Oxygen consumption in fathead minnows (Pimephales promelas) following acute exposure to water-borne selenium

Following determination of a concentration of selenate-Se lethal during 24-hr exposures at 22 degrees C, routine oxygen consumption was measured in fathead minnows (Pimephales promelas) exposed to various sublethal concentrations of Se for 24 hr. A median lethal concentration for 24-hr exposures (24-hr LC50) of fathead minnows equalled 82 mg Se/l with 95% fiducial limits of 76-89 mg Se/l. Mean weight-specific oxygen consumption rates of minnows exposed to 0, 15, 40 and 60 mg Se/l for 24-hr ranged from 0.43 to 0.49 mg O2/g-1/hr-1 and were not significantly different. These results indicate that acute exposure to Se does not affect oxygen consumption; however, observations during respirometry trials suggest that minnows at the highest Se concentration may have physiologically compensated to maintain oxygen consumption rates.     

Comparison of ELISAs for detecting vitellogenin in the fathead minnow (Pimephales promelas)

Measurement of vitellogenin (VTG) concentrations in the fathead minnow (Pimephales promelas) is currently being considered and evaluated for screening of endocrine active substances. One of the proposed methods, an enzyme-linked immunosorbent assay (ELISA) based on VTG from carp (Cyprinus carpio), was recently evaluated in an inter-laboratory ring test using whole body homogenates from juvenile fathead minnows. The objective of the current study was to compare the performance of three different ELISAs for measuring fathead minnow VTG: (1) a heterologous carp VTG (cVTG) ELISA used in the ring test, (2) a homologous fathead minnow VTG (fVTG) ELISA, and (3) a hybrid ELISA with the antibody developed for cVTG, but using fVTG for coating the plates and preparing standard curves. VTG was measured in whole body homogenates from juvenile fathead minnows exposed to 17alpha-ethynylestradiol (EE(2); 10 ng/l) and whole body homogenates and plasma from adult fathead minnows exposed to 17beta-estradiol (E(2); 5 mg/kg; i.p.). The cVTG assay showed lower specificity for fathead minnow VTG in whole body homogenates and plasma from treated fish, compared to the fVTG assay. VTG concentrations in juvenile fathead minnow homogenates from the EE(2)-exposed group were approximately 50-fold higher when measured using the fVTG method compared to the cVTG method. Use of the homologous fVTG in the hybrid cVTG assay yielded VTG concentrations in the range of the fVTG assay but the low specificity persisted. The homologous fVTG assay is recommended to achieve accurate quantification of VTG levels in fathead minnows.     

Influence of metal concentrations, percent salinity, and length of exposure on the metabolic rate of fathead minnows (Pimephales promelas)

Understanding the effects of chemical toxicants on energetic processes is an important aspect of ecotoxicology. However, the influence of toxicant concentration and time of exposure on metabolism in aquatic organisms is still poorly understood. The purpose of this investigation was to determine the influence of increasing levels of three stressors (Cu, Cd, percent salinity) and exposure time (24 h and 96 h) on the metabolic rate of fathead minnows (Pimephales promelas). In all 24-h exposures, there existed a threshold concentration, above which metabolic rate decreased significantly compared to the control and lower concentrations. In contrast, the metabolic rate of fish exposed for 96 h increased significantly in all concentrations compared to fish from the control. We suggest fathead minnows exhibit a consistent pattern of metabolic response to stressors, regardless of the physiological mechanisms involved, and that this response differs as a function of time of exposure.     

Temporal characterization of growth of fathead minnow (Pimephales promelas) larvae during sublethal hydrogen cyanide exposure

Growth of fathead minnow yolk sac larvae was characterized from changes in dry weight and total content and concentrations of RNA, DNA and protein in fish exposed to a sublethal level of HCN (58 micrograms/l) and in age matched controls. Cyanide toxicosis occurred within 24 hr of exposure as evidenced by significant reductions in protein and RNA content and RNA/DNA ratio of larvae. After 96 hr exposure to HCN, larvae exhibited the same growth rate and protein synthetic rate (RNA/DNA) as control fish. HCN toxicosis and recovery is rapid and at least partial tolerance to HCN develops within 96 hr of exposure in larval fathead minnows.     

Behavioural responses of fathead minnows to hypoxanthine-3-N-oxide at varying concentrations

Antipredator behaviour of fathead minnows Pimephales promelas increased significantly on exposure to hypoxanthine-3-N-oxide at concentrations as low as 0·4 n with no further increase in response at concentrations up to 6·7.     

