Induction of DNA damage by urethane in mouse testes: DNA binding and unscheduled DNA synthesis

The extent and persistence of DMA damage and repair were investigated in mouse spermatogenic cells exposed in vivo to urethane (ethyl carbamate, EC). Adult male mice exposed to [³H]EC at 10–1,000 mg/kg were sacrificed 12 hr later. EC/metabolite binding to liver and testicular DNA and to sperm heads from the vasa deferentia was measured. Other male mice were exposed to EC at 50–750 mg/kg, and unscheduled DNA synthesis (UDS) induction was investigated in early spermatid stages. Similar experiments were conducted with vinyl carbamate (VC; putative EC metabolite) at 10–75 mg/kg. [³H]EC bound to liver and testicular DNA and to whole sperm heads. Testicular DNA binding increased linearly with dose, although binding was at least 2 orders of magnitude lower than with liver DNA. Sperm head binding also increased linearly with dose. Dose response studies with the UDS assay showed that EC and VC induced a small but significant increase of the UDS response in early spermatid stages. However, the induced UDS responses were quite variable and did not consistently increase with the administered dose. To determine the time kinetics of UDS induction, [³H]dThd was injected at various times after treatment with 500 mg/kg of EC or 60 mg/kg of VC. A slight but significant UDS increase was observed 4 hr after treatment with EC but not with VC. Overall, these results suggest that EC metabolites bind to testis DNA and cause low-level DNA damage in mouse sper-matogenic cells. This type of DNA damage apparently does not have significant genetic consequences. © 1994 Wiley-Liss, Inc.     

Use of seminiferous tubule segments to study stage specificity of unscheduled DNA synthesis in rat spermatogenic cells

DNA repair in spermatogenic cells at various stages of maturity was determined by quantitation of unscheduled DNA synthesis (UDS). Male F-344 rats were exposed (i.p.) to methyl methanesulfonate (MMS, 35 mg/kg); 1 hr later, segments of seminiferous tubules corresponding to spermatogenesis stages II, IV-V, VI, VII, VIII, IX-X, XII, and XIV were isolated with the transillumination pattern of the tubules as a guide. Intact tubule segments were cultured 24 hr in the presence of [3H]thymidine, and UDS was quantitated by autoradiography as net grains/nucleus (NG). In primary spermatocytes from treated rats, NG count increased with increasing maturity from leptotene primary spermatocytes (3.5 NG) up through stage VIII and IX-X pachytene spermatocytes (22 NG), after which NG decreased in stage-XII pachytene and diplotene spermatocytes (to 16 NG and 8 NG, respectively). Round spermatids of steps 2-8 of spermiogenesis all exhibited approximately the same UDS response (8 NG). Elongating spermatids as mature as step 14 underwent UDS after exposure to MMS, but step-15 and later-step spermatids did not. The DNA repair response of pachytene spermatocytes cultured within segments of seminiferous tubule corresponding to stages VIII and IX-X was 4 to 25 times greater, depending on the dose of MMS, than pachytene spermatocytes isolated by enzymatic digestion and cultured in suspension [Bentley and Working, Mutat Res 203:135-142, 1988]. Thus, the use of segments of seminiferous tubule both increased the sensitivity of UDS as an indicator of DNA damage in rat germ cells and enabled the study of UDS in spermatogenic cells at different stages of maturity.     

Effect of mode of administration of methyl methanesulfonate and triethylenemelamine on induction of unscheduled DNA synthesis in mouse germ cells

