Effects of marine noise pollution on Mediterranean fishes and invertebrates: A review.

Marine noise pollution (MNP) can cause a multitude of impacts on many organisms, but information is often scattered and general outcomes difficult to assess. We have reviewed the literature on MNP impacts on Mediterranean fish and invertebrates. Both chronic and acute MNP produced by various human activities - e.g. maritime traffic, pile driving, air guns - were found to cause detectable effects on intra-specific communication, vital processes, physiology, behavioral patterns, health status and survival. These effects on individuals can extend to inducing population- and ecosystem-wide alterations, especially when MNP impacts functionally important species, such as keystone predators and habitat forming species. Curbing the threats of MNP in the Mediterranean Sea is a challenging task, but a variety of measures could be adopted to mitigate MNP impacts. Successful measures will require more accurate information on impacts and that effective management of MNP really becomes a priority in the policy makers' agenda.

Assessment of the use of Oblada melanura (L. 1758) otolith fluctuating asymmetry as environmental disturbance indicator.

Human impact on the environment is of widespread concern. The majority of anthropogenic impacts are centred on coastal ecosystems, so surveying them is an important step in the protection of the marine environment. We have tested Oblada melanura (L. 1758) otoliths' fluctuating asymmetry as a bioindicator in a Mediterranean coastal zone. The French Riviera is characterised by a summer population increase leading in particular to more yachting, and seasonal climatic changes with reduced, more concentrated waterway flows and storm events causing soil erosion. The present three-year study compares nine sites, situated in three zones, and characterised by three types of chemical pollutant states (low; waterway mouth; recreational harbour). For O. melanura juveniles, we have not shown any significant difference in the otoliths' fluctuating symmetry between zones or types of sites. We hypothesize that high stress levels are needed to induce significant fluctuating asymmetry variation.

Assessing Heterodera glycines-Resistant and Susceptible Cultivar Yield Response.

The soybean cyst nematode Heterodera glycines (SCN) is of major economic importance and widely distributed throughout soybean production regions of the United States where different maturity groups with the same sources of SCN resistance are grown. The objective of this study was to assess SCN-resistant and -susceptible soybean yield responses in infested soils across the north-central region. In 1994 and 1995, eight SCN-resistant and eight SCN-susceptible public soybean cultivars representing maturity groups (MG) I to IV were planted in 63 fields, either infested or noninfested, in 10 states in the north-central United States. Soil samples were taken to determine initial SCN population density and race, and soil classification. Data were grouped for analysis by adaptation based on MG zones. Soybean yields were 658 to 3,840 kg/ha across the sites. Soybean cyst nematode-resistant cultivars yielded better at SCN-infested sites but lost this superiority to susceptible soybean cultivars at noninfested sites. Interactions were observed among initial SCN population density, cultivar, and location. This study showed that no region-wide predictive equations could be developed for yield loss based on initial nematode populations in the soil and that yield loss due to SCN in our region was greatly confounded by other stress factors, which included temperature and moisture extremes.

Neurohypophysial hormone receptors and second messengers in trout hepatocytes.

