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Monday, August 30, 2010
Measuring Microscope
Measuring objects with a microscope is known as micrometry. Most good microscopes can be used as a measurement microscope or inspection microscope. The necessary accessories are an eyepiece reticle (reticule) and a stage micrometer. Eyepiece reticles are available from the manufacturer of your microscope. Some eyepieces are designed to allow a reticle to be 
added by the user. Some reticles must me installed by the manufacturer. Reticles can be a line scale, a grid, a series of concentric circles, or some other scale depending on the application. Reticles must be calibrated with a stage micrometer. Stage micrometers are available in English units (inches) or metric (millimeters).
added by the user. Some reticles must me installed by the manufacturer. Reticles can be a line scale, a grid, a series of concentric circles, or some other scale depending on the application. Reticles must be calibrated with a stage micrometer. Stage micrometers are available in English units (inches) or metric (millimeters).
First determine the diopter adjustment which brings the reticle in sharp focus for your eyes and write this down. This will be your diopter adjustment for future measurements. Place the stage micrometer on the stage and, using the appropriate magnification for your application, line up one of the 
long bars of the micrometer with the zero on the reticle. Look for another place where a reticle line exactly lines up with a micrometer line. The longest point at which this happens will make the factor more accurate. Divide the micrometer distance by reticle line number. This will be the number of microns (thousandths of an inch for English) for each reticle line at this magnification. Now the stage micrometer can be removed and your sample can be placed under the objective and focused. You know know the distance between each reticle line, the factor, and you may use this to measure your specimen. A more thorough explanation of this calibration process can be found on MicroscopyU
long bars of the micrometer with the zero on the reticle. Look for another place where a reticle line exactly lines up with a micrometer line. The longest point at which this happens will make the factor more accurate. Divide the micrometer distance by reticle line number. This will be the number of microns (thousandths of an inch for English) for each reticle line at this magnification. Now the stage micrometer can be removed and your sample can be placed under the objective and focused. You know know the distance between each reticle line, the factor, and you may use this to measure your specimen. A more thorough explanation of this calibration process can be found on MicroscopyUPosted by Robin P at 8:00 AM Read Article 0 comments 
Friday, August 27, 2010
Plant Viruses and Viroids
Plant viruses are very similar in morphology to animal viruses and they have similar types of nucleic acid. Some plant viruses actually multiply inside insect cells. Viruses can cause diseases to may different economically important crops. Beans can suffer from the bean mosaic virus, corn and sugarcane are affected by the wound tumor virus, and potates are succeptible to the potato yellow dwarf virus. Plant viruses can cause symptoms such as color change, deformed growth, wilting, and stunted growth however some plants do not suffer from symptoms and are merely carriers of the infection. Plants are able to protect themselves from viruses due to their impermeable cell wall. Viruses typically enter through wounds or they enter by plant parasites such as fungi, nematodes, or insects. Some plant diseases are casued by viroids, short pieces of naked DNA, only 300-400 nucleotides with no protein coat. Nucleotides are paired so the molecule has a closed, folded, three-dimensional structure that prevents attack from enzymes.
Wednesday, August 25, 2010
Glassware to the Extreme!
Looking for a type of glassware to withstand even the coldest of cold or hottest or hot? Try Borosilicate or Pyrex glassware. Glassware composed of at least 5% boric oxide by definition is considered Borosilicate glass. In addition to the glass being able to withstand extreme hot or cold, it is also chemical corrosion resistant and able to withhold unstable chemicals.
Another name for Borosilicate glass is Pyrex. Pyrex was an exclusive name given to Borosilicate glass created by Corning. However, since its inception, Pyrex is now considered a genericized trademark.
This extreme glass is used in everything from glass cookware to laboratory glassware (flask, slides, bottles, etc). Although, like any other glass, Borosilicate glass is not unbreakable when dropped or quickly removed from an extreme temperature to another, it is more likely to crack than shatter. So, If you are looking for a type of glass to go the distance, consider Borosilicate glass! Monday, August 23, 2010
Coverglass
A coverglass or a coverslip is used to cover a specimen on a glass slide for examination under the microscope. The coverglass flattens solid objects and creates a thin even film for wet mounts. Coverslips can be sealed to the slide using sealants like Sakura Tissue Tek OCT Compound. Microscope cover slips are standardized very thin optically flat glass. They can also be made of plastic and quartz. They are sized to fit within the dimensions for a typical glass microscope slide (25 x 75mm) typically 20 x 20mm. Cover glasses are standardized by thickness:
no. 0: 0.085 - 0.13mm
no. 1: 0.13 - 0.16mm
no. 1.5(1 1/2): 0.16 - 0.19mm
no. 2: 0.19 - 0.23mm
no. 3: 0.25 - 0.35mm
no. 4: 0.43 - 0.64mm
The thickness of the cover slip is very important. Most compound objectives are designed to work with the no. 1.5 cover glass (0.17mm). Highly corrected objectives are equipped with a correction collar to allow adjustment for changes is coverslip thickness..
