Fifth Day Of Exposure Research Articles

Toxicity, Antibacterial, and Phytochemical Analyses of Antrocaryon klaineanum Pierre Extracts.

Medicinal plants are traditionally used in Gabon to treat several types of illnesses. The study's purpose was to determine the toxic, antibacterial, and anti-inflammatory effects of Antrocaryon klaineanum Pierre extracts and to characterize their phytochemical compounds. Toxicity was evaluated on frog tadpoles (Phrynobatrachus africanus Hallowell). The microorganism susceptibility test was performed by the diffusion method, while minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated using the microdilution technique. Anti-inflammatory activity was tested through protein denaturation and membrane stabilization methods. Chromatography and molecular network techniques were used to characterize chemical compounds. The lethality test showed that the lethal concentration (LC50) increased from 110.03 ± 1.25 to 15.86 ± 2.21 μg/mL after 24 and 96 hours of exposure. In tadpoles exposed to 7.81 μg/mL extract, the first mortalities (12.5%) were observed on the fifth day of exposure. A relative decrease in mature erythrocytes exposed to plant extracts was observed. The antibacterial activity shows that the Ak F2, Ak F3, and Ak F4 fractions (from the water-ethanol crude extract) gave the greatest antibacterial activities compared to the other extracts. The water, water-acetone, and water-ethanol extracts showed good inhibition of denaturation. The haemolysis test shows that the extracts exhibited good anti-inflammatory activities. Phytochemical characterisation revealed four major compounds, including monogallate epicatechin and hydroxy-ergostadian. The molecular network revealed five main clusters. Our study shows that A. klaineanum Pierre could be a promising natural product for the isolation of molecules with potential biological activities.

Laccase Production Under Optimized Parameters by Aspergillus oryzae, an Endophytic Fungus and their Application to Waste Water Treatment

Objective: To isolate an endophytic fungal laccase producer from the Ziziphus mauritiana plant leaves in the surroundings of paper mill effluents and to study its role in the decolorization of synthetic dyes, removal of COD and phenol from industrial effluents. Methods: Laccase-producing endophytic fungi were isolated and screened by using an agar plate method. The positive isolates were identified, and laccase activity was determined by using spectrophotometric methods to monitor the oxidation of guaiacol and optimizing various parameters affecting laccase production. The molecular mass of the purified laccase enzyme was determined by using 12% SDSgel electrophoresis. Industrial effluents were treated with laccase to remove phenol, decolorize dyes, and reduce chemical oxygen demand. For the analysis, a spectrophotometric method was employed. Findings: One of the most effective endophytic fungal isolates, Aspergillus oryzae, was screened as a maximum laccase producer. The optimal pH of 6, temperature of 35 oC, inoculation period of 8 days, and the inoculum number of 3 discs/100 ml of Czapek Dox Broth in submerged culture were determined for the maximum laccase production. Sucrose and sodium nitrate, as carbon and nitrogen sources, considerably assisted laccase production. The molecular weight of the isolated laccase from A. oryzae was 66 kDa. The greatest activity was determined to be 64.2 U/mL, which is two times more than under unoptimized conditions. After the fifth day of exposure, the A. oryzae laccase decolorizes the synthetic dyes Bromophenol blue, Congo red, Methyl orange, and Phenol red.Chemical oxygen demand and phenolic pollutants’ clearance rates were 38–43% and 60% from coal and textile effluents during their exposure times, respectively. Novelty: A. oryzae was discovered to be a potent natural laccase producer endophytic fungus from paper mill effluents, which may be used for decolorizing non-textile dyes, treatment of various industrial effluents, and other industrial purposes. Keywords: Endophytic Fungi; Aspergillus oryzae; Laccase; Chemical oxygen demand; Synthetic dyes

Removal of copper by Azolla filiculoides and Lemna minor: phytoremediation potential, adsorption kinetics and isotherms