Neurohypophysial hormone receptors and second messengers were studied in trout (Oncorhynchus mykiss) hepatocytes. Arginine vasotocin (AVT) and isotocin (IT) elicited a concentration-dependent inhibition of cAMP accumulation in the presence of 5x10(-8) M glucagon (maximal effect for 4.5x10(-7) M and 1.4x10(-7) M, half-maximal effect for 2.1x10(-8) M and 0.7x10(-8) M, AVT and IT respectively). The effect of glucagon was inhibited up to 90% by AVT and 80% by IT. While AVT inhibited (up to 50%) the basal cAMP production, IT had no such action. Specific V(1) or V(2) analogues (with reference to vasopressin in mammals) were used for pharmacological characterization of the type of neurohypophysial hormone receptor involved in this inhibition. The V(1) agonist [Phe(2), Orn(8)]-oxytocin inhibited the glucagon-stimulated cAMP production with a maximal effect for 6x10(-7) M and a half-maximal effect for 0.9x10(-8) M concentrations of the analogue. While the V(1) agonist reduced the glucagon-stimulated cAMP level by 70%, it showed only a tendency to reduce the basal level. The V(2) agonist [deamino(1), Val(4),d -Arg(8)]-vasopressin had no effect either on basal or on glucagon-stimulated cAMP production. The V(1) antagonist [d(CH(2))(5)(1), O-Me-Tyr(2), Arg(8)]-vasopressin totally reversed the 10(-8) M AVT-induced inhibition of 5x10(-8) M glucagon-stimulated cAMP production, whereas the V(2) antagonist [d(CH(2))(5)(1),d -Ile(2), Ile(4), Arg(8), Ala(9)]-vasopressin had no such effect. In this particular case, maximal and half-maximal effects of the V(1) antagonist were obtained for 2.3x10(-6) M and 1. 2x10(-6 )M respectively. Changes in intracellular calcium content were measured using the fluorescent probe FURA-2/AM. AVT and IT elicited a concentration-dependent increase in Ca(2+) accumulation. The comparison of the effect of 10(-8) M agonists versus AVT showed the following order of potency: AVT=IT>V(1) agonist>V(2) agonist. The V(1) antagonist reversed the AVT-induced Ca(2+) accumulation whereas the V(2) antagonist had no such effect. These results are taken as evidence for the presence in trout hepatocytes of neurohypophysial hormone receptors functionally close to the V(1a)-type linked to cAMP production and Ca(2+) mobilization.

A V1-type receptor for mediating the neurohypophysial hormone-induced ACTH release in trout pituitary.

We analysed the effects of specific neurohypophysial analogues for pharmacological characterization of the type of vasotocin receptor involved in the control of the adrenocorticotrophin hormone (ACTH) release from the perifused pituitary in the rainbow trout, Oncorhynchus mykiss. Mammalian corticotrophin releasing factor (CRF) and teleostean neurohypophysial peptides (arginine vasotocin (AVT) and isotocin (IT)) stimulated ACTH release. Analysis of concentrations giving half-maximal effects (D50) showed that these peptides affected ACTH release in the following order of potency: CRF (8 x 10(-13) M) > AVT (2 x 10(-10) M) > IT (10(-7) M). Maximal responses (Dmax) were obtained for hormonal concentrations of 10(-10) M, 10(-8) M and 10(-6) M respectively. This suggests that AVT and IT have different roles in the control of ACTH release. The values obtained for AVT and IT were in agreement with the circulating levels we previously found for these peptides. Specific V1 or V2 agonists or antagonists (with reference to vasopressin in mammals) were used to define the specificity of the neurohypophysial peptide receptor involved in this stimulation. The V1 agonist, [Phe2, Orn8]-oxytocin, stimulated ACTH release while the V2 agonist, [deamino1, Val4, D-Arg8]-vasopressin, had no such effect. Maximal and half-maximal responses were obtained in the presence of the V1 agonist with 10(-7) M and 7 x 10(-9) M respectively, and were in the range of values obtained with natural peptides. The V1 antagonist, [d(CH2)5(1), O-Me-Tyr2, Arg8]-vasopressin, and the V2 antagonist, [d(CH2)5(1), D-Ile2, Ile4, Arg8, Ala9]-vasopressin, maximally reversed the 10(-9) M AVT-stimulated ACTH release by 60% and 25% respectively, for a 5 x 10(-10) M concentration of the analogues and a D50 approximately 2 x 10(-11) M. These results demonstrated the presence of only one V1-type receptor in fish pituitary, with some of the structural and functional peculiarities typically displayed by the mammalian V1a-type receptor, but distinct from it. In this sense, the fish pituitary vasotocin receptor may represent a novel type of neurohypophysial hormone receptor, more closely related to the mammalian V1b-type.

Vasopressin and oxytocin action in the brain: cellular neurophysiological studies.

