Aflatoxin B1-induced ultrastructural alterations in matureZea mays embryos

Mature maize (Zea mays L.) embryos were exposed to aflatoxin B₁ (AFB₁) concentrations ranging from 0.1 to 25 µg/ml for 9 days. With increasing toxin concentration above 2 µg/ml, primary root elongation of germinated embryos was progressively inhibited, to reach a maximum value of 81% at 25 µ/ml toxin. An ultrastructural investigation of the subcellular alterations induced following toxin exposure provided evidence of deteriorative changes in several compartments of the plant cell. Alteration in membrane integrity (e.g., the tonoplast, plasmalemma and inner mitochondrial membrane) was a frequent feature of many cells. Apparent fusion of vacuoles, incorporation of cytoplasmic components into vacuoles and intravacuolar membrane whorls might be interpreted as deteriorative alterations. The results are discussed in the light of ultrastructural findings for other plant systems exposed to similar AFB₁ concentrations, as well as findings for animal systems.     

Reduction of cyanobacterial toxins through coprophagy in Mytilus edulis

An experiment was conducted to follow the fate of the cyanobacterial toxin, nodularin, produced by Nodularia spumigena through ingestion by Mytilus edulis and re-ingestion of faecal material (coprophagy). Mussels were fed with cultures of N. spumigena, and the faeces that were produced were fed to other mussels not previously exposed to N. spumigena. Concentrations of nodularin were measured in the food (N. spumigena), the mussels and in the faeces in order to make a toxin budget. High concentrations of nodularin were found in the mussels and their faeces after 48 h incubation with N. spumigena. When the toxic faeces were fed to new mussels, the toxin content of faeces was reduced from 95 μg nod g⁻¹ dry weight (DW) to 1 μg nod g⁻¹ DW through the process of coprophagy. Hence, when toxic faeces were fed to mussels, the nodularin concentration of the resulting faecal material was reduced by 99%. Pseudofaeces were produced when the mussels were grazing on N. spumigena, but not when grazing on faeces. The pseudofaeces contained high concentrations of nodularin and apparently intact N. spumigena cells. However, these cells were growth-inhibited and their potential contribution to seeding a bloom is probably limited. Our data indicate that a large fraction of ingested nodularin in M. edulis is egested with the faeces, and that the concentration of nodularin in the faeces is reduced when faeces are re-ingested.     

Dynamics of the phycotoxin domoic acid: accumulation and excretion in two commercially important bivalves

Batch cultures of the toxigenic diatomNitzschia pungens Grunow f.multiseries Hasle were fed to blue mussels (Mytilus edulis) and deep sea Atlantic scallops (Placopecten magellanicus) to elucidate conditions under which domoic acid (DA) was accumulated and excreted (depurated). Mussels accumulated the toxin to a maximum level of 13 g g^-1, at rates of 0.21 to 3.7 g h^-1 g^-1, dry weight. Accumulation efficiency (the proportion of accumulated DA to estimated net uptake) ranged from 1–5%. The highest filtration rate of 1.71 h^-1 occurred at concentrations of 4–8 × 10⁶ Nitzschia cells 1^-1 with no formation of pseudofeces. Depuration rates between fed and starved mussels over a 2 h test period were the same. The depuration rate of domoic acid was about 17% d^-1 and did not account for the low uptake efficiencies, so it is suggested that most of the DA is lost from mussels in the solution during the feeding process. Domoic acid accumulation in mussels was dependent on the amount of toxin available, which in turn was a function of the density and growth phase of theNitzschia population. Changes in filtration rate withNitzschia concentration and depuration rate with time can account for the DA levels of mussels collected during toxic episodes in Cardigan Bay, Prince Edward Island, Canada in 1988 and 1989.Scallops accumulated DA (0.39–1.3 g h^-1 g^-1, more slowly than mussels, however, accumulation efficiencies ranged from 5–100%. Filtration rates remained relatively low and constant at 0.081 h^-1. Scallops retained domoic acid longer than mussels, a fact which must be considered in the marketing of whole scallops for human consumption.     

