A Modified MTS Proliferation Assay for Suspended Cells to Avoid the Interference by Hydralazine and ß-Mercaptoethanol.

The 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay is one of the most commonly used tests of cell proliferation. Hydralazine has been reported to interfere with the performance of the MTS assay when used on adherent cells. This study aimed to investigate whether hydralazine interferes with the performance of the MTS assay on suspended cells. THP-1 (a monocytic leukemia cell line) cells were cultured in the presence or absence of hydralazine (0, 10, 50, 100, and 500 µM) for 2 or 24 h. Cell numbers were analyzed using the MTS, trypan blue exclusion, or microscopic assays. A modified version of the standard MTS assay was established by centrifuging the cells and replacing the test medium with fresh culture medium immediately before the addition of the MTS reagent. Culture of THP-1 cells with hydralazine at concentrations of 50, 100, and 500 µM for 2 h increased absorbance (p < 0.001) in the standard MTS assay, whereas both the trypan blue exclusion assay and microscopy suggested no change in cell numbers. Culture of THP-1 cells with 100 and 500 µm hydralazine for 24 h increased absorbance (p < 0.05) in the standard MTS assay; however, trypan blue exclusion and microscopy suggested a decrease in cell numbers. In a cell-free system, hydralazine (100 and 500 µM) increased absorbance in a time- and concentration-dependent manner. The modified MTS assay produced results consistent with trypan blue exclusion and microscopy using THP-1 cells. In addition, the modified MTS assay produced reliable results when K562 and Jurkat cells were incubated with hydralazine or ß-mercaptoethanol (ßME). In conclusion, a simple modification of the standard MTS assay overcame the interference of hydralazine and ßME when assessing suspended cells.

The concentration of ethanol affects its penetration rate in bovine cardiac and hepatic tissues.

INTRODUCTION: Ethanol is a commonly used fixative. Fixation of the inner layers of the tissue depends on the ability of the fixative to diffuse into the tissue. It is unknown whether the concentration of ethanol affects its penetration into tissues. This study aimed to compare the penetration rates of 50% and 100% ethanol into bovine heart and liver tissues. MATERIALS AND METHODS: The penetration distance and tissue shrinkage or expansion were measured by analysing the digital images of the heart and liver tissues before and after immersion in ethanol at 20°C for 2, 6, 24 or 30 hours. The penetration coefficients were calculated as the slope of the regression line using the linear regres-sion function between the penetration distance and square root of fixation time. Differences in tissue shrinkage or expansion and penetration distance at various time points between the two concentrations of ethanol were analysed using a mixed design ANOVA followed by Bonferroni's post-hoc test. RESULTS: The penetration distance of 100% ethanol was significantly greater in both heart and liver tissues com-pared with that of 50% ethanol (n = 4, p < 0.05 for both). 100% ethanol shrank immersed liver tissue signifi-cantly more than 50% ethanol (p = 0.002), but the shrinkage of the heart tissue caused by two concentrations of ethanol did not significantly differ (p = 0.054). The greater penetration distance of 100% over 50% ethanol remained unchanged after normalising the penetration distance to the individual tissue's shrinkage (n = 4, p < 0.001). The mean penetration coefficient of 100% ethanol was significantly greater than 50% ethanol in the heart tissue (0.906 vs. 0.442, p = 0.003) and in the liver tissue (0.988 vs. 0.622, p = 0.028). CONCLUSIONS: It was proven that in two types of tissue that substantially differ in histological structures, 100% ethanol penetrated tissue significantly faster than 50% ethanol.

Whole genome survey of copy number variation in the spontaneously hypertensive rat: relationship to quantitative trait loci, gene expression, and blood pressure.

Copy number variation has emerged recently as an important genetic mechanism leading to phenotypic heterogeneity. The aim of our study was to determine whether copy number variants (CNVs) exist between the spontaneously hypertensive rat (SHR) and its control strain, the Wistar-Kyoto rat, whether these map to quantitative trait loci in the rat and whether CNVs associate with gene expression or blood pressure differences between the 2 strains. We performed a comparative genomic hybridization assay between SHR and Wistar-Kyoto strains using a whole-genome array. In total, 16 CNVs were identified and validated (6 because of a relative loss of copy number in the SHR and 10 because of a relative gain). CNVs were present on rat autosomes 1, 3, 4, 6, 7, 10, 14, and 17 and varied in size from 10.0 kb to 1.6 Mb. Most of these CNVs mapped to chromosomal regions within previously identified quantitative trait loci, including those for blood pressure in the SHR. Transcriptomic experiments confirmed differences in the renal expression of several genes (including Ms4a6a, Ndrg3, Egln1, Cd36, Sema3a, Ugt2b, and Idi21) located in some of the CNVs between SHR and Wistar-Kyoto rats. In F(2) animals derived from an SHRxWistar-Kyoto cross, we also found a significant increase in blood pressure associated with an increase in copy number in the Egln1 gene. Our findings suggest that CNVs may play a role in the susceptibility to hypertension and related traits in the SHR.