O. Cattani

Correlation between metallothionein and energy metabolism in sea bass, Dicentrarchus labrax, exposed to cadmium☆

Specimens of sea bass (Dicentrarchus labrax) were exposed to two different cadmium concentrations (0.5 and 5 μg Cd2+/ml seawater) for a period of 7 days. Cadmium accumulated in the tissues of D. labrax in the following order: kidney > liver > gills at both concentrations. Accumulation patterns in fish exposed to 0.5 μg Cd2+/ml seawater were different with respect to 5.0 μg Cd2+/ml seawater. At both Cd concentrations a similar stress situation occurred during the first 4 hr as noted by the depletion of glycogen stores and the increase in free glucose in the muscle; metallothionein was induced in the liver, but failed to bind all the cytosolic Cd, which was in part bound to high-molecular-weight ligands. Fish recovered from this initial stress situation within 24 hr as indicated by the increase in glycogen and the decrease of glucose. Long-term effects were clearly dependent upon metal concentration: at lower Cd exposure, metallothionein induction increased linearly with time and counteracted the toxic effect of the metal; on the other hand, when fish were exposed to 5.0 μg Cd2+/ml seawater a clear stress occurred at the end of the exposure, as indicated by the notable decrease of glycogen stores, the increase of free glucose, the decrease of AEC in the muscle and the increase of Cd bound to high-molecular-weight ligands in the liver.

Energy metabolism of the mussel, Mytilus galloprovincialis, during long-term anoxia

Abstract In the mussel, Mytilus galloprovincialis , the pattern of metabolic adaptations to long-term anoxia was clearly biphasic. The first phase (transition stage) lasted 24 hr and was characterized by the decrease of adenylate energy charge, the consumption of aspartate and the accumulation of succinate and alanine. The second phase (stationary stage) was characterized by the depletion of glycogen stores, the production of propionate, which was subsequently excreted into incubation water, and the metabolic depression. The ATP turnover rate was reduced by a factor of 3.9 from short-term anoxia to long-term anoxia.

Differential survival of Venus gallina and Scapharca inaequivalvis during anoxic stress: Covalent modification of phosphofructokinase and glycogen phosphorylase during anoxia

SummaryBiochemical mechanisms underlying anaerobiosis were assessed in two Mediterranean bivalve species, Scapharca inaequivalvis and Venus gallina, with widely differing tolerances for oxygen lack. These species displayed LT50 values for anoxic survival at 17–18°C of 17 and 4 d, respectively. Succinate and alanine were the major products of 24 h anaerobic metabolism in both species but only S. inaequivalvis further metabolized succinate to propionate. Both species reduced metabolic rate while anoxic but metabolic arrest was more pronounced in S. inaequivalvis. Calculated ATP turnover rate (MATP) during exposure to N2-bubbled seawater was only 4.51% of the aerobic rate in S. inaequivalvis but was 12.68% in V. gallina. To counteract a greater load of acid end products, V. gallina foot showed a significantly greater buffering capacity, 23.38±0.20 slykes, compared to 19.6±0.79 slykes in S. inaequivalvis. The two species also differed distinctly in the enzymatic regulation of anaerobiosis. In V. gallina anoxia exposure caused only a small change in PFK kinetic parameters (a decrease in Ka AMP) and had no effect on glycogen phosphorylase. By contrast, S. inaequivalvis foot showed a strong modification of enzyme properties in anoxia. The percentage of glycogen phosphorylase in the a form dropped significantly only in S. inaequivalvis. Other changes included alterations in the properties of PFK leading to a less active enzyme form in anoxia. Compared to the aerobic enzyme form, PFK from anoxic foot showed a reduced affinity for fructose-6-P (Km increased 2.4-fold), greater inhibition by ATP (I50 decreased 6.8-fold), and an increase in sensitivity to AMP activation (Ka decreased by 50%). These enzyme changes appear to be key to a glycolytic rate depression during anaerobiosis in S. inaequivalvis foot muscle.

