Functional morphology of coronal and peristomeal podia in Sphaerechinus granularis (Echinodermata,Echinoida)

Summary Coronal podia of Sphaerechinus granularis are anchoring (adhering) appendages involved in either locomotion or capture of drift materials. Adhesion is not due to the presumed sucker action of the disc but relies entirely on secretions of the disc epidermis. Peristomeal podia function in wrapping together food particles or food fragments in an adhesive material thus facilitating their capture by the Aristotle's lantern. In both types of podia, the disc epidermis is made up of four cell types: non-ciliated secretory cells (NCS cells) that contain graules whose content is at least partly mucopolysaccharidic in nature, ciliated secretory cells (CS cells) containing granules of unknown nature, ciliated non-secretory cells (CNS cells) and support cells. The cilia of CS cells are subeuticular whereas those of CNS cells, although also short and rigid, traverse the cuticle and protrude in the outer medium. All these cells are presumably involved in an adhesive/de-adhesive process functioning as a duogland adhesive system. Adhesive secretion would be produced by NCS cells and de-adhesive secretion by CS cells. These secretions would be controlled through stimulations by the two types of ciliated cells (receptor cells) which presumably interact with the secretory cells by way of the nerve plexus. This model of adhesion/de-adhesion fits well with the activities of both coronal and peristomeal podia. The secretion of NCS cells would make up a bridge of adhesive material between a podium and the substratum (coronal podia) or would coat and gather food particles (peristomeal podia), respectively. The de-adhesive material enclosed in the granules of CS cells would allow the podia (either coronal or peristomeal) to easily become detached from the substratum and to always remain clear of any particles.Research Assistant, National Fund for Scientific Research (Belgium)     

Ultrastructure of the Penicillate Podia of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata) with Special Emphasis on the Epidermal Sensory-Secretory Complexes

The spatangoid echinoid Echinocardium cordatum possesses specialized penicillate podia that handle sediment particles during burrowing and feeding. Epidermal complexes, which occur on podial surfaces directly contacting the sediment, each comprise four cells: a non-ciliated secretory cell containing granules rich in mucopolysaccharides (NCS cell), a ciliated secretory cell containing granules of unknown composition (CS cell), and two ciliated non-secretory cells (CNS cells). The cilium of the CS cell is subcuticular whereas that of each CNS cell traverses the cuticle. We propose that these four cells constitute a sensory-secretory complex wherein the ciliated cells are sensory cells and the secretory cells function for adhesion and de-adhesion. More exactly, an NCS cell adhesive and a CS cell de-adhesive would be sequential and would be initiated by two successive stimulations transduced by cilia when the podium touches the sediment. Cilia that first contact the sediment are those protruding through the cuticle from the CNS cells. Their stimulation would result in the secretion of an adhesive material by the NCS cells. Subsequently, the subcuticular cilia of CS cells would be stimulated when the podial digitations closely squeeze the substrate, and this would induce the secretion of a de-adhesive. These two antagonistic secretions would allow the podium to pick up and discharge sediment repetitively during burrowing and feeding.     

The attachment complex of brachiolaria larvae of the sea star <Emphasis Type="Italic">Asterias rubens</Emphasis> (Echinodermata): an ultrastructural and immunocytochemical study

The attachment complex of brachiolaria larvae of the asteroid Asterias rubens comprises three brachiolar arms and an adhesive disc located on the preoral lobe. The former are used in temporary attachment and sensory testing of the substratum, whereas the latter is used for permanent fixation to the substratum at the onset of metamorphosis. Brachiolar arms are hollow structures consisting of an extensible stem tipped by a crown of dome-like ciliated papillae. The papilla epidermis is composed of secretory cells (type A, B and C cells), non-secretory ciliated cells, neurosecretory-like cells and support cells. Type A and B secretory cells fill a large part of the papilla epidermis and are always closely associated. They presumably form a duo-gland adhesive system in which type A and B cells are respectively adhesive and de-adhesive in function. The adhesive disc is an epidermal structure mainly composed of secretory cells and support cells. Secretory cells produce the cement, which anchor the metamorphic larva to the substratum until the podia are developed. The relatedness between the composition of the adhesive material in the brachiolaria attachment complex and in the podia of adults was investigated by immunocytochemistry using antibodies raised against podial adhesive secretions of A. rubens. Type A secretory cells were the only immunolabelled cells indicating that their temporary adhesive shares common epitopes with the one of podia. The attachment pattern displayed by the individuals of A. rubens during the perimetamorphic period—temporary, permanent, temporary—is unique among marine non-vertebrate Metazoa.     

