Influence of Ca,pH and humic acid on Cd uptake

Summary Solution culture experiments were conducted to examine the effect of naturally occurring compounents of soil solutions such as Ca-ion, H-ion and organic acids on the Cd uptake of corn and snap beans. An increase in the Ca-ion concentration of solution cultures depressed the translocation of Cd from roots to tops of snap beans and corn but had no apparent deffect on the absorption of Cd by roots. Suppression of Cd translation by Ca was less marked for the corn than for the beans. No change in Cd absorption or translocation in corn was noted for solution pH values ranging from 4 to 7. Addition of humic acid to the solution decreased the Cd activity in soolution and the subsequent absorption of Cd by corn roots, indicating that Cd-ion activity in solution directly affectes Cd uptake. The addition of humic acid had no effect on Cd translation in corn plants.     

The effect of pH on the lability of lead and cadmium sorbed on humic acid particles

Abstract

Sorption of lead(II) or cadmium(II) ions on humic acid particles (at pH 3.5) yields surface complexes which are sparingly soluble in the pH 3.55 region. Interaction of these species with acetic acid or dilute nitric acid released ASV labile metal species (mainly hydrated metal ion). When the pH was adjusted between 4 and 7, increasing amounts of the metal humate species (and humic acid substrate) dissolved and low levels of ASV labile species were detected. Overnight interaction with an excess of acetate ions (0.01 M) led to higher lability values (attributed to acetate/humate ligand exchange). The percentage of labile metal ion detected in acetate solutions varied with the amount of metal ion initially sorbed (range 100 to 500 mmol g^?1). With the lower loadings, the ASV labile levels peaked in the pH 6–7 region (at around 12% of total sorbed cadmium, and 4% of total lead). In alkaline solutions, the percentage of labile Cd fell to about half of the peak value, but with Pb, lability values increased at pH > 8, due possibly to the formation of hydroxy complex species. The ASV lability of the Cd and Pb humates, and their 24 hour lability values (determined using a transfer to cation exchanger technique) has been compared with the behaviour of Cu and Zn humates (using similar conditions).     

Application of the biotic ligand model to predicting zinc toxicity to rainbow trout,fathead minnow,and Daphnia magna

The Biotic Ligand Model has been previously developed to explain and predict the effects of water chemistry on the toxicity of copper, silver, and cadmium. In this paper, we describe the development and application of a biotic ligand model for zinc (Zn BLM). The data used in the development of the Zn BLM includes acute zinc LC50 data for several aquatic organisms including rainbow trout, fathead minnow, and Daphnia magna. Important chemical effects were observed that influenced the measured zinc toxicity for these organisms including the effects of hardness and pH. A significant amount of the historical toxicity data for zinc includes concentrations that exceeded zinc solubility. These data exhibited very different responses to chemical adjustment than data that were within solubility limits. Toxicity data that were within solubility limits showed evidence of both zinc complexation, and zinc-proton competition and could be well described by a chemical equilibrium approach such as that used by the Zn BLM.     

Thermal acclimation in selected tissues of the fathead minnow, Pimephales promelas rafinesque

Environmental variables besides temperature such as length, weight, sex, and photoperiod were shown to affect the metabolic rate in gill and white muscle tissue. This required statistical adjustment to account for these factors. Oxygen consumption rates for gill tissue were greater following cold acclimation at all determination temperatures. This suggests thermal compensation had occurred. Metabolic rates for white muscle tissue showed inverse compensation between 7 °C and 15 °C, but little compensation was evident between 15 °C and 23 °C. Both gill and white muscle tissue had Q₁₀ values ranging between 1–00 and 2–00. These are lower than values previously recorded for fathead minnows.     

Effects of handling on endocrinology and reproductive performance of the fathead minnow

Anaesthesia with MS-222 followed by intra-peritoneal (ip) injection (with a 10% ethanol in corn oil carrier) of fathead minnow either as one or three (weekly) treatments did not affect survival, behaviour or secondary sexual characteristics of the fish. Fecundity of the fish, as indicated by fertility and hatching success, was also unaffected. Gonadal condition (relative gonad mass, histopathology) was not altered in either sex. Male and female plasma sex steroids (β;-oestradiol, testosterone, 11-ketotestosterone) and male vitellogenin concentrations were not significantly affected by the treatments. Females subjected to either ip treatment regime had significantly higher plasma vitellogenin concentrations than control females. However, based on previous data, this difference did not appear to be treatment-related. Overall, exposure of fathead minnows to chemicals via the ip route should not confound the interpretation of toxicity tests with potential endocrine disrupting chemicals.     

