Specific distribution of barrier-relevant ceramides in the emerging epidermis and the periderm/subperiderm during chicken embryogenesis

During mammalian embryogenesis the emerging epidermis is temporarily covered by an epithelial monolayer, the periderm. In chicken, a second epithelial layer, the subperiderm, located underneath the periderm develops in later embryogenesis. Together the periderm and the subperiderm are referred to as the PSP unit. The cells of the PSP unit are tightly connected by tight junctions (TJ), thereby providing the embryo with an impermeable bilayered diffusion barrier. The emerging epidermis assumes its barrier function by cornification beginning at embryonic day 17 (E17) before at E18 the PSP unit undergoes desquamation. Lipid analysis of both epithelia after their mechanical separation revealed a dramatic increase to about 100-fold values of barrier-relevant ceramides, i.e. those known to essentially contribute to the diffusion barrier of the cornified envelope, in the emerging epidermis between E17 and E19. In contrast, the content of barrier-relevant ceramides in the PSP unit remained at constantly low levels throughout embryogenesis. These data strongly argue in favour of different mechanisms for the barrier function of the two epithelia. TJ in the PSP unit provide the main diffusion barrier protecting the embryo until beginning of desquamation at E18. At this developmental stage the content of cornified envelope-specific ceramides is substantially elevated, thus enabling the epidermis to fulfil its function as the major diffusion barrier after desquamation of the PSP unit. The observation that barrier-relevant ceramides are formed prior to desquamation of the PSP unit points to a precisely regulated sequence in that desquamation does not occur until the lipid-based barrier of the cornified envelope is completed and suggests in addition that these lipids might be essential regulators of the interaction between the PSP unit and the emerging epidermis.     

In vitro induction of cell division in the epidermis of stem segments ofTorenia fournieri Lind.

Cell division in the epidermis of stem segments ofT. fournieri stopped immediately when the epidermis was separated from subjacent tissues after having been in contact with these tissues for some time. Thus, the effects of the inductive signals emanating from these tissues did not persist. However, cell division in isolated epidermis cultured alone could be induced by adding asparagine, alanine or glutamine to the medium. Asparagine, at 5 mM, had the greatest stimulatory effect. Growth substances had a synergistic effect on this induction by amino compounds. However, these cell divisions, unlike those in epidermis cultured together with subepidermal tissues, did not lead to organogenesis. The amino compounds which partially replaced the inductive action of subepidermal layers on the epidermis can be considered as one of the endogenous factors coming from the first-named layers in intact explants.     

A study on the vascularization and structure of the epidermis of the air-breathing mudskipper, Periophthalmus magnuspinnatus (Gobiidae, Teleostei), along different parts of the body

A histological study on the epidermis of eight body regions, five fins and the sucking disc was performed on the mudskipper, Periophthalmus magnuspinnatus. The study aimed to determine the role of the skin in respiration and to assess which region of the skin was most effective. The structure of the epidermis, consisting of the superficial layer, middle layer and the stratum germinativum, was the same in all regions. Large numbers of blood capillaries were situated at the superficial layer and occasionally at the middle layer. The mean diffusion distance between the capillary endothelial cells and the surface of the epidermis ranged from 2.6 to 15.4 μm: the lowest value was on the back (mean 2.0 μm) and the highest value was at the base of the anal fin (mean 15.4 μm). Relative surface area of respiratory epithelium in 14 regions was highest in the 1st and 2nd dorsal fins with a thinner epidermis and a lower diffusion distance (mean value 3.2% and 2.5% respectively), whereas the lowest was found at the base of the anal fin (mean 0.7%). Among the 14 regions of the epidermis, it can be surmised that the two dorsal fins toward the upper region may often be more exposed to air and for longer time periods than the other body regions during the amphibious life phase of Periophthalmus magnuspinnatus.     

The penetration of 3:5-dinitro-o-cresol into leaves

A study of the penetration of 3:5-dinitro- 0 -cresol from spray solutions or suspensions into leaves of Sinapis arvensis L. shows that entry through the stomata is unimportant. Lethal amounts may enter from aqueous solution by simple diffusion of the undissociated phenol through the epidermis, which behaves as a homogeneous lipide membrane. The effect of the structure of the epidermal surface on the rate of diffusion is discussed. Lethal amounts may also enter Sinapis from a dry surface deposit by gaseous diffusion through the stomata or by diffusive penetration of the epidermis following sublimation. Movement of the substance within a plant is slight and appears to be mainly by diffusion. The selective action of 3:5-dinitro- 0 -cresol as a weed-killer is discussed in the light of these results.     

