Human hair keratins

Revitalizing Effect on the Scalp After Injection with a Mechanically Stabilized Hyaluronic Acid Complex in Subjects with Androgenetic Alopecia

Background: Treatments for androgenetic alopecia (AGA) include different drugs, but a treatment based on stabilized hyaluronic acid has not been tested. The aim of this study is to clinically evaluate the effect of six sessions of injections using a hyaluronic acid compound supplemented with vitamins, ions, and amino acids (CH) on hair density and quality in volunteers. Methods: For this purpose, twenty-six healthy volunteers of both sexes with moderate AGA were injected with 3 mL of CH using the micro-papule technique. All received six CH sessions at two-week intervals. Hair loss, hair thickness, and shine were assessed using macro-photographs. A follow-up questionnaire was given to the volunteers at 40 days and at 90 days after the last treatment to determine their level of satisfaction. In addition, a dermatological control was carried out to assess the tolerance of the treatment applied. Results: The results indicate that, after treatment with CH, there is a significant improvement in the thickness, shine, and density of scalp hair, and that the treatment significantly reduces hair loss on the scalp. On a dermatological level, the tolerability of the treatment was excellent with no complications observed. In total, 88.5% of the volunteers indicated that CH treatment improved their appearance. In summary, it can be said that CH treatment reduces hair loss and promotes hair growth. Conclusions: It is suggested that this treatment is effective in reducing the signs and symptoms of alopecia.

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

The surface and internal features of pubic hair: A comparative study with those of scalp hair

Although pubic hair has been a subject of public interest, little is known about its structure or characteristics beyond its curly and coarse appearance. In this study, we investigated the surface and internal features of pubic hair from Korean males and compared them to those of scalp hair from the same donors. Our findings indicate that the cuticle layer of pubic hair has a greater number of scales than that of scalp hair, resulting in a thicker cuticle layer overall. Fourier-transform infrared (FT-IR) spectroscopy analysis showed that the protein in the cortex layer of pubic hair was less affected by exposure to urine or ammonia than the protein in the cortex layer of scalp hair. This suggests that the cuticle layer of pubic hair, which is thicker and composed of more scales, acts as a physical barrier that protects the hair's internal structure. Furthermore, we observed that the secondary and tertiary structures of keratin in the pubic hair cuticle layer are essentially different from those in scalp hair. Based on these findings, we hypothesize that the thickened cuticle layer in pubic hair may have evolved as a defence mechanism against chemical damage from urine, urea and ammonia.

Green Composites Based on Animal Fiber and Their Applications for a Sustainable Future

Global climate change is already affecting the environment, as glaciers are receding, ice on rivers and lakes is melting, plant and animal range`s have altering, and trees are blooming early. Therefore, focus has shifted towards sustainable materials. There is a growing desire for materials that have a unique combination of qualities that metals, polymers, and other materials cannot provide, therefore scientists are turning their focus to green composites. Green composites offer a wide range of uses in automotive, aerospace, and marine applications. Composites are multiphase resources with separate interfaces that contain chemically different materials. Composites are made up of a variety of materials that are distinct in nature, and they give a set of desirable features that are superior to those of their predecessors or parents. Natural fibers are less expensive, more readily available, rust-resistant, plentiful, nontoxic, and safe for human skin, eyes, and respiratory systems. Green composites are created by combining renewable fibers with polymers (matrix) to create a new class of composites known as "green composites." This review includes studies on various animal-based fibers and their applications. In this article, recent advancements in the field of these fibers and their composites of fibers are also discussed. The physical, chemical, and mechanical properties are also discussed in this paper. Moreover, the benefits and drawbacks of using these fibers are also discussed in detail. Finally, the paper gives an outline of the topic. The results from composites constructed from each fiber are provided, along with appropriate references for more in-depth analysis studies. This review is specially performed to strengthen the knowledge bank of the young researchers working in the field of natural composites.