Phytoremediation is an eco-friendly biotechnology with low costs. The removal of copper (Cu) from polluted water by the two floating plant species Azolla filiculoides and Lemna minor was observed and recorded. Plants were exposed to different Cu (II) concentration (0.25–1.00 mg/L) and sampling time (Days 0, 1, 2, 5 and 7). Both plants can remove Cu at 1.00 mg Cu/L water, with the highest removal rates of 100% for A. filiculoides and 74% for L. minor on the fifth day of exposure. At the end of the exposure period (Day 7), the growth of A. filiculoides exposed to 1.00 mg Cu/L was inhibited by Cu, but the structure of the inner cells of A. filiculoides was well organized as compared to the initial treatment period. Regarding L. minor, Cu at 1.00 mg/L negatively impacted both the growth and morphology (shrinking of its inner structure) of this plant. This is due to the higher accumulation of Cu in L. minor (2.86 mg/g) than in A. filiculoides (1.49 mg/g). Additionally, the rate of Cu removal per dry mass of plant fitted a pseudo-second order model for both plants, whereas the adsorption equilibrium data fitted the Freundlich isotherm, indicating that Cu adsorption occurs in multiple layers. Based on the results, both species can be applied in the phytoremediation of Cu-polluted water.

DNA methylation changes in promoter region of CDKN2A gene in workers exposed in construction environment

Purpose Construction workers are exposed to a mixture of substances in the workplace considered carcinogenic. This study aimed to characterise gene-specific changes in DNA methylation over the workweek in this population as this type of environmental exposure has not been studied extensively. Materials and methods We evaluated their DNA methylation in 4 gene-promoter regions (CDKN2A, RASSF1A, MLH1 and APC) and 2 repeat elements (ALU and LINE-1) in blood samples obtained on the first and fifth day of the same workweek of a group of 39 male construction workers. DNA methylation was measured by bisulphite-PCR-Pyrosequencing. We also measured the levels of trace elements in the whole blood by ICP-MS. Results Only the CDKN2A gene had significant differences in the average methylation level between the first and fifth day of the workweek. We also observed that the levels of Cu, Pb, Se, Mn, and Ti decreased during the fifth day of exposure, and only lead, titanium and copper showed a low significant correlation with the methylation level mean for three specific CpG sites of the CDKN2A. Conclusions In summary, the data suggest that altered levels of CDKN2A methylation in construction workers may be a potential biomarker of recent exposure in this environment.

Effect of Thiourea on Migratory Activity of Climbing Perch Anabas testudineus and Food Consumption

The effect of thiourea (exposure to 0.05% solution) on the migratory activity of the climbing perch Anabas testudineus has been studied. It is established that thiourea simultaneously affects two components of the migratory behavior of climbing perch: rheoreaction and frequency of jumps out of water. Thiourea stimulates (by 27%) movement of specimens against the current and increases (by 31%) the frequency of jumps out of water. The effect of the substance is manifested on the fifth day of exposure, while specimens almost completely stop feeding on the twelfth day. Starvation caused by thiourea may play a crucial role in the effect of thiourea on the migratory activity of climbing perch.

Ultrafine organic aerosol particles inhaled by mice at low doses remain in lungs more than half a year.

Experimental results of the second series of experiments on the penetration of monodisperse polymeric particles, inhaled at low dose by mice, to different organs using direct way of particle registration, based on the ultra-sensitive accelerator mass spectrometer (AMS), are presented. Polystyrene (PS) beads, composed of radiocarbon-labeled styrene, were produced for testing them as model organic aerosols. Mice inhaled 14 C-PS aerosol of 3·105 ultrafine particles per 1 cm3 for 30 minutes every day during 5 days. Long-term investigation showed that PS ultrafine particles have been effectively accumulated in lungs with the maximum content in the fifth day of postexposure, and have also appeared in liver on the fifth day of exposure and in the brain on the 30th day of experiments. No particles have been detected in kidneys, spleen, and excrements. Thirty-five millions of particles remained in the lungs after half a year of postexposure showing extremely slow removal of such particles from the organ.