During the last two decades it has become apparent that vasopressin (VP) and oxytocin (OT), in addition to playing a role as peptide hormones, also act as neurotransmitters. Morphological studies and electrophysiological recordings have shown a close anatomical correlation between the presence of these receptors and the neuronal responsiveness to VP or OT. These compounds have been found to affect membrane excitability in neurons located in the hippocampus, hypothalamus, lateral septum, brainstem, spinal cord and superior cervical ganglion. Sharp electrode intracellular and whole-cell recordings, done in brainstem motoneurons, have revealed that VP and OT can directly affect neuronal excitability by opening non-specific cationic channels. These neuropeptides can also influence synaptic transmission, by acting either postsynaptically or upon presynaptic target neurons or axon terminals. Whereas in some hypothalamic neurons OT appears to mobilize intracellular calcium, as revealed by calcium imaging techniques, in the brainstem the action of this neuropeptide is mediated by a second messenger which is distinct from the second messenger activated in peripheral target cells. Future studies should be aimed at elucidating the properties of the cationic channels responsible for the neuronal action of VP and OT, at identifying the brain-specific second messengers activated by these neuropeptides and at determining whether endogenous VP and OT can exert neuronal effects similar to those elicited by exogenous neuropeptides.

ELISA measurements of vasotocin and isotocin in plasma and pituitary of the rainbow trout: effect of salinity.

The fish neurohypophysial hormones arginine vasotocin (AVT) and isotocin (IT) were measured for the first time by ELISAs (in comparison with other techniques) in plasma and hypophysis of rainbow trout adapted stepwise from freshwater (FW) to seawater (SW). AVT concentrations were higher than IT in plasma and, conversely, lower in hypophysis. No difference appeared between FW and SW conditions, but plasma hormone concentrations fell when FW fish were moved to 1/3 SW and increased progressively when fish were moved from 1/3 SW to SW. Peptide values obtained in 1/3 SW may correspond to the lowest osmoregulatory constraints occurring in an isosmotic medium in comparison to FW or full SW. The data suggest that storage and/or release of AVT and IT differ, but vary in a similar way with external salinity, and that these peptides should play a role in teleost fish osmoregulation.

Action of a metabotropic glutamate receptor agonist in rat lateral septum: induction of a sodium-dependent inward aftercurrent.

The mechanism by which (1S,3R)-ACPD, a metabotropic glutamate receptor agonist, induces burst firing in lateral septal neurons of the rat was investigated in coronal brainstem slices. Membrane currents were characterized in voltage clamp using whole-cell recordings. In the presence of (1S,3R)-ACPD, following depolarizing voltage jumps, repolarization towards the holding potential generated an inward aftercurrent. It could have a plateau-like phase and decayed exponentially. This (1S,3R)-ACPD-dependent inward aftercurrent was accompanied by an increase in cell conductance and was reduced following partial replacement of extracellular sodium by N-methyl-D-glucamine. It was unaffected by TEA or barium, and persisted in Cs-loaded neurons or following partial replacement of extracellular chloride by isethionate. This suggests that it was mainly carried by sodium. Loading neurons with the calcium chelator, BAPTA, or blocking transmembrane calcium currents, suppressed the (1S,3R)-ACPD-dependent aftercurrent. By contrast, partial replacement of extracellular sodium by lithium did not affect it. Thus, this current was dependent upon calcium influx but was not due to a sodium/calcium exchanger. It was probably mediated by G protein activation. Indeed, in neurons loaded with GTP-gamma-S, following depolarizing voltage jumps, repolarization towards the holding potential revealed an inward aftercurrent having properties similar to those of the (1S,3R)-ACPD-dependent current. We suggest that (1S,3R)-ACPD induced calcium-activated non-selective channels. In the presence of this agonist, a depolarization-evoked calcium influx could thus evoke a cationic inward current. This current probably promotes the burst firing observed in lateral septal neurons in current clamp.

The effect of colchicine-specific active immunization on colchicine toxicity and disposition in the rabbit.

Anti-colchicine antibodies raised in rabbits are effective at protecting rabbits from acute colchicine intoxication. The positive effect depends on the ratio between the binding site capacity of the specific antibodies and the colchicine dose. Immunized rabbits receiving 6 mg/kg colchicine intravenously (LD100) died within 8 h as rapidly as those of the non-immunized control group. In contrast, if the colchicine dose was reduced to 3 mg/kg (LD83), rabbits were protected and mortality decreased to 17%. Study of plasma colchicine pharmacokinetics indicated that colchicine was totally sequestrated by antibodies in the 3 mg/kg group and only 55-80% sequestrated in 6 mg/kg group. This sequestration contributed to reducing colchicine diffusion into tissues (the volume of distribution decreased 7-fold) and to increasing the terminal half-life and the total body clearance of the drug. Moreover, as the slope of the dose-lethality curve was steep, a small binding capacity was sufficient to neutralize colchicine toxicity at 3 mg/kg. Results clearly indicate that anti-colchicine antibodies are able to effectively sequestrate colchicine. Moreover, the amount of circulating antibodies is a crucial limiting factor for the effectiveness of immunotoxicotherapy.