Observations on the moving colonies of the genus Tethya (Demospongia,Porifera)

Summary Observations on two species of sponges, Tethya seychellensis from the Red Sea, and T. aurantium from the Mediterranean Sea revealed that young colonies are able to detach from their sites of settlement and by means of filamentous podia, to move to other sites in the vicinity. These podia are 10–16 mm long extensions of the sponge body wall that bear an adhesive knob on their distal ends. After being attached, the contracting podia pull the spherical colonies of 2.0–3.0 cm in diameter, transporting them to a new site. EM observations showed that in the podia the matrix is rich in contractile myocytes, primary archaeocytes, nucleated archaeocytes and scleroblastic cells, each of which takes part in the moving ability of the podium. It was also shown that some of the archaeocytes go over a process of ripening within the podium and produce collagenic filaments deposited in the internal matrix.     

Characterization of the Adhesive from Cuvierian Tubules of the Sea Cucumber <Emphasis Type="Italic">Holothuria forskali</Emphasis> (Echinodermata,Holothuroidea)

Abstract Sea cucumbers possess a peculiar specialized defense system: the so-called Cuvierian tubules. The system is mobilized when the animal is mechanically stimulated, resulting in the discharge of a few white filaments, the tubules. Their great adhesivity, combined with their high tensile strength, allows Cuvierian tubules to entangle and immobilize potential predators. The cellular origin and composition of the Cuvierian tubule adhesive were investigated in the species Holothuria forskali by studying prints left on the substratum after mechanical detachment of the tubule. Polyclonal antibodies raised against tubule print material were used to locate the origin of tubule print constituents in the tubules. Extensive immunoreactivity was detected in the secretory granules of mesothelial granular cells, suggesting that their secretions make up the bulk of the adhesive material. Tubule print material consists of 60% proteins and 40% carbohydrates, a composition that is unique among the adhesive secretions of marine invertebrates. Although it is highly insoluble, a small fraction of this material can be extracted using denaturing buffers. Electrophoretic analysis of the extracts revealed that it contains about 10 proteins with apparent molecular masses ranging from 17 to 220 kDa and with closely related amino acid compositions, rich in acidic and in small side-chain amino acids. The adhesive from the Cuvierian tubules of H. forskali shares these characteristics with many marine bioadhesives and structural biomaterials.     

Ultrastructure of the tube foot sensory-secretory complex in Ophiocomina nigra (Echinodermata,Ophiuridea)

Summary The ultrastructure of the epidermal layer of both the oral and arm podia of the brittle star Ophiocomina nigra is described. Despite external differences, little variation occurs in their internal structure. The podial epidermis, which is overlain by a three-layered cuticle, consists of five cell types: support, mucous, sensory, adhesive secretory and monociliated neurosecretory-like cells. Areas of specialisation are superimposed on this basic plan. These comprise four cells forming cohesive units, made up of two adhesive secretory, one sensory and one monociliated neurosecretory-like cells. The two adhesive secretory cells may be identical or vary in the structure of their secretory packets. The sensory cells are of the normal type bearing a short cilium with a 9+2 microtubular arrangement. The monociliated neurosecretory-like cells contain many small dense vesicles and a short sub-cuticular cilium of irregular microtubular structure. Together, they appear to form a sensory-secretory complex which functions in adhesion both for feeding and locomotion. A system in which the secretion of the monociliated neurosecretory-like cell may control adhesive secretion is proposed.     

Leaf anatomy inCaesalpinia andHoffmannseggia (Leguminosae,Caesalpinioideae) with emphasis on secretory structures

Leaflets of 65 species ofCaesalpinia s.l. and seven species ofHoffmannseggia were studied in clearings supplemented by resin sections and scanning electron microscopy. Three types of secretory structure occurred among 46 species; in 43 species they were distributed mutually exclusively (external glands: 8 species; internal cavities: 5 species; idioblastic cells: 30 species); three other species each had two types. Species with secretory structures conform mostly to proposed subgenera and informal groups. Other unusual features were external glands with internal spaces, thickened walls or conspicuous localized wall thickenings in epidermal cells or mesophyll cells of certain species, and differentially stained epidermal cells surrounding stomata. Prismatic crystals predominate but druse crystals also occur.     