Understanding the Interaction of Gluconamides and Gluconates with Amino Acids in Hair Care

A hair care mixture formed from a gluconamide derivative and 3-hydroxypropyl ammonium gluconate is known to strengthen hair fibers; however, the mechanism by which the mixture affects hair is unknown. To give insight into the aggregation of the target gluconamide and potential interactions between the gluconate-derived mixture and hair fibers, a range of systems were characterized by X-ray crystallography namely two polymorphic forms of the target gluconamide and three salts of 3-hydroxypropylammonium with sulfuric acid, methane sulfonic acid, and oxalic acid. The gluconamide proves to aggregate and becomes a supramolecular gelator in aniline and benzyl alcohol solution. The resulting gels were characterized by rheology, scanning electron microscopy, proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and powder X-ray diffraction.

Dexamethasone-loaded keratin films for ocular surface reconstruction

Amniotic membrane (AM) is often applied as a substitute material during ocular surface reconstruction. However, since AM has several disadvantages, alternative materials must be considered for this application. Keratin films made from human hair (KFs) have previously been presented as a promising option; they exhibited suitable characteristics and satisfactory biocompatibility in an in vivo rabbit model. Nevertheless, dexamethasone (DEX) eye drops are necessary after surgery to suppress inflammation. Since eye drops must be administered frequently, this might result in poor patient compliance, and the release of DEX at the transplant site would be clinically beneficial. Therefore, we aimed to incorporate DEX into KFs without hindering the positive film characteristics. Drug-loaded KFs were generated either by suspension technique or by the addition of solubilizing agents. The resulting specimens were analyzed regarding appearance, loading capacity, transparency, mechanical characteristics, swelling behavior and in vitro release. Furthermore, biocompatibility was assessed in vitro by determining the cell viability, seeding efficiency and growth behavior of corneal epithelial cells. The amount of incorporated DEX influenced the transparency and biomechanical properties of the films, but even highly loaded films showed properties similar to those of AM. The suspension technique was identified as the best incorporation approach regarding chemical stability and prolonged DEX release. Moreover, suspended DEX in the films did not negatively impact cell seeding efficiencies, and the cell-growth behaviors on the specimens with moderate DEX loads were satisfactory. This suggest that these films could comprise a suitable alternative material with additional anti-inflammatory activity for ocular surface reconstruction. Graphical abstract.

Noyes-Whitney Dissolution Model-Based pH-Sensitive Slow Release of Paclitaxel (Taxol) from Human Hair-Derived Keratin Microparticle Carriers

This paper describes a convenient and straightforward method developed to extract keratin particles (KPs) from human hair. It also involves their characterization by several methods and encapsulation of the anticancer drug Paclitaxel (Taxol) within them, aiming for targeted delivery to cancerous sites and slow release at their vicinity. The KPs obtained were in micrometer in size. They are capable of encapsulating Taxol within them with a high encapsulation efficiency of 56% and a drug loading capacity of 2.360 g of Taxol per g keratin. As revealed by the SEM elemental analysis, KPs do not contain any toxic metal ion, and hence, they pose no toxicity to human cells. The pH-dependent release kinetics of the drug from KPs indicates that the drug is released faster when the pH of the solution is increased in the 5.0 to 7.0 pH range. The release kinetics obtained is impressive, and once targeted to the cancerous sites, using cancer directing agents, such as folic acid; a glutamate urea ligand known as DUPA; aminopeptidase N, also known as CD13; and FAP-α-targeting agents, the slow release of the drug is expected to destroy only the cancerous cells. The Noyes-Whitney dissolution model was used to analyze the release behavior of Taxol from KPs, which shows excellent fitting with experimental data. The pH dependence of drug release from keratin is also explained using the 3-D structures and keratin stability at different pH values.

