the IFs, and little water diffuses into the core of the IFs. The amount of water in the IF assembly increases rapidly up to 10% relative humidity (RH), and then slowly with further increase in RH. Most of the water appears to reside outside the IF assembly, in the voids and at the interfaces, and contribute to the central diffuse scattering. The IF assembly in the decuticled hair absorbs more water and is more ordered than that the native hair. This suggests that cuticle acts as a barrier, and might constrain the structure by compressing the cortex radially. Treatments with oils that are hydrophobic, heat treatment, and reduction of the S-S linkages that opens up the matrix by disulfide bond cleavage, all affect structure and water permeability. Coconut oil was found to impede hydration more than the soybean oil because of its ability to penetrate deeper into hair. A new model for the IF assembly that is sterically more favorable than the previous models is proposed.

External lipid function in ethnic hairs

OBJECTIVE

The main aim of this study is to characterize the external lipids of different ethnic hairs and to study the contribution of the exogenous lipids on their physicochemical properties.

METHODS

On the extraction procedure, sebaceous lipids from the exterior of the fiber are removed. The influence of those free lipids on the hair properties, such as contact angle, mechanical characteristics, and sorption of water, will be evaluated to determine permeation characteristics of the keratin fibers. Relationship with lipid order was also determined by infrared spectroscopy (IR).

RESULTS

Lipid extraction indicates the greatest amount of total lipids for African hair. Caucasian lipid extracts present the higher melting point and phase transition temperatures. This could be related to higher hydration and lower diffusion coefficient of the Caucasian fibers. A decrease in moisture was found in the lipid-extracted fibers. This diminution of the maximum water regain in all cases could be due to a higher water desorption. IR results indicate that Caucasian and moreover African native fibers present the most quantity of lipids, and the similar frequency of all fibers indicates a lamellar/orthorhombic order arrangement.

CONCLUSION

The hexane/tert-butanol extraction was demonstrated to modify not only cuticular but also cortex lipids. Exogenous lipid depletion in all fibers indicates a less water content and higher water desorption. However, lipid depleted Caucasian fibers presents an increase in the lipid order which could be related to the different saturation of the lipid extract and its improvement in breaking tenacity.

Pre-incubation in soil improves the nitrogen fertiliser value of hair waste

Global generation of human hair waste and its disposal at landfills could contribute to the leaching of nitrates into ground water. High concentrations of nitrogen (N) and other elements suggest that the waste could be a source of plant nutrients and differences in ethnic hair types could affect nutrient release and fertiliser value. The objective of this study was to determine the effects of hair type, as an N source, and pre-incubation time on dry-matter yield, nutrient uptake by spinach (Spinacia oleracea L.) and residual soil nutrients. Salons in Pietermaritzburg provided bulk African and Caucasian hair waste, without distinguishing age, sex, health status or livelihood of the individuals. The hair waste was analysed for elemental composition. A pot experiment was set up under glasshouse conditions. The hair waste was incorporated (400 kg N ha^-1) into a loamy oxisol and pre-incubated for 0, 28, 56 and 84 days before planting spinach. Potassium (K) and phosphorus (P) were corrected to the same level for all treatments. Spinach seedlings were then cultivated for 6 weeks. Shoot dry-matter and the uptake of all nutrients, except P, were increased by the pre-incubation of hair. African hair pre-incubated for 28 days resulted in greater dry-matter, N, K, Mn and S uptake than Caucasian hair. Increasing pre-incubation resulted in a decline in the residual soil pH and exchangeable K. The findings suggested that pre-incubation improves the N fertiliser value of hair and that African hair has greater value than Caucasian hair when pre-incubated for a short period.

Emerging Diagnostic and Therapeutic Potentials of Human Hair Proteomics

The use of noninvasive human substrates to interrogate pathophysiological conditions has become essential in the post- Human Genome Project era. Due to its high turnover rate, and its long term capability to incorporate exogenous and endogenous substances from the circulation, hair testing is emerging as a key player in monitoring long term drug compliance, chronic alcohol abuse, forensic toxicology, and biomarker discovery, among other things. Novel high-throughput 'omics based approaches like proteomics have been underutilized globally in comprehending human hair morphology and its evolving use as a diagnostic testing substrate in the era of precision medicine. There is paucity of scientific evidence that evaluates the difference in drug incorporation into hair based on lipid content, and very few studies have addressed hair growth rates, hair forms, and the biological consequences of hair grooming or bleaching. It is apparent that protein-based identification using the human hair proteome would play a major role in understanding these parameters akin to DNA single nucleotide polymorphism profiling, up to single amino acid polymorphism resolution. Hence, this work seeks to identify and discuss the progress made thus far in the field of molecular hair testing using proteomic approaches, and identify ways in which proteomics would improve the field of hair research, considering that the human hair is mostly composed of proteins. Gaps in hair proteomics research are identified and the potential of hair proteomics in establishing a historic medical repository of normal and disease-specific proteome is also discussed.