Soybean Cyst Nematode Reproduction in the North Central United States.

An experiment was conducted in Heterodera glycines-infested fields in 40 north central U.S. environments (21 sites in 1994 and 19 sites in 1995) to assess reproduction of this nematode. Two resistant and two susceptible soybean cultivars from each of the maturity groups (MG) I through IV were grown at each site in 6.1 m by 4 row plots. Soil samples were collected from each plot at planting and harvest and processed at Iowa State University to determine H. glycines initial (Pi) and final (Pf) population densities as eggs per 100 cm3 of soil. Overall, reproduction (Pf/Pi) of H. glycines on susceptible cultivars in all MG was similar. Reproduction was higher on MG III and IV susceptible cultivars than on those in MG I and II. Resistant MG I and II cultivars reduced nematode population densities more consistently than those in MG III and IV. Reproduction of the nematode was similar among sites within the same maturity zone (MZ), defined as the areas of best adaptation of the corresponding MG. Nonetheless, careful monitoring of nematode population densities is necessary to assess changes that occur over time in individual fields.

Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.

Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.

Distribution of Heterodera glycines in Ohio.

A 4-year systematic survey for the presence of soybean cyst nematode Heterodera glycines in Ohio soybean fields was initiated in 1992. A total of 667 soybean fields in 63 counties was sampled. Heterodera glycines was present in 91 fields in 40 counties based on soil samples collected, and in one field in each of three additional counties based on soil samples submitted to the Plant and Pest Diagnostic Clinic or through a preliminary survey conducted in 1991. Soybean hectarage in the 43 counties with at least one field known to be infested with H. glycines accounts for 79% of the total Ohio soybean production area. Eight races of H. glycines were identified in 33 samples from 18 counties. The most common was race 3, identified in 15 samples; others were races 1, 2, 4, 5, 6, 10, and 14.

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Effect of vasopressin on the input-output properties of rat facial motoneurons.

Vasopressin can directly excite facial motoneurons in young rats and mice. It acts by generating a persistent inward current, which is Na(+)-dependent, tetrodotoxin-insensitive and voltage-gated. This peptide-evoked current is unaffected by Ca(++) or K(+) channel blockade and is modulated by extracellular divalent cations. In the present work, we determined how vasopressin alters the input-output properties of facial motoneurons. Whole-cell recordings were obtained from these neurons in the current clamp mode, in brainstem slices of young rats. Repetitive firing was evoked by injecting depolarizing current pulses. Steady-state frequency-current (f-I) relationships were constructed and the effect of vasopressin on these relationships was studied. We found that vasopressin caused a parallel shift to the left of the cell steady-state f-I relationship. This effect persisted in the presence of blockers of K(+) or Ca(++) channels. The peptide effect was distinct from that brought about by Ca(++) channel suppression or by apamin, a blocker of the mAHP. These latter manipulations resulted in an increase in the slope of the steady-state f-I relationship. We conclude that the vasopressin-induced modification of the input-output properties of facial motoneurons is probably exclusively caused by the sodium-dependent, voltage-modulated inward current elicited by the peptide, rather than being due to indirect effects of the peptide on Ca(++) channels, K(+) channels or Ca(++)-dependent K(+) channels. Computer simulation, based on a simple model of facial motoneurons, indicates that the introduction of a conductance having the properties of the vasopressin-dependent conductance can entirely account for the observed peptide-induced shift of the f-I relationship.

Enzyme linked immunosorbent assay for the neurohypophyseal hormones arginine vasotocin and isotocin.

