Eel Skin Research Articles

海洋生命科学における糖鎖生物学・糖鎖工学 魚類体表面粘質物の生体防御における役割 ウナギシアル酸含有糖タンパク質の構造と機能

海洋生命科学における糖鎖生物学・糖鎖工学 魚類体表面粘質物の生体防御における役割 ウナギシアル酸含有糖タンパク質の構造と機能

Melanin concentrating hormone (MCH): Synthesis and bioactivity studies of MCH fragment analogues

Nineteen analogues of melanin concentrating hormone (MCH) were synthesized and tested for their skin-lightening activities in the in vitro eel skin ( Synbranchus marmoratus) bioassay. All the analogues synthesized were fragments of the native sequence: Asp-Thr-Met-Arg- Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys -Trp-Glu-Val with sequential elimination of substituents from both the carboxy- and amino-termini. All the analogues that contained trytophan in position 15 were found to be full agonists and equipotent to MCH. In the absence of Trp 15, full agonist activity was maintained but potency was reduced ten-fold or more. The minimal fragment analogue possessing equipotency to the parent peptide, MCH, was the MCH(5–15) sequence. These observations coupled with results from work reported previously by our laboratories suggest the importance of the Trp 15 residue for interaction with the MCH receptor in this assay system.

Free amino acid content in the skin mucus of yellow and silver eel, Angvilla angvilla l

1. 1. Free amino acid contents in skin mucus extracts were analysed in sexually undinerentiated yellow eels, female yellow eels and male and female silver eels trapped at the same time from the same freshwater location. 2. 2. Total free amino acid contents in skin mucus were similar in the three groups of sexually differentiated eels (16.2–18.2μM/g dry weight). In sexually undinerentiated yellow eels, total content was higher (39.6μM/g dry weight). 3. 3. Free amino acid composition of skin mucus from male and female silver eels were similar. Compared with the two groups of yellow eels, main differences were found in taurine and non-essential amino acid relative contents. 4. 4. Taurine, glycine and alanine concentrations in skin mucus decreased as the level of sexual maturity of the eel increased. 5. 5. Possible influences of nutritional and hormonal factors on the free amino acid content of eel skin mucus are discussed. Potential consequences in osmoregulatory processes and intraspecific chemocommunication of the eel are also considered.

Histochemical localization of .BETA.-N-acetylhexosaminidase in the epidermis of eel.

To elucidate the origin of β-N-acetylhexosaminidase which had been found in the external mucous materials of varlous fishes, histochemical detection of β-N-acetylhexosaminidase activlty in the epidermis of eel was attempted using naphthol AS-BI N-acetyl, β-D-glucosaminide as sub-strafe and hexazonium pararosanilin as capture reagent. Besides, the structure of eel skin was observed histochemlcally by staining with periodate-Schiff reagent and toluidine blue. β-N-Acetylhexosaminidase activity was demonstrated as red-stained granules around the mature goblet cells in the upper layer of the epidermis. From the fact that the cell membrane in the epidermis was stained with periodate-Schiff reagent and toluidine blue, the membrane was revealed to con-tain carbohydrate components, presumably complex carbohydrates. From the above findings, it was assumed that β-N-acetylhexosaminidase might be involved in catabolic collapse of the super-ficial cells of the epidermis.

Neuron-specific enolase and serotonin in the Merkel cells of conger-eel (Conger conger) epidermis. An immunohistochemical study.

Immunocytochemical techniques were used to investigate the distribution and co-localization of neuron-specific enolase (NSE) and serotonin (5-HT) in the skin of the conger eel, Conger conger. NSE and 5-HT immunoreactivity were found in Merkel cells; these cells were also identified at the electron-microscope level by the presence of characteristic granules and their association with an intraepithelial nerve ending. For the first time, it was demonstrated that Merkel-cell granules of vertebrate skin exhibit an immunoreaction with 5-HT. The production of amines may indicate that the Merkel cells of C. conger have both secretory capabilities and transduction functions. However, immunocytochemical investigation of the synaptic zones at the electron microscope level will be necessary to confirm this hypothesis. The present histochemical results suggest that NSE and 5-HT may be marker substances for Merkel cells, and that immunocytochemistry is a useful tool for the light-microscopic localization of these cells.

