Changes in structure of ventral epidermis of Rana ridibunda during metamorphosis

Summary The organisation of the ventral epidermis organisation was followed throughout ontogenesis in Rana ridibunda. Epidermis of tadpoles with 2–3 limbs was organised into two layers: a stratum germinativum consisting of elongated columnar cells, and an outer stratum corneum consisting of two types of cuboid cells. Two types of cells can be distinguished; they are a light (clear) cell and a dark (dense) cell. In the 4-legged tadpoles the stratum corneum cells start to flatten and a replacement layer appeared underneath. A well-defined stratum germinativum is found and within it, epidermal glands. Moulting took place for the first time in tadpoles just before metamorphosis, and a well-organised stratum granulosum was formed still containing the two main types of epidermal glands. The flask cells appear in the juveniles for the first time, greatly increasing in numbers in the adult epidermis.     

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.     

Fibronectin (FN) localizations in mitochondria-rich cells of frog epidermis

Indirect immunoperoxidase detection of fibronectin (FN) in the ventral frog epidermis showed that only one type of epidermal cell, the mitochondria-rich cells (MRC), was FN-detected. FN was found in MRC having rounded, flask-like and intermediate shapes, located at different levels of the epidermis between the stratum germinativum and the stratum corneum. These cells contained cytoplasmic FN particularly in the form of small granules. Our results support the view that MRC differ from other epidermal cells in their in vivo FN localizations.     

Skin cultured with or without an NaCl gradient and aldosterone influence epidermal fibronectin localizations

Fibronectin (FN) localizations in the epidermal cells of the frog Rana esculenta were detected in isolated ventral skin fragments 4 day-cultured with or without an NaCl transepithelial gradient and aldosterone. Without the gradient, few mitochondria-rich cells (MRCs) were FN-detected. Stratum germinativum and spinosum cells also contained fibronectin. With the gradient, numerous MRCs were detected. Below them, in the stratum germinativum, clear spaces were recognized. Aldosterone with or without the gradient modified the above effects: in both cases, many MRC contained fibronectin. It was interesting to note that, for each type of culture, stratum germinativum cells were dramatically FN-detected.     

Anti-fibronectin serum inhibits the disorganization of the dermal-epidermal junction in cultured wounded skin

During wound-healing in cultured frog skin fragments, fibronectin (FN) was detected in the dermal-epidermal junction. Intracellular fibronectin was stained using permeabilization and DAB immunoperoxidase. With electron microscopy intracytoplasmic FN granules were localized in the epidermal processes of the stratum germinativum cells protruding towards the dermis and in their marginal regions (membrane-associated plaques). Faint staining was visible at the level of the lamina densa and inside some parts of the lamina lucida. In comparison, contrasted ultrathin sections revealed classical disorganization of the dermal-epidermal junction. In the presence of anti-fibronectin serum during the whole time of culture, fibronectin-antifibronectin binding was visualized in the form of sparse cytoplasmic granules in the epidermal processes of the stratum germinativum cells. Contrasted ultrathin sections emphasized the continuity between the tonofilaments, the anchoring filaments and the anchoring fibrils. Briefly, anti-fibronectin serum inhibits the disorganization of the dermal-epidermal junction in cultured wounded skin.     

Orientation behaviour of toads (Bufo bufo) displaced from the breeding site

Summary The sensory basis and spatial range of orientation to the breeding site were studied in the toadBufo bufo, during two breeding seasons. Toads were displaced passively from their breeding pond and fitted with a tracking device to record the path of migration in individuals. The directional choice and the straightness of trails after release were used to quantify the effect of experimental treatments. In both years, control (untreated): toads headed to the breeding site with the same precision at all release sites. The initial orientation of toads blinded by opaque tape over their eyes. did not differ from controls, but the return paths were not as direct. The directional choice of anosmic toads was apparently random, however, individuals followed a straight path in a chosen direction. Anosmic toads also blinded were completely disoriented, moving in cycloid trails. Bar magnets glued to the head caused an increase in dispersion of toads. However, in some individual releases a directional bias without increased dispersion was observed. Sky conditions (clear or overcast) did not influence the initial orientation or the dispersion of toads. Nevertheless, the breeding site component was significantly correlated with wind direction in relation to the breeding site. Wind blowing from the breeding site improved the initial orientation, whereas wind from the opposite direction reduced the breeding site component. The spatial range for the ability to relocate the breeding pond after displacement exceeded 3 km, but the time taken to select the correct direction increased with the displacement distance. The results indicate that after displacement the initial orientation ofB. bufo is based mainly on olfactory and magnetic cues, with visual control of straightness.     