SECRETORY VESICLE FORMATION IN GLANDULAR TRICHOMES OF CANNABIS SATIVA (CANNABACEAE)

Formation of secretory vesicles in the noncellular secretory cavity of glandular trichomes of Cannabis saliva L. was examined by transmission electron microscopy. Two patterns of vesicle formation occurred during gland morphogenesis. 1) During initial phases of cavity formation small hyaline areas arose in the wall near the plasma membrane of the disc cell. Hyaline areas of elongated shape and different sizes were distributed throughout the wall and adjacent to the secretory cavity. Hyaline areas increased in size, some possibly fusing with others. These hyaline areas, possessing a membrane, moved into the cavity where they formed vesicles. As membraned vesicles they developed a more or less round shape and their contents became electron-dense. 2) During development of the secretory cavity and when abundant secretions were present in the disc cells, these secretions passed through the wall to accumulate as membraned vesicles of different sizes in the cavity. As secretions emerged from the wall, a membrane of wall origin delimited the secretory material from cavity contents. Vesicles released from the wall migrated in the secretory cavity and contacted the sheath where their contents permeated into the subcuticular wall as large or diffused quantities of secretions. In the subcuticular wall these secretions migrated to the wall–cuticle interface where they contributed to structural thickening of the cuticle. This study demonstrates that the secretory process in glands of Cannabis involves not only secretion of materials from the disc cell, but that the disc cell somehow packages these secretions into membraned vesicles outside the cell wall prior to deposition into the secretory cavity for subsequent structural development of the sheath.     

Adhesive mechanisms in cephalopods: a review

Abstract

Several genera of cephalopods (Nautilus, Sepia, Euprymna and Idiosepius) produce adhesive secretions, which are used for attachment to the substratum, for mating and to capture prey. These adhesive structures are located in different parts of the body, viz. in the digital tentacles (Nautilus), in the ventral surface of the mantle and fourth arm pair (Sepia), in the dorsal epidermis (Euprymna), or in the dorsal mantle side and partly on the fins (Idiosepius). Adhesion in Sepia is induced by suction of dermal structures on the mantle, while for Nautilus, Euprymna and Idiosepius adhesion is probably achieved by chemical substances. Histochemical studies indicate that in Nautilus and Idiosepius secretory cells that appear to be involved in adhesion stain for carbohydrates and protein, whilst in Euprymna only carbohydrates are detectable. De-adhesion is either achieved by muscle contraction of the tentacles and mantle (Nautilus and Sepia) or by secretion of substances (Euprymna). The de-adhesive mechanism used by Idiosepius remains unknown.     

Early Development of the Secretory Cavity of Peltate Glands in Humulus lupulus L. (Cannabaceae)

Early development of the secretory cavity of chemically fixed peltate glands in Humulus lupulus L. showed secretions with different densities, light, gray and dark, in the cytoplasm of disc cells and in the periplasmic space adjacent to the developing secretory cavity. Secretions were detected in the disc cell wall and subsequently in the developing secretory cavity under the subcuticular wall of the sheath. Light and gray secretions in the cavity possessed a membrane-like surface feature. Secretions were in contact with the irregular inner surface of the cuticle. Secretions contributed to the thickening of the cuticle, whereas the membrane-like surface feature contributed to a network of Cannabis striae distributed throughout the cuticle. This study supports an early development and organization of the secretory cavity in H. lupulus, parallel to those in Cannabis, and may represent common features for lipophilic glands in angiosperms.     

Non-respiratory podia of clypeasteroids (Echinodermata,Echinoides): II. Diversity

