AAB Basic Knowledge-MT practice questions and answers.

Centrifuges (4) #1- Table top centrifuges are used in clinical labs to separate cells from serum or plasma. #2- Micro-centrifuges are small centrifuges used for small plastic conical containers with an integral snap cap. #3- High speed centrifuges reach speeds b/w 17,000 & 30,000 rpm. #4- Ultra Centrifuges are high speed centrifuges (15,000 rpm). Small air-driven to separate chylomicrons from serum. Pipettes types (3) 1. Automated pipettes 2. semi-automated micro-pipettes 3. Glass pipettes Automated Pipettes used to prep many samples for analysis and can be apart of an automated analyzer. Semi-automated micro-pipettes contain or deliver small volumes of liquid ranging from 1 to 1000ul. A. air displacement- forward and reverse mode b. positive displacement glass pipette A. transfer/ volumetric pipettes have a bulb in the middle with tapered delivery tip. B. measuring/ graduated pipettes are uniform in diameter with tapered delivery tip. C. To contain (TC) or rinse out pip. must be rinsed with appropriate solvent after the initial liquid has been drained. D. To deliver (TD) pip are filled and allowed to drain by gravity. Most be held vertically and top against the side of receiving vessel. E. To deliver/ blow-out pip are filled and allowed to drain, after which the remaining fluid in the tip is blown out. Identified by the two frosted bands near the moth piece. Temperature-regulated equipment (4) A. Heat blocks/ water baths (36C-38C) B. Room Temperature (20C-24C) C. Refrigerators: Lab: 2C-8C Blood Bank: 1C-6C D. Freezers: Lab: < -18C Blood Bank: < -65C Microscopes (6) 1. Bright- field microscopy 2. Dark-field Microscopy 3. Electron Microscopy 4. Fluorescent Microscopy 5. Phase-contrast Microscopy 6. Polarized Microscopy Bright- Field Microscopy Simplest of all light microscopy. Sample illumination is via white light from below and observed from above. Limitations include low contrast of most biological samples and low apparent resolution due to the blur of out of focus material. Most commonly used. Dark Field Microscopy technique from improving the contrast of unstained transparent specimen. Illumination uses a carefully aligned light source to minimize the quantity of directly transmitted (unscattered) light entering the image plane, collecting only the light scattered by the sample. Can dramatically improve image contrast, especially of transparent objects. However, the technique does suffer low light intensity in the final image of many biological samples and continues to be affected by low apparent resolution. Electron microscopy uses an electron microscope in which electrons illuminate a specimen and create an enlarged image. They have much greater resolving power than light microscopes and can obtain much higher magnifications. Both electron and light have resolution limitations, imposed by their wavelength. The electron uses electrostatic and electromagnetic lenses in forming the image by controlling the electron beam to focus it at a specific plane relative to the specimen in a manner similar to how a light microscope uses glass lenses to focus light on or through a specimen to form an image. Fluorescent Microscope uses fluorescence instead of or in addition to reflection and absorption to view the object. When certain compounds are illuminated with high-energy light, they then emit light of a different, lower frequency. This effect is known as fluorescence. Since the emission differs in wavelength (color) from the excitation light, a fluorescent image ideally shows only the structure of interest that was labeled with the fluorescent dye. Different dye can be used to stain different structures. Phase-contrast Microscopy widely used technique in which small phase shifts in the light passing through a transparent specimen show differences in refractive index as difference in contrast. contrast is excellent. however, frequently a halo is formed even around small objects, which obscures detail. The microscope objective has special optical properties: it first of all reduces the direct light in intensity, but more importantly, it creates an artificial phase difference. As the physical properties of this direct light have changed, interference with the diffracted light occurs, resulting in the phase contrast image. Polarized microscopy technique which produces only transmitted polarized light. This means that light is provided from the bottom and is transmitted through the thin section of birefringent specimen on a microscope slide. Applications for polarized light microscopes include medical applications, such as viewing microscopic crystals in urine. Parts and function of compound microscope (14) 1. eyepiece lens: lens at the top you look thru 10X 2. Tube: connects the eyepiece to obj lens. 3. Arm: support the tube and connects the base. 4. Base: bottom of the microscope. 5. light source: sends light up through the diaphragm and through the slide for viewing. 6. stage: slides are placed. 7. Nose-piece: holds the objective lenses and rotate. 8. condenser lens: focus the light onto the specimen and can be moved up or down. 9. iris diaphragm:a rotating disk under the stage. used to vary intensity and size of the cone of light. 10. course adjustment: used to focus the slide under low power 11. fine adjustment: used to focus the slide under high power and oil immersion. 12. low-power objective: usually 10X 13. high-power objective: 40X immersion objective: 100X