Thin Stratum Corneum Research Articles

Penetration of topically applied polymeric nanoparticles across the epidermis of thick skin from rat

The barrier function of the epidermis poses a significant challenge to nanoparticle-mediated topical delivery. A key factor in this barrier function is the thickness of the stratum corneum (SC) layer within the epidermis, which varies across different anatomical sites. The epidermis from the palms and soles, for instance, have thicker SC compared to those from other areas. Previous studies have attempted to bypass the SC layer for nanoparticle penetration by using physical disruption; however, these studies have mostly focused on non-thick skin. In this study, we investigate the role of SC-disrupting mechano-physical strategies (tape-stripping and microneedle abrasion) on thick and thin skin, in allowing transdermal penetration of topically applied nanoparticles using an ex-vivo skin model from rat. Our findings show that tape-stripping reduced the overall thickness of SC in thick skin by 87%, from 67.4 ± 17.3 μm to 8.2 ± 8.5 μm, whereas it reduced thin skin SC by only 38%, from 9.9 ± 0.6 μm to 6.2 ± 3.2 μm. Compared to non-thick skin, SC disruption in thick skin resulted in higher nanoparticle diffusion. Tape-stripping effectively reduces SC thickness of thick skin and can be potentially utilized for enhanced penetration of topically applied nanoparticles in skin conditions that affect thick skin.

Homogenous and multilayer electromagnetics models for estimating skin reflectance

<span>Reflectance measurements of human skin are widely limited over the millimeter wave (MMW) band in literature. This is due to the cost and technical difficulties of the experimental setup. This paper proposes homogenous and multilayer skin models for estimating the reflectance of the forearm and palm of the hand skin over the MMW band 30-100 GHz. The simulation results demonstrate that the differences in reflectance between the homogenous and multilayer models of forearm skin are limited to 0.014, indicating that the thin stratum corneum (SC) layer in the multilayer skin models has a minimal impact on the interaction with MMW of the forearm skin. However, in the palm of hand skin, there is a substantial difference in reflectance calculations between the homogenous and the multilayer skin models in the range of 0.099 to 0.143. These differences are attributed to the presence of a thick SC layer in the palm of the hand. Thus, the simulation results suggested that two-layer should be used for the palm of hand skin as it better captures the reflectance characteristics of this region. The importance of having those models are in calculating the skin reflectance that can be used for the non-invasive diagnosis of skin conditions.</span>

Photogallery. Pyoderma

Pyoderma is an acute (less often chronic) purulent inflammation of the skin, its appendages, and subcutaneous adipose tissue. Pyodermas are the most common skin diseases, accounting for 3040% of all skin diseases. According to the etiology, staphyloderma, streptoderma, streptostaphyloderma are distinguished.
 Staphyloderma is more common in men aged 45 to 65 years, who are diagnosed with 6070% of all cases of the disease; streptoderma ― more often in women and children with delicate skin and a thin stratum corneum.
 Along the course, pyoderma is divided into acute and chronic; according to the mechanism of occurrence into primary or secondary; according to the depth of the lesion into superficial, deep.
 Staphyloderma is usually associated with sebaceous hair follicles; pathogen ― more often Staphylococcus aureus (facultative anaerobe, lives in the mouths of follicles, sebaceous and sweat glands). Streptoderma is mainly caused by -hemolytic streptococcus (an obligate aerobe, present mainly on smooth skin, near natural openings and folds).