Friday, August 20, 2010
Antimycobacterial Antibiotics
The cell wall of the bacterial genus Mycobacterium differs from the cell wall of other species due to the presence of mycolic acids. This genus includes dangerous pathogens such as those that cause leprosy and tuberculosis. Due to the difference in cell wall structure a different class of antibiotics, known as antimycobacterial antibiotics is required to fight infections. Isoniazid is an antimicrobial drug against Mycobacterium tuberculosis. This drug prevents the synthesis of mycolic acids. When isoniazid is used to treat tuberculosis it is usually administered simultaneously with other drug such as rifampin (also known as rifampicin) or ethambutol. This minimizes the development of drug resistance. Because the tubercle bacillus is normally found within macrophages or walled off in tissue, any antitubercular drug must be able to penetrate into these sites. Ethambutol is effective only against mycobacteria as it inhibits the incorporation of mycolic acid into the cell wall. This drug is used typically as a secondary drug to avoid resistance problems.
Wednesday, August 18, 2010
Meltdown
Meltdown! After months and years of trial after trial, data upon data, and specimen after specimen… you go to your lab to check on your prize possessions… and the freezer is warm! Your heart drops. Your stomach churns. Panic sets in… years of data lost… forever!
You must be wondering why those prize possessions were not linked to an alarm. Although an alarm is not a major laboratory purchase, it is critical to long term storage.
Alarm technology has increased from just lights, bells and whistles when the temperature drops below your threshold to automatic phone dial as a secondary line of defense in notification. Some alarms even have the capability of reading temperatures from multiple freezers and auto-dialing multiple numbers.
So instead of John Doe walking into his lab and having a massive panic attack, he could have been notified when the temperature was low and the samples were still salvageable instead of destroyed!
Monday, August 16, 2010
Plastic Droppers
Bulb pipets are very useful for transfer of fluids such as samples, reagents, and stains. Also known as disposable transfer pipettes these tools are indispensable. The pipettes are 
made from polyethylene and are pliable but tough. They are available sterile and non-sterile. Manufacturers such as Samco (Thermos Scientific) and VWR offer many different draw volumes and tip design. Some of the options are fine tip, extra fine tip, long stem, extra long stem, large bulb, exact volume, and pipets specially designed for blood bank applications. There is a large choice in transfer pipets. Perhaps the procedure you're using could be improved with the right transfer pipette.
Friday, August 13, 2010
TB-detecting microscope
Andrew Miller, a bright student from Rice University, may have created a TB-detecting microscope that could save researchers thousands of dollars. Typically a confocal microscope, costing close to $40,000 is used to view samples from infected patients however Mr. Miller's microscope only costs $240. People who are infected with tuberculosis are typically in remote locations which increases the time it takes to perform the test and get results. With Mr. Miller's microscope researchers will be able to perform this test in the field and provide results immediately. Mr. Miller wanted to create a microscope that could be used in developing countries where laboratories and/or electricty are not readily available. In a recent clinical trial 63 TB smears were tested with a fluorescence microscope and Mr. Miller's microscope. The two microscopes showed similar results in 98.4% of the tests. Once approved, this microscope will make TB testing much more efficient.
Thursday, August 12, 2010
Types of Cuvettes
UV Vis Cuvettes are available as glass, quartz, or disposable plastic cuvettes. Optical quality glass and quartz are used to make 
spectrophotometer cuvettes (aka spectrophotometer cells). For UV spectrophotometers quartz cuvettes are the standard. All of these materials can be made into semi-micro and micro cuvettes for small sample sizes. Be careful when choosing micro cuvettes as the beam height of your spectrophotometer must not be lower than the beam height specified by the cuvette manufacturer. Long path length cuvettes, rectangular and cylindrical, are available for very dilute samples. For fluorometers cuvettes must be optically clear on all four sides. 
Disposable plastic cuvettes are available for visible, UV, and fluorometry. These plastic cuvettes are valuable for high throughput when absorption tolerances are not critical. Brandtech, VWR, Unico, and Scientific Cells are a few manufacturers of Cuvettes
spectrophotometer cuvettes (aka spectrophotometer cells). For UV spectrophotometers quartz cuvettes are the standard. All of these materials can be made into semi-micro and micro cuvettes for small sample sizes. Be careful when choosing micro cuvettes as the beam height of your spectrophotometer must not be lower than the beam height specified by the cuvette manufacturer. Long path length cuvettes, rectangular and cylindrical, are available for very dilute samples. For fluorometers cuvettes must be optically clear on all four sides. 