Physiological background for using freshwater mussels in monitoring copper and lead pollution

In studying the effect of copper (10 ± 0.57 µg Cu l^–1 and 100 ± 3.01 µg Cu l^–1) and lead (50 ± 1.12 µg Pb l^–1 and 500 ± 12.5 µg Pb l^–1) on the filtration activity of Anodonta cygnea L. it was found that both heavy metals resulted in significant shortening of the active periods, but little change occurred in the length of the rest periods. The concentrations of copper and lead were measured in the gill, foot, mantle, adductor muscle and kidney for 840 hours of exposure to 10.9 ± 5 µg Cu l^–1 and 57.0 ± 19 µg Pb l^–1 as well as during subsequent depuration. Uptake was observed after 72 hours of exposure. The highest copper concentration (59.1 ± 16.2 µg Cu g^–1) was measured at 672 h in the mantle, and the highest lead value (143 ± 26.1 µg Pb^–1) was obtained in the kidney. Depuration of copper was fastest from the foot, and from the adductor muscle for lead. The gill had the longest half-depuration time (> 840 h for copper and > 672 h for lead).     

Metabolism of Klebsiella pneumoniae freeze‐dried cultures for the design of BOD bioassays

Aims: The survival rate of freeze‐dried cultures is not enough information for technological applications of micro‐organisms. There could be serious metabolic/structural damage in the survivors, leading to a delay time that can jeopardize the design of a rapid biochemical oxygen demand (BOD) metabolic‐based bioassay. Therefore, we will study the metabolic activity (as ferricyanide reduction activity) and the survival rate (as colony‐forming units, CFU) of different Klebsiella pneumoniae freeze‐dried cultures looking for stable metabolic conditions after 35 days of storage. Method and Results: Here, we tried several simple freeze‐drying processes of Kl. pneumoniae. Electrochemical measurements of ferrocyanide and survival rates obtained with the different freeze‐dried cultures were used to choose the best freeze‐drying process that leads to a rapid metabolic‐based bioassay. Conclusions: The use of milk plus monosodium glutamate was the best choice to obtain a Kl. pneumoniae freeze‐dried culture with metabolic stable conditions after storage at ?20°C without the need of vacuum storage and ready to use after 20 min of rehydration. We also demonstrate that the viability and the metabolic activity are not always directly correlated. Significance and Impact of the Study: This study shows that the use of this Kl. pneumoniae freeze‐dried culture is appropriate for the design of a rapid BOD bioassay.     

Effect of aflatoxin B1 on germination index and seedling growth in wheat varieties

The effect of different concentrations of aflatoxin B₁ (100, 250, 500, 1000, 2000 µg/l) was studied on germination index and seedling growth in three varieties of wheat seeds. Inhibition in the above process was directly influenced by the concentration of toxin. Concentration of toxin had highly significant effect (p<0.001) for seed germination rate and radicle and plumule development. Inhibition dose for 50% reduction in germination rate (ID₅₀) determined by probit analysis was maximum for the variety HP-129 (895 µg/l).     

Succession of phytoplankton in a deep stratifying lake: Mondsee,Austria

Phytoplankton numbers, biovolume, chlorophyll-a and various physico-chemical characteristics were followed at weekly intervals in Mondsee, Austria during the year 1982. Secchi-disk transparency varied from 10 m in winter to 2 m in September. Prior to the onset of stratification phosphate-phosphorus concentration was 4 µg 1^–1 decreasing to undetectable values thereafter. Nitrate-nitrogen dropped from 590 µg 1^–1 to about 100 µg 1^–1 during the same time. The vernal bloom was dominated by Asterionella formosa Hass. which abruptly declined after silicon depletion. Spring growth ceased in early June, when Tabellaria flocculosa (Lyngb.) Kütz var. asterionelloides Grun. dominated. Oscillatoria rubescens D.C. and Microcystis aeruginosa Kütz. dominated summer and early autumn followed by the chrysophyte Dinobryon divergens Imh. and D. sociale Ehr. which formed up to 69% of total biovolume in October. Thereafter diatoms and Cryptophyceae (Rhodomonas lacustris Pascher and Ruttner, Cryptomonas pusilla Bach.) became abundant again.Maximum chlorophyll-a concentration in the epilimnion (16 µg 1^–1) was reached during spring growth of the diatoms. During summer higher chlorophyll-a levels were always associated with the metalimnetic layer of Oscillatoria.Compared with earlier studies, both the total biovolume and the share of Oscillatoria rubescens significantly decreased because of reduced nutrient loading of the lake and wash-out of Oscillatoria (theor. renewal time of the lake: 1.7 years).     

