Increase In Lead Concentration Research Articles

Effect of lead treatment on the stipe and leaflet anatomy of Pteris vittata and Pityrogramma calomelanos (Pteridaceae: fern)

The effect of various concentrations of Lead on stipe and leaflet anatomy of Pteris vittata and Pityrogramma calomelanos were investigated. Fernlets were transplanted into 5 kg pots of soil pre-treated with five different concentrations of Lead, adequately watered and arranged in a complete randomized design in the screen house. Pots with no Lead treatment served as control. At twelve weeks after planting, plants were carefully removed, washed and taken to the laboratory. Anatomical sections of leaflets and stipe of each of the treatments were carried out with a sledge microtome (10-15 μm). Microscopic observations of structures were made after staining the sections. In Pteris vittata, the thickness of the cuticle of the stipe increased with increasing Lead concentrations but the reverse of this was observed in Pityrogamma calomelanos. There was also significant reduction of epidermal and mesophyll cell area of both species with increasing Lead concentrations. It can be concluded from this study that P. vittata has a higher tolerance level to Lead than Pityrogramma calomelanos.
 Key words: Anatomy, Cuticle thickness, Ferns, Lead, Pteridaceae.

Physicochemical changes of lead(II) contaminated sand–clay mixture

In this study, the influence of lead nitrate as a hazardous environmental pollutant was studied through experimental tests to assess its physicochemical effects in soils. Artificially contaminated soil specimens were prepared using sand and two kinds of clays. Direct shear, consolidation, electrical resistivity and unconfined compression tests were conducted. In addition, the influence of lead cation on atterberg limits, pH and particle size distribution of soils was evaluated. Overall, the presence of lead ion in mixtures including bentonite increased the shear strength due to a flocculated structure and replacement of sodium cations by hydrogen ions which is along with the reduction of double-layer thickness. However, due to the broken bonds and rearranging of kaolinite particles to a weaker form, the strength of sand–kaolinite mixtures decreased with the increase of lead concentration. Based on the obtained results, with the addition of lead concentration, the compression index and electrical resistivity of all specimens decreased. Due to the acidic nature of positively charged lead cations, pH of the specimens directly affected and tended to a more acidic range. These findings indicate that the presence of lead ion improves the strength of some kinds of soils including bentonite and decreases the strength parameters of soils with kaolinite.

EUTROPHICATION AND POLLUTION DEVELOPMENT IN THE DANUBE RIVER AND COASTAL MARINE ZONE SYSTEM

Since the 1970s, the process of anthropogenic water euthrophication and the near bottom hypoxia linked with it, have caused widespread benthos fauna mortality. In addition to this negative phenomenon a lot of contaminations and pollutants are washed out from the fields and the coastal urban agglomerations by the river flow. In the process of sedimentation, the suspended matter is accumulated in the bottom sediments. It reinforces negative changes in benthic habitat conditions. One of the main modern problem is eutrophication and pollution (waste) in rivers, lakes and coastal marine systems. It illustrates the development of eutrophication and waste in a large, deep lake, together with the impacts on the lake and marine ecosystems. The Object of investigation is the Danube mouth area. The Subject of investigation is euthrophication processes and pollution input development in aquatic system. The Danube river extends almost all over Central Europe, which means that any waste from factories located directly near the Danube will inevitably get there. Therefore, the phenomenon of "water bloom" and periodic environmental disasters on the Danube are natural consequences of human activities. The level of pollution of the bottom sediments in the Northwest shelf of the Black Sea is examined. Modern data are compared with those of the late 20th century and their variability over 20 years. Substantial increase (by two orders) of copper, lead and nickel concentration has been marked. The diverse of contamination sources in larger catchment areas usually produce a mixture of pol­lutants, which is more difficult to treat than an industrial waste. For most sediments, there are more arguments in favor of disposal rather than treatment. Mechanical separation of the less contaminated fractions could be a useful step prior to the final stor­age of the residues. To improve the status of surface water bodies in the management area, it is necessary to take into account and reduce all existing factors and risks of deterioration of water quality. Environmental issues and the science behind them are of great public concern. Water management issues are also of critical importance. Human impacts within the river – delta –sea system are environmental contamination with nutrients, heavy metals, organic compounds, etc., degrading water and sediment quality and leading to toxic impacts in biota, airborne pollution. Human impacts from outside of the wetland are lack of catchment scale management of land use upstream, leading to soil erosion and sedimentation.