Toxicity assessment and histopathological analysis of nano-ZnO against marine fish (Mugilogobius chulae) embryos

The toxicity of nano-materials has received increasing attention in recent years. Nevertheless, relatively few studies have focused on their oceanic distributions and toxicities. In this study, we assessed nano-ZnO toxicity in marine organisms using the yellowstriped goby (Mugilogobius chulae). The relative differences in nano-ZnO dissolution and dispersal in seawater and fresh water were also investigated. The effects of nano-ZnO on embryonic development, deformity, hatching, mortality, and histopathology were analyzed. In addition, the effects of the Zn2+ concentration on M. chulae hatching and mortality were compared. The results showed that nano-ZnO had higher solubility in seawater than in fresh water. Nano-ZnO significantly inhibited hatching. By the fifth day of exposure, the LC50 of nano-ZnO was 45.40mg/L, and the mortality rate spiked. Hatching inhibition and lethality were dose-dependent over a range of 1–25mg/L nano-ZnO. Zn2+ inhibited hatching and increased lethality, but its effects were weaker than those of nano-ZnO at the same concentrations. Nano-ZnO also induced spinal bending, oedema, hypoplasia, and other deformities in M. chulae embryos and larvae. Histopathology revealed vacuolar degeneration, hepatocyte and enterocyte enlargement, and morphological abnormalities of the vertebrae. Therefore, nano-ZnO caused malformations in M. chulae by affecting embryonic growth and development. We conclude that nano-ZnO toxicity in seawater was significantly positively correlated with the associated Zn2+ concentration and sedimentary behaviour. The toxicity of nano-ZnO was cumulative and showed a critical point, beyond which embryonic and developmental toxicity in marine fish was observed.

Copper and lead removal from aqueous solutions by bacterial consortia acting as biosorbents

A bacterial consortium was selected in the presence of Cu from sediment samples taken from Sepetiba Bay, Brazil, which is a site historically contaminated by metals. Bacteria were exposed to 0, 1, 6, 12.5, 25 and 50μg·mL−1 Cu, Pb and Cu+Pb for 11days of bioassay. Results showed Alcanivorax dominance (81%) and cell counts of 108cells·mL−1. However, a reduction in dehydrogenase activity was observed from the fifth day of exposure for all Cu, Pb, and Cu+Pb concentrations tested. Esterase activity tended to increase, indicating higher energy demand to complete the bacterial lifecycle. Pb concentrations in the filtered culture medium (0.2μm) were below the detection limit, indicating biosorption, whereas concentrations of Cu were close to the tested concentrations, indicative of efflux. Results suggest the need for biomarkers, such as esterase and dehydrogenase enzymatic activity, in the assessment of resistance and tolerance of communities previously exposed to stressors.

Increased p53 and decreased p21 accompany apoptosis induced by ultraviolet radiation in the nervous system of a crustacean

Ultraviolet (UV) radiation can produce biological damage, leading the cell to apoptosis by the p53 pathway. This study evaluated some molecular markers of the apoptosis pathway induced by UVA, UVB and UVA+ UVB (Solar Simulator, SIM) in environmental doses, during five consecutive days of exposure, in the brain of the crab Ucides cordatus. We evaluated the central nervous system (CNS) by immunoblotting the content of proteins p53, p21, phosphorylated AKT, BDNF, GDNF, activated caspase-3 (C3) and phosphohistone H3 (PH3); and by immunohistochemical tests of the cells labeled for PH3 and C3. After the fifth day of exposure, UVB radiation and SIM increased the protein content of p53, increasing the content of AKT and, somehow, blocking p21, increasing the content of activated caspase-3, which led the cells to apoptosis. The signs of death affected the increase in neurotrophins, such as BDNF and GDNF, stimulating the apoptotic cascade of events. Immunohistochemical assays and immunoblotting showed that apoptosis was present in the brains of all UV groups, while the number of mitotic cells in the same groups decreased. In conclusion, environmental doses of UV can cause apoptosis by increasing p53 and decreasing p21, revealing an UV-damage pathway for U. cordatus.

Pseudomonas sp. strain AKM-P6 enhances tolerance of sorghum seedlings to elevated temperatures