Relative importance of the trophic and direct pathways on PCB contamination in the rotifer species Brachionus calyciflorus (Pallas)

To determine the contribution of food ingestion (trophic pathway) to PCB contamination of zooplankton in the river Meuse (Belgium), we used ¹⁴C-labelled algae (Dictyosphaerium ehrenbergianum) to measure ingestion and assimilation rates in the rotifer species Brachionus calyciflorus. When the concentration of algae in the culture medium varied from 20 10³ to 200 10³ algal cells ml^–1 (0.12 to 1.18 mg Cl^–1), the Brachionus calyciflorus ingestion rate varied from 0.25 ± 0.12 to 1.52 ± 0.43 ng C ind^–1 h^–1 at 15 °C and from 0.74 ± 0.17 to 5.93 ± 0.61 ng C ind^–1 h^–1 at 20 °C. The assimilation efficiency (ratio of the assimilation rate to the ingestion rate) measured in a culture medium containing 200 10³ algal cells ml^–1 was 55.7 ± 5.8%. Since the PCB concentration measured in the phytoplankton of the river Meuse is about 3 µg PCBs g^–1 D.W., the estimated PCB contamination of zooplankton ascribable to the trophic pathway ranges from 0.22 ± 0.17 to 1.31 ± 0.77 µg PCBs g^–1 D.W. at 15 °C and from 0.64 ± 0.34 to 5.10 ± 2.10 µg PCBs g^–1 D.W. at 20°C. The lower figure based on measurements effected at 20 °C is comparable to the actual level measured in zooplankton samples collected in the river Meuse (0.69 ± 0.20 µg PCBs g^–1 D.W.). The applicability of the formula used in our estimate was checked in a 48-hour in vitro experiment in which the rotifers were fed contaminated algae. The PCB accumulation measured in the rotifers was found to coincide with the calculated PCB contamination. Additional experiments were carried out to determine the contribution of the direct pathway to PCB contamination of zooplankton living in the river Meuse (0.02 µg PCBs l^–1 of water; average dissolved organic matter: 3 mg C 1^–1). The PCB concentration in zooplankton resulting from direct uptake of PCBs from the water was estimated at 0.19 ± 0.05 µg PCBs g^–1 D.W. These results show that in zooplankton living in polluted ecosystems, PCBs are likely to accumulate via the trophic pathway to concentrations up to 30 times higher than by direct contamination. Furthermore, our estimates of PCB contamination via the trophic pathway coincide quite well with actual concentrations measured in situ.     

Evidence of freshwater algal toxins in marine shellfish: Implications for human and aquatic health

The occurrence of freshwater harmful algal bloom toxins impacting the coastal ocean is an emerging threat, and the potential for invertebrate prey items to concentrate toxin and cause harm to human and wildlife consumers is not yet fully recognized. We examined toxin uptake and release in marine mussels for both particulate and dissolved phases of the hepatotoxin microcystin, produced by the freshwater cyanobacterial genus Microcystis. We also extended our experimental investigation of particulate toxin to include oysters (Crassostrea sp.) grown commercially for aquaculture. California mussels (Mytilus californianus) and oysters were exposed to Microcystis and microcystin toxin for 24 h at varying concentrations, and then were placed in constantly flowing seawater and sampled through time simulating riverine flushing events to the coastal ocean. Mussels exposed to particulate microcystin purged the toxin slowly, with toxin detectable for at least 8 weeks post-exposure and maximum toxin of 39.11 ng/g after exposure to 26.65 μg/L microcystins. Dissolved toxin was also taken up by California mussels, with maximum concentrations of 20.74 ng/g after exposure to 7.74 μg/L microcystin, but was purged more rapidly. Oysters also took up particulate toxin but purged it more quickly than mussels. Additionally, naturally occurring marine mussels collected from San Francisco Bay tested positive for high levels of microcystin toxin. These results suggest that ephemeral discharge of Microcystis or microcystin to estuaries and the coastal ocean accumulate in higher trophic levels for weeks to months following exposure.     

