Induction of shape abnormality and unscheduled DNA synthesis by arecoline in the germ cells of mice

The ability of arecoline, an alkaloid of betel nut, to induce abnormality in the shape of sperm heads and unscheduled DNA synthesis (UDS) in the early spermatid stages of Swiss albino mice was studied. Treatment of mice with arecoline at the dose levels of 20, 40 and 80 mg/kg elicited dose-related increase in the number of abnormal sperm heads, as well as the unscheduled incorporation of [3H]thymidine into the DNA of early spermatids. Such increase in the production of abnormally shaped sperms and UDS response of the early spermatids following arecoline treatment expressed its genotoxic potential in the mouse germ cells.

Long-term infertility and dominant lethal mutations in male mice treated with adriamycin

Sperm production and fertility were studied in male mice treated with adriamycin (ADR) at 6 or 8 mg/kg. Testicular sperm production and epididymal sperm counts were markedly reduced after ADR treatment. Gradual recovery of counts occurred, but sperm counts had not reached control levels even more than 1 year after treatment. Epididymal sperm showed treatment-induced morphological abnormalities throughout the experiment; the frequencies of sperm with detached tails and the frequencies of sperm with morphologically abnormal heads remained elevated about 2-3-fold above control. According to the frequency of vaginal plugs, treated male mice mated at control rates with untreated females during the post-treatment sterile period. However, after some fertility was regained the fertilization rate (calculated as the fraction of eggs, flushed from the oviduct 2 days after mating, that had been fertilized and had cleaved) was markedly reduced and remained depressed for the remainder of the experiment. The fertilization rate reached only 0.29 at 23-32 weeks after 8 mg/kg ADR and 0.76 at 16-23 weeks after 6 mg/kg ADR; both values were significantly below the control value of 0.94. Dominant lethal mutations in the zygotes flushed from the oviduct were measured in culture by the loss of the zygote's ability to develop to a stage characterized by trophectoderm outgrowths and formation of an inner cell mass. The frequencies of dominant lethal mutations detected in vitro were 1.7 or 7.4% after 6 mg/kg, and 32 or 40% after 8 mg/kg ADR; each value was calculated in two different ways, with 3 of these 4 values significantly different from zero. We conclude that even after mice regain fertility following ADR exposure, the level of fertility remains permanently subnormal as evidenced by a lack of fertilization of eggs that is probably due to the decreased quantity and quality of spermatozoa produced. Furthermore, ADR can induce genetic damage in stem spermatogonia, which can be transmitted through fertile spermatozoa. Thus, there may be a genetic risk to the offspring of cancer patients treated with ADR chemotherapy, but at present we are unable to quantitate that risk.

Reproductive effects of inhaled methyl chloride in the male Fischer 344 rat. II. Spermatogonial toxicity and sperm quality

Studies were performed to assess the effects of inhaled methyl chloride (MeCl) on sperm quality and testicular histopathology in the Fischer 344 rat. Adult male F-344 rats were exposed to 1000 or 3000 ppm MeCl 6 hr/day for 5 days, or received an ip injection of 0.2 mg triethylenemelamine (TEM)/kg on the afternoon of Day 5. Five males from a control group and each of the three treatment groups were killed weekly for 8 weeks, and five more from the control and 3000 ppm groups at Week 16 postexposure. Male rats from the 1000 ppm MeCl- and TEM-exposed groups exhibited no consistent difference from control males in any parameter measured. In the 3000 ppm MeCl group, over 50% of the males had uni- or bilateral sperm granulomas in the cauda epididymis. Testes weights were significantly depressed in these males by 3 weeks postexposure, and remained depressed as late as 8 weeks after treatment. Testicular spermatid head counts were significantly lower by 2 weeks postexposure, and the testes showed a characteristic cytotoxic response to MeCl exposure, including a delay in spermiation, chromatin margination in round spermatids, epithelial vacuolation, luminal exfoliation of spermatogenic cells, and multinucleated giant cells. Counts of repopulating seminiferous tubule cross sections and of testicular sperm heads at 7 weeks postexposure indicated that 60 to 70% of the spermatogonial stem cells had been killed by MeCl exposure. Sperm isolated from the vasa deferentia had significantly depressed numbers and an elevated frequency of abnormal sperm head morphology by Week 1 postexposure, and significantly depressed sperm motility and an elevated frequency of headless tails by Week 3 postexposure. All parameters measured in the testes and in vasa deferentia sperm showed varying degrees of recovery, and all were near the normal range by Week 16 postexposure except sperm count. These data suggest that the previously reported high preimplantation loss caused by methyl chloride exposure may be primarily due to cytotoxic effects on the testis and epididymal epithelium, rather than to direct genotoxic effects on the sperm.