A thermotolerant strain AKM-P6 of Pseudomonas sp. possessing plant growth-promoting properties was isolated from rhizosphere of pigeon pea grown under semiarid conditions in India. The effect of inoculation with AKM-P6 on survival and growth of sorghum seedlings at elevated temperatures (ET) was investigated under sterile and nonsterile soil conditions. Inoculation with strain AKM-P6 helped sorghum (var CSV-15) seedlings to survive and to grow at elevated temperatures (47–50°C day/30–33°C night) up to 15 days while uninoculated plants died by the fifth day of exposure to elevated temperature. Under sterile and nonsterile conditions, significantly higher root and shoot biomass were recorded in inoculated seedlings as compared to uninoculated control at ET, but this difference was nonsignificant at ambient temperature. Inoculation induced the biosynthesis of high-molecular weight proteins in leaves under elevated temperature, reduced membrane injury, and improved the levels of cellular metabolites like proline, chlorophyll, sugars, amino acids, and proteins. Scanning electron microscopy studies confirmed the colonization and establishment of the organism on the root surface. The 16SrDNA sequence of the strain AMK-P6 showed 97% homology with that of Pseudomonas aeruginosa in the existing database. The results indicate that Pseudomonas sp. strain AKM-P6 can enhance tolerance of sorghum seedlings to elevated temperatures by inducing physiological and biochemical changes in the plant.

Measurement of Toluene Concentrations in the Blood of Fetuses of Pregnant Rats Exposed to Low Concentration Toluene Using Headspace-Solid Phase Micro Extraction-Gas Chromatography-Mass Spectrometry

In order to measure the level of toluene in the blood of fetuses of pregnant rats exposed to toluene, application of headspace-solid phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was studied. Pregnant rats from gestational day 15 (GD15) to GD19 were subjected to inhalational exposure to toluene for 90 min per day. They were obtained by Cesarean section on the fifth day of exposure (on GD19), and the level of toluene in the blood of mother rats and in fetuses were quantified using 5µl blood. The levels of toluene in the blood of the fetuses in the groups exposed to toluene at 9 ppm and 90 ppm were 0.07 ± 0.03µg/ml (n = 17) and 2.0 ± 0.51µg/ml (n = 16) respectively, which were significantly higher than the blood level of the fetuses in the control group (0.02 ± 0.02µg/ml, n = 12). Meanwhile, the blood concentrations of mother rats were 0.06 ± 0.06µg/ml (n = 3, control group), 0.14 ± 0.03µg/ml (n = 3, 9 ppm exposure group), and 3.5 ± 1.5µg/ml (n = 4, 90 ppm exposure group), respectively, which were higher than those of the fetuses per unit blood volume.

Bioconcentration of the insecticide pyridaphenthion by the green algae Chlorella saccharophila

A study was undertaken to examine the uptake of the organophosphate insecticide pyridaphenthion in the chlorophyta Chlorella saccharophila. Algae cultures were exposed to the initial nominal concentration 10.0 mg l −1 pyridaphention during seven days. The insecticide bioconcentrates in the biomass to the highest level of 441.5 ± 25.9 mg kg −1 on the fifth day of exposure and was followed by a decrease to 76.6 ± 5.1 mg kg −1 on the seventh day. A model was constructed to describe the dynamic process, which estimated a bioconcentration factor (BCF) equal to 28. The study demonstrates the potential of accumulation of pyridaphenthion in aquatic organisms and helps to expand the pyridaphenthion toxicity database. The replacement of fenitrothion by pyridaphenthion concerning their use in rice flooded cultures is discussed.

Sexual dimorphism of brain aromatase activity in medaka: induction of a female phenotype by estradiol.

In this study we identified sex-dependent dimorphism of brain aromatase in the teleost medaka and examined its regulation by sex steriods. We first investigated differential distribution of brain aromatase activity in sexually mature male and female medaka in serial coronal sections of the brain and identified the hypothalamic nuclei contained in each section using the brain atlas of medaka. In the brain of male medaka, high levels of activity are localized in sections containing the preoptic (POA) and suprachiasmatic nuclei (SC) (63-75 fmol/hr) and low levels in the nuclei periventricular dorsalis (HD), ventralis (HV), and caudalis (Hc), nuclei diffusus of lobulus inferiores (NDIL), and nuclei tuberi anteriores (TA) and posteriores (TP) (< 25 fmol/hr). In the brain of female medaka high aromatase activity is localized in sections containing the HD, HV, Hc, NDIL, TA, and TP (85-80 fmol/hr) and highly variable levels in the POA and SC (23-70 fmol/hr). The concentration and time dependency of the exposure of male medaka to estradiol on the total brain aromatase activity and morphologic sex characteristics were determined next. Estradiol increased the activity of brain aromatase in a concentration-dependent manner at 2.5 and 25 microg/L, but the increase was lower at higher concentrations of the hormone. The effect was time dependent, gradually increasing up to the fifth day of exposure, after which it reached a plateau. Estradiol induction of brain aromatase analyzed using Lineweaver-Burke plots of saturation assays revealed a non-first-order reaction. The results indicate that a positive feedback mechanism regulates brain aromatase and imply that the sexual dimorphic distribution of aromatase may be highly sensitive to physiologic cues and environmental perturbations in fish.