Transferosomal in situ gel administered through umbilical skin tissues for improved systemic bioavailability of drugs: A novel strategy to replace conventional transdermal route

Systemic bioavailability is of prime importance for most of the drugs that are administered via any route to produce required therapeutic efficacy. Many hydrophilic and lipophilic drugs have relied on parenteral and oral routes of administration for several treatments. However, these routes possess numerous disadvantages. Therefore, transdermal route of drug administration has come into existence as an alternative to parenteral and oral routes. Although many transdermal drug delivery systems have achieved better systemic bioavailability, they are associated with several disadvantages, such as poor skin permeability and retention. Additionally, the drugs that need to be administered in larger doses for sustained delivery are facing challenges. Generally, the transdermal formulations are applied on various skin regions (forearm, shoulder, thigh, back, etc.), other than the umbilicus, to deliver a drug into the systemic circulation. However, the supremacy of the umbilicus is that its skin tissues possess a thin stratum corneum and the presence of paraumbilical veins beneath the umbilical skin tissues enables rapid systemic distribution of drugs. The navel therapy has a practical history of more than 2000 years under Traditional Chinese Medicine. Several studies have witnessed the successful treatment of many digestive diseases by placing numerous herbal extracts on the umbilicus. An ample amount of works has compared the drug absorption through skin tissues at the umbilicus and forearm. Upon their results, it seemed the umbilicus could serve as an ideal region for better systemic bioavailability than other skin regions. Therefore, the present hypothesis aimed to put forward to deliver selected hydrophilic or lipophilic drugs through skin tissues at the umbilicus using a transferosomal in situ gel system for better systemic bioavailability than delivering drugs through other skin regions. Thus, the proposed hypothesis would produce better systemic bioavailability of many drugs.

Small nerve fiber selectivity of laser and intraepidermal electrical stimulation: A comparative study between glabrous and hairy skin

ObjectivesIn clinical neurophysiology practice, various methods of stimulation can be used to activate small-diameter nociceptive cutaneous afferents located in the epidermis. These methods include different types of laser and intraepidermal electrical stimulation techniques. The diffusion of the stimulation in the skin, inside or under the epidermis, depends on laser wavelength and electrode design, in particular. The aim of this study was to compare several of these techniques in their ability to selectively stimulate small nerve fibers. MethodsIn 8 healthy subjects, laser stimulation (using a CO2 or Nd:YAP laser) and intraepidermal electrical stimulation (using a micropatterned, concentric planar, or concentric needle electrode), were applied at increasing energy or intensity on the dorsal or volar aspect of the right hand or foot. The subjects were asked to define the perceived sensation (warm, pinprick, or electric shock sensation, corresponding to the activation of C fibers, Aδ fibers, or Aβ fibers, respectively) after each stimulation. Depending on the difference in the sensations perceived between dorsal (hairy skin with thin stratum corneum) and volar (glabrous skin with thick stratum corneum) stimulations, the diffusion of the stimulation inside or under the epidermis and the nature of the activated afferents were determined. ResultsRegarding laser stimulation, the perceived sensations turned from warm to pinprick with increasing energies of stimulation, in particular with the Nd:YAP laser, of which pulse could penetrate deep in the skin according to its short wavelength. In contrast, CO2 laser stimulation produced only warm sensations and no pricking sensation when applied to the glabrous skin, perhaps due to a thicker stratum corneum and the shallow penetration of the CO2 laser pulse. Regarding intraepidermal electrical stimulation using concentric electrodes, the perceived sensations turned from pinprick to a combination of pinprick and electrical shocks with increasing intensities. Using the concentric planar electrode, the sensations perceived at high stimulation intensity even consisted of electric shocks without concomitant pinprick. In contrast, using the micropatterned electrode, only pinprick sensations were produced by the stimulation of the hairy skin, while the stimulation of the glabrous skin produced no sensation at all within the limits of stimulation intensities used in this study. ConclusionsUsing the CO2 laser or the micropatterned electrode, pinprick sensations were selectively produced by the stimulation of hairy skin, while only warm sensation or no sensation at all were produced by the stimulation of glabrous skin. These two techniques appear to be more selective with a limited diffusion of the stimulation into the skin, restricting the activation of sensory afferents to the most superficial and smallest intraepidermal nerve fibers.

