MicroscopesBlog: Expert's reviews, news, notes on Microscopes, Centrifuges, Lab Coats, Pipettes, Lab Safety, & more Lab Products!
Friday, April 30, 2010
Cell Wall
The bacterial cell wall is a semirigid structure that gives the cell structure. Bacterial cell walls differ from the cell walls of eukaryotic cells mainly because of the presence of peptidoglycan. Peptidoglycan consists of two sugars: N-acetylglucosamine and n-acetylmuramic acid along with chains of amino acids. The two sugars alternate forming a carbohydrate backbone. Peptide side chains of four amino acids attached to the n-acetylmuramic acid are crosslinked to form a macromolecule of the cell wall. Gram positive bacterial also contain polysaccharides called teichoic acids while acid fast bacteria contain mycolic acid in addition to peptidoglycan. Gram negative bacteria have peptidoglycan but only in thin layers. These cells have a lipoprotein, lipopolysaccharide, and a phospholipid outer membrane surrounding their peptidoglycan layers. A periplasm is found between the outer membrane and the plasma membrane. When the cell wall disintegrates in the host's bloodstream the lipid portion of the cell wall is released as an endotoxin that can cause illness. Berkshire, Helix Medical, and North Safety provide products used in microbiology laboratories worldwide.
Posted by Paul at 12:00 PM Read Article 0 comments 
Friday, April 23, 2010
Flagella
A flagellum (singular form of flagella) is a tail like structure that extends from the cell body of prokaryotic and eukaryotic cells. This tail like structure functions in locomotion and allows the cell to advance in various directions. Flagellar filaments are composed of a protein called flagellin. The base of the flagellar filament widens to a hook and attached to this hook is a basal body. The basal body anchors the flagellum to the cell wall and plasma membrane. The basal body of gram negative bacteria is anchored at the cell wall and plasma membrane however in gram positive bacteria it is anchored only at the plasma membrane. Flagella are arranged in one of 4 basic ways: monotrichous (single flagellum), lophotrichous (two ore more polar flagella at the end of the cell), amphitrichous (a single flagellum at each end of the cell), and peritrichous (flagella distributed all over the cell). Flagella can spin counter clockwise or clockwise producing directional movement. Movement to or from a stimulus is called taxis. The stimulus may be chemicals (chemotaxis) or light (phototaxis). Axygen, Pall, and Wheaton supply products used in microbiology laboratories where the flagellum is researched.
Friday, April 16, 2010
Eukaryotic Cell
The eukaryotic cell differs from the prokaryotic cell in several ways. The cell wall of eukaryotic cells does not contain peptidoglycan. Algae have cellulose in their cell walls, fungi have chitin in their cell walls, and the cell walls of yeast have have polysaccharides like glucan and mannan. In animals the plasma membrane is covered by carbohydrates called the glycocalyx. Many enzymes are located in organelles thanks to the presence of a membrane. The nucleus is one of these membrane bound organelles and is surrounded by a nuclear envelope. The endoplasmic reticulum is a network of flattened sacs or cisterns. It function is to make and store lipids and proteins and to transport them. The golgi apparatus is similar to the endoplasmic reticulum in that it transports substances to other areas of the cell via vesicular transport. Mitochondria are the the powerhouses of the cell. Enzymes in the membrane of the mitochondria are responsible for producing energy for the organism. Contec Inc, Mediatech, and Steris supply products used in research involving eukaryotic cells.
Monday, April 12, 2010
Cameras for Microscopes
In the past a microscopist had to know how to draw. Documentation was necessary and the only camera suitable for a microscope was the human eye. The camera lucida drawing tool was the standard aid for reproducing images from the microscope until very recently. Now we can reproduce the image from microscopes with an SLR camera or with a digital ccd camera for microscopes. The microscope camera is designed for attaching to either the eye piece of a binocular or monocular microscope or to the third port of a trinocular microscope. With either of these arrangements the eyepiece magnification is replaced with the camera magnification. If the image is sent from a ccd camera to a computer screen the magnification is the diagonal of the computer screen divided by the ccd chip size. multiply this number by the objective magnification and you have the approximate magnification on the computer screen.
Microscopes.com carries many choices for microscope cameras from simple ones for kids to 5 mega pixel cameras with measuring software. An example of a simple camera is the Konus 5829. this is a 1.2 mega pixel camera with adapters to fit in the eyepiece of any DIN compound or stereo microscope, no extra adapters needed. A cool choice for a classroom microscope camera is the Celestron 44430. This can send images to a computer, or if a computer isn't near the image can be sent to an optional SD card. More sophisticated cameras come from Unico and Motic. Motic cameras can be purchased with measuring software for image analysis and industrial quality control. The microscope camera adapters necessary for using the Motic and Unico microscope cameras would be specific to the microscope.
