Fertilizability and chromosomal integrity of frozen-thawed Bryde's whale (Balaenoptera edeni) spermatozoa intracytoplasmically injected into mouse oocytes

Prior to attempting the in vitro production of embryos in the Bryde's whale (Balaenoputera edeni), we investigated whether spermatozoa can retain the capacity for oocyte activation and pronucleus formation as well as chromosomal integrity under cryopreservation by using intracytoplasmic sperm injection (ICSI) into mouse oocytes. Regardless of motility and viability, whale spermatozoa efficiently led to the activation of mouse oocytes (90.3-97.4%), and sperm nuclei successfully transformed into male pronucleus within activated ooplasm (87.2-93.6%). Chromosome analysis at the first cleavage metaphase (M) of the hybrid zygotes revealed that a majority (95.2%) of motile spermatozoa had the normal chromosome complement, while the percentage of chromosomal normality was significantly reduced to 63.5% in immotile spermatozoa and 50.0% in dead spermatozoa due to the increase in structural chromosome aberrations. This is the first report showing that motile Bryde's whale spermatozoa are competent to support embryonic development.

381 FERTILIZABILITY AND CHROMOSOMAL INTEGRITY OF FROZEN - THAWED BRYDE's WHALE (BALAENOPTERA EDENI) SPERMATOZOA INTRACYTOPLASMICALLY INJECTED INTO MOUSE OOCYTES

In this study, we applied intracytoplasmic sperm injection (ICSI) to mouse oocytes to evaluate the fertilizability and chromosomal integrity of the three types of frozen–thawed Bryde's whale spermatozoa. B6D2F1 female mice (7–11 weeks of age) were superovulated by injections of PMSG followed by hCG 48 h later. The oocytes recovered from oviducts between 14 and 16 h after hCG injection were denuded of their cumulus cells. Sperm samples were obtained from a Bryde's whale (Balaenoptera edeni) captured under the Japanese Whale Research Program with Special Permit in the Western North Pacific between May and August 2003 (presumptive feeding season). The whale was killed by an explosive harpoon which has been recognized as the best humane method for whales by the International Whaling Commission (IWC) and stipulated by Schedule III (Capture) of the International Convention for the Regulation of Whaling. Spermatozoa collected from vasa deferentia were cryopreserved. Frozen Bryde's whale spermatozoa were thawed at 37�C and washed with HEPES-TYH by centrifugation at 500g for 5 min. Motile and immotile spermatozoa were obtained, and some spermatozoa in HEPES-TYH were refrozen without cryoprotectant at -20�C to be completely killed. Within 24 h, they were thawed at 37�C and prepared for ICSI. Comparison of group values was performed by either Fisher's exact probability test or chi-square test where necessary. Differences at P d 0.05 were considered significant. Chromosomal normality was determined by analyses of karyotyped haploid chromosomes (n = 22) of the whale sperm. Regardless of motility and viability, whale spermatozoa efficiently led to the activation of mouse oocytes (90.3–97.4%), and sperm nuclei successfully transformed into male pronuclei within activated ooplasm (87.2–93.6%). Chromosome analysis at the first cleavage metaphase of the hybrid zygotes revealed that a majority (95.2%) of motile spermatozoa had the normal chromosome complement, whereas the percentage of chromosomal normality was significantly (P ≤ 0.001) reduced to 63.5% in immotile spermatozoa and 50.0% in dead spermatozoa, due to the increase in structural chromosome aberrations such as chromosome fragments. This is the first report showing that motile Bryde's whale spermatozoa are competent to support embryonic development. Furthermore, we have shown that chromosomal analysis of whale spermatozoa is a useful technique for measuring the influences of marine pollution on reproduction in cetacean species that occupy the top niche in the marine ecosystem.

Sperm chromosome study of two bulls heterozygous for different Robertsonian translocations

Haploid chromosomes of a total of 354 spermatozoa from two bulls heterozygous for different Robertsonian translocations, a Holstein-Friesian bull carrying a t(1;21) and a Japanese Black bull carrying a t(7;21), were analyzed using an interspecific in vitro fertilization system with zona-free hamster oocytes. The proportion of chromosomally normal and balanced spermatozoa was approximately equal in both carriers (51.8% and 47.0% in the 1/21 carrier, and 47.3% and 50.0% in the 7/21 carrier). The combined incidences of normal and balanced spermatozoa, i.e., incidences of spermatozoa resulting from alternate meiotic segregation were very high (98.8% and 97.3%) in both carrier. On the contrary, the incidences of chromosomally unbalanced spermatozoa resulting from adjacent meiotic segregation were only 0.6% and 2.7%. These results indicate that the alternate segregation of a trivalent chromosome is predominant in these Robertsonian translocation carriers.

A cytogenetic study of in-vitro matured murine oocytes after ICSI by human sperm

BACKGROUND

The purpose of this study was to investigate the chromosomal complement and developmental potential of in-vitro matured murine oocytes following ICSI by human sperm.

