MicroscopesBlog: Expert's reviews, news, notes on Microscopes, Centrifuges, Lab Coats, Pipettes, Lab Safety, & more Lab Products!

Microscopy is as much art as it is science. The microscopic world of "brass and glass" as it is sometimes referred to, is almost always a prisoner of the source of illumination. Sunlight, candlelight, incandescent light, fluorescent light, high pressure arc lamps and most recently LED illumination have all been employed to supply both compound and stereoscopic microscopes with the illuminating energy that brings the images of the samples we want to investigate to our eyes. In some ways, the science is the easy part. You focus a lens system on the desired sample and the laws of physics render a magnified image for eyes to study and appreciate. The art involves choosing the source of illumination to best suit your needs. Sunlight is usually regarded as the best source to observe specimens with the least amount of bias as to how their natural colors are rendered;however, sunlight is not always available. Incandescent tungsten sources tend to amplify yellows and fluorescent sources seem to favor the blue/green portion of the visible spectrum. Each source will exhibit some degree of color bias. In addition, there is the problem of heat, especially as it affects living samples on a slide or in a Petri dish or other sample container. In modern microscopy the tungsten/halogen light source is the current common denominator for normal brightfield viewing and is a very good compromise for good color balance and minimizing the effects of heat since the actual illuminating components are somewhat removed from the specimen itself. Many current microscopes also offer LED light sources which boast extremely long bulb life, good color balance and virtually eliminate any heat issues. LED sources can also be powered by battery packs where AC current is not readily available or may be undesirable. If you are examining a geological sample or sampling the water in your aquarium or local fishing pond, investigate your options as to available illumination cources for your microscope.

Prokaryotic cells are defined as cells that lack a membrane bound nucleus. There are two basic types: domain Bacteria and domain Archaea. Prokaryotics average 1.1-1.5 um in width and 2.0-6.0 in length. Because they are such simple organisms there are only three main components of structure: cell envelope, cytoplasm and appendages. In addition, there are four basic shapes associated with these cells: bacillus (rod-shaped bacterium); coccus (spiral-shaped bacterium); spirilla (long rods twisted into rigid spirals); and spirochetes (long rods twisted into flexible spirals). Prokaryotics although simple organisms, are very important to human body functions. Bacteria, for example, is necessary and helpful for healthy digestion within the body. Bacteria is also used in the production of cheese and milk consumed by humans. There are also bacteria that are harmful to humans such as Streptococcus, a coccus shaped bacterium that can cause strep throat. Another example would be Mycobacterium Tuberculosis a bacillus shaped bacteria that can cause Tuberculosis. However, since bacteria are there own organism and not parasites, like viruses, they can be killed/treated with antibiotics. Bacteria can be seen and observed through a compound microscope. *Picture from http://www.positive-healthy-living.com/good-bacteria.html

Fluorescence microscopy is a valuable tool in the study of cells and their biological activity. Immunofluorescence adds to the utility of this study by the specificity of the technique. Antibodies to specific molecules in the cell are conjugated with fluorphores. When viewed under a fluorescence microscope with the appropriate filters only the specific molecule of interest is observed. Two antibodies may be necessary: The primary antibody is specific to the molecule of interest in the cell and may be from mouse or goat or chicken... The secondary antibody is conjugated to a fluorophore and is anti-mouse or anti-goat or anti-chicken.... This technique is called immunofluorescence. One application of immunofluorescence is the identification and separation of embryonic and pluripotent(undifferentiated) stem cells. Image from www.biologie.uni-hamburg.de.

Cytology is the study of cells. The study of cells truly began to blossom in the 1830's with the work of German biologist Matthais Schleiden, a botanist, and Theodor Schwann, a zoologist. Their contribution: all organisms are composed of cells. And with the the addition of a German physician, Rudolph Virchow discovery that all cells come from pre-existing cells, cytology was spawn. Cytology continued to develop through the advancement of microscopes. Microscopes are needed to view cells, whose sizes measure from one micrometer to one millimeter. Structurally, all cells are composed of a cell membrane, cytoplasm, and a nucleus. However, as the organism gains complexity so does the cell's components. There are several different microscopes that are used in this study. Please see the table below for a few examples of microscopes you can use to examine cells.