Therapeutic effect of mesenchymal stem cells on histopathological, immunohistochemical, and molecular analysis in second-grade burn model

Background and aimDeleterious cutaneous tissue damages could result from exposure to thermal trauma, which could be ameliorated structurally and functionally through therapy via the most multipotent progenitor bone marrow mesenchymal stem cells (BM-MSCs). This study aimed to induce burns and examine the effect of BM-MSCs during a short and long period of therapy.Material and methodsNinety albino rats were divided into three groups: group I (control); group II (burn model), the animals were exposed to the preheated aluminum bar at 100°C for 15 s; and group III (the burned animals subcutaneously injected with BM-MSCs (2×106 cells/ ml)); they were clinically observed and sacrificed at different short and long time intervals, and skin samples were collected for histopathological and immunohistochemical examination and analysis of different wound healing mediators via quantitative polymerase chain reaction (qPCR).ResultsSubcutaneous injection of BM-MSCs resulted in the decrease of the wound contraction rate; the wound having a pinpoint appearance and regular arrangement of the epidermal layer with thin stratum corneum; decrease in the area percentages of ADAMs10 expression; significant downregulation of transforming growth factor-β (TGF-β), interleukin-6 (IL-6), tumor necrotic factor-α (TNF-α), metalloproteinase-9 (MMP-9), and microRNA-21; and marked upregulation of heat shock protein-90α (HSP-90α) especially in late stages.ConclusionBM-MSCs exhibited a powerful healing property through regulating the mediators of wound healing and restoring the normal skin structures, reducing the scar formation and the wound size.

TRANSMISSION COEFFICIENT OF POWER DENSITY INTO SKIN TISSUE BETWEEN 6 AND 300 GHZ.

The latest electromagnetic safety guidelines define transmitted or epithelial power density as the basic restriction above 6GHz. In this note, we derive an approximation for a conservative transmission coefficient for quasi plane wave incidence as a function of the frequency for the normal component of the Poynting vector with respect to the evaluation plane or tissue surface |Sz inc| and for its modulus ||Sinc||. The maximum transmission coefficient for the normal component of the Poynting vector ${\boldsymbol{T}}_{\mathbf{z}}^{\mathbf{max}}$ is 1 independent of tissue composition and frequency. Approximations of ${\boldsymbol{T}}_{\mathbf{total}}^{\mathbf{max}}$ normalized to ||Sinc|| for thin and thick stratum corneum are provided allowing higher exposures. These approximations allow to conservatively demonstrate compliance with basic restrictions when quasi plane-wave conditions are locally satisfied and enhancement effects of standing waves between source and body can be neglected. The reported results are important to regulators and standardization bodies regarding revisions of compliance requirements and safety guidelines.

Novel therapy of Scabies's disease

Background: Scabies is a common disease that is caused by Sarcoptes scabiei var. hominis. This disease is usually characterized by skin lesions which form straight or winding cuniculus coloured white or grey. These lesions generally located on the thin stratum corneum. It often accompanied by itching sensation at night and quickly spreads in dense environments. Scabies is a skin disease that is endemic in tropical and subtropical climates. In Indonesia, there are 14,798 Islamic boarding schools with a high prevalence of scabies. Treatment using permethrin 5% is felt to be less effective because if it not done simultaneously and massively, recurrence will occur immediately. The scabies disease certainly makes the students frustrated and decreased educational value

16041 Efficacy of a nature-based lip treatment to repair dry damaged lips: Clinical and biophysical assessments

Background: Lip epithelium is characterized by a thin stratum corneum (SC) with incomplete corneocyte formation. Due to the lack of hair follicles and sweat glands, the lubricating effect of sebum is absent. As a result, the lips can easily become dry and chapped. Extremely dry and damaged lips require intensive treatment, which accelerate healing while providing moisturizing benefits. We investigated a nature-based lip treatment containing healing botanicals to improve barrier function, hydration, and overall health of the lips.

Transcutaneous Blood VOC Imaging System (Skin-Gas Cam) with Real-Time Bio-Fluorometric Device on Rounded Skin Surface.