The histochemistry of urea-unmasked glycosaminoglycans in the skin of the eel, Anguilla japonica.

In the connective tissues of the dermis and subcutis of the eel skin, the histochemistry of urea-unmasked glycosaminoglycans has been studied by means of combined staining and enzyme digestion procedures. The staining procedures employed were alcian blue (AB) pH 1.0, AB pH 2.5, aldehyde fuchsin (AF), periodic acid-Schiff (PAS), AB pH 2.5-PAS, high iron diamine (HID) and low iron diamine (LID) methods, whereas the enzymes used were Streptomyces and testicular hyaluronidases, chondroitinases ABC and AC and keratanase. The results obtained have shown that a substantial amount of dermatan sulfate and a relatively small amount of hyaluronic acid, chondroitin, chondroitin sulfate A and/or C were the glycosaminoglycans involved in the connective tissues of the eel skin and that the tissues were devoid of keratan sulfate.

Sustained branchial apnea in the Australian short‐finned eel, Anguilla australis

Branchial and cutaneous O2 uptake as well as branchial ventilatory stroke volume and frequency were measured by twin-chamber respirometry in conscious unoperated eels (Anguilla australis) at 20 degrees C. The branchial ventilatory pattern comprised alternating periods of apnea and eupnea, together constituting a "Standard Breathing Cycle" (SBC = 1 apneic period plus the ensuing period of eupnea). SBC time in 17 eels averaged 15.5 min of which only 23% was devoted to eupnea. Reduction of the PO2 of inspired water from 155 to 80 torr significantly increased the proportion of time devoted to eupnea to 49% of SBC time without significantly changing SBC time. Absolute cutaneous O2 uptake (5.8 ml O2 X h-1 X kg-1) was largely independent of the frequency or occurrence of eupnea, with the relative contribution of the skin to total O2 uptake averaging 47%. The histological appearance of the skin in A. australis is very similar to that described in A. anguilla: eel skin is only poorly vascularized. It was concluded that the skin may contribute to O2 requirements other than its own, and that this adaptation is a consequence of the unusual intermittent pattern of gill ventilation.

Sialic acid-containing glycoprotein in the external mucus of eel, Anguilla japonica TEMMINCK et SCHLEGEL. V. Structure of disaccharide from eel skin mucous glycoprotein and its linkage to protein moiety.

The purpose of this study was to elucidate the structure of disaccharide and the nature of its linkage to protein moiety of sialic acid-containing glycoprotein (SA-glycoprotein) isolated from eel skin mucus. The disaccharide of SA-glycoprotein was identified as N-acetylneuraminyl-(α, 2→6)-N-acetyl-galactosamine by periodate oxidation, analysis of the SMITH degradation product, and susceptibility to neuraminidase. The analysis of the sialic acid-containing glycopeptide which had been extensively digested with Pronase P showed that threonine and serine residues Were the only identifiable acceptors to the disaccharide units of eel SA-glycoprotein, indicating that the disaccharide units are O-glycosidically linked to the hydroxyl amino acids such as threonine and serine residues of SA-glycoprotein. This is the first, fish skin mucous glycoprotein which was elucidated concerning the structure of the carbohydrate unit and the carbohydrate-protein linkage. The function of eel SA-glycoprotein is also discussed.

MECHANICAL PROPERTIES AND LOCOMOTOR FUNCTIONS OF EEL SKIN

1. The skin of the American eel Anguilla rostrata is composed largely of a crossed-helical array of fibers, believed to be collagen, that are oriented at an angle of 45° with the long axis of the fish. Uniaxial and biaxial tension testing of eel skin was used to assess the role of the collagen fibers in the locomotor functions of the skin.2. The elastic modulus of skin stressed in the circumferential direction of the fish is 14.6 MN/m2 while that of skin stressed in the longitudinal direction is 3.5 MN/m2, thus eel skin is an order of magnitude stiffer in the circumferential than in the longitudinal direction. The skin is stiffest in the direction of the fibers, having an elastic modulus of 0.16 GN/m2 in this direction. Within the range of in vivo extensions the behavior of skin stressed in the longitudinal direction is similar to that of a model consisting of continuous crossed-fibers, while that of skin stressed in the circumferential direction is not.3. The mechanical behavior of the skin indicates that the skin may act as an external tendon, transmitting forces arising in the axial musculature down the length of the fish to the tail.4. The collagen fibers within the skin may play an important role in torsion resistance when the eel executes its peculiar "corkscrew" motion.

