Flow cytometry of human spermatozoa

Bovine sperm sex-selection technology in Japan

BACKGROUND

In Japan, Livestock Improvement Association of Japan started commercially producing sexed bovine semen 10 years ago, and sexed bovine semen is currently used for the artificial insemination (AI) in the farms. In this review, the authors introduce the technology for sperm sexing by flow cytometry, the efforts at commercializing sexed semen in Japan, and recent field data on artificial insemination of the cattle with sexed semen.

METHODS

In the procedures of the flow cytometric method, X-chromosome-bearing sperm and Y-chromosome-bearing sperm were fluorescently stained, separated from each other by analyzing the difference in the DNA content, and cryopreserved. The authors surveyed the conception rates after AI with these sperm and sex ratios of the offspring with the cooperation from livestock associations, AI technicians, and farmers.

MAIN FINDINGS RESULTS

Although AI with sexed semen was associated with lower conception rates in comparison with AI with conventional semen, the accuracy of sex selection using AI with sexed semen was beyond >90%.

CONCLUSION

Sexed semen produced by flow cytometry has the potential to produce offspring of the preferred sex with high accuracy and reliability. Thus, it is expected that sexed semen is used for AI more frequently in the farms.

Sex-sorting sperm using flow cytometry/cell sorting

The sex of mammalian offspring can be predetermined by flow sorting relatively pure living populations of X- and Y-chromosome-bearing sperm. This method is based on precise staining of the DNA of sperm with the nucleic acid-specific fluorophore, Hoechst 33342, to differentiate between the subpopulations of X- and Y-sperm. The fluorescently stained sperm are then sex-sorted using a specialized high speed sorter, MoFlo(®) SX XDP, and collected into biologically supportive media prior to reconcentration and cryopreservation in numbers adequate for use with artificial insemination for some species or for in vitro fertilization. Sperm sorting can provide subpopulations of X- or Y-bearing bovine sperm at rates in the 8,000 sperm/s range while maintaining; a purity of 90% such that it has been applied to cattle on a commercial basis. The sex of offspring has been predetermined in a wide variety of mammalian species including cattle, swine, horses, sheep, goats, dogs, cats, deer, elk, dolphins, water buffalo as well as in humans using flow cytometric sorting of X- and Y-sperm.

Flow cytometric sexing of mammalian sperm

This review reexamines parameters needed for optimization of flow cytometric sexing mammalian sperm and updates the current status of sperm sexing for various species where this technology is currently being applied. Differences in DNA content have provided both a method to differentiate between these sex-determining gametes and a method to sort them that can be used for predetermining sex in mammals. Although the DNA content of all cells for each mammalian species is highly conserved, slight but measurable DNA content differences of sperm occur within species even among cattle breeds due to different sizes of Y-chromosomes. Most mammals produce flattened, oval-headed sperm that can be oriented within a sorter using hydrodynamic forces. Multiplying the percentage the difference in DNA content of the X- or Y-chromosome bearing sperm times the area of the flat profile of the sperm head gives a simple sorting index that suggests that bull and boar sperm are well suited for separation in a flow sorter. Successful sperm sexing of various species must take into account the relative susceptibilities of gametes to the stresses that occur during sexing. Sorting conditions must be optimized for each species to achieve acceptable sperm sexing efficiency, usually at 90% accuracy. In the commercial application of sperm sexing to cattle, fertility of sex-sorted bull sperm at 2 x 10(6)/dose remains at 70-80% of unsexed sperm at normal doses of 10 to 20 x 10(6) sperm. DNA content measurements have been used to identify the sex-chromosome bearing sperm populations with good accuracy in semen from at least 23 mammalian species, and normal-appearing offspring have been produced from sexed sperm of at least seven species.