A skin-gas cam that allows continuous imaging of transcutaneous blood volatile organic compounds (VOCs) emanated from human skin was developed. The skin-gas cam is able to reveal the relationship between the local skin conditions and transcutaneous blood VOCs in the field of volatile metabolomics (volatolomics). A ring-type ultraviolet (UV) light-emitting diode was mounted around a camera lens as an excitation light source, which enabled the simultaneous excitation and imaging of fluorescence. A nicotinamide adenine dinucleotide (NAD)-dependent alcohol dehydrogenase (ADH) was used to detect ethanol as a model sample. When gaseous ethanol was applied to an ADH-immobilized mesh that was wetted with an oxidized NAD solution placed in front of the camera, a reduced form of NAD (NADH) was produced through an ADH-mediated reaction. NADH emits fluorescence by UV excitation, and thus, the concentration distribution of ethanol was visualized by measuring the distribution of the fluorescence light intensity from NADH on the ADH-immobilized mesh surface. In this study, a new gas application method that mimicked the release mechanism of transcutaneous gas for quantification of the transcutaneous gas concentration was evaluated. Also, spatiotemporal changes of transcutaneous ethanol for various body parts were measured. As a result, we revealed a relationship between local skin conditions and VOCs that could not be observed previously. In particular, we demonstrated the facile measurement of transdermal gases from around the ear where capillaries are densely distributed below a thin stratum corneum.

Neonatal skin: Handle with care: A case series

The neonatal skin is fragile and should be handled with maximal care. The thin stratum corneum and attenuated rete ridges in neonatal skin makes them vulnerable to physical injury, insensible water loss, thermal instability and infection. The widespread use of Intensive Care Unit facilities for taking specialized care of the neonate brings along with it a better prognosis for survival but has introduced the caveat of many an iatrogenic skin disorder. Most of these iatrogenic disorders are potentially preventable by providing more inclusive rigorous training of neonatal health care providers and observation of utmost vigilance and care.

Characterization of mesenchymal cells beneath cornification of the fetal epithelium and epidermis at the face: an immunohistochemical study using human fetal specimens.

Fetal development of the face involves a specific type of cornification in which keratinocytes provide a mass or plug to fill a cavity. The epithelial-mesenchymal interaction was likely to be different from that in the usual skin. We examined expression of intermediate filaments and other mesenchymal markers beneath cornification in the fetal face. Using sections from 5 mid-term human fetuses at 14–16 weeks, immunohistochemistry was conducted for cytokeratins (CK), vimentin, nestin, glial fibrilary acidic protein, desmin, CD34, CD68 and proliferating cell nuclear antigen (PCNA). Fetal zygomatic skin was composed of a thin stratum corneum and a stratum basale (CK5/6+, CK14+, and CK19+) and, as the intermediate layer, 2–3 layered large keratinocytes with nucleus. The basal layer was lined by mono-layered mesenchymal cells (CD34+ and nestin+). Some of basal cells were PCNA-positive. In the keratinocyte plug at the external ear and nose, most cell nuclei expressed PCNA, CK5/6, CK14, and CK19. Vimentin-positive mesenchymal cells migrated into the plug. The PCNA-positive nucleus as well as mesenchymal cell migration was not seen in the lip margin in spite of the thick keratinocyte layer. The lingual epithelium were characterized by the CK7-positive stratum corneum as well as the thick mesenchymal papilla. CD68-positive macrophages were absent in the epidermis/epithelium. Being different from usual cornification of the skin, loss of a mesenchymal monolayer as well as superficial migration of mesenchymal cells might connect with a specific differentiation of keratinocyte to provide a plug at the fetal nose and ear.

Optical Detection of a Capillary Grid Spatial Pattern in Epithelium by Spatially Resolved Diffuse Reflectance Probe: Monte Carlo Verification

We performed a large scale Monte Carlo verification of possibility of detecting the capillary grid spatial pattern in surface tissues such as mucosal epithelium or epidermis with very thin (optically nonsignificant) stratum corneum by a spatially resolved diffuse reflectance probe. Our results confirm the hypothesis that a spatially resolved, steady-state, diffuse reflectance spectroscopy can potentially identify absorption inhomogeneities located at the depth of 0.5-1.0 of the transport mean free path l <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ' = 1/μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ', which is the range of capillary loops locations within epithelium. The modulation depth depends significantly on an inhomogeneity's absorption, depth of the inhomogeneity, a bulk reduced scattering coefficient, and the size of the defect. The optical clearing technique can be used to lower the scattering in surface tissues and subsequently increase the transport mean free path, which can lead to increase in the sensitivity of the method.