Effect of a peptide in cosmetic formulations for hair volume control

OBJECTIVE

The capacity of hair to absorb water causes changes in its physical and cosmetic properties under different environmental conditions. Hence, the control of hair volume in variable relative humidity settings is an important topic in cosmetics. The behaviour of two types of hair, Caucasian and Asian, was studied regarding their volume change in different relative humidity conditions. The ability of a peptide as a hair volume treatment was evaluated in two climate control formulations.

METHODS

Tresses of the two types of hair were tested in two relative humidity (RH) conditions: (A) variable relative humidity (2 h 40% RH, followed by 2 h 90% RH and 2 h of 40% RH), and (B) continuous high relative humidity (90% RH for 6 h). Changes in the hair tress volume were assessed throughout time. Hair treated with two climate control formulations, with and without a peptide (KP peptide), were tested under the two relative humidity conditions.

RESULTS

Caucasian hair had a higher change in volume compared to the Asian hair in variable and high relative humidity conditions. The hair volume increase when subject to high air humidity, and it was lower with the incorporation of a peptide into climate control formulations.

CONCLUSION

Caucasian hair showed higher volume than Asian hair when submitted to both relative humidity conditions. The incorporation of the peptide into the climate control formulations, a base (mostly composed of water ≈ 94%) and an ethanolic, was found to reduce the volume of Caucasian hair tresses. The presence of the peptide improved the hair volume change more than 60% in high relative humidity conditions.

Geometric classification of scalp hair for valid drug testing, 6 more reliable than 8 hair curl groups

INTRODUCTION

Curly hair is reported to contain higher lipid content than straight hair, which may influence incorporation of lipid soluble drugs. The use of race to describe hair curl variation (Asian, Caucasian and African) is unscientific yet common in medical literature (including reports of drug levels in hair). This study investigated the reliability of a geometric classification of hair (based on 3 measurements: the curve diameter, curl index and number of waves).

MATERIALS AND METHODS

After ethical approval and informed consent, proximal virgin (6cm) hair sampled from the vertex of scalp in 48 healthy volunteers were evaluated. Three raters each scored hairs from 48 volunteers at two occasions each for the 8 and 6-group classifications. One rater applied the 6-group classification to 80 additional volunteers in order to further confirm the reliability of this system. The Kappa statistic was used to assess intra and inter rater agreement.

RESULTS

Each rater classified 480 hairs on each occasion. No rater classified any volunteer's 10 hairs into the same group; the most frequently occurring group was used for analysis. The inter-rater agreement was poor for the 8-groups (k = 0.418) but improved for the 6-groups (k = 0.671). The intra-rater agreement also improved (k = 0.444 to 0.648 versus 0.599 to 0.836) for 6-groups; that for the one evaluator for all volunteers was good (k = 0.754).

CONCLUSIONS

Although small, this is the first study to test the reliability of a geometric classification. The 6-group method is more reliable. However, a digital classification system is likely to reduce operator error. A reliable objective classification of human hair curl is long overdue, particularly with the increasing use of hair as a testing substrate for treatment compliance in Medicine.

Hair from different ethnic groups vary in elemental composition and nitrogen and phosphorus mineralisation in soil

Disposal of hair wastes at landfills causes nitrate leaching to ground water, and use of the waste as fertiliser could be a viable option. This study was to determine elemental composition of major hair types in South Africa and their nitrogen (N) and phosphorus (P) release in soil. Wastes of African, White and Indian hair were obtained from local salons and analysed for carbon (C), N and sulphur (S) with the Leco CNS analyzer, and P, bases, aluminium (Al) and micronutrients, with the ICP. We also conducted an incubation study to determine changes in mineral N and P in soil. Hair wastes were added to soil at increasing rates based on N, incubated at 25 °C with destructive sampling after 0, 28, 56 and 84 days and pH, ammonium-N, nitrate-N and extractable P measured. All data were subjected to analysis of variance. Indian and White hair had higher N than African. White hair had higher C and lower potassium (K) than those of other types. The Fe levels in hair were in the order White > African > Indian, whilst those of Al were African > Indian > White. African hair had higher calcium (Ca), manganese (Mn), zinc (Zn) and cobalt (Co) than the other types. Ammonium-N and nitrate-N releases were in the order: Indian > African > White, especially at higher rates. Ammonium-N increased in the first 28 days and declined thereafter, when nitrate-N increased and pH decreased. The findings implied that hair types differ in elemental composition and nitrogen release in soil, with implications on pollution and soil fertility.