Effects of cadmium on foraging behaviour of lake charr, Salvelinus namaycush

Synopsis Foraging behaviour of lake charr, Salvelinus namaycush, exposed to 0.5 and 5.0 g l^–1 cadmium concentrations for 106–112 d, was examined in a flow-through stream channel using fathead minnows, Pimephales promelas, as prey. Five modes of foraging behaviour were observed and quantified (ending at fixate-orient; ending at approach and/or chase; ending at failed attack; ending at capture and loss; successful consumption). Each mode represented an increasingly progressive end-point from initial sighting of the prey to final consumption. Compared to controls., 0.5 g l^–1 Cd-exposed predators captured significantly fewer prey, while 5 g l^–1 Cd-exposed predators made fewer attacks. Both Cd-exposed groups consumed fewer prey than controls.     

Elevated carbon dioxide has the potential to impact alarm cue responses in some freshwater fishes

Freshwater fish behaviors have the potential to be impacted by acidification due to increases in dissolved carbon dioxide (CO₂). Recent work in the marine environment suggests that increased CO₂ levels due to climate change can negatively affect fishes homing to natal environments, while also hindering their ability to detect predators and perform aerobically. The potential for elevated CO₂ to have similar negative impacts on freshwater communities remains understudied. The objective of our study was to quantify the effects of elevated CO₂ on the behaviors of fathead minnows (Pimephales promelas) and silver carp (Hypophthalmichthys molitrix) following exposure to conspecific skin extracts (alarm cues). In fathead minnows, their response to conspecific skin extracts was significantly impaired following exposure to elevated CO₂ levels for at least 96 h, while silver carp behaviors were unaltered. However, fathead minnow behaviors did return to pre-CO₂ exposure in high-CO₂-exposed fish following 14 days of holding at ambient CO₂ levels. Overall, this study suggests there may be potential impacts to freshwater fishes alarm cue behaviors following CO₂ exposure, but these responses may be species-specific and will likely be abated should the CO₂ stressor be removed.     

Kinetics of alkaline phosphatase activity and phosphorus availability for phytoplankton and bacterioplankton in lake plu\see (North German Eutrophic Lake)

Annual studies of kinetics of alkaline phosphatase (APA) activity and phosphorus availability for microplankton in the photic zone of an eutrophic lake are reported. The total APA activity of microplankton varied strongly. V_max was highest during summer P depletion, and in autumn and winter total APA activity was low. The total APA specific activity of the microplankton was also highest (average 3.55 pmole PO₄ ^3– ng ATP^–1 min^–1) when ambient orthophosphate concentrations were very low. Both V_max and specific APA activity were not dependent on the biomass of microplankton; they were strongly affected by P available for microplankton. A differential filtration technique was used for separation of microplankton into two size classes, i.e., algal, larger than 3m, and bacterial fraction with size 0.2–3.0m. The algal size fraction had lower specific APA activity (average 1.224 pmole PO₄ ^3– ng ATP^–1 min^–1) and higher K_M values (38.8mole × liter^–1) than microorganisms which were smaller than 3m (2.011 pmole PO₄ ^3– ng ATP^–1 min^–1 and 25.4mole liter^–1, respectively). The K_M values of free, dissolved APA (36.8mole liter^–1) indicated that free APA was probably released by algae. Phytoplankton were major APA activity producers in the photic zone of the lake from March to November, and their activity constituted, on the average, 48.6% of the total APA activity in the water. Bacteria were the dominant APA activity producers in winter (41.3–44.9%); however, during other periods they contributed significantly (average 21.7%) to total APA activity. When surplus constituted less than 10% of particulate P in seston, phytoplankton produced high specific APA activity, and when surplus P was higher than 15%, the specific APA activity of phytoplankton size fraction rapidly decreased. APA of the bacterial size fraction of the seston was not affected by P concentrations. Orthophosphate was a competitive inhibitor of APA produced by microorganisms of the size fraction larger than 3.0m, and increasing concentrations of inorganic phosphate caused an increase in K_M values. The hypothetical metabolic-coupling between phytoplankton and bacterioplankton in the phosphorus cycle in conjunction with carbon metabolism in the lake is discussed.     