Resistance of bivalves to anoxia as a response to pollution-induced environmental stress

The effect of environmental pollution stress factors on anoxic survival time was established in three bivalve molluscs (Mytilus edulis, Scapharca inaequivalvis and Venus gallina). In order to study relationships with energy status of the cell and ATP turnover rates the accumulation of fermentative end-products and changes in the glycogen, the adenylate phosphate and the phosphoarginine pool were also estimated. The response among the different species was not consistent. In contrast to Scapharca inaequivalvis, in Mytilus edulis and Venus gallina, accumulated cadmium reduced the tolerance to anoxic conditions. In Mytilus edulis this was accompanied with enhanced metabolic activity indicating a higher anaerobic ATP utilization rate. Additional evidence from literature shows that the anoxic survival response of mussels is a simple method to judge whether environmental variables might have perturbing effects on cellular processes which lead to reduced fitness.

Anoxic survival potential of bivalves: (arte)facts

The anoxic survival time of the bivalves Chamelea gallina, Cerastoderma edule and Scapharca inaequivalvis from two different ecosystems and differing anoxia tolerances was studied in static (closed) and flow-through systems. The antibiotics chloramphenicol, penicillin and polymyxin were added, and molybdate (specific inhibitor of the process of sulfate reduction). Survival in (near) anoxic seawater of Chamelea was studied in a static system by comparing untreated seawater with autoclaved seawater and untreated clams with clams incubated in well-aerated seawater, containing the broad-spectrum antibiotic chloramphenicol, prior to the anoxic survival test. With untreated clams and natural seawater (median mortality time 2.4 days) a decrease in pH and exponential accumulation of sulfide and ammonium was observed in the anoxic medium, indicating excessive growth of (sulfate reducing) bacteria. In sterilized seawater LT50 (2.1 days) was not significantly different and again considerable amounts of ammonium and sulfide accumulated. However, pre-treatment of clams with chloramphenicol resulted in an increase of LT50 (11.0 days) by approximately fivefold. Accumulation of ammonium and sulfide was retarded, but was finally even stronger than in the medium containing untreated clams. Median mortality times were 2.5 and 2.4 days for Chamelea and 2.7 and 2.9 days for Cerastoderma for static and flow-through incubations, respectively. Addition of chloramphenicol increased strongly survival time in both systems with corresponding values of 11.0 and 16.3 days for Chamelea, and 6.4 and 6.5 days for Cerastoderma. LT50 of Scapharca in anoxic seawater was 14.4 days. Chloramphenicol and penicillin increased median survival time to 28.5 and 28.7 days, respectively, whereas polymyxin displayed no effect (LT50=13.6 days). Molybdate added to artificial sulfate free seawater blocked biotic sulfide formation, but did not improve survival time (LT50=13.7 days). Overall the results indicate that proliferation of anaerobic pathogenic bacteria, firmly associated with the bivalves, is a main cause of death besides lack of oxygen. Bacterial damage is probably caused by injury of the tissues of the clams and not by the release of noxious compounds to the medium.

Energy metabolism during anaerobiosis and recovery in the posterior adductor muscle of the bivalve Scapharca inaequivalvis (Bruguiere)

Abstract 1. 1. In the posterior adductor muscle of Scapharca inaequivalvis both aspartate and glycogen were substrates for anaerobic metabolism. ATP and arginine phosphate only contributed to a small extent. Alanine and succinate were major end products, whereas opines were minor end products. Lactate production was not observed. 2. 2. The ATP turnover rate was reduced by a factor of 6 in the later anoxic period. Glycolysis and aspartate contributed about 90% either during the initial step or during the prolonged anoxia. 3. 3. Recovery of 24 hr was not enough for a complete restoration of energy reserves, whereas anaerobic end products were eliminated over this period. There was no strombine or lactate accumulation.

Superoxide dismutase in gastric adenocarcinoma: is it a clinical biomarker in the development of cancer?

