Electronic cell sorting

This is considered in more detail in 10.7.5. It is a method which involves a modified electronic cell counter, i.e. a Coulter counter linked to a pulse height analyser and an electronic cell sorter. It is capable of separating cells at a rate of about 50,000/min into a 

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The second step required in the application of avidin-biotin technology is to prepare an appropriate avidin-associated probe or probes for the desired application (for general reviews, see refs. 1 and 2). For example, a fluorescent form of avidin can be used for fluorescence microscopy, fluorescence-activated cell sorting, and in some cases, for immunoassay. Likewise, an avidin-enzyme conjugate can be used for immunoblotdng, immunoassay, light microscopy, and in some cases, electron microscopy. An immobilized form of avidin can be used for isoladon purposes (see Note 1). 

Abbreviations APCI Atmospheric Pressure Chemical Ionization DAG Diacyl-glycerols DE Delayed Extraction DHB 2,5-Dihydroxybenzoic Acid El Electron Impact ESI Electrospray Ionisation FACS Fluorescence-activated cell sorting GC Gas Chromatography HDL High Density Lipoprotein HPLC High-Performance Liquid Chromatography IR Infrared LDL Low Density Lipoprotein LOD Level of Detection LOQ Level of Quantification LPC Lyso-Phosphatidylcholine LPL Lyso-Phospholipid MALDI Matrix-... 

The choice of label will depend on the application envisaged. Enzymes are widely applicable they are used in assays, such as ELISAs, and for detection of antigen blotted or dotted on membranes or embedded in tissue sections. Enzyme labels have also be used for the location of antigen in electron microscope sections but gold labelled antibodies (Chapter 11) are now extensively employed for this purpose. Antibodies labelled with a fluorescent molecule are used in assays and for the detection of antigens in tissue sections and also for flow cytometiy and fluorescence-activated cell sorting. 

It was also observed in earlier studies that mitochondria not only accumulate Ca2+ as an alternative to phosphorylation of ADP (Ca2+ uptake uncouples phosphorylation from electron transport), but could also accumulate much larger amounts of Ca2+ if phosphate was also taken up, resulting in precipitation of Ca2+ within the matrix as insoluble hydroxyapatite, visible as electron-dense granules by EM. An unusual feature of these hydroxyapatite deposits is that they fail to become crystalline and remain amorphous even over protracted periods of time. Their presence in mitochondria in a number of disease conditions underlines the role for mitochondria as a sort of safety device, which can enable the cell to survive, if only for a limited period of time, situations of cytoplasmic Ca2+ overload. 

Consider the battery in Fig. 7.18. The sodium beta alumina barrier allows sodium ions formed at the anode to Row across to the sulfur compartment, where, together with the reduction products of the sulfur, U forms a solution of sodium trisulfide in the sulfur. The latter is held at 300 CC to keep it molten. The sodium beta alumina also acts like an electronic insulator to prevent short circuits, and it is inert toward both sodium and sulfur. The reaction is reversible. At the present state of development, when compared with lead storage cells, batteries of this sort develop twice the power on a volume basis or four times the power on a weight basis. 

Fig. 9.5. Efficiency and speed of sorting are affected by the flow rate of cells. At high flow rates, more desired cells are lost, but the speed of collecting these desired cells increases until the loss of efficiency becomes greater than the increase in speed. Highspeed sorting, with more drops per second, increases the efficiency and decreases the time required to obtain the desired number of cells. The model from which these graphs were generated was derived by Robert Hoffman for these data, a three-drop sort envelope was used, 1% of the cells were sorted, and the electronic dead time was set at 6 ps. If one drop is sorted with each sort decision (instead of three), the theoretical efficiency of the sorting improves considerably (as does the rate of collecting the sorted cells).

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