Lipids in the skin of a cat-fish Heteropneustes fossilis (Bloch) (Heteropneustidae, Pisces). A histochemical investigation

Lipase from liver of seabass (Lates calcarifer): Characteristics and the use for defatting of fish skin

Lipase from liver of seabass (Lates calcarifer), with a molecular weight of 60kDa, was purified to homogeneity using ammonium sulfate precipitation and a series of chromatographies, including diethylaminoethyl sepharose (DEAE) and Sephadex G-75 size exclusion columns. The optimal pH and temperature were 8.0 and 50°C, respectively. Purified lipase had Michaelis-Menten constant (K_m) and catalytic constant (k_cat) of 0.30mM and 2.16s^-1, respectively, when p-nitrophenyl palmitate (p-NPP) was used as the substrate. When seabass skin was treated with crude lipase from seabass liver at various levels (0.15 and 0.30units/g dry skin) for 1-3h at 30°C, the skin treated with lipase at 0.30 units/g dry skin for 3h had the highest lipid removal (84.57%) with lower lipid distribution in skin. Efficacy in defatting was higher than when isopropanol was used. Thus, lipase from liver of seabass could be used to remove fat in fish skin.

Cutaneous biology and diseases of fish

The normal structure and function of the piscine integument reflects the adaptation of the organism to the physical, chemical, and biological properties of the aquatic environment, and the natural history of the organism. Because of the intimate contact of fish with the environment, cutaneous disease is relatively more common in fish than in terrestrial vertebrates and is one of the primary disease conditions presented to the aquatic animal practitioner. However, cutaneous lesions are generally nonspecific and may be indicative of disease that is restricted to the integument or a manifestation of systemic disease. Regardless, a gross and microscopic examination of the integument is simple to perform, but is highly diagnostic and should always be included in the routine diagnostic effort of the aquatic animal practitioner, especially since various ancillary diagnostic procedures are either not practical or lack predictive value in fish. The purpose of this article is to provide an overview of normal cutaneous biology prior to consideration of specific cutaneous diseases in fish.

Histochemical studies of acid proteoglycans and glycoproteins and activities of hydrolytic and oxidoreductive enzymes in the skin epidermis of the fish Blennius sanguinolentus pallas (Teleostei: Blenniidae)

In the epidermis of the fish Blennius sanguinolentus the histochemistry of complex carbohydrates and various oxidoreductases has been studied by means of a series of selected light microscopical techniques. The epidermis is endowed with three types of secretory cells namely, the mucous goblet cells, the superficial polygonal cells and the ionocytes, which provide protective functions in view of their involvement in the prevention of the skin epithelium from invading pathogens and in the osmoregulation processes respectively. The secretory substances of mucous goblet cells contain sulfated, carboxylated and neutral complex carbohydrates in addition to a glycoprotein with sialic acid terminal to galactose in its oligosaccharide chains. Activities of SDH, ICDH, MDH and G-6-PDH were studied, to elucidate some aspects of the correlated functions of the ionocytes which play a key role in the performance of the maintenance of the electrolyte pattern in the internal milieu of the skin. Differences in the intensity of various oxidoreductases are correlated with the extent of the activity of the epidermis for related to secretion of a mucous cover over the surface. Activity of the oxidoreductases is confined mainly to the basal and outer epidermal layers and this enzyme zonation is discussed with reference to the existence of the high turnover rate of the epithelial cells and both the proliferative and respiratory capabilities of the skin epithelium.