The Rate of Water-loss from Stripped Leaves

Stripping off the epidermis of Sedum leaves is found to increasethe rate of water-loss by amounts of the order of 700 per cent.A high resistance of the pores of the stomatal epidermis tothe diffusion of water-vapour from the mesophyll is thus indicated. Stripping one surface of a leaf considerably increases the rateof transpiration from the other (untouched) surface. The explanationof this is under investigation. In conclusion, the writer wishes to thank Dr. F. M. Haines forsuggestions, interest and criticism. Thanks are also due tothe staff of the Chelsea Physic Garden and to Mr. I. R. McGregorfor his valuable technical assistance.     

Structure of the skin of an air-breathing mudskipper, Periophthalmus magnuspinnatus

The epidermis of the mudskipper Periophthalmus magnuspinnatus consisted of three layers: the outermost layer, middle layer and stratum germinativum. Extensive vascular capillary networks were present near the superficial layer of epidermis and outermost layer. The diffusion distance between the vascular capillaries and the surface of epidermis was c . 1.5 ± 0.9μm. The middle layer consisted of small or voluminous cells swollen by epidermal cells. Due to the swollen cells, the thickness of the epidermis increased and the epidermis appeared web-like. The swollen cells contained tonofilaments, lucent contents and desmosomes. Fine blood capillaries were also discernible in this layer. Well-developed lymphatic spaces containing lymphocytes existed in the stratum germinativum. Numerous blood capillaries were present under the basement membrane. The dermis consisted of a stratum laxum and stratum compactum, and there was a definite area with acid mucopolysaccharides and a small scale in the stratum laxum. The skin had an epidermal pigment cell, dendritic melanophores (-cytes) containing melanin granules within their cytoplasm, and two kinds of dermal pigment cells, melanophores and colourless pigments containing reflecting platelets.     

Morphology of the Epidermis of the Neotropical Catfish Pimelodella lateristriga (Lichtenstein, 1823) with Emphasis in Club Cells

The epidermis of Ostariophysi fish is composed of 4 main cell types: epidermal cells (or filament containing cells), mucous cells, granular cells and club cells. The morphological analysis of the epidermis of the catfish Pimelodella lateristriga revealed the presence of only two types of cells: epidermal and club cells. The latter were evident in the middle layer of the epidermis, being the largest cells within the epithelium. Few organelles were located in the perinuclear region, while the rest of the cytoplasm was filled with a non-vesicular fibrillar substance. Club cells contained two irregular nuclei with evident nucleoli and high compacted peripheral chromatin. Histochemical analysis detected prevalence of protein within the cytoplasm other than carbohydrates, which were absent. These characteristics are similar to those described to most Ostariophysi studied so far. On the other hand, the epidermal cells differ from what is found in the literature. The present study described three distinct types, as follows: superficial, abundant and dense cells. Differences among them were restricted to their cytoplasm and nucleus morphology. Mucous cells were found in all Ostariophysi studied so far, although they were absent in P. lateristriga, along with granular cells, also typical of other catfish epidermis. The preset study corroborates the observations on club cells'' morphology in Siluriformes specimens, and shows important differences in epidermis composition and cell structure of P. lateristriga regarding the literature data.     

Der Diffusionswiderstand der Spaltöffnungen; ein Vergleich des CO2-Gaswechsels von Blättern mit und ohne Epidermis

Summary The lower epidermis from leaves of Primula palinuri can be stripped off. Light-saturation curves of the CO₂-exchange were measured at 20°C and 300 ppm CO₂. Whereas the normal leaf reaches light-saturation at 0.3 cal cm^-2 min^-1, even 0.6 cal cm^-2 min^-1 is not sufficient to saturate the stripped leaf. Transpiration, apparent CO₂-uptake and leaf-temperature were measured simultaneously. The data were used to calculate the diffusion resistances for CO₂ with the usual methods, that is, from the diffusion resistances for water-vapour transport. The comparison of the CO₂-exchange of stripped and normal leaves makes it possible to determine the resistances—in particular those of the stomata—directly from the CO₂-exchange. Both methods agree well. When CO₂ exchanges only through the lower surface of the leaf the epidermis is—even with opened stomata—a considerable diffusion resistance. It lowers the CO₂-concentration in the intercellular system to 160 ppm and limits the CO₂-uptake.     