The effect of route of administration on induction of unscheduled DNA synthesis (UDS) in mouse germ cells in vivo was studied using two germ cell mutagens, methyl methanesulfonate (MMS) and triethylenemelamine (TEM). The chemicals were administered to male mice (C3Hf X 101)F1 by IP injection or gavage using acute or 5-day subacute regimens. After completion of dosing, methyl-[3H]thymidine [( 3H]TdR) was injected into the testes, and spermatozoa were collected 16 days later. The sperm heads were isolated, and UDS was determined by the amount of [3H]TdR incorporated. Acute administration of MMS (2-100 mg/kg) induced a strong, dose-related UDS response. The response was slightly higher with IP injection than with gavage. The UDS response after five daily doses of 50 mg MMS/kg was 20-30% higher than that induced by a single IP or gavage dose. Acute administration of TEM (0.05-4.0 mg/kg) by IP injection or gavage induced weak and variable responses. Retesting TEM using inbred C3Hf mice produced weak but exposure-related responses with both acute IP and gavage treatments. There was a slight increase in UDS response with subacute IP injection but not with subacute gavage. Acute testicular injection of TEM produced a higher but more variable UDS response. The study showed that gavage, as well as IP injection, can be used for the administration of test chemicals and that the subacute 5-day regimen induced a higher UDS response than the acute regimen. Furthermore, the testicular route may enhance the detection of weak UDS inducers.     

Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. I. Target cells and possible mode of action

The effect of dextran sulfate on [³H]dThd incorporation in lymphoid cells was investigated. The polyanion activated DNA synthesis in spleen and bone marrow cells of normal mice. The highest rate of activation was detected in spleen cells of athymic (nude) mice; the ratio of [³H]dThd incorporation was higher in TxBM spleen cells of thymectomized, lethally irradiated and bone marrow protected mice than in spleen cells of normal donors. Thymus cells of normal mice could not be stimulated, but a slight response was obtained in cortisone-resistant thymus cells. A synergetic effect was found in normal thymus cells using a combination of dextran sulfate and phytohemagglutinin (PHA). In contrast, lipopolysaccharide and PHA showed no synergetic effect. The possible mode of action of polyanions as de-repressors of DNA synthesis is discussed.     

The effect of 5-fluorouracil on [3H]nucleoside incorporation into the DNA of mouse embryos and maternal tissues

Pregnant albino mice (ICR) were administered, ip, 40 mg/kg 5-fluorouracil (5-FU) on Day 10 of gestation. This dosage produced 96.3% embryolethality and 100% of the surviving fetuses were malformed. This dosage also produced a pronounced inhibition of 6-[³H]dUrd incorporation into the DNA of the embryo, chorioallantoic placenta, maternal intestine, and maternal spleen. There was no recovery in the embryo or placenta over the 48 hr time period analyzed. In the maternal tissues, however, incorporation levels returned to control values by 48 hr after 5-FU administration. 5-FU had no effect on 6-[³H]dThd incorporation into the DNA of any of the mitotically active tissues with the exception of the embryo at the 48 hr time point. Concomitant histological studies of the embryo neural tube showed that 40 mg/kg 5-FU produced mitotic inhibition 2 hr after treatment. Cell death began at 4 hr with heteropycnosis in the DNA synthetic zone of the primitive ependymal layer. As with the incorporation experiment, there was no histological recovery in the neural epithelium and the pycnosis became progressively more severe with time after 5-FU treatment.     

Radiosensitivity of T and B lymphocytes. II. Effect of irradiation on response of T cells to alloantigens

The radiosensitivity of T cells was investigated by studying the effect of irradiation in vitro in suppressing the capacity of parental strain thoracic duct lymphocytes (a) to induce splenomegaly in newborn F₁ mice, and (b) to proliferate in adult irradiated F₁ mice as measured by incorporation of tritiated thymidine ([³H]dThd) 4 days after transfer. By these parameters, small T lymphocytes were found to be highly radiosensitive. It was calculated that, of cells with the reactivity to the alloantigens studied, 0.3 % were capable of a proliferative response after exposure to 500 r. Radiosensitivity was considered to be a reflection of lymphocyte death in interphase. The radiosensitivity of H-2-activated T cells (T. TDL) differed from that of small T cells. Thus, [³H]dThd incorporation by T. TDL measured 1 day after transfer to irradiated F₁ hosts was not abolished, although lowered, by exposure to doses as high as 5000 r; [³H]dThd incorporation measured at 2 days, however, was greatly reduced by much smaller doses of irradiation. In view of evidence obtained elsewhere that the response of T. TDL to alloantigens involves DNA synthesis but not cell division, the present studies were interpreted in terms of irradiation causing death of T. TDL in interphase before entry into DNA synthesis. It was concluded that T. TDL were far more resistant to irradiation-induced interphase death than were small T cells. The small numbers of lymphocytes obtained from thoracic duct lymph of mice exposed to whole body irradiation 4 days before consisted almost entirely of T cells; these cells, although viable, were found incapable of mounting a proliferate response when exposed to alloantigens on transfer.     

