Effects Of Sublethal Concentrations Research Articles

Injury by heavy metals in Escherichia coli.

The aim of the present study on the effects of sublethal concentrations of metals on the growth and recovery of E. coli, is to throw light on some of the aspects of the viability and recovery of E. coli as well as changes in its cell enzymatic activity when exposed to sublethal concentrations of heavy metals. Total dehydrogenase was used since it is a measure of bacterial activity closely related to energetic metabolic systems and ..beta..-galactosidase as a typical inducible enzyme in E. coli. E. coli was chosen as the test organism, both on account of its importance in public health (sanitary indicators) and for the information available (biochemical and genetic properties) on it.

The species-specific effects of sublethal concentrations of cadmium on freshwater phytoplankton communities in a Canadian Shield lake

The species-specific responses of natural phytoplankton communities to low cadmium concentrations were measured in Lake 239 (Experimental Lakes Area, northwestern Ontario). Both in situ and laboratory 5-L continuous-flow cultures, and 5-L and 100-mL cultures were used. Asterionella formosa, Dinobryon sertularia, and Dinobryon bavaricum showed dramatic negative sensitivity to low cadmium concentrations (5–100 μg/L), while Rhabdoderma gorskii and Elakatothrix sp. consistently increased in numbers at the same cadmium concentrations. In all experiments, some species exhibited no apparent effect to cadmium addition as measured by cell counts. The "bottle effect" of each technique was evaluated by comparing the community similarity valves of the control cultures to the lake samples and showed the in situ continuous cultures to be most similar to the lake followed by the laboratory continuous cultures, the in situ 5-L batch cultures, the 5-L laboratory cultures, and the 100-mL batch cultures. Replicate cadmium cultures, all techniques, were more similar to each other than the lake samples. The similarity of the cadmium cultures to the lake sample or control cultures decreased with increased cadmium concentration and incubation time.

Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

AbstractThe effect of sublethal concentrations (LC1 and LC50) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC1 and LC50 concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC50 values.

Molecular genetic and phenotypic alteration ofEscherichia coliin natural water microcosms containing toxic chemicals

Microcosms of sterile Chesapeake Bay water were used to study effects of sub-lethal concentrations (1 μl/l) of nitrobenzene, m-cresol, and dibutyl phthalate on Escherichia coli H10407. E. coli remained viable during the 19-day test period in estuarine water, both in the presence and absence of the chemicals, long after it became non-culturable. Analysis of membrane proteins revealed changes in the protein composition. Carbohydrate and amino acid utilization was affected by these changes. Plasmids in E. coli H10407 could not be detected following microcosm exposure. When the cells were transferred to rich medium without toxic chemicals, growth resumed and plasmid bands were again detectable.

Nickel toxicity on carbohydrate metabolism of a freshwater fish, Colisa fasciatus

Effects of sublethal concentration (0.8 of LC 50 96 h) of nickel sulphate (NiSO 4· 7H 2O) on muscle glycogen and blood lactic acid levels of a freshwater teleost, Colisa fasciatus, at time intervals from 3–96 h have been recorded. Muscle glycogen levels showed a general decrease at all time intervals compared with controls, with a maximum decrease of 35.2% at 96 h ( P<0.001). Blood lactic acid showed an increase at all stages attaining a maximum of 78.12% at 12 h ( P<0.001) except at 24 h where, for reasons not clearly understood, a distinct fall was recorded. The muscle glycogenolysis accompanied by blood hyperlacticaemia is probably the result of some direct action of nickel on the fish. The severe stress conditions caused by nickel-induced pathological changes in the gills and blood may also be responsible for these metabolic changes.

A clinical approach to study the pollutants intoxication in a freshwater teleost clarias batrachus

The effect of sublethal concentrations of aldrin and Swascofix CD-38 was studied on certain haematological parameters of C. batrachus after 10, 20, and 30 days exposures. The parameters studied were CT, PT, Hb, RBC, WBC, PCV, MCH, MCHC, MCV, specific gravity and pH. CT, MCH, and MCV were found to be decreasing with the increase of pollutant concentrations and time of exposure, while all other parameters showed an increase. However, pH and specific gravity remained generally uneffected.

In vivo effect of mercuric chloride on tissue ATPases of Notopterus notopterus

Effect of sublethal concentrations, 0.088, 0.044, 0.029, 0.022 and 0.0176 mg HgCl 2 per liter ( 1 5 , 1 10 , 1 15 , 1 20 , and 1 25 fractions of 96-h LC 50) on Na +-K +, Mg 2+, and total ATPase activities in brain, gills, kidney and liver of Notopterus notopterus have been studied after 30 days exposure. Na +-K + ATPase were inhibited maximally and significantly in brain and minimally and insignificantly in liver. Mg 2+ ATPase was inhibited maximally and significantly ( P<0.01) in brain and minimally and insignificantly in kidney. The relative inhibition of total, Na +-K + and Mg 2+ ATPases for the tissues studied were brain > gill > kidney > liver. At the lowest concentration ( 1 25 fraction) the enzyme activity returned to the normal range.