METHODS

Heterologous ICSI fertilization between mouse oocytes and human sperm was employed in order to overcome the reduced fertilization rates observed after conventional IVF due to zona hardening during in-vitro maturation, and to assess separately maternal and paternal chromosome complements. Cytogenetic analyses were performed in four types of oocytes: (i) in-vitro matured metaphase II (MII) oocytes; (ii) in-vivo matured MII oocytes; (iii) in-vitro matured oocytes after ICSI; (iv) in-vivo matured oocytes after ICSI.

RESULTS

Activation rates after ICSI of in-vitro matured oocytes was lower than that of in-vivo matured oocytes (69.9 versus 97.2%, P < 0.01), and premature chromosomal condensation was only observed in in-vitro matured oocytes. However, there were no significant differences in developmental rates after successful activation between in-vivo and in-vitro matured ICSI oocytes (69.7 versus 76.6%). The incidences of aneuploidy and structural aberrations were similar between the ICSI embryos and non-ICSI (MII) oocytes. Furthermore, the frequency of chromosomal aberrations was not associated with in-vitro or in-vivo maturation. Similar analyses of paternal chromosomes indicated that there were no significant differences in the incidence of chromosomal aberrations between the embryos derived from in-vitro and in-vivo matured oocytes.

CONCLUSIONS

These results suggest that in-vitro matured oocytes following ICSI do not lead to an increase in the frequency of aneuploidy and structural aberrations when human sperm are injected into mouse oocytes.

Meiotic stage-dependent induction of chromosome aberrations in Chinese hamster primary oocytes exposed to topoisomerase II inhibitor etoposide

To investigate the chromosomal effects of topoisomerase II (topo-II)-interactive drugs on mammalian primary oocytes, female Chinese hamsters were treated with etoposide (VP-16) at various intervals pre- and post-human chorionic gonadotropin (hCG) injections. Chromosome analysis of oocytes at metaphase II (M II) showed that treatment with VP-16 at 50h pre-hCG had no effect, but the treatments between 24h pre-hCG and 2h post-hCG often caused structural chromosome aberrations. Although treatment at 4h post-hCG had no effect, subsequent treatments at 6 and 8h post-hCG produced a significant increase in structural chromosome aberrations. No effect was found following treatment at 10h post-hCG. The incidence of aneuploidy following exposure to VP-16 was also dependent on the time of hCG injection. Taking the time course of meiotic progression in primary oocytes following hCG injection and pharmacokinetics of VP-16 into consideration, it is likely that meiotic stages from late dictyate to diakinesis are highly sensitive to VP-16, while stages at dictyate and from metaphase I (M I) to telophase I (telo I) are relatively insensitive to the drug. Moreover, the effect of VP-16 on structural chromosome aberrations and aneuploidy was dose-dependent. Chromosome analysis at M I detected a frequent occurrence of structural chromosome aberrations in treated oocytes. This suggests that structural aberrations may be caused by disruption of cleavable complexes during chromosome condensation. Detection of chromosome bridges during anaphase I/telophase I (ana I/telo I) may support the hypothesis that induction of aneuploidy by VP-16 is due to failure in decatenation of recombinant homologous chromosomes.

Chromosome analysis of human spermatozoa following in vitro exposure to cyclophosphamide, benzo(a)pyrene and N-nitrosodimethylamine in the presence of rat liver S9

For the purpose of assessing mutagenic effects (clastogenicity) of metabolites derived from chemical mutagens/carcinogens on human sperm chromosomes, spermatozoa were exposed in vitro to cyclophosphamide (CP), benzo(a)pyrene (BP) or N-nitrosodimethylamine (NDMA) for 2h in the presence or absence of rat liver S9, a metabolic activator of these chemicals. After in vitro fertilization between human spermatozoa and zona-free hamster oocytes, chromosome complements of sperm origin were analyzed cytogenetically. In the absence of S9, none of three chemicals (20 microg/ml CP, 200 microg/ml BP and 20mg/ml NDMA) caused a significant increase in spermatozoa with structural chromosome aberrations (8.6, 10.0 and 7.5%), as compared with their matched controls (10.9, 11.0 and 8.5%). In the presence of S9, however, a significant increase in chromosomally abnormal spermatozoa was observed in CP (37.1%, P < 0.001) and BP (31.0%, P < 0.001), indicating that enzymatic activation of CP and BP induced chromosomal abnormalities in human sperm. In contrast, NDMA did not induce chromosome aberrations in human spermatozoa by S9 treatment, although positive results have been observed in somatic cells. The present results on in vitro clastogenicity of CP, BP and NDMA are consistent with the results in previous in vivo studies with murine spermatozoa. Our S9/human sperm chromosome assay seems to be useful for estimation of hereditary risk of chemicals in human. Because most chemicals need metabolic activation to bind to DNA.