Effects of p‐nonylphenol, methoxychlor, and endosulfan on vitellogenin induction and expression in sheepshead minnow (Cyprinodon variegatus)

AbstractTemporal and dose‐responserelationshipsofvitellogenin(VTG) mRNA nductionand subsequent plasma VTG accumulation were established for sheepshead minnows (Cyprinodon variegatus) treated with p‐nonylphenol (an alkylphenol) and the organochlorine pesticides methoxychlor and endosulfan. Thirty‐two adult male fish per treatment were continuously exposed to measured concentrations of 0.64, 5.4, 11.8, 23.3, and 42.7 μg/L p‐nonylphenol; 1.1, 2.5, 5.6, 12.1, and 18.4 μg/L methoxychlor; and in two separate tests, 15.9, 36.3, 68.8, 162, 277, 403, 590, and 788 ng/L endosulfan using an intermittent flow‐through dosing apparatus. Separate triethylene glycol (50 (μl/L) and 17β‐estradiol (65.1 ng/L) treatments served as the negative and positive controls, respectively. Four fish were randomly sampled from each test concentration on days 2, 5, 13, 21, 35, and 42 of exposure, and levels of hepatic VTG mRNA induction and serum VTG accumulation were determined for each individual. Overall, fish exposed to p‐nonylphenol or methoxychlor demonstrated a rapid, dose‐dependent synthesis of VTG mRNA up to day 5 of exposure, followed by a relatively constant dose‐dependent expression through day 42. Both chemicals showed a dose‐dependent increase in plasma VTG over the entire time course of exposure, with significantly elevated VTG levels by the fifth day of exposure to p‐nonylphenol at concentrations of 5.4 μg/L or greater and to methoxychlor at concentrations of 2.5 μg/L or greater. Exposure to 0.64 μg/L p‐nonylphenol resulted in highly variable plasma VTG levels of less than 6 mg/ml. Exposures with endosulfan failed to induce measurable levels of either hepatic VTG mRNA or serum VTG at the chemical concentrations tested. Our results demonstrate that the sheepshead minnow bioassay is a suitable estuarine/marine teleost model for in vivo screening of potentially estrogenic substances.

Effects of p-nonylphenol, methoxychlor, and endosulfan on vitellogenin induction and expression in sheepshead minnow (Cyprinodon variegatus).

Temporal and dose-response relationships of vitellogenin (VTG) mRNA induction and subsequent plasma VTG accumulation were established for sheepshead minnows (Cyprinodon variegatus) treated with p-nonylphenol (an alkylphenol) and the organochlorine pesticides methoxychlor and endosulfan. Thirty-two adult male fish per treatment were continuously exposed to measured concentrations of 0.64, 5.4, 11.8, 23.3, and 42.7 micrograms/L p-nonylphenol; 1.1, 2.5, 5.6, 12.1, and 18.4 micrograms/L methoxychlor; and in two separate tests, 15.9, 36.3, 68.8, 162, 277, 403, 590, and 788 ng/L endosulfan using an intermittent flow-through dosing apparatus. Separate triethylene glycol (50 microliters/L) and 17 beta-estradiol (65.1 ng/L) treatments served as the negative and positive controls, respectively. Four fish were randomly sampled from each test concentration on days 2, 5, 13, 21, 35, and 42 of exposure, and levels of hepatic VTG mRNA induction and serum VTG accumulation were determined for each individual. Overall, fish exposed to p-nonylphenol or methoxychlor demonstrated a rapid, dose-dependent synthesis of VTG mRNA up to day 5 of exposure, followed by a relatively constant dose-dependent expression through day 42. Both chemicals showed a dose-dependent increase in plasma VTG over the entire time course of exposure, with significantly elevated VTG levels by the fifth day of exposure to p-nonylphenol at concentrations of 5.4 micrograms/L or greater and to methoxychlor at concentrations of 2.5 micrograms/L or greater. Exposure to 0.64 microgram/L p-nonylphenol resulted in highly variable plasma VTG levels of less than 6 mg/ml. Exposures with endosulfan failed to induce measurable levels of either hepatic VTG mRNA or serum VTG at the chemical concentrations tested. Our results demonstrate that the sheepshead minnow bioassay is a suitable estuarine/marine teleost model for in vivo screening of potentially estrogenic substances.

