Advanced Histology Techniques Quiz: Tissue Processing and Analysis

Dehydrating agents are substances that remove water or moisture from another compound. Ethanol, methanol, isopropanol, acetone, and universal agents are commonly used as dehydrating agents due to their ability to absorb water. On the other hand, water, sodium chloride, and sugar are not dehydrating agents as they do not possess the necessary properties to remove water from a compound.

Clearing agents are substances used in laboratory procedures to make tissues transparent for microscopic examination. The correct examples provided are commonly used clearing agents, while the incorrect answers do not serve this purpose.

When tissues are not fixed fast enough, a series of detrimental changes occur due to various processes like autolysis and putrefaction resulting in the loss of structural integrity and function.

Formalin pigment can be removed by adding alcoholic picric acid. It is predominantly seen in bloody tissues due to the chemical reaction between formalin and blood components.

Fixatives are used in histology to preserve tissue structure for microscopic examination. Potassium dichromate and osmium tetroxide are known for making lipids insoluble, while the incorrect answers do not have the same property when used as fixatives.

Mercury pigment can be effectively removed with Lugal's iodine solution, followed by sodium thiosulphate, due to their ability to chemically react with mercury compounds and facilitate their removal.

A polychromatic dye is not a single color dye, but rather a combination of different colored dyes. It is not specifically derived from plants, nor is it limited to being synthetic.

Paraffin has a melting point range between 56 to 58 degrees Celsius, but often a few degrees higher temperatures are used for the melting bath. The incorrect answers provide variations in temperature outside of the typical range of paraffin melting point.

When distinguishing between additive and non-additive fixatives, it is essential to understand how these substances interact with proteins in the fixation process. Additive fixatives bind to proteins, rendering them insoluble, while non-additive fixatives do not bind to proteins. The examples provided for each type of fixative further demonstrate their respective characteristics.

Acetic acid is added to fixative solutions to precipitate nucleic acids, leading to improved nuclear detail in tissue samples. This aids in preserving the cellular structure for microscopic examination.

Bouin's fixative is composed of picric acid, formaldehyde, and acetic acid specifically used for trichrome stains. The incorrect answers provided contain different combinations of chemicals and are used for other types of special stains.

Zenker's fixative is a histological fixative composed of mercuric chloride, potassium dichromate, sodium sulphate, and formalin. The other options provided do not represent the correct components of Zenker's fixative.

Certain fixatives like Zenker's or B5 contain components that can interfere with specific staining techniques. In the case of silver stains, the mercury present in the fixative can prevent the proper binding of silver, rendering the stain ineffective in highlighting specific tissue components.

A chromophore is specifically related to absorbance in the visible spectrum due to its molecular structure, making the incorrect answers irrelevant to the concept.

An auxochrome is a group of atoms that alters the light-absorbing properties of a chromophore. The examples provided in the correct answer showcase positive (NH4+) and negative (SO3-, COO-, O-) auxochromes.

Lysochrome or lipochrome dyes/stains have unique characteristics that differentiate them from true dyes, such as lacking an auxochrome. Oil Red O is a common example of this type of fat stain.

An aqueous mounting medium is specifically used for fat stains such as Oil Red O, and it is impermanent, meaning it does not harden. It is not typically used for permanent mounting of H&E stained slides, immunofluorescence staining, or live cell imaging samples.

Coagulant fixatives form an open network in tissues for easy processing, while non-coagulant fixatives create a dense gel. Examples provided in the correct answer demonstrate this difference.

The correct answer is that 37% formaldehyde is present in 100% formalin, and we use a 1:10 (10%) working solution which would contain 3.7% formaldehyde. The incorrect answers provided different percentages of formaldehyde in 100% formalin and corresponding working solution concentrations.

Paraformaldehyde precipitate can be reversed by using heat to dissolve the precipitate, or prevented by adding methanol to the solution. Dissolving in water, increasing pH, or using a stronger fixing agent would not effectively address the issue.

Formaldehyde fixation involves the initial step of hemiacetal formation followed by the formation of a methylene bridge, leading to stable covalent bonding.

Mercury works by crosslinking thiols (SH) groups in proteins, which can disrupt normal cellular function and tissue structure. This ultimately leads to tissue 'fixing' or hardening due to the altered protein structure.

B5 fixative is composed of mercuric chloride, sodium acetate, and formalin. It is commonly used for preserving bone marrows for histological examination.

When fixing tissue samples, the desired ratio of fixative volume to tissue is generally 15-20 : 1, meaning that you should aim to have 15 to 20 times more fixative than tissue for optimal preservation.

Weak forces such as Van der Waals, H-bonds, and hydrophobic bonds are intermolecular forces that play a key role in molecular interactions. These forces are weaker than ionic, covalent, or metallic bonds, which involve stronger intramolecular interactions.

Decalcifying agents are substances used to remove calcium deposits from materials. The correct answer options are commonly used for this purpose, while the incorrect answers are not typically used as decalcifying agents.

In the context of sharing electrons, covalent bonding occurs when electrons are shared between elements leading to a stable and relatively weak attraction. On the other hand, coordinate covalent bonding occurs when one element donates both electrons to bond with another element, creating a strong and irreversible bond.

Leuco dyes are a type of colorless dye that undergo a chemical reaction to become colored. They are commonly used in applications where color change is desired.