Effects of Boat Engine Noise on the Auditory Sensitivity of the Fathead Minnow, Pimephales promelas

Fishes are constantly exposed to various sources of noise in their underwater acoustic environment. Many of these sounds are from anthropogenic sources, especially engines of boats. Noise generated from a small boat with a 55 horsepower outboard motor was played back to fathead minnows, Pimephales promelas, for 2 h at 142 dB (re: 1 Pa), and auditory thresholds were measured using the auditory brainstem response (ABR) technique. The results demonstrate that boat engine noise significantly elevate a fish's auditory threshold at 1 kHz (7.8 dB), 1.5 kHz (13.5 dB), and 2.0 kHz (10.5 dB), the most sensitive hearing range of this species. Such a short duration of noise exposure leads to significant changes in hearing capability, and implies that man-made noise generated from boat engines can have far reaching environmental impacts on fishes.     

Assessing the efficacy of corn-based bait containing antimycin-a to control common carp populations using laboratory and pond experiments

Strategic use of oral toxicants could allow for practical and sustainable control schemes for the invasive common carp (Cyprinus carpio, or ‘carp’) if a toxicant selectively targeted carp and not native species. In this study, we incorporated antimycin-a (ANT-A), a known fish toxicant, into a corn-based bait and conducted a series of experiments to determine its toxicity, leaching rate, and species-specificity. Our results showed that ANT-A was lethal to carp at doses ≥ 4 mg/kg and that the amount of ANT-A that leached out of the bait in 72 h was not lethal to carp or bluegill (Lepomis macrochirus). Species-specificity trials were conducted in 227 L tanks, in which carp were stocked with three native species representing families that occur sympatrically with carp in our study region: the fathead minnow (Pimephales promelas), yellow perch (Perca flavescens) and bluegill. These trials showed high mortality of carp (46%) and fathead minnows (76%) but no significant mortality of perch or bluegill. Finally, a pond study, which used the same species composition except for fathead minnows, resulted in 37% morality among adult carp and no mortality among perch or bluegill. Our results suggest that corn-based bait that contains ANT-A could be used to selectively control carp in ecosystems dominated by percids or centrarchids, such as lakes across the Great Plains ecoregion of North America, where carp are especially problematic.     

Effects of fathead minnows and restoration on prairie wetland ecosystems

SUMMARY 1. Research has shown that fish influence the structure and processes of aquatic ecosystems, but replicated studies at the ecosystem level are rare as are those involving wetlands. Some wetlands of the Prairie Pothole Region (PPR) of North America support fish communities dominated by fathead minnows ( Pimephales promelas ) while others are fishless, providing an opportunity to assess the influence of these fish on wetland ecosystems. Additionally, many wetlands have previously been drained and subsequently restored, but the success of these efforts is poorly known and restoration may be impeded by the presence of fish.
2. We assessed the effects of fathead minnows and drainage by studying 20 semipermanent, prairie wetlands in Minnesota from 1996 to 1999. We used a 2 × 2 factorial design to examine the effects of presence and absence of minnows and drainage history (restored/never drained) on the abundance of aquatic invertebrates and amphibians, as well as on the concentrations of chlorophyll a , total phosphorus, total nitrogen and turbidity in the water column.
3. Results showed that fathead minnows are an important determinant of many biotic and abiotic characteristics of wetlands in the eastern PPR. Wetlands with fathead minnows had fewer aquatic insects, large- and small-bodied cladocerans, calanoid copepods, ostracods and larval tiger salamanders, as well as a higher abundance of corixids and greater turbidity and chlorophyll a . A higher concentration of phosphorus in restored basins was the only consistent effect of past management.
4. Fathead minnows usually dominate fish communities in eastern PPR wetlands where fish are present, and can have several strong ecosystem effects. While abiotic variables are important determinants of ecosystem structure in prairie wetlands, they can be strongly influenced by biotic factors.     

The uptake of Manganese-54 by green algae (Protococcoidal chlorella), Daphnia magna,and fathead minnows (Pimephales promelas)

Concentration factors (CF) of ⁵⁴Mn for three aquatic species: green algae (Protococcoidal chlorella), Daphnia magna, and fathead minnows (Pimephales promelas) were determined following direct exposure to the isotope in solution. The maximum accumulation (CF = 911) in P. chlorella was reached at 48 hours of exposure; the maximum uptake (CF = 65) in Daphnia was reached at 8 hours of exposure; and the maximum accumulation (CF = 22.6) in fathead minnows was at 128 hours of exposure. The data indicate that ⁵⁴Mn accumulation decreases with ascent up a theoretical aquatic food chain when water is the only source of contamination.     

