Practical Laboratory Instruments PDF

Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed Types of microscope 1. Light microscope: A. Simple microscope B. Compound microscope 2. Phase contrast microscope. 3. Dar...

Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed Types of microscope 1. Light microscope: A. Simple microscope B. Compound microscope 2. Phase contrast microscope. 3. Dark field microscope. 4. Fluorescence microscope. 5. Electron microscope: A. Transmission electron microscope B. Scanning electron microscope) 6. Stereo microscope: (dissecting microscope) 7. Digital microscope. 1. Light microscope It is the most common microscope, which uses light to pass through the sample to produce the image. A. Simple microscope: the oldest design of light microscope to magnify images of small samples. B. Compound microscope: is a light microscope, which is routinely used in medical laboratories of hospitals or health centers. 1 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed 2. Phase contrast microscope It is widely used for examining in the biology and medical research. It is a type of light microscopy that enhances contrasts of transparent and colorless objects by influencing the optical path of light. It is able to show components in cells, bacteria, parasites (without killed them by staining) and made it possible for biologists to study living cells and how the cells division, which would be very difficult to see in an ordinary light microscope. 3. Dark field microscope A microscope that has a special condenser and objective with a diaphragm that scatters light from the cells observed so the cells appears bright on a dark background. Applications:  Viewing blood cells.  Viewing bacteria.  Viewing clearly the structure of the cells. Advantages: 1. Extremely simple to use. 2. Inexpensive to set up. 2 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed Disadvantages: Limited colors (just black and white). 4. Fluorescence microscope It is an optical microscope that uses fluorescence and phosphorescence. In addition to reflection and absorption to study properties of organic or inorganic substances and Antigen - Antibody reaction (Ag-Ab reaction). The fluorescence microscopy use ultra - violet light (UV light), which has a very short wavelength and is not visible to the eye. This light activates specific parts of the sample (organisms, cells, particles) that interact with the fluorescent dye called (fluorochrome). The sample is dyed with special shining pigments that make the sample parts glow. Special optical filters are used to absorb colors at all wavelengths, except the wavelength of the dye used. 3 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed 5. Electronic Microscope The electron microscope is a type of microscope that uses a beam of electrons to create an image of the specimen. It is capable of much higher magnifications and has a greater resolving power than a light microscope, allowing it to see much smaller objects in finer details. They are large, expensive pieces of equipment, generally standing alone in a small, specially designed room and requiring trained personnel to operate them. All electron microscopes use electromagnetic and/or electrostatic lenses to control the path of electrons. Glass lenses, used in light microscopes, have no effect on the electron beam. The faster electrons travel that have shorter wavelength. The resolving power of a microscope is directly related to the wavelength used to form an image (Reducing wavelength increases resolution). Although modern electron microscopes can magnify objects up to about (two million times). Types of Electron Microscopes A. Transmission Electron Microscope (TEM) The electron beam that has been partially transmitted through the very thin (and so semitransparent for electrons) specimen carries information about the structure of the specimen. 4 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed B. Scanning Electron Microscope (SEM) Unlike the TEM, the electron beam is scanned across the surface of the sample with detectors building up an image by mapping the detected signals with beam position. Sample Preparation: 1. Fixation: Fixation of the specimen stabilizes the cell Fixation can be done through two methods as follows: a) Chemical fixation: This method is used for stabilizing biological samples. Chemical substances are used to cross link protein molecules with nearby molecules. The most frequently used chemical in this method is glutaraldehyde. b) Cryofixation: This method involves rapid freezing of the sample in either liquid nitrogen or liquid helium. The water content in the sample thus gets transformed into ice form. 2. Dehydration 3. Embedding 4. Sectioning 5. Staining 6. Freezing 7. Sputter Coating Disadvantages of Electron Microscope: 1. Electron microscopes are very expensive to buy and maintain. 2. Technique not easy to use. 6. Stereo microscope (Dissecting microscope) This microscope is designed for low magnification to observe the sample, typically using light to produce an image. Used to exam insects and help in anatomical dissection. 5 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed 7. Digital microscope It is a traditional microscope that uses a digital camera to output an image to a monitor. Slide and Cover slide A microscope slide: is a thin flat piece of glass, typically 75 by 26 mm (3 by 1 inches) and about 1 mm thick, used to hold objects for examination under a microscope. Cover slides: Microscope slides are often used together with a cover slip or cover glass, a smaller and thinner sheet of glass that is placed over the specimen. 6 Practical Laboratory Instruments First Class Lab -2&3 Assist. Lec. Omar A. Mahmoud Assist. Lec. Hayder Ahmed 7