Biosorption of Lead Using the Bacterial Strain, Bacillus subtilis (MTCC 2423)

Lead removal efficiency of the bacterial strain, Bacillus subtilis (MTCC 2423) was tested with 200, 400, 600, 800 and 1000 ppm of lead in minimal broth for a period of ten days. Samples were tested for the level of lead every two days in each concentration and maximum removal was observed after six days of treatment. With the increase in lead concentration, both biomass and lead removal efficiency showed an increase. When tested with immobilized, dead and live cells, maximum removal was observed for immobilized cells. Among the sugars tested, monosaccharide sugars enhanced the biomass of B. subtilis during lead treatment and the results are discussed.

Water quality of runoff from flat panel display glass concrete during modified accelerated aging plus leaching tests.

Flat panel display glass (FPDG) from plasma televisions is difficult to recycle due to their heavy metal composition. When crushed, flat panel display glass has similar physical properties to sand and could be used as a recycled aggregate in concrete, if the potentially harmful metals in FPDG can be encapsulated. To replicate leaching from environmental exposure, at periodic points during freeze-thaw tests, samples of concrete with 0%, 10%, and 20% FPDG were exposed to simulated rainwater and the runoff water was analyzed. For the metals detected (arsenic, barium, chromium, and lead), lead concentrations in the leachate/runoff from 20% FPDG samples exceeded the acute ambient water quality criteria after approximately 50-60 cycles; however, no samples exceeded the toxic characteristic leaching procedure limits at any point during freeze-thaw testing. Increases in lead and chromium concentrations over time indicate a need for stabilization, especially since lead exceeded the acute water quality criteria. PRACTITIONER POINTS: TCLP results indicate flat panel display glass is not expected to release RCRA-8 metals at or above regulatory limits. Accelerated aging-leaching tests indicate lead might be released at levels approaching or exceeding the acute ambient water quality criteria. With additional lead stabilization, this study shows flat panel display glass has the potential to be used in concrete.

Impacts of Using Mineral Fertilization Combined with Sewage Sludge in the Amendment of Luvisol on Oat Crop. II. Influence on Metal Accumulation

The objective of the present paper was to investigate the effects of sewage sludge application on metals (Cu, Mn, Zn, Cd, Co, Pb) accumulation in oat (Avena sativa L.) grains, Somesan variety. It were used various doses of sewage sludge corresponding to equivalent doses of 0-600 kg N/ha associated or not with NPK mineral fertilization. The results evidenced that copper and zinc levels in oat grains increased significant with sewage sludge fertilization starting with a dose equivalent with 200 kg N/ha. Mineral fertilization led to significant decrease of copper content in comparison with sewage sludge treatments only. For manganese, fertilization with sewage sludge has produced a significant decrease, this trend being accentuated up to the equivalent dose of 300 kg N/ha. For cadmium, application of sewage sludge in an equivalent dose of 200 kg N/ha led to concentrations in oat grains higher than 1 mg Cd/kg (imposed limit for grains used for animal feed). This behavior is a consequence of high cadmium content of sewage sludge (of 7.2 times over maximum admitted limit). Cobalt contents of oat grains increased with sewage sludge doses, but the levels are between normal values and concordant with literature data. Application of sewage sludge in an equivalent doses of 500 and 600 kg N/ha generated a significant increase of lead content in oat grains, average values being 1.87 and 2.17 mg Pb/kg, respectively.

