Cellular types in the gill arch of the teleost Cyprinus carpio (Cyprinidae, Pisces). A histochemical and ultrastructural study

On adult specimens of the common carp (Cyprinus carpio), we have carried out a histochemical and ultrastructural study of the epithelia which form the gill arch. Secondary lamellae have two cellular types, granular and mucous, which produce neutral carbohydrates and proteins rich in tryptophane, and another mucous cell type which contains glycosaminoglycans. In gill rakers, three cellular types show different histochemical behaviour: 1) granular cells elaborate neutral mucosubstances; 2) a second cell type contains glycosaminoglycans,, and 3) a third cell type secretes neutral and acid carbohydrates. We discuss the possible role of these cells according to their secretion. We describe pillar and chloride cells in secondary lamellae, and chloride and neuroendocrine-like cells in gill rakers.     

Deviations from the flux ratio equation for chloride ions in ouabain- and acetazolamide-treated frog skin.

In order to establish whether or not chloride ions behave as freely moving particles in "passive", i.e. ouabain- and acetazolamide-treated, frog skin, tracer fluxes of 36Cl-have been measured while a voltage (generally +40 mV, serosal side positive) across the skin was applied. Ussing's flux ratio equation has been used as a criterion for this type of transport. One group of skin samples exhibited significant exchange diffusion phenomena. Most samples in a second group either behaved according to the flux ratio equation of showed significant and extreme exchange diffusion. From flux ratios obtained at two different voltages across various skin samples, showing extreme exchange diffusion, it appeared that the simple form of Kedem and Essig's law derived from irreversible thermodynamics, which is valid for homogeneous systems, does not apply to the type of exchange diffusion found. The system can, however, be described by a 1:1 exchange mechanism working in parallel with a diffusional pathway. The ratio exchange flux/observed efflux must then have a constant value (0.83) at the voltages appled, which implies that the exchange flux is voltage dependent. By comparison with iodide flux experiments as carried out by Ussing, it is shown that iodide exhibits the same type of exchange diffusion. A carrier, possibly responsible for the observed behaviour, is described.     

Categorization of the mitochondria-rich cells in the gill epithelium of the freshwater phases in the life cycle of lampreys

The distribution and ultrastructure of the mitochondria-rich (MR) cells in the gills of larval (ammocoetes) and adult lampreys (Petromyzon marinus and Geotria australis) have been studied. One type of MR cell, which is found only in ammocoetes, occurs in groups on and between gill lamellae. Freeze-fracture replicas show that the apical membrane of this ammocoete MR cell contains globular particles. The second type of MR cell, which is present in both ammocoetes and adults in freshwater, is located between lamellae and at the base of the filament. This cell usually occurs singly and is typically intercalated between ammocoete MR cells in larval lampreys and between pavement cells and pavement and chloride cells in adult lampreys. It contains rod-shaped particles in either the apical membrane (subtype A) or, far less frequently, the lateral membrane (subtype B) and in membranes of cytoplasmic vesicles and tubules. These features characterize this intercalated MR cell as a member of a group of MR cells that are also found in urinary epithelia of tetrapods and the amphibian epidermis, where they are involved in H⁺ and HCO₃ ^- secretion. Because this type of MR cell disappears when the young adult lamprey enters the sea and reappears immediately after the fully grown adult re-enters freshwater on its spawning run, it is presumably essential for osmoregulation in freshwater. On the basis of electrophysiological studies on frog skin, it is proposed that the subtype A of the branchial intercalated MR cell of lampreys provides the driving force for the Na⁺ uptake by active H⁺ secretion. By analogy with urinary epithelia, the subtype B cells may exchange Cl^- for HCO₃ ^-.     