Characterization of metamorphic changes in anuran larval epidermis using lectins as probes

The skin of an adult frog of Xenopus laevis was characterized by the reactivity of 20 lectins. The lectins were classified into six groups in their binding to the epidermal cells: Lycopersicon esculentum lectin (LEL)-type which was positive for all epidermal cells; Pisum sativum agglutinin (PSA)-type for stratum germinativum; succinylated wheat germ agglutinin (sWGA)-type for strata spinosum, granulosum and corneum; Dolichos biflorus agglutinin (DBA)-type for strata germinativum and spinosum; peanut agglutinin (PNA)-type for stratum spinosum; and Ulex europaeus agglutinin (UEA-I)-type for strata granulosum and corneum. PSA and sWGA were utilized as markers of mitotically active germinative cells and the differentiated cells of the epidermis, respectively, to describe the metamorphic conversion of larval epidermal cells to adult type. PSA stained all epidermal cells of tadpoles before metamorphic climax. At the end of metamorphosis, PSA-positive cells were restricted to cells in the basal layer of body epidermis while all the tail epidermis remained PSA-positive. The other cell marker, sWGA, only stained apical cells in tadpole epidermis. During the metamorphic climax, sWGA-positive cells appeared in the cells beneath the stratum corneum of the body region, but not in the tail region. The present study demonstrates that PSA and sWGA are useful to investigate metamorphic changes in tadpole epidermal cells.     

Epidermal tissue homeostasis. II. Cell pool size, cell birth rate and cell loss in toads deprived of the pars distalis of the pituitary gland

Following removal of the pars distalis of the pituitary gland in toads, epidermal efflux from the stratum corneum recruitment cell pool (i.e. production of corneal layers) is greatly increased. In this investigation the cell birth rate is studied by means of the metaphase arrest technique, as a function of time after pars distalis ablation. The method allows assessment of the total cell production over 14 days after the operation, to be compared with the total efflux and changes in the epidermal cell pool size. Whereas in intact toads the rate of cell production exceeds that of cell loss by moulting by a factor of 2.7, the 'surplus' of cells neither being used for formation of corneal layers nor permanently accommodated within the living epidermis, a 'balance sheet' of efflux and influx indicates that following pars distalis ablation all cells produced are also used for the (excessive) formation of corneal cell layers. The observations lend further support to the hypothesis that controlled cell deletion is a tissue homeostatic mechanism complementary to controlled cell divisions.     

The gastric mucosa of two monotremes: the duck-billed platypus and echidna

The gastric mucosa of both the echidna and platypus is aglandular and the lining epithelium is stratified squamous. The latter exhibits three principle layers: stratum germinativum, stratum spinosum, and stratum corneum. The cytoplasm of cells composing the first two strata of both species shows bundles of tonofibrils and numerous free ribosomes. Cells of the stratum spinosum in the platypus also show numerous dense granules limited to the peripheral cytoplasm. The stratum spinosum of both species is comprised of fusiform-shaped cells whose adjacent cell membranes show extensive interlocking. The stratum spinosum of the echidna in addition shows numerous intercellular bridges. Cells of the stratum corneum become flattened and elongate and in the echidna nuclei near the surface appear to degenerate. Cells comprising the stratum corneum of the platypus exhibit well preserved nuclei and contain scattered large granules of varying electron density. Prior to sloughing, cells near the surface of both species show a separation of adjacent cell membranes. True keratinization is not found in the gastric lining epithelium of either species and the epithelium lining of the stomach of the echidna more closely represents a form of parakeratosis. Delicate papillae containing capillaries extend considerable distances into the overlying epithelium of both species and are thought to contribute to its nutrition.     