Type of Microscope	Basic Information
Compound Light	· Focused by glass lenses · Light is passed through sample · Caps at 1000x magnification o 500 times better than the human eye · Resolution is 0.2µm
Transmission Electron (T.E.M.)	· Focused by magnetic lenses · Electrons pass through sample · Imaged on fluorescent screen · Caps at 100,000x magnification o 100, 000 times better than the human eye · Resolution is 0.00002µm
Scanning Electron (S.E.M.)	· Focused by magnetic lenses · Sample sprayed with a thin coat of metal · Imaged on fluorescent screen

Laboratory notebooks are designed in accordance with GLP. Lab notebooks in the research laboratory must be auditable and are considered a legal document. Laboratory notebook paper must be acid free for long term storage. Lab notes must be able to be traced back to original data; therefore lab notebooks have unique serial numbers, numbered pages, and the pages are not removable. Many laboratories are leaving written lab notebooks behind and are using an electronic laboratory notebook, ELN. ELNs are software programs designed to be searchable and traceable. Many laboratory instruments are now designed to be used with ELN software. ELN software must be designed to maintain the integrity of original data. Safety protocols must be included to protect against manipulation or falsification of original data.

A molecule composed of one or more polypeptides is a protein. There have been over 100,000 proteins identified and as much as 50% of the dry weight of cells is composed of them. Therefore, the study and comprehension of proteins are invaluable to biology, the study of life and living organisms. Proteins have various functions within animals; which includes, metabolic, supportive, transport, defense, regulatory and mobility functions. In fact, proteins are so imperative to living organisms that tissue and cells can sometimes be identified by the type of protein they contain or produce. A good example of this is red blood cells. Hemoglobin is a type of protein specific to red blood cells; whose major function is to transport oxygen throughout the organism. Other functions and examples can be seen in the table below:

Metabolic Functions	Enzyme: catalyzes chemical reactions in cells
Supportive Functions	Keratin/Chitin: Provides structural function. Keratin makes up hair/nails in humans and Chitin makes up the exoskeleton of crabs, etc.
Transport Functions	Hemoglobin: Transport oxygen within red blood cells from the lungs of a human, for example, throughout the rest of the body.
Defense Functions	Antibodies: Prevents antigens from destroying and upsetting cells regulatory processes.
Regulatory Functions	Hormones: Messengers that influence the metabolism of cells
Mobility Functions	Myosin: Causes muscles to contract by allowing parts of cells to move

Ever wonder what the hazard symbols in the diamond placards on the sides of tank trucks are telling us? The signs are notifying us of the possible chemical hazards posed by the contents of the truck. The blue portion of the symbol represents health hazards. The yellow portion represents reactivity such as a tendency to explode. The red is flammability. The white portion is for special hazards such as dangerous reactivity with water. The higher the numbers the more dangerous the chemical. Use of this hazard symbol has been carried into the lab. It appears on wash bottles and other chemical containers.

A thermometer by definition is an instrument used to measure temperature by expanding and contracting a liquid within the glass filled tube to indicate temperature and/or temperature changes. Traditionally, the liquid used to measure these changes was mercury. However, due to the potential health risk associated with mercury if cracked or broken, there has been a move by some to switch to an alternative liquid.What is that alternative? Alcohol. Spirit-filled or alcohol thermometers is a good alternative to mercury because it is less toxic and evaporates quickly if damage occurs. Spirit-filled thermometers can me made of various types of alcohol depending upon the manufacturer and temperature range. Alcohol thermometers have a maximum temperature range of -115°C to 785°C, which is the freezing and boiling point of alcohol respectively. Here is a chart to display max and min temperatures values associated with each liquid.

*Filling liquid	Abbreviation	Lower limit (° C)	Upper limit (° C)
Mercury	Hg	-38.5	+800
Mercury-thallium alloy	Hg/TI	-58	approx.+150
Gallium alloy	Ga	-0	approx. +1.200
Technical pentane	C5H12	-200	approx. +35
Ethanol	C2H6O	-110	approx. +100
Pentanol	C5H12O	-115	approx. +135
Toluene	C7H8	-90	approx. +100
Creosote		approx. -40	approx. +210
Petroleum	P	approx. -45	approx. +160
i-amyl benzoate	C12H16O2	approx. -40	approx. +220

*From http://www.instrumentationservices.net If you are looking for a safe alternative to mercury thermometers and are not interested in digital, I would suggest investigating and investing in a spirit filled thermometer.