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Dual DNA staining assessment of bovine sperm viability using SYBR-14 and propidium iodide
D L Garner1, L A Johnson, S T Yue
1School of Veterinary Medicine, University of Nevada, Reno 89557.
Abstract:
A new membrane-permeant DNA stain, SYBR-14, was used in combination with propidium iodide (PI) to estimate the proportion of living sperm in bovine semen. The SYBR-14 stained living sperm while PI only stained degenerate cells that had lost their membrane integrity. Staining with SYBR-14 resulted in the nuclei of living sperm fluorescing bright green. Aliquots containing nearly all living bovine sperm were prepared using glass wool/Sephadex filtration to remove dead and damaged cells. A portion of this filtered sample was killed by unprotected freeze-thawing and used to provide mixed aliquots containing known ratios of living and dead sperm. Flow cytometry was used to assess the green and red fluorescence of these mixtures. The percentages of living sperm, as determined by the log of green fluorescence, were 85.1, 68.8, 39.8, 20.7, and 1.4 for ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 of the filtered, killed mixtures. Also, bovine semen was diluted 1:60 in HEPES-0.1% bovine serum albumin and incubated for 0, 3, 6, and 24 hours at 36 degrees C to assess changes in cell viability. As cell death occurred during this incubation period, a relatively rapid transition of staining from green to red occurred as sperm died. Three replicates of cryopreserved sperm from six bulls were also examined using SYBR-14 and PI to assess the proportion of living and dead cells. Flow cytometric analyses of these samples, which had been processed and stored in homogenized milk, indicated that this stain combination was useful in assessing the quality of cryopreserved sperm. The combination of SYBR-14 and PI was determined to be an effective tool for assessing the viability of fresh or cryopreserved sperm.
Insights
A new SYBR-14 and propidium iodide (PI) staining method effectively estimates living sperm viability in fresh and cryopreserved bovine semen. This flow cytometry technique accurately distinguishes between live and dead sperm cells.
Area of Science:
- Reproductive Biology
- Cell Biology
- Biotechnology
Background:
- Assessing sperm viability is crucial for artificial insemination and fertility studies.
- Traditional methods for sperm viability assessment can be time-consuming and subjective.
- Novel staining techniques are needed for accurate and efficient evaluation of sperm quality.
Purpose of the Study:
- To evaluate the efficacy of a new membrane-permeant DNA stain, SYBR-14, in combination with propidium iodide (PI), for estimating the proportion of living sperm in bovine semen.
- To assess the utility of this staining combination for evaluating both fresh and cryopreserved sperm viability using flow cytometry.
Main Methods:
- Bovine sperm samples were stained with SYBR-14 (stains live sperm green) and PI (stains dead sperm red).
- Flow cytometry was used to quantify green and red fluorescence, correlating with live and dead sperm populations, respectively.
- Known ratios of live and dead sperm were created to validate the method's accuracy.
- Sperm viability was also assessed after incubation at 36°C and in cryopreserved samples.
Main Results:
- SYBR-14 and PI staining allowed for accurate differentiation of live (green fluorescence) and dead (red fluorescence) sperm.
- The flow cytometry method demonstrated high accuracy in quantifying sperm viability across various known ratios.
- A rapid transition from green to red fluorescence was observed as sperm underwent cell death during incubation.
- The stain combination proved effective in assessing the viability of cryopreserved bovine sperm.
Conclusions:
- The combination of SYBR-14 and propidium iodide is an effective and reliable tool for assessing the viability of fresh and cryopreserved bovine sperm.
- This flow cytometry-based method provides an accurate and efficient means for sperm quality assessment in reproductive biology and biotechnology applications.