Effects of fertilization and development of the common mussel Mytilus edulis after long-term exposure to a nonionic surfactant

Common mussels (Mytilus edulis L.) were exposed over a 5-month period to low-level concentrations (0.5 to 1.5 ppm) of a nonionic surfactant. Upon maturation at the end of this period, spawning ability was examined. Fertilization occurred at low-level concentrations (0.1 to 2.0 ppm) of the surfactant, and was most successful for gametes from the long-term controls and the highest long-term concentration (1.5 ppm). Inhibited or delayed larval development was observed, related to the concentration gradient of the short-term exposures. Gametes from mussels long-term exposed to the surfactant were more sensitive than those from the long-term control.     

Stimulatory effect of ingested protein and/or free amino acids on the secretion of the gastro-endocrine hormone cholecystokinin and on tryptic activity, in early-feeding herring larvae, Clupea harengus

In the larvae of many marine teleosts, the stomach is absent until they approach or attain metamorphosis. Consequently, the formation of chyme containing specific free amino acids from the gastric digestion of protein, which are believed to be signals initiating the release of the digestive hormone cholecystokinin (CCK), is lacking. CCK, when secreted into the blood circulation from specialized intestinal cells, stimulates gallbladder motility and is a key factor causing the release of pancreatic digestive enzymes into the gut lumen. Using first-feeding Atlantic herring larvae (Clupea harengus) as a model, the aim of the present study was to determine if a CCK response together with tryptic activity could be elicited in larvae ingesting dietary protein and/or FAA. Larvae were tube fed single lamellar liposome vesicles (SLV) containing: (1) physiological saline (PS), (2) bovine serum albumin (BSA), (3) specific free amino acids (FAA), or (4) a ratio (1:1) of BSA and FAA. The CCK and trypsin levels were then assayed (radio-immunoassay) at 0, 15, 60 and 120 min after tube feeding. A marked CCK response was elicited in all treatments compared to the PS control at 15 and 30 min and was significant (p<0.05) at 120 min after tube feeding. Larvae tube fed the FAA treatment exhibited CCK levels that increased linearly from 1.6 to 5.6 fmol mg^-1 dry weight (DW) after 2 h of digestion, although this response was below the BSA and BSA:FAA treatments. The BSA and BSA:FAA treatments, after 15 min of digestion, showed a rapid CCK increase, over the PS and the FAA liposome treatments, to 8.1 and 5.4 fmol mg^-1 DW, respectively. At the end of the assay, BSA and BSA:FAA demonstrated similar levels (10.2 and 9.2 fmol mg^-1 DW, respectively). Larvae tube fed the PS control or the FAA liposome treatment did not demonstrate any appreciable increase in tryptic activity during the 2 h digestion period (0.03-0.071 and 0.03-0.048 mU mg^-1 DW, respectively). In contrast, the BSA:FAA treatment increased from 0.03-0.148 mU mg^-1 DW 1 h after feeding, which was significantly (p<0.05) higher than the PS and FAA liposomes, and then decreased markedly (0.085 mU mg^-1 DW) after 2 h of digestion. The larvae tube fed BSA liposomes, however, demonstrated steadily increasing tryptic activity throughout the sampling period, attaining 0.255 mU mg^-1 DW after 2 h, which was significantly (p<0.05) more than all the other treatments. The results showed that ingested liposomes containing FAA or the protein BSA or a combination of these two nutrients effectively stimulated CCK production in first-feeding herring larvae. In contrast, liposomes containing only physiological saline did not elicit a CCK response. In addition, liposomes containing BSA stimulated tryptic activity in herring larvae, which was not observed in fish fed liposomes that included only FAA or PS. This suggests that a suitable protein substrate is required to regulate protein digestion.     

Partitioning of inorganic and organic mercury in cockles Cardium edule (L.) and C. glaucum (Bruguiére) from a chronically polluted area: influence of size and age

Partitioning of inorganic and organic mercury was studied in the cockles Cardium edule and C. glaucum sampled in a chronically polluted area in the Western Limfjord, Denmark. The proportion of organic mercury in the cockles was linearly correlated to age (and weight) but not to total mercury concentration in the cockles. In 2-, 3- and 4-year-old cockles organic mercury constituted c. 30%, 60%, and 90% of total mercury, respectively. The age correlated proportion of organic mercury is discussed in a food chain context.     