Dithiothreitol induces sperm nuclear decondensation and protects against chromosome damage during male pronuclear formation in hybrid zygotes between Chinese hamster spermatozoa and Syrian hamster oocytes

The present study was undertaken to investigate whether a time lag in sperm nuclear decondensation and male pronuclear formation in the course of development of eggs is associated with any occurrence of structural chromosome aberrations in male genomes of hybrid zygotes between Chinese hamster spermatozoa and zona-free Syrian hamster oocytes. Shortly after insemination, hybrid zygotes were treated with dithiothreitol (DTT) at different concentrations (0.1-10.0 mM) for 30 min to reduce protamine disulphide (S-S) bonds and thereby accelerate sperm nuclear decondensation and male pronuclear formation. The incidence of sperm nuclear decondensation and male pronuclear formation increased with increasing DTT concentrations, indicating that a reduction in S-S bonds effectively induces these cytological events. Chromosomes of male genomes in hybrid zygotes generated by treatment with 1.0 mM, 2.5 mM and 10.0 mM DTT were analysed at the first cleavage metaphase. Incidence of structural chromosome aberrations in each treatment was 34.5%, 27.1% and 24.7%, respectively. There was a significant difference between the incidences with 1.0 mM and 10.0 mM DTT treatment. As the time lag in nuclear decondensation and male pronuclear formation was greatest in the 1.0 mM treatment condition, followed in order by 2.5 mM and 10.0 mM, it is suggested that the lag in sperm nuclear development behind egg development is responsible for structural chromosome aberrations in male genomes of hybrid zygotes.

No induction of chromosome aberrations in human spermatozoa exposed to extremely low frequency electromagnetic fields

Clastogenic effects of extremely low frequency electromagnetic fields (ELF-EMFs) on human sperm chromosomes were studied using an interspecific in vitro fertilization system with zona-free golden hamster oocytes. Semen samples from healthy men were exposed to ELF-EMFs (50 Hz, 20 mT) for 2 h at 37 degreesC under 5% CO2 in air. The samples were then cryopreserved in liquid nitrogen for shipment to a cytogenetic laboratory. After thawing the samples, motile spermatozoa were collected using a continuous Percoll density gradient centrifugation and then capacitated for in vitro fertilization with hamster oocytes. Sperm-derived chromosomes were analyzed at first cleavage metaphase. The present experiment was performed twice using semen samples from two different donors. In test-1, incidence of spermatozoa that displayed structural chromosome aberrations was 17.0% (35/206) in the exposed group and 20.8% (55/264) in the control group. In test-2, structural chromosome aberrations were observed in 11.1% (13/117) of exposed spermatozoa and 13.8% (13/94) of spermatozoa in the control group. In both tests, there was no significant difference in the incidence of chromosomally abnormal spermatozoa between the exposed group and the control group. Types of aberrations observed and their incidences per spermatozoon in the exposed group were similar to those of the control group. Despite the small sample size, the present results suggest that ELF-EMFs have no clastogenic effect on human sperm chromosomes.

Parthenogenetic activation of Chinese hamster oocytes by chemical stimuli and its cytogenetic evaluation

This study was undertaken parthenogenetically to activate Chinese hamster oocytes in vitro by chemical stimuli. Oocytes were exposed to five different chemical agents, ethanol (EtOH), strontium chloride (SrCl2), cycloheximide (CHX), phorbol ester (PMA), and ionophore A23187 (IA23). No parthenogenetic activation was observed in the oocytes treated with 8% EtOH for 8-11 min, 1.7 mM and 5.0 mM SrCl2 for 1 hr, 100 microM and 400 microM CHX for 2 hr, and 81 nM and 162 nM PMA for 5 min. In contrast, 89.7% of oocytes parthenogenetically extruded the second polar body in treatment with 3 microM IA23 for 5 min, but only 22.6% of them formed a pronucleus and developed to 2-cell embryos. The remaining ova stopped their cell cycle immediately after completion of the second meiotic division. They had unichromatid chromosomes (monads), which are called MIII chromosomes. Treatment with 5 microM IA23 for 5 min was so deleterious that > 90% of oocytes were degenerated. However, oocyte activation was significantly improved when the treatment with 3 microM IA23 for 5 min was followed by treatment with 8% EtOH for 10 min, 100 microM CHX for 2 hr, 81 nM PMA for 5 min or 3 microM IA23 for 5 min: rates of pronuclear formation were 54.4%, 84.3%, 34.2%, and 54.6%, respectively. More than 80% of pronucleate ova successfully developed into 2-cell stage. Additive treatment with 5 mM SrCl2 for 1 hr had no positive effect on pronuclear formation. Incidences of aneuploidy (4.6%) and structural chromosome aberrations (1.0%) in parthenogenons produced by combined stimuli of IA23 and CHX were not significantly different from those (3.8% and 1.6%, respectively) in female pronuclei of ova fertilized in vitro, showing that combined treatments with IA23 and CHX cause neither nondisjunction at the second meiotic division nor structural aberrations in MII chromosomes. The present technique for parthenogenetic activation of Chinese hamster oocytes may be useful as an assessment system to detect aneugenic and clastogenic effects of mutagens on mammalian oocytes.