The relative biological effectiveness of low doses of 14 MeV neutrons in steady-state murine spermatogenesis as determined by flow cytometry

The relative biological effectiveness of 14 MeV neutrons in the low-dose range < or =1 Gy has been determined in differentiating and differentiated spermatogonia. Male NMRI mice were exposed to single doses of 2 cGy to 3 Gy of (60)Co gamma rays or neutrons. The ratios of testicular S-phase cells, 4c primary spermatocytes, and elongated spermatids were quantified by DNA flow cytometry 2 to 70 days after irradiation and were found to decrease. Histological samples and testis weight were analyzed in parallel. Doses of 2-5 cGy neutrons and 10-50 cGy gamma rays significantly (P<0.05) decreased the proportions of S-phase cells, spermatocytes and elongated spermatids at 4, 14 and 28 days postirradiation. For S-phase cells, the biphasic shape of the cell survival curves was described with a D(50) of 5 cGy neutrons. The D(50) for (60)Co gamma rays and the relative biological effectiveness could not be determined. The relative biological effectiveness of neutrons at 50% reductions of testis weight, primary spermatocytes, and elongated spermatids were 2.5, 10.0 and 6.1, respectively. This in vivo assay is interesting because of its sensitivity at dose ranges that are relevant for exposures in the environment, the workplace and radiotherapy.

DNA flow cytometry of human semen

The aim of this study was the evaluation of DNA flow cytometry for the analysis of male infertility. 171 ejaculates from 155 patients with fertility problems were analysed by flow cytometry and by conventional microscopical procedures. Using flow cytometry, it was possible to determine the relative proportions of the various cell populations: mature haploid and abnormal diploid mature spermatozoa, cellular fragments, immature germ cells (haploid round spermatids, diploid cells, S phase and 4C cells), and of leukocytes as indicators of infection. A linear association was observed between sperm concentration in semen as quantified by light microscopy and by flow cytometry, even with fewer than 20x10(6) spermatozoa/ml. Eight classes of histograms, each with differing fractions of spermatozoa and other particles, were obtained and correlated with the results of the spermiograms. During the 10 year follow-up, the two patient groups with a low sperm concentration or a high concentration of cellular debris exhibited significantly impaired fertility. The two patient groups with >/=5% diploid spermatozoa and with malcondensed sperm chromatin were also subfertile. No ovulatory disorders were revealed in the 155 female partners. DNA flow cytometry thus provides an additional dimension to semen analysis not easily gained by other methods and has the advantage of being rapidly performed and interpreted. We therefore recommend application of this technique in the diagnosis of male infertility.

Mitochondrial membrane potential and DNA stainability in human sperm cells: a flow cytometry analysis with implications for male infertility

Sperm cells from control donors of proven fertility and men from barren couples were studied by conventional procedures, i.e., light microscopy as well as flow cytometry. Light microscopy analysis of semen included the measurement of spermatozoa concentration, morphology, and motility. All the men from barren couples were asthenozoospermic at the conventional analysis of semen samples. Flow cytometry was applied to study two important parameters of sperm cells: mitochondrial membrane potential (MMP) assessed by the cationic dye JC-1 and DNA stainability with propidium iodide (PI). JC-1 staining was more reliable than the classical procedure used for this purpose, i.e., rhodamine 123 (Rh123) staining, and allowed us to show a positive correlation between MMP and spermatozoa motility. Regarding DNA analysis, a higher relative percentage of immature spermatozoa, showing a high accessibility of DNA to the intercalating PI fluorochrome, was found in men from barren couples compared to donors of proven fertility. The relative percentage of immature spermatozoa was significantly higher in semen from oligoasthenozoospermic subjects. Moreover, a positive correlation was found between immature spermatozoa, as evaluated by PI staining, and cells with depolarized mitochondria, as evaluated by JC-1 staining, suggesting that spermatozoa defective for nuclear maturity could be functionally defective cells. No correlation between immature spermatozoa determined by FCM and immature spermatozoa determined by light microscopy was found, suggesting that these two techniques assess sperm cell maturity at different levels.