A comparative study on vascularization and the structure of the epidermis of an amphibious mudskipper fish,Scartelaos gigas (Gobiidae,Teleostei), on different parts of the body and the appendages

Epidermal structure of the amphibious mudskipper, Scartelaos gigas (Gobiidae), was investigated in relation to their terrestrial adaptation whereby a histological study on the epidermis of 15 regions including nine body regions, five fins and the sucking disc was carried out. The structure of the epidermis consists of three layers: an outermost layer with polygonal cells or rather flattened cells, small cells and mucous cells; a thick middle layer with voluminous cells swollen by epidermal cells; and the stratum germinativum. A dermal bulge was located at each apical area of the epidermis of almost all body regions, but was not existent in the operculum and the appendages, including none of the fins or the sucking disc. In the epidermis of the body regions, the dermal bulges had numerous dermal capillaries just beneath the stratum germinativum. By contrast, the appendages never had dermal capillaries due to the absence of the dermal bulge. Based on these results, the cutaneous air uptake in S. gigas would seem to be more effective in the upper body regions that are most often exposed to air than in the lower body regions, however, cutaneous air uptake is not likely to occur in the appendages.     

Keratinization of the outer surface of the avian scutate scale: Interrelationship of alpha and beta keratin filaments in a cornifying tissue

Summary The outer surface of adult Gallus domesticus scutate scale was studied as a model for epidermal cornification involving accumulation of both alpha and beta keratins. Electron-microscopic analysis demonstrated that the basal cells of the adult epidermis contained abundant lipid droplets and that filament bundles and desmosomes were distributed throughout the cell layers. Indirect immunofluorescence microscopy and double-labeling immunogold-electron microscopy confirmed that the stratum germinativum contained alpha keratin but not beta keratin. Beta keratins were first detected in the stratum intermedium and were always found intermingled with filament bundles of alpha keratin. As the differentiating cells moved into the outer regions of the stratum intermedium and the stratum corneum, the large mixed keratin filament bundles labeled increasingly more with beta keratin antiserum and relatively less so with alpha keratin antiserum. Sodium dodecyl sulfate-polyacrylamide gel analysis of vertical layers of the outer surface of the scutate scale confirmed that cells having reached the outermost layers of stratum corneum had preferentially lost alpha keratin. The mixed bundles of alpha and beta keratin filaments were closely associated with desmosomes in the lower stratum intermedium and with electron-dense aggregates in the cytoplasm of cells in the outer stratum intermedium. Using anti-desmosomal serum it was shown that these cytoplasmic plaques were desmosomes.     

Morphology and ultrastructure of possible integumentary sense organs in the estuarine crocodile (Crocodylus porosus)

The skins of crocodylids and gavialids can be distinguished from those of alligatorids by the presence of darkly pigmented pits, known as integumentary sense organs (ISOs), on the postcranial scales. The structure of ISOs, in Crocodylus porosus, was studied using light microscopy and scanning and transmission electron microscopy. The stratum corneum of the epidermis in the area of the ISO is thinner, while the stratum germinativum is thicker, relative to other regions of the integument. Beneath the epidermal layer the ISO region has a paucity of collagen fibers relative to the rest of the dermis. Widely dispersed fibrocytes, nerve terminals, and chromatophores occur throughout the ISO region of the dermis, but these elements are concentrated in the area immediately beneath the stratum germinativum in the ISO region. The morphology of the ISOs suggests that they are sensory organs. It has traditionally been assumed that sensory organs on the amniote integument have a mechanosensory function. However, alternate functional interpretations of this structure are possible, and a resolution awaits further work. © 1996 Wiley-Liss, Inc.     

The structure of the canary's incubation patch

The gross morphology, histology and ultrastructure of the canary's incubation patch and the ventral apterium from which it arises are described. The apterium is vascularized by pectoral, external mammary, incubation, and prepubic arteries. It is innervated by cutaneous branches of spinal nerves. It has a surface area of 6 cm². Its epidermis is a stratified squamous epithelium with basal, intermediate, transitional and cornified layers. Cells in the stratum germinativum contain a normal array of organelles, but are characterized by tonofilaments, desmosomes and interdigitating surfaces. Cellular organelles disappear in the stratum transitivum and are replaced by large vacuoles and keratohyalin bands. Nonmyelinated nerve fibers are abundant in the stratum germinativum. The dermis consists of (1) an avascular layer of dense collagen subjacent to the epidermis and containing many nonmyelinated nerves, and (2) an underlying layer of areolar connective tissue containing blood vessels, lamellar corpuscles and nerves. A layer of coarse elastic fibers, reinforced by collagen and smooth muscle, separates the dermis from subcutaneous tissue. In contrast to the ventral apterium, the incubation patch is featherless and visibly hypervascular and edematous. Its epidermis is both hypertrophic and hyperplastic. Large spaces separate cells in the stratum germinativum. The visible hypervascularity is due to hyperemia and increased number and size of blood vessels in the dermis. Visible edema is due to the accumulation of fluid interstitially. Although no histological differences exist among various regions of the ventral apterium, such differences are present in the incubation patch.     