The effects of a few xenobiotics on certain phosphatases in the plasma of Clarias batrachus and Cirrhina mrigala

The effects of sublethal concentrations 1 2 , 1 4 and 1 8 fractions of 96-h LC 50 of aldrin and Swascofix CD-38 on alkaline, acid and glucose-6-phosphatases in the plasma of Clarias batrachus and Cirrhina mrigala were studied. These enzymes increased after exposure of fish to both xenobiotics. The increase was maximal after 20 days exposure to the highest concentrations. The enzyme increase was greatest in the fish exposed to aldrin.

Effects of sodium pentachlorophenate on enzymes of energy metabolism in tissues of Notopterus notopterus

Effect of sublethal concentrations (0.0083, 0.0055, 0.0041, 0.0033 and 0.0028 mg/l) of sodium pentachlorophenate (Na-PCP) on the enzymes SDH, PDH and LDH in brain, liver and gills of Notopterus notopterus after 15 and 30 days exposure were studied. SDH and PDH were inhibited, and LDH were stimulated significantly at most concentrations. However, changes were maximum (−68.3%, −73.4% and + 197.7% for SDH, PDH and LDH, respectively) in brain after 30 days, and minimum (−1.3% and + 2.4% for SDH and LDH, respectively) in gills and (−3.4% for PDH) brain after 15 days. Inhibition of SDH and PDH, and the stimulation of LDH activity indicate the development of anaerobic conditions at the cellular level in pollutant-stressed fish.

Pesticide-induced physiological alterations in certain tissues of a fish, Mystus vittatus

Effect of sublethal concentrations ( 1 5 , 1 10 and 1 15 fractions of 96-h TL 50) of thiotox, dichlorvos and carbofuran on acid, alkaline and glucose-6-phosphatases of liver, kidney and gills of Mystus vittatus have been studied. Maximum (62.79%) inhibition of alkaline phosphatase in gills after thiotox (0.00013 mg/1) treatment and minimum inhibition (6.12 %) of glucose-6-phosphatase in liver after dichlorvos (0.030 mg/1) treatment have been observed. At 0.000045 mg/1 concentration of thiotox, a marginal (7.6%) and significant (P<0.01) stimulation was observed in hepatic alkaline phosphatase activity.

Petroleum hydrocarbons in aquatic ecosystems — behavior and effects of sublethal concentrations: Part 1∗

Petroleum hydrocarbons in aquatic ecosystems — behavior and effects of sublethal concentrations: Part 1∗

Effects of sublethal concentrations of selenium on metabolism and filtering rate of Daphnia pulex.

The purpose of this research was to evaluate the sublethal effects of selenium on Daphnia pulex oxygen consumption and filtering rate. Selenium is a trace element which is receiving increased attention as an environmental pollutant because of its high concentration in coal and other fossil fuels. It is the least plentiful and most toxic of the essential trace elements with a very narrow margin of safety between required and toxic doses.

Effects of sublethal concentrations of mercuric chloride on ammonium-limitedSkeletonema costatum

The effect of sublethal additions of mercuric chloride on the marine diatomSkeletonema costatum (Grev.) Cleve grown in NH4-limited chemostats and batch cultures was assessed. In short-term Hg exposure experiments (up to 5 h), the effect of Hg on ammonium uptake rates was studied by simulatneously perturbing the culture with 5 μM NH4 Cl and Hg concentrations ranging from 0.04 to 5.52 nM HgCl2. The threshold of Hg toxicity occurred between 1.8 and 3.7 nM, based on a decrease in ammonium uptake rates. When the NH4-limited culture was starved of ammonium for 30 h, the threshold of Hg toxicity decreased about an order of magnitude to 0.2 nM. In long-term Hg exposure experiments (679.5 h), NH4-limited continuous cultures were semi-continuously exposed to 0.37 and 3.68 nM HgCl2. After 4 days, the cell density in the Hg-treated chemostats began to drastically decline. After about 16 days these populations recovered, even though Hg additions continued. At the end of the experiment (26 days), cell densities had reached the levels observed at the beginning of the experiment. The reason for the recovery is unknown, but several possibilities are discussed. Ammonium uptake rates determined during the time-course of this long-term Hg exposure, indicated that these NH4-limited cultures exhibited a significant loss in their ability to take up ammonium at low concentrations (e.g. 1 μM). Thus, mercury pollution may seriously decrease the ability of a species to utilize the limiting nutrient during periods of seasonal nutrient limitation.

Effects of sublethal concentrations of cadmium as possible indicators of cadmium pollution for two populations of Acartia clausi (Copepoda) living at two differently polluted areas.

