Mitochondrial electron microscope photo observation experiment

Summary

Electron microscopes commonly used are transmission electron microscope (TEM) and scanning electron microscope. Compared with the light microscope electron microscope with an electron beam instead of visible light, with electromagnetic lenses instead of optical lenses and the use of fluorescent screen will be invisible to the naked eye electron beam imaging.

Operation method

Mitochondrial electron microscope photo observation experiment

Principle

Mitochondria with the endoplasmic reticulum, in addition to prokaryotic cells and mammalian mature erythrocytes, all other fine stage mitochondria (mitochodri). The number, shape and size of mitochondria in a cell often due to cellular and physiological conditions and other different and large differences, such as a certain algae in only one mitochondria, corn root products in the 100~3000, while the sea urchin oocytes in the mitochondria up to 300,000; in the optical microscopy of the mitochondria were linear, granular, rod-shaped, etc., so it is called the mitochondria; the size of the general diameter of 0.5~1.0 μm. electron microscopy Under the electron microscope, mitochondria can be seen to be encapsulated by a double layer of closed unit membrane, containing mainly proteins (stroma, mati), the inner and outer membranes are not connected to each other, and they are 40~80A between each other.

Materials and Instruments

Rabbit
Janus Green B Stain Ringer's solution
Microscope Slide Coverslip

Move

I. Observation of mitochondria in light microscopic sections
1. Light microscopic section of a rabbit hepatocyte stained with Janus Green B. The mitochondria in the hepatocyte appear as blue-green granules.
II. Electron micrographic observation of mitochondria
1. The shape and number of mitochondria vary from cell to cell. Mitochondria are of various shapes, such as round, oval, dumbbell-shaped and rod-shaped. The number of mitochondria is related to the cell type and the physiological state of the cell, and mitochondria tend to accumulate in the areas of the cell where the physiological function is strong.
2. The number and distribution of mitochondrial ridges are diverse. They are generally arranged perpendicular to the long axis of the mitochondria, but ridges arranged parallel to the long axis of the mitochondria can also be seen. The ridges are vesicular or tubular in cross section. The number of ridges is strongly related to the strength of cellular respiration.
3. Here are three electron micrographs of ultrathin sections of mitochondria:

(1) The first is an electron micrograph of mitochondria in mouse renal tubular epithelial cells, visible mitochondria are elliptical and rod-shaped, surrounded by a double membrane, the inner membrane protrudes inward into a flat plate-like ridges, the ridges are aligned perpendicularly to the long axis of the mitochondria, and the renal tubular epithelium requires energy for reabsorption, and the number of mitochondria is high.

(2) The second one is the mitochondria in the synapse of rhesus monkey spinal cord. It can be seen that the mitochondria are small in size and large in number, and the ridges are arranged in concentric circles with the mitochondria.

(3) The third one is the mitochondria in the interstitial cells of the mouse testis. The ridges of the mitochondria are branched tubes, which appear as single membrane vesicles in the photo

Caveat

Before using a transmission electron microscope to observe a biological sample, the sample must be pre-treated. Scientists use different treatments depending on the requirements of the study.Fixation: In order to preserve the sample as much as possible glutaraldehyde is used to harden the sample and osmium acid is used to stain the fat.Cold fixation: The samples are flash frozen in liquid ethane so that the water does not crystallize and forms amorphous ice. Samples preserved this way have less damage, but the images have very low contrast.Desiccation: Ethanol and acetone are used instead of water.Padding in: The sample is padded in so that it can be divided.Dividing: The sample is cut into thin slices using a diamond blade.Staining: Heavier atoms such as lead or uranium have a higher ability to scatter electrons than lighter atoms and can therefore be used to improve contrast.

Common Problems

Resolving power is an important index of the electron microscope, the resolving power of the electron microscope it can distinguish the minimum distance between two adjacent points to express, that is, called the highest point of the instrument's resolution: d = δ. Obviously, the higher the resolution, that is, the value of d (for the unit of length) the smaller, then the instrument is able to distinguish the details of the object to be observed is also the more rich, that is to say, the instrument's ability to distinguish or distinguish the skills The stronger.

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