Copper homeostasis and toxicity in the elasmobranch Raja erinacea and the teleost Myoxocephalus octodecemspinosus during exposure to elevated water-borne copper

Clear nosed skate, Raja erinacea were exposed to 0.10 (control), 0.52 or 1.73 microM copper and sculpin, Myoxocephalus octodecemspinosus were exposed to 0.10 or 1.73 microM copper (as CuSO4) in Salisbury Cove seawater for up to seven days. Skate gill copper concentrations increased 40-50 fold over background in response to copper exposure at both concentrations. In comparison, sculpin gill levels only increased 3-fold. While there was no evidence for internalized copper in the skate arising from the water-borne exposure, sculpin kidneys, but not livers, exhibited elevated copper concentrations after the seven days of exposure. The marked difference in branchial copper accumulation between the skate and the sculpin likely explains why elasmobranchs appear to be more sensitive to metal exposure than most marine teleost fish. Brain tissue from both species and the skate rectal gland contained relatively high background copper concentrations. Copper exposure caused an initial transient reduction in skate plasma total ammonia (Tamm), but eventually led to elevated plasma Tamm. Despite the marked branchial copper accumulation in the skate, there was no reduction in gill Na/K-ATPase activity. Similarly, Na/K-ATPase activity in skate rectal gland and intestine, as well as in sculpin gill and intestine were not affected by copper exposure. Plasma sodium, magnesium and chloride were not affected by copper exposure in either the skate or the sculpin.     

Influence of L-lysine and zinc administration during exposure to lead or lead and ethanol in rats

Influence of lysine and zinc administration on the lead-sensitive biochemical parameters and the accumulation of lead during exposure to lead or lead and ethanol was investigated in rats. The lead exposure inhibited blood δ-aminolevulinic acid dehydratase (ALAD) activity, increased blood zinc protoporphyrin (ZPP), urinary δ-aminolevulinic acid (ALA), serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), blood and tissue lead levels, and decreased blood and hepatic glutahione (GSH) contents. Some of these effects were enhanced on coexposure to ethanol. The simultaneous administration of lysine and zinc reduced tissue accumulation of lead and most of the lead-induced biochemical alterations irrespective of exposure to lead alone or lead and ethanol. The depletion of endogenous calcium and magnesium owing to lead or ethanol exposure was also prevented by co-administration of lysine and zinc.     

Histological, histochemical and ultrastructural studies on the interrenal and chromaffin cells of the fathead minnow, Pimephales promelas Rafmesque

Light and electron microscopic examination of fathead minnow head kidneys revealed that the interrenal and chromaffin cells were intermingled and always closely associated with the cardinal veins and their tributaries. Histochemical tests for lipids in the interrenal cells were positive, and two types of chromaffin cells were indicated by chromaffin reactions. Interrenal cells contained abundant smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae, characteristic of steroid-producing cells. Only one interrenal cell type was found. Two types of chromaffin cells were present with differences in cytoplasmic density and in types of granules. In light cells, adrenaline granules were most common, and in dark cells noradrenaline granules predominated.     

Zinc effects on LDH, MDH and alkaline phosphatase from cultures of fathead minnow cells.

1. Three purported zinc metalloenzymes have been investigated from cell cultures of the fathead minnow (Pimephales promelas). 2. With the addition of increasingly higher concentrations of zinc to the tissue culture medium, the specific activity of LDH increased. 3. The results with MDH were equivocal. 4. The specific activity of alkaline phosphatase decreased in the presence of increasing amounts of zinc in the growth medium. 5. Zinc exogenously added to the LDH enzyme assay did not alter the LDH enzyme activity of cells grown without zinc.     

Effect of population density and feeding rate on the fathead minnow (Pimephales promelas)

Juvenile fathead minnows ( Pimephales promelas ) were stocked in tanks at different densities and different ration levels, in two experiments, to determine effects on final population density, growth and fecundity. Length and weight of fish increased with increased food availability. Egg size was exponentially related to growth and perhaps directly to ration level. High population density appeared to limit growth and gamete development regardless of food abundance. Additionally, water volume appeared to limit numbers (tolerance density) of fish which can be supported in a specific volume of water.     

Natural disturbance and life history: consequences of winterkill on fathead minnow in boreal lakes

Age, growth and reproductive characteristics of fathead minnow Pimephales promelas populations inhabiting four lakes that varied in the extent and frequency of winterkill were studied in the boreal region of western Canada. The lifespan of fathead minnows inhabiting lakes prone to winterkill was 1–2 years shorter than those in less disturbed lakes. In populations prone to winterkill, fish displayed faster growth rates and grew to a larger size‐at‐age, particularly during the first year of life. Although lower population densities in winterkill lakes probably contributed to this increased growth, adults in these populations tended to spawn earlier in the season than the smaller adults in more stable populations. Fathead minnows in lakes prone to winterkill also matured at an earlier age and allocated a greater proportion of their body mass to gonads than conspecifics in the more benign, stable lakes. These trends are consistent with predictions for organisms in variable, unpredictable environments and, because fathead minnows are tolerant to a wide range of environmental conditions, suggest that variation in life‐history traits among populations is probably a product of both selection and phenotypic plasticity.     