Uptake and distribution of cadmium in maize inbred lines

Genotypic variation in uptake and distribution of cadmium (Cd) was studied in 19 inbred lines of maize (Zea mays L.). The inbred lines were grown for 27 days on an in situ Cd-contaminated sandy soil or for 20 days on nutrient solution culture with 10 µg Cd L^-1. The Cd concentrations in the shoots showed large genotypic variation, ranging from 0.9 to 9.9 µg g^-1 dry wt. for the Cd-contaminated soil and from 2.5 to 56.9 µg g^-1 dry wt. for the nutrient solution culture. The inbred lines showed a similar ranking for the Cd concentrations in the shoots for both growth media (r²=0.89). Two main groups of inbreds were distinguished: a group with low shoot, but high root Cd concentrations (shoot: 7.4±5.3 µg g^-1 dry wt.; root: 206.0±71.2 µg g^-1 dry wt.; shoot Cd excluder) and a group with similar shoot and root Cd concentrations (shoot: 54.2±3.4 µg g^-1 dry wt.; root: 75.6±11.2 µg g^-1 dry wt.; non-shoot Cd excluder). The classification of the maize inbred lines and the near equal whole-plant Cd uptake between the two groups demonstrates that internal distribution rather than uptake is causing the genotypic differences in shoot Cd concentration of maize inbred lines. Zinc (Zn), a micronutrient chemically related to Cd, showed an almost similar distribution pattern for all maize inbred lines. The discrepancy in the internal distribution between Cd and Zn emphasizes the specificity of the Cd distribution in maize inbred lines.     

Effects of mine effluent on uptake of Co,Ni, Cu,As, Zn,Cd, Cr and Pb by aquatic macrophytes

Concentrations of Ni, Co, Cu, Pb, Zn, Cd, Cr and As were determined in aquatic sediments, water and macrophytes collected from a fluvial system, contaminated by mine effluents. Myriophyllum verticillatum collected in May below the trace element point source accumulated 169 µg/g of Ni, 860 µg/g of Co, 37 µg/g of Cu, 31 µg/g of Pb, 92 µg/g of Zn, 6.9 µg/g of Cr and 1,200 µg/g of As (concentrations in dry weight). The aquatic macrophytes Nymphaea odoratae and Pontederia cordata accumulated the investigated trace elements to a much lesser extent. The concentrations of trace elements in Myriophyllum verticillatum decreased from May to August. Correlations were found between the concentrations of total Ni, Co and Cu in the bottom sediment and in the submerged macrophytes. However, there was no correlation between the amounts of these trace elements extractable by 0.5 N HCl from the sediments and the concentrations in the macrophytes.     

Freeze tolerance and accumulation of cryoprotectants in the enchytraeid Enchytraeus albidus (Oligochaeta) from Greenland and Europe

The freeze tolerance and accumulation of cryoprotectants was investigated in three geographically different populations of the enchytraeid Enchytraeus albidus (Oligochaeta). E. albidus is widely distributed from the high Arctic to temperate Western Europe. Our results show that E. albidus is freeze tolerant, with freeze tolerance varying extensively between Greenlandic and European populations. Two populations from sub Arctic (Nuuk) and high Arctic Greenland (Zackenberg) survived freezing at −15 °C, whereas only 30% of a German population survived this temperature. When frozen, E. albidus responded by catabolising glycogen to glucose, which likely acted as a cryoprotectant. The average glucose concentrations were similar in the three populations when worms were frozen at −2 °C, approximately 50 μg glucose mg⁻¹ tissue dry weight (DW). At −14 °C the glucose concentrations increased to between 110 and 170 μg mg⁻¹ DW in worms from Greenland. The average glycogen content of worms from Zackenberg and Nuuk were about 300 μg mg⁻¹ DW, but only 230 μg mg⁻¹ DW in worms from Germany showing that not all glycogen was catabolised during the experiment. Nuclear magnetic resonance spectrometry (NMR) was used to screen for other putative cryoprotectants. Proline, glutamine and alanine were up regulated in frozen worms at −2 °C but only in relatively small concentrations suggesting that they were of little significance for freeze survival. The present study confirms earlier reports that freeze tolerant enchytraeids, like other freeze tolerant oligochaete earthworms, accumulate high concentrations of glucose as a primary cryoprotectant.     