Effects of exposure to predatory cues on territorial behaviour of male fathead minnows

We conducted a laboratory study to determine if male fathead minnows, Pimephales promelas, altered their territorial behaviour associated with reproduction in response to combinations of visual and chemical cues from northern pike, Esox lucius. We introduced the following stimuli to a territorial male: a brick (control), fathead minnow alarm pheromone, a pike fed brook stickleback, Culea inconstans, or a pike fed fathead minnow. The territorial behaviour of males did not change when the control was added. Male minnows experiencing threat from pike fed stickleback significantly reduced the frequency at which they performed three territorial behaviours, but, within 12 h, had returned to pre-exposure activity levels. Male minnows subjected to alarm pheromone alone and to pike fed fathead minnow significantly reduced their territorial behaviour, abandoned their nests, and did not return to pre-exposure levels of activity after 24 h. We suggest that because risk of predation triggers prolonged decreases in territorial defense, it may affect competition between nesting males and female mate choice. We conclude that fathead minnows can assess the severity of predatory threat and adjust their reproductive behaviour accordingly.     

Clinical applications of quantitative proteomics using targeted and untargeted data-independent acquisition techniques

Introduction: While selected/multiple-reaction monitoring (SRM or MRM) is considered the gold standard for quantitative protein measurement, emerging data-independent acquisition (DIA) using high-resolution scans have opened a new dimension of high-throughput, comprehensive quantitative proteomics. These newer methodologies are particularly well suited for discovery of biomarker candidates from human disease samples, and for investigating and understanding human disease pathways.

Areas covered: This article reviews the current state of targeted and untargeted DIA mass spectrometry-based proteomic workflows, including SRM, parallel-reaction monitoring (PRM) and untargeted DIA (e.g., SWATH). Corresponding bioinformatics strategies, as well as application in biological and clinical studies are presented.

Expert commentary: Nascent application of highly-multiplexed untargeted DIA, such as SWATH, for accurate protein quantification from clinically relevant and disease-related samples shows great potential to comprehensively investigate biomarker candidates and understand disease.     

Ability of chloramphenicol to suppress phenotypically some bacterial mutations

Summary Chloramphenicol (CLP) at slightly inhibitory concentrations (3–5 g/ml) suppresses the inhibition of DNA synthesis and cell division caused by the temperature sensitive mutation dnaE486 at the nonpermissive temperature. Some other mutations can also be phenotypically suppressed by CLP. A similar effect is shown by chlortetracycline. Phenotypic suppression is caused by both these drugs in different cases than by streptomycin.     

Homocysteine stimulates inducible nitric oxide synthase expression in macrophages: Antagonizing effect of ginkgolides and bilobalide

Hyperhomocysteinemia is an independent risk factor for atherosclerotic diseases. Inducible nitric oxide synthase (iNOS) is mainly expressed in macrophages upon stimulation. Overproduction of nitric oxide (NO) by iNOS can exacerbate the development of atherosclerosis. Our previous studies demonstrated that the extract of ginkgo biloba leaves (EGb) inhibited the iNOS-mediated NO production in monocyte-derived macrophage. We also reported that homocysteine could stimulate monocyte chemoattractant protein-1 (MCP-1) expression in vascular cells causing enhanced monocyte chemotaxis. The objective of the present study was to investigate the effect of homocysteine on iNOS-mediated NO production in macrophages and the antagonizing effect of EGb. Human monocytic cell (THP-1)-derived macrophages were incubated with homocysteine for various time periods. Homocysteine at concentrations of 0.05–0.1 mM significantly stimulated NO production and iNOS activity in macrophages via increased expression of iNOS mRNA and protein. The increased iNOS expression was associated with activation of nuclear factor-kappa B (NF-B) arising from reduced expression of inhibitor protein (IB) mRNA as well as increased phosphorylation of IB protein in homocysteine-treated cells. EGb and its terpenoids (ginkgolide A, ginkgolide B and bilobalide) could antagonize the homocysteine effect on iNOS expression in macrophages via their antioxidant effect resulting in attenuation of NF-B activation. Taken together, our results have demonstrated that homocysteine, at pathophysiological concentrations, stimulates iNOS-mediated NO production in macrophages. EGb and its terpenoids can antagonize such stimulatory effect via antioxidation and attenuation of NF-B activation.     