Abilities of wild-type and thymidine kinase-deficient Friend mouse erythroleukemia cells to undergo unscheduled DNA synthesis following mutagen treatment

The abilities of wild-type and thymidine kinase-deficient Friend mouse erythroleukemia cells to perform unscheduled DNA synthesis (UDS), through the incorporation of [³H]deoxycytidine, were measured following damage with methyl methane sulfonate (MMS), ethyl methane sulfonate (EMS), and ultraviolet (UV) irradiation. For each mutagenic treatment, a positive and quantitatively similar response was observed for both wild-type and thymidine kinase-deficient cells. The extent of the response varied greatly, however, depending upon the mutagen used. The results contrast with the unscheduled incorporation of [³H] thymidine in wild-type cells following mutagen treatment, where less variation between the positive UDS responses elicited by MMS, EMS, and UV treatments was observed. Nevertheless, the results clearly indicate that thymidine kinase deficiency does not prevent excision repair (UDS) from occurring.     

Effect of estrogen and corticosterone on the lymphoid system in neonatal mice

Neonatal female NMRI mice were injected with varying doses of estradiol-17β (E₂), diethylstilbestrol (DES), or corticosterone (CC). All three substances reduced the body weight and the weight of thymus and spleen. On a dose level, DES was more potent than E₂ or CC. DES treatment resulted in pronounced degeneration in thymus cortex, reduced incorporation of [³H]thymidine in thymus and spleen, reduced mitotic rate in thymus, and reduced number of leukocytes in peripheral blood with a decreased percentage of mononuclear cells. Nine-week-old animals, injected with DES neonatally, had persistent changes in their peripheral leukocyte population. Cytosol fraction of thymus and spleen from 4- to 5-day-old females contained a DES and E₂-binding macromolecule with a sedimentation coefficient of approximately 4.5S and binding characteristics similar to α-fetoprotein. Autoradiograms of thymus after an [³H]DES injection did not show any labeling of thymocytes. The concentration of radioactivity in thymus and spleen after a single [³H]DES injection was very low and constant from 10 min to 4 hr after the injection, while a pronounced radioactivity occurred in uterus and skeletal muscle. A model is discussed for the estrogen effect on the lymphoid tissue in neonatal mice. The results underline the importance of studying the immune system in offspring of women treated with DES during pregnancy.     

Comparative Studies on the Effects of Specific Immunoneutralization of Endogenous FSH or LH on Testicular Germ Cell Transformations in the Adult Bonnet Monkey (Macaca radiata)

PROBLEM : It is yet to be determined clearly whether the two hormones FSH and T act synergistically in the same cell type—the Sertoli cells—to control overall spermatogenesis or influence independently the transformation of specific germ cell types during spermatogenesis in the adult mammal. METHOD : Adult male bonnet monkeys specifically deprived of either FSH or LH using immunoneutralization techniques were monitored for changes in testicular germ cell transformation by DNA flow cytometry. RESULTS : FSH deprivation caused a significant reduction (>40%; P < 0.05) in [³H] thymidine incorporation into DNA of proliferating 2C (spermatogonial) cells, a marked inhibition (>50%) in the transformation of 2C to primary spermatocytes (4C) and a concomitant, belated reduction (50%) in the formation of round spermatids (1C). In contrast, specific LH/T deprivation led to an immediate arrest in the meiotic transformation of 4C to 1C/HC leading to an effective and significant block (<90%; P < 0.01) in sperm production. CONCLUSION : Thus, LH rather than FSH deprivation has a more pronounced and immediate effect as the former primarily blocks meiosis (4C → 1C/HC) which controls production of spermatids. These data provide evidence for LH/T and FSH regulating spermatogenic process in the adult primate by primarily acting at specific germ cell transformation steps.     