Aspects of basic reproductive biology and endocrinology in the fathead minnow (Pimephales promelas)

The fathead minnow (Pimephales promelas) has been proposed as a model species for assessing the adverse effects of endocrine-disrupting chemicals (EDCs) on reproduction and development. The purpose of these studies was to develop baseline reproductive biology and endocrinology data for this species to support interpretation of tests with potential EDCs. Pairs of reproductively-active fathead minnows (n=70) were evaluated with respect to reproductive cyclicity in terms of spawning interval and fecundity. The mode and mean (+/-SE) spawning intervals for the fish in this study were 3.0 and 3.7+/-0.1 days, respectively. The mean number of eggs produced per spawn was 85+/-2.8. Animals were sacrificed at periodic intervals during the established spawning cycle and measurements made of gonadal condition (gonadosomatic index [GSI], histopathology) and plasma concentrations of vitellogenin and sex steroids (beta-estradiol, testosterone, 11-ketotestosterone). The GSI in females varied significantly as a function of spawning interval, with the largest values occurring day 2 post-spawn, just prior to the interval of maximum spawning activity. Plasma beta-estradiol concentrations in females also varied significantly relative to peak values in the GSI and spawning activity. Vitellogenin concentrations in the female, and male GSI and steroid concentrations did not vary significantly relative to position in the spawning cycle. Concentrations of beta-estradiol in females and 11-ketotestosterone in males were positively correlated with testosterone concentrations.     

Effect of pH on domoic acid toxicity in mice

Domoic acid is a shellfish toxin which produces gastrointestinal distress, followed by neurological symptoms such as headache, confusion, disorientation and severe deficits in short-term memory. Domoic acid is an amino acid which contains three carboxylic groups, and one imino group, and its solubility, rate of absorption, and elimination would vary depending on the protonation of these groups at different pH's. We propose that domoic acid toxicity varies with pH of administered domoic acid solution. Domoic acid toxicity was measured in mice as the onset times for scratching behaviour, seizure activity, and death, after the intraperitoneal administration of domoic acid at different pH's. Results of the present study show that the scratching behaviour, seizure activity, and death, occurred at 12, 40, and 55 min, after intraperitoneal administration of domoic acid at pH 3.7. Apparently, the onset times for three types of behaviours were relatively long, and well separated from each ot her. Domoic acid toxicity was lowest at pH 3.7, and highest at pH 7.4, with intermediate toxicity at other pH's. The onset time of scratching behaviour was not influenced by pH of domoic acid solution at three different doses. In contrast, the onset times for seizure activity, and death were significantly affected by pH of domoic acid, toxicity being higher at pH 7.4 than at pH 3.7. The pH effect on domoic acid toxicity diminished as the dose of domoic acid was increased. In fact, at 14.5 mg/kg domoic acid toxicity was similar at both pH's of 3.7 and 7.4. It is concluded that in vivo toxicity of domoic acid varies depending on pH of the administered solution. The differential toxicity of domoic acid at different pH may be related to its solubility, rate of absorption, and elimination, depending on the degree of protonation of domoic acid molecule. Domoic acid toxicity would also vary depending on the age of animal, receptor sensitivity and density in different regions of brain. (Mol Ce ll Biochem 167: 179-185, 1997)     

光照对除虫菊素触杀毒力的影响

采用药膜法测定了不同光照条件下天然除虫菊素对桔小实蝇Bactrocera dorsalis (Hendel)成虫的触杀毒力,试图通过毒力的变化来明确除虫菊素用于防治桔小实蝇成虫的光稳定性.测定结果表明,天然除虫菊素在室内(平均光强25.00±0.53 KLux)条件下对桔小实蝇成虫仍表现出较好的触杀毒力,其LC50为3...     

The effects of temperature and dissolved oxygen on antioxidant defences and oxidative damage in the fathead minnow Pimephales promelas

Fathead minnows Pimephales promelas maintained at 25° C for 6 h had significantly higher superoxide dismutase (SOD) activity than fish maintained at 7 or 32° C, but hypoxic conditions (3 mg l^?1 O₂) over the same time period did not affect SOD activity. Fish in better body condition (length‐adjusted mass) had higher SOD activity. In a separate experiment, P. promelas maintained at three water temperatures (7, 23 and 32° C) for 31 days did not differ in liver acrolein, a biomarker of oxidative stress.     

Impact of nest substrate limitations on patterns of illegitimacy in the fathead minnow, Pimephales promelas (Cypriniformes: Cyprinidae)

The fathead minnow (Pimephales promelas) is a nest-building North American cyprinid that spawns multiply and exhibits exclusive male parental care. Here, we examined the effects of nest substrate availability on the genetic mating system in 2 natural populations from the glacial pothole region of eastern South Dakota. The sites differed dramatically with respect to the type and density of available nest substrate. Substrate effects were examined by comparing the percentage and distribution of illegitimate offspring between the 2 sites. A total of 1338 embryos from 42 nests (21 from each site) were genotyped at 4 or 5 microsatellite loci. Bimodally distributed frequencies of illegitimate offspring occurred in the nests of guardian males from both sites and indicate the presence of nest takeovers as well as previously undocumented alternative reproductive tactics. As predicted, the rate of usurped nests, a previously documented behavior, was higher in the nest substrate-limited population; furthermore, males were significantly larger here and acquired more mates, suggesting a difference in sexual selection regime. Although these results are based on a single comparison between 2 sites, the results are intriguing and provide a foundation for future studies.     

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.