Summary There are five major types of non-respiratory podia in the Order Clypeasteroida: accessory, barrel-tipped, food groove, large food groove, and buccal. The anatomy of each type is intimately related to its function in the feeding mechanism of clypeasteroids. Accessory podia are found aborally and orally in some species, only aborally and ambitally in others. Accessory podia are largely sensory and manipulatory, but can be locomotory in the small fibulariids and juvenile sand dollars. Barrel-tipped podia have expanded disk muscles and connective tissue, and are usually found in two sizes, large and small. In species that have them they are usually restricted to the oral surface. These podia collect food and pass it towards the food grooves in the manner of a bucket brigade. Food groove podia are found only in species with food grooves. These podia are small, with reduced tip musculature and expanded secretory tissue for coating food with mucus. They transport food down the food grooves to the mouth. Large food groove podia are simply large versions of ordinary food groove podia. They help move the clumped food into the mouth area towards the buccals, and are found only in the Clypeasteridae and some scutellines. Buccal podia lack tip musculature, but possess tip support fibres and a single type of small secretory cell. They are sensory, and capable of manipulating particles into the mouth. Buccals are present in all families except the Clypeasteridae. Juvenile Echinarachnius less than 3 mm in diameter have only respiratory, accessory and buccal podia. Food groove and barrel-tipped podia start to differentiate from the accessories as the juvenile approaches a diameter of 4 to 5 mm. Clypeasteroid podial diversity increases the efficiency of the food collecting mechanism. The anatomy and distribution of podia on the oral surface of scutellines supports the fact that this surface is the prime food collecting area in all true sand dollars. The podia (not miliary spines) are the major source of mucus used during the feeding process and are the primary feeding appendages.     

Light and electron microscope investigations on the salivary glands of the slug,Agriolimax reticulatus (Müller)

Summary Ten cell types have been identified with the light microscope in the salivary glands ofA. reticulatus. Eight of these have also been observed with the electron microscope. A secretory cycle involving several cell types is absent. At least six different secretions are believed to be released from the glands. The pathways by which the secretions pass from the cells to the collecting ducts are outlined.Salivary duct epithelial cells have a characteristic ultrastructure which is similar to that found in ion and water transporting cells. It is proposed that the duct epithelial cells have a similar function.     

Micro- and nanostructure of the adhesive material secreted by the tube feet of the sea star Asterias rubens

To attach to underwater surfaces, sea stars rely on adhesive secretions produced by specialised organs, the tube feet. Adhesion is temporary and tube feet can also voluntarily become detached. The adhesive material is produced by two types of adhesive secretory cells located in the epidermis of the tube foot disc, and is deposited between the disc surface and the substratum. After detachment, this material remains on the substratum as a footprint. Using LM, SEM, and AFM, we described the fine structure of footprints deposited on various substrata by individuals of Asterias rubens. Ultrastructure of the adhesive layer of attached tube feet was also investigated using TEM. Whatever the method used, the adhesive material appeared as made up of globular nanostructures forming a meshwork deposited on a thin homogeneous film. This appearance did not differ according to whether the footprints were fixed or not, and whether they were observed hydrated or dry. TEM observations suggest that type 2 adhesive cells would be responsible for the release of the material constituting the homogeneous film whereas type 1 adhesive cells would produce the material forming the meshwork. This reticulated pattern would originate from the arrangement of the adhesive cell secretory pores on the disc surface.     

Cloning,Characterization, and Expression Levels of the <Emphasis Type="Italic">Nectin</Emphasis> Gene from the Tube Feet of the Sea Urchin <Emphasis Type="Italic">Paracentrotus Lividus</Emphasis>

Marine bioadhesives perform in ways that manmade products simply cannot match, especially in wet environments. Despite their technological potential, bioadhesive molecular mechanisms are still largely understudied, and sea urchin adhesion is no exception. These animals inhabit wave-swept shores, relying on specialized adhesive organs, tube feet, composed by an adhesive disc and a motile stem. The disc encloses a duo-gland adhesive system, producing adhesive and deadhesive secretions for strong reversible substratum attachment. The disclosure of sea urchin Paracentrotus lividus tube foot disc proteome led to the identification of a secreted adhesion protein, Nectin, never before reported in adult adhesive organs but, that given its adhesive function in eggs/embryos, was pointed out as a putative substratum adhesive protein in adults. To further understand Nectin involvement in sea urchin adhesion, Nectin cDNA was amplified for the first time from P. lividus adhesive organs, showing that not only the known Nectin mRNA, called Nectin-1 (GenBank AJ578435), is expressed in the adults tube feet but also a new mRNA sequence, called Nectin-2 (GenBank KT351732), differing in 15 missense nucleotide substitutions. Nectin genomic DNA was also obtained for the first time, indicating that both Nectin-1 and Nectin-2 derive from a single gene. In addition, expression analysis showed that both Nectins are overexpressed in tube feet discs, its expression being significantly higher in tube feet discs from sea urchins just after collection from the field relative to sea urchin from aquarium. These data further advocate for Nectin involvement in sea urchin reversible adhesion, suggesting that its expression might be regulated according to the hydrodynamic conditions.     

