Effects Of Toxic Substances Research Articles

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test Methods for Definition of Effects of Toxic Substances on Behavior and Neuromotor Function

Test Methods for Definition of Effects of Toxic Substances on Behavior and Neuromotor Function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Test methods for definition of effects of toxic substances on behavior and neuromotor function

Record linkage and the identification of long-term environmental hazards.

The long-term effects of toxic substances in man that have been discovered so far have involved gross relative risks or bizarre effects, or have stumbled upon by chance or because of special circumstances. These facts and some recent epidemiological evidence together suggest that a systematic approach with better methods would reveal the effects of many more toxic substances, particularly in manufacturing industry. Record linkage is a powerful tool because it makes possible the correlation of indicators of exposure with indicators of the biological effect of such exposure in the same persons or in their progeny even after considerable periods of time have elapsed. A system of linked records exists in England and Wales which is at present used by research workers to follow up samples of persons defined in various ways, e.g. in respect of exposure to a suspected toxic factor. In this way hypotheses about substances causing cancer or other lethal effects can be tested. It is suggested that there are two additional ways in which record linkage techniques could be used to identify substances with long-term toxic effects: the first would be by setting up a register of women employed in industry during pregnancy and linking this register to records of the occurrence of congenital malformations and of stillbirth or death in their children; the second would be to follow samples of workers in manufacturing industry, notably those engaged in the manufacture of products from raw materials including the chemical industry, to death and to the development of cancer. Regular analyses of material from these two systems of linked records would provide the basis for a monitoring system for certain gross effects of long-term toxic substances in man. There are two principal obstacles to further progress in this field. The first is the lack of a clear statement of public policy concerning the issues of confidentiality and informed consent in the use of identifiable personal records for medical research. A settlement is needed which defines the proper limits of their use in the interests of health with safeguards to privacy. The second obstacle is a lack of resources to improve the quality, accessibility and organization of the appropriate data.

Proceedings of a conference on Test Methods for definition of effects of toxic substances on behavior and neuromotor function

Proceedings of a conference on Test Methods for definition of effects of toxic substances on behavior and neuromotor function

The Epidemiologic Approach

Epidemiological studies rarely provide unequivocal data on the effects of toxic substances on human health. Unlike experimental studies, pertinent variables frequently cannot be controlled and some are often unknown. Nevertheless, these limitations can be dealt with by various facets of an epidemiological investigation. These include, the choice of a study design, selection of controls or comparison populations, evaluation of available data, statistical analysis, and the drawing of appropriate inferences from the data. Among the special problems that might be encountered in studies of the effects of cardiotoxic substances are, difficulties in establishing diagnoses, errors in death certificates, observer errors in electrocardiographic interpretations, and taking into account the effects of various risk factors known to be implicated in the etiology of cardiovascular diseases. In spite of various methodological problems and certain inherent limitations of epidemiological studies, they can, when properly conducted, make significant contributions to knowledge of disease etiology and provide the means of reducing the risk of a disease, even when its etiology is not completely known.

Symposium on Target Organ Toxicity: cardiovascular system. The epidemiologic approach.

Epidemiological studies rarely provide unequivocal data on the effects of toxic substances on human health. Unlike experimental studies, pertinent variables frequently cannot be controlled and some are often unknown. Nevertheless, these limitations can be dealt with by various facets of an epidemiological investigation. These include, the choice of a study design, selection of controls or comparison populations, evaluation of available data, statistical analysis, and the drawing of appropriate inferences from the data. Among the special problems that might be encountered in studies of the effects of cardiotoxic substances are, difficulties in establishing diagnoses, errors in death certificates, observer errors in electrocardiographic interpretations, and taking into account the effects of various risk factors known to be implicated in the etiology of cardiovascular diseases. In spite of various methodological problems and certain inherent limitations of epidemiological studies, they can, when properly conducted, make significant contributions to knowledge of disease etiology and provide the means of reducing the risk of a disease, even when its etiology is not completely known.

Cerebrospinal lesions resulting from invasion of canine heartworm larvae

In two cases of canine filariasis submitted to necropsy, a large number of worms ofDirofilaria immitis were found in the heart and pulmonary artery, although no neur-ological manifestations had been noticed during life time. Histological examinationrevealed, however, disseminated perivascular lesions resulting from the invasion ofheartworm larvae in the brain and spinal cord of them. Histopathological findings inthe central nervous system were as follows: (a) perivascular cell accumulations situatedprincipally in the Virchow-Robin space and (b) nodular cell accumulations, developedfrom the former, with tissue destruction in the neighborhood of the nodules.Chief elements forminag the cell accumulations were plasma cells and adventitial cells.Lesion (b) was probably caused by tissue desolation due to the mechanical or toxiceffect of larvae penetrating into the parenchyma and passing across the blood vessels, orby tissue reaction to toxic substances which had been produced by the degeuteration ordestruction of larvae penetrating into the parenchyma and acting as foreign bodies.Such nodular lesions may also be regarded as an evidence of the tissue reaction to thedestruction products of the nervous parenchyma. Lesion (a) was thought to be reactionto the inflow of toxic substances derived from immigrating larvae, into the lymphaticspaces, or to the exudation of toxic substances derived froxn mature parasites or toxicproducts produced by the former passing through the weakeuaed wall of blood vessels.In histopathogenesis of perivascular lesions, it should be taken into considerationthat edematous loosening in the wall of blood vessels of small diameter (weakness ofthe wall of blood vessels) is regarded as one of the favoring factors to allow the larvae totraverse blood vessels easily.As causes for weakness of the wall of the blood vessel may be considered the effectsof toxic substances and their products derived from the larva or mature parasite and themechanical effect of the larva. In addition, general nutritional di

Effect of Toxic Substances on Wild Life

Effect of Toxic Substances on Wild Life

Effects of Toxic Substances on Wild Life

Effects of Toxic Substances on Wild Life