Relationship between low-level lead, cadmium and mercury exposures and blood pressure in children and adolescents aged 8–17 years: An exposure-response analysis of NHANES 2007–2016

This study investigated whether low-level blood and urinary lead, cadmium and mercury exposures were associated with blood pressure (BP) in children and adolescents. Data from National Health and Nutrition Examination Survey (NHANES) between 2007 and 2016 for children and adolescents aged 8–17 years (n = 7076) were analyzed. Outcome variables were systolic BP, diastolic BP and high BP status. High BP was defined as: self-reported antihypertensive medication usage or a diagnosis of hypertension; classified as having elevated BP/hypertension according to 2017 AAP guidelines. Multivariable linear and logistic regressions models were performed and stratified by race/ethnicity and gender. Blood lead was negatively associated with diastolic BP among blacks, and positively associated with diastolic BP among whites. For a two-fold increase of blood lead concentration, the change in diastolic BP was −1.59 mm Hg (95% CI: −3.04 to −0.16 mm Hg) among blacks and 1.38 mm Hg (95% CI: 0.40 to 2.36 mm Hg) among whites. No significant associations between either systolic BP or diastolic BP with urinary lead were observed. The inverse associations between blood lead and high BP were found in females, Mexican Americans and other Hispanics. No associations between blood cadmium and BP were observed, except in other Hispanics. Urinary cadmium levels were inversely correlated with systolic BP, diastolic BP and high BP in all participants and in men. When compared to the lowest quartile of urinary cadmium levels, participants with a urinary cadmium level ≥ 0.12 μg/L had 0.48 (95% CI: 0.29–0.78) times and 0.53 (95% CI: 0.30–0.94) times reduced odds of having high BP in all participants and in men, respectively. No associations between either blood mercury or urinary mercury with systolic BP were observed. Significant inverse associations were found between blood total mercury and methyl mercury with diastolic BP in all participants and in men. Future prospective studies are warranted to confirm these findings.

Lead concentrations in blood from incubating common eiders (Somateria mollissima) in the Baltic Sea

Here we investigate if lead may be a contributing factor to the observed population decline in a Baltic colony of incubating eiders (Somateria mollissima). Body mass and blood samples were obtained from 50 incubating female eiders at the Baltic breeding colony on Christiansø during spring 2017 (n = 27) and 2018 (n = 23). All the females were sampled twice during early (day 4) and late (day 24) incubation. The full blood was analysed for lead to investigate if the concentrations exceeded toxic thresholds or changed over the incubation period due to remobilisation from bones and liver tissue. Body mass, hatch date and number of chicks were also analysed with respect to lead concentrations. The body mass (mean ± SD g) increased significantly in the order: day 24 in 2018 (1561 ± 154 g) < day 24 in 2017 (1618 ± 156 g) < day 4 in 2018 (2183 ± 140 g) < day 4 in 2017 (2359 ± 167 g) (all p < 0.001). The lead concentrations increased significantly in the opposite order i.e. day 4 in 2017 (41.7 ± 67.1 μg/L) < day 24 in 2017 (55.4 ± 66.8 μg/L) < day 4 in 2018 (177 ± 196 μg/L) < day 24 in 2018 (258 ± 243) (all p < 0.001). From day 4 to 24, the eider females had a 1.33-fold increase in blood lead concentrations in 2017 and a 1.46-fold increase in 2018. Three of the birds (13%) sampled in 2018 had lead concentrations that exceeded concentrations of clinical poisoning (500 μg/L) and eleven (48%) had concentrations that exceeded the threshold for subclinical poisoning (200 μg/L). In 2017, none of the birds exceeded the high toxic threshold of clinical poisoning while only one (4%) exceeded the lower threshold for subclinical poisoning. Three of the birds (6%) sampled in 2018 had lead concentrations that exceeded those of clinical poisoning while 12 birds (24%) resampled in both years exceeded the threshold for subclinical poisoning. In addition, lead concentrations and body mass on day 4 affected hatch date positively in 2018 (both p < 0.03) but not in 2017. These results show that bioavailable lead in bone and liver tissue pose a threat to the health of about 25% of the incubating eiders sampled. This is particularly critical because eiders are largely capital breeding which means that incubating eiders are in an energetically stressed state. The origin of lead in incubating eiders in the Christiansø colony is unknown and it remains an urgent priority to establish the source, prevalence and mechanism for uptake. The increase in lead from day 4 to day 24 is due to bone and liver remobilization; however, the additional lead source(s) on the breeding grounds needs to be identified. Continued investigations should determine the origin, uptake mechanisms and degree of exposure to lead for individual birds. Such research should include necropsies, x-ray, lead isotope and stable C and N isotope analyses to find the lead sources(s) in the course of the annual cycle and how it may affect the population dynamics of the Christiansø colony which reflects the ecology of the Baltic eiders being suitable for biomonitoring the overall flyway.