Toxicity of heavy metals to marine organisms is a subject of interest because, due to technological development, the sea receives an increasing amount of heavy metals. Acute toxicity studies have played a major role in estimating the effects of heavy metals to marine organisms because survival is considered the best index of a pollutant stress, being in general the least variable. However, long term exposure to sublethal concentration of a pollutant may markedly alter the normal functioning of organisms and thus destroy a population as effectively as lethal doses. Therefore, the study of the effects of sublethal doses is indispensable if we want to set realistic standards of water qualtiy criteria. The purpose of this study was twofold: first to establish and characterize the sublethal effects of cadmium on different physiological processes (longevity, feeding, respiratory rates), and second to verify whether there exist differences in the effects of sublethal concentrations of cadmium between the two populations of Acartia adapted to differently polluted areas.

The Effect of Sub-Lethal Concentrations of Mercury and Zinc on Chlorella

Summary Sodium selenite (Na2SeO3) and some sulphydryl (-SH) compounds, including the amino acid cysteine protect Chlorella against the sub-lethal effects of mercuric chloride (HgCl2) and phenylmercuric acetate (PMA). However just the addition of selenium and the sulphur compounds to the culture medium containing zinc chloride (ZnCl2), HgCl2 or PMA provided little or no protection. But when Chlorella was incubated for six days in selenium and the sulphydryl compounds prior to metal treatments, then cells were markedly protected against mercury toxicity (but not zinc toxicity) as measured by increased cell division rates. Cells incubated in methionine (-SCH3) were only slightly protected, and cells incubated in the disulphide compound, cystine (-SS) were not protected at all. The increase in rates of cell division (protection) was strongly correlated to the amount of sulphydryl groups in the cells. Physiological implications of the work are discussed.

Effect of sublethal concentrations of malathion on Coturnix quail

Effect of sublethal concentrations of malathion on Coturnix quail

The toxicity of ozone to the bluegill

Abstract Ozone toxicity to bluegill (Lepomis macrochirus) was determined using standard bioassay procedures. In initial work bluegill were exposed to water containing ozone for 24 h; the LC50 was 0.06 ppm. A second experiment simulated “shock defouling” — the periodic dosing of power plant cooling water with high biocide concentrations to prevent biofouling. The LC50 for a series of six 30‐min exposure periods spaced 8 h apart was 0.32 ppm. A third experiment attempting to determine the effects of sublethal concentrations resulted in the death of 9 of 15 bluegill after 4 weeks of exposure to 0.01 ppm of ozone. No controls died in any experiment. It was concluded that ozone is highly toxic to bluegill. Safe limits for long‐term exposure probably lie well below 0.01 ppm. The results of this study and an examination of the literature indicate that ozone is more toxic than chlorine; however, ozone is readily removed from treated water while some chlorine compounds are not.

The effects of sublethal concentrations of five organophosphorus insecticides on temperature tolerance, reflexes, and orientation in Gambusia affinis affinis (Pisces: Poeciliidae)

Gambusia affinis were exposed to the insecticides ABATE®, fenthion, chlorpyrifos, methyl parathion, and malathion for 24 h at concentrations of 1, 5, and 10 ppb and for 48 h at 5 ppb. The thermal tolerance was lowered significantly for male and female G. affinis by the toxicants methyl parathion and chlorpyrifos at 5 and 10 ppb with 24 h exposure. Activity was restricted with fish exposed to methyl parathion and chlorpyrifos at concentrations of 10 ppb for 24 h and at 5 ppb for 48 h.

Locomotor hyperactivity induced in the bluegill sunfish, Lepomis macrochirus, by sublethal concentrations of DDT.

A quantitative description of the effects of sublethal concentrations of DDT on the locomotor activity of the bluegill sunfish, Lepomis macrochirus, is presented. DDT-elicited hyperactive locomotor responses at all the concentrations examined (0.008, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, and 0.2 parts per billion (ppb)) and the degree of such responses were concentration dependent. Maximal effects at each concentration were observed within 8 days after addition of DDT to the environment. At their maxima, fish at 0.008 ppb were 1.3 times as active as control fish, whereas fish at 0.2 ppb were 3.0 times as active as controls. The effects of DDT on locomotor activity were not reversed even after the fish were transferred back into tap water for 2 weeks.

The Effect of Sub-Lethal Concentrations of Mercury and Zinc on Chlorella

Summary The effects of either 1 mM ZnCl 2 , 1 μm HgCl 2 or 0.1 μM phenyl mercuric acetate solutions on photosynthesis, pigment composition and respiration are described for cultures of Chlorella . Although photosynthesis and respiration are initially inhibited in young cultures, there is a recovery towards control values as the cultures proceed in their growth. In young cultures the inhibition in photosynthesis is associated with a loss in chlorophyll. In cultures grown for several days in metal solutions, photosynthesis per unit mass of chlorophyll may exceed control values - in phenyl mercuric acetate solutions in particular. Mercury solutions markedly enhance protochlorophyll levels in young cultures, while decreasing chlorophyll a/b and pheophytin a/b ratios. These observations are interpreted in terms of the action of metals on the oxidative and reductive steps in the biosynthetic pathway of pigments.