Cell-counting instruments

Figure 14. Water column analysis involving pump profiling system. In the system pictured, conductivity (an index of salinity) and temperature are profiled. The fluorometer measures ij vivo fluorescence from chlorophyll (from all phytoplankton) and discrete samples are taken for cell counts and nutrient chemistry. Photodetectors can be employed for the measurement of bioluminescence. Light measurements range from Secchi disc readings to more sophisticated transmissometry and spectral radiometry instruments.

This review is written for the clinical chemist who wishes to understand the principles of the main classes of instruments, their relative merits and applications, and the types likely to be important in the future. Equipment used for data processing, in vivo analysis, cell counting and morphology is excluded. Some instruments described in standard textbooks [e.g., (S15, W18)] have been omitted either because they have not developed significantly in recent years (e.g., nephelometers, refractometers) or because they have found little application in clinical chemistry (e.g., thermal analyzers). 

The use of an infrared sensor (Aquasant Messtechnik AG, Bubendorf, Switzerland) may be a solution for many apphcations, particularly in combination with a control of viability (Merten et al, 1987). Other alternatives are sensors measuring conductance/capacitance (ABER Instruments, Cefnllan, Aberystwyth, UK) and software sensors (Pelletier et al, 1994). For further reading see De Gouys et al (1996). A recently pubhshed method based on real-time imaging opens up new possibihties by real cell counting (Ozturk et al, 1997). 

Fluorescence Decay Measurements. The single photon counting instrument will be described in detail elsewhere. All measurements were made on whole cells using 870 nm excitation and 900 nm emission detection. 

Automated Cell Counter Instrument that uses electric impedance or optical light scatter to rapidly count blood cells. 

Automated Cell-Coimting Instruments. Until the mid-1950 s, cell counts were performed manually using a diluted fluid and a hemocytometer, and blood smears were viewed microscopically. Modern automated instruments can perform a complete blood count (CBC), which includes red blood cells, white blood cells, platelets, hemoglobin, hematocrit, and a five-part differential. This testing accounts for... 

To eliminate the need for recalibration during a measurement and to obtain additional information, the Royco instrument was supplemented with a Nuclear Data ND-60 Multichannel Analyser (MCA). The amplified signal of the Royco 225 (which is proportional to the cimount of light scattered from each particle) was connected to the input of the MCA which cem count and classify pulsed input signals into as many as 2048 channels and display the results on a cathode ray tube (CRT). This number of cells is of course much more than required to determine the PSD. The data were therefore grouped into eleven cells whose limits were consistent with those used earlier (5), emd the counts in these cells were then printed on a Texas Instruments 743 KSR Data Terminal interfaced with the MCA. 

Xanthamonas campestris strain engineered to bioluminesce (Shaw et al., 1992). The strain was applied to cabbage plants and surrounding soils in a limited field study conducted in 1990. The fate of the organisms was monitored by both CCD-microscopy and plate counts, Recombinant cells were found for up to six weeks, with the CCD and plate counts giving quantitatively similar results. Bioluminescence in this case was no more sensitive than plate counts, and required a precision instrument,... 

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