A competitive enzyme linked immunosorbent assay (ELISA) using new polyclonal antibodies was developed for the first time for each of two neurohypophyseal hormones: arginine vasotocin (AVT, ubiquitous in vertebrates) and isotocin (IT, restricted to teleost fish). The antibodies obtained were highly specific, showed no cross-reaction between the two peptides and were able to suppress the activity of the peptides in in vitro bioassays. An original feature of the assays was the covalent binding of the peptidic antigen to Covalink microplates. Competition was thereafter made between this bound antigen and the antigen in samples, for a fixed amount of the relevant antibody. Revelation used peroxidase-labeled antibodies. These ELISAs were sensitive enough to detect 1 ng/ml and 0.1 ng/ml for AVT and IT respectively. Moreover, for the first time, the two hormones were measured separately, each in the presence of the other, and shown to exist as circulating hormones in fish.

[Immunotoxicotherapy: protective effect of anti-colchicine antibodies in acute colchicine poisoning in rabbits and mice]. / Immunotoxicothérapie: effet protecteur d'anticorps anticolchicine lors de l'intoxication aiguë à la colchicine chez le lapin et la souris.

Anti-colchicine antibodies are able to neutralize toxic effects of colchicine after acute intoxication in rabbits and mice. The protecting effect is demonstrated by active immunization (rabbits) or passive immunization (mice). These data suggest that the immunotoxicotherapy may be useful for compounds (colchicine) with intracellular action.

Immunotoxicotherapy: present status and future trends.

Immunotoxicotherapy (ITT) is currently used in humans for the treatment of snake venom and cardiac glycoside poisoning. Other toxins have been studied in animals or in vitro to assess their suitability as candidates for detoxification by specific antibodies. Testing conditions are often empirical suggesting that numerous improvements need to be introduced in ITT. Basic mechanisms in ITT include three phases: sequestration, extraction and elimination. The pharmacokinetics of these three phases depend on the type of antidotal binding site (ABS). IgG or its Fab2, Fab or Fv fragment are the possible choices. The Fab fragment is the most frequently used ABS because of its diffusion properties in the peripheral compartments and its renal excretion by glomerular filtration. Toxicokinetic and pharmacokinetic considerations indicate that the dosage cannot be satisfactorily calculated from stoichiometric principles. Study of the toxin dose-lethality curves shows that ABS dosage can be lowered. Moreover, clinical data reveal that some FAb fragments are directly eliminated without acting on toxin molecules. In order to counteract these drawbacks, a compromise between dosage and duration of infusion is suggested. Other improvements will stem from advances in immunologic methodology. Monoclonal and chimeric antibodies are new tools that will help resolve the clinical problems of immunogenicity and adverse reactions associated with polyclonal ABS.

The stress axis, stanniocalcin, and ion balance in rainbow trout.

In teleosts, the stress hormone cortisol and the calcium regulatory hormone stanniocalcin (STC) are both involved in the regulation of ion balance. Under stressful conditions, ion balance is easily disturbed as stressors via the stress signals they evoke disturb easily and primarily gill function. The gills are key in fish gas exchange and ion regulation. The present work evaluates the effect of the pivotal stress signal cortisol, the eventual output of the stress axis on STC secretion in freshwater rainbow trout (Oncorhynchus mykiss). Plasma cortisol levels were manipulated by intraperitoneal injections of porcine ACTH(1-39) or dexamethasone (Dex), and plasma cortisol, STC and mineral status were assessed. A perifusion assay of trout Stannius corpuscles was validated and used to study the direct effects of stress-related signals on STC release. In perifusion, cortisol, adrenocorticotropic hormone (ACTH), and dexamethasone did not affect STC release. ACTH injections increase plasma cortisol (corresponding to an acute stress) and STC concentrations, but did not affect mineral status. Dexamethasone injections resulted either in a classical hypocortisolinemia or, unexpectedly, in hypercortisolinemia. However, independently of the resulting cortisol status Dex induced a chronic stress effect, as indicated by decreased plasma Na, Cl, and Ca levels, and increased plasma STC concentrations. The increased STC secretion cannot be explained by the classical elevation of plasma calcium concentration. Thus, plasma parameters other than calcium could be involved and we propose that STC secretion might be stimulated also by a decrease of NaCl concentrations, implying a broader function than the classical hypocalcemic action of STC.