Deviations from the flux ratio equation for chloride ions in ouabain- and acetazolamide-treated frog skin

In order to establish whether or not chloride ions behave as freely moving particles in “passive”, i.e. ouabain-and acetazolamide-treated, frog skin, tracer fluxes of ³⁶Cl⁻ have been measured while a voltage (generally +40 mV, serosal side positive) across the skin was applied. Ussing's flux ratio equation has been used as a criterion for this type of transport. One group of skin samples exhibited significant exchange diffusion phenomena. Most samples in a second group either behaved according to the flux ratio equation or showed significant and extreme exchange diffusion. From flux ratios obtained at two different voltages across various skin samples, showing extreme exchange diffusion, it appeared that the simple form of Kedem and Essig's law derived from irreversible thermodynamics, which is valid for homogeneous systems, does not apply to the type of exchange diffusion found. The system can, however, be described by a 1 : 1 exchange mechanism working in parallel with a diffusional pathway. The ratio exchange flux/observed efflux must then have a constant value (0.83) at the voltages applied, which implies that the exchange flux is voltage dependent. By comparison with iodide flux experiments as carried out by Ussing, it is shown that iodide exhibits the same type of exchange diffusion. A carrier, possibly responsibe for the observed behaviour, is described.     

Gill morphology in the zebrafish, Brachydanio rerio (Hamilton- Buchanan)

A light and electron microscopic study of the gills of the zebrafish, Brachydanio rerio , were made to serve as a morphological basis for future investigations. It was found that for fixation of B. rerio gills, a mixture of 1·5% gluturaldehyde and 1·5% paraformaldehyde gives a mucus-free surface. Morphometric measurements of structural components of the gill secondary lamellae were made. Observations at SEM were correlated with those made at TEM. The different cell types in the branchial epithelium were characterized. Chloride cells were mainly located in the interlamellar regions and on the afferent side of the primary lamellae. Two morphologically different chloride cells were seen. The first type communicates with the external environment through a reservoir-like lumen, which is normally absent in freshwater fishes. The second type of chloride cell has more direct contact with the ambient water, resembling chloride cells from other freshwater fishes. Another cell type with features similar to those of the rodlet cell was frequently observed. This cell is interposed between other types of cells in the epithelium, and sometimes junctional complexes were present between the rodlet cell and surrounding cells.     

Comparative effects of catecholamines, angiotensin II and antidiuretic hormone on chloride transport in toad skin

In this work we present data which show stimulation of Cl- transport in the isolated toad skin by four agonists: L-isoproterenol, L-adrenalin, angiotensin II and ADH. This response was demonstrated by raising mucosal amiloride concentration to block the sodium transport in the skin. With transepithelial sodium influx almost completely inhibited, it was likely that the response reflected transport events in the glands. Inhibition of the bioelectric parameters by removing chloride from the serosal bathing medium in the amiloride-inhibited preparation eliminated the response to all four agents, indicating that these responses are chloride dependent. The similarity of the bioelectric responses of the amiloride-treated preparation to db cAMP and to the four agents tested in this work add further evidence that this second messenger may account largely for the Cl- transport mechanism in the toad skin glands by increasing the apical membrane permeability to Cl-.     

Skin growths of the head and neck region in elderly patients--analysis of two five-year periods in General Hospital Karlovac, Croatia

Skin lesions, benign and malignant, are more common in the older than younger people. Due to the aging of the skin and greater exposure to the impact of ultraviolet rays, their long-term cumulative negative effect, skin lesions are more common in the head and neck area than on other parts of the skin. This paper analyses the pathohistological diagnosis of material after the surgical excision of tumors of the skin on the head and neck of persons older than 60, at the General Hospital Karlovac through two five-year period. The first period is the period from 2006 to 2010 and the second one from 1996 to 2000. The aim was to determine for each period the type and variety of skin lesions, the prevalence of the disease, the age and gender structure, and finally to compare the two periods. The total number of excisions in the first period was 1200, and in the second 513. In both periods more excisions was done in women than men, if compared it comes to 1.4:1. The ratio of malignant (basocellular carcinoma, squamous cell carcinoma and melanomas), and benign tumors (seborrheic keratoses, moles and others) in the first period was 49.3 to 46.3%, and in the second 56.7 to 42.1%. Precancerous lesions (actinic keratoses and Mb Bowen's disease) accounted for 4.3% of lesions in the first and 1.2% in the second period. The total number of basocellular carcinoma was 481/232, which makes 81.3% of all malignant tumors in the first, or 79.7% in the second period. Our results showed that around half of all skin lesions removed in both periods consisted of malignant tumors, among which the most common were basal cell carcinomas. High prevalence of malignant non-melanoma skin cancers, 48.7 and 56%, indicate the importance of protection from UV radiation, and early detection and treatment of skin cancer and precancerous lesions.     

