A long-term study of stable isotope ratios of fingernail keratin and amino acids in a mother-infant dyad

OBJECTIVE

To evaluate the potential of compound-specific isotope analysis of amino acids (CSIA-AA) for investigating infant feeding practices, we conducted a long-term study that compared infant and maternal amino acid (AA) nitrogen isotope ratios.

MATERIALS AND METHODS

Fingernail samples were collected from a single mother-infant dyad over 19 months postpartum. Carbon and nitrogen stable isotope ratios were measured in the bulk keratin of the fingernail samples. Selected samples were then hydrolyzed and derivatized for compound-specific nitrogen isotope analysis of keratin AAs.

RESULTS

As in previous studies, infant bulk keratin nitrogen isotope values increased during exclusive breastfeeding and fell with the introduction of complementary foods and eventual cessation of breastfeeding. Infant trophic AAs had elevated nitrogen isotope values relative to the mother, while the source AAs were similar between the mother and infant. Proline and threonine appeared to track the presence of human milk in the infant's diet as the isotopic composition of these AAs remained offset from maternal isotope values until the cessation of breastfeeding.

DISCUSSION

Although CSIA-AA is costly and labor intensive, it appears to hold potential for estimating the duration of breastfeeding, even after the introduction of complementary foods. Through the analysis of a full suite of AAs, it may also yield insights into infant physiology and AA synthesis.

Is Raman Spectroscopy of Fingernails a Promising Tool for Diagnosing Systemic and Dermatological Diseases in Adult and Pediatric Populations?

Background: Raman spectroscopy is a well-known tool used in criminology, molecular biology, and histology. It is also applied to diagnose bone mineral disorders by taking advantage of the similarity of the structure of keratin and bone collagen. Raman spectroscopy can also be used in dermatology and diabetology. The purpose of the present review is to critically evaluate the available research about the use of Raman spectroscopy in the mentioned areas of medicine. Methodology: PubMed was searched for peer-reviewed articles on the subject of use of Raman spectroscopy in bone mineral disorders, dermatology, and diabetes mellitus. Results: Nail keratin and bone collagen are related structural proteins that require disulfide bond for structural stability. Therefore, Raman spectroscopy of keratin may have potential as a diagnostic tool for screening bone quality and distinguishing patients at risk of fracture for reasons different from low bone mineral density (BMD) in the adult women population. Raman spectroscopy can also investigate the changes in keratin's structure in nails affected by onychomycosis and distinguish between healthy and onychomycosis nail samples. It could also reduce the need for nail biopsy by distinguishing between dermatophytic and non-dermatophytic agents of onychomycosis. Additionally, Raman spectroscopy could expedite the diagnostic process in psoriasis (by assessing the secondary structure of keratin) and in diabetes mellitus (by examining the protein glycation level). Conclusions: In adult populations, Raman spectroscopy is a promising and safe method for assessing the structure of fingernails. However, data are scarce in the pediatric population; therefore, more studies are required in children.

New Formulation-Microporation Combination Approaches to Delivering Ciclopirox across Human Nails

Topical treatments for onychomycosis are of interest to those seeking to avoid systemic drug interactions and to improve systemic safety. This work aimed to develop aqueous-based, simple, and cost-effective vehicles that provide high solubility for ciclopirox and enable the delivery of an active through channels created by nail microporation. Following solubility tests, aqueous gels and thermogels based on hydroxypropylmethylcellulose and poloxamer 407, respectively, were loaded with 8% and 16% ciclopirox. Their performance was then compared to the marketed lacquer Micolamina® in in vitro release tests with artificial membranes and in in vitro permeation tests with human nail clippings with and without poration. Finally, a microbiological assay compared the best gel formulations and the reference product. Little correlation was observed between the in vitro release and the permeation data, and the drug release was highly membrane-dependent. Ciclopirox nail retention in single-dose, porated nails tests was larger than in daily-dosing, non-porated nail conditions. The series of new gel and thermogel vehicles delivered ciclopirox more effectively than Micolamina® in single-dose, porated nail experiments. The inhibition of Trichophyton rubrum activity was significantly increased with microporated nails when the gel formulations were applied but not with Micolamina®. Overall, the results suggest that the new vehicles could be successfully combined with nail microporation to improve the drug delivery and efficacy of topical antifungal medication while reducing the dosing frequency, facilitating patients' adherence.

