Microscopy

Scientists in a laboratory are studying celiac disease using chickens as a model system.
The main focus is to determine whether celiac disease affects goblet cells in the chicken intestine.

Goblet cells are a specific type of cell found in the intestines that secrete mucus.
Understanding the morphology and number of goblet cells is essential in the context of celiac disease.

The researchers need to analyze their samples using microscopy.
- They must determine if the size and shape of goblet cells can be observed under a microscope using the Mallory staining technique.
A researcher has already prepared a sample for microscopy using a process displayed on a big wall screen.
It is necessary to review the procedure for sample preparation for microscopy.

Multiple Choice Question: What is the purpose of staining biological samples?
- Option A: Enabling sample collection.
- Option B: Facilitating sectioning of the sample.
- Option C: Adding contrast and labeling specific structures. (Correct Answer)
- Ensuring the light can pass through the sample.

Staining is crucial because most biological samples have low contrast, allowing light to pass mostly through without obstruction.
Different stains and dyes bind to various structures in the biological sample, enhancing the visibility of the morphology and abundance of those structures.

Assembling the light microscope is necessary before usage.
The microscope parts are located on the workbench; you need to select each part and place it correctly to match the image on the screen.
Note: Interaction with items is not possible when holding an item.

The microscope camera captures and displays the image on a screen adjacent to the microscope.
- This allows for saving images known as micrographs.
The microscope stage is where the prepared slide is placed.
- The stage is adjustable for focusing on the slide.
The eyepiece lenses provide a magnification factor of 10.

When using a 5x objective, the total magnification becomes 50 times (5 * 10).
Concept of Parfocal Objectives:
- Multiple Choice Question: What does it mean to have parfocal objectives?
- Option A: The sample remains in focus when the stage is moved laterally.
- Option B: The whole sample is in focus.
- Option C: The sample remains in focus when the objectives are changed. (Correct Answer)
- Option D: Focusing on the sample is done automatically.
Parfocal objectives require only minor manual corrections when changing objectives.

The slide containing the specimen is located in the microscope slide tray on the left.
You can move the stage to examine different areas of the sample via screen arrows; other microscopes may use buttons or dials.
Higher magnifications allow for clearer views of individual cells and their internal structures.
- At high magnifications, collagen appears as a stringy blue mass and cell nuclei as dark red against a light pink background.
- Objective to locate goblet cells secreting mucus into the lumen, highlighted with an arrow on screen.

Increase in magnification clarifies the cellular layers observed.
Understanding refraction—light bending as it moves from one medium (glass) to another (air)—is critical.
- Refraction can distort images, especially at higher magnifications.
- At low magnification, distortion is minimal; however, at 100x magnification, immersion oil is required to minimize refraction.

Immersion oil has a similar refractive index to glass (approximately 1.5) to reduce light refraction and improve image resolution.
Multiple Choice Question: Which factor is improved by adding immersion oil?
- Option A: Contrast.
- Option B: Transparency.
- Option C: Magnification.
- Option D: Resolution. (Correct Answer)

At the highest magnification, observe the epithelial cells’ morphology including dark red nuclei against light pink cytoplasm.
Focus on the highlighted goblet cell to assess morphology and function.

Goblet cell counts and morphology can be evaluated based on the Mallory staining results.
- Mallory staining allows researchers to distinguish cytoplasm, nucleus, and mucus, providing insight into goblet cell characteristics.
For enhanced visualization, one can employ fluorescent tags on proteins or antibodies.
- This approach offers high-contrast images of cellular components, e.g., viral particles in magenta, cells in yellow, and nuclei in cyan.

The limitations of light microscopy are due to visible light's wavelength (approx. 200 nanometers), affecting resolution.
The use of electron microscopy can overcome this limitation as electrons have much shorter wavelengths.
- Different sample preparation and microscopy techniques are required for electron microscopy.
- Electron microscopy images result in black and white due to the absence of colors in electron imaging.

Choice of microscopy type depends on the research question:
- Fluorescence microscopy for high contrast.
- Electron microscopy for superior resolution.
- Light microscopy for easily stained structures.
This training session concludes with an invitation for further discussion on other microscopy techniques.