Tuning the reversibility of hair artificial muscles by disulfide cross-linking for sensors, switches, and soft robotics

Tensile and torsional artificial muscles from biocompatible and biodegradable materials are highly desired for soft robotics, sensors, and controllers in bio-related applications. Twisted fibers can be used to prepare tensile and torsional artificial muscles, while torsional tethering is always required to avoid release of the inserted twist, which adds complexity to the device design. Moreover, the tuning of the reversibility of twisted fiber artificial muscles has not been realized. Here disulfide cross-linking was used to prepare novel tether-free hygroresponsive tensile and torsional fiber artificial muscles in twisted hair fibers. Increasing the cross-linking level converted the fiber artificial muscle from irreversible to reversible actuation. Different types of actuations including rotation, contraction, and elongation were realized for the twisted, the homochirally coiled, and the heterochirally coiled hair fibers, respectively. A reversible torsional fiber artificial muscle showed 122.4° mm^-1 rotation, homochiral and heterochiral fiber artificial muscles showed 94% contraction and 3000% elongation, respectively, and a maximum work capacity and energy density of 6.35 J kg^-1 and 69.8 kJ m^-3, respectively, were realized, on exposure to water fog. This work provides a new strategy for preserving the inserted twist in bio-fiber artificial muscles and for tuning of muscle reversibility, which show application perspectives in biocompatible smart materials, sensors, and robotics.

Smart and Sustainable Hair Products Based on Chitin-Derived Compounds

According to previous research studies, consumers worldwide are searching for new natural-oriented hair products that are both skin and environmentally friendly. Worldwide waste and air pollution, with the consequent environmental disasters, represent the greatest risk to human health and economy, further increased by the COVID-19 pandemic. Among others, non-biodegradable molecules are present in hair products (fossil-based additives, surfactants, etc.) and macromolecules (plastics). Plastics waste is considered the most serious problem, representing a forecast amount of 460 million tons per year by 2030, 12% of which is reused or recycled. Most plastics consumed, therefore, go to landfills and incineration, also if their recycling is considered an important driver of industrial profitability. Thus, the use of biopolymers represents an interesting alternative to produce biodegradable goods and tissues. After an introduction to the worldwide waste problem and the hair structure, the present review proposes the possibility to make biodegradable tissues that, realized by chitin nanofibrils and nano-lignin as natural polymers, may be used to produce an innovative and smart cosmetic hairline. Chitin-derived compounds are considered interesting polymers to produce non-woven tissues able to repair the hair damages provoked by the aggressiveness of both the environment and some aggressive cosmetic treatments, such as setting, bleaching, permanent waving, and oxidative coloring. The possible activity, that positively charged polymers such as chitin could have, has been speculated, interfering with the constitution and organization of the hair fibrils’ structure, which is negatively charged. The possibility of selecting biopolymers for their packaging is also discussed. Moreover, the use of these biopolymers, obtained from forestry-agro-food waste, may be of help to safeguard the further consumption of natural raw materials, necessary for future generations, also maintaining the earth’s biodiversity.

Structure of Keratin

Keratins, as a group of insoluble and filament-forming proteins, mainly exist in certain epithelial cells of vertebrates. Keratinous materials are made up of cells filled with keratins, while they are the toughest biological materials such as the human hair, wool and horns of mammals and feathers, claws, and beaks of birds and reptiles which usually used for protection, defense, hunting and as armor. They generally exhibit a sophisticated hierarchical structure ranging from nanoscale to centimeter-scale: polypeptide chain structures, intermediated filaments/matrix structures, and lamellar structures. Therefore, more and more attention has been paid to the investigation of the relationship between structure and properties of keratins, and a series of biomimetic materials based on keratin came into being. In this chapter, we mainly introduce the hierarchical structure, the secondary structure, and the molecular structure of keratins, including α- and β-keratin, to promote the development of novel keratin-based biomimetic materials designs.