Remedial ability of maize (Zea-Mays) on lead contamination under potted condition and non-potted field soil condition

This study presents the remedial ability of maize on lead (Pb) contaminated soil. Soil samples were collected randomly from the site and subjected to physico-chemical tests before experimentation. The samples were contaminated artificially at six different concentration levels of lead nitrate (Pb(NO3)2). Experimental design was 4-factorial combination (6 × 6 × 2 × 1). The study duration was 10 weeks, and during this period, Pb contents of the soil were analyzed in intervals of two weeks. Analyzed physico-chemical properties of the soil showed that the soil was loamy with pH 6.82, electrical conductivity 1.62 dS/m and adequate macro nutrient elements. The average percentage removal of Pb from the soil was 2.25% and 3.67% for potted and non-potted experiments, respectively. Similarly, the average percentage of Pb in the roots was 1.10% and 1.68% for potted and non-potted experiments, respectively. The result of this study indicated that extraction of Pb by the plant system increased with the increase of lead concentration in the soil as well as in the extent of vegetation attained by the crop. It also clearly showed that the non-potted experiments demonstrated greater influence on removal of Pb from the soil system than the potted experiments.

Effects of Lead and Gasoline Contamination on Geotechnical Properties of Clayey Soils

ABSTRACTVarious laboratory tests were carried out to study the effects of lead and gasoline on the geotechnical properties of three kinds of contaminated soil. This paper addresses soils contaminated with lead, gasoline, and lead-gasoline. This work aimed to investigate the critical alterations in geotechnical properties of an artificial soil (MDD: 17.6 kN/m3) due to these contaminants ‘ simultaneous application. For this purpose, soil samples were prepared with several lead contents (1000, 2000, 5000, 10000, 20000 ppm) and different gasoline contamination percentages (the 3%, 6% and 9% weight of dried soil) with the 4 days contamination duration. The tests conducted were: compaction, permeability, direct shear test, unconfined compressive strength, X-ray diffraction, and SEM analysis. The results indicated increment in maximum dry density and internal friction angle with the increase in the amount of lead and gasoline in all types of samples. The growth in maximum dry density was higher with gasoline than lead contamination. Also, by increasing lead content in contaminated samples the values of cohesion and hydraulic conductivity increase while a reverse trend was observed with the climb in gasoline content. Furthermore, Lead-gasoline contaminated samples show a peak behavior for both unconfined compressive strength and failure strain by an increase in pollution content.

The Effects of Lead Toxicity on the Hematological Parameters Common Carp (Cyprinus carpio) at Varying Salinity Levels

Background: Lead (Pb) is an important metal used in industries, mining and agriculture. It is equally important to the aquatic ecosystems and has negative impact on the health of aquatic organisms. Methods: The LC50 of lead toxicity at varying salinities was first determined for 96 hours. Then juvenile fish were transferred to tanks individually and were exposed to 0, 15, 30, 60 and 120 mg/l of Pb at varying salt concentration of 0, 0.1, 0.2 or 0.4 g/l. The blood samples were taken after the 4th day and the hematological parameters were evaluated. Results: Red Blood Cells (RBC) and White Blood Cells (WBC) were decreased in almost all lead treated groups. The Hb levels decreased consistent with increasing lead concentrations (P&lt;0.05). The mean corpuscular volume, hemoglobin and the concentration were not affected by the lead concentrations compared to those for the control group. The WBC and RBC counts showed an inverse correlation with the lead concentrations in the Pb-exposed fish. A direct correlation was also observed in the lead concentration and the heterophile rate (P&lt;0.05). Conclusion: The results showed that salinity did not affect the hematological parameters, but the LC50 values decreased with increasing salinity.