Flow cytometric determination of binding of monoclonal antibodies to human spermatozoa

Although several monoclonal antibodies to sperm antigens are available, only few systematical reports on the appearance of distinct antibody binding structures in spermatozoa of infertile patients are available. We studied the binding frequency of six monoclonal antibodies (TUS-1, -2, -10, -17, -19, -20) by means of a flow cytometer in different semen samples and their possible relationship to other sperm parameters, in particular to the motility parameters as determined by computer-assisted semen analysis. The percentage of vital spermatozoa binding the different antibodies was 21.5% (TUS-2) to 52.1% (TUS-20). The percentage binding was higher in samples with normozoospermia than in those with oligo-asthenoteratozoospermia. A significant correlation occurred between sperm concentration and the percentage of spermatozoa stained by TUS-2 and TUS-17; between motile spermatozoa and those binding TUS-17 and TUS-20; the velocity average path and those binding TUS-17; an inverse correlation occurred between the morphologically-abnormal spermatozoa and those binding TUS-20; an inverse correlation between TUS-17 and acrosin. We conclude from our results that although the antigens of the antibodies concerned are not yet characterized, the determination of antibody binding will give additional information on the functional status during capacitation and acrosome reaction of spermatozoa.

Effect of low doses of gamma-radiation on the steady-state spermatogenesis of mouse: a flow-cytometric study

Radiation-induced perturbations in the steady-state spermatogenesis of mouse exposed to 0.05 to 2 Gy of 60Co gamma-radiation were studied at 7 to 70 days post-irradiation flow cytometrically. Five quantifiable populations viz: elongated spermatids (HC), round spermatids (1C), spermatogonia and other diploid cells (2C), spermatogonial cells synthesizing DNA (S-phase) and primary spermatocytes (4C) were identified in the sham-irradiated controls. Exposure of mice to different doses of radiation resulted in a significant decline in the total germ-cell transformation ratio (1C:2C) at 21 and 28 days post-irradiation as compared to the control group, except for the animals exposed to 0.05 Gy. The 1C:2C ratio is sub-divided into two components viz. 4C:2C and 1C:4C. The 4C:2C ratio decreased significantly on day 14 post-irradiation, except for 0.05 Gy where it was non-significant. Consequently, meiotic transformation (1C:4C) showed a significant increase on day 14 post-irradiation compared to the sham-irradiated control barring 0.05 Gy where the difference between the two groups was non-significant. The ratio of HC:1C (cell transformation during spermiogenesis) increased significantly at day 21 post-irradiation 0.2 to 2 Gy and between day 7 and 14 for 0.05 Gy as compared to the control group. It appears that a dose as low as 0.05 Gy radiation was able to cause the perturbations in the steady-state spermatogenesis of mouse and normalcy was not restored even up to 70 days post-irradiation at all exposure doses.

DAPI: a DNA-specific fluorescent probe

DAPI (4',6-diamidino-2-phenylindole) is a DNA-specific probe which forms a fluorescent complex by attaching in the minor grove of A-T rich sequences of DNA. It also forms nonfluorescent intercalative complexes with double-stranded nucleic acids. The physicochemical properties of the dye and its complexes with nucleic acids and history of the development of this dye as a biological stain are described. The application of DAPI as a DNA-specific probe for flow cytometry, chromosome staining, DNA visualization and quantitation in histochemistry and biochemistry is reviewed. The mechanisms of DAPI-nucleic acid complex formation including minor groove binding, intercalation and condensation are discussed.

The fertility of patients with clinical stage I testis cancer managed by nerve sparing retroperitoneal lymph node dissection

Nerve sparing retroperitoneal lymph node dissection reliably preserves emission and ejaculation in patients with clinical stage I nonseminoma. The fertility of 51 patients who underwent nerve sparing retroperitoneal lymph node dissection was assessed by 3 different methods: standard semen analysis, analysis of chromatin content by deoxyribonucleic acid histogram and assessment of ultimate fertility status by a questionnaire. Approximately 75% of these patients have semen analyses generally considered to be in the normal range. Virtually all patients who underwent deoxyribonucleic acid histogram analysis had histograms similar to controls. A retrospective analysis of fertility was performed in 201 patients who had previously undergone nerve sparing retroperitoneal lymph node dissection. Of these patients who attempted pregnancy after nerve sparing retroperitoneal lymph node dissection 76% have been successful. Approximately 75% of patients who present with clinical stage I nonseminoma are potentially fertile. Nerve sparing retroperitoneal lymph node dissection is capable of preserving this potential in allowing these patients to father children.

