Evolution des activités protéolytiques digestives chez les Jeunes Mulgilidae

Proteolytic activity in the stomach, pyloric caeca and intestine decreases with increasing size in the three fish species Mugil auratus, M. capito and M. saliens. Differences between these species are found mainly in the gastric proteolytic activity which appears to be related to diet. This activity is pronounced in M. saliens whose diet is mainly carnivorous. Comparison of regression lines relating gastric proteolytic activity to size reveals differences which distinguish M. auratus from both of the other species. Total proteolytic activity exhibits high variability depending on the types of diet.     

L'Intestin chez les Mugilidae (Poissons; Téléostéens) a différentes étapes de leur croissance I. Aspects morphologiques et histologiques

The intestine of Mugilidae (Pisces; Teleostei) at different growth stages. I. Morphological and histological aspects A morphological and histological study of the intestine of Mugilidae (Mugil cephalus, Liza aurata, Liza ramada and Liza saliens) has been carried out from the larval to the adult stages. The allometric relationship between length of intestine and standard length of fish are represented by regression lines correlated with species and kind of diet. S.E.M. observations on the intestinal mucosa surface show finger-like villi, as in Mammals. Histologically, the mucosa structure appears similar to that in others Teleosteans. The gobblet cells are scarce in the larval stages but very numerous in the juvenile stages; furthermore, they are more abundant in the posterior than the anterior part of the intestine (respectively 25 and 10%). Change in the feeding habits observed in young stages has no effect on the features of the intestine but notably increases its relative length.     

Caractérisation de quelques activités enzymatiques digestives chez Mugil capito en relation avec la taille

The activities of esterase 2C, esterase 14C, L-leucine aminopeptidase, α-glucosidase, alkaline and acid phosphatases of the stomach, the caeca and the gut of Mugil capito were examined by polyacrylamide gradient gel electrophoresis. Fishes of three sizes were compared: the smallest only showed esterase 2C and phosphatases activities. Zymograms for each size and each organ were examined and the molecular weights of the isozymes evaluated with an accuracy of 10,000 daltons. It was found that (a) the existence of some isozymes is dependent to the size and the organ; (b) some enzymes are found only in some parts of the digestive tract; (c) for any given organ, enzymatic activity differs from one isozyme to another; and (d) the digestive enzymatic activities differ for each organ considered and in different ways dependent on the size of the fish.     

L'Intestin chez les Mugilidae (Poissons Téléostéens) à différentes étapes de leur croissance: II. Aspects ultrastructuraux et cytophysiologiques

The Intestines of the Mugilidae (Pisces Teleostei) at different growth stages. II-Ultrastructural and cytophysiological aspects The ultrastructures and functions of the columnar cells of the intestinal epithelia are characterized, from the larva to the adult stage: major transformations of the endoplasmatic reticulum, passage of SER/RER from 1 to 3, noticeable encrease of Golgi activity, development of lamellar structures forming a “mitochondrial pump” together with the basal mitochondria, at all levels of the intestine. Localized mainly in the posterior region of the juvenil stages, pinocytosis of the alimentary proteins and the associated lytic processus extend in the adult to the anterior region. Lipid absorption takes place essentially in the anterior part, resulting at all stages of development in the presence of lipid particles in the SER and in the intercellular spaces, and in the adult only in rare free lipid droplets in the cytoplasma. Correlations are rare between the evolution of organelles and cellular inclusions observed during the growth and the diet.     

Evolution de quelques Enzymes Digestives chez le Jeune Mugil capito à Diverses Etapes de sa Croissance

Modifications in the digestive enzymic profile in three parts of the digestive tract (stomach, pyloric caecum and intestine) were studied during the first year of life of the teleost Mugil capito by the semi-quantitative APIZYM method. Higher enzymic activity was found int he pyloric caecum and intestine than in the stomach. Moreover, a decrease in protease activities appears during growth and is apparently due to adaptation to changes in diet.     

Simultaneous preparation of basolateral and brush-border membrane vesicles from sea bass intestinal epithelium

A method is described for simultaneous preparation of brush-border and basolateral sea bass enterocyte membranes using simple differential centrifugation and discontinuous sucrose gradient density centrifugation techniques. Basolateral membranes were purified with a Na+/K(+)-ATPase yield of about 11% of the original activity, with an enrichment factor of 12. The yield of maltase-glucoamylase, a specific marker of brush-border membranes, was also about 11% of the original activity, with 15-fold enrichment. The characteristics of these membrane preparations were determined. Electron microscopy analysis showed that these two membrane preparations were uniform in size and vesicular in nature. Orientation studies revealed that the luminal membrane vesicles were right-side out and 43% of the antiluminal membrane vesicles were sealed inside out. Investigation of D-glucose and L-leucine uptake showed that these two plasma membrane preparations retained their transport properties.     

Evidence and properties of digestive proteases in young mugilidae during the first year of life]

Proteolytic activity was observed in extracts from the digestive tract of Mugil auratus and Mugil capito; its maximum occurs at about pH 2 and 9. Activity in the acid range is mainly found in stomach extracts and the enzyme may be considered as similar to pepsin and cathepsins. In the alkaline range, the main activity is recorded in the region of the pyloric caeca. Activities of the trypsin, chymotrypsin, A and B carboxypeptidases and elastase type are found. The effects of pH and temperature on some activities are studied: optimal pH are about 2.6 and 3,4 with pepsin-like activity, between 8,1 and 8,5 with trypsin-like activity and between 7,8 and 8,5 with chymotrypsin-like activity; incubation optimal temperature (pH 2,2) is found between 35 degrees and 40 degrees.