Field Studies of the Wheat Stomata Resistance Influenced by Soil Water Content

Concurrent observations of soil water potential and leaf stomata diffusion resistance were made on two, plots of wheat grown at Datun Agro-ecological Experimental Station in Beijing under two different soil water conditions. These data were further complemented by weather and physiological observation. In this paper, we mainly analysed the influence of soil water potential on the status of wheat leaf stomatal resistance. The results indicate that: (1) there is a obvious influence of soil water potential on the status of wheat leaf stomata under normal conditions and (2) there is a different upper and lower epidermis stomata of wheat leaf respond to the soil water potential. The lower epidermis stomata are more sensitive to soil water potential than upper epidermis one. (3) There is a linear relationship between the ratio of lower and upper epidermis stomata resistance and soil water potential in root layer, according to this we can diagnose the degree of wheat water deficit.     

The effect of resveratrol and its methylthio-derivatives on the Nrf2-ARE pathway in mouse epidermis and HaCaT keratinocytes

Resveratrol is the most extensively studied stilbene derivative. We previously showed that methylthiostilbenes were more effective inhibitors of CYP1A1 and 1B1 activity than resveratrol. In this study, we investigated whether resveratrol and its methylthio-substituted derivatives, i.e. 3-M-4′-MTS (S2), 3,5-DM-4′-MTS (S5) and 3,4,5-TM-4′-MTS (S7) could activate Nrf2 signaling in the mouse epidermis and in human keratinocytes. Western blot analysis showed translocation of Nrf2 from the cytosol to the nucleus in both models. All of the tested stilbenes increased GST activity, but resveratrol was the most effective inducer. Moreover, only resveratrol increased the protein level of GSTP in the mouse epidermis. GSTM was enhanced in HaCaT cells after the treatment with derivatives S2 and S5. The same effect was observed for GSTP in the case of compound S2. Resveratrol and its derivatives reduced the NQO2 protein level in HaCaT cells. Thus, it is possible that increased expression of GSTP or GSTM and GST activity was linked with NQO2 inhibition in these cells. The results of this study indicate that resveratrol and its methylthioderivatives activate Nrf2 not only in the mouse epidermis, but also in human keratinocytes. Upregulating GST isozymes might be particularly important for deactivating chemical carcinogens, such as PAH.     

Coupled Protein Diffusion and Folding in the Cell

When a protein unfolds in the cell, its diffusion coefficient is affected by its increased hydrodynamic radius and by interactions of exposed hydrophobic residues with the cytoplasmic matrix, including chaperones. We characterize protein diffusion by photobleaching whole cells at a single point, and imaging the concentration change of fluorescent-labeled protein throughout the cell as a function of time. As a folded reference protein we use green fluorescent protein. The resulting region-dependent anomalous diffusion is well characterized by 2-D or 3-D diffusion equations coupled to a clustering algorithm that accounts for position-dependent diffusion. Then we study diffusion of a destabilized mutant of the enzyme phosphoglycerate kinase (PGK) and of its stable control inside the cell. Unlike the green fluorescent protein control''s diffusion coefficient, PGK''s diffusion coefficient is a non-monotonic function of temperature, signaling ‘sticking’ of the protein in the cytosol as it begins to unfold. The temperature-dependent increase and subsequent decrease of the PGK diffusion coefficient in the cytosol is greater than a simple size-scaling model suggests. Chaperone binding of the unfolding protein inside the cell is one plausible candidate for even slower diffusion of PGK, and we test the plausibility of this hypothesis experimentally, although we do not rule out other candidates.     