A New Ex Vivo Model to Evaluate the Hair Protective Effect of a Biomimetic Exopolysaccharide against Water Pollution

As an external appendage, hair is exposed to multiple stresses of different origins such as particles and gases in air, or heavy metals and chemicals in water. So far, little research has addressed the impact of water pollution on hair. The present study describes a new ex vivo model that allowed us to document the adverse effects of water pollutants on the structure of hair proteins, as well as the protective potential of active cosmetic ingredients derived from a biomimetic exopolysaccharide (EPS). The impact of water pollution was evaluated on hair from a Caucasian donor repeatedly immersed in heavy metal-containing water. Heavy metal retention in and on hair was then quantified using Inductively Coupled Plasma Spectrometry (ICP/MS). The adverse effects of heavy metals on the internal structure of hair and its prevention by the EPS were assessed through measurement of keratin birefringence. Notably, the method allows the monitoring of the organization of keratin fibers and therefore the initial change on it in order to modulate the global damage in the hair. Results revealed an increasing amount of lead, cadmium and copper, following multiple exposures to polluted water. In parallel, the structure of keratin was also altered with exposures. However, heavy metal-induced keratin fiber damage could be prevented in the presence of the tested EPS, avoiding more drastic hair problems, such as lack of shine, or decrease in strength, due to damage accumulation.

Forensic determination of hair deposition time in crime scenes using electron paramagnetic resonance

Several types of biological samples, including hair strands, are found at crime scenes. Apart from the identification of the value and the contributor of the probative evidence, it is important to prove that the time of shedding of hair belonging to a suspect or victim matches the crime window. To this end, to estimate the ex vivo aging of hair, we evaluated time-dependent changes in melanin-derived free radicals in blond, brown, and black hairs by using electron paramagnetic resonance spectroscopy (EPR). Hair strands aged under controlled conditions (humidity 40%, temperature 20-22°C, indirect light, with 12/12 hour of light/darkness cycles) showed a time-dependent decay of melanin-derived radicals. The half-life of eumelanin-derived radicals in hair under our experimental settings was estimated at 22 ± 2 days whereas that of pheomelanin was about 2 days suggesting better stabilization of unpaired electrons by eumelanin. Taken together, this study provides a reference for future forensic studies on determination of degradation of shed hair in a crime scene by following eumelanin radicals by utilizing the non-invasive, non-destructive, and highly specific EPR technique.

A comparative study of materials assembled from recombinant K31 and K81 and extracted human hair keratins

Natural biopolymers have found success in tissue engineering and regenerative medicine applications. Their intrinsic biocompatibility and biological activity make them well suited for biomaterials development. Specifically, keratin-based biomaterials have demonstrated utility in regenerative medicine applications including bone regeneration, wound healing, and nerve regeneration. However, studies of structure-function relationships in keratin biomaterials have been hindered by the lack of homogeneous preparations of materials extracted and isolated from natural sources such as wool and hair fibers. Here we present a side-by-side comparison of natural and recombinant human hair keratin proteins K31 and K81. When combined, the recombinant proteins (i.e. rhK31 and rhK81) assemble into characteristic intermediate filament-like fibers. Coatings made from natural and recombinant dimers were compared side-by-side and investigated for coating characteristics and cell adhesion. In comparison to control substrates, the recombinant keratin materials show a higher propensity for inducing involucrin and hence, maturation in terms of potential skin cell differentiation.

Keratinous materials: Structures and functions in biomedical applications

Keratins are a family of fibrous proteins anticipated to possess wide-ranging biomedical applications due to their abundance, physicochemical properties and intrinsic biological activity. This review mainly focuses on the biomaterials derived from three major sources of keratins; namely human hair, wool and feather, that have effective applications in tissue engineering, wound healing and drug delivery. This article offers five viewpoints regarding keratin i) an introduction to keratin protein extraction and keratin-based scaffold fabrication methods ii) applications in nerve and bone tissue engineering iii) a review on the keratin dressings applied to different types of wounds to facilitate wound healing and thereby repair the skin iv) the utilization of keratinous materials as a carrier system for therapeutics with a controlled manner v) a discussion regarding the main challenges for using keratin in biomedical applications as well as its future prospects.