Friday, April 09, 2010
Prokaryotic Cell
Bacteria range in size from 1 to 10 microns in diameter and have a cell wall made mostly of peptidoglycan. Peptidoglycan consists of two sugars, N-acetylglucosamine and N-acetylmuramic acid as well as chains of amino acids. The two sugars alternate with each other forming a carbohydrate backbone. This size of these cells and the presence of the cell wall are two main differences between prokaryotic cells and eukaryotic cells. One other major difference between prokaryotic cells and eukaryotic cells is the presence of membrane bound orangelles in eukaryotes. The general term for substances surrounding bacterial cells is glycocalyx which is a polysaccharide, polypeptide, or both. If it is organized and tightly attached is called a capsule. If it is unorganized and loosely attached, the glycocalyx is called a slime layer. Dade Behring, Heathrow Scientific, and Ohaus all supply products used for prokaryotic cell related research.
Thursday, April 08, 2010
Microscopy and Measurement
Biological microscopes are often used to measure artifacts, cells, cellular components (i.e. nuclear diameter) and other features as necessary using an eyepiece reticle. Typically, the objectives used on even a very high end research microscope do not exhibit exact magnification(s). The actual magnification values may vary as much as 2-3% so that a 10X objective, for example, may in reality be as low as 9.7x or as high as 10.3x. Clearly this will affect the accuracy of any measurements that are made and the variation may be significant depending on the ultimate use of the values collected. This potential source of error is easily overcome by calibrating the objective/eyepiece reticle set using a stage micrometer. Stage micrometers are quite accurate and can be acquired with a calibration certificate traceable to NIST, JIS, DIN or other recognized national standards organizations. Each objective must be individually calibrated, but once done, the values remain valid as long as the microscope set-up remains intact and unchanged. The procedure and mathematics are quite simple and step by step instructions are available either online or in printed hardcopy. In essence, the graduations in the eyepiece reticle are compared to those on the stage micrometer and a correction factor is calculated. Once the correction factor is determined for each objective a spreadsheet can be easily created to correct the "raw" readings. NIKON and UNICO are two of the many microscope manufacturers that offer stage micrometers for use in quantitative microscopy.Tuesday, April 06, 2010
Lab Shaker
IKA is a manufacturer of orbital shakers, one of them being the Lab Dancer. The lab dancer was designed to mix small test tube samples without touch function. This particular shaker is small, compact and reliable. It will fit small containers up to 30mm in diameter, such as test tubes, centrifuge tubes, and Eppendorf beakers. It has a fixed speed of 2800 rpm's. The type of movement on this unit is orbital. You should only use test tubes that are closed. The voltage is 120-240V selectable. Other brand names of laboratory shakers are, Eberbach, Unico, and Barnstead.Monday, April 05, 2010
Objects in 3D
We are fascinated by 3D on the big screen. What about 3D of the tiny world of 
insects, flowers, and computer chips? If you wish to see in 3D and magnify at the same time you must use a stereo microscope. A stereo microscope magnifies an object for each eye about 10 to 12 degrees apart; this mimics the separation of view in the human eye which makes it possible for us to see in 3D. A stereo microscopes is also called a dissecting microscope. Stereo microscope magnification is as it would be in nature, not inverted like the magnification of compound microscopes. The long working distance and the correct image makes it possible to work under a stereo microscope.
insects, flowers, and computer chips? If you wish to see in 3D and magnify at the same time you must use a stereo microscope. A stereo microscope magnifies an object for each eye about 10 to 12 degrees apart; this mimics the separation of view in the human eye which makes it possible for us to see in 3D. A stereo microscopes is also called a dissecting microscope. Stereo microscope magnification is as it would be in nature, not inverted like the magnification of compound microscopes. The long working distance and the correct image makes it possible to work under a stereo microscope.
Lomo Stereo microscopes are some of the best. The Lomo SF-50 is a perfect choice for a biology class or a watchmaker. It has the longest working distance of any stereo microscope and magnification from 2.5X to 46X. The Lomo SF-100 has a magnification of up to 200X with the optional 2X auxiliary objective. the Lomo SF-100BF comes with a ring light illuminator which is the best illumination available for a stereo microscope. The Lomo Sf-100 is ideal for production lines and quality control. Both microscopes are available in a trinocular version for attaching a microscope camera or an SLR camera.
Friday, April 02, 2010
Microbial Metabolism
Microbial metabolism is the way in which microbes obtain the energy and nutrients required to survive. Metabolism is the sum of all chemical reactions within a living organism including anabolic (biosynthetic) and catabolic (degradative) reactions. Catabolism is the breakdown of complex molecules into organic molecules and yields energy. This energy is stored in the bonds of adenosine triphosphate or ATP. Enzymes play an integral role in metabolism as they are responsible for lowering the activation energy of reactions or speeding up the rate at which they take place. Temperature, pH, substrate concentration, and inhibitors are some of the factors that affect enzymatic activity. Many of us enjoy the benefits of microbial metabolism yet we do not realize it. A few degrees can be the difference between making vinegar and wine, I prefer the latter. Yogurt (fermented milk) is a product of microbial metabolism and an excellent source of calcium. Bacteria are also responsible for the transfer of nitrogen from air to the soil and back to the air. Barnant Company, Marvel, and Parr Instrument supply products used in microbial metabolism research.