Cellular effects of diagnostic Doppler ultrasound on murine spermatogenic cells monitored by flow cytometry

A study has been carried out to investigate the possible effects caused by Doppler diagnostic ultrasound on murine spermatogenesis. The frequency of the different types of cells has been analyzed using flow cytometry. Exposure to ultrasound was carried out using a commercial device used in diagnostic conditions. Male hybrid mice were exposed to ultrasound for 30 min and observed from 7 to 35 days after treatment. Flow cytometrical analysis showed changes in the relative frequency of the elongated spermatids and this was used as an end-point. A statistically significant decrease in the frequency of this cell type was observed after 7 and 35 days with both pulsed and continuous ultrasound. With the former, a decrease was also seen in this compartment after 14 and 21 days. Our results have shown that diagnostic ultrasound used in the Doppler technique induces effects on specific cell types of murine spermatogenesis.

Utility of light scatter in the morphological analysis of sperm

We were able to differentiate the morphologically diverse sperm nuclei of four animal species by using an Ortho flow cytometer to detect the forward light scatter from a red (helium-neon) laser. Cytograms depicting the axial light loss and forward red scatter signals revealed unique, but reproducible, sigmoid distributions that reflected not only interspecies differences in shape and size, but variations in particle refractive index and orientation within the flow cell at the time of analysis. Consequently, we were able to use regional gating of the light scatter cytogram to minimize the influence of orientation on the resolution of the fluorescence signal. We also observed that sperm enlarging as a result of chemically induced decondensation exhibit over time a biphasic shift (increase, then decrease) in light scatter at a species-dependent rate. These results suggest that, without any special adaptations to the flow cytometer, light-scatter parameters can be used to discriminate morphologically different sperm, to enhance the resolution of fluorescence measurements that may otherwise be confounded by variability in radial orientation, and to detect alterations in the rate of a biochemical/biophysical process such as decondensation.

Effects of heat on mouse spermatogenesis monitored by flow cytometry

The effects of heat on mouse spermatogenesis have been determined using both testis weight and flow cytometrically determined DNA content distribution as experimental end-points. Temperatures of 38-42 degrees C and exposure times of 20-60 min have been tested. The results concerning the testis weight substantially confirm those reported by other authors (Hand et al. 1979). The measurement of DNA content distributions shows a relatively higher depletion, 14 days after treatment, of the cytometric compartment containing elongated spermatids in respect to that containing round spermatids. The analysis of the cytotoxic effects, monitored 14 vs. 28 days after treatment, as a function of the exposure time at a given temperature, or of the temperature for a fixed exposure time, indicates that, in the course of spermatogenesis, late spermatocytes are more sensitive to heat than differentiated spermatogonia. Following the approach based on flow cytometry, the effect of exposures as low as 20 min at 38 degrees C can be appreciated.

Flow sorting of X and Y chromosome-bearing mammalian sperm: activation and pronuclear development of sorted bull, boar, and ram sperm microinjected into hamster oocytes

Flow cytometric techniques were used to measure relative DNA content of X and Y chromosome-bearing bull, boar, and ram sperm populations and to separate the two sex-determining populations. Neat semen was prepared for flow cytometric analysis by washing, light sonication, and staining with 9 microM Hoechst 33342. Computer analysis of the bimodal histograms showed mean X-Y DNA differences of 3.9, 3.7, and 4.2% for bull, boar, and ram, respectively. Flow cytometric reanalysis of sorted bull, boar, and ram sperm showed purities greater than 90%. Bull, boar, and ram sperm nuclei were microinjected into hamster oocytes. Microinjected sperm were either unsorted, sorted, unsorted plus dithiothreitol (DTT) exposure, or sorted plus DTT exposure. Following microinjection, eggs were incubated 3 hr, fixed, and stained. A total of 579 eggs was observed for sperm activation (decondensation or formation of a male pronucleus). A lower percentage of sorted than unsorted (3 vs. 23%) boar sperm was activated (P less than .05). However, sorted and unsorted DTT-exposed boar sperm or sorted and unsorted bull or ram sperm, regardless of DTT treatment, did not differ significantly. Sorted sperm nuclei of both rams and bulls exhibited higher activation rates than sorted boar sperm (P less than .05). Treatment of sperm with DTT increased the activation rate (P less than .05) for sorted boar sperm but not for bull or ram sperm.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometry of X and Y chromosome-bearing sperm for DNA using an improved preparation method and staining with Hoechst 33342

