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Bioassay

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Bioassay is a shorthand commonly used term for biological assay and is a type of scientific experiment. Bioassays are essential in the development of new drugs, and monitoring pollutants in the environment.

Biological Standardisation or Bioassay's are procedures by which the potency or the nature of the substance is estimated by studying its effects on Living matter.

Introduction

Bioassays are typically conducted to measure the effects of a substance on a living organism. Bioassays may be qualitative or quantitative. Qualitative bioassays are used for assessing the physical effects of a substance that may not be quantified, such as abnormal development or deformity. An example of a qualitative bioassay includes Arnold Adolph Berthold's famous experiment on castrated chickens. This analysis found that by removing the testes of a chicken, it would not develop into a rooster because the endocrine signals necessary for this process weren't available. Quantitative bioassays involve estimation of the concentration or potency of a substance by measurement of the biological response that it produces. Quantitative bioassays are typically analyzed using the methods of biostatistics.

Definition

"It is the comparable estimation of the nature, constitution or potency of the active principles with that of the standard drug, by means of the reaction on a living matter such as whole animal, isolated tissue or organism"

Purpose

  1. measurement of the pharmacological activity of new or chemically undefined substances
  2. investigation of the function of endogenous mediators
  3. determination of the side-effect profile, including the degree of drug toxicity
  4. measurement of the concentration of known substances (alternatives to the use of whole animals have made this use obsolete)
  5. assessing the amount of pollutants being released by a particular source, such as wastewater or urban runoff.

Types

Bioassay's are of two types:

Quantal

Tha quantal assay is "all or none Phenomenon". For example: Insulin induced hypoglycemic convulsive reaction and on the cardiac arrest caused by digitalis. In both the cases, the end point is an all or none response eg- either convuslion occurs or doesnt occur,, similarly is with cardiac arrest.

Graded

These are based on the observations that there is a proportionate increase in the observed response with a subsequent increase in the concentartion or dose. The parameters employed in such bioassays are based on the nature of the effect the substance is expected to produce. For example: contraction of smooth muscle preparation for assaying histamine or the study of blood pressure response in case of adrenaline.

The graded Bioassay can be performed by employing any of the below mentioned techniques. The choice of the procedures depends on the:

  1. precision of the assay demands
  2. quantity of the sample available
  3. availability of the experimental animals

Procedures

  1. Matching Bioassay
  2. Interpolation Method
  3. Bracketting Method
  4. Multiple Point Bioassay
  5. Six Point Assay

Environmental bioassays

Environmental bioassays are generally a broad-range survey of toxicity, and a toxicity identification evaluation is conducted to determine what the relevant toxicants are. Although bioassays are beneficial in determining the biological activity within an organism, they can often be time-consuming, laborious, and organism-specific factors may result in data that isn't applicable to others in that species. For these reasons, other biological techniques are often employed, including radioimmunoassays. See bioindicator.

Water pollution control requirements in the United States require some industrial dischargers and municipal sewage treatment plants to conduct bioassays. These procedures, called whole effluent toxicity tests, include acute toxicity tests as well as chronic test methods. The methods involve exposing living aquatic organisms to samples of wastewater.[1] [2]

See also

References

  1. ^ United States Environmental Protection Agency (EPA). Washington, DC. "Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms." October 2002. Document No. EPA-821-R-02-012.
  2. ^ US EPA. "Whole Effluent Toxicity / Clean Water Act Analytical Methods." Accessed December 16, 2008.
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