Analysis of chromosome constitution of human spermatozoa with normal and aberrant head morphologies after injection into mouse oocytes

The chromosome constitution of human spermatozoa was determined after injecting individual spermatozoa into mouse oocytes. Of a total 279 eggs arrested at first cleavage metaphase, 200 (71.7%) were suitable for the analysis of sperm chromosomes. Incidences of spermatozoa with numerical and structural chromosome aberrations were 1.3 and 6.9% respectively in spermatozoa with normal head morphology, showing values comparable with those found in previous studies using the hamster oocyte-human sperm fusion system. The ratio of X- to Y-bearing spermatozoa did not differ significantly from the expected 1:1 ratio. The incidence of structural chromosome aberrations was about four times higher in spermatozoa with amorphous, round and elongated heads (26.1%) than in those with morphologically normal heads, whereas the incidence of aneuploidy was not significantly different between the two groups. No increase in chromosome aberrations was found in spermatozoa with large heads. The same was true for spermatozoa with small heads. Although the sample size used in this study is rather small, the results nevertheless indicate that some morphological abnormalities in the sperm heads are associated with their chromosome defects.

Penetration of concanavalin-A-treated Chinese hamster oocytes by golden hamster spermatozoa in vitro, and chromosome analysis of hybrid 1-cell zygotes

Pretreatment of zona-free Chinese hamster (CH) oocytes with three kinds of lectin--concanavalin A (Con-A), phytohaemagglutinin-P (PHA) and wheat germ agglutinin (WGA)--was attempted in order to improve penetration by golden hamster (GH) spermatozoa in vitro. Con-A had no significant effect on penetration at 2 micrograms/ml, adequately facilitated oocyte-sperm fusion at 4 micrograms/ml, and caused excessive sperm binding and resultant severe polyspermy at 10 micrograms/ml. Neither PHA nor WGA had positive effects on sperm penetration at any concentrations (2-10 micrograms/ml) examined. Using the Con-A (4 micrograms/ml) pretreatment, high rates of interspecific fertilisation and subsequent chromosome analysis of hybrid 1-cell zygotes were achieved. Among 258 CH oocytes used, 212 (82.2%) were fertilised and 153 (72.2% of fertilised ova) developed to the first cleavage metaphase. Eventually, 132 CH-derived chromosome complements and 153 GH-derived ones were successfully karyoanalysed. Incidences of aneuploidy and structural anomaly were 3.1% and 2.3% in CH complements, and 1.4% and 6.5% in GH complements, respectively. These incidences were not significantly different from those obtained by intraspecific in vivo fertilisation, suggesting that our interspecific in vitro fertilisation system does not cause chromosome aberrations.

Relative biological effectiveness (RBE) of 252Cf fission neutrons for the induction of chromosome damage in human spermatozoa

Effects of 60Co gamma-rays and 252Cf neutrons on human sperm chromosomes were studied using our interspecific in vitro fertilization system to estimate relative biological effectiveness (RBE) of neutrons. Semen samples were exposed to 0.5, 1.0 and 2.0 Gy of 60Co gamma-rays at 1.7 cGy/ min and 0.25, 0.5 and 1.0 Gy of 252Cf radiation at 1.3-1.7 cGy/ min. In the 60Co experiment, 509 spermatozoa from controls and 902 spermatozoa from the irradiated groups were karyotyped, while in the 252Cf experiment 460 control and 804 irradiated spermatozoa were analysed. In both 60Co and 252Cf experiments, incidences of spermatozoa with radiation-induced structural chromosome aberrations increased linearly with increase of dosage. The RBE of 252Cf neutrons for the induction of chromosomally abnormal spermatozoa was estimated to be 1.6. The number of induced structural chromosome aberrations per spermatozoon also increased linearly. The RBE of neutrons for this index was 2.0. Among structural chromosome aberrations observed, chromosome-type breaks were predominant in both 60Co and 252Cf experiments, and they showed a significant linear dose-dependent increase. Other types of aberrations such as chromosome-type exchanges and chromatid-type breaks also increased linearly with increase in dose. The RBEs of 252Cf neutrons for the induction of these three types of aberrations were 1.6, 3.2 and 3.9, respectively. Thus, the RBEs of neutrons for the induction of chromosome aberrations were smaller in human spermatozoa than in human lymphocytes, and mouse spermatogonia and embryos. This result is discussed from the point of view of DNA-repairing capacity of oocytes.