Unattenuated Structural and Biochemical Alterations in the Rat Lung during Functional Adaptation to Ozone

Acute ozone (O3) exposure in humans produces changes in pulmonary function that attenuate with repeated exposure. This phenomenon, termed adaptation, has been produced in unanesthetized rats. Rats exposed to O3 (0, 0.35, 0.5, or 1.0 ppm) for 2.25 h for 5 consecutive days showed an increased frequency of breathing and a decreased tidal volume on Days 1 and 2 of exposure at all O3 concentrations. However, by Day 5 these breathing responses to O3 were diminished in rats exposed to 0.35 and 0.5 ppm, but not in rats exposed to 1.0 ppm. In addition, a flow limitation in smaller airways was observed after the second day of exposure to 0.5 ppm O3 that initially attenuated and then disappeared by the fifth day of exposure. In contrast to these findings, a light microscopic examination of fixed lung tissue sections from rats exposed to 0.5 ppm indicated a 5-day progressive pattern of epithelial damage and inflammation in the terminal bronchiolar region. A sustained 37% increase in lavageable protein was also observed over the course of the 5-day exposure regimen to 0.5 ppm. Lung glutathione increased initially, but it was within the control range on Days 4 and 5. Lung ascorbate was significantly elevated above control levels on Days 3 and 5. These data suggest that attenuation of the pulmonary function response to O3 occurs in laboratory rats with repeated exposure while biochemical and morphologic aspects of the tissue response continue to progress.

Early biochemical changes produced by malathion on toad embryos.

The exposure of newly fertilized amphibian embryos to malathion (44 mg/L) produces 67% mortality on the fifth day of exposure. Clinical signs of intoxication are evident on the fourth day. A variety of biochemical parameters, such as enzyme activity, lipid and protein content, was examined in control and malathion-treated embryos. The activity of acetyl, butyrylcholinesterase and aliesterase are quickly inhibited. An interference with cellular protein synthesis and redistribution is possible. A slight increase in total phospholipids is evident after 24 hr of exposure.

Effects of nitrogen dioxide on biochemical and physiological characteristics of soybean.

One month old soybean (Glycine max (L.) Merrill) cv. 'Williams' plants were exposed to nitrogen dioxide (NO2 at 0.1, 0.2, 0.3, and 0.5 microl liter(-1) and carbon filtered air (control), 7 h per day for five days, under controlled environment. Data were collected on net photosynthetic rate (PN), stomatal resistance (SR), and dark respiration rate (DR), immediately following the fifth day of exposure and 24 h after termination of exposure. Chlorophyll a (Ch a), chlorophyll b (Ch b), total chlorophyll (tot Ch) and foliar nitrogen (N) were measured before and after exposures. Growth characteristics--relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and root shoot ratio (RSR) -- were computed for treated plants using standard growth equations. Increases of 18% and 23% in PN were observed immediately following exposure to 0.2 microl liter(-1) NO2 and after 24 h recovery period, respectively. With 0.5 microl liter(-1) NO2 treatment, reductions in PN of 23% and 50% were observed, immediately after exposure and following 24 h recovery, respectively. DR rates with 0.2 l liter(-1) treatment were higher than the control. Chlorophyll a and tot Ch showed significant reduction with 0.5 microl liter(-1) NO2 treatment. The percent reduction in Ch a and tot Ch with 0.5 microl liter(-1) NO2 were 45% and 47%, respectively. Increases in foliar nitrogen content after 0.2 and 0.3 microl liter(-1) NO2 treatments were 46% and 69%, respectively. Nitrogen dioxide at 0.5 microl liter(-1) reduced RGR and NAR by 47% and 51%, respectively. Leaf area ratio was 42% higher in 0.5 microl liter(-)1 NO2 treated plants, compared with the control; this increase was insufficient to compensate for the decrease in NAR resulting in a net decline in RGR. Nitrogen dioxide up to 0.2 microl liter(-1) increased PN and foliar-N content of soybean. With 0.5 microl liter(-1) NO2, significant decreases were observed in PN, leaf chlorophyll, foliar-N, NAR and RGR. Nitrogen dioxide up to 0.2 microl liter(-)1 has a favorable influence on overall growth characteristics of soybean; however, inhibitory effects were seen with NO2 treatment at 0.5 microl liter(-1).