[Quantitative changes in histones during the formation of structures characteristic of the male pronucleus in mammalian spermatozoa in vitro]

Treatment of bull spermatozoa with DDC--Na/dithiothreitol results in the swelling and decondensation of nuclear chromatin. The structures formed at the final stages of decondensation are morphologically similar to the male pronucleus. Cytophotometric analysis has shown that decondensation of chromatin in the gametes in followed by quantitative changes of basic nuclear proteins. In partly--decondensed sperm nuclei the intensity of histone staining increases as a result of the appearance of extra reactive groups. In fully decondensed nuclei there remain only 54% of histones of the original haploid level. Nucleoproteins revealed in the sperm with fully dispersed chromatin must be histones of the somatic type.

Evaluation of chemicals used for drinking water disinfection for production of chromosomal damage and sperm-head abnormalities in mice

Chemical oxidants are commonly added during water treatment for disinfection purposes. These chemicals have not been tested previously for their ability to induce genetic damage in vivo. Chlorine (hypochlorite and hypochlorous acid), monochloramine, chlorine dioxide, sodium chlorite, and sodium chlorate were evaluated for induction of chromosomal aberrations and micronuclei in bone marrow of CD-1 mice, and for induction of sperm-head abnormalities in B6C3F1 mice. Oral administration of chlorine at pH 8.5 (where hypochlorite predominates) at dose levels equivalent to approximately 4 and 8 mg/kg/day induced significant increases in the level of sperm-head abnormalities. There was no evidence of other effects with any of the disinfectants. Halogenated acetonitriles, which have previously been shown to form in the stomach following oral dosing of sodium hypochlorite to rats, were also tested in the sperm-head abnormality assay but gave no indication of an effect.

Side-effects of salazopyrin on male fertility

The author critically studied the twelve papers and letters to the editor published since 1979 regarding toxic effects of Salazopyrin on male fertility. A direct toxic side-effect of Salazopyrin on the maturation of sperm cells is apparent, but associated influencing factors are the basic illness itself and associated therapy forms, such as steroids, that also influence spermatogenesis. The mechanism of action of Salazopyrin is still a matter of dispute. Possible (and possibly combined) interfering factors are: an anti-folate action with influence on the rapid turnover of dividing spermatogenic cells, an anti-prostaglandin effect on motility and toxic effects of the sulphapyridine substance of Salazopyrin.

Evaluation of genotoxic potential of vincristine from multiple parameters

The genotoxic potential of vincristine is assessed by in vivo and in vitro cytogenetic assays on two test systems using multiple parameters. In in vivo experiments it was administered intraperitoneally to Swiss albino mice at doses computed on a surface area basis to lie within the therapeutic range. The parameters employed include screening of chromosome mutational activity in bone marrow and meiotic cells for periods covering one spermatogenetic cycle, in vivo SCE analysis and sperm head abnormality assay. In vitro studies included conventional scoring for chromosome mutations from human leucocyte cultures following administration of the drug at doses within the therapeutic range on the basis of blood volume. Strict controls were employed in both test systems. The data were treated by appropriate statistical tests to evaluate their validity. The results of in vivo experiments on somatic as well as meiotic test systems reveal a lack of clastogenic action of the compound. Both sexes respond in an identical fashion regarding this activity. The SCE analysis supports the in vivo nonclastogenic action of vincristine. Total univalents significantly seen with the highest dose after 1 and 2 weeks must be considered as being important as they can lead to aneuploidy. Evidence is adduced from sperm head abnormality assay that the drug induces point mutations. The results from in vitro test system indicate a positive chromosome mutational property. This is substantiated by results of in vitro SCE analysis. A comparison of data from in vivo and in vitro test systems suggests that a metabolic conversion of the compound in the former might render it innocuous for expressing the chromosome mutational activity. They also point out that vincristine evokes a differential clastogenic response in the two test systems despite bringing about an anaphase arrest commonly in both by acting on cytokinesis.