Synergy of fluconazole with macrophages for antifungal activity againstCandida albicans

The possible synergy between macrophages and fluconazole for antifungal activity against different isolates ofC. albicans was studied. The susceptibility ofC. albicans isolates to fluconazole (FCZ), when incubated in RPMI-1640 with 10% fetal bovine serum (FBS) and 10% fresh mouse serum (test medium, TM) was determined by using a quantative culture methodology. Multiplication of isolate Sh27 was strongly inhibited by FCZ, even at 1.0 µg/ml. However, FCZ even at 100 µg/ml was not fungicidal. Resident murine peritoneal macrophages (MP) incubated for 48 h in RPMI-1640+10% FBS (tissue culture medium, TCM), then challenged with Sh27 in TM for 24 h, were fungistatic (20±9%,n=4). Cultured macrophages synergized with FCZ (10 µg/ml) for fungicidal activity when co-cultured with Sh27 in TM for 24 h (46±8%) and for 48 h (74±5%),n=3. Macrophages and FCZ (10 µg/ml) could not synergize for significant killing of a less FCZ-sensitiveC. albicans isolate 94-164. Multiplication of a FCZ-resistant isolate (94–20) was not inhibited by FCZ at 10 µg/ml TM; however, macrophages and FCZ (10 µg/ml) could synergize for fungistatic (64%), but not fungicidal, activity.     

Effects of salinity, light and inorganic nitrogen on growth and toxigenicity of the marine dinoflagellate Alexandrium tamarense from northeastern Canada

Growth and toxin production of a highly toxic clone of the marine dinoflagellate Alexandrium tamarense, isolated from the lower St Lawrence estuary (Quebec) in eastern Canada, were studied in unialgal batch cultures under different conditions. Controlled experiments were conducted on the production of paralytic shellfish poisoning (PSP) toxins under conditions of varying light (40, 60, 150, 230 and 470 mol m^-21 s^-1), salinity (10, 15, 20, 25 and 30) and nitrate concentrations (0, 88, 364, 528 and 880 mol l^-1). The effects of variable environmental factors on both toxin composition (% molar) and cell toxicity [pg STXeq (saxitoxin equivalents) cell^-1] were determined through the culture cycle. The toxin profile (% molar; mean SD), determined by high-performance liquid chromatography with fluorescence detection (HPLC-FD), remained stable and was consistently dominated by the low-potency N-sulfocarbamoyl toxins C1/C2 (64.0 ± 3%). There were also substantial relative amounts of the high-toxicity carbamate derivatives gonyautoxin 1-4 (GTX1-4) (1.7 ± 0.5%), neosaxitoxin (NEO) (16.2 ± 2%) ans saxitoxin (STX) (17.8 ± 2%). The cellular toxicity (mean ± SD: 58.8 ± 7 pg STXeq cell^-1) was essentially independent of light, salinity and nitrate concentration throughout the exponential growth phase, but varied over the growth stages in cultures. A positive correlation was observed between cellular toxicity and salinity-dependent growth rate, indicating that cell toxin quota may be affected by extrinsic factors, but it is not always a direct functional response to specific environmental stress.      

Temporal and spatial variability in the heavy-metal content of Dreissena polymorpha (Pallas) (Mollusca: Bivalvia) from the Kleines Haff (northeastern Germany)

The present investigation was performed on zebra mussels, Dreissena polymorpha (Pallas), which were sampled from the Kleines Haff. As a part of the Oder estuary, the Kleines Haff acts as a sink for the load of the river Oder. Mussel shells and mussel tissue were analyzed for their content of selected heavy metals, based on the composition of the suspended matter. Mussels were sampled in May, July, August and September 1996 at different locations and divided into three groups regarding their body size. The data show that concentrations of lead, cadmium and mercury vary during the year. Mussel shells and mussel tissue showed seasonal and local differences in heavy-metal concentration. Between the size classes, however, there was no significant difference, with one exception: the lead content in tissues was significantly higher in large mussels (>2.5 cm shell length) than in small ones (<1.9 cm). The concentrations of lead and cadmium clearly decreased in mussel shells from May to September, while they increased in mussel tissues. The lead concentration in the tissue corresponded to that of mercury. The highest values measured for mercury were 218 μg/kg dry weight (DW), for cadmium 1030 μg/kg DW and for lead 6182 μg/kg DW. The average concentration of heavy metals in mussel tissue was 9 to nearly 170 times lower than in the surrounding sediment and seston. It can be assumed that a balance exists between the concentration of heavy metals in the mussels' food and the mussels themselves.     