In vivo effects of nitrogen dioxide on membrane constituents in lung and liver of rats

When rats were exposed to 10 ppm NO 2 for 7 days, the succinate-cytochrome c reductase activity, the rate-limiting step of mitochondrial succinoxidase, of the liver decreased progressively, reaching 77% ( P < 0.01) of the control level by the fifth day. By contrast, this activity was gradually increased by a 10-day exposure to 4 ppm NO 2 and reached 1.14-fold that of the control level at the seventh day. A reduction in the components of electron-transport systems in liver microsomes was found during exposure to NO 2 at both concentrations. This reduction was preferential for components of drug-metabolizing systems. The NADPH-cytochrome c reductase activity and the cytochrome P-450 content were decreased to 82% ( P < 0.05) and 76% ( P < 0.05), respectively, at the fifth day of exposure to 10 ppm NO 2. Exposure to 4 ppm NO 2 also caused a significant decrease in the NADPH-cytochrome c reductase and the cytochrome P-450 content, which were lowered to 84% ( P < 0.05) of the control level at the fourth and seventh days, respectively. Reduction in these components appears to occur even at the concentration of 0.4 ppm at the seventh day. Alterations in the components of mitochrondria and microsomes of the lung were considerably different from those of the liver. The protein content of the lung increased to 1.18 ( P < 0.05)- and 1.14 ( P < 0.05)-fold that of the control during exposure to 10 and 4 ppm NO 2, respectively. The succinate-cytochrome c reductase activity showed a reduced value, which was 73% ( P < 0.01) of the control level, 1 day after exposure to 10 ppm NO 2. Subsequently, the activity increased to 1.14-fold that of the control during exposure to 10 (at the fifth day) and 4 ppm (at the fourth day) NO 2. Components of microsomal electron-transport systems also showed a slightly elevated value during exposure to 4 ppm NO 2. Seven days after exposure, the cytochrome P-450 content was decreased to 61% ( P < 0.01) of the control level, while other components were retained at control levels. A significant reduction in the cytochrome P-450 content was also observed at the exposure concentration of 1.2 ppm, but not of 0.4 ppm, at the seventh day.

Behavioral Toxicology of Volatile Organic Solvents. III. Acute and Subacute Effects of Carbon Disulfide Exposure on the Behavior of Mice

The effects of exposure to carbon disulfide (CS2) were studied on two different behavioral responses in mice. One response was the interruption of a single light beam passing immediately behind a small hole in the wall of the mouse chamber. The other response was the consecutive interruption of each of three radial light beams spaced around a circular runway. Both responses were maintained under an FI 60-sec schedule of milk presentation. Acute, cumulative concentration-effect functions were determined by increasing, stepwise, the concentration of CS2 in the chamber until responding was abolished. Although the level of physical activity required by the two responses was quite different, the acute effects of CS2 on each were quantitatively similar: a concentration of 120 ppm was without effect, 580 ppm decreased responding in most mice, to as low as 0.55 of control levels, 2200 ppm decreased responding in all mice, and 3700 ppm abolished responding. Recovery from these acute effects was slow; following cumulative exposures which abolished responding, recovery to 0.50 of the control level of responding took more than 4 hr, and full recovery required 6 hr. With repeated daily exposure to CS2, the cumulative effect on both types of responding depended upon the concentration and the duration of the exposure. No effect was seen with either response until the fifth day of exposure to 260 ppm; 580 ppm decreased responding progressively during most daily exposures but the overall decrease was not different on successive days; 840 ppm decreased responding progressively during daily exposures and the decrease was also progressively greater on successive days. Daily control performances before exposure were unaffected during repeated exposure, so the manifest effects of these levels of CS2 did not appear to last as long as 18 hr.