In vitro fertilisation of Chinese hamster oocytes by spermatozoa that have undergone ionophore A23187-induced acrosome reaction, and their subsequent development into blastocysts

To enhance potential use of the Chinese hamster, Cricetulus griseus, in developmental and cytogenetic studies of mammalian gametes and embryos, techniques for in vitro fertilisation and embryo culture were developed in the species. Spermatozoa were recovered from the vasa deferentia of mature males, and incubated in modified TYH medium for 1 h at 37 degrees C under 5% CO2 in air. They were then treated with ionophore A23187 (20 microM) for 10 min to induce the acrosome reaction. Following ionophore treatment, superovulated oocytes were collected from hormonally stimulated females and incubated with the acrosome-reacted spermatozoa for 2 h at 37 degrees C under 5% CO2 in air. In this study, 245 oocytes were used for insemination, and 198 (80.8%) were found to be penetrated by sperm; among them, 194 ova (98.0%) were determined to be monospermic. The monospermic ova were then cultured in TYH supplemented with 1 mM hypotaurine under the same gas phase. Within 30 h of fertilisation, 182 ova (93.8%) cleaved to the 2-cell stage, and subsequently 163 ova (84.0%) developed beyond the 2-cell stage. Thus, obstinate developmental arrest at the 2-cell stage ('2-cell block') was not observed in this species. Ultimately, 65.5% of monospermic ova reached morula to blastocyst stages.

Difference in types of radiation-induced structural chromosome aberrations and their incidences between Chinese and Syrian hamster spermatozoa

The effects of ionizing radiations on sperm chromosomes were studied in the Chinese hamster (Crisetulus griseus) and the Syrian (golden) hamster (Mesocrisetus auratus). Testes of mature male Chinese hamsters (CH) were irradiated with X-rays (0.91, 1.82 and 3.63 Gy) and gamma-rays (1.10, 2.15, 2.95 and 4.01 Gy) at a single acute dosage, whereas the irradiation was done with lower doses of X-rays (0.45, 0.91 and 1.82 Gy) and gamma-rays (0.49, 0.99 and 1.98 Gy) in mature male Syrian hamsters (SH), taking the higher radiosensitivity of this species into consideration. They were mated with normal females within 6 days of exposure. Sperm-derived chromosomes were analyzed in 1125 and 1966 fertilized ova of the CH and the SH, respectively. In both species, there was no great difference in the induction of structural chromosome aberrations between X-irradiated and gamma-irradiated spermatozoa. Chromosome-type aberrations were predominantly induced. The incidence of breakage-type aberrations increased linearly, and that of exchange-type aberrations linear-quadratically with increase of dosage. A species-specific difference in chromosomal radiosensitivity of spermatozoa was clear. In spite of the same radiation dosage, the incidence of chromosomally abnormal spermatozoa in the SH was about twice as high as that in the CH (e.g. 27.0% vs. 14.7% at 0.91 Gy of X-rays). The incidences of breakage-type aberrations (69-89%) were far higher than those of exchange-type aberrations (11-31%) in the SH, while the disparity of the two incidences was much smaller in the CH (46-65% vs. 35-54%). Exchange-type aberrations consisted of both chromosome-type and chromatid-type in the SH, while almost all of them were of the chromosome-type in the CH. These results suggest that the DNA-repairing capacity of oocytes is much higher in the CH than in the SH. Moreover, it seems likely that radiation-induced sperm DNA damage is repaired with both pre-replication repair (excision repair) and post-replication repair systems in SH oocytes, whereas the excision repair system operate most exclusively in CH oocytes.

Induction of aneuploidy in Chinese hamster oocytes following in vivo treatments with trimethoxybenzoic compounds and their analogues

Many inhibitors of tubulin polymerization have a trimethoxybenzene ring in their molecules. Such trimethoxybenzoic compounds and their analogues may therefore have a potency to induce meiotic nondisjunction of oocytes. In this study, a single dose of reserpine (0.5 microgram/g body weight), podophyllotoxin (20.0 micrograms/g b.w.), trimethoxybenzoic acid (500.0 micrograms/g b.w.) or vinblastine sulfate (3.0 micrograms/g b.w.) was injected intraperitoneally to mature female Chinese hamsters at the onset of the first meiotic spindle formation of oocytes. Within 6 h after spontaneous ovulation, MII oocytes were collected from the oviducts for morphological examination and cytogenetic analysis. The incidence of morphologically abnormal oocytes with unusually large first polar body or bodies increased significantly after the treatment with reserpine (18/202; 8.9%), podophyllotoxin (28/172; 16.3%) and vinblastine sulfate (63/197; 32.0%), as compared with the control (3/214; 1.4%). Chromosome analysis of oocytes revealed that podophyllotoxin and vinblastine sulfate were effective in inducing aneuploidy (62/154; 40.3% and 128/156; 82.1% vs. 3/198; 1.5% of the control) by inhibiting the formation of spindle microtubules at the first meiosis. Aneuploids were found more frequently in morphologically abnormal oocytes than in normal oocytes. No aneugenic activity of reserpine and trimethoxybenzoic acid was observed. These results indicate that trimethoxybenzoic compounds do not necessarily exhibit aneugenic activity.