Location‐related differences in structure and function of the stratum corneum with special emphasis on those of the facial skin

Between the two different kinds of the skin covering the body, the glabrous skin is found only on the palmo-plantar surface because of its rather simple function to protect the underlying living tissue with its remarkably thick stratum corneum (SC) from strong external force and friction. Thus, its barrier function is extremely poor. In contrast, the hair-bearing skin covers almost all over the body surface regardless of the presence of long hair or vellus hair. In regard to its SC, many dermatologists and skin scientists think that it is too thin to show any site-specific differences, because the SC is just present as an efficient barrier membrane to protect our body from desiccation as well as against the invasion by external injurious agents. However, there are remarkable regional differences not only in the living skin tissue but also even in such thin SC reflecting the function of each anatomical location. These differences in the SC have been mostly disclosed with the advent of non-invasive biophysical instruments, particularly the one that enables us to measure transepidermal water loss (TEWL), the parameter of the SC barrier function, and the one that evaluates the hydration state of the skin surface, the parameter of the water-holding capacity of the SC that brings about softness and smoothness to the skin surface. These in vivo instrumental measurements of the SC have disclosed the presence of remarkable differences in the functional properties of the SC particularly between the face and other portions of the body. The SC of the facial skin is thinner, being composed of smaller layers of corneocytes than that of the trunk and limbs. It shows unique functional characteristics to provide hydrated skin surface but relatively poor barrier function, which is similar to that observed in retinoid-treated skin or to that of fresh scar or keloidal scars. Moreover, there even exist unexpected, site-dependent differences in the SC of the facial skin such as the forehead, eyelid, cheek, nose and perioral regions, although each location occupies only a small area. Between these locations, the cheek shows the lowest TEWL in contrast to the perioral region that reveals the highest one. Moreover, these features are not static but change with age particularly between children and adults and maybe also between genders. Among various facial locations, the eyelid skin is distinct from others because its SC is associated with poor skin surface lipids and a thin SC cell layer composed of large corneocytes that brings about high surface hydration state but poor barrier function, whereas the vermillion borders of the lips that are covered by an exposed part of the oral mucosa exhibit remarkably poor barrier function and low hydration state. Future studies aiming at the establishment of the functional mapping in each facial region and in other body regions will shed light on more delicate site-dependent differences, which will provide us important information in planning the strategy to start so called tailor-made skin care for each location of the body.

Millimeter wave reflectivity used for measurement of skin hydration with different moisturizers

A new non-invasive method for determining the free water content in human skin has been developed. The method analyzes the reflection of millimeter (mm) wavelength electromagnetic waves. The amount of reflection of mm waves depends on an electrical property (namely, the permittivity) of the skin, and this depends upon the free water content of the various skin layers. The aim of the present study was to use the mm wave reflectometry method for determination of free water content in healthy skin treated with different hydrating substances. Skin lotion, pure water, glycerol, and petroleum jelly (an occlusive substance) were used for hydration of skin. The amount of free water was calculated using the permittivity values of skin layers found from fitting a three layer skin model to measured reflection data. The skin model consisted of (1) the stratum corneum (SC), (2) the viable epidermis plus the dermis, and (3) fat layers. Mm wave reflection was significantly affected by the water content of the thick SC of the palm but not by the very thin SC of the forearm. Treatment of the forearm and palm skin with different hydrating substances produced notable changes of the free water content in the SC, but not in the viable epidermis or dermis. The greatest hydration was produced by pure water and skin lotion, and the lowest by petroleum jelly. However, petroleum jelly produced prolonged retention of water in the SC following its hydration by other moisturizers. The content of free water was found to return to its baseline value after removal of moisturizers in as short a time as 8.3 min. The study shows that mm wave reflectometry can be used as a sensitive technique for the non-invasive determination of water content in living skin.