The permeability barrier in the epidermis of the grass snake during the resting stage of the sloughing cycle

Summary Tracer and freeze-fracture replication techniques show that there are two morphologically and topographically distinct permeability barriers in the epidermis of the grass snake. Tight junctions interconnect the apico-lateral plasma membranes of the uppermost living cells, establishing an ionic or osmotic gradient between the stratum germinativum and alpha layer. The second barrier is formed by intercellular lipid sheets in the overlying mesos layer, which are very similar to the barrier found in the stratum corneum of mammals.     

Epidermal tissue homeostasis. III. Effect of hydrocortisone on cell pool size, cell birth rate and cell loss in normal toads and in toads deprived of the pars distalis of the pituitary gland

It has previously been shown that in toad epidermis the cell birth rate (Kb) exceeds the rate of cell loss through moulting (Kd) and that the 'surplus' of cells seems to be removed in a controlled manner. Assuming that the epidermis is non-expanding, a Kb/Kd ratio greater than 1 indicates that cell deletion additional to desquamation takes place. In normal toads this ratio is 2-3. Following implantation of hydrocortisone pellets into intact toads (release rate, 18 micrograms/g toad/d), the Kb/Kd ratio, over a period of 14 d of hormone treatment, had increased to about 7, due mainly to an increased Kb and to a lesser extent to a decreased Kd. No change in the epidermal cell pool size had taken place. It was previously shown that, following removal of the pars distalis of the pituitary gland, the Kb/Kd ratio decreased with time, due to a decreasing Kb and an increasing Kd, eventually leading to a decreased epidermal cell pool size. In this paper it is shown that, in pars distalisectomized toads with hydrocortisone pellets implanted, the Kb/Kd ratio is restored to control levels by a restoration of the Kb as well as the Kd. The results differ from those of previous studies in which ACTH or adrenocorticosteroids were administered discontinuously (by injection). Thus, by experimental manipulation, different Kb/Kd ratios can be obtained: low (less than 1, pars distalis ablation), medium (2-3, normal toads) and high (7, hydrocortisone implantation). The potentiality of this unique situation in analysing the important question of how the 'surplus' cells are deleted is discussed.     

Relationship between nutritional state and testes function, together with observations on patterns of feeding, in the toad, Bufo bufo bufo

The effects of 10 weeks of starvation, restricted feeding, or ad lib. feeding on nutritional state and testes functions were investigated in male toads that had artificially hibernated in a refrigerator before being placed at room temperature. Food intake increased for about four weeks in both the fed groups. After this initial period the toads on restricted food ate their ration for the remaining part of the experiment, and they developed fat bodies of sizes characteristic of male toads during late summer in nature. The toads fed ad lib. increased food intake to about twice that of those on restricted food. After two weeks of high feeding rate food intake rapidly declined and remained low to the end of the experiment, when the fat bodies were larger than normally seen in nature. At the end of the experiment spermatogenetic activity had declined to a low level in the starving toads, whereas it was high in the fed toads. Starvation for 10 weeks did not affect the late stages of spermatogenesis. Interstitial cells and thumbpads remained reduced in the starving toads, but were restored in the fed toads. The importance of the annual cycle in nutritional state for gonadal cycles in male and female toads is discussed.     

中华大蟾蜍多种组织内5—羟色胺免疫染色细胞的分布

The distribution of 5-hydroxytryptamine (5-HT) immunostaining cells in the digestive tracts (hibernation and nonhibernation), the brain and other various tissues of Bufo bufo gargarizans was studied by peroxidase anti-peroxidase immunocytochemical method. In the brain, 5-HT immunostaining cells were localized in the raphen nuclear area of brain stem and in the ependyma cell area of the ventriclus tertius of diencephalon. These immunostaining cells were round or oval. The cells usually possess processes which were filled with immunoreactive substance. Some of the processes were contact with the processes of other cells. A few 5-HT positive reactive nerve fibers were observed in the brain stem and the diencephalon. The density of 5-HT immunostaining cells in the digestive tubes were the highest in the pylorus, fundus, cardia of gaster, and moderate in the esophagus and duodenum and the lowest in the large intestine and the small intestine. The density of 5-HT immunostaining cells in the digestive tubes were higher in nonhibernant toads than in hibernant toads. By the statistical method, the difference of the density between the two sorts of toads were notable (P less than 0.05). The 5-HT immunostaining cells were visualized to distribute between the epithelium cells of the mucosa or the epithelium cells of gland. These positive cells usually had one or more processes which contained 5-HT immunoreactive substance. Some were reached into lumen surface of the gland or intestine. Some were extended into lamina propria through the basal membrane. These results indicate that the 5-HT immunostaining cells in digestive tubes could release 5-HT by both endocrine and exocrine ways.     