The effect of colchicine and colcemid on the mitogeninduced blastogenesis of lymphocytes

The effect of colchicine and colcemid (1 × 10^?6 M) on the blastogenic response of human lymphocytes to concanavalin A was studied in vitro by three different methods. (a) Measurement of [³H]thymidine ([³H]dThd) incorporation which was strongly suppressed by the drugs. (b) Volume spectroscopy showing that the growth of cellular and nuclear volume was only moderately affected by the drugs during the first two days of culture: in drug-treated cultures, 25% of the cells responded by measureable growth of their nuclear volume as compared to 30% in untreated cultures. After two days, however, growth stagnated in drug-treated cultures, and cell division never occurred. (c) Flow cytofluorometry, showing that in drug-treated cultures the number of cells measurably increasing their DNA content, i.e. entering S-phase, was about 60% of that in untreated cultures. However, the drugs caused a majority of the responding cells to stop DNA synthesis before completing S-phase. This effect could not fully account for the strong suppression of the [³H]dThd incorporation indicating that colchicine and colcemid caused a malfunction of the [³H]dThd assay. It is concluded that colchicine and colcemid do not significantly inhibit initiation of a blastogenic response indicating that microtubuli, which are known to be affected by these drugs, are not essential for the triggering of blastogenesis.     

Differential sensitivities of spermatogonial and postspermatogonial cell stages of the mouse to induction of unscheduled DNA synthesis by ethyl- and methyl-nitrosourea.

An autoradiographic procedure was used to measure unscheduled DNA synthesis (UDS, DNA repair synthesis) in spermatogonial and postspermatogonial cell stages of mice after treatment with two doses of N-ethyl-N-nitrosourea (ENU) and N-methyl-N-nitrosourea (MNU). Significant levels of UDS were measured in type A spermatogonia, meiotic spermatocytes, round spermatids, and early elongating spermatids but not in mature spermatids. The extent of UDS varied according to the germ cell stage and the dose. At equimolar concentrations, MNU was more efficient than ENU in eliciting a UDS response in all germ cells. After ENU treatment, type A spermatogonia showed the highest UDS response, while round and elongating spermatids showed the lowest. After MNU treatment, pachytene spermatocytes exhibited the highest UDS response while type A spermatogonia showed the lowest. The high UDS response of type A spermatogonia to ENU parallels the well-known high mutational sensitivity of spermatogonia to this chemical. Similarly, the high UDS response observed in meiotic spermatocytes and early spermatid stages after MNU treatment correlates with the high mutational sensitivity of postspermatogonial stages to MNU. Thus, the present results, like the specific locus mutation studies, indicate that ENU and MNU each has a unique effect on the spermatogenic cells. This effect is likely due to the different mechanism of action of ENU and MNU at the level of DNA and also to the physiological differences between different germ-cell stages. Teratogenesis Carcinog. Mutagen. 19:339-351, 1999. Published 1999 Wiley-Liss, Inc.     

Initiation of the blastogenic response of lymphocytes by hyperoptimal concentrations of concanavalin A.

The blastogenic response of human lymphocytes in vitro to hyperoptimal concentrations of concanavalin A (Con A) has been studied by means of volume spectroscopy (measuring cellular and nuclear volume), flow cytofluorometry (measuring cellular DNA content) and incorporation of [3H]thymidine ([3H]dThd). The optimal Con A dose with respect to [3H]dThd incorporation was about 30 micrograms/ml. In cultures given hyperoptimal doses, e.g. 100 micrograms/ml, [3H]dThd incorporation was strongly inhibited, whereas the number of cells entering S-phase and significantly increasing their cellular and nuclear volume was considerably larger than with 30 micrograms/ml. With 200 micrograms/ml Con A, which induced negligible [3H]dThd incorporation, the percentage of responding cells was even larger. Hence, doses of Con A, which were hyperoptimal with regard to [3H]dThd incorporation, induced blastogenic response, including DNA synthesis, in a larger percentage of the cells than did the optimal dose. However, in cultures with hyperoptimal Con A doses, the progression of the cell cycle stagnated mainly during S- and G2-phase and few cells completed mitosis. Thus, the blocking effect of hyperoptimal doses was not confined to any particular point of the cell cycle. The reduced [3H]dTd incorporation, seen with hyperoptimal doses, is attributed partly to a failure of this assay under such conditions.     