Comparative Analysis of Type I Keratin Expression By Nail Consistency: An Immunohistochemistry Study

The nail plate is one of the essential structures of the nail apparatus and is highly keratinized, making it difficult to handle this tissue experimentally. Different types of nail consistency were identified by applying distal pressure to the nail plate. To analyze the relationship between the keratins expressed in the nail plate and nail consistency, we chose a sample of 32 adult individuals (age 49.81±3.21 y) with the same number of each sex, who had a similar percentage of nail consistency types (56.25% hard consistency nails and 43.75% soft consistency nails). Immunohistochemical analyses showed that hard consistency nails contain more keratin 17 than soft consistency nails (P=0.026). These novel results allow nail consistency to be defined by the differential expression of keratins in the nail plate, and have potential clinical implications for the diagnosis of possible nail disorders and/or systemic disease.

Predictive Model of Nail Consistency Using Scanning Electron Microscopy with Energy-Dispersive X-Ray

Simple Summary

Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) is a useful technique to analyse elemental composition in the nail plate. The dorsal, intermediate, and ventral layers are differentiated by the levels of the elements present in each layer. The level of calcium in the dorsal layer is the main predictive variable in calculating the predictive model of consistency. This model will provide further knowledge of the factors that determine nail consistency in individuals and help health professionals to better understand nail characteristics and objectively determine nail consistency.

Abstract

The nail plate is made up of tightly packed keratin-rich cells. Factors such as the special distribution of the intermediate filaments in each layer (dorsal, intermediate, and ventral), the relative thickness of the layers, and their chemical composition define the characteristics of each nail. The main objective of this study is to determine nail consistency by calculating a predictive model based on elemental composition analysis using scanning electron microscopy. Nail consistency was determined in 57 participants (29 women and 28 men) in two age groups (young people and adults). Elemental composition was analysed in each layer using scanning SEM-EDS, and nail plate thickness was measured by image analysis. A total of 12 elements were detected in nail plates, of which carbon, nitrogen, phosphorus, sulphur, and calcium showed significant differences between layers (p-values ≤ 0.01). The level of calcium in the dorsal layer was the main predictive variable in calculating the predictive model of consistency, with 75.4% correctly classified cases. Elemental analysis in each layer of the nail plate by SEM-EDS can be used to develop a predictive model of nail consistency that will help health professionals to objectively determine nail consistency.

Solitary subungual neurofibroma with glomus tumor-like appearance: a case report

We present a case of subungual neurofibroma which clinically presented a glomus tumor-like appearance. Six months after surgical resection, no clinical recurrence or pain was reported. We herein report the difficulty of its preoperative diagnosis, including literature review.

Collision of Subungual Neurofibroma and Onychomatricoma: S100 Positivity as a Clue

We present a 41-year-old man with a hemionychodystrophy of the first toe, appearing as a longitudinal thickening of the nail plate, overcurved and with holes in its thickened free margin, thus leading to the clinical diagnosis of onychomatricoma. Complete excision showed typical nail plate of onychomatricoma and, underlying it, curvy disorganized neural-looking fascicles without atypia and with diffuse positivity for S100, interpreted as subungual neurofibroma (NF). Subungual NF is a very rare tumor, with only 12 previous cases reported. Its diagnosis is based on histopathology, as the tumor presents waves or whorls of disorganized neural-looking cells positive for S100. Regarding onychomatricoma, it is characterized by typical glove finger digitations (which were present in our case) and an underlying stroma composed by a cellular superficial layer (this layer expresses CD34 but not CD99) and a more sclerotic and deeper area. As we did not find information on S100 expression in the stroma of onychomatricoma, we have stained 4 typical cases, and all were negative with S100 and positive with CD34, as expected. In conclusion, as "subungual NF" is so rare and, in our case, seems to collide with a typical onychomatricoma, we recommend adding S100 staining to properly characterize tumors involving nail plate, to detect underlying neural tumors, as has happened in our case.