Human skin reconstructed in vitro as a model to study the keratinocyte, the fibroblast and their interactions: photodamage and repair processes

The protective role of the skin is provided by the two major compartments of the skin, dermis and epidermis. Both are affected in the long term by consequences of sun exposure such as skin photoaging and cancer development. Characterization of UV-induced skin response at cellular and molecular levels is needed for prevention or correction of these long term effects. The human skin reconstructed in vitro, comprising both a living dermal equivalent and a fully differentiated epidermis represents a predictive tool to characterize wavelength and cell type specific biological damage together with tissular distribution. While UVB directly affects epidermis, inducing DNA lesions and apoptotic sunburn keratinocytes, UVA radiation can directly target the dermal compartment through ROS generation, dermal fibroblasts alterations and extracellular matrix (ECM) modifications. Interactions between the two compartments have also been found, especially for MMP1 induction. In the normal population, photodamage can be repaired through specialized systems. Using skin cells from Xeroderma pigmentosum (XP, a photosensitive and cancer-prone disease), a DNA-repair deficient skin has been developed in vitro. Specific features due to intrinsic XP cell phenotype have been discovered, some of them being indicative of early steps of neoplasia and suggesting a particular role for stroma-epithelium interactions. Finally, human reconstructed skin can be used for approaches designed to regenerate photodamaged skin. The dermal-epidermal junction (DEJ), which is crucial for skin cohesion, is drastically altered in photo-aged skin. The three-dimensional skin model allowed to visualize the improving effects of vitamin C on the DEJ. Modified skin models, lacking one cell type, allowed us to determine the cellular origin of the different markers, their spatial localization, and the respective roles and interactions of keratinocytes and fibroblasts during DEJ formation. All together these studies give a global and tissular view concerning the effects of UV light on skin cells and emphazise the interest of such models for general aspects of cellular biology. By allowing the control of cells used to reconstruct the model and their origin, these studies make it possible to assess the respective role of the two major cellular actors of the skin as well as their interactions. Ongoing research about incorporating other cell types may certainly give rise to even more relevant models.     

Structure and Function of the Chloride Cell of Fundulus heteroclitus and Other Teleosts

Teleosts, the bony fishes, inhabit both freshwater and seawaterenvironments. Some euryhaline fish, such as Fundulus heteroclitus,alternate between the two milieux several times daily. Regardlessof adaptation, the gills of these animals possess a highly specializedcell type called the chloride cell. This cell contains numerousmitochondria and exhibits a greatly amplified basolateral cellsurface richly endowed with Na,K-ATPase. Recent studies on isolatedopercular epithelia containing chloride cells have demonstratedactive chloride secretion and passive transepithelial sodiummovements, and have established the chloride secretory roleof this cell type in seawater-adapted teleosts. Current modelssuggest that chloride transport occurs via a transcellular route.Seawater chloride cells exist in multicellular units and sharesimple, shallow tight junctions which are thought to be theroute for passive sodium movement. Freshwater chloride cells,whose function remains to be elucidated, are generally describedas existing in a unicellular configuration. However, recentobservations in Fundulus heteroclitus adapted to salinitiesas low as 1% sea water reveal that chloride cells persist inmulticellular complexes with apical crypts. Strikingly, tightjunctions between chloride cells in this freshwater environmentare deep     

Eosinophils and mast cell homogeneity of the guinea pig eyelid skin, conjunctiva, and ileum