The Ability of Phosphate To Prevent Lead Release from Pipe Scale When Switching from Free Chlorine to Monochloramine.

For lead pipes that contain PbO2(s) as a major component of their scales, a change in the residual disinfectant from free chlorine to monochloramine can destabilize the PbO2(s) and result in dramatic increases in aqueous lead concentrations. Such a scenario occurred in Washington, D.C., in late 2000. That problem was ultimately addressed by the addition of phosphate as a corrosion inhibitor, but it took several months for lead levels to drop below regulatory values. This study sought to determine whether adding phosphate prior to switching the disinfectant could mitigate lead release. Using synthetic tap water and new lead pipes, we developed a set of lead pipes with scales rich in PbO2(s) and then studied their response to a change from free chlorine to monochloramine. Total lead concentrations remained below 10 μg/L for pipes that received phosphate prior to and during the switch. In contrast, total lead concentrations increased from less than 5 μg/L to more than 150 μg/L as a result of the disinfectant switch when phosphate was not present. Characterization of the pipe scales demonstrated that plattnerite (β-PbO2(s)) was the dominant component of the scale prior to the switch, and that the scale gradually transformed into one containing a lead phosphate solid chemically similar to phosphohedyphane (Ca2Pb3(PO4)3(Cl,F,OH)(s)) when phosphate was present.

Puberty and resultant increased bone turnover as a possible etiology of an increased lead concentration in a pre-adolescent girl

Introduction: We present a case in which puberty likely resulted in an increased lead concentration in a pre-adolescent girl.Case report: A 12-year-old girl was referred to the pediatric environmental health clinic (PEHC) after her blood lead level (BLL) was found to be elevated to 30 µg/dL (reference <5 µg/dL). She had been seen in the PEHC 6 years previously for management of a BLL as high as 36 µg/dL. Fifteen months prior to her repeat PEHC referral, her BLL had been 10 µg/dL. In those intervening 15 months, she grew 10.42 cm. Thyroid studies were normal. Four months after re-referral, her osteocalcin concentration, a marker of bone turnover, was 212 ng/mL (normal 9–42 ng/mL in adults >18 years); 10.5 months after the peak BLL of 32 mcg/dL, her BLL was 16 µg/dL, osteocalcin was 69 ng/mL, and her rate of growth had declined to 0.20 cm/30 days (peak: 1.07 cm/30 days). No external source of her exposure was found.Discussion: Osteocalcin concentrations and plotting the changes in growth velocity over time may assist clinicians in determining if pubertal growth is playing a role in unexpectedly increased BLL discovered in adolescents for whom no external source of lead exposure can be found.

The effect of the state of “loaded metabolism” assesses the level of lead in the productivity of dairy cows

Annotation. The study was performed on clinically healthy cows of Holstein breed during the period of milking in the CJSC "Gatchina" of the Leningrad region (Russia). Animals (n = 60) were divided into groups depending on the severity of "loaded metabolism" estimated by lead concentration in wool: up to the 25th centile, within the 25th to 75th centile, above the 75th centile. The concentration of lead in wool was determined by atomic emission and mass spectrometry (AES-ICP and MS-ICP). It was found that about the increase in lead content from the minimum to the maximum in centile intervals from 25-75 to> 75, the level of malondialdehyde (Total-MDA) in the blood increased, which was recorded against the background of a decrease in milk productivity. A significant negative correlation was observed between the concentration of lead in wool and the yield of milk fat, protein, dry matter, and corrected for 1% milk fat.

