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Estimation of the frequency of malformed sperm by slit scan flow cytometry
Abstract:
We have investigated the utility of Slit Scan Flow Cytometry (SSFCM) for measuring the frequencies of malformed sperm heads in control and mutagen treated B6C3F1/CRL mice. In SSFCM, fluorescence profiles of sperm heads stained with the DNA-specific fluorescent dye acriflavine were recorded for sperm flowing lengthwise through a 2.5-microns-thick laser beam. Malformed sperm were detected as having fluorescence profiles that differed substantially from an average fluorescence profile for sperm from untreated mice. Specifically, a sum of squared difference (SSD) value was calculated for the fluorescence profile of each sperm according to the equation (Formula: see text) where c(i) and t(i) are the ith values for the fluorescence profiles from control and test sperm, respectively. Profiles whose SSD exceeded a threshold value of 20 were considered to be from malformed sperm. We measured fluorescence profiles for 500 sperm per mouse from five control mice, five mice injected intraperitoneally daily for 5 days with a total of 375 mg/kg of body weight methyl methane sulfonate (MMS), and for 30 mice injected intraperitoneally daily for 5 days with total doses of procarbazine ranging from 125 mg/kg to 1,250 mg/kg. Sperm were collected from the caudae epididymides 35 days after the last injection. Frequencies of malformed sperm in these samples were also estimated by visual analysis. All samples were analyzed in double blind fashion. The visual and SSFCM malformed sperm frequencies for the samples from control, MMS-treated, and procarbazine-treated mice were correlated (r = 0.83). A dose effect was seen with both the visual and SSFCM estimates for the sperm from the procarbazine-treated mice.
Insights
Slit Scan Flow Cytometry (SSFCM) effectively measures malformed sperm heads in mice. This method correlated well with visual analysis, showing a dose-dependent effect with mutagen exposure.
Area of Science:
- Reproductive toxicology
- Flow cytometry
- Sperm analysis
Background:
- Assessing sperm head morphology is crucial for evaluating reproductive health and genotoxicity.
- Traditional methods like visual analysis can be labor-intensive and subjective.
- Novel techniques are needed for more efficient and objective sperm abnormality assessment.
Purpose of the Study:
- To evaluate the utility of Slit Scan Flow Cytometry (SSFCM) for quantifying malformed sperm heads.
- To compare SSFCM results with traditional visual analysis in mutagen-treated mice.
- To assess the sensitivity of SSFCM to dose-dependent effects of chemical mutagens.
Main Methods:
- Sperm samples from control and mutagen-treated B6C3F1/CRL mice were analyzed using SSFCM.
- Sperm heads were stained with acriflavine, and fluorescence profiles were recorded.
- Malformed sperm were identified based on deviations from control profiles using a sum of squared difference (SSD) threshold.
- Visual analysis was performed concurrently on the same samples in a double-blind manner.
Main Results:
- SSFCM successfully identified malformed sperm heads based on distinct fluorescence profiles.
- A strong correlation (r = 0.83) was observed between SSFCM and visual assessment of malformed sperm frequencies.
- Both methods detected a dose-dependent increase in malformed sperm following procarbazine treatment.
- Methyl methane sulfonate (MMS) treatment also resulted in increased malformed sperm frequencies detectable by SSFCM.
Conclusions:
- Slit Scan Flow Cytometry (SSFCM) is a viable and objective method for measuring sperm head malformations.
- SSFCM offers a high-throughput alternative to manual sperm morphology assessment.
- The technique demonstrates sensitivity to mutagenic effects and dose-response relationships in reproductive toxicology studies.