Mast cell heterogeneity has been described on the basis of differential staining reactions, light microscopic morphology, anatomic location, degranulation after polyamines, biochemical contents, growth requirements, and reactions to lymphokines. We have demonstrated typical "connective-tissue mast cells" by using anatomic criteria, histological staining reactions, electron microscopy, and reaction to compound 48/80 in the guinea pig conjunctiva, eyelid skin, and ileum. A second, much larger population of cells in the ileal mucosa and the conjunctiva, and rarely in the eyelid skin stained reddish-blue with acid toluidine blue in tissue fixed in ethanol-acetate-lead subacetate (BLA) and with alkaline Giemsa in formaldehyde-fixed tissue, did not stain with ethanolic or acid toluidine blue in formaldehyde-fixed tissue or with alkaline Giemsa in BLA-fixed tissue, and did not degranulate after 48/80 treatment. These are features of the rat intestinal "mucosal mast cells"; however, ultrastructural and light microscopic studies with the orcein Giemsa stain demonstrated these cells in the guinea pig to be eosinophils. Tissue culture, biochemical, and immunological studies indicate the existence of a second type of mast cell (bone-marrow-derived mast cell), ultrastructurally almost indistinguishable from the connective tissue mast cell. Our studies demonstrate only one mast cell type in the guinea pig and support the contention that other forms of mast cells are immature forms or variants of the connective-tissue mast cell.     

The volume of mitochondria-rich cells of frog skin epithelium

Summary The pathway for movement of chloride ions across frog skin is not well understood. Mitochondria-rich (MR) cells have been proposed as the route for chloride across the skin. To test this hypothesis we studied the MR cells of the skin of the frog,Rana pipiens, by quantitative light microscopic determination of cell volume. MR cell volume was influenced by changes in the chloride concentration or osmolality of the outside bathing solution. MR cells shrank about 23% when all chloride was removed from the outside (mucosal) bathing solution. MR cells were also shown to be responsive to changes in the osmolality of either the mucosal or serosal bath. Osmotically-induced swelling caused by dilution of the serosal bath resulted in volume regulatory decrease. These results are consistent with the hypothesis that MR cells constitute the pathway for chloride movement across frog skin.     

Significance of eIF4E expression in skin squamous cell carcinoma

Cutaneous squamous cell carcinoma (SCC) is a malignant tumour of keratinising epidermal cells. This type of skin cancer is the second leading cause of death after melanoma, and it is the second most common type of non-melanoma skin cancer after basal cell carcinoma. The cellular and molecular events involved in the progression of skin cancers are largely unknown. Increased protein synthesis is necessary for the transition of cells from quiescence to proliferation. Translational control is critical for the proper regulation of the cell cycle, tissue induction and growth. Eukaryotic initiation factor eIF4E, an important regulator of translation, plays critical roles in neo-plastic transformation and cancer progression. We investigated eIF4E expression in 49 skin samples (six normal tissues, eight Bowen diseases, seven stage I, 10 stage II, 13 stage III and five stage IV SCCs). Results obtained demonstrated that all SCC samples, evaluated by SDS-PAGE, Western blotting and cap-affinity chromatography using m7GTP-sepharose, presented eIF4E expression (13.6+/-1.2), whereas, starting from stage 0 (4.1+/-0.9) to stage I (7.4+/-1.4), stage II (12.1+/-2.4), stage III (18.1+/-3.0) and stage IV (26.2+/-3.8) SCCs, a constant and significant increase of protein over expression (P<0.001) was observed. A high expression of eIF4E is correlated with advanced stages. The results presented in this study demonstrate a possible role of eIF4E in SCC.     

The organization of ampullary sense organs in the electric fish, Gymnarchus niloticus

Three types (A, B, and C) of ampullary sense organs occur in the skin of Gymnarchus niloticus. In type A the ampulla is connected to the surface of the skin by an open duct whereas in B and C organs it is closed, though overlain by specialized epidermal cells. In each case the receptor cell surface in contact with the ampullary lumen bears microvilli; these are more highly developed in B and C organs than in type A. Fine structural observations are consistent with the view that the organs are electric receptors of three different types.     

