Abstract
The Feulgen reaction is examined by absorption photometric measurements at 565 nm with correction for varying background absorption at 485 nm. This correction is done to improve the accuracy of measuring.
Examinations of the accuracy of analysis for the Feulgen reaction and the direct microscopic cell counts show that the former is of the same order, when the cell count is made at a working factor of 17,000.
The standard deviations expressed in percentage of the reaction value are greater the lower the reaction is, whereas the absolute standard deviation is reduced.
It has been demonstrated that addition of a few (< 5) µg of DNA per ml milk can give Feulgen reaction. The coefficient of correlation between log added amount of DNA and log Feulgen reaction is 0.98.
The coefficient of correlation between log Feulgen reaction and log cell content depends on the accuracy at which both determinations are made. In a determination of cell content at a working factor of 550, and several determinations of the Feulgen reaction the coefficient of correlation (r) is found to be 0.98. A cell content determination at a working factor of 20,000 and a single determination of Feulgen reaction on each milk sample yields r = 0.83.
An examination of foremilk samples of the same cell content reveals on an average the highest reaction in mastitis-affected quarters which have been infected within the last 4 weeks. Quarters that have been infected for more than 4 weeks, on an average show the second highest reaction, whereas quarters of physiological cell number show the lowest reaction.
The DNA-content in most cases is found to be too high compared with the number of cells counted microscopically. The DNA-content in centrifugated cells corresponds to the one calculated theoretically. The surplus DNA-content can be demonstrated in the cell-free skim milk fraction, probably originating from destroyed cells.
The studies performed suggest that determination of the content of 2-deoxyribose in milk by means of the Feulgen reaction is a more correct measure of the cell content in the milk than is the microscopic cell count. Studies are being continued for illustration of these conditions.
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References
- Hauke H. Weitere Untersuchungen über die Spezifität der Feulgen Reaktion mit Milch und ihre Beziehungen zum Desoxyribonucleinsäuregehalt. (Further investigations on the specificity of the Feulgen reaction with milk and its relation to the desoxyribonucleic acid content) Milchwissenschaft. 1967;22:269–273. [Google Scholar]
- Hauke H, Lüttich V. Untersuchungen über die Eignung der Feulgen-Reaktion zur schnellen Bestimmung des Zellgehaltes der Milch. (Studies on the aptitude of Feulgen's reaction for the rapid determination of the cell content of milk) Milchwissenschaft. 1966;21:620–624. [Google Scholar]
- Klastrup O. Celletsellinger i leverandørmaelk. (Cell counts on can milk) Nord. Vet.-Med. 1960;12:621–638. [Google Scholar]
- de Langen H. Determination of DNA in milk. 1967. [Google Scholar]
- Menkin V. Biology of inflammation. Science. 1956;123:527–534. doi: 10.1126/science.123.3196.527. [DOI] [PubMed] [Google Scholar]
- Paape M J, Hafs H D, Tucker H A. Relationship of Feulgen DNA in milk and of Milk Quality Test to the number of milk somatic cells. J. Milk Food Technol. 1964;27:228–230. doi: 10.4315/0022-2747-27.8.228. [DOI] [Google Scholar]
- Paape M J, Hafs H D, Tucker H A. Comparison of methods for estimating milk somatic cells. J. Dairy Sci. 1965;48:191–196. doi: 10.3168/jds.S0022-0302(65)88193-0. [DOI] [PubMed] [Google Scholar]
- Paape M J, Tucker H A. Somatic cell content variation in fraction-collected milk. J. Dairy Sci. 1966;49:265–267. doi: 10.3168/jds.S0022-0302(66)87847-5. [DOI] [PubMed] [Google Scholar]
- Sandritter W D, Miller D, Gensecke O. Ultraviolettmikrospektrofotometrische Messungen des Nucleinsäuregehaltes von Spermien und diploiden Cellen. (Ultra-violet microspectro-photometric investigations of DNA-content of sperma and diploid cells) Acta histochem. (Jena) 1960;10:139–154. [Google Scholar]
- Schneider E, Jasper D E. The influence of the working factor and cell content on the precision of microscopic counts of milk somatic cells. J. Milk Food Technol. 1966;29:49–52. doi: 10.4315/0022-2747-29.2.49. [DOI] [Google Scholar]
- Whittlestone W G, de Langen H. The cell count of milk and rapid tests for mastitis. Proc. N. Z. Soc. Animal Production. 1965;25:137–151. [Google Scholar]
- Widstrom, G.: 1928, ref. from de Langen 1967.