Unscheduled DNA synthesis in various types of cells of the mouse brain in vivo

Summary Very low incorporation of ³H-thymidine (TdR) into neurons and non-proliferating glial and endothelial cells in various brain areas of the adult mouse after ³H-TdR injection and subsequent X-irradiation of the head with 45 Gy has been demonstrated autoradiographically after exposure times of 250 days. In accordance with biochemical studies this incorporation of ³H-TdR represents DNA repair synthesis or UDS (unscheduled DNA synthesis). However, ³H-TdR incorporation into nuclear DNA of non-proliferating cells in the brain was not only found in X-irradiated but also in sham-irradiated mice. This suggests that spontaneous UDS also occurs. Up to now spontaneous UDS has been shown only in HeLa cells in vitro. Nearly all the various types of brain cells tested exhibited UDS after X-irradiation as well as spontaneous UDS. After correcting the mean grain numbers per nucleus not only for background but also for -self-absorption, substantial differences became apparent in the extent of UDS between the individual types of cells. After X-irradiation, UDS was highest in Purkinje cells and hippocampal granular cells but comparable UDS was also found in endothelial cells, regardless of the different brain areas studied. The extent of spontaneous UDS is also quite different in the various cell types, being highest in neurons of different sites and considerably lower in endothelial and glial cells.     

DNA adduct kinetics in reproductive tissues of DNA repair proficient and deficient male mice after oral exposure to benzo(a)pyrene

Benzo(a)pyrene (B[a]P) can induce somatic mutations, whereas its potential to induce germ cell mutations is unclear. There is circumstantial evidence that paternal exposure to B[a]P can result in germ cell mutations. Since DNA adducts are thought to be a prerequisite for B[a]P induced mutations, we studied DNA adduct kinetics by ³²P‐postlabeling in sperm, testes and lung tissues of male mice after a single exposure to B[a]P (13 mg/kg bw, by gavage). To investigate DNA adduct formation at different stages of spermatogenesis, mice were sacrificed at Day 1, 4, 7, 10, 14, 21, 32, and 42 after exposure. In addition, DNA repair deficient (Xpc^?/?) mice were used to study the contribution of nucleotide excision repair in DNA damage removal. DNA adducts were detectable with highest levels in lung followed by sperm and testis. Maximum adduct levels in the lung and testis were observed at Day 1 after exposure, while adduct levels in sperm reached maximum levels at ～1 week after exposure. Lung tissue and testis of Xpc^?/? mice contained significantly higher DNA adduct levels compared to wild type (Wt) mice over the entire 42 day observation period (P < 0.05). Differences in adduct half‐life between Xpc^?/? and Wt mice were only observed in testis. In sperm, DNA adduct levels were significantly higher in Xpc^?/? mice than in Wt mice only at Day 42 after exposure (P = 0.01). These results indicate that spermatogonia and testes are susceptible for the induction of DNA damage and rely on nucleotide excision repair for maintaining their genetic integrity. Environ. Mol. Mutagen. 2010. © 2009 Wiley‐Liss, Inc.     