A complex sensory organ in the nose skin of the prosimian primate Lemur catta

Most mammals have nose tips covered by glabrous skin, a labronasal area, or rhinarium. The surface of the rhinarium of Lemur catta has a dermatoglyphic pattern consisting of epidermal domes. Below the domes, epidermal pegs dip down into the dermis. In and below the tip of the epidermal peg, a complex sensory organ is found. It consists of an association of innervated Merkel cells, lamellate (Pacini‐like) bodies with a central nerve, and a ring of unmyelinated nerve endings in the epidermis. The Merkel cells are situated basally in the epidermis and the lamellated bodies just below the epidermis. The unmyelinated nerve endings related to the organ ascend in a circle straight through the epidermis ending below the corneal layer. From these nerve terminals, horizontal spikes enter the keratinocytes. The three components occur together forming an organ and are innervated from a common nerve plexus. The morphology of the complex sensory organ of the lemur shares most crucial components with Eimer's organs in moles, echidna, and platypus, while some structures are lacking, for example, the specific central pillar of keratinocytes, the cuticular cap, and a central unmyelinated fiber. The presence of the essentials of an Eimer's organ in many mammals suggests that a wider definition is motivated. J. Morphol. 276:649–656, 2015. © 2015 Wiley Periodicals, Inc.     

Rates of diffusion of fluorescent molecules via cell-to-cell membrane channels in a developing tissue

Diffusion coefficients for the intercellular movement of fluorescent tracers have been measured in the epidermis of a larval beetle. Fluorescent tracer was injected into a cell and the spread of tracer from cell to cell in this monolayer was recorded by a TV camera. Fluorescence intensities were digitized from the TV images at successive times after the start of injection at various distances from the source by a microcomputer interfaced with a video analyzer. From the relationship between concentration (measured as light intensity), time and distance, an effective diffusion coefficient (De) is calculated for the tracer in the tissue. In newly ecdysed epidermis, De for carboxyfluorescein (CF) is 2.7 X 10(-7) cm2/s, and De for lissamine rhodamine B (LRB) is 1.2 X 10(-7) cm2/s, whereas in intermolt epidermis the De's for CF and LRB are 3.7 X 10(-7) and 1.2 X 10(-7) cm2/s, respectively. These diffusion coefficients are only an order of magnitude lower than their values in water. The ratio of De for the two tracers at these two stages of development differs from the ratio predicted in cytoplasm alone, with the movement of the slightly larger molecule (LRB) being impeded relative to that of the smaller molecule (CF). This suggests that the properties of the membrane channels amplify differences in the rates of movement of molecules of similar size. This may be important during cell patterning in development. De for CF was also monitored as junctional resistance was increased in the epidermis. During 30 min of exposure to 0.25 mM chlorpromazine, De dropped to 20% of its initial value of 5 X 10(-7) cm2/s, implying that the junctional membrane, rather than cytoplasm, is the major barrier to molecular diffusion among the cells.     

Glandular Epithelium as a Possible Source of a Fertility Signal in Ectatomma tuberculatum (Hymenoptera: Formicidae) Queens

The wax layer covering the insect''s cuticle plays an important protective role, as for example, uncontrolled water loss. In social insects, wax production is well-known in some bees that use it for nest building. Curiously, mated-fertile queens of the ant Ectatomma tuberculatum produce an uncommon extra-wax coat and, consequently queens (mated-fertile females) are matte due to such extra cuticular hydrocarbon (CHC) coat that covers the cuticle and masks the brightness of the queens'' cuticle while gynes (virgin-infertile queens) are shiny. In this study, histological analysis showed differences in the epidermis between fertile (i.e., queens or gynes with highly ovarian activity) and infertile females (gynes or workers with non developed ovaries). In fertile females the epidermis is a single layer of cubic cells found in all body segments whereas in infertile females it is a thin layer of flattened cells. Ultrastructural features showed active secretory tissue from fertile females similar to the glandular epithelium of wax-producing bees (type I gland). Different hypotheses related to the functions of the glandular epithelium exclusive to the E. tuberculatum fertile queens are discussed.     

Study of skin microcirculation by epicutaneous diffusion of 133 xenon]

The diffusion of radioactive inert gas xenon 133 through the epidermis in man was studied by compartimental model with a constant speed injection. From this we deduce the cutaneous and subcutaneous flow.     