Ultrastructural features of the retina and optic nerve of Strombus luhuanus,a marine gastropod

The retina and optic nerve of Strombus luhuanus were examined by transmission electron microscopy in order to provide an ultrastructural basis for their electrophysiological responses, described elsewhere. The retina exhibits a distinct rhabdomeric layer and layers of cell nuclei and neuropile. These layers are comprised predominantly of three cell types that can be readily distinguished on the basis of their shape, their nuclei and cytoplasmic inclusions such as vesicles and filaments. One type of cell, apparently a photoreceptor that depolarizes in response to photic stimulation, possesses a long distal segment with microvilli; such distal segments comprise the bulk of the rhabdomeric layer. A second cell type, which appears to be supportive in function, contains a bundle of tightly packed tonofilaments that extend across the retina from the capsule to the vitreous body; this cell is quite narrow except in the region near the rhabdomeric layer, where it is expanded and wraps around the other cell types. A third type of cell possesses many short microvilli that project from its apical end into the rhabdomeric layer; it may be a second type of photoreceptor or another type of neuron. The retina also contains bundles of cilia that appear to project from a possible fourth type of cell. The layer of neuropile contains numerous processes that exhibit a variety of vesicle types and structures generally associated with synapses; these appear to play a role in mediating inhibitory and excitatory interactions between the retinal neurons. The optic nerve exhibits two populations of fiber distinguishable on the basis of mean diameter. Fibers in these two populations apparently yield “on” and “off” discharges in response to photic stimulation of the eye.     

Mitochondria-rich cells in gills and skin of an African lungfish, Protopterus annectens

We used scanning electron microscopy, the vital dye DASPEI and an antibody to the inner mitochondrial membrane to study the presence and localisation of mitochondria-rich cells in the gills and skin (opercular, dorsal and ventral) of the lungfish Protopterus annectens in its free-swimming conditions and at the beginning of aestivation. In the free-swimming period, the gills were short and thick and the pavement cells were extremely large (30-40 microns). The mitochondria-rich cells, which were distributed in the secondary and primary epithelium, occurred as two morphologically different types, i.e. elongated and oval, similar to the alpha and beta chloride cells of fresh water teleosts. In the skin, only one type of mitochondria-rich cells was found, resembling the alpha chloride cells. All the mitochondria-rich cells distributed in the gills and skin were labelled with anti Ca(2+)-ATPase serum indicating the possible uptake of Ca2+ at freshwater chloride cell level. At the start of aestivation, the skin and gills were covered by a thick layer of mucus and the epithelium of the gills was reduced. The mitochondria-rich cells were almost completely covered by the pavement cells.     

Bleomycin treatment of chick fibroblasts causes an increase of polysomal type I procollagen mRNAs. Reversal of the bleomycin effect by dexamethasone

Bleomycin treatment of primary chick skin fibroblasts and chick lung fibroblasts resulted in a selective dose-dependent increase of cell layer procollagen synthesis. Solid support hybridization of total cellular RNA to 32P-labeled pro-alpha 1(I) and pro-alpha 2(I) cDNAs did not indicate an increase of total cellular procollagen type I mRNAs in bleomycin-treated cells. However, bleomycin treatment of chick skin fibroblasts causes a redistribution of procollagen type I mRNAs within the nuclear, cytoplasmic, and polysomal subcellular fractions. Both the nuclear and cytoplasmic procollagen type I mRNAs are significantly decreased in concentration after bleomycin administration. In contrast, the polysomal procollagen type I mRNAs are significantly increased in both chick skin and lung fibroblasts treated with bleomycin. Administration of dexamethasone to bleomycin-treated fibroblasts resulted in a reversal of the bleomycin-induced increase in cell layer procollagen synthesis. The increased amounts of polysomal procollagen type I mRNAs in bleomycin-treated cells were also reduced by subsequent administration of dexamethasone. These data indicate that bleomycin treatment of chick skin and chick lung fibroblasts results in a specific increase in procollagen synthesis in the cell layer which is mediated by elevated levels of polysomal type I procollagen mRNAs via a repartitioning of these mRNAs within the fibroblast. Furthermore, dexamethasone reverses the bleomycin-induced elevations of both cell layer procollagen synthesis and polysomal type I procollagen mRNAs.     

