Organ target

Control of secretion of anterior pituitary hormones also includes inhibition by hormones produced by target organs. For example, CRH stimulates the anterior pituitary to secrete ACTH, which in turn stimulates the adrenal cortex to secrete corticosteroids. Corticosteroids then feed back to inhibit the secretion of ACTH. Feedback mechanisms are important for the control of most hormones. For example, insulin (qv) secretion from the pancreas increases in response to increased blood glucose resulting from ingestion of a meal. Insulin increases tissue uptake and metaboHsm of glucose, which lowers blood glucose and in turn reduces insulin secretion. 

Compound CAS Registry Number LD50 log(l/D, )" Principal target organ... 

It is important to appreciate that the magnitude of the absorbed dose, the relative amounts of bio transformation product, and the distribution and elimination of metaboUtes and parent compound seen with a single exposure, may be modified by repeated exposures. For example, repeated exposure may enhance mechanisms responsible for biotransformation of the absorbed material, and thus modify the relative proportions of the metaboUtes and parent molecule, and thus the retention pattern of these materials. Clearly, this could influence the likelihood for target organ toxicity. Additionally, and particularly when there is a slow excretion rate, repeated exposures may increase the possibiUty for progressive loading of tissues and body fluids, and hence the potential for cumulative toxicity. 

The presence of air pollutants in the surrounding ambient air is only one aspect of determining the impact on human beings. An air pollution instrument can measure the ambient concentration of a pollutant gas, which may or may not be related to its interaction with individuals. More detailed information about where and for how long we are breathing an air pollutant provides additional informahon about our actual exposure. Finally, how an air pollutant interacts with the human body provides the most useful information about the dose to a target organ or bodily system. 

Tlie respiratory system is tlie main target organ for vapour, gas or mist. Readily-soluble cheirticals, e.g. chlorine or phosgene, attack the upper respiratory tract less soluble gases, e.g. oxides of nitrogen, penetrate more deeply into the conducting airways and, in some cases, may cause pulmonary oedema, often after a time delay. 

Caneer is a disorder of the body s eontrol of die growth of eells. The disease may be genetie or influeneed by life style or exposure to eertain ehemieals, termed eareinogens. For a list of examples of human ehemieal eareinogens, and the relevant target organs, refer to Table 5.10. 

Table 6. Target Organ Effects Categorized Under the Hazard Communication Act...

When working with chemicals that have target organ effects it is critical to prevent exposure. This is especially true if you have a pre-existing condition, disease, or injury to that particular organ. Read the MSDS to fmd out the most effective personal protection equipment (PPE) for dealing with the chemical and be certain to minimize release of the chemical in the first place. 

Inhalation is the most rapid route, immediately introducing toxic chemicals to respiratory tissues and the bloodstream. Once admitted to the blood through the lungs, these chemicals are quickly transported throughout the body to contact all organs. In many cases, chemicals accumulate in a target organ. 

Contains the health hazards and risks, toxicological data, and first aid procedures Exposure routes and limits signs and symptoms target organs and medical conditions aggravated by exposure. 

Hazard characterization, or dose-response characterization, by using experimental animals to reveal target organs and toxic doses, and the shape of the dose-response curve... 

Physico-chemical characteristics greatly determine the entry of chemicals into the body, and also their behavior in the body (distribution, biotransformation, and excretion). Therefore, the physico-chemical characteristics of a compound affect its dose and its subsequent effects by determining how quickly and extensively a chemical reaches the target organs. In the following section, some of these important physical-chemical characteristics of chemicals will be discussed. 

Water-soluble compounds are naturally easily transported in the blood. Non-soluble compounds are usually transported bound to plasma proteins (albumins). This binding is reversible in most cases but may vary remarkably. The degree of protein binding may vary between 50% and 99%. The proportion of the free (unbound) compound in the circulation is the amount of the compound that can reach the tissues and thus the target organs. Very lipid-... 

Suhacute toxicity Rats/mice 2. 2 weeks Delayed effects, target organs... 

Subchronic study Rats/mice/dogs/rabbits 6 months Target organs, delayed effects... 

Target organ A specific organ where the toxic effect of a substance is manifested. 

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