Methodological Considerations for Hair Cortisol Measurements in Children

BACKGROUND

Hair cortisol levels are used increasingly as a measure for chronic stress in young children. We propose modifications to the current methods used for hair cortisol analysis to more accurately determine reference ranges for hair cortisol across different populations and age groups.

METHODS

The authors compared standard (finely cutting hair) versus milled methods for hair processing (n = 16), developed a 4-step extraction process for hair protein and cortisol (n = 16), and compared liquid chromatography-mass spectrometry (LC-MS) versus enzyme-linked immunosorbent assays (ELISAs) for measuring hair cortisol (n = 28). The extraction process included sequential incubations in methanol and acetone, repeated twice. Hair protein was measured through spectrophotometric ratios at 260/280 nm to indicate the hair dissolution state using a BioTek plate reader and dedicated software. Hair cortisol was measured using an ELISA assay kit. Individual (n = 13), pooled hair samples (n = 12) with high, intermediate, and low cortisol values, and the ELISA assay internal standards (n = 3) were also evaluated by LC-MS.

RESULTS

Milled and standard methods showed highly correlated hair cortisol (rs = 0.951, P < 0.0001) and protein values (rs = 0.902, P = 0.0002), although higher yields of cortisol and protein were obtained from the standard method in 13 of 16 and 14 of 16 samples, respectively (P < 0.05). Four sequential extractions yielded additional amounts of protein (36.5%, 27.5%, 30.5%, 3.1%) and cortisol (45.4%, 31.1%, 15.1%, 0.04%) from hair samples. Cortisol values measured by LC-MS and ELISA were correlated (rs = 0.737; P < 0.0001), although cortisol levels [median (interquartile range)] detected in the same samples by LC-MS [38.7 (14.4-136) ng/mL] were lower than that by ELISA [172.2 (67.9-1051) ng/mL]. LC-MS also detected cortisone, which comprised of 13.4% (3.7%-25.9%) of the steroids detected.

CONCLUSIONS

Methodological studies suggest that finely cutting hair with sequential incubations in methanol and acetone, repeated twice, extracts greater yields of cortisol than does milled hair. Based on these findings, at least 3 incubations may be required to extract most of the cortisol in human hair samples. In addition, ELISA-based assays showed greater sensitivity for measuring hair cortisol levels than LC-MS-based assays.

Distribution of glycolipid and unsaturated fatty acids in human hair

It has been recognized that human hair lipids play crucial roles in the integrity of cells and matrices, while the details of distribution and structure of the minor lipids are hardly known. Here we investigated the lipids at the hair surface, at the interface between cuticle and cortex and in the interior of hair (cortex, medulla and melanin granules). Hair lipids and fatty acids and their metabolites were detected and characterized by using infrared spectroscopy and several mass spectrometry techniques (FTIR, ToF-SIMS, GCMS, and ESI-MS). As a result, it was found that unsaturated fatty acids were present more in the cortex of hair than at the hair surface. At the interface between cuticle and cortex, it is suggested that steryl glycoside-like lipids containing N-acetylglucosamine were present, and contributing to the adhesion between the cuticle and cortex of hair. Oxidative metabolites derived from integral fatty acids such as linoleic and alpha-linolenic acids were found in the hair bulb and melanin granules. Especially the oxidative metabolites of alpha-linolenic acid were integrated into the lipids non-covalently and tightly bound to melanin granules (namely, melanin lipids) and suggested as being involved in the biosynthetic processes of melanosome.

Internal lipids of felted, yellowed and pathologically thin wool

The keratin fibers contain small amount of the internal lipids which are in free state or bound with fiber proteins via tioester of 18-methyleicosanoic acid. Today the origin of these lipids, their composition and functional properties are still not found. Therefore, our objective was to examine the content and composition of internal lipids in sheep's wool with different defects. We observed that regardless of the type of fibers defect there are significant changes especially in the quality composition of the internal lipids, although the total content of free and covalently bound lipids in all cases is practically identical. Notably, both free and covalently bound lipids composition of felted and simultaneously felted and yellowed wool is characterized by changes in contents mainly of free fatty acids and ceramides whereas abnormal thinning of fibers is accompanied only by a decrease of sulfolipids.