Nail bed solitary neurofibroma: A case report and literature review

RATIONALE

Nail bed solitary neurofibroma is an extremely rare tumor, with only 9 cases recorded in the literature so far.

PATIENT CONCERN

We present the case of a 42-year-old female patient, with a history of a slowly growing tumor in the nail bed of the left index and no clinical features of type I neurofibromatosis.

DIAGNOSIS

Nail bed solitary neurofibroma.

INTERVENTION

The tumor was surgically removed and the pathology examination established the diagnosis of neurofibroma.

OUTCOMES

The postoperative outcome was good, with no recurrence 12 months after surgery.

LESSONS

We present the rarity of this type of tumor localized in the nail bed, taking into consideration the only 9 cases recorded in the literature. Nail bed solitary neurofibroma should be also included in the differential diagnosis of a nail bed tumor.

Investigation of a correlation between taxane-based chemotherapy and the ultrasonic time-of-flight of human fingernails

BACKGROUND

Medical practitioners have long associated the physical appearance of human fingernails with certain underlying health conditions due to their direct connection to the vascular system. The objective of this study was to demonstrate how human fingernails can potentially be used as a biomarker to determine the severity of a patient's reaction to chemotherapy.

METHODS

Quantitative investigation of fingernails in patients undergoing taxane-based chemotherapy was conducted using a high-frequency 50 MHz ultrasound device in B-mode in the form of a pilot study. Time-of-Flight (TOF) ultrasonic signal measurements were recorded longitudinally across fingernails over three time intervals; (before treatment, in the middle of treatment, and on the last day of treatment); a neuropathy assessment and photographs were also taken for comparison.

RESULTS

A total of 17 patients were examined in this study with ages ranging from 35-69 years old with both weekly and biweekly chemotherapy regimens. Onycholysis and fingernail discoloration were observed in 8 of the 17 patients. White transverse lines and white lunula were observed on 4 of the 17 patients. Quantitative assessment revealed a TOF median decrease in fingernails during the first half of chemotherapy treatment; conversely, TOF median was found to have increased during the second half. Median TOF measurements at the end of treatment were found to return to approximately that of the baseline value.

CONCLUSION

This was a novel application of ultrasound in fingernails as chemotherapy biomarkers and further studies should be considered to verify and expand on the results obtained in this study.

Understanding the formidable nail barrier: A review of the nail microstructure, composition and diseases

The topical treatment of nail fungal infections has been a focal point of nail research in the past few decades as it offers a much safer and focused alternative to conventional oral therapy. Although the current focus remains on exploring the ways of enhancing permeation through the formidable nail barrier, the understanding of the nail microstructure and composition is far from complete. This article reviews our current understanding of the nail microstructure, composition and diseases. A few of the parameters affecting the nail permeability and potential causes of the recurrence of fungal nail infection are also discussed.

Transungual delivery: deliberations and creeds

Although considered as trifling illness, nail diseases have a reasonably high occurrence and a noteworthy impact on the patients' quality of life. Furthermore, there is a need to improve the topical treatment for nail diseases to avoid drug interactions and to reduce side effects associated with oral therapy. Topical drug delivery to the nails has established amplified consideration lately. Strategies (such as chemical enhancers, formulation strategies, physical and mechanical methods) are being investigated in order to improve drug permeability across the nail plate. The rationale of this review is to present contemporary information on the structure of human nail along with its comparison with animal hooves. Precincts of nail permeability have been briefly discussed with respect to factors like permeant's molecular size, hydrophilicity, charge and the nature of the vehicle. These factors affect drug uptake and permeation through the nail. Formulations like nail lacquers which mimic cosmetic varnish and colloidal carriers along with nail substitutes that can be utilized for transungual delivery have also been discussed.

Onychomycosis in patients of nail psoriasis on biologic therapy: a randomized, prospective open label study comparing Etanercept, Infliximab and Adalimumab

INTRODUCTION AND OBJECTIVE

The association between patients of psoriasis on anti TNF therapy and onychomycosis has not been explored. The aim of this study was to determine the rate of onychomycosis in patients of psoriasis with nail involvement on anti TNF therapy.