The role of experience and chemical alarm signalling in predator recognition by fathead minnows, Pimephales promelas

Young-of-the-year, predator-naive fathead minnows, Pimephales promelas , from a pikesympatric population did not respond to chemical stimuli from northern pike, Esox Indus , while wild-caught fish of the same age and size did. These results suggest that chemical predator recognition is a result of previous experience and not genetic factors, Wild young-of-the-year minnows responded to pike odour with a response intensity that was similar to that of older fish, demonstrating that the ability to recognize predators is learned within the first year. The intensity of response of wild minnows which had been maintained in a predator free environment for 1 year was similar to that of recently caught minnows of the same age, suggesting that reinforcement was not required for predator recognition to be retained. Naive minnows that were exposed simultaneously to chemical stimuli from pike (a neutral stimulus) and minnow alarm substance exhibited a fright response upon subsequent exposure to the pike stimulus alone. Predator-naive minnows exposed simultaneously to chemical stimuli from pike and glass-distilled water did not exhibit a fright response to the pike stimulus alone. These results demonstrate that fathead minnows can acquire predator recognition through releaserinduced recognition learning, thus confirming a known mechanism through which alarm substance may benefit the receivers of an alarm signal.     

Territrems: Naturally occurring specific irreversible inhibitors of acetylcholinesterase

Territrem B (TRB), a fungal metabolite isolated fromAspergillus terreus, potently and noncompetitively inhibited Electrophorus acetylcholinesterase (AChE EC 3.1.1.7), but had no inhibitory effect on horse serum butyrylcholinesterase (BtChE EC 3.1.1.8). The TRB-treated AChE did not recover its enzyme activity after either dialysis or dilution of the inhibited enzyme. The binding of [¹⁴C]TRB to AChE, but not to BtChE, was demonstrated. The concentrations of territrems required for 50% inhibition of AchE were: TRA 2.4 × 10^–8 M; TRB 1.9 × 10^–8 M; TRC 1.5 × 10^–8 M; TRA 9.8 × 10^–8 M; TRB 9.2 × 10^–8 M.     

Acetylcholinesterase activity in antennal receptor neurons of the sphinx moth Manduca sexta

Summary We have used a cytochemical technique to investigate the distribution of acetylcholinesterase (AChE) activity in the antenna of the sphinx moth Manduca sexta. High levels of echothiophate-insensitive (presumably intracellular) AChE activity were found in six different types of antennal receptors localized in specific regions of the three antennal segments of the adult moth. Mechanosensory organs in the scape and pedicel, the Böhm bristles and Johnston's organ, are innervated by AChE-positive neurons. In each annulus of the antennal flagellum, AChE-positive neurons are associated with six sensilla chaetica and a peg organ, probably a sensillum styloconicum. At least 112 receptor neurons (8–10 per annulus) innervating the intersegmental membranes between the 14 distalmost annuli also exhibit high levels of echothiophate-resistant AChE. In addition, each annulus has more than 30 AChE-positive somata in the epidermis of the scale-covered (back) side of the flagellum, and 4 AChE-positive somata reside within the first annulus of the flagellum. Since none of the olfactory receptor neurons show a high level of echothiophateresistant AChE activity, and all known mechanoreceptors are AChE-positive, apparently intracellular AChE activity in the antenna correlates well with mechanosensory functions and is consistent with the idea that these cells employ acetylcholine as a neurotransmitter.     

Reactivating and cholinolytic action of trimedoxime bromide at the neuromuscular junction of warm-blooded animals

The reactivating and cholinolytic action of trimedoxime bromide was evaluated during experiments on rat soleus and diaphragm muscles accoridng to the amplitude and time course of miniature end-plate potentials and currents (MEPP and MEPC respectively). This agent reactivates acetylcholinesterase (AChE) phosphorylation. The effects of trimedoxime bromide at concentrations of 5·10^–6–5·10^–4 M following AChE inhibition on the amplitude and duration of MEPP arises from complex interaction between the reactivating and cholinolytic effects. A separate evaluation of the reactivating effect (once the reactivating agent had been removed) revealed that this action increases throughout the entire range of trimedoxime bromide concentration: complete reactivation of AChE phosphorylation was observed under the action of 2–5·10^–4 M trimedoxime bromide. Examination of the cholinolytic effect in isolation (with voltage-clamping at the muscle and intact AChE) showed that blockade of open end-plate ionic channels underlies this effect. Reduction in MEPC amplitude together with retarded (but still exponential) decay of signals were distinguishing features of this blockade, confirming that trimedoxime bromide acts as a very fast blocker.S. V. Kurashov Medical Institute, Ministry of Public Health of the RSFSR, Kazan'. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 351–357, May–June, 1988.