A new and improved method of preparing mammalian spermatozoa for high resolution flow cytometric DNA analysis and flow sorting is described. Ejaculated or cryopreserved sperm were briefly sonicated to remove tails and then stained with Hoechst 33342. This simple procedure was found superior to more severe treatments of dimethylsulfoxide washes, fixation in 80% ethanol, and protease digestion of the sperm membranes and tails by papain. Flow cytometric DNA analyses of sperm samples subjected to varying sonication times indicated that X and Y chromosome-bearing sperm populations could be well resolved with as little as 15-sec sonication. In addition, a comparison of sonicated samples stained with four concentrations of bisbenzimide (Hoechst 33342) or 4',6-diamidino-2-phenylindole (DAPI) indicated that 2.5 or 5.0 micrograms/ml of Hoechst was sufficient to resolve the X and Y sperm populations. In order to quantitatively describe the flow cytometric data, several indices (sample quality, orientation and splitting) were developed.

Flow cytometric analysis of the effects of 0.4 MeV fission neutrons on mouse spermatogenesis

(C57Bl/Cne X C3H/Cne)F1 male mice were irradiated with single acute doses of 0.4 MeV neutrons ranging from 0.05 to 2 Gy, and testis cell suspensions were prepared for cytometric analysis of the DNA content 2-70 days after irradiation. Various cell subpopulations could be identified in the control histogram including mature and immature spermatids, diploid spermatogonia and spermatocytes, tetraploid cells and cells in the S-phase. Variations in the relative proportions of different cell types were detected at each dose and time, reflecting lethal damage induced on specific spermatogenetic stages. The reduction of the number of elongated spermatids 28 days after irradiation was shown to be a particularly sensitive parameter for the cytometrical assessment of the radiosensitivity of differentiating gonia. A D0 value of 0.13 Gy was calculated and compared with data obtained after X-irradiation, using the same experimental protocol. In the latter case a biphasic curve was obtained over the dose range from 0.25 to 10 Gy, possibly reflecting the existence of some cell population heterogeneity. RBE values were estimated at different neutron doses relative to the radiosensitive component of the X-ray curve, and ranged from 3.3 to 4, in agreement with data in the literature. Genotoxic effects were monitored 7 days after irradiation by a dose-dependent increase of the coefficient of variation (CV) values of the round spermatid peak, reflecting the induction of numerical and structural chromosome aberrations, and 14 or 21 days after irradiation by the detection of diploid elongated spermatids, probably arising from a radiation-induced complete failure of the first or second meiotic division.

Flow sorting of X and Y chromosome-bearing spermatozoa into two populations

The only established difference on which to base the separation of X and Y chromosome-bearing spermatozoa is chromosomal constitution. This difference is quantifiable both from chromosome morphology (karyotype) and from DNA content. Flow cytometric techniques were used to measure relative DNA content of the X and Y populations and to flow-sort spermatozoa from Chinchilla laniger. Epididymal spermatozoa were recovered in PBS, fixed in 80% ethanol, treated with papain and dithioerythritol, and stained for DNA with Hoechst 33342. Sperm nuclei were analyzed and sorted on an EPICS V flow cytometer/cell sorter, modified specifically for spermatozoa. Two clearly resolved peaks (coefficient of variation less than 1.5%) with approximately 7.5% difference in DNA content between X and Y chromosome-bearing spermatozoa were evident. Sperm nuclei were sorted from a portion of the X and Y peaks at a rate of 55 nuclei/sec for each population. Purities of individual X and Y populations averaged 95% as determined by reanalysis of the sorted populations. Successful sorting of Chinchilla X and Y chromosome-bearing spermatozoa into separate populations may aid in the identification of a biochemical marker that could be used to discriminate between the two sperm populations and lead to a practical procedure for sexing spermatozoa.