MATERIALS AND METHODS

All patients of psoriasis with nail involvement seen between February 2007 - July 2012 were examined. All the patients with negative nail scrapings for fungus were enrolled. Patients found fit for biologics after investigations were randomly divided into 3 groups (Group A: Infliximab, Group B: Etanercept and Group C: Adalimumab). The patients were followed up every 4 weeks for 24 weeks. Repeat nail scrapings were done at week 24. The results were compared with controls.

RESULT

In total, 315 (178 males and 137 females) patients were enrolled. The mean age was 37.5 ± 11.4 years. The results for scraping for fungus at the end of 24 weeks were as follows: 33% (33/100) in patients on Infliximab followed by 15.45% (17/110), 13.33% (14/105) in patients on treatment with Etanercept and Adalimumab respectively as compared to 13.89% (25/180) among controls. Onychomycosis in association with nail psoriasis was more common in males.

CONCLUSION

This study revealed statistically significant association between fungal infections of the nail in patients of psoriasis on treatment with Infliximab.

The human nail--barrier characterisation and permeation enhancement

The human nail remains one of the most challenging membranes for formulation scientists to target and for clinicians to heal. Its formidable barrier properties are the primary reason that oral therapy remains the primary approach to manage ungual infections. This article considers the major structural properties underlying the excellent barrier function of the nail, with particular emphasis on the role of biophysical methods in advancing our knowledge of this appendage. Formulations currently available for management of ungual disease are discussed and their therapeutic efficacy is assessed. Finally, experimental strategies to enhance ungual permeation are reviewed and prospects for future developments in the field are considered.

Solitary subungual neurofibroma in the right first finger

BACKGROUND

Neurofibromas may occur as part of neurofibromatosis or as a solitary tumor. Solitary subungual neurofibroma appears to be a rare condition. Up until now, less than 10 case reports of solitary subungual neurofibroma have been documented. Solitary subungual neurofibroma is difficult to diagnose, particularly as it is often small and without obvious symptoms. Awareness of the diagnosis is emphasized to prevent unnecessary delay in treatment. So, understanding the differentiation and diagnosis of solitary subungual neurofibroma has a great value.

METHODS

A 32-year-old woman presented with a two-year history of painless thickening and elevation of the nail plate of the right first finger. She was treated with complete surgical excision of the tumor, and we performed pathological examination of the biopsy specimen.

RESULTS

The final diagnosis of the tumor was solitary neurofibroma. After surgery, the nail regrew with a good cosmetic result. After 10months of follow-up, there were no signs of recurrence of the tumor.

CONCLUSION

Solitary subungual neurofibroma appears to be a rare condition, and immunohistochemistry is the key to the diagnosis. Complete surgical excision should be considered as the curative treatment of choice for them.

Iontophoretic drug delivery across the nail

INTRODUCTION

Topical drug delivery to treat nail diseases such as onychomycosis and psoriasis is receiving increasing attention. Topical nail delivery is challenged by the complicated structure of the nail and the low permeability of most drugs across the nail plate. Considerable effort has been directed at developing methods to promote drug permeation across the nail plate. Iontophoresis efficiently enhances molecular transport across the skin and the eye and is now being tested for its potential in ungual delivery.

AREAS COVERED

This review covers the basic mechanisms of transport (electro-osmosis and -migration) and their relative contribution to nail iontophoresis as well as the key factors governing nail permselectivity and ionic transport numbers. Methodological issues concerning research in this area are summarized. The data available in vivo on nail iontophoresis of terbinafine specifically are reviewed in separate sections.

EXPERT OPINION

Our understanding of nail iontophoresis has improved considerably since 2007; most decisively, the feasibility of nail iontophoresis in vivo has been clearly demonstrated. Future work is required to establish the adequate implementation of the technique so that its clinical efficacy to treat onychomycosis and nail psoriasis can be unequivocally determined.