Sanitary napkin contact dermatitis of the vulva: Location‐dependent differences in skin surface conditions may play a role in negative patch test results

I herein report six Japanese female patients with sanitary napkin contact dermatitis of the vulva. This condition may not be uncommon, although only a few reports have been published in Europe and the USA and none from Asia. Routine patch test with a saline-soaked fragment of their sanitary napkins conducted on the flexor surface of the upper arm gave negative results in all the patients, although pruritic dermatitis was clinically reproducible, developing in a delayed fashion, 2-4 days after the use of any brands of sanitary napkin. Moreover, this dermatitis could be avoided by using a tampon together with wearing cotton shorts. These observations suggest that it is a kind of irritant dermatitis that is induced by the wet local conditions as well as by friction caused by wearing a sanitary napkin rather than that due to sanitary napkin components. Resistance of the skin against external irritant stimuli is variable among different body sites and the genital skin, which is covered by thin stratum corneum, is thought to have low resistance against various external irritating and mechanical stimuli induced by wearing a sanitary napkin. Moreover, it is reasonable to presume that the proliferation of the resident microorganisms of the genital skin that takes place under the wet conditions produced by the use of the napkin also plays a role in the induction of such a unique contact dermatitis. Unfortunately, the commonly employed patch testing method performed on the skin of the upper limb or back cannot simulate the local situation occurring on the vulva under the sanitary napkin. We are urgently in need of a modification in patch testing method that is suited to reproduce similar dermatitis in other body locations.

Skin biothermomechanics for medical treatments

Electromagnetic heating, such as microwave, radiofrequency, and laser etc., is widely used in medical treatments. Recent advances in these technologies resulted in remarkable developments of thermal treatments for a multitude of diseases and injuries involving skin tissue. The comprehension of heat transfer and related thermomechanics in skin tissue during these treatments is thus of great importance, and can contribute to the further developments of these medical applications. Biothermomechanics of skin is highly interdisciplinary, involving bioheat transfer, burn damage, biomechanics, and physiology. The aim of this study is to develop a computational approach to examine the heat transfer process, heat-induced mechanical response, as well as the associated pain level, so that the differences among the clinically applied heating modalities can be quantified. In this paper, numerical simulation with the finite difference method (FDM) was used to analyze the temperature, burn damage, and thermal stress distributions in the skin tissue subjected to various thermal treatments. The results showed that the thermomechanical behavior of skin tissue is very complex: blood perfusion has little effect on thermal damage, but a large influence on skin temperature distribution, which, in turn, influences significantly the resulting thermal stress field; for laser heating, the peak temperature is higher for lasers with shorter wavelengths, but the peak is closer to the skin surface; the thermal stress due to laser and microwave heating is mainly limited to the top epidermis layer due to the exponential decrease of heat generation along skin depth; the thin (and commonly overlooked) stratum corneum layer dominates the thermomechanical response of skin tissue.

Millimeter wave dosimetry of human skin

To identify the mechanisms of biological effects of mm waves it is important to develop accurate methods for evaluating absorption and penetration depth of mm waves in the epidermis and dermis. The main characteristics of mm wave skin dosimetry were calculated using a homogeneous unilayer model and two multilayer models of skin. These characteristics included reflection, power density (PD), penetration depth (delta), and specific absorption rate (SAR). The parameters of the models were found from fitting the models to the experimental data obtained from measurements of mm wave reflection from human skin. The forearm and palm data were used to model the skin with thin and thick stratum corneum (SC), respectively. The thin SC produced little influence on the interaction of mm waves with skin. On the contrary, the thick SC in the palm played the role of a matching layer and significantly reduced reflection. In addition, the palmar skin manifested a broad peak in reflection within the 83-277 GHz range. The viable epidermis plus dermis, containing a large amount of free water, greatly attenuated mm wave energy. Therefore, the deeper fat layer had little effect on the PD and SAR profiles. We observed the appearance of a moderate SAR peak in the therapeutic frequency range (42-62 GHz) within the skin at a depth of 0.3-0.4 mm. Millimeter waves penetrate into the human skin deep enough (delta = 0.65 mm at 42 GHz) to affect most skin structures located in the epidermis and dermis.