Short communication: Anatomical changes in the roots, rhizomes and leaves of seagrass (Cymodocea serrulata) in response to lead

Abstract. Rosalina D, Herawati EY, Musa M, Sofarini D, Risjani Y. 2019. Short communication: Anatomical changes in the roots, rhizomes, and leaves of seagrass (Cymodocea serrulata) in response to lead. Biodiversitas 20: 2583-2588. Runoff of heavy metals as a result of urban and industrial development is a potential threat for seagrass populations in the coast. The objectives of this study were to study the anatomical changes in the tissues of roots, rhizomes, and leaves of seagrass Cymodocea serrulata in response to treatment with different concentrations of lead (Pb) for different time durations. This experiment used heavy metal Pb from a solution of Pb (NO3)2-with a concentration of 0 ppm, 5 ppm, 10 ppm, and 15 ppm and the treatment period extended up to 4 weeks with 3 replications. Analysis of changes in anatomical features showed that exodermis and endodermis cells in the roots thickened as lead concentration increased. The air spaces in the root cortex and rhizome also widened. Thickening of cell walls occurred in the epidermis and endodermis of rhizome. Likewise, in the leaves, thickening occurred in the upper and lower cuticle and also the upper and lower epidermis. In general, changes in anatomical features of root, rhizome, and leaves were observed in response to increasing lead concentrations. The results showed that C. serrulata developed some level of tolerance to heavy metals, especially lead.

Airborne lead dust concentration in Townsville, Queensland is associated with port activity and may contribute to estuarine sediment contamination

Australia has a history of overlooking heavy metal contamination in towns and water bodies that can impact on human and environmental health. Airborne lead pollution in many regional Australian towns is often related to mining, smelting and transport of minerals. Recent studies in Townsville have shown inner city soil and playgrounds, creek and nearby off-shore sediment to have heavy metal concentrations that exceed Australian standards; this contamination is suspected to originate from the port. To assess the port as a current source of lead dust, we evaluated one year of data in 2015-2016 on lead concentration in air from the Department of Environment and Heritage Protection continuous metals monitoring station. The analysis shows that when the wind direction is from the port, and ships are present at the berth where the lead and zinc concentrates are loaded, there is a significant increase in lead concentration. This suggests that shipping activity at the port continues to be the source of lead-laden dust in inner Townsville and in estuarine and coastal marine sediments. The sediments have the highest concentration of lead in Ross Creek, southwest of the port. The geographical relationship between the port, metal analyser and the creek relative to the northeast winds, the latter being directly downwind, suggest that the Ross creek and metal monitoring station have the same source of lead contamination. Our results indicate lead testing in people and wildlife in the area may be warranted to directly assess risks, and that remedial action should continue to focus on reducing escape of lead dust from the port.

Serum levels of Some metals (iron, magnesium, zinc and lead) in patients with chronic otitis media and its association with cholesteatoma formation

ABSTRACT The association between middle ear diseases and metals serum levels in adult population is not well studied. So, the aim of this study was to estimate the serum levels of some metals (iron, magnesium, zinc and lead) in patients presented with chronic otitis media, and find if there is possible link with cholesteatoma formation or not. Patients and methods: This study was a across-sectional prospective study; conducted on 59 patients with chronic otitis media from ear, nose and throat department of Al-Azhar University Hospital (New Damietta) from January 2018 to December 2018 compared to the same number of age matched healthy controls. Serum iron, zinc, magnesium and lead levels were estimated to all patients and the healthy controls. Results: There was significant decrease of serum iron, magnesium and zinc while serum lead level was significantly increased in the patient’s group as compared to the healthy controls. Cholesteatoma was found in 18 (30.5%) of the patient’s group. There was significant decrease of magnesium and significant increase of lead concentrations in patients who developed cholesteatoma. In addition, at the lead cut off values of 10µg/dl, cholesteatoma was more common in patients with high lead concentration. Conclusions: The results of this study showed that there were significant differences among patients and control and groups according to the studied metals levels. Serum levels of magnesium lead may play a role in the development of cholesteatoma. Recommendation: It is recommended to measure at least magnesium and lead levels in chronic otitis media patients and to add lead chelating agents, antioxidant and anti-inflammatory drugs with the antibiotics for its treatment ,which could decrease free radical induced inflammatory alterations and prevent complications of otitis media. Further studies are required to ascertain the associations between the studied metals and the development of cholesteatoma.