Lyonization pattern of normal human nails

To examine the X-inactivation patterns of normal human nails, we performed the human androgen receptor gene assay of DNA samples extracted separately from each finger and toe nail plates of nine female volunteers. The X-inactivation pattern of each nail was unique and constant for at least 2 years. The frequency of nails with one of the two X-chromosomes exclusively inactivated was 25.9%. In the nails composed of two types of cells with either one X-chromosome inactivated, the two cell types were distributed in patchy mosaics. These findings suggest that the composition of precursor cells of each nail is maintained at each site at least through several cycles of regeneration time, and that the nail plate has a longitudinal band pattern, each band consisting of cells with only one of the two X-chromosomes inactivated. Using the frequency of nails with one of two X-chromosomes exclusively inactivated, we estimated the number of progenitor cells that gave rise to the nail plate during development to be about 3, under the assumption that the process follows the binominal distribution model. A strong correlation observed among the big, index and little fingers, and among the corresponding toes suggests an interesting interpretation concerning their morphogenetic process.

Histological microstructure of the claws of the African clawed frog,Xenopus laevis (Anura: Pipidae): implications for the evolution of claws in tetrapods

Claws are consistent components of amniote anatomy and may thus be implicated in the success of the amniote invasion of land. However, the evolutionary origin of these structures in tetrapods is unclear. Claws are present in certain extant non-amniotes, such as Xenopus laevis, the African clawed frog. The histology of the soft tissue component of the claws of X. laevis is described and compared with the amniote condition in order to gain new information on the question of homology of claws in these two groups based on patterns of keratinization. The X. laevis claw sheath is composed of a localized thickening of the corneous region of the epidermis that envelops the terminal phalanx. Noted differences between the non-cornified layers of the epidermis of the claw and non-claw region are the overall grainier appearance of the cells and an increased abundance of desmosomes in the intermediate spinosus cells. The biochemical identity of the sheath keratin(s) is inferred to be different from that of non-claw region epidermis, based on histological differences and differences in stain affinity between the two regions. The microstructure of the frog claw differs from that of amniotes in several respects, including the lack of a specified zone of growth near the base of the claw. Amphibians and amniotes, therefore, have very different patterns of claw sheath growth. Observations do not support homology of claws on a structural level in these two groups; however, further experimental work may confirm a conserved pattern of cornification in these structures in tetrapods.

Detection of breastfeeding and weaning in modern human infants with carbon and nitrogen stable isotope ratios

Carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios were longitudinally measured in fingernail and hair samples from mother-infant pairs where infants were exclusively breastfed (n = 5), breast- and formula-fed (n = 2), or exclusively formula-fed (n = 1) from birth. All exclusively breastfed infants had a dual enrichment in carbon ( approximately 1 per thousand) and nitrogen ( approximately 2-3 per thousand) when compared to maternal values. In contrast, breast- and formula-fed subjects had reduced enrichments compared to exclusively breastfed subjects, and the exclusively formula-fed infant showed no increase in delta(13)C or delta(15)N values. This finding of a carbon trophic level effect in breastfeeding infants suggests that (13)C-enrichments of approximately 1 per thousand in archaeological populations are not necessarily the result of the consumption of C(4)-based weaning foods such as maize or millet. During the weaning process, the delta(13)C results for breastfed infants declined to maternal levels more rapidly than the delta(15)N results. This suggests that delta(13)C values have the potential to track the introduction of solid foods into the diet, whereas delta(15)N values monitor the length of time of breast milk consumption. These findings can be used to refine the isotopic analysis of breastfeeding and weaning patterns in past and modern populations.

Brittle nail syndrome: a pathogenesis-based approach with a proposed grading system

Brittle nail syndrome is a heterogeneous abnormality, characterized by increased fragility of the nail plate. Brittle nails affect about 20% of the population and women are affected twice as frequently as men. The vast majority of patients experience brittle nails as a significant cosmetic problem and a substantial number indicate that these nail abnormalities are painful, impair daily activities, and may have a negative impact on occupational abilities. Pathogenic factors leading to brittle nails are factors that impair intercellular adhesion of the corneocytes of the nail plate or factors that cause a pathologic nail formation by involving the matrix. Clinical features of brittle nail syndrome are onychoschizia and onychorrhexis: the impairment of intercellular adhesive factors of the nail plate is expressed as onychoschizia, whereas the involvement of the nail matrix is expressed as onychorrhexis. Although impairment of life quality has not been evaluated for patients with brittle nail syndrome, the reduction of life quality in other nail problems has been studied and is evident. A proposed scoring system of key features of brittle nails is presented, and therapeutic approaches focussed on the pathogenic factors are discussed.