The Equine Hoof: Laminitis, Progenitor (Stem) Cells, and Therapy Development

The equine hoof capsule, composed of modified epidermis and dermis, is vital for protecting the third phalanx from forces of locomotion. There are descriptions of laminitis, defined as inflammation of sensitive hoof tissues but recognized as pathologic changes with or without inflammatory mediators, in the earliest records of domesticated horses. Laminitis can range from mild to serious, and signs can be acute, chronic, or transition from acute, severe inflammation to permanently abnormal tissue. Damage within the intricate dermal and epidermal connections of the primary and secondary lamellae is often associated with lifelong changes in hoof growth, repair, and conformation. Decades of research contribute to contemporary standards of care that include systemic and local therapies as well as mechanical hoof support. Despite this, consistent mechanisms to restore healthy tissue formation following a laminitic insult are lacking. Endogenous and exogenous progenitor cell contributions to healthy tissue formation is established for most tissues. There is comparably little information about equine hoof progenitor cells. Equine hoof anatomy, laminitis, and progenitor cells are covered in this review. The potential of progenitor cells to advance in vitro equine hoof tissue models and translate to clinical therapies may significantly improve prevention and treatment of a devastating condition that has afflicted equine companions throughout history.

Association between maternal exposure to phthalates and lower language ability in offspring derived from hair metabolome analysis

The fetus undergoes a crucial period of neurodevelopment in utero. The maternal hair metabolome provides an integrated record of the metabolic state of the mother prior to, and during pregnancy. We investigated whether variation in the maternal hair metabolome was associated with neurodevelopmental differences across infants. Maternal hair samples and infant neurocognitive assessments (using the Bayley III Scales of Infant Development at 24 months) were obtained for 373 infant-mother dyads between 26–28 weeks’ gestation from the Growing Up in Singapore Towards Healthy Outcomes cohort. The hair metabolome was analysed using gas chromatography-mass spectrometry. Intensity measurements were obtained for 276 compounds. After controlling for maternal education, ethnicity, and infant sex, associations between metabolites and expressive language skills were detected, but not for receptive language, cognitive or motor skills. The results confirm previous research associating higher levels of phthalates with lower language ability. In addition, scores were positively associated with a cluster of compounds, including adipic acid and medium-chain fatty acids. The data support associations between the maternal hair metabolome and neurodevelopmental processes of the fetus. The association between phthalates and lower language ability highlights a modifiable risk factor that warrants further investigation.

Hydrogels from feather keratin show higher viscoelastic properties and cell proliferation than those from hair and wool keratins

Hydrogel prepared from keratin shows potential applications in tissue engineering. However, the importance of the keratin sources has not been considered. The objectives of this study were to characterize and compare the rheological (storage modulus), physical (porosity, pore size, swelling capacity, and water contact angle) and in vitro cell compatibility of hydrogel scaffolds prepared from various keratin sources. Keratins were characterized by means of their molecular weight, amino acid composition, thermal and conformational properties. Hydrogels from chicken feather keratins demonstrated substantially higher storage modulus (G') than hair and wool keratin hydrogels. However, higher swelling capacity (>3000%) was determined in hair and wool over feather keratin (1500%) hydrogels. Our results suggest that small molecular weight and β-sheet conformation of feather keratin (~10 kDa) facilitated the self-assembly of rigid hydrogels through disulfide bond re-oxidation. Whereas, high molecular weight (10-75 kDa) stretchable α-helix conformation in hair and wool keratins resulted in weaker hydrogels. The cell cultures using fibroblasts showed the highest proliferation rate on chicken feather keratin hydrogel scaffolds. After 15 days of culture, partial breakdown of keratin fibers was observed. Results indicate that stiffer avian keratins can be used to fabricate more mechanically robust biomaterials than mammalian keratins.