Fine structure of the epidermis in Gnathostomulida

Summary The fine structure of the epidermis in Haplognathia simplex, Haplognathia rosea, Pterognathia meixneri (Filospermoidea) and Gnathostomula paradoxa (Bursovaginoidea) has been investigated. The epidermis in the filospermoidean species is uniform, consisting of epidermal cells with a single locomotory cilium. The structure and development, including ciliogenesis, of these epidermal cells are described. In G. paradoxa additional epidermal elements have been found: mucous cells with a presumably apocrine secretion modus are scattered in a strip-like arrangement within the epidermis. Their deverlopment is separate from epidermal cells with locomotory function. Two further types of glandular cells with either a single cilium or a diplosome are located ventrally. It is assumed that they represent an adhesive system.Abbreviations (used in figures) ac accessory centriole - ap appendix of accessory centriole - ax axoneme - bb basal body - bf basal foot - bl basal lamina - c cilium - cA ciliary adhesive cell - ce centriole - cp ciliary pit - d diplosome - dy dictyosome - dA diplosomal adhesive cell - E epidermal cell with locomotory cilium, epidermis - ev epidermal vesicle (epitheliosome) - gv gland vesicle - m mitochondrion - ma microvillus of apical cell membrane - mp microvillus of ciliary pit - mv microvillus - n nucleus - ps prosecretory-vesicle - R receptor - r ciliary rootlet - rc caudal ciliary rootlet - rr rostral ciliary rootlert - sv secretory vesicle - v vesicle - v _i central vesicle of multivesicular body - v _o surrounding vesicle of multivesicular body - z cisternae     

Is the adhesive material secreted by sea urchin tube feet species‐specific?

Sea urchin adoral tube feet are highly specialized organs that have evolved to provide efficient attachment to the substratum. They consist of a disk and a stem that together form a functional unit. Tube foot disk tenacity (adhesive force per unit area) and stem mechanical properties (e.g., stiffness) vary between species but are apparently not correlated with sea urchin taxa or habitats. Moreover, ultrastructural studies of sea urchin disk epidermis pointed out differences in the internal organization of the adhesive secretory granules among species. This prompted us to look for interspecific variability in the composition of echinoid adhesive secretions, which could explain the observed variability in adhesive granule ultrastructure and disk tenacity. Antisera raised against the footprint material of Sphaerechinus granularis (S. granularis) were first used to locate the origin of adhesive footprint constituents in tube feet by taking advantage of the polyclonal character of the generated antibodies. Immunohistochemical assays showed that the antibodies specifically labeled the adhesive secretory cells of the disk epidermis in the tube feet of S. granularis. The antibodies were then used on tube foot histological sections from seven other sea urchin species to shed some light on the variability of their adhesive substances by looking for antibody cross‐reactivity. Surprisingly, no labeling was observed in any of the species tested. These results indicate that unlike the adhesive secretions of asteroids, those of echinoids do not share common epitopes on their constituents and thus would be “species‐specific.” In sea urchins, variations in the composition of adhesive secretions could therefore explain interspecific differences in disk tenacity and in adhesive granule ultrastructure. J. Morphol., 2011. © 2011 Wiley Periodicals, Inc.     

On the sites of secondary podia formation in a juvenile echinoid: growth of the body types in echinoderms

The growth of the adult echinoderm body is addressed here in the echinoid Holopneustes purpurescens in a study of the early development of the secondary podia along the five radial canals of the adult rudiment. At a stage when the first four secondary podia have formed along each radius oral to the primary podium, two podia are on one side of the radius and two are on the other side, all at a different distance from the primary podium. The pattern of the connexions of these secondary podia to the radial canals changes in successive radii in a manner similar to Lovén’s law for skeletal plates and matches the reported sequence in the times at which the first ambulacral skeletal plates form in the adult echinoid rudiment. A similar pattern is described for the reported origins of the secondary podia in apodid holothurians. A common plan for the growth of the body types is described for echinoids, asteroids, holothurians and concentricycloids. The five metameric series of secondary podia formed in echinoderms have a coelomic developmental origin like the single metameric series of somites formed in the axial structures of chordates.     