Onychocosmeceuticals

The nail is the largest skin appendage. In addition to its important physiological and sensory functions, it is also of great esthetic importance. Complaints of brittle or soft nails are frequent, particularly among women. Innumerable preparations claiming to improve the nail quality are being sold; however, most have no proven beneficial effect. Also, surgery cannot enhance nail quality but improve shape and size abnormalities.

A morphological study of ectopic plantar nail

Ectopic nails are rare. Four adult patients presented to us, affected by true ectopic nails of the foot, sole, and toes, occurring bilaterally in one case. Full documentation of these anomalies was collected. The aim of this study was to better describe the morphologic features of ectopic plantar nails by using, besides histologic evaluation, transmission and scanning electron microscopy. New morphologic criteria were identified to determine if ectopic plantar nail differed from normal and ectopic hand nails. Morphologically, ectopic plantar nails are smaller than normal ones, but still form cuticles, nail grooves and nail folds, and periungual wrinkles. Furthermore, they form with a flat angle between the nail matrix and proximal nail fold, and have a nail plate interrupted by several transverse nails grooves.

Fingernail clubbing and chromonychia associated with the use of angiotensin II receptor blockers

Fingernail clubbing and discoloration frequently indicate serious pulmonary, cardiovascular, and gastrointestinal pathologies. A 76-year-old Caucasian man developed clubbing of the fingernails and discoloration of both the fingernails and toenails after 27 days of treatment with the angiotensin II receptor blocker (ARB) losartan 50 mg/day. Even though this therapy was switched to valsartan, the nail changes persisted for another 6 months. The patient's therapy then was changed to captopril, and the changes gradually subsided over 17 months. An extensive literature search revealed no reports of this effect in association with ARBs. However, one manufacturer had received spontaneous reports. Despite careful consideration of other possible causes of the patient's symptoms, the temporal association with the start and discontinuation of ARB therapy suggests a possible drug-related adverse event.

Modulation of linear nail growth to treat diseases of the nail

Diseases affecting the nail can cause significant distress and interfere with an individual's self-esteem, personal relationships, and professional life. Often, hand and foot function is adversely affected. Certain diseases are characterized by accelerated nail growth while others show a decrease. In this review, drugs known to influence the growth rate of nails are examined, highlighting their potential use as adjunctive therapy in the treatment of nail disease. This approach, described recently in the context of the yellow nail syndrome,(1) may be extended to other common disorders such as nail psoriasis, brittle nails, and onychomycosis.

Evolution and development of mammalian limb integumentary structures

The adaptive radiation of mammalian clades has involved marked changes in limb morphology that have affected not only the skeleton but also the integumentary structures. For example, didelphid marsupials show distinct differences in nail and claw morphology that are functionally related to the evolution of arboreal, terrestrial, and aquatic foraging behaviors. Vespertilionoid bats have evolved different volar pad structures such as adhesive discs, scales, and skin folds, whereas didelphid marsupials have apical pads covered either with scales, ridges, or small cones. Comparative analysis of pad and claw development reveals subtle differences in mesenchymal and ectodermal patterning underlying interspecific variation in morphology. Analysis of gene expression during pad and claw development reveals that signaling molecules such as Msx1 and Hoxc13 play important roles in the morphogenesis of these integumentary structures. These findings suggest that evolutionary change in the expression of these molecules, and in the response of mesenchymal and ectodermal cells to these signaling factors, may underlie interspecific differences in nail, claw, and volar pad morphology. Evidence from comparative morphology, development, and functional genomics therefore sheds new light on both the patterns and mechanisms of evolutionary change in mammalian limb integumentary structures.