Water relations of tetrapod integument

The vertebrate integument represents an evolutionary compromise between the needs for mechanical protection and those of sensing the environment and regulating the exchange of materials and energy. Fibrous keratins evolved as a means of strengthening the integument while simultaneously providing a structural support for lipids, which comprise the principal barrier to cutaneous water efflux in terrestrial taxa. Whereas lipids are of fundamental importance to water barriers, the efficacy of these barriers depends in many cases on structural features that enhance or maintain the integrity of function. Amphibians are exceptional among tetrapods in having very little keratin and a thin stratum corneum. Thus, effective lipid barriers that are present in some specialized anurans living in xeric habitats are external to the epidermis, whereas lipid barriers of amniotes exist as a lipid-keratin complex within the stratum corneum. Amphibians prevent desiccation of the epidermis and underlying tissues either by evaporating water from a superficial aqueous film, which must be replenished, or by shielding the stratum corneum with superficial lipids. Water barrier function in vertebrates generally appears to be relatively fixed, although various species have ;plasticity' to adjust the barrier effectiveness facultatively. While it is clear that both phenotypic plasticity and genetic adaptation can account for covariation between environment and skin resistance to water efflux, studies of the relative importance of these two phenomena are few. Fundamental mechanisms for adjusting the skin water barrier include changes in barrier thickness, composition and physicochemical properties of cutaneous lipids, and/or geometry of the barrier within the epidermis. While cutaneous lipids have been studied extensively in the contexts of disease and cosmetics, relatively little is known about the processes of permeability barrier ontogenesis related to adaptation and environment. Advances in such knowledge have didactic significance for understanding vertebrate evolution as well as practical application to clinical dermatology.

Development and Fine Structure of the Reticulate Scales of the Turkey Foetuses with Regard to Occurrence of the Food Pad Lesions in Turkey Poults

Introduction: Most of the morphological studies on the skin of birds refer to chickens. Little can be found about the specific fine structure of the foot‐pad epidermis of turkeys and almost nothing is known about the developing reticulate scales in turkey foetuses. This study deals with the question as to whether the development and morphology of the reticulate scales of turkeys are similar to those of chickens. Since the first signs of food‐pad dermatitis can be observed in turkey poults at the age of four days, it was additionally examined if these alterations can be found in turkey foetuses already.Methods: Foot pad samples of heavy strain BUT Big 6 turkeys were collected at different developmental stages (day 20, 23, and 28 of incubation). The specimens were compared by light‐ and electron‐microscopic methods.Results: On the 20th day of incubation, the reticulate scales cover the food pads as small knob‐like structures. Between the embryonic epidermal cells wide inter‐cellular spaces are visible, and in the intermediate cells multigranular bodies (MGBs) are detectable. Peridermal cells cover the reticulate scales. They are characterized by peridermal granules and protuberances of the outer cell membrane. On the 23rd day of incubation, many lipid droplets are scattered within the intermediate cells. Because a thin stratum corneum has formed, the periderm is almost completely sloughing off. On the 28th day of incubation, the turkey poults hatch. The epidermis has almost reached maturity and a broad stratum corneum is detectable.Conclusions: The development and morphology of the reticulate scale epidermis of turkey is comparable to that of chicken, although little differences were found. Besides former investigations, which described the peridermal protuberances as microvilli, scanning‐electron microscopy proved that they also show a fingerprint‐like surface structure that has not been observed for birds previously. Up to the hatching day, no signs of food pad alterations are seen in developing turkeys.