Partial pronase digestion of rat gastric mucosa isolates cells undergoing replicative DNA synthesis

A pronase digestion procedure for the isolation of gastric mucosal cells was evaluated for its usefulness in measuring unscheduled DNA synthesis (UDS). The method has been claimed to be suited for assessing the genotoxicity potential of compounds. Compounds were given orally to rats. After 13 h [3H]thymidine was injected and after another hour the animals were killed. The dissected stomachs were treated with pronase for 45 min and the incorporation of radioactivity into DNA was determined. Autoradiography was also performed both on the mucosa and on the isolated cell suspension. The cell suspensions were found to include cells undergoing normal replicative (S phase) DNA synthesis. Of all cells isolated, 4.8 +/- 0.6% consisted of S phase cells. The total amount of DNA recovered (corresponding to the number of cells isolated) was variable and ranged from 20 to 671 micrograms DNA, i.e. approximately 30-fold variation. Neither omeprazole (10, 30 and 80 mg/kg) nor ranitidine (215 mg/kg) had any effect on [3H]thymidine incorporation. The known carcinogen 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) increased incorporation. Refeeding of fasted animals increased incorporation of [3H]thymidine almost 4-fold, showing that animal feeding status influences incorporation. Hydroxyurea, the selective inhibitor of S phase DNA synthesis, inhibited [3H]thymidine incorporation in control and omeprazole-treated animals as well as that induced by MNNG by 92-98%. The results clearly show that the pronase digestion procedure used releases cells undergoing normal, replicative DNA synthesis and can therefore neither be used for measurements of UDS nor for the assessment of the genotoxic potential of drugs.     

Evidence that the [3H]thymidine-induced adaptive response of human lymphocytes to subsequent doses of X-rays involves the induction of a chromosomal repair mechanism

When human lymphocytes are treated with [³H]thymidine ([³H]dThd),the observed number of chromosomal aberrations induced by [³H]dThdand subsequent doses of X-rays is less than the number inducedby X-rays alone. Experiments in which cells were examined atvarious times after exposure to the X-rays showed that thisphenomenon, termed an adaptive response to the endogenous radiationfrom tritium, is not an artefact caused by radiation-inducedmitotic delays, which could result in the sampling of metaphasecells that were irradiated in different parts of the G₂ phaseof the cell cycle, where sensitivity to X-rays changes dramatically.Reconstruction experiments in which labelled female cells wereco-cultured with unlabelled male cells now show that labelledand unlabelled cells progress to metaphase equally, and thereforethat the adaptive response is not the result of selection againsta radiosensitive population of cells that have incorporated[³H]dThd. Measurements of chromosomal aberrations induced inthe labelled female cells and unlabelled male cells that hadbeen co-cultured show that the adaptive response is restrictedto those cells exposed to radiation from the incorporation of[³H]dThd and that diffusible factors are not involved. The resultsare consistent with the proposal that this adaptive responseis the result of the induction of a hitherto unknown chromosomalrepair mechanism. It has now been found that this repair mechanismis induced at levels of radiation from [³H]dThd that in themselvesare too low to induce any discernible chromosomal aberrationsand that its activity is dependent on the enzyme poly(ADP-ribose)polymerase, because 3-aminobenzamide, an inhibitor of poly(ADP-ribosyl)ation,prevents the adaptive response. ¹To whom correspondence should be addressed     

Inhibition of [3H]thymidine incorporation by Mycoplasma arginini-infected cells due to enzymatic cleavage of the nucleoside

Culture supernatants contaminated by Mycoplasma arginini inhibit the incorporation of [3H]thymidine ([3H]dThd) by cytotoxic T lymphocyte cell lines. This study presents evidence that the inhibition of uptake of the nucleoside is due to the rapid cleavage of the exogenous [3H]dThd into thymine. Uridine and cytidine as well as dThd are degraded by the mycoplasma-contaminated supernatants, while no cleavage was observed with uninfected supernatants. Cells contaminated by mycoplasma apparently release a pyrimidine-specific nucleosidase, possibly a dThd phosphorylase, which is responsible for the inhibition.     