Preparation and characterization of DOX loaded keratin nanoparticles for pH/GSH dual responsive release

Smart drug carriers are the current need of the hour in controlled drug delivery applications. In this work, pH and redox dual responsive keratin based drug-loaded nanoparticles (KDNPs) were fabricated through two-step strategies. Keratin nanoparticles were first prepared by desolvation method and chemical crosslinking, followed by electrostatic adsorbing doxorubicin (DOX) to afford drug loaded keratin nanoparticles (KDNPs). The size, size distribution, and morphology of the KDNPs were characterized with dynamic light scattering (DLS) and Scan electronic microscope (SEM). Drug delivery profiles showed that KDNPs exhibited pH and glutathione (GSH) dual-responsive characters. Under tumor tissue/cell microenvironments (more acidic and high GSH level), KDNPs tended to accumulate at the tumor region through a potential enhanced permeability and retention (EPR) effect and perform surface negative-to-positive charge conversion. Hemolysis assay indicated that KDNPs had good blood compatibility. Cellular uptake assay demonstrated that KDNPs could be internalized by A 549 cells through endocytosis. Intriguingly, KDNPs were capable of promoting nitric oxide (NO) release from endogenous donor of S-nitrosoglutathione in the presence of GSH. All of these results demonstrated that keratin based drug carriers had potential for drug/NO delivery and cancer therapy in clinical medicine.

Hair for brain trade-off, a metabolic bypass for encephalization

Hair loss in humans is perplexing and raises many hypothetical explanations. This paper suggests that hair loss in humans is metabolically related to encephalization; and that hair covered hominids would have been unable to evolve large brains because of a dietary restriction of several amino acids which are essential for hair and brain development. We use simulations to imply that hair loss must have preceded increase in brain size & volume. In this respect we see hair loss as a major force in human evolution. We assume that hair reduction required favorable climatic conditions and must have been quick. Using evolutionary and ecological time scales, we pinpoint hair loss to a period around 2.2-2.4 million years ago. The dating is further supported by a rapid selection at that time of the sialic acid deletion mutation which may have protected growing human brains against calcium ion flux. In summary we view encephalization, in part, as a metabolic trade-off between hair and brain. Other biochemical changes may have intervened in the process too; and the deletion mutation of sialic acid hydroxylation may have been involved as well.

Structure and mechanical properties of human trichocyte keratin intermediate filament protein

Keratin is a protein in the intermediate filament family and the key component of hair, nail, and skin. Here we report a bottom-up atomistic model of the keratin dimer, using the complete human keratin type k35 and k85 amino acid sequence. A detailed analysis of geometric and mechanical properties through full-atomistic simulation with validation against experimental results is presented. We introduce disulfide cross-links in a keratin tetramer and compare the mechanical behavior of the disulfide bonded systems with a system without disulfide bonds. Disulfide bond results in a higher strength (20% increase) and toughness (49% increase), but the system loses α-helical structures under loading, suggesting that disulfide bonds play a significant role in achieving the characteristic mechanical properties of trichocyte α-keratin. Our study provides general insight into the effect of disulfide cross-link on mechanical properties. Moreover, the availability of an atomistic model of this protein opens the possibility to study the mechanical properties of hair fibrils and other fibers from a bottom-up perspective.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry combined with multidimensional scaling, binary hierarchical cluster tree and selected diagnostic masses improves species identification of Neolithic keratin sequences from furs of the Tyrolean Iceman Oetzi

The identification of fur origins from the 5300-year-old Tyrolean Iceman's accoutrement is not yet complete, although definite identification is essential for the socio-cultural context of his epoch. Neither have all potential samples been identified so far, nor there has a consensus been reached on the species identified using the classical methods. Archaeological hair often lacks analyzable hair scale patterns in microscopic analyses and polymer chain reaction (PCR)-based techniques are often inapplicable due to the lack of amplifiable ancient DNA. To overcome these drawbacks, a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method was used exclusively based on hair keratins. Thirteen fur specimens from his accoutrement were analyzed after tryptic digest of native hair. Peptide mass fingerprints (pmfs) from ancient samples and from reference species mostly occurring in the Alpine surroundings at his lifetime were compared to each other using multidimensional scaling and binary hierarchical cluster tree analysis. Both statistical methods highly reflect spectral similarities among pmfs as close zoological relationships. While multidimensional scaling was useful to discriminate specimens on the zoological order level, binary hierarchical cluster tree reached the family or subfamily level. Additionally, the presence and/or absence of order, family and/or species-specific diagnostic masses in their pmfs allowed the identification of mammals mostly down to single species level. Red deer was found in his shoe vamp, goat in the leggings, cattle in his shoe sole and at his quiver's closing flap as well as sheep and chamois in his coat. Canid species, like grey wolf, domestic dog or European red fox, were discovered in his leggings for the first time, but could not be differentiated to species level. This is widening the spectrum of processed fur-bearing species to at least one member of the Canidae family. His fur cap was allocated to a carnivore species, but differentiation between brown bear and a canid species could not be made with certainty.