Diseases of the generative nail apparatus. Part I: Nail matrix

Disorders of the generative structures of the nail produce a characteristic set of outcomes. The matrix is the seat of nail development and diseases or insults of this germinative epithelium will tell a story in the signs that unfold in the ensuing nail growth. This story will be influenced by the intensity, duration and extent of this pathology. A method of categorizing changes associated with the generative matrix of the nail will be presented.

Investigation of nail permeation enhancement by chemical modification using water as a probe

Our objective was to screen molecules that could interact with keratin in the human nail and thereby improve the topical penetration of actives into and through the nail plate. We used specialized Franz-type diffusion cells for our permeation experiments and water as a marker molecule. Aqueous/hydroalcoholic gels containing the enhancers were spiked with tritiated water and compared with a control (without enhancer). We computed the normalized water flux (defined as a product of flux and nail thickness) for each gel. We defined an enhancement factor for water as the ratio of the normalized water flux from a gel containing enhancer to that of the control. Our results indicate that the chemical structure of the modifier is most important in determining its ability to enhance penetration. The best enhancement effect was obtained using N-(2-mercaptopropionyl) glycine, a mercaptan derivative of an amino acid, in combination with urea. The concentration of each chemical modifier was linearly related to normalized water flux and mercaptan levels were more important that urea levels in penetration enhancement. Barrier integrity of nails was compromised after treatment with effective chemical modifiers. Thus, we have developed a suitable technique to screen nail penetration enhancers using water as a probe.

Enhanced human nail drug delivery: nail inner drug content assayed by new unique method

The purpose of this study was to develop an assay method of the human inner nail plate and to compare nail drug penetration by a penetrating enhancing formulation (the test carrier formulation). The test carrier and saline formulations were tested using radiolabeled urea, ketoconazole, and salicylic acid. After twice dosing daily for 7 days on human nail plates, the under inner section of the nail plate was assayed for absorbed drug content using a unique drilling/removal system. Results show that the weight-normalized radioactivity contents of three chemicals in the inner intermediate nail plate center in the carrier formulation were two fold higher than those from saline (p < 0.05). Total radioactivity recovery of dosed [(14)C]-salicylic acid was 89 +/- 2% in the carrier formulation and 88 +/- 5% in saline. In saline formulation, salicylic acid showed greater binding to the outer nail, making it less bioavailable for the inner nail area. This didn't occur with carrier formulation. In conclusion, topical treatment of nail diseases such as onychomycosis is not yet sufficiently effective, likely because of minimal drug penetration into the inner nail plate where the disease perpetuates. The assay system has the unique characteristic of being able to assay the inner part of the nail where the disease resides.

Development and evolution of the mammalian limb: adaptive diversification of nails, hooves, and claws

Paleontological evidence indicates that the evolutionary diversification of mammals early in the Cenozoic era was characterized by an adaptive radiation of distal limb structures. Likewise, neontological data show that morphological variation in distal limb integumentary appendages (e.g., nails, hooves, and claws) can be observed not only among distantly related mammalian taxa but also among closely related species within the same clade. Comparative analysis of nail, claw, and hoof morphogenesis reveals relatively subtle differences in mesenchymal and epithelial patterning underlying these adult differences in distal limb appendage morphology. Furthermore, studies of regulatory gene expression during vertebrate claw development demonstrate that many of the signaling molecules involved in patterning ectodermal derivatives such as teeth, hair, and feathers are also involved in organizing mammalian distal limb appendages. For example, Bmp4 signaling plays an important role during the recruitment of mesenchymal cells into the condensations forming the terminal phalanges, whereas Msx2 affects the length of nails and claws by suppressing proliferation of germinal epidermal cells. Evolutionary changes in the form of distal integumentary appendages may therefore result from changes in gene expression during formation of mesenchymal condensations (Bmp4, posterior Hox genes), induction of the claw fold and germinal matrix (shh), and/or proliferation of epidermal cells in the claw matrix (Msx1, Msx2). The prevalence of convergences and parallelisms in nail and claw structure among mammals underscores the existence of multiple morphogenetic pathways for evolutionary change in distal limb appendages.