Chromosome analysis of human spermatozoa exposed to antineoplastic agents in vitro

We studied in vitro the cytogenetic effects of six antineoplastic agents, bleomycin (BM), cyclophosphamide (CP), daunomycin (DM), methyl methanesulfonate (MMS), mitomycin C (MMC) and triethylenemelamine (TEM) on spermatozoa, using an interspecific in vitro fertilization system between zona-free hamster oocytes and human or bull spermatozoa. In preliminary experiments with bull spermatozoa, clastogenic effects were clearly shown with BM, DM, MMS and TEM, but not with CP and MMC. In main experiments, the effects of the first four chemicals were studied in detail with human spermatozoa. Total numbers of 585 and 512 spermatozoa were karyotyped in the control and the chemical-treated groups respectively. The incidence of spermatozoa with structural chromosome aberrations was 34.5%, 53.0%, 59.3%, and 55.6% in the BM (50 micrograms/ml, 90 min), DM (0.1 microgram/ml, 90 min), MMS (100 micrograms/ml, 120 min) and TEM (0.1 micrograms/ml, 120 min) groups respectively, each showing a significantly higher incidence than the matched controls (10.1-13.5%). Breakage-type aberrations were more frequent than exchange-type aberrations in the BM, MMS and TEM groups, while the exchange-type aberrations were more frequent in the DM group. Exchanges were mainly of the chromatid type in the DM, MMS and TEM groups, while chromosome-type exchanges occurred more frequently in the BM group. These results are discussed in relation to previous data on chemical-induced chromosome aberrations in mammalian somatic cells and in mouse spermatozoa.

An Atypical Acidophil Cell Line Tumor Showing Focal Differentiation Toward Both Growth Hormone and Prolactin Cells

We report a case of giant pituitary adenoma in a child. Computerized tomography (CT) scan revealed a suprasellar extension tumor mass with hydrocephalus. There was no clinical evidence of acromegaly, gigantism, and other hormonal symptoms. Endocrinologic studies showed within normal value of serum growth hormone (GH: 4.2 ng/mL) and slightly increased levels of prolactin (PRL: 78 ng/mL) and other pituitary hormone values were within normal range. On suppression test by bromocryptin, both GH and PRL levels were reduced. Histopathological findings revealed that the tumor consisted of predominantly chromophobic and partly eosinophilic adenoma cells. Immunohistochemical staining detected GH and PRL in a small number of distinctly different adenoma cells, respectively. Nonradioactive in situ hybridization (ISH) also showed GH and PRL mRNA expression in identical immunopositive cells. Electron microscopy (EM) demonstrated adenoma cells with moderate or small numbers of two types of dense granules and without fibrous body which are characteristic of sparsely granulated GH-cell adenomas. The adenoma does not fit into any classification but may be an atypical acidophil cell line tumor showing focal differentiation toward both GH and PRL cells.

A chromosome painting method for human sperm chromosomes using fluorescent in situ hybridization

A method of chromosome painting on human sperm chromosomes using fluorescent in situ hybridization (FISH) is introduced. Sperm chromosome slides were prepared after in vitro fertilization of hamster eggs with human spermatozoa. The slides were treated by RNase A before FISH. Chromosome 4 was clearly and specifically painted in a majority of sperm-derived metaphase plates after an application of whole chromosome painting DNA probes of this chromosome. This is the first report of successful painting on human sperm chromosomes.

[A cytogenetic study of human oocytes unfertilized in in-vitro fertilization (IVF)]

A total of 260 unfertilized human oocytes obtained in our IVF program were studied cytogenetically, by a gradual fixation-air drying method proposed by Mikamo and Kamiguchi (1983). The oocytes were obtained from 72 cycles of 52 patients (mean age 32.1). Indications for these patients were 26 cases of tubal factor, 13 of male infertility, 2 of endometriosis and 11 of unexplained infertility. Ovulation induction was performed by hMG-hCG administration with GnRHa pretreatment. Of the 260 unfertilized oocytes, 183 displayed metaphase II and 149 were karyotyped accurately. There were 5 diploids (3.4%), 9 structural anomalies (6.0%) and 15 aneuploids (10.1%) including 8 hyperhaploids (5.4%) and 7 hypohaploids (4.7%). One hundred and twenty-two oocytes out of 149 (81.9%) were found to be normal haploids [23,X]. In 9 aneuploids, 5 showed the loss or gain of monads (so-called predivision), while 4 showed the loss or gain of dyads (so-called nondisjunction). Twenty-three oocytes out of 149 (15.4%) had one or more split dyads. (so-called nondisjunction). Twenty-three oocytes out of 149 (15.4%) had one or more split dyads. Our results were compared with those obtained in previous studies, and the importance of the chromosome preparation method in evaluating aberration frequencies was stressed. Causal mechanisms of aneuploidy, diploidy and structural anomaly were also discussed.

Chromosomal analysis of unfertilized human oocytes prepared by a gradual fixation-air drying method

Two hundred and sixty-five unfertilized human metaphase II (M II) oocytes from an in vitro fertilization program were studied cytogenetically using our chromosomal technique, a gradual fixation-air drying method. Of the 265 oocytes, 185 (70%) were successfully karyotyped. There were 21 aneuploids (11.4%) consisting of 8 hyperhaploids (4.3%), 11 hypohaploids (5.9%) and 2 complex cases (1.1%). There were also 9 structural anomalies (4.9%) and 18 diploids (9.7%). In aneuploidy, the loss or gain of dyads (so-called nondisjunction) occurred more frequently than the loss or gain of monads (so-called predivision). The frequency of abnormally behaved chromosomes (segregation errors) due to nondisjunction, anaphase lag and predivision was studied among the seven chromosomal groups (A-G) and compared with the frequency expected from an equal probability of segregation errors in each of the 23 chromosomes. The observed frequency was somewhat higher than the expected frequency in groups E and G but the difference was not statistically significant in either group. These results were discussed in relation to previous studies on human M II oocyte chromosomes.

