Attilio Arillo

Ammonia toxicity mechanism in fish: studies on rainbow trout (Salmo gairdneri Rich).

Abstract Salmo gairdneri specimens were exposed for 4–48 hr to various environmental un-ionized ammonia (UIA) concentrations. In the brain of NH3-treated trout glutamate, GABA, total sugars, ATP, NADH, and succinate decrease, while tissue NH3 content, glutamine, and lactate increase. In the liver total sugars, succinate, and lactate decrease, while tissue NH3, glutamine, and the taurine/glycine ratio increase. Such variations depend upon exposure time and environmental UIA level. Ammonia toxicity mechanism in fish is discussed and compared with the one proposed in mammals. Further data obtained from overturned specimens suggest that in these animals a cerebral hypoxic phenomenon also occurs.

Metabolic integration between symbiotic cyanobacteria and sponges: a possible mechanism

Metabolic relationships between symbiotic cyanobacteria and host sponge have been investigated in the marine species Chondrilla nucula and Petrosia ficiformis (collected in the Ligurian Sea in 1992). DNA, RNA, total protein, cytosolic protein, total sugar, cytosolic sugar, total lipid, nonprotein sulfhydryl groups, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were assayed in cortex-free sponge tissue, where cyanobacteria are all but absent. For both species, biochemical parameters were determined in specimens living in illuminated habitats and in dark caves, where sponges are virtually aposymbiotic for cyanobacteria. As C. nucula is unable to colonize dark sites, specimens of this species were artificially transferred to a cave and maintained in dark conditions for 6 mo. Results showed that in the absence of light (i.e., in the absence of cyanobacteria) C. nucula undergo metabolic collapse and thiol depletion. In contrast, P. ficiformis activates heterotrophic metabolism and mechanisms which balance the loss of cell reducing power. This suggests that cyanobacteria effectively participate in controlling the redox potential of the host cells by the transfer of reducing equivalents. Only P. ficiformis is capable of counteracting, by means of heterotrophic metabolism, the loss of the contribution from symbionts which is caused by dark conditions. This explains the differences in the ecological requirements of the two species. Because cyanobacterial symbionts release fixed carbon in the form of glycerol and other small organic phosphate (Wilkinson 1979), a model based on the glycerol 3-phosphate shuttle (typically occurring in chloroplasts and mitochondria) is suggested. The mechanism proposed appears to be an ancient biochemical adaptation which arose among ancestral symbiotic systems, and further developed in the relationships between endosymbiotic organelles and cytoplasm.

Nitrite bioaccumulation in Salmo gairdneri rich. and hematological consequences

Abstract Salmo gairdneri Rich. exposed to 450 μg/l (NO 2 N) of environmental nitrite, and examined after various periods of treatment, possess methemoglobin levels neither correlatable to their physiological conditions, nor proportional to their hematic nitrite concentration. Also, functional hemoglobin content (total Hb minus metHb) can be connected to a physiological state only in the early stages of intoxication. Nitrite accumulates in blood and tissues of fish to a surprisingly high extent (up to 60 times the environmental concentration) against increasing concentration gradients. The nitrite concentration in blood seems to be linked to exposure time more than to physiological conditions, while in the liver and brain of treated specimens, much greater differences exist between apparently unstressed animals and torpid, unreactive trout. Further evidence is given, therefore, that death following acute intoxication depends on nitrite toxic action in vital organs rather than on methemoglobinemia.

Quality assessment of bed sediments of the Po River (Italy).

Comprehensive and contemporary evaluations of physical, chemical and toxicological endpoints have been performed on bed sediments of the Po River, the major Italian watercourse. Two extensive sampling campaigns were conducted in summer and winter low-flow conditions. Composite sediment samples were collected from ten reaches of the main river: the first was located in the upper region (ambient control), and the others downstream of the confluences of nine principal tributaries. The two sampling programs were paralleled by contemporary investigations on the macroinvertebrate community. The particle-size composition along the Po River showed a relatively uniform distribution of fine sand, a progressive downstream decrease of coarse sands and a corresponding increase of fine materials. The levels of polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), extractable organo halides (EOX), Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in sediment fine particles (< 63 microm), and showed marked changes across the ten river reaches. Their longitudinal trends, as those of organic carbon and total nitrogen, were very similar and largely independent of the survey season. Sediment quality benchmarks were used to evaluate sediment chemistry, and, although the overall level of contamination was from moderate to low, the reaches located downstream of the tributaries Dora Riparia, Dora Baltea, Lambro and Oglio were considered to be at risk. Sediments were tested for toxicity on Oncorhynchus mykiss, Ceriodaphnia dubia, Raphidocelis subcapitata and Vibrio fischeri. The toxicity tests were conducted both with sediment extracts and whole samples. Sediment extracts showed toxic potentials that were consistent with the spatial distribution of contaminants. Whole-sediment toxicity showed moderate/low effects which also included false positives and negatives. Alterations of the macroinvertebrate community were found for many kilometers downstream of Dora Riparia, and with a seasonal dependence, also in other reaches of the Italian river. Principal component analysis (PCA) was used to describe the longitudinal and temporal changes of the Po River, and allowed the selection of the most useful and discriminating indicators.

Parasitic diatoms inside antarctic sponges.

Antarctic sponges may host large populations of planktonic and benthic diatoms. After settling on the sponge, these diatoms enter its body through pinacocytes (1) and form, there, large mono- or pauci-specific assemblages. Yet the total amount of carbohydrates in the invaded sponge tissue is inversely correlated with that of chlorophyll-a. We suggest, therefore, that endobiont diatoms utilize the products of the metabolism of their host as an energy source. This is the first evidence indicating that an endobiotic autotrophic organism may parasitize its animal host. Moreover, this unusual symbiotic behavior could be a successful strategy that allows the diatom to survive in darkness.

