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At least 235 records · Page 13Linked to original sources
PubMed2004

Riparian deforestation, stream narrowing, and loss of stream ecosystem services.

A study of 16 streams in eastern North America shows that riparian deforestation causes channel narrowing, which reduces the total amount of stream habitat and ecosystem per unit channel length and compromises in-stream processing of pollutants. Wide forest reaches had more macroinvertebrates, total ecosystem processing of organic matter, and nitrogen uptake per unit channel length than contiguous narrow deforested reaches. Stream narrowing nullified any potential advantages of deforestation regarding abundance of fish, quality of dissolved organic matter, and pesticide degradation. These findings show that forested stream channels have a wider and more natural configuration, which significantly affects the total in-stream amount and activity of the ecosystem, including the processing of pollutants. The results reinforce both current policy of the United States that endorses riparian forest buffers as best management practice and federal and state programs that subsidize riparian reforestation for stream restoration and water quality. Not only do forest buffers prevent nonpoint source pollutants from entering small streams, they also enhance the in-stream processing of both nonpoint and point source pollutants, thereby reducing their impact on downstream rivers and estuaries.

Animals↗
PubMedDate not supplied

Endocrine active agents: implications of adverse and non-adverse changes.

The US Environmental Protection Agency (EPA) is currently in the process of developing screening and testing methodologies for the assessment of agents that may possess endocrine-like activity--the so-called endocrine disruptors. Moreover, the EPA has signaled its intention of placing information arising from such studies on the worldwide web. This has created significant interest in how such information may be used in risk assessment and by policymakers and the public in the potential regulation or deselection of specific chemical agents. The construction of lists of endocrine disruptors, although fulfilling the requirements of some parties, is really of little use when the nature of the response, the dose level employed, and the lifestage of the test species used are not given. Thus, we have already seen positive in vitro information available on the interaction with a receptor being used as a key indicator when the results of large, high quality in vivo studies showing no adverse changes have been ignored. Clearly a number of in vitro systems are available to ascertain chemical interaction with specific (mainly steroid) hormone receptors including a number of reporter gene assays. These assays only provide indicators of potential problems and should not be, in isolation, indicators of toxicity. Likewise, short-term in vivo screens such as the uterotrophic and Hershberger studies are frequently conducted in castrated animals and thus indicate the potential for a pharmacological response in vivo rather than an adverse effect. A number of new end points have been added to standard rodent testing protocols in the belief of providing more sensitivity to detect endocrine related changes. These include the measurement of anogenital distance (AGD), developmental landmarks [vaginal opening (VO), preputial separation (PPS)], and in some studies the counting of nipples and areolae on males. AGD, VO, and PPS are all affected by the size of the pup in which they are measured and should always be compared using bodyweight as a covariate. The historical control database for such changes is gradually growing, albeit that if pups are not individually identified it becomes problematic to associate any change with a specific malformation or to assess whether a delay or advance in, for example, developmental landmarks is biologically significant. Agents that significantly reduce AGD in males (it is an androgen-dependent variable) frequently have other more adverse changes associated with this end point (eg, reproductive tract malformations), but a 2 to 3% change in AGD although measurable is unlikely to be biologically of importance and in isolation would not necessarily be considered adverse. Retention of thoracic nipples in male rat pups is also an indicator of impaired androgen status. Recent studies have also shown that this retention for some endocrine active chemicals is permanent. Thus, the presence of a permanent structural change that is rarely found in adult control animals could be considered a malformation and therefore a developmental adverse effect on which risk assessment decisions could be made. The advent of multigeneration reproduction studies as the definitive studies for the assessment of the dose-response relationships and risk assessment for endocrine disruptors has shown that current testing protocols may be inadequate to reliably detect the adverse effects of concern as only 1 adult/sex/litter is examined. A number of the effects on reproductive development although, due to an in utero exposure, will not be manifest until after puberty or at adulthood. The use of only a limited number of animals to examine such changes, particularly for weaker acting materials indicates that some agents may have been examined in well-conducted, modern protocols but have insufficient power to detect low incidence phenomena (eg, a 5% incidence of malformations).

Androgen Antagonists↗
PubMed2003

Oxidative stress and bioindicators of reproductive function in pulp and paper mill effluent exposed white sucker.