The mechanical properties and locomotory functions of eel skin

The mechanical properties and locomotory functions of eel skin

Himasthla quissetensis: Induced in vitro encystment of cercaria and ultrastructure of the cyst

Himasthla quissetensis cercariae were induced to encyst in solutions of casein hydrolysate, sodium glutamate, lysine, arginine, glucose, α-methylglucoside, 3-0-methylglucose, glucosamine, gluconate, galactose, xylose, cellobiose, maltose, clam mucus, and diffusates from bluegill and eel skin. The approximately ellipsoidal cyst is composed of an outer homogeneous layer formed by granules released from the tegument and an inner laminated layer formed by scrolled rods originating in subtegumental cell bodies. Encysted metacercariae were infective to fledgling seagulls. Cercariae of Leopcreadium setiferoides, Cryptocotyle lingua, and Parorchis acanthus could not be induced to encyst in vitro by addition of casein hydrolysate.

The sweat gland as a mucous gland.

Human crude sweat and sweat from a rhesus monkey (<i>Macaca mulatta</i>), obtained from the skin after thermal stimulation, were compared with human saliva and skin mucus from the frog (<i>Rana temporaria</i>) and eel (<i>Anguilla</i>). Mucin from all samples contained sialic acid and small amounts of lipids and protein; the polysaccharide part was essentially sulfated and contained but little hexuronic acid and hexosamine. Hydrolysed mucin fractions from all materials showed a similar amino acid composition. The skin mucins differed from other mucins in amino acid composition by the absence of threonine. Human crude sweat from the chest contained acid phosphatase, monkey sweat acid and alkaline phosphatase, frog skin mucus alkaline phosphatase and eel skin mucus acid phosphatase. Human axillar crude sweat showed a considerable alkaline phosphatase activity in addition to a stronger acid phosphatase activity than that from the chest. In atopic dermatitis no difference appeared in sialic acid content with a control group and a difference in protein content of mucin was unlikely. In this disease the significantly larger variability in free phosphate content was presumably from intra-cellular origin and that in the results of a reaction employing sulfite and heptazine indicated the importance of an investigation into lipids, containing carbonyl groups, in skin mucin.

<i>Aeromonas ljquefaciens</i>の病原性に関する研究-II

The 50, 000×g centrifugal supernatant of sonicated cell suspension of A. liquefaciens strain Y-62 was gel filtered on Sephadex G-100 column. Factors causing the death of mouse and guinea pig, hemorrhage to the guinea pig skin passed through Sephadex gel without disparsing, while hemorrhage and necrosis in the eel skin and necrosis in the guinea pig skin were disparsed in Sephadex gel and these activities were not separable. These indicate that the sonic extract of the organisms contained at least 2 different toxic substances.

VIII. The process of secretion in the skin of the common eel

We owe to Leydig (1) the first demonstration that a secretory process is a possibility for the skin of the Fish. In some twelve genera he described the occurrence of specialized cells in the epidermis, to which he gave the common name of “Schleim-zellen,” though subsequent research has shown that several varieties of structure were included in this generic term. Kölliker (2) in 1860, in an investigation of the skins of Myxine and Petromyzon , differentiated two cell-forms. Observing the “thread bodies” of the mucous sacs of Myxine , first clearly described by Johannes Müller (3), he recognized their cellular nature, and found that the epidermis held similar, though less complex cells, from whose contents also, by appropriate treatment, a thread could be obtained. To these epidermic cells of Myxine the name “Fadenzellen” was applied. In addition, clear or finely granular cells, termed “Schleimzellen,” were described.