Cell lineage restrictions in the genital disc ofDrosophila revealed byMinute gynandromorphs

Summary The genital imaginal disc ofDrosophila differentiates the terminalia, i.e. the genitalia and analia, of both sexes. It represents a composite anlage, containing a female genital primordium, a male genital primordium and an anal primordium. In normal males and females, only one of the two genital primordia differentiates; the other is developmentally repressed. Therefore, cell-lineage relationships between the male and female genital primordia can only be studied in sexual mosaics which differentiate female and male cells. We producedMinute (M)non-Minute(M⁺) gynandromorphs and selected those with sexually mosaic terminalia for a cell-lineage analysis. In these mosaics, either the male (XO) or female (XX) cells wereM ⁺ and thus had a growth advantage. The differential growth rates served as a tool to detect clonal restrictions. In control gynandromorphs (M ⁺M ⁺), the amount of female genitalia differentiated was largely independent of the amount of male genitalia present. In contrast, male and female anal structures, as a rule, added up to one full set. The same was true for the experimentalMM ⁺ gynandromorphs, but the contribution ofXX andXO cells to mosaic terminalia changed drastically due toM ⁺ cells competing successfully against the more slowly growingM cells. Specific subsamples ofMM ⁺ gynandromorphs showed thatM cells in a non-mosaic primordium are shielded from cell competition taking place in the neighbouring mosaic primordium. We conclude that the three primordia of the genital disc represent developmental compartments. In the genital primordia, even developmentally repressedM ⁺ cells compete successfully against developmentally activeM cells.     

Adaptations to benthic development: functional morphology of the attachment complex of the brachiolaria larva in the sea star Asterina gibbosa

The asteroid Asterina gibbosa lives all its life in close relation to the sea bottom. Indeed, this sea star possesses an entirely benthic, lecithotrophic development. The embryos adhere to the substratum due to particular properties of their jelly coat, and hatching occurs directly at the brachiolaria stage. Brachiolariae have a hypertrophied, bilobed attachment complex comprising two asymmetrical brachiolar arms and a central adhesive disc. This study aims at describing the ultrastructure of the attachment complex and possible adaptations, at the cellular level, to benthic development. Immediately after hatching, early brachiolariae attach by the arms. All along the anterior side of each arm, the epidermis encloses several cell types, such as secretory cells of two types (A and B), support cells, and sensory cells. Like their equivalents in planktotrophic larvae, type A and B secretory cells are presumably involved in a duo-glandular system in which the former are adhesive and the latter de-adhesive in function. Unlike what is observed in planktotrophic larvae, the sensory cells are unspecialized and presumably not involved in substratum testing. During the larval period, the brachiolar arms progressively increase in size and the adhesive disc becomes more prominent. At the onset of metamorphosis, brachiolariae cement themselves strongly to the substratum with the adhesive disc. The disc contains two main cell types, support cells and secretory cells, the latter being responsible for the cement release. During this metamorphosis, the brachiolar arms regress while post-metamorphic structures grow considerably, especially the tube feet, which take over the role of attachment to the substratum. The end of this period corresponds to the complete regression of the external larval structures, which also coincides with the opening of the mouth. This sequence of stages, each possessing its own adhesive strategy, is common to all asteroid species having a benthic development. In A. gibbosa, morphological adaptations to this mode of development include the hypertrophic growth of the attachment complex, its bilobed shape forming an almost completely adhesive sole, and the regression of the sensory equipment.     

Endogenous Tumor Necrosis Factor α Unmasks the Binding Sites for N-Acetylglucosaminyl-(β1-4)-N-Acetylmuramyl-Alanyl-D-Isoglutamine on the Surface of Melanoma Cells

The surface of the melanoma BRO cells was shown to contain binding sites for N-acetylglucosaminyl-(1-4)-N-acetylmuramyl-alanyl-D-isoglutamine (GMDP). Their number (1500 ± 200 per cell) and affinity (K _d= 10 ± 1.2 nM) were determined. The occurrence of these sites was found to correlate with the ability of the melanoma cells to react in vitrowith GMDP by increasing the expression of melanoma-associated antigens (MAA). An increased number of the GMDP binding sites (5200 ± 500 per cell) was observed upon treating the melanoma BRO cells with tumor necrosis factor (TNF-). The mechanism of the TNF- action most likely involves the unmasking of GMDP binding sites, initially expressed on the cell surface, by activating the endogenous protease that hydrolyzes surface proteins, in particular, highly glycosylated LAMP-2 protein exposed on the melanoma cell surface.