Alteration of free sulphydryl content of rat sperm heads by suppression of intratesticular testosterone

Subcutaneous injections of testosterone propionate to adult male rats at a dose of 2.5 or 10 mg/kg body weight, 3 times per week for 7 weeks, resulted in a 75% reduction in serum LH and more than 50% reduction in intratesticular testosterone concentration, but serum FSH levels remained unchanged. The free -SH content, measured as iodo[14C]acetamide binding, increased by 70-100% in testicular sperm heads after suppression of testicular testosterone, and by 25-30% in caput epididymal sperm heads but was decreased by 70-80% in cauda epididymal sperm heads. These results demonstrate an alteration in the oxidative state of sperm nuclear basic proteins, suggesting incomplete nuclear maturation. These changes may be specific for the suppression of intratesticular testosterone, thus illustrating the androgen dependency of sperm head maturation. The contrast effects noted between the iodo[14C]iodoacetamide binding by the caput and the cauda epididymal sperm heads indicate that testosterone propionate treatment may affect the mechanisms regulating the oxidation of the sulphydryl residues in sperm heads during epididymal transit. This alteration may not directly relate to the tissue androgen concentrations.

Stimulation of an exocytotic event, the hamster sperm acrosome reaction, by cis-unsaturated fatty acids

The cis-unsaturated fatty acids oleic, arachidonic and cis-vaccenic stimulated the hamster sperm acrosome reaction in vitro (an exocytotic event which occurs in the sperm head and which is essential for fertilization). The trans-isomers of oleic and vaccenic acids did not stimulate the acrosome reaction, nor did the cis-unsaturated fatty acids petroselenic and docosahexaenoic or the saturated fatty acids lauric, myristic or stearic. This is the first report of a stimulatory effect of cis-unsaturated fatty acids on an exocytic event in an intact viable cell.

Dissociation of intermolecular linkages of the sperm head and tail by primary amines, aldehydes, sulphydryl reagents and detergents

Primary amines, pyridoxal and thiols induced separation of the mammalian sperm head and tail at specific sites across the head-tail junction. Primary amines and pyridoxal induced head detachment by allowing separation of the inner and outer nuclear envelope membranes adjacent to the tail basal plates. This detachment was prevented by prior reduction with sodium cyanoborohydride. The chemistry of amine-induced head separation and the similar action of pyridoxal indicate that the head and tail are joined by Schiff bases formed between proteins within the nuclear membranes. Head detachment with thiols occurred at two sites: across the connecting filaments linking the basal plate and the capitulum of the tail-neck complex and between the inner nuclear membrane and the nuclear chromatin. Mammalian epididymal spermatozoa exhibited species differences in susceptibility to head detachment induced by hydromechanical shear. The heads of mouse epididymal spermatozoa readily separated from the tails during vortexing whereas those from the vas deferens were resistant to shear. Head separation occurred at the same site as induced by primary amines. Rabbit spermatozoa from all parts of the epididymis were resistant to mechanical shear. Species differences in the mechanical stability of the head-tail junction suggest that the intermolecular Schiff bases linking the head and tail can be formed before or during sperm transport in the epididymis and that their formation probably occurs after the appearance of the periodic structures which bridge the inner and outer membranes of the nucleus in the region of the tail basal plate.

Evaluation of a testicular sperm head counting technique using rats exposed to dimethoxyethyl phthalate (DMEP), glycerol alpha-monochlorohydrin (GMCH), epichlorohydrin (ECH), formaldehyde (FA), or methyl methanesulphonate (MMS)

Single dosages of DMEP (1,000-2,000 mg/kg), GMCH (50 mg/kg), ECH (25 and 50 mg/kg), FA (100 and 200 mg/kg), and MMS (100-400 mg/kg) were administered orally to 10 week old male Wistar rats. The rats were necropsied on the 11th day following dosing. The testes were weighed, homogenised and sonicated; numbers of sperm heads (total and abnormal) were counted and percentage sperm head abnormalities were calculated. Testes weights were significantly reduced only in rats exposed to 1,500 and 2,000 mg DMEP/kg. Compared with controls, there were significant increases in the incidence of abnormal sperm at all dose levels of MMS and the higher dose levels of DMEP (1,500 and 2,000 mg/kg), ECH and FA. No toxicologically significant effects upon total sperm counts were seen following the oral administration of any of the five chemicals tested. However, an additional group of rats given 100 mg MMS/kg intraperitoneally (i.p.) showed significant reductions in testes weight and total sperm head counts compared with control animals. It is concluded that this testicular sperm head counting technique is a useful tool in the detection of selective adverse effects of chemicals upon testicular sperm but requires further evaluation.