Ecological problems of Lake Ladoga: causes and solutions

We studied the outcome of competition between a large (Brachionus calyciflorus) and a small (Anuraeopsis fissa) rotifer species at five algal (Scenedesmus acutus) concentrations (0.5 × 10⁶ to 40.5 × 10⁶ cells ml^–1) and with varying initial densities in mixed populations (100 to 0% of B. calcyciflorus or A. fissa), the combined initial biomass being 0.2 µg ml^–1 in all test jars. Experiments were conducted at 28 ± 1 °C.Regardless of food concentration, B. calcyciflorus showed a greater increase in biomass than A. fissa, peak densities (mean ± standard error) at the lowest food concentration in the controls being 1.34 ± 0.31 µg dry weight ml^–1 and 0.82 ± 0.08 dry weight ml^–1, respectively. At the lower food concentrations, A. fissa displaced B. calyciflorus and vice versa at the higher food concentrations. At the intermediate food concentrations of 4.5 × 10⁶ cells ml^–1, B. calyciflorus outcompeted A. fissa only if its initial population density was three times higher. The rates of population growth in controls varied from 0.792 ± 0.06 d^–1 to 1.492 ± 0.13 d^–1 for B. calyciflorus and 0.445 ± 0.04 to 0.885 ± 0.01 for A. fissa depending on food level. When both species were introduced together, low food levels favoured higher abundance of A. fissa than B. calyciflorus, suggesting, in nature, it is likely that small Anuraeopsis colonize oligotrophic water bodies more successfully than larger Brachionus. The results also suggest that the outcome of competition depends not only on the size of the competing species and food availability but also on their colonizing density.     

Effects of aflatoxin B1 on in vitro cultures ofNicotiana tabacum var. Samsun

Calli ofNicotiana tabacum (tobacco) were treated with two dose ranges of aflatoxin B₁ (0.1–2.0 µg ml^–1 - low does; 5–25 µg ml^–1 aflatoxin B₁). The ability of calli to recover following 3 weeks of toxin exposure was also investigated. The I₅₀ (50% inhibition) value for fresh mass accumulation was approximately 2 µg ml^–1 AFB₁. Fresh mass accumulation was significantly lower than the control value from 0.5 µg ml^–1 AFB₁. Following 3 weeks growth without a toxin source, the growth of calli up to and including 10 µg ml^–1 AFB₁, was significantly greater than control calli, indicating reversibility of the toxic effects. With increasing toxin concentration, chlorophyll content of callus was inhibited from 0.5 µg ml^–1. Transfer to a toxin-free medium resulted in a degree of recovery (up to 0.5 µg ml^–1). In the dose range 5–25 µg ml^–1, the levels of chlorophyll were drastically reduced, with no recovery following AFB₁ removal. Electron microscopy revealed a disruption of chloroplast structure as an early deteriorative event in AFB₁ exposure of callus cells. Protein levels were less sensitive, with inhibition manifested only in the high dose range. Shoot development occurred at all concentrations, but was significantly inhibited from 5 µg ml^–1 AFB₁. Recovery following toxin removal was minimal at these higher AFB₁ concentrations. The number of necrotic calli increased progressively from 5 µg ml^–1 as toxin levels increased.     

Determination of regional distributions of phenylethylamine andmeta-andpara-tyramine in rat brain regions and presence in human and dog plasma by an ultra-sensitive negative chemical ion gas chromatography-mass spectrometric (NCI-GC-MS) method

Using a new ultrasensitive method the trace biogenic amines, phenylethylamine,meta-tyramine andpara-tyramine have been quantitated in brain regions obtained from a single rat. Phenylethylamine concentrations in ng/g wet tissue (mean±std. error) were as follows: caudate 2.71±0.73, hypothalamus 0.45±0.15, cerebellum 0.09±0.02, olfactory bulb 0.35±0.11, stem 0.13±0.03, hippocampus 0.20±0.11, cortex 0.69±0.13 and the rest (remainder of the brain) 2.81±0.41. Mean whole brain was 1.23±0.19 ng/g, in agreement with previous measurements.meta-Tyramine concentrations (ng/g) were: caudate 2.69±0.19, hypothalamus 0.32±0.16, cerebellum 0.07±0.04, olfactory bulb 0.09±0.04, stem 0.04±0.01, hippocampus, 0.07±0.02, cortex 0.18±0.15 and the rest 0.15±0.06, with a mean whole brain value of 0.26±0.05 ng/g andpara-tyramine concentrations were: caudate 8.99±1.60, hypothalamus 0.93±0.13, cerebellum 0.78±0.27, olfactory bulb 0.70±0.13, stem 0.90±0.36, hippocampus 0.40±0.06, cortex 1.78±0.28 and the rest 2.38±0.12 and mean whole brain was 1.90±0.25 ng/g. In human plasma the concentrations of the three amines were found to be 31.3±3.4 pg/ml, 5.3±1.6 pg/ml and 66.0±9.9 pg/ml respectively and in dog blood 95.3±4.6 pg/ml, 24.0±7.6 pg/ml and 486±43 pg/ml respectively. When monoamine oxidase inhibitors were added to the blood immediately after collection there were no significant increases in the amine levels indicating that MAO-B is not present in plasma in significant quantities.     