Transdermal insulin delivery using lipid enhanced electroporation

Transdermal insulin transport by electroporation was measured using porcine epidermis and fluorescein-labeled insulin. Previous studies have shown that anionic lipids can enhance the electroporative transport of molecules up to 10 kDa in size. It was also shown that it is the charge and not the type of the phospholipid head group that influences transdermal transport under electroporation. Moreover, phospholipids with saturated acyl chains enhance the transport of larger molecules more as compared to those with unsaturated chains. In the current study, based on those earlier findings, the effect of 1,2-dimyristoyl-3-phosphatidylserine (DMPS) on the transdermal transport of insulin by electroporation was examined. Porcine epidermis was used as a model for skin. Transport was measured using glass vertical diffusion apparatus in which the epidermis separated the donor and receiver compartments. Negative pulses were applied across the epidermis using platinum electrodes. Results show that when electroporation was carried out in the presence of DMPS, there was greater than 20-fold enhancement of insulin transport. Furthermore, while in the presence of the phospholipid, almost all the transported insulin was detected in the receiver compartment; in the absence of added lipids, only about half the insulin transported was in the receiver compartment and an almost equal amount of insulin remained in the epidermis. Fluorescence microscopy revealed that the insulin transport was mainly through the lipid multilayer regions that surround the corneocytes.     

Transdermal insulin delivery using lipid enhanced electroporation

Transdermal insulin transport by electroporation was measured using porcine epidermis and fluorescein-labeled insulin. Previous studies have shown that anionic lipids can enhance the electroporative transport of molecules up to 10 kDa in size. It was also shown that it is the charge and not the type of the phospholipid head group that influences transdermal transport under electroporation. Moreover, phospholipids with saturated acyl chains enhance the transport of larger molecules more as compared to those with unsaturated chains. In the current study, based on those earlier findings, the effect of 1,2-dimyristoyl-3-phosphatidylserine (DMPS) on the transdermal transport of insulin by electroporation was examined. Porcine epidermis was used as a model for skin. Transport was measured using glass vertical diffusion apparatus in which the epidermis separated the donor and receiver compartments. Negative pulses were applied across the epidermis using platinum electrodes. Results show that when electroporation was carried out in the presence of DMPS, there was greater than 20-fold enhancement of insulin transport. Furthermore, while in the presence of the phospholipid, almost all the transported insulin was detected in the receiver compartment; in the absence of added lipids, only about half the insulin transported was in the receiver compartment and an almost equal amount of insulin remained in the epidermis. Fluorescence microscopy revealed that the insulin transport was mainly through the lipid multilayer regions that surround the corneocytes.     

Electrical properties of the horny layer of human epidermis and its water transport

Experimental evidence was obtained concerning the connection between the electric parameters of epidermis horny layer of the man's skin and water transport in the course of imperceptible perspiration. Two-layer diffusion model of water transport was considered.     

Potassium reaccumulation by isolated frog epidermis

The involvement of potassium in transepithelial sodium transport was tested by studying net potassium reuptake by potassium-depleted frog skin epidermis. Normal potassium content in half-strength Ringer's (0.244 μequiv/mg dry weight) fell 43% after 16 h in K-free medium at 5°C. Reaccumulation, against an electrochemical potential gradient, to 83% of the initial tissue potassium content occurred following incubation for 4 h at 22°C in K-containing medium. Sodium was required in the solution bathing the inside, but not the outside surface of the skin, for net potassium reaccumulation. Ouabain caused an additional potassium loss from potassium-depleted epidermis, but did not have the same effect on potassium-depleted isolatedcells. Procaine, lithium and caffeine completely inhibited, antidiuretic hormone and cyclic AMP may partially inhibit and amiloride had no effect on potassium reaccumulation. In many cases decreases in sodium and water content were found to occur even in the absence of net potassium reaccumulation. The results suggest (1) potassium is actively transported into the epidermis, (2) this transport is not rigidly coupled to sodium extrusion or water loss, (3) potassium uptake is not rigidly coupled to transepithelial sodium transport, or only a small fraction is involved, (4) potassium diffusion is restricted in the extracellular space.     

Characterization of the keratin filament subunits unique to bovine snout epidermis.

Steinert [Biochem. J. (1975) 149, 39-48] reported that the alpha-keratin polypeptides (the subunits of the intracellular keratin filaments) of bovine hoof and snout epidermis are the same. We now demonstrate that this is not so: in addition to the seven polypeptides previously identified in hoof epidermis, snout epidermis also contains at least three other polypeptides of higher molecular weight. These unique polypeptides were isolated, purified and characterized. They are chemically and structurally very similar to the other polypeptides of bovine epidermis and readily polymerize in vitro with them to form native-type epidermal keratin filaments.