The use of hair as an indicator of occupational 14C contamination

This paper presents a study in which the specific activity of (14)C in hair has been investigated as an easily determined bio-indicator of the integrated (14)C exposure (over several months). The study includes 28 Swedish workers handling (14)C-labelled compounds, or working in a (14)C-enriched environment. Hair samples from personnel at a Swedish nuclear power plant showed very low levels of (14)C contamination, if any. In contrast, personnel at the investigated research departments showed (14)C levels in hair of up to 60% above the natural specific activity of (14)C. Much higher levels, up to 80 times the natural specific activity of (14)C, were found in hair from individuals working at a pharmaceutical research laboratory. This contamination was, however, not solely an internal contamination. There were indications that most of the (14)C in the hair originated from airborne (14)C-compounds, which were adsorbed onto the hair. The difficulties in removing this external (14)C contamination prior to analysis are discussed, as are the possibilities of using accelerator mass spectrometry to analyse various types of samples for retrospective dose assessment.

Methylated Metal(loid) Species in Humans

While the metal(loid)s arsenic, bismuth, and selenium (probably also tellurium) have been shown to be enzymatically methylated in the human body, this has not yet been demonstrated for antimony, cadmium, germanium, indium, lead, mercury, thallium, and tin, although the latter elements can be biomethylated in the environment. Methylated metal(loid)s exhibit increased mobility, thus leading to a more efficient metal(loid) transport within the body and, in particular, opening chances for passing membrane barriers (blood-brain barrier, placental barrier). As a consequence human health may be affected. In this review, relevant data from the literature are compiled, and are discussed with respect to the evaluation of assumed and proven health effects caused by alkylated metal(loid) species.

Mechanisms of mercury disposition in the body

Today the most widespread human exposures to mercury are to mercury vapor emitted from amalgam tooth fillings, to ethylmercury as a preservative in vaccines, and to methylmercury in edible tissues of fish. This review will focus on the mechanisms of transport of these three species of mercury. All three species are freely moveable throughout the body. Inhaled vapor in view of its physical properties as an uncharged atomic gas is believed to be transported by passive diffusion. Methylmercury and ethylmercury also move freely in the body. Methylmercury, and presumably its closely related chemical cousin ethylmercury, cross cell membranes as complexes with small molecular weight thiol compounds, entering the cell in part as a cysteine complex on the large neutral amino acid carriers and exiting the cell in part as a complex with reduced glutathione on endogenous carriers. The implications of these mechanisms with regard to biological monitoring are discussed.

Arsenic speciation in human hair: a new perspective for epidemiological assessment in chronic arsenicism