Influence of various concentration of lead on consolidation parameters of bentonite

ABSTRACT Influence of concentrations of lead (Pb2+) on consolidation behaviour of bentonite was investigated. Various parameters such as coefficient of consolidation (cv ), coefficient of volume change (mv ), time for 90% of consolidation (t90) and compression index (Cc ) and Swelling potential and swelling pressure in the presence of the various lead concentration ranging from 250 to 1000 mg/L. The results manifested that with the increase in lead concentration, the swelling pressure, swelling potential and cv increased; however, Cc, mv and t90 of the bentonite decreased. A decrease in diffuse double layer (DDL) thickness as the Pb2+ gets adsorbed by bentonite is responsible for the change in these parameters. The results show that the impact of Pb2+ on bentonite was more dominant at higher concentration. Results also revealed that with the rise in vertical consolidation pressure, t90 increased, whereas cv decreased. However, mv increased initially and then decreased after reaching a peak value.

The effects of lead on ATPase activity in liver of Pelophylax nigromaculata

Lead is a major heavy metal in sewage, which affects the growth, development, reproduction, endocrine and blood circulation of aquatic animals. The effects of lead on the activity of ATPase in liver of Pelophylax nigromaculata were studied. In vitro experiment, the grinding fluid of the liver of P. nigromaculata was mixed with the equal proportion of 0, 0.1, 10, 100, 1000 and 10000 ug/L lead. In vivo experiment, the liver was treated with 0, 10, 100 and 1000 g/L of lead for 30 d. The absorbance of the liver was measured by ATPase kit with enzyme labeling instrument and ATPase activity of the liver was calculated according to the formula. In vitro experiments, compared with the control group, the activity of ATP enzyme in lead treated group decreased significantly (p<0.05). With the increase of lead concentration, the activity value showed a fluctuating trend of first decreasing and then rising and then falling, and the activity value of 10 μg/L ATP in treatment group decreased most (p<0.05). With the increase of Pb concentration, the activity of ATP decreased first and then increased, and there was a significant difference among the treatment groups (p<0.05). The activity of 100 μg/L ATP decreased most in the treatment group. The results showed that lead treatment inhibited the activity of ATP enzyme in the liver of P. nigromaculata.

Lead exposure-induced cognitive impairment through RyR-modulating intracellular calcium signaling in aged rats

Lead is widely distributed in the environment and has become a global public health issue. It is well known that lead exposure induces not only neurodevelopmental toxicity but also neurodegenerative diseases, with learning and memory impairment in the later stage. However, the molecular mechanisms remain elusive. The present study investigated the effects of early life and lifetime lead exposure on cognition and identified the molecular mechanisms involved in aged rats. The results herein demonstrated that the lead concentration in peripheral blood and brain tissues in aged rats was significantly increased in a lead dose-dependent manner. High-dose lead exposure caused cognitive functional impairment in aged rats, concomitant with a longer escape latency and a lower frequency of crossing the platform via Morris water maze testing compared to those in the control and low-dose lead exposure groups. Importantly, neuron functional defects were still observed even in early life lead exposure during the prenatal and weaning periods in aged rats. The neurotoxicity induced by lead exposure was morphologically evidenced by a recessed nuclear membrane, a swollen endoplasmic reticulum, and mitochondria in the neurons. Mechanistically, the exposure of aged rats to lead resulted in increasing free calcium concentration, reactive oxygen species, and apoptosis in the hippocampal neurons. Lead exposure increased RyR3 expression and decreased the levels of p-CaMKIIα/CaMKIIα and p-CREB/CREB in the hippocampus of aged rats. These findings indicated that early life lead exposure-induced cognition disorder was irreversible in aged rats. Lead-induced neurotoxicity might be related to the upregulation of RyR3 expression and high levels of intracellular free calcium with increasing lead concentration in injured neurons.