What does cytophotometry mean?
Cytophotometry is a laboratory technique in cell biology that combines microscopy with photometry — the precise measurement of light — to quantify the chemical contents of individual cells. By measuring how much light of a particular wavelength is absorbed by stained material within a cell or its nucleus, an instrument called a cytophotometer can determine the amount of a substance such as DNA or RNA present in that single cell. The best-known application is Feulgen cytophotometry, which uses a DNA-specific stain to measure nuclear DNA content; this method was historically important for studying the cell cycle, chromosome ploidy, and abnormalities in cancer cells. The technique flourished from roughly the 1950s onward but has since been largely displaced by faster automated approaches such as flow cytometry and digital image analysis. The term derives from Greek 'kytos' (cell) plus 'photometry', and remains part of the vocabulary of quantitative cytology and pathology.
nounA laboratory technique in cytology that uses a photometer or microspectrophotometer to measure the amount of light absorbed or transmitted by individual cells or cell components, allowing quantitative determination of substances such as DNA, RNA, or other chemicals within cells.
- The measurement of light absorption or transmission by individual cells or cellular components using a microscope-based photometric instrument, typically to quantify the amounts of specific substances (such as DNA after Feulgen staining) within those cells.
"Feulgen cytophotometry allowed the researchers to measure the DNA content of each nucleus with remarkable precision."
"Cytophotometry of Feulgen-stained nuclei revealed that tumour cells contained abnormal amounts of DNA."
"In the 1950s and 1960s, cytophotometry was the principal method available for quantifying nuclear DNA content in individual cells."
Rarely if ever pluralized; the word is used as an uncountable mass noun referring to the technique itself.
"Different cytophotometries were compared across laboratories."
Before modern flow cytometers existed, scientists measured the exact amount of DNA inside single nuclei by shining light through stained cells — one cell at a time.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cytophotometry
The word cytophotometry is formed from three combining elements: the Greek root 'kytos' meaning 'hollow vessel' or 'cell' (which also gives us cytology, cytoplasm, and cytokinesis), the element 'photo-' from Greek 'phos' meaning light, and '-metry' from Greek 'metron' meaning measure. The compound thus literally means 'the measurement of light in cells'. It arose in the early-to-mid twentieth century as quantitative cytochemistry developed, alongside related terms such as photometry and microspectrophotometry. Its cognates include all the -metry scientific terms derived from Greek metron, such as cytometry, densitometry, and spectrophotometry.
How cytophotometry is actually used
A technical term used almost exclusively in cytology, pathology, and cell biology. It is largely historical: from the mid-20th century it was the standard method for quantitative cytochemistry, but it has been substantially superseded by flow cytometry and image cytometry. The word is uncountable in ordinary use.
Easily confused with cytophotometry
Flow cytometry measures properties of cells suspended in a fluid stream as they pass through lasers, whereas cytophotometry measures light absorption in cells fixed on slides under a microscope.
Spectrophotometry measures the absorbance of solutions or bulk samples in a cuvette, while cytophotometry applies the same optical principle to measure chemical content within individual microscopic cells.