Gossypol--an effective male contraceptive was not mutagenic in sperm head abnormality assay in mice

Gossypol acetic acid, a potential male anti-fertility compound, was investigated for its mutagenic effects in the mouse sperm head abnormality assay. Compared with the controls, the chemical at 20 and 40 mg/kg doses did not increase detectable sperm head abnormalities in mice.

Electron microscopic and biochemical analyses of the organization of human sperm chromatin decondensed with sarkosyl and dithiothreitol

Human sperm chromatin was decondensed by treating the purified sperm heads with Sarkosyl for 60 minutes followed with dithiothreitol (DTT) for 20 minutes and overnight. Following Sarkosyl treatment all histones and nonhistones were removed; the remaining nucleoprotamines in the sperm heads exhibited two levels of higher-order structure in the forms of 900-1200 A thick and 380-520 A thin knobby cords, which were randomly coiled. Subsequent treatment with DTT resulted in the dissociation of the 380-520 A cords into subunits of 180-210 A fibers, which were further decondensed into beads-on-a-string structure with diameter of the beads about 120-150 A.

Importance of zinc for human sperm head-tail connection

Head-tail detachment of ejaculated human spermatozoa was studied with phase contrast microscopy. The frequency of head-tail detachment was assessed after sperm exposure to the anionic detergent sodium dodecyl sulfate (SDS) for 60 min at 22 degrees C. Decapitation was enhanced by EDTA. Zinc reversibly inhibited native as well as EDTA induced head-tail disconnection. Still a certain proportion of spermatozoa were resistant to EDTA-treatment and this proportion significantly increased upon 24 h of saline storage. The development of EDTA resistance was enhanced by EDTA treatment before storage. A physiological role for zinc as a preserver of an inherent mechanism for head-tail detachment is suggested.

Sperm head morphology of the plains mouse Pseudomys australis

Spermatozoa of plains mice were studied by transmission and scanning electron microscopy. The occurrence of a distinct dorsal hook and 2 ventral hooks joined at the base was confirmed. Acrosomal material covered the dorsal hook and appeared to constitute most of the 2 ventral hooks which contained nuclear material only at the base. Incubation in sodium dodecyl sulphate resulted in loss of all the material presumed to be acrosomal.

A comparison of the molecular action of an SN1-type methylating agent, methyl nitrosourea and an SN2-type methylating agent, methyl methanesulfonate, in the germ cells of male mice

A study has been made of the unscheduled DNA synthesis (UDS) induced in early spermatid stages of the mouse by methyl nitrosourea (MNU), a methylating agent that reacts predominantly by an SN1 type mechanism. In comparison with methyl methanesulfonate (MMS), a methylating agent that reacts predominantly by an SN2 mechanism, MNU induced more UDS by a factor of about 1.4. This result was in line with chemical dosimetry studies carrie out with both chemicals, which showed that 4 h after treatment with MNU, testicular DNA was methylated about 1.5 times more than it was 4 h after treatment with MMS. The UDS response in the spermatids fell off rapidly in the first half-day after treatment with either MNU or MMS. However, from 0.5 to 3 days after treatment the UDS response decreased with a t1/2 of 2.4 days after MNU treatment, but 1.2 days after MMS treatment. Chemical dosimetry studies with 3H-labeled MNU and MMS showed that the pattern of methylation produced in the developing sperm was different for each chemical and was generally correlated with the corresponding pattern of induced dominant-lethal mutations. However, on the basis of equal sperm-head methylation, MNU is as much as 17 times more effective than MMS in producing dominant lethals. It is suggested that more methylation by MNU at the O-6 position of guanine or phosphate groups in DNA in the developing germ cells may account for MNU's greater effectiveness in inducing dominant lethals. Greater methylation of these sites by MNU than by MMS might also account for the differences observed in the UDS response of the spermatids to these chemicals.