Comparison of histologic and flow cytometric evaluation of cyclophosphamide-induced testicular damage

This study evaluates the ability of DNA histograms obtained by flow cytometry to detect and quantify reversible alterations in spermatogenesis induced by cyclophosphamide, a known inhibitor of spermatogenesis. Evaluation of per cent of cells in each of the haploid (lc), diploid (2c), and tetraploid peaks (4c) as determined by flow cytometry in treated and control Balb/C mice over a six-week period, and comparison with routine histologic evaluation have led us to conclude that DNA histogram evaluation is a rapid and accurate means of identifying testicular damage and recovery. This technique may be useful in sequential monitoring of the effects of malignancy and/or treatments applied on spermatogenesis in young men.

Flow cytometry of postmortem human testicular tissue in cases of atherosclerosis

From forty-seven autopsy cases of atherosclerosis flow cytometry (FCM) of DNA and histology of both testes are compared with the histological sections of their supplying vessels arteriae testiculares and arteriae ductus deferentis at different levels. By this method, changes of spermatogenesis are judged separately for each side and the results can be related to the local conditions of blood supply. Four young men, dead after traffic accidents, served as control. In the majority of cases, the computer-assisted evaluations of the meiotic DNA histograms show no differences between the right and left testis, even when differences of the arterial diameters are found by histology. On the other hand, cases with distinct differences in the histograms can show insignificant pathological alterations of the vessels. Though most excessive forms of macroscopic and microscopic atherosclerosis do not necessarily lead to a significant reduction in spermatogenesis, some cases with moderate forms show a strong reduction or even a total loss. This discrepancy can best be explained by superposition of other diseases.

Flow cytometry and sizing for routine andrological analysis

Flow fluorometry and Coulter type sizing analysis of sperm have been applied separately in order to improve human semen analysis. Different methods of sample preparation were evaluated and a protocol involving prestaining pepsin treatment of sperm samples is proposed for fluorometric analysis. The data obtained with fluorometry and sizing analysis result in different kinds of information: Coulter counting allows to automate sperm counting and fluorometry yields more detailed information about normozoospermia and oligozoospermia by determining the proportion of mature spermatozoa and immature germ-cells. These two methods, together with light microscopy, may help to explore the correlation of fertility and pathology of spermatozoa. The aim of these investigations is to yield the preconditions for simultaneous two-parameter analysis of DNA content and cellular size distributions.

Cytometry of deoxyribonucleic acid content and morphology of mammalian sperm

Because spermatogenesis is exquisitely sensitive to external influences, sperm can serve as a biological dosimeter. Advances in interpreting induced sperm abnormalities require a better understanding of sperm characteristics. This report reviews the application of several methods for automated, quantitative detection of shape changes, methods that are faster and more sensitive than conventional subjective techniques. Variability of sperm deoxyribonucleic acid content as a bioassay of genetic damage is explored, and limitations of the bioassay are discussed. New flow cytometric techniques that could lead to sexing mammalian sperm are examined.

Flow cytometry of human testicular tissue

Flow cytometry of testicular tissue from autopsies showed differences in the proportion of substained spermatozoa (1 CA), spermatids (1 CB), diploid 2C nuclei and premeiotic spermatozoa in the 4 C class. The evaluation of the histograms was performed with computer assistance. Healthy accident cases or those delivered in forensic medicine furnished the control values. Patients with hepatic cirrhosis showed a nearly complete loss of the haploid class, while cases with fatty degeneration of the liver demonstrated a reduction. Circulatory insufficiency in cases of acute shock resulted in an increase in the 4C values of meiotic prophase I and a decrease of spermatids. Spermatozoa were normal in these cases. After prolonged shock a nearly complete breakdown of spermatogenesis was observed. In cases of atherosclerosis an irregular degree of reduction was seen. Cancer patients showed a reduction of spermatogenesis in correlation to therapy.