A freezing and thawing method of hamster oocytes designed for both the penetration test and chromosome assay of human spermatozoa

Superovulated hamster oocytes were cryopreserved and thawed according to our carefully designed procedures. More than 90% (92 +/- 4%) of oocytes survived freezing and thawing. They were proven to be well conserved, showing excellent performance comparable to freshly ovulated oocytes in the human sperm penetration test (proportion of penetrated ova: 94.7% vs. 93.6%) and human sperm chromosome analysis (proportion of metaphasic ova: 81.8% vs. 83.6%). There was no statistically significant difference in the incidences of sperm chromosome aberrations between assays using fresh and frozen-thawed oocytes. In addition, there was no statistically significant increase of aberrations in female pronuclear (hamster) chromosomes. This freezing-thawing method was found to be reliable, yielding viable hamster oocytes of high quality.

Micronucleus test in 2-cell embryos as a simple assay system for human sperm chromosome aberrations

A micronucleus test method to assess radiation-induced chromosomal damage in human spermatozoa is described, and its efficiency examined by comparison with that of sperm chromosome analysis. Human spermatozoa were exposed in vitro to 1.11 and 2.13 Gy of 137Cs gamma-rays at a dose rate of 1.36 Gy/min. After interspecific in vitro fertilization of irradiated spermatozoa with zona-free hamster oocytes, a total of 193 monospermic eggs were examined with the micronucleus test at the 2-cell stage, and a total of 304 male pronuclear chromosome plates were analyzed according to our established method. The incidence of 2-cell embryos with micronuclei coincided well with the incidence of spermatozoa with chromosomal breaks and fragments (51.6% vs. 50.3% in the 1.11-Gy group and 82.7% vs. 79.3% in the 2.13-Gy group). A similar correlation was also found between the number of micronuclei per embryo and the number of breaks and fragments per spermatozoon (0.85 vs. 0.88 and 1.50 vs. 1.45 in the 2 dose groups, respectively). These results indicate that our micronucleus test is useful as a simple and rapid method for assessing the clastogenic effects of various environmental mutagens on human sperm chromosomes.

A method for chromosome analysis of ram spermatozoa using zona-free hamster oocytes

A method for displaying ram spermatozoan chromosomes using the interspecific zona-free hamster oocyte penetration was described to distinguish X- and Y-bearing spermatozoa. Semen samples from four rams were frozen and stored in liquid nitrogen. After thawing the samples, motile spermatozoa were collected by the swim-up method and treated with ionophore A23187 for the purpose of facilitating their capacitation. Slides were prepared by the gradual fixation-air dry method. The rates of oocyte penetration, first cleavage metaphase, and the number of ova that were karyotyped successfully were 67.9, 60.8 and 40.6%, respectively. The overall success rate (number of spermatozoa karyotyped/number of oocytes used for insemination) was 47.9%. A total of 1009 spermatozoa were analyzed, and the ratio of X- and Y-bearing spermatozoa was 508:501.

Dose-response relationship for the induction of structural chromosome aberrations in human spermatozoa after in vitro exposure to tritium beta-rays

The effects of tritium (HTO) beta-rays on human sperm chromosomes were studied using our interspecific in vitro fertilization system between human spermatozoa and zona-free hamster oocytes. Semen samples were treated with media containing 1.53-24.3 mCi/ml HTO for about 80 min. 1290 spermatozoa from the controls and 1842 spermatozoa from the irradiated groups were karyotyped. The incidence of spermatozoa with structural chromosome aberrations increased linearly with increasing dosage. Breakage-type aberrations occurred far more frequently than exchange-type. Chromosome-type aberrations appeared far more frequently than chromatid-type. All of these types of aberrations showed linear dose-dependent increases. The RBE values of HTO beta-rays relative to X-rays were calculated for the above-mentioned 5 indices, respectively. Their RBE values ranged from 1.89 to 3.00 when the absorbed dose was estimated to be the minimum, whereas the values ranged between 1.04 and 1.65 when the absorbed dose was estimated to be the maximum.