Active chloride cell density in some tissues of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) larvae during the early development stage

In this study, active chloride cell density in some tissues (gill arch epithelium, skin, and yolk-sac membrane) of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) larvae during the early development stage was investigated using a vital fluorescence staining technique. It was found that the numbers of active chloride cells were very variable, depending on the tissue and age of the larvae. Active chloride cells were most abundant in the skin and yolk-sac membrane, but less so in the gill arch epithelium of newly hatched larvae. With larval age, the density of active chloride cells in the gill epithelium increased, while that in the skin and yolk-sac membrane decreased.     

Electrical parameters of the toad skin: effects of forskolin.

Forskolin stimulated short-circuit current (SCC) and transepitelial electrical conductance (G) in the isolated skin of the toad Bufo arenarum in a concentration-dependent manner, between 1.0 x 10(-6) and 2.4 x 10(-5) M. At the latter concentration, glandular secretion appeared to be stimulated also. The increase in G was considerably greater in skins bathed in Ringer solution than in solutions containing no chloride. The increased SCC was abolished by amiloride, a specific blocker of sodium transport in amphibian membranes, irrespective of the anion present in the solution bathing the skin. G was also decreased by amiloride to control values in skins bathed in solutions without chloride, but remained elevated in the presence of Cl-. The increase in SCC following exposure to forskolin, 4.4 x 10(-6) M, was not altered when furosemide, a specific blocker of chloride transport, was present in the Ringer solution bathing the dermal side of the skin. The response to forskolin, 2.4 x 10(-5) M, however, was significantly decreased by dermal furosemide; the inhibitor was ineffective in the absence of chloride. The data indicate that forskolin acts on at least two sites: stratum granulosum cells (the main pathway for sodium transport, and an alternate site, responsible for the increase in permeability to chloride. In addition, at high concentration of the agent, glandular secretion is also stimulated. The data suggest that the adenylate cyclase-cyclic AMP system is involved in the regulation of the permeability of the toad skin to sodium and chloride, probably by separate cell types.     

The renal chloride cell of the fresh-water catfish,Parasilurus asotus,with special reference to the tubular membrane system

The kidney of the fresh-water catfish, Parasilurus asotus, was examined by electron microscopy. A special type of cell, very similar in appearance to the chloride cell of the teleostean gill filaments, is found in the kidney and is referred to as a renal chloride cell. This cell is characterized by an extensive tubular membrane system with a rather constant diameter of approximately 600 A. A number of mitochondria are closely associated with this system. Application of ruthenium red as an extra-cellular space marker revealed that the tubular system is a highly organized derivative of the cell membrane, infolded from the basal and lateral surfaces of the cell. The fine structural resemblance to other types of cells known to possess active transport of electrolytes suggests that these cells are involved in intrarenal osmoregulation.     

Structure of the skin of Agonus cataphractus (Teleostei)

The skin of the scuted teleost Agonus cataphractus has been investigated by histochemical methods, SEM and TEM. The anterior dorsal skin bears tubercles of epidermis overlying tiny ossifications (scutelets) superficial to the main scutes. The epidermis secretes a cuticular layer containing acidic non-sulphated glycoproteins, but there are no mucous goblet cells in the external skin. Non-mucous sacciform cells of two types are present in the epidermis, also numerous chloride cells. Scanning electron microscopy reveals variation in the microridge pattern of superficial epithelial cells, thought to relate to arrival at the surface and secretion of the cuticle. The major scutes overlap anteriorly, contrary to the normal arrangement of scales, indicating that they are secondary ossifications. The type of mineralization is similar to that of acellular bone. The scutes are set directly in the collagen of the dermis. They have a girdered structure with radial and cross bars, inserting on both faces of a thin plate. The interstices are occupied by unmineralized collagen, and extrinsic collagen bundles impinge on the bone. Non-mineralized parts of the dermis contain tracts of microfibrils in addition to collagen; these are best developed in the flexible gular skin and in the barbels and are interpreted as elastic tissue, although an amorphous component was not seen. The barbels have a core of connective tissue without a cartilaginous skeleton and bear taste buds and numerous chloride cells.