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Membrane potential depolarization due to electrogenic peptide transport activity was examined in eel ( Anguilla anguilla) intestinal brush-border membrane vesicles (BBMV) by monitoring the fluorescence quenching of the voltage-sensitive dye 3,3′-diethylthiadicarbocyanine iodide. Our experimental approach consisted of generating an internal negative membrane potential mimicking in vivo conditions and measuring membrane potential depolarization due to different extravesicular dipeptides. Peptide-dependent membrane potential depolarization was observed in both the presence and absence of extravesicular Na+ and was inhibited by diethylpyrocarbonate, which is consistent with the involvement of electrogenic, Na+-independent, H+-dependent peptide transport activity. Kinetic analysis indicated that peptide-dependent membrane potential depolarization is a saturable process ( Km,app ∼ 1.5 mmol L−1) and that within the 0.1–10 mmol L−1 peptide range a single carrier system is involved in the transport process. Our results suggest that a peptide transport activity, kinetically resembling the PepT1(Slc15A1)-type-mediated H+/peptide cotransport action, can be monitored in eel intestinal BBMV using an easy and inexpensive fluorescence assay. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate whether standard fish meal diets prepared with increasing levels of genetically modified (GM; 150 and 300 g kg−1) maize (event MON810®) as a starch source, showed any nutritional or physiological adverse effects on Atlantic salmon, Salmo salar L. postsmolt. The diets with low or high inclusions of GM maize and its near-isogenic parental line (nongenetically modified; nGM maize), were balanced with Suprex maize (Reference) to obtain compositional equivalency of diet starch, sugars and all other nutrients. Total starch level in all diets was 160 g kg−1. After 82 days of feeding, fish growth was high in all groups, however fish fed the GM maize showed slight but significant lower feed intake, which was followed by slight but significant lower specific growth rate and final body weights, compared with fish fed nGM maize, none of the groups varied significantly from fish fed the Reference diet. There was no variation in feed conversion ratios (FCR), protein and lipid efficiency ratios (PER and LER), or protein- and lipid-productive values (PPV and LPV) in this study. No significant effect of maize type was detected on apparent digestibility coefficients (ADC) of dry matter, protein or lipid. Hematological analysis and plasma nutrients varied within normal ranges for Atlantic salmon in all diet groups, except for somewhat elevated aspartate aminotransferase (ASAT) values in all groups. Hepatosomatic index (HSI) with values ranging from 1.37 to 1.60, was significantly higher for the high GM maize group compared with the high nGM maize group but not when compared with the Reference diet group. Lowered spleen (SSI) and head-kidney somatic indices (H-KSI) were registered when fed GM compared with nGM maize, the Reference treatment was however, equal to both. Distal intestine somatic index (DISI) was significantly higher for GM maize-fed fish compared with nGM maize-fed fish, but not significantly different from the Reference diet group. Histological evaluation of the mid- and distal intestine, liver, spleen and head-kidney did not reveal any diet-related morphological changes. Maltase activities in the mid- and distal intestinal tissue homogenates were affected by diet, the fish fed high GM maize having higher activities compared with high nGM maize-fed fish. Leucine aminopeptidase (LAP) and alkaline phosphatase (AP) activities were not affected by diet. Sodium-dependentd-glucose uptake in brush border membrane vesicles (BBMV) isolated from pyloric caeca of fish fed high GM maize was significantly higher than that found in fish fed the analogous diet with high nGM maize. Based on the present findings, the conclusions made are: Atlantic salmon smolts fed GM maize (event MON810®), its near-isogenic parental line and suprex maize (Reference diet), all resulted in high growth rates, ADC and feed utilization. Health, when evaluated by means of mortality (low), normal ranges of blood and plasma parameters, except somewhat elevated ASAT values and minor variations in organ sizes, were considered good in all diet groups. The changes in the glucose transport mechanism and intestinal maltase enzyme activity in the gastrointestinal tract warrant further studies. [ABSTRACT FROM AUTHOR]

The pharmacokinetic properties of cephalexin were studied in sea bream (mean weight 77 g), Sparus aurata (L.) after a single intraperitoneal injection (200 mg kg-1). Pharmacokinetic analysis of the serum concentrations vs time points obtained was performed using non-compartmental analysis and a compartmental pharmacokinetic model approach. In the latter case, a two-compartment open model with a lag time gave the best fitting. The maximum peak serum concentration was 5.018 mg ml-1 kg-1 1 h post-treatment. The area under the curve (AUC) cephalexin was 17.394 mg·h kg-1 and the elimination half-life of 1.83 h. [ABSTRACT FROM AUTHOR]