An interactive microcomputer-based system for the quantitative analysis of stratified tissue sections

This paper describes a microcomputer-based system that allows diagnostically relevant properties of stratified tissue sections to be objectively measured. The results of detailed nuclear image analyses are examined in the broader context of the position of nuclei within the tissue section and relative to histologic structures and each other. Quantitative measures are obtained for important morphometric and densitometric properties of individual nuclei and mitotic figures and especially for their distribution and orientation within the tissue section relative to the stratum germinativum and each other. Recorded karyometric and histometric parameters include measures of nuclear DNA content (based on optical density measurements), size, roundness, texture, shape, distance to the basal layer, angle with the stratum germinativum, epithelial height and proximate nuclear distance. Statistics generated describe normalized mitotic density as a function of depth in the epithelium, and a composite mitotic index is produced based upon weighting of these densities relative to their distance from the stratum germinativum. These properties and derived statistics may be examined as a function of epithelial depth and nuclear type and may be plotted as a function of other diagnostic features in addition to the observed stratum. The system is one part of microTICAS-STRATEX, an expert diagnostic system for the clinical evaluation of stratified tissue sections, now under development as an outgrowth of the microTICAS system. Results of measurements made with this system will be compared with site-specific and diagnosis-specific reference profiles and used in conjunction with clinical data derived from a data base at the University of Chicago of over 1.5 million patients to generate diagnostic and prognostic evaluations.     

Morphological Characteristics of the Dorsal Skin of Two Hynobiids and Their Adaptive Role in Aquatic and Terrestrial Habitats

The morphological characteristics of the dorsal skin of trunk in two species of hynobiid salamanders, Batrachuperus pinchonii and Hynobius chinensis were examined by light microscopy. The basic structures of the skin in the two species are similar and consist of two layers: epidermis and dermis. The epidermis consists of stratum corneum, stratum intermedium and stratum germinativum, while the dermis is composed of a stratum spongiosum and stratum compactum. However, some species-specific variation has been identified(e.g., the distribution of capillary vessels and gland cells, and the thickness of skin). H. chinensis is a terrestrial species and only lives in water during breeding period, but B. pinchonii is aquatic and remains aquatic throughout its lifetime. The differences in the distribution of capillary vessels and gland cells are related to their different habitats, and show a morphological adaptation.     

Zu den Nervenendigungen (Merkeische Endigungen) in der haarlosen Nasenhaut der Katze

Zusammenfassung Die Nervenendigungen in der Epidermis der haarlosen Haut der Katzennase wurden licht- und elektronenmikroskopisch untersucht. Im Stratum germinativum werden Merkeische Endigungen gefunden. Sie bestehen aus spezialisierten Zellen und je einer anliegenden verdickten Nervenfaser. Diese Rezeptoren werden in zwei Formen beobachtet. Einzelne Zell-Neurit-Komplexe liegen in der Basalschicht der Epidermis über den bindegewebigen Papillen und Gruppen solcher Komplexe im Stratum germinativum der Epidermalleisten (Epithelialzapfen). Die spezialisierten Zellen sind mit den umliegenden Epidermiszellen durch Desmosomen verbunden.Freie Nervenendigungen konnten in der Epidermis der haarlosen Nasenhaut nicht beobachtet werden.

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Nerve endings (Merkel's corpuscles) in hairless skin of the nose of cat

Summary The nerve endings in the epidermis of the hairless skin of the nose of the cat have been studied by means of light and electron microscopy. In the stratum germinativum there are Merkel's corpuscles. They consist of specialized cells with a thickened nerve fibre adjacent to each one of them. These receptors have been observed in two forms. Single cell-neurit-complexes are lying in the basal layer of the epidermis above the connective tissue papillae, and groups of these complexes are situated in the interpapillary pegs of the epidermis. The specialized cells are connected by desmosomes with the neighbouring cells of the epidermis. There are no free nerve endings in the hairless skin of the nose.