Types of structural chromosome aberrations and their incidences in human spermatozoa X-irradiated in vitro

We studied the effects of in vitro X-irradiation on human sperm chromosomes, using our interspecific in vitro fertilization system between human spermatozoa and zona-free hamster oocytes. 28 semen samples from 5 healthy men were exposed to 0.23, 0.45, 0.91 and 1.82 Gy of X-rays. Totals of 2098 and 2862 spermatozoa were karyotyped in the control and the irradiated groups, respectively. The incidence of spermatozoa with X-ray-induced structural chromosome aberrations (Y) increased linearly with increasing dosage (D), being best expressed by the equation, Y = 0.08 + 34.52 D. The incidence of breakage-type aberrations was more than 9 times higher than that of exchange-type aberrations. Both of them showed linear dose-dependent increases, which were expressed by the regression lines, Y = -0.014 + 0.478 D and Y = -0.010 + 0.057 D, respectively. The incidence of chromosome-type aberrations was about 6 times higher than that of chromatid-type aberrations. Their dose-dependent increases were expressed by the regression lines, Y = -0.015 + 0.462 D and Y = -0.006 + 0.079 D, respectively. These results are discussed in relation to the previous data obtained with gamma-rays. The repair mechanism of X-ray-induced sperm DNA lesions is also discussed.

An improved, efficient method for analyzing human sperm chromosomes using zona-free hamster ova

We have developed an improved method for analyzing human sperm chromosome, using zona-free hamster ova. Our main improvements of methodology are as follows: (1) Fertilization rate of hamster oocytes by human spermatozoa was markedly raised by successive treatments of the spermatozoa with 5-15 microM ionophore A23187 solutions and a capacitation medium (BWW medium) containing 3.5% HSA. The HSA most effective in inducing capacitation was selected from several kinds of HSA products commercially available. (2) Monospermic fertilization was ensured by inseminating oocytes with highly capacitated spermatozoa at a low concentration for a short time. (3) TC medium 199 was used for postinsemination culture of the eggs. (4) A medium containing podophyllotoxin and vinblastine (0.04 micrograms/ml each) was used to block karyogamy and first-cleavage spindle formation. (5) Chromosome slides were prepared with our gradual fixation-air-dry method instead of Tarkowski's method. Ninety-two to 177 spermatozoa corresponding in number to 43%-79% (mean: 62%) of the inseminated oocytes were successfully karyotyped in each experiment. In spite of above-mentioned quantitative improvements, quality of Q-banding was not necessarily satisfactory in our slides. Improvement of banding technique is an important problem to be solved in our method. Spontaneous incidence of chromosome aberrations was studied in a total of 1,091 spermatozoa obtained from nine semen samples from four donors. Incidences of aneuploidy and structural anomaly were 0.9% (hyperhaploidy, 0.45%; hypohaploidy, 0.45%) and 13.0%, respectively. Structural aberrations included breaks (45.1%), fragments (32.4%), exchanges (21.8%), and deletions (0.7%). Ratio of X-sperm to Y-sperm was 53% to 47%. These results were discussed in comparison with those reported previously.

A quantitative study of synaptic ribbons in pinealocytes of adult Chinese hamsters (Cricetulus griseus) under different photoperiodic conditions

Synaptic ribbons (SR) in pinealocytes of adult (120-130 day-old) male Chinese hamsters (Cricetulus griseus) were classified into types 1, 2 and 3; these have a central dense structure showing rod-like, various and ring-like profiles, respectively. The central structure of the type-2 SR usually appeared as round, oval or comma-like bodies, and occasionally as plates showing various profiles or club-shaped bodies. The quantity of each type of SR, expressed as the SR index, was determined over a 24-h period under a light/dark regime (LD) 12:12 or LD 14:10. On comparing the results obtained from adults with previously published data from young (60-70-days-old) animals under LD 12:12, it was found that, in both young and adult animals, the type-1 and type-3 SR indices exhibited different 24-h variations, whereas the type-2 SR index remained constant over a 24-h period. In addition, the indices of the type-2 SR, but not those of the other SR types, were found to be significantly larger in adult than in young animals. In adult animals, the effects of the photoperiod were different between the three types of SR. A nocturnal increase in the type-1 SR index was observed under both LD 12:12 and LD 14:10, its time course being different for each of these photoperiods. Under LD 14:10, the type-2 SR index showed a significant 24-h rhythm with larger values during the dark period; this was not observed under LD 12:12. The type-3 SR index was almost the same under LD 12:12 and LD 14:10.(ABSTRACT TRUNCATED AT 250 WORDS)

Maturation of spermatozoa in the epididymis of the Chinese hamster

Chinese hamster spermatozoa gain their ability to move when they descend from the testis to the distal part of the caput epididymis, but it is not until they enter the corpus epididymis that they become capable of fertilizing eggs. The maturation of the spermatozoa proceeds as they further descend the tract and perhaps continues even in the vas deferens. During transit between the distal caput and proximal cauda epididymides, small membrane-limited vesicles (and tubules) appear on the plasma membrane over the acrosomes of the spermatozoa. The number of vesicles appearing on the sperm brane reaches a maximum when the spermatozoa are in the proximal cauda epididymis. It declines sharply in the distal cauda epididymis. Spermatozoa in the vas deferens are free of the vesicles. The origin, chemical nature, and functional role of the vesicles that appear on the sperm surface during epididymal transit must be the subject of further investigation.