The analysis for arsenic in hair is commonly used in epidemiological studies to assess exposure to this toxic element. However, poor correlation between total arsenic concentration in hair and water sources have been found in previous studies. Exclusive determination of endogenous arsenic in the hair, excluding external contamination has become an analytical challenge. Arsenic speciation in hair appears as a new possibility for analytical assessing in As-exposure studies. This study applied a relative simple method for arsenic speciation in human hair based on water extraction and HPLC-HG-ICP-MS. The concentration of arsenic species in human hair was assessed in chronically As(V)-exposed populations from two villages (Esquiña and Illapata) of the Atacama Desert, Chile. The arsenic concentrations in drinking water are 0.075 and 1.25 mg L(-1), respectively, where As(V) represented between 92 and 99.5% of the total arsenic of the consumed waters. On average, the total arsenic concentrations in hair from individuals of Esquiña and Illapata were 0.7 and 6.1 microg g(-1), respectively. Four arsenic species, As(III), DMA(V), MMA(V) and As(V), were detected and quantified in the hair extracts. Assuming the found species in extracts represent the species in hair, more than 98% of the total arsenic in hair corresponded to inorganic As. On average, As(III) concentrations in hair were 0.25 and 3.75 microg g(-1) in Esquiña and Illapata, respectively; while, the As(V) average concentrations were 0.15 and 0.45 microg g(-1) in Esquiña and Illapata, respectively. Methylated species represent less than 2% of the extracted As (DMA(V)+ MMA(V)) in both populations. As(III) in hair shows the best correlation with chronic exposure to As(V) in comparison to other species and total arsenic. In fact, concentrations of As(total), As(III) and As(V) in hair samples are correlated with the age of the exposed individuals from Illapata (R= 0.65, 0.69, 0.57, respectively) and with the time of residence in this village (R= 0.54, 0.71 and 0.58, respectively).

Characterization of a 190-kilobase pair domain of human type I hair keratin genes

Polymerase chain reaction-based screening of an arrayed human P1 artificial chromosome (PAC) library using primer pairs specific for the human type I hair keratins hHa3-II or hHa6, led to the isolation of two PAC clones, which covered 190 kilobase pairs (kbp) of genomic DNA and contained nine human type I hair keratin genes, one transcribed hair keratin pseudogene, as well as one orphan exon. The hair keratin genes are 4-7 kbp in size, exhibit intergenic distances of 5-8 kbp, and display the same direction of transcription. With one exception, all hair keratin genes are organized into 7 exons and 6 positionally conserved introns. On the basis of sequence homologies, the genes can be grouped into three subclusters of tandemly arranged genes. One subcluster harbors the highly related genes hHa1, hHa3-I, hHa3-II, and hHa4. A second subcluster of highly related genes comprises the novel genes hHa7 and hHa8, as well as pseudogene PsihHaA, while the structurally less related genes hHa6, hHa5, and hHa2 are constituents of the third subcluster. As shown by reverse transcription-polymerase chain reaction, all hair keratin genes, including the pseudogene, are expressed in the human hair follicle. The transcribed pseudogene PsihHaA contains a premature stop codon in exon 4 and exhibits aberrant pre-mRNA splicing. Evolutionary tree construction reveals an early divergence of hair keratin genes from cytokeratin genes, followed by the segregation of the genes into the three subclusters. We suspect that the 190-kbp domain contains the entire complement of human type I hair keratin genes.

A splice site mutation in the gene of the human type I hair keratin hHa1 results in the expression of a tailless keratin isoform

In this study, we have elucidated the molecular mechanisms underlying the expression of an acidic 41-kDa protein inherited as an autosomal dominant trait of the hair keratin pattern of about 5% of the human population. We show that this protein is a size variant of the large type I hair cortex keratin hHa1 due to a genetic polymorphism in the hHa1 gene. We detected a G-A substitution in the 5' splice site of intron 6 of the hHa1 gene, which segregates with the 41-kDa protein phenotype in two pedigrees and is responsible for the formation of an abnormally spliced hHa1 mRNA species. The use of an alternative 5' splice site leads to the retention of 41 nucleotides of the initial intron 6 sequences in the mature transcript. The open reading frame of the aberrant mRNA creates a premature stop codon immediately downstream of the mutation site. The resulting hHa1 protein variant, hHa1-t, is about 6-kDa smaller than the 47-kDa hHa1 hair keratin and lacks the complete nonhelical tail domain. We show that the tailless hHa1-t is functional, since both recombinant hHa1 and hHa1-t form identical keratin intermediate filaments when assembled in vitro with a type II hair keratin partner. This finding confirms the view of a noninvolvement of the keratin tail domain in filament assembly and explains the lack of a pathological hair phenotype in hHa1-t positive individuals.