An assay to detect chemically induced DNA repair in rat spermatocytes

An in vivo/in vitro DNA repair assay has been developed to quantitate chemically induced unscheduled DNA synthesis (UDS) in rat spermatocytes utilizing autoradiography. Male Fischer-344 rats were treated by i.p. injection or gavage with a variety of genotoxic agents dissolved in dimethyl sulfoxide, corn oil, or water. At selected times after treatment, spermatocytes were isolated by trypsin digestion of testes and cultured for 24 hr in the presence of ³H-thymidine. The direct-acting genotoxicants methyl methanesulfonate (MMS) and ethyl methanesulfonate and the chemotherapeutic agent cyclophosphamide (CPA) produced positive UDS responses in spermatocytes isolated 1 hr after i.p. injection. The UDS response evoked by either CPA or MMS was maximal within 1 hr after injection and declined rapidly thereafter to control levels. Other known genotoxicants—including dimethylnitrosamine, aflatoxin B₁, 2-acetylaminofluorene, 2,6-dinitrotoluene, and 1,6-dinitropyrene—failed to induce UDS, even with routes of administration and at times of exposure known to produce a positive response in hepatocytes. This negative response is consistent with these genotoxicants lack of mutagenic effect in rodent germ cells. These results demonstrate that the in vivo/in vitro spermatocyte DNA repair assay may be useful as a predictive screen for germ cell mutagens. Moreover, by its compatibility with similar assays which utilize other tissues from the same treated animal, this assay permits assessment of the organ specificity of the genotoxic response.     

Chromosome aberrations and spermatogenic disorders in mice with Robertsonian translocation (11; 13)

Objective: To determine the diagnostic features of Robertsonian (Rob) translocation (11; 13) in mice and the mechanisms underlying the effect on spermatogenesis and reproductive decline. Methods: A Rob translocation (11; 13) mouse model was established by cross-breeding, and confirmed by chromosome analysis. Chromosome aberrations and translocation patterns were identified in mice with Rob translocation (11; 13) by fluorescence in situ hybridization (FISH). Spermatogenic disorders were investigated at different stages of spermatogenesis. Immunofluorescent analysis was performed on sections of testis and epididymis specimens during spermatogenic meiosis. The weight of the testes and reproductive decline were recorded. Results: The crossed Rob translocation (11; 13) mouse has 39 chromosomes, including a fusion chromosome (included chromosomes 11 and 13) using dual color FISH. There was no difference in the distribution pattern of SYCP3 and γH2AX in spermatocytes between Rob translocation and wild-type mice; however, round haploid spermatids presented characteristic morphologic changes of apoptosis and the number of haploid spermatids was decreased. Furthermore, the immature germ cells were released into the epididymis and the number of mature sperm was reduced. Conclusions: Chromosome aberrations and spermatogenic disorders may result from apoptosis of round haploid spermatids and a reduced number of mature sperm in Rob translocation (11; 13) mice. Abnormal sperm and reduced number of sperm may be one of the main reasons for reproductive decline and male infertility in Rob translocation (11; 13) mice.     

Ontogeny of peroxidase activity in epithelium and eosinophils of the mouse uterus.

Outbred CD-1 mice treated for 1 or 4 days with 1 mg/kg of diethylstilbestrol (DES) at various ages after birth were examined for histochemical localization of peroxidase in the uterine epithelium. Peroxidase activity in uterine extracts was also measured by a radiometric assay and the conversion of [3H]DES to [3H]Z,Z-diensestrol (Z,Z-DIES). While no peroxidase activity was detected by a histochemical method in uterine epithelium from untreated 5-day old mice, the enzyme was apparent in mice treated for 4 days with DES; uterine eosinophils were absent at this age. By day 9, DES-induced staining for peroxidase in uterine epithelial cells and the number of uterine eosinophils had increased significantly. In addition, at this age, the biochemical assays for uterine peroxidase were sensitive enough to show that DES is converted to Z,Z-DIES and that [3H]estradiol gives rise to 3H2O and water-soluble radioactive metabolites. The peroxidase response to DES, determined by both histochemical and biochemical methods, increased with the age of the immature mice. These data indicate that the neonatal uterus, although deficient in eosinophils, demonstrates a peroxidase response to estrogen and that this response is localized primarily in the luminal epithelium. The role of this DES-induced peroxidase activity in converting DES to activated metabolites that may cause cell damage is discussed.