This study investigates oxidative stress and bioindicators of reproductive function in wild white sucker (Catostomus commersoni) collected from environments receiving pulp and paper mill effluent discharges in northern Ontario. Samples were collected over an eight-year period adjacent to three pulp and paper mills using a variety of processing and bleaching techniques. Fish collected downstream of pulp and paper mills within the Moose River basin exhibited elevated hepatic and gonadal 2-thiobarbituric acid reactive substances (TBARS), the presence of which is indicative of oxidative stress in these tissues. Within the Jackfish Bay system, exposure to pulp and paper mill effluent did not elevate hepatic or gonadal TBARS. Hepatic cytochrome P4501A activity (CYP1A) and fatty acyl-CoA oxidase (FAO) activities were frequently increased in livers of Moose River basin fish exposed to pulp and paper mill effluent, while lower activities of both enzymes were found within fish from the Jackfish Bay system. This suggests that oxidative stress may be related to CYP1A and FAO activities. Within the Moose River system, increases in measures of oxidative stress (TBARS, FAO) were generally coincident with decreased levels of 17 beta-estradiol; however, testosterone was often lower in Jackfish Bay system fish without any commensurate changes in oxidative stress. The suite of reproductive and oxidative stress parameters measured in this study varied between seasons and mills suggesting responses to effluent are dynamic and effects are complicated by different receiving environments. The relationship between gonad size, gonadal oxidative stress, and circulating plasma steroids remains unclear.

Androgen Antagonists↗
PubMed1995

The effect of p-chloroaniline on leucocytes of sheep peripheral blood under the migration-inhibition test conditions.

Toxic and immunotoxic effects of p-chloroaniline--a metabolite of herbicide monolinuron--were investigated in peripheral blood leucocytic suspensions of five sheep using a migration-inhibition test. The toxic effect of p-chloroaniline was recorded at concentrations 1.0 to 0.1 mg.ml-1 and the immunotoxic one at concentrations 0.01-0.001 mg.l-1. The toxic effect was demonstrated by total inhibition of leucocyte migration. The immunotoxic effect, determined as mitogenic activation of leucocytes by phytohemagglutinin, concanavalin A and lipopolysaccharide, was detected at 10 to 100-fold lower concentrations of p-chloroaniline than those which resulted in toxic effects.

Aniline Compounds↗
PubMed1994

Methemoglobinemia following ingestion of a monolinuron/paraquat herbicide (Gramonol)

A 59-year-old man ingested a mouthful of Gramonol with suicidal intent and was admitted to a local hospital six and a half hours later. It was noted that he looked "ashen grey" and was centrally cyanosed. The methemoglobin and plasma paraquat concentrations performed on arrival at the Regional Poisons Treatment Unit eight hours after paraquat ingestion were 52% and 1100 micrograms/L respectively; the administration of methylene blue reversed methemoglobinemia within two hours. The patient suffered extensive paraquat-induced oral, and probably esophageal, ulceration and developed multiple organ (particularly renal, respiratory and hepatic) failure and died some 10 days later. This is the most severe case of Gramonol poisoning reported both in terms of the amount of paraquat ingested and the concentration of methemoglobin formed. We believe that the methemoglobinemia in this patient was caused by monolinuron not paraquat.

Fatal Outcome↗
PubMedDate not supplied

[Adsorption of phenylurea derivative and chlorine-substituted aniline herbicides by microorganisms].

Adsorption of phenylurea derivatives and chlorosubstituted anilines by Pseudomonas and Aspergillus was studied. All these substances were adsorbed by the microorganisms in large quantities. The bacteria adsorbed more of these substances per biomass unit than the fungi. Adsorption of herbicides by the microorganisms is a physical process and is characterized by the same correlation as adsorption of herbicides by soil. Derivatives of phenylurea and chlorosubstituted anilines are easily washed from the cells with water. Conditions under which the substances were completely desorbed have been studied. Acetylation of 3,4-dichloroaniline by Pseudomonas aurantiaca results in desorption of 3,4-dichloroaniline from the cells of Pseudomonas boreopolis.

Adsorption↗
PubMedDate not supplied

Reaction of freshwater phyto- and zooplankton to pesticides.

The reaction of plankton to the toxic effect of pesticides is considered at four levels: the cell, the organism, the population, and the biocenosis. The basis for the methodological approach to evaluation of response at the cell level was the principle of phase reactions. Depending on concentration, the pesticides may either suppress or stimulate the plankton organisms. Temperature may be decisive intoxic effects (pesticides are effective in a range of 15 to 25 degrees C). Most pesticides having algacidal activity are effective in a range of concentrations of 1-10 mg/liter. Phytoplankton as a whole has a high buffer capacity with respect to pesticides. Changes in ratios of basic components of phytoplankton effected by pesticides most often lead to a change of the dominant. Analogical changes are characteristic also for zooplankton; pesticides lead to the elimination of water fleas from its composition. The stimulating effect of a low concentration of pesticides, changes in the functional activity of the components of bacterial plankton, and changes coupled with this in biogeochemical cycles of nitrogen and phosphorous as well as elimination of water fleas from the plankton promotes the development of "secondary" eutrophication, that is, an increase in the biomass of the phytoplankton.

Animals↗