High resolution DNA content measurements of mammalian sperm

The high condensation and flat shape of the mammalian sperm nucleus present unique difficulties to flow cytometric measurement of DNA content. Chromatin compactness makes quantitative fluorescent staining for DNA difficult and causes a high index of refraction. The refractive index makes optical measurements sensitive to sperm head orientation. We demonstrate that the optical problems can be overcome using the commercial ICP22 epiillumination flow cytometer (Ortho Instruments, Westwood, MA) or a specially built cell orientating flow cytometer (OFCM). The design and operation of the OFCM are described. Measurements of the angular dependence of fluorescence from acriflavine stained rabbit sperm show that it is capable of orienting flat sperm with a tolerance of +/- 7 degrees. Differences in the angular dependence for the similarly shaped bull and rabbit sperm allow discrimination of these cells. We show that DNA staining with 4-6 diamidino-2-phenylindole (DAPI) or an ethidium bromide mithramycin combination allows resolution of the X and Y populations in mouse sperm. They have also been successful with sperm from the bull, ram, rabbit, and boar. Reliable results with human sperm are not obtained. The accuracy of the staining and measurement techniques are verified by the correct determination of the relative DNA content of these two populations in sperm from normal mice and those with the Cattanach [7 to X] translocation. Among the potential uses of these techniques are measurement of DNA content errors induced in sperm due to mutagen exposure, and assessment of the fractions of X and Y sperm in semen that may have one population artifically enriched.

Stage-related variations in DNA fluorescence distribution during rat spermatogenic cycle measured by flow cytometry

Living segments of rat seminferous tubules representing the fourteen stages of the spermatogenic cycle have been isolated for DNA flow cytometry using the transillumination-assisted microdissection procedure. The resulting DNA profiles showed stage-related variations in the proportions of cells within the haploid (1C), diploid (2C) and tetraploid (4C) classes. Three distinct populations of haploid cells could be distinguished according to differences in fluorescence intensity of their nuclear DNA. The major haploid peak (1C) was found to reflect the steps 1-11 spermatids, the first hypofluorescent peak (fluorescence intensity from 0.45-0.75C) the steps 12-15 spermatids and the second hypofluorescent peak (fluorescence intensity of ca 0.25C) the maturing steps 16-19 spermatids. The changes in fluorescence intensity could thus be correlated with nuclear protein transitions that are known to occur during spermiogenesis in rats. The results indicated that tht processes responsible for the changes in nuclear fluorescence intensities are rapidly occurring, although not synchronously in all spermatids at the same developmental stages.

Clinical application of flow cytometry: a review

A survey of the use of flow cytometry for clinical purposes is given. In the last decade the main clinical application of this technique has been measurements of cellular DNA content for estimation of cell cycle distribution and ploidy studies. A large body of data is now available on the presence of aneuploidy in different malignant diseases. By measurements with high resolution, the demonstration of abnormal cellular DNA content in several types of tumors can be of definite diagnostic value when combined with conventional diagnostic procedures. The prognostic significance of different types of DNA aberrations is so far not established. Attempts to monitor cancer treatment by studying altered cell cycle distribution have not been successful, although some applications are of potential value. The main reasons for this are the complexity of tumor tissue as well as difficulties with interpretation of altered cell cycle distribution caused by drug combinations. For further progress in this field more emphasis on other cell constituents than DNA measured by flow cytometry is desirable, either as single or as multiparameter measurements.

Effects of acute gamma-irradiation on spermatogenesis as revealed by flow cytometry

Mice irradiated with doses ranging from 0.1 to 15 Gy using a 60Co-source and controls were killed at intervals varying from 2 to 35 days after irradiation. The DNA content of the testicular cells in single cell suspensions was measured with the pulse cytophotometer to determine the frequencies of the different stages in the spermatogenesis. The relative amount of S-phase and 4c-cells was reduced initially but increased subsequently to hypernormal values. A decrease of 2c-cells indicated a higher cell-kill of diploid spermatogonia. Gamma ray-induced spermatids with abnormal DNA-values (diploid sperm) were identified. The results suggest that the spermatogenesis can be analysed with flow cytometry and used as a biologic dosimeter even for small doses of ionizing radiation.