In vitro decondensation of human sperm chromatin

The swelling of human sperm head and the decondensation of the sperm chromatin were investigated using a microscopic observation and the increased binding of AMD as the probes. Incubation of the human spermatozoa with 1 mM DTT produced sperm head swelling within 30 min. Addition of soybean trypsin inhibitor or PMSF blocked the swelling induced by 1 mM DTT. The DTT induced a large increase in the binding of AMD to the spermatozoa, to the sperm head and to the triton X-100 treated spermatozoa. This increase in AMD binding was completely abolished by the presence of PMSF. These results suggested the participation of a sulfhydryl reducing agent and a proteolytic enzyme in the sperm head swelling and the chromatin decondensation. The simplicity of probing the chromatin decondensation with AMD binding offers a means to study kinetic and quantitative aspects of the process.

Do induced sperm-head abnormalities in mice specifically identify mammalian mutagens rather than carcinogens?

The results of testing 54 compounds including 19 carcinogen/non-carcinogen pairs from a wide range of chemical classes are reported. Many carcinogens did not induce increases in abnormal sperm heads. In contrast compounds known to induce transmissible genetic damage in whole animals invariably induced dose-dependent large increases in the incidence of abnormal sperm heads. The test may be useful in assisting discrimination between compounds that only cause mutations in isolated cell systems from those which constitute a real genetic hazard for whole mammals.

Deformities in the head region of late spermatids of hypophysectomized-hormone-treated rats

Testosterone capsules implanted in hypophysectomized rats prevented tubulobulbar complexes from forming in many late spermatids. These spermatids also displayed an accumulation of cytoplasm (swelling) in the perinuclear region of the head. Other spermatids with normal or near-normal numbers of tubulobulbar complexes showed a typical perinuclear space. The results indicate, but do not prove, that development of tubulobulbar complexes (and their subsequent phagocytosis) is essential for the normal elimination of cytoplasm that takes place prior to sperm release.

The detection of carcinogen-induced sperm head abnormalities in mice

The (CBA X BALB/c(F1 male mouse is sensitive to the induction of sperm-head abnormalities after exposure to a range of chemical mutagens and carcinogens. 8 carcinogens including ethionine and diethyl stilboestrol were correctly identified. 23 non-carcinogens and compounds of unknown carcinogenicity including a range of 13 substituted anilines and methionine did not induce sperm-head abnormalities. 4-Aminophenol induced an increase in sperm-head abnormalities. The utility of the procedure for identifying genotoxic compounds is discussed.

Changes in mammalian sperm morphology after X-ray and chemical exposures

Sperm head morphology in mammals provides a unique approach to quantiating the effects of environmental agents on the germ cells. In unperturbed male mice, the sperm of each genotype can be reproducibly characterized by the shape of the head, the overall percent of sperm with head-shape abnormalities and the types of shape abnormalities seen. Genetic studies show that sperm shape is highly heritable, and that the fraction of abnormal sperm is controlled by a multitude of autosomal factors plus probably involvement of the sex chromosomes.--Exposure to ionizing radiation or certain chemical agents in vivo leads to dosage-dependent increase in the fraction of sperm with head-shape abnormalities. These results are documented in numerous mammalian species, including man. Evidence from mouse studies suggests that in general sperm shape is affected by those agents considered to be mutagenic. Since sperm samples are easily obtained and sperm morphology is rapidly quantitated, these observations suggest that sperm morphology in the mouse may be an applicable screen for environmental effects on germ cells. Changes in sperm are also seen in the offspring of male mice exposed to irradiation or a chemical alkylating agent. Preliminary evidence suggests that these changes represent heritable sperm shape abnormalities that can be further transmitted to subsequent generations.--The problems of determining the genetic implications of induced sperm abnormalities in exposed males are discussed. It is suggested that sperm morphology testing may have a direct application in man.

Effects of cannabinoids on sperm morphology

Sperm morphology was studied in hybrid mice of genotype (C57BL X C3H)F1 following treatment with specific cannabinoids. Mice were treated for 5 consecutive days with the specific cannabinoid; 35 days after the last treatment, epididymal sperm were scored in the light microscope and assessed in the scanning electron microscope. The animals treated with delta9-tetrahydrocannabinol (delta9-THC) and cannabinol (CBN) had a statistically higher incidence of abnormal sperm than the controls. The incidence of abnormal sperm in the animals treated with cannabidiol (CBD) was not statistically different from the control value. The relative toxicity of the cannabinoids in these studies was delta9-THC greater than CBN greater than CBD. Normal sperm have a smooth kidney-shaped head with a prominent hook; abnormal sperm have shapes which include heads without hooks, banana-shaped heads, amorphous heads and folded heads.