Abstract Gastric cancer is the second most common cancer worldwide. The involvement of reactive oxygen species (ROS) in the pathogenesis of gastric malignancies is well known. Many human tumours have shown significant changes in the activity and expression of superoxide dismutase (SOD), which might be correlated with clinical–pathological parameters for the prognosis of human carcinoma. The aim of this study is the detection of MnSOD and CuZnSOD activity and their expression in gastric adenocarcinoma and healthy tissues. Gastric samples (adenocarcinoma and healthy tissues) harvested during endoscopy or resected during surgery were used to determine MnSOD and CuZnSOD activity and expression by spectrophotometric and Western blotting assays. The total SOD activity was significantly higher (p<0.05) in healthy mucosa with respect to gastric adenocarcinomas. No differences were found in MnSOD activity and, on the contrary, CuZnSOD activity was significantly lower (p<0.001) in cancer samples with respect to normal mucosa. The rate of MnSOD/CuZnSOD activity in adenocarcinoma was over ninefold higher than that registered in healthy tissues (p<0.05). Moreover, in adenocarcinoma MnSOD activity represented the 83% of total SOD with respect to healthy tissues where the ratio was 52% (p<0.001). On the contrary, in cancer tissues, CuZnSOD activity accounted for only 17% of the total SOD (p<0.001 if compared with the values recorded in normal mucosa). After immunoblotting, MnSOD was more expressed in adenocarcinoma with respect to normal mucosa (p<0.001), while CuZnSOD was similarly expressed in adenocarcinoma and healthy tissues. The SOD activity assay might provide a specific and sensitive method of analysis that allows the differentiation of healthy tissue from tumour tissue. The MnSOD to CuZnSOD activity ratio, and the ratio between these two isoforms and total SOD, presented in this preliminary study might be considered in the identification of cancerous from healthy control tissue.

Hydrocarbons, sterols and fatty acids in sea urchin (Paracentrotus lividus) of the adriatic sea

Aliphatic hydrocarbons, linear alkylbenzenes (LABs), sterols and fatty acids were determined in sea urchins (Paracentrotus lividus) of the Adriatic Sea in order to study their relationship with the trophic chain. The prevailing aliphatic hydrocarbons were squalene (40.3%) and n-C17:1 (24.9%), both of recent biological origin. LABS, on the other hand, are considered tracers of domestic wastes in marine environment. Among sterols, cholesterol (73.5%) and other Δ5-sterols are dominant, Fatty acids 16:0 (20.0%), 20:5ω3 (12.2%) and 14:0 (7.6%) were prevalent here as they are in other echinoid species analyzed by other authors. The distribution of these different compounds seems to be influenced by factors such as physiological needs, available diet and anthropogenic contamination.

Energy metabolism of bivalves at reduced oxygen tensions

This paper describes physiological and biochemical responses of three bivalved molluscs of the Northern Adriatic Sea to reduced ambient oxygen tension. Since the regular occurrence of exceptional algal blooms, the accidentally-imported «Indo-Pacific» blood clam Scapharca inaequivalvis is out-competing the native Venus gallina and Mytilus galloprovincialis. One reason for their differential ability to survive eutrophication with concomitant oxygen depletion is probably the exclusive presence of haemoglobin containing erythrocytes in the blood clam

Effects of different levels of dietary zinc on the gilthead,Sparus aurata during the growing season

Gilthead were fed three diets. Diet A was the control diet, whereas diets B and C were supplemented with 300 and 900 mg Zn/kg, respectively. Fish fed with diet C, at the end of the experiment, showed the lowest weight. Zinc concentrations presented the higher values in gills, liver, and kidney. Muscle and brain had the lower mean values and showed a tight control of zinc levels. These results reinforce the hypothesis that zinc in the CNS should be strictly controlled in order to maintain the functional role of the metal. Significant differences in tissue zinc concentrations were obtained between fish fed different amounts of zinc, the metal concentrations being higher in tissues of fish fed diet C. The tissue decrease of zinc, found at the end of the experiment, may depend on a lower feed consumption or on different zinc requirements during the cold season. These changes, even if not univocal among the three diets, may be associated with the life cycle of fish. Furthermore, copper concentrations were little affected by the different concentrations of zinc in the three diets; liver and kidney presented the highest concentrations; liver showed a significant decrease in copper content at the end of the experiment. We conclude that: zinc concentrations of the diet may affect the gilthead weights and the tissual metal content; and zinc concentrations in the diets, depending on the growth rate, may be varied depending on the season.