The lunula

The lunula is the visible portion of the distal nail matrix that extends beyond the proximal nailfold. It is white, half-moon-shaped, appears by week 14 of gestation, has unique histologic features. The lunula has a primary structural role in defining the free edge of the distal nail plate. Lunular anomalies include changes in form and structure and in color. Lunular dysmorphologic features can be characterized by macrolunula, microlunula or anolunula, and nonconvex lunula. Lunular dyschromias can be confluent or spotted or can be characterized by longitudinal colored bands that traverse the lunula. Alterations in the morphologic features or color (or both) of the lunula can be an indication of either a cutaneous or a systemic disorder.

Acquired nail beading in patients receiving itraconazole--an indicator of faster nail growth? A study using optical profilometry

Nail surfaces of toe-nail fragments were analysed by optical profilometry in patients treated with two different dosages of itraconazole: 200 mg continuous dosing for 12 weeks, or a pulse-dose regimen of 1 week per month of 400 mg itraconazole daily for 3-4 months. The use of the latter regimen seemed clinically to increase nail growth, which was accompanied in several patients by the occurrence of nail surface irregularities. This aspect was studied by computerized optical profilometry. Nail beading was characterized by a higher number of peaks and a larger mean roughness value (Ra). Such findings are reminiscent of other nail alterations resulting from a faster matrix turnover. A substantially greater number of peaks and larger Ra were found in the patients receiving the pulse treatment than in those receiving the continuous-dose regimen. Pulse therapy with itraconazole therefore appears to modify the structure of the nail plate, probably as a result of, or in association with, an increased rate of growth.

Surgical anatomy of the nail unit

A gross anatomic exploration of the nail unit was performed. The characteristic gross components of the nail unit and its relationship to the digital anatomy are described and presented in detail. Each segment of the nail unit is illustrated both photographically and with artistic illustration. It is our intention that through a simple gross dissection the nail structural unit may be better understood.

Nail disorders in children

The spectrum of nail abnormalities that may be seen in the pediatric population is discussed in this article. Developmental abnormalities, both hereditary and congenital, are discussed. Acquired nail abnormalities that may be similar to those seen in adults are also described.

Nail is produced by the normal nail bed: a controversy resolved

Nail thickness and mass (dry weight/unit surface area) of 21 toenails, removed from 19 patients after accidental injury, were measured over the mid point of the lunula, at the nail plate immediately distal to the lunula and at the distal end of the nail bed. Nail thickness increased from 43% of the final thickness over the mid-point of the lunula to 81% at its distal margin, the remaining increase in thickness being formed by the nail bed. The changes in nail mass were comparable. We conclude that ventral nail produced by the nail bed comprises about one-fifth of the terminal nail thickness and mass.

An abnormality of nail growth associated with median nerve damage

It has been recognised for a long time that damage to the median or ulnar nerves is usually followed by slowing of growth of the fingernails. In the past, this has always been ascribed to immobilization of the appropriate digits, rather than to a neurotrophic factor. No other nail changes appear to have been described in association with nerve damage. We present two patients with marked nail changes following median nerve injury, in which immobilization does not appear to be responsible.

Management of fingernail deformities after thermal injury

Fingernail deformities after thermal injury can be very disfiguring and troublesome. The fingernails may be discoloured, cleft or vertically deviated. From the pathophysiology of the nail growth in general, the specific features of the nail deformities after deep burn can be deduced, as can guidelines for the treatment. Over a two-year period, 153 patients with burned hands were treated in the Groningen Burn Centre. Seven of these patients developed abnormal quality and growth pattern of the fingernails. In two patients an effort was made to correct the deformity by incising the dorsal skin at the base of the nail fold, reflecting the nail fold and covering the acquired defect with a full thickness skin graft. Although the patients were satisfied with the results achieved, one year after the operation little or no improvement in the nail growth was found. A cautious policy should be followed in correcting these deformities, since dislocation of the eponychium together with damage to the nail matrix and the nail bed play a complex role in the process of deformation.