H[sup +]/peptide cotransport was studied in brush-border membrane vesicles (BBMV) from the intestine of the haemoglobinless Antarctic teleost Chionodraco hamatus by monitoring peptide-dependent intravesicular acidification with the pH-sensitive dye Acridine Orange. Diethylpyrocarbonate-inhibited intravesicular acidification was specifically achieved in the presence of extravesicular glycyl-L-proline (Gly-L-Pro) as well as of glycyl-L-alanine (Gly-L-Ala) and D-phenylalanyl-L-alanine (D-Phe-L-Ala). H[sup +]/Gly-L-Pro cotransport displayed saturable kinetics, involving a single carrier system with an apparent substrate affinity (K[sub m,app]) of 0.806±0.161 mmol l[sup -1]. Using degenerated primers from eel and human (PepT1) transporter sequence, a reverse transcription-polymerase chain reaction (RT-PCR) signal was detected in C. hamatus intestine. RT-PCR paralleled kinetic analysis, confirming the hypothesis of the existence of a PepT1-type transport system in the brush-border membranes of icefish intestine. Functional expression of H[sup +]/peptide cotransport was successfully performed in Xenopus laevis oocytes after injection of poly(A)[sup +] RNA (mRNA) isolated from icefish intestinal mucosa. Injection of mRNA stimulated DPhe-L-Ala uptake in a dose-dependent manner and an excess of glycyl-L-glutamine inhibited this transport. H[sup +]/peptide cotransport in the Antarctic teleost BBMV exhibited a marked difference in temperature optimum with respect to the temperate teleost Anguilla anguiila, the maximal activity rate occurring at approximately 0°C for the former and 25°C for the latter. Temperature dependence of icefish and eel intestinal mRNAstimulated uptake in the heterologous system (oocytes) was comparable. [ABSTRACT FROM AUTHOR]

Examines carbonic anhydrase (CA) activity and distribution in blood gills, intestine and kidney of the hemoglobinless teleost Chionodraco hamatus with Trematomus bernacchii. Analysis of the highest CA activity; Molecular masses of CA isoforms; Presence of a different branchial systolic CA in the red-blooded teleosts.

The enzymatic activity (expressed as milliunits per milligram total proteins) of three intestinal brush-border membrane enzymes, leucine aminopeptidase, alkaline phosphatase and maltase, measured over a range of temperatures between 1.5 and 37 °C, has been found to be much higher in the Antarctic fish Pagothenia bernacchii than in the temperate fish Anguilla anguilla. To explain this experimental observation the apparent Michaelis-Menten constant, the maximal velocity, the activation energy values and the thermal stability of these three enzymes were measured. The apparent Michaelis-Menten constant values of leucine amino peptidase and alkaline phosphatase were different in the intestine mucosal homogenate of the two fish at each measured temperature (from a minimum of 2.5 to a maximum of 37 °C). However, the values found at 2.5 °C for the Antarctic species and 15 °C for the eel where comparable. Furthermore, its value was unchanged in eel intestine apical membranes, both in the presence and without enzyme lipid microenvironment. While the maximal enzymatic activities of the leucine aminopeptidase and maltase did not decrease without their enzyme lipid microenvironment, produced by treatment with Triton X-100, the impairment of alkaline phosphatase maximal activity cannot be significantly differentiated from a non-specific inhibitory effect of the detergent. The activation energy values of leucine amino peptidase, alkaline phosphatase and maltase were lower in the Antarctic fish (11.7, 5.6 and 11.8 kcal·mol, respectively) than in the eel (13.6, 7.6 and 13.1 kcal·mol, respectively). The thermal stability of alkaline phosphatase and maltase is different in Pagothenia bernacchii and Anguilla anguilla intestinal homogenate. [ABSTRACT FROM AUTHOR]

Examines the Na+-D-glucose cotransport in the Antarctic fish Trematomus bernacchii by brush-border membrane vesicles (BBMV). Enzymatic characterization of BBMs isolated from T. bernacchii intestine; Temperature dependence in Anguial anguilla and T. bernacchii intestinal BBMV; Effect of electrical membrane potential on D-glucose uptake.