ENHANCED LIVER METABOLISM OF MUTAGENS AND CARCINOGENS IN FISH LIVING IN POLLUTED SEAWATER

Specimens of the seawater fish annular seabream (Diplodus annularis) were caught from a polluted harbor area and from a clean reference area. Seawater concentrates and fish-muscle extracts were not mutagenic in the Salmonella reversion test. Liver preparations of fish from the 2 sources were comparatively assayed for microsomal mixed-function oxidases and cytosolic biochemical parameters, as well as for the ability of S12 fractions to activate promutagens or to detoxify direct-acting mutagens. A shift of the cytochrome P-450 peak from 450.3 to 448.5 was accompanied by a 4.5-fold increase in arylhydrocarbon hydroxylase activity in fish living in the polluted environment. At the same time, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were doubled in the cytosol of the same animals, while reduced glutathione (GSH) peroxidase and GSH S-transferase were slightly yet significantly depressed. No significant difference was recorded for other biochemical parameters, including GSH, oxidized glutathione (GSSG) reductase, NADH- and NADPH-dependent diaphorases, and DT diaphorase. In parallel, fish exposed to polluted seawater exhibited a significant and marked enhancement of the metabolic activation of the pyrolysis product Trp-P-2 and of benzo[a]pyrene-trans-7,8-diol, and at the same time were less efficient in detoxifying the antitumor compound ICR 191. Liver S12 fractions from both sources efficiently decreased the direct mutagenicity of sodium dichromate, and failed to activate benzo[a]pyrene and aflatoxin B1 to mutagenic metabolites. These results provide evidence that both biochemical parameters and the overall capacity of fish liver to activate or detoxify certain mutagens can be assumed to be sensitive indicators of exposure to mixed organic pollutants in the marine environment.

Biomarkers of Exposure and Effect in Flounder (Platichthys flesus) Exposed to Sediments of the Adriatic Sea

The modifications of several biomarkers were investigated in flounder (Platichthys flesus) when exposed in the laboratory to sediment samples collected from the Northern Adriatic Sea. Besides clean sand used as a control substrate, fish were exposed to sediments sampled offshore the delta of the Po River, the harbour of Trieste, and from the industrial harbour of Venice (Porto Marghera). After six days of exposure, the enzyme activities ethoxyresorufin-O-deethylase (EROD), UDP glucuronyltransferase (UDPGT), glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx), were assayed in fish liver. In addition, the contents of reduced glutathione (GSH), nonprotein thiols (SH), total sugars and extractable lipids were also determined in hepatic tissue, as well as the number of micronucleated hepatocytes and biliary concentrations of fluorescent aromatic compounds (FAC). Despite some variability within treatment groups, differences among exposed organisms were evident and consistent with known contaminant levels of sampled areas. Microsomal activities (EROD, UD-PGT) and FAC levels were the most sensitive exposure indicators. Variations in the other biomarkers showed only tendencies which although not statistically significant were generally consistent with the contamination pattern.

Diatom invasion in the antarctic hexactinellid sponge Scolymastra joubini

Abstract Sponges often host large amounts of symbionts, mainly represented by cyanobacteria and dinoflagellates. Recent findings show a widespread presence of symbiotic diatoms living inside antarctic demosponges. In this paper, the invasion by large populations of the diatom Melosira sp. into specimens of the hexactinellid sponge Scolymastra joubini is reported. SEM analyses support the hypothesis that the embedded living diatoms have a negative impact on sponge tissues, leading to degenerative processes.

Involvement of the gill chloride cells of trout under acute nitrite intoxication

Abstract 1. 1. In the gill of trout ( Salmo gairdneri Rich.) treated with 450 μg N-NO 2 /l for 72 hr, ultrastructural changes are seen especially in chloride cells, probably due to an accelerated turnover. 2. 2. Despite the marked inhibition exerted by nitrite on gill carbonic anhydrase activity, blood Cl − content of treated trout is not altered. 3. 3. The hypertrophia observed in some gill chloride cells could be a hyperactive response attempting to maintain physiological Cl − levels in the presence of NO 2 − and lowered HCO 3 − production.

Xenobiotic metabolizing enzymes in uninduced and induced rainbow trout (Oncorhynchus mykiss): Effects of diets and food deprivation

Abstract 1. Untreated and β-naphtoflavone (BNF)-treated trout ( Oncorhynchus mykiss ) were maintained for 15–21 days under 3 different feeding regimens or under starvation. 2. Possible diet effects were studied by measuring the following 13 hepatic parameters: aminopyrine demethylase (APDM), ethoxyresorufin-O-deethylase (EROD), benzo(a)pyrene hydroxylase (AHH), UDP glucuronyltransferase (UDPGT), glutathione reductase (GR), glutathione-S-transferase (GST), glutathione peroxidase (GPx), glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) enzyme activities; the content of total cytochrome P-450 (P-450); proteic and non-proteic SH groups (SHP, SHNP) and liver somatic index (LSI). 3. The results show that some feeding regimens affect a large number of these parameters in both uninduced and BNF-treated fish. 4. Hence, caution should be imposed in the use of the biochemical markers as a water-quality monitoring tool. 5. In particular, it is advisable to maintain fish without feeding during short-term experiments, especially because trout exhibit an excellent biochemical response to inducer even after a 21-day starvation period. 6. Conversely, when fish are to be necessarily fed (long-term experiments), diet must be carefully chosen and controlled by preliminary tests because some commercial fish pellets contain both inducers and inhibitors of several microsomal/cytosolic enzymes.