Author: Site Editor Publish Time: 2022-12-14 Origin: Site
Cytometry is any of various methods used for cell counting or similar quantification in the life sciences, including medical diagnosis and therapy.It is an important subset of cytometry and has applications in both research and clinical practice.For example, a complete blood count can help doctors determine why a person is feeling unwell and what to do to help.Cell counts in liquid media (such as blood, plasma, lymph, or laboratory washes) are usually expressed as the number of cells per unit volume, thus expressing a concentration (for example, 5,000 cells per milliliter).
Many procedures in biology and medicine require counting cells.Concentrations can be adjusted by counting cells in a known small volume.Examples where cell counts are required include:In medicine, the concentration of various blood cells, such as red and white blood cells,can provide important information about a person's health (see: complete blood count).In cell therapy, the dose of cells given to the patient is controlled.Likewise, the concentration of bacteria,viruses and other pathogens in blood or other bodily fluids can reveal information about the progression of an infectious disease and about how successfully the immune system handles the infection.Many experiments in molecular biology require knowledge of cell concentrations in order to adjust the amounts of reagents and chemicals to be applied in the experiment accordingly.Studies that examine the growth rate of microorganisms (in other words, how quickly they divide to produce new cells) require cell counts.Calculate the ratio of dead cells to live cells as a measure of cell viability, eg cells exposed to toxicants.
Manual Cell Counting
There are several methods for cell counting. Some are primitive and require no special equipment, so they can be done in any biological laboratory, while others rely on sophisticated electronics.
Counting chambers are microscope slides designed for cell counting.Cytometers and Sedgewick Rafter counting chambers are two types of counting chambers.There are two grid-shaped chambers in the middle of the blood cell counter, which are covered with special glass slides when counting.A drop of cell culture is placed in the space between the chamber and the cover glass, filling it by capillary action.Looking at samples under a microscope, researchers use a grid to manually count the number of cells in a specific area of known size.The separation distance between the chamber and the lid is predefined so that the volume of the counted culture can be calculated and used to calculate the cell concentration.Cell viability can also be determined if a reactive dye is added to the liquid.Their advantage is that they are cheap and fast; this makes them the preferred counting method in rapid biological experiments where it is only necessary to determine whether the cell culture is growing as expected.Typically the cultures examined need to be diluted, otherwise the high density of cells will not be countable.The need for dilution is a disadvantage, as each dilution increases the inaccuracy of the measurement.
Plating and CFU Counting
To quantify the number of cells in a culture, cells can be simply plated on Petri dishes containing growth medium.If the cells are efficiently distributed on the plate, it can usually be assumed that each cell will produce a single colony or colony forming units (CFU).Colonies can then be counted and based on the known culture volume spread across the plate, the cell concentration can be calculated.As with the counting chamber, the culture usually needs to be heavily diluted before inoculation; otherwise, instead of counting individual colonies, a so-called "lawn" will form: thousands of colonies overlapping each other. In addition, plating is the slowest of all methods: most microorganisms require at least 12 hours to form visible colonies.While this method can be time-consuming, it allows for an accurate estimate of the number of viable cells (since only they are able to grow and form visible colonies).It is therefore widely used in experiments aimed at quantifying the number of cells resistant to drugs or other external conditions.Additionally, the use of a colony counter can greatly facilitate colony counts on agar plates.