Disposable plastic cuvettes are available for visible, UV, and fluorometry. These plastic cuvettes are valuable for high throughput when absorption tolerances are not critical. Brandtech, VWR, Unico, and Scientific Cells are a few manufacturers of CuvettesWednesday, August 11, 2010
The C-Diff Problem
Clostridium difficile (or C. Diff) are bacteria that cause diarrhea and intestinal diseases. These bacteria are becoming a rising problem in today’s hospital because of its inability to be killed by most cleaners and alcohol-based sanitizers, as well as being most antibiotic resistant.
The elderly, sick, and those using antibiotics for prolong periods are highly susceptible to this fecal-spore spread bacterium. Side effects of C. Diff can range from flu-like symptoms (fever, loss of appetite, nausea, and diarrhea) to Colitis (inflammation of the large intestine).
Because C. Diff can not be killed with traditional cleaners hospitals are scrambling for a disinfectant solution. The CDC is recommending the use of a hypochlorite-based disinfectant.
The first and only company that is EPA registered for disinfection specifically against C. Diff spores is Clorox®, Ultra Clorox Germicidal Bleach. In addition, Dispatch ® Hospital Cleaner Disinfectant with Bleach is an EPA registered hypochlorite-based disinfectant but is not EPA registered for that specific bacterium. Caltech is currently in review by the CDC to become EPA registered, but boast that in addition to being hypochlorite-based, they have as much or more bleach ppm (1 in 10) then most disinfectants. Hopefully with new disinfectant technology the C. Diff rise will become just an occasional occurrence.
Monday, August 09, 2010
Membrane Reverse Osmosis
Osmosis is the process by which our cells absorb water, salts, nutrients, and shed waste products. A semi-permeable membrane surrounds the cell allowing certain molecules to pass but not others. The tendency for molecules to
be in equilibrium on both sides of the membrane is the pressure which causes molecules to pass through the membrane. Osmotic pressure is the pressure across the membrane when the molecules are not in equilibrium. Reverse osmosis membranes only allow water to pass. Pressure applied to the side of the membrane with the untreated water forces only the water to pass across the membrane, leaving the impurities behind. Reverse osmosis water treatment is extremely valuable. Large scale reverse osmosis systems provide purified water for troops and NGOs in remote areas.
be in equilibrium on both sides of the membrane is the pressure which causes molecules to pass through the membrane. Osmotic pressure is the pressure across the membrane when the molecules are not in equilibrium. Reverse osmosis membranes only allow water to pass. Pressure applied to the side of the membrane with the untreated water forces only the water to pass across the membrane, leaving the impurities behind. Reverse osmosis water treatment is extremely valuable. Large scale reverse osmosis systems provide purified water for troops and NGOs in remote areas.
Image from inspectapedia.com
Friday, August 06, 2010
Streptococcus mutans
Ever wonder why your dentist told you that candy causes cavities? Candy provides a species of bacteria, Streptococcus mutans, with sugar. S. mutans then converts this sugar to lactic acid which eats away at the enamel of the tooth. Teeh do not shed surface cells which allows the accumulation of microorganisms. The accumulation of microorganisms on teeth are referrerd to as dental plague, a type of biofilm. There are over 700 species of bacteria in the oral cavity. Most of the species in the oral cavity can't be isolated using conventional laboratory techniques. Streptococcus mutans is capable of metabolizing a wider range of carbohydrates making it harmful to tooth enamel. Within minutes a clean tooth will become coated with a pellicle or thin layer of proteins from saliva. Within a couple of hours, cariogenic bacteria become established on this pellicle and begin to produce a gummy polysaccharide of glucose molecules called dextran. Our body does have natural defenses against bacteria. Our saliva contains an antimicrobial substance known as lysozyme. This doesn't give you an excuse not to brush your teeth!
Monday, August 02, 2010
Laboratory Water Quality
Laboratory water quality standards are established by several groups including, the National Committee for Clinical laboratory Standards (NCCLS) (now the Clinical Laboratory Standards Institute - CLSI). The NCCLS uses Type I, II and II where Type I water is the Higher purity. For the American Society for Testing and Materials (ASTM) Type I ASTM water is the higher purity. The American Chemical Society (ACS), US. Pharmacopoeia (USP) also have water quality standards.
Type I water has High resistivity, low total organic carbon (TOC) and is filtered at least to 0.45 micron for particulates and bacteria. HPLC, electrophoresis, flame emission spectrometry, trace metal analysis, and standard solution preparation are some of the applications requiring Type I water.
Type II water is used in test methods where the presence of bacteria can be tolerated. Type II water is suitable for things like reagent preparation, stains and dyes for histology, and microbiology systems which are to be sterilized.
Type III water is used for general washing and feed water for systems which produce the higher grades of water.
Special purpose water is Type I water which is further purified with a UV chamber to reduce TOC even lower and an ultra filtration cartridge for removal of pathogens.
Please see the Clinical Laboratory Standards Institute for a more exact description of these standards.