III. The process of secretion in the skin of the common eel

Leydig, more than forty years ago, demonstrated the possibility of a secretory process in the skins of Fish by the discovery in the epidermis of some twelve genera, of specialised cells to which the name of “ schleimzellen ” was given. Since then Kolliker, Max Schultze, F. E. Schulze, Foettinger, List, Leydig himself, and others have extended our knowledge of the anatomical secreting elements of the epidermis, and shown that in many instances it is extremely probable that several varieties of such structures exist.

Further Observations on the Electromotive Properties of the Skin of the Common Eel

Further Observations on the Electromotive Properties of the Skin of the Common Eel

IV. The electromotive properties of the skin of the common eel

Hermann (1) has investigated the electromotive properties of the skins of Fish. His object in so doing was to attempt to determine, by the employment for experiment of a skin usually credited with being bereft of glands, whether the marked “current of rest” exhibited by the skins of Amphibia is with greater probability to be ascribed to glandular processes in accordance with the opinion of du Bois Reymond (2), or whether the phenomena are not explained with greater simplicity upon the principles of his own ‘Alterations-Theorie.’ Du Bois failed to obtain evidence of a “current of rest” in the four kinds of Fish with which he worked (Eel, Tench, Pike, and Perch), a fact, which taken in conjunction with the absence of “glands” satisfied him that in the richly glandular Amphibian skin the source of the E. M. F. must lie in the secreting structures. Hermann himself, previous to his examination of the skins of Fish, shared to some extent the opinion of du Bois, for in a paper published in 1878 (3), he inclines to the idea, that preparatory processes of glandular origin are the cause of the E. M. F. of the current of rest in the skin of the Frog, but also advances the supposition of a possible contribution from epithelial action at the surface. Finally, as is well known, Hermann demonstrated the presence of an ingoing current of rest in the skins of some ten genera of Fish, but found that its E. M. F. was far less than that exhibited by the Amphibian skin. After noting that substances, the application of which destroys the current of rest in Amphibian skin, cannot be traced microscopically beyond the upper layers of epidermic cells, and recalling the fact that an electromotive excitatory change was demonstrated by Bach and Oehler (4), in the skin of the Frog, after complete removal of the current of rest, by the action of corrosive sublimate applied to the outer surface, Hermann concludes that the E. M. F. of the current of rest, and that of the current of action are of different origin. In speaking of the origin of the current of rest, he makes the following statement, upon the strength of his demonstration of such a current in the “non-glandular” skins of Fish, “dass nicht, oder nicht in erster Linie, die Driisen, sondern die Epithelschicht, der Sitz der elektromotorischen Haut-wirkung ist.” Finally he bases his explanation of the source of the E. M. F. of the current of rest of the skins of both Amphibians and Fish upon the axioms of the “Alterations-Theorie.” According to this hypothesis, the processes of dying or excitation in the continuity of protoplasm cause the more altered parts to be negative electrically to the less altered, so Hermann says “Nun haben wir aber zunächst in alien verhornenden Epithelgebilden eine dem Absterben völlig analoge Alteration, welche von aussen nach innen fortschreitet (und durch den Nachwuchs compensirt wird), nämlich die Verhornung.” Thus in the case of the Amphibian the keratinized superficial cells of the epidermis are supposed to form a demarcation surface whose electrical sign is negative to that of the deeper less altered portions of the skin tissue. Analogous to the “keratin-metamorphose” of protoplasm stands in this connection a “mucin-metamorphose,” and Hermann remarks “Am Aal und an der Trüsche kann man direct sehen, wie die äusseren Zellenden unter Mucinbildung zu Grunde gehen.”

III. The electromotive properties of the skin of the common eel

1. The assumption that the E. M. F. of the current of rest of the skin of the Fish is entirely due to mucin-metamorphosis, and that it is not possible to attribute it to the presence of glandular elements is negatived, in the case of the Eel, by the absence of any such mucinous change in the superficial epidermic cells and by the presence of abund­ance of secretory cells throughout the structure. 2. The existence of considerable differences of potential between two contacts upon the outer surface of the skin, and the fact that such E. M. F. is capable of excitatory augmentation upon mechanical stimulation, coincides with the assumption that the E. M. F. of the current of rest is the outcome of glandular processes of variable activity and is not compatible with the theory of origin of the E. M. F. in mucin-metamorphosis.