A 10-year survey, 1980–1990, of prenatally diagnosed small supernumerary marker chromosomes,identified by fish analysis. Outcome and follow-up of 14 cases diagnosed in a series of 12 699 prenatal samples

A cytogenetic survey and follow-up studies were made of 14 cases with supernumerary marker chromosomes, identified among 12 699 prenatal samples, investigated at our institution over a 10-year period from 1980 to 1990. FISH (fluorescence in situ hybridization) techniques were employed to identify the chromosomal origin of the marker chromosomes. Five cases were familial, all derived from acrocentric chromosomes, and all without apparent phenotypic effects in the children. Nine cases represented de novo aberrations. In two cases (one with a marker from chromosome 14 or 22, the other with a ring-like marker derived from chromosome 17), the pregnancies continued and apparently normal babies were delivered at term, but the child with a marker derived from chromosome 17 showed slight psychomotor retardation at 2 years of age. All other pregnancies with de novo markers were terminated. In three cases, significant abnormalities were found at autopsy. One of these had an isochromosome 12p and the phenotype was consistent with Pallister-Killian syndrome. In conclusion, marker chromosome identification, as well as clinical follow-up, is essential for the purpose of improving genetic counselling.     

Transport and reduction of nitrate in clayey till underneath forest and arable land

Transport and reduction of nitrate in a typically macroporous clayey till were examined at variable flow rate and nitrate flux. The experiments were carried out using saturated, large diameter (0.5 m), undisturbed soil columns (LUC), from a forest and nearby agricultural sites. Transport of nitrate was controlled by flow along the macropores (fractures and biopores) in the columns. Nitrate reduction (denitrification) determined under active flow mainly followed first order reactions with half-lives (t(1/2)) increasing with depth (1.5-3.5 m) from 7 to 35 days at the forest site and 1-7 h at the agricultural site. Nitrate reduction was likely due to microbial degradation of accumulated organic matter coupled with successive consumption of O2 and NO3- in the macropore water followed by reductive dissolution of Fe and Mn from minerals along the macropores. Concentrations of total organic carbon measured in soil samples were near identical at the two study sites and consequently not useful as indicator for the observed differences in nitrate reduction. Instead the high reduction rates at the agricultural site were positively correlated with elevated concentration of water-soluble organic carbon and nitrate-removing bacteria relative to the forest site. After high concentrations of water-soluble organic carbon in the columns from the agricultural site were leached they lost their elevated reduction rates, which, however, was successfully re-established by infiltration of new reactive organics represented by pesticides. Simulations using a calibrated discrete fracture matrix diffusion (DFMD) model could reasonably reproduce the denitrification and resulting flux of nitrate observed during variable flow rate from the columns.     

Biodegradation of linear alkylbenzene sulfonates in sulfate-leached soil mesocosms

Aromatic sulfonates (R-SO(3)(-)) can be used as sulfur sources by sulfate-starved bacteria in laboratory cultures and the corresponding phenols are excreted from the cells. The present study was conducted to demonstrate whether such desulfonation reactions also occur in sulfate-leached agricultural soil, where desulfonation of organic sulfur compounds may have agronomic importance as a S source for plants. Xenobiotic linear alkylbenzene sulfonates (LAS) were added to nominal concentrations of 0, 10 and 100 mgkg(-1) dry weight in a sandy soil that was depleted in sulfate by leaching the soil with water (sulfate depletion, approximately 75%). The soil was incubated at 20 degrees C in duplicate 3-dm(3) mesocosms for 8 weeks. Primary degradation of LAS was rapid with half-lives of 1-4 days. Sulfophenylcarboxylates were identified and quantified as intermediates, whereas linear alkylphenols (the expected primary desulfonation products) were not detected by high-pressure liquid chromatography coupled with both fluorescence and electrospray ionization-mass spectrometry. Thus, LAS was used by the bacteria as a source of energy and carbon, rather than as a source of sulfur. Measurements of soil pH, fluorescein diacetate (FDA) hydrolysis and arylsulfatase activity showed that stable microbial conditions prevailed in the soil mesocosms. FDA hydrolysis (a measure of total microbial activity) was transiently inhibited at the highest LAS concentrations. Arylsulfatase activity (i.e., hydrolysis of aromatic sulfate esters) was not significantly affected by the soil incubation, although arylsulfatases may be upregulated in sulfate-starved bacteria. However, an increased production of arylsulfatase may be difficult to detect due to the background of extracellular arylsulfatases stabilised in the soil. Therefore, the present data does not exclude a regulatory response to sulfate depletion by the soil microorganisms. However, the importance of desulfonation reactions in natural environments still needs to be demonstrated.