Final answer:
For cell counts in hematology, a Petroff-Hausser counting chamber is used to count cells directly under a microscope. This system is effective for concentrated cultures, while dilute samples may require membrane filtration. Advanced analysis of specific cell types can be done with flow cytometry using fluorescently labeled antibodies.
Step-by-step explanation:
A dilution system commonly used for cell counts in hematology is a Petroff-Hausser counting chamber. This device is akin to the hemocytometer and is integral in the process known as direct microscopic cell count. A known volume of culture is placed on the chamber, beneath a coverslip situated at a precise height, making it possible to count cells in a defined volume and calculate cell concentration in the original sample. The Petroff-Hausser chamber's design etches squares into the central area where cells can be counted. This method has the advantages of being straightforward, quick, and cost-effective. However, it may be unsuitable for very dilute cultures due to insufficient cell numbers for accurate counting.
In cases of extremely dilute samples like drinking water, a membrane filtration technique may be employed, which involves filtering the sample and then growing colonies on a Petri dish. Other methods like the spread plate and pour plate methods involve serial dilutions and colony counts on agar plates. For living cell enumeration, vital dyes such as Trypan blue may be used to distinguish between live and dead cells in viability counts. Flow cytometry is another advanced technique allowing for the analysis of specific cell types using fluorescently labeled antibodies, enabling rapid and detailed cell counts and analysis in complex samples such as blood.