Features of the lipid transport system of fish as demonstrated by studies on starvation in the rainbow trout

Summary A comparison was made of the processes involved in the transport and uptake of lipids in starved and fed trout in order to gain a fuller understanding of the underlying mechanisms of these processes and their control in fish. Trout that had been starved for 8 weeks showed significantly lower lipoprotein lipase activities than control fed fish in their adipose tissue (64±45 and 546±205 units±SEM for starved and fed, respectively;P<0.05) and liver (22±6 and 147±56;P<0.05) but no significant difference in red muscle (22±6 and 88±35) or heart (0.53±0.20 and 0.89±0.27). A similar difference in salt-resistant lipase, present in extra-hepatic tissues in trout, was found, i.e. adipose tissue: 200±105 and 1,327±190 (P<0.05); liver: 133±16 and 404±78 (P<0.01); red muscle: 101±32 and 105±20 (n.s.); heart: 2.43±0.38 and 1.92±0.37 (n.s.). The plasma cholesterol esterifying activity of starved trout (1.79±0.36 units) was significantly lower (P<0.001) than the fed fish (3.74±0.65). The concentrations of plasma VLDL and LDL were 67% and 47% lower (P<0.001 andP<0.05, respectively) in the starved than in the fed trout, while the concentration of HDL was the same (163±15 and 165±20 mg cholesterol/100 ml for starved and fed fish, respectively), as was the concentration of nonesterified fatty acids (0.303±0.039 and 0.333±0.035 mEq/l, respectively). These observations demonstrate that, in spite of differences in the distribution of lipases between the various tissues, fish possess systems for the transport and uptake of lipids that broadly parallel those of mammals and are consistent with the greater use of lipid as a major energy source in fish.Abbreviations VLDL, LDL andHDL very low density, low density and high density lipoproteins, respectively, isolated from trout plasma by flotation at densities 1.023, 1.086 and 1.21 g/ml     

Amino-acid uptake by mussels,Mytilus edulis,from natural sea water in a flow-through system

Natural Wadden Sea water taken from the North Sea (island of Sylt) was pumped at rates of 150 and 300 l h^–1 through a 4 l plexiglass tube mounted on a wooden tripod on the beach. The tube was densely filled with numerous cleaned mussels,Mytilus edulis. HPLC analysis of sea water showed that total dissolved amino acids are patchily distributed, varying by 100 % within 15 min, though proportions of individual amino acids were remarkably constant. Total amino-acid concentrations were 1528±669 nM (N=3) in October 1983 and 1198±597 nM (N=7) in July 1984. Samples taken at the entrance and the outlet of the experimental mussel bed revealed that the mussels had taken up 29 to 66 % of the amino acids dissolved in sea water. Uptake was observed for all amino acids detected in the chromatograms. 78 % of uptake resulted from the 5 most concentrated amino acids: serine, alanine, glycine/threonine, ornithine, aspartic acid. The nutritional profit obtained from uptake of dissolved amino acids amounted to 12 % (N=5, range 5–23 %, flow rate 150 l h^–1) and to 24 % (N=3, range 13–38 %, flow rate 300 l h^–1) of metabolic rate. The present data suggest that amino-acid concentration predominantly determines the magnitude of the nutritional profit obtained from uptake, and to a smaller extent the flow rate. These findings are in contrast to results of previous studies onAsterias rubens, interacting in small-volume closed systems with the natural bacterial sea water flora (Siebers, 1982). In these experiments, bacteria, due to rapid uptake, outcompeted the sea stars in absorption of dissolved amino acids. The present results suggest that bivalve mussels, can, due to their large gill surface areas and the great amounts of water pumped through their mantle cavity, successfully compete with bacteria in uptake of dissolved organic matter. Mussels, therefore, suggestedly play an important role in cycling dissolved organic matter.