Stem-spermatogonial survival and incidence of reciprocal translocations in the gamma-irradiated boar

Delayed manifestation and transmission bias of de novo chromosome mutations: their relevance for radiation health effect

The origin and transmission of de novo chromosome mutations were reviewed on the basis of our chromosome studies in retinoblastoma patients and male infertility. In a series of 264 sporadic retinoblastoma families, gross chromosome rearrangements involving the RB1 locus were identified in 23 cases (8.7%), of which 16 were non-mosaic and 7 were mosaic mutations. The newly formed chromosome mutations, whether they were non-mosaic or mosaic, had a strong bias towards paternally derived chromosome, indicating that they shared a common mechanism where a pre-mutational event or instability is carried over to zygote by sperm and manifested as gross chromosome mutation at the early stages of development. The de novo chromosome mutations are preferentially transmitted through female carriers. This transmission bias is consistent with the finding of higher frequencies of translocation carriers in infertile men (7.69% versus 0.27% in general populations) in whom meiotic progression is severely suppressed, possibly through activation of meiotic checkpoints. Such a meiotic surveillance mechanism may minimize the spreading of newly-arisen chromosome mutations in populations. A quantitative model of meiotic surveillance mechanism is proposed and successfully applied to the published data on ;humped' dose-response curves for radiation-induced spermatogonial reciprocal translocations in several mammalian species.

X-ray induced translocations in premeiotic germ cells of monkeys

The induction of reciprocal translocations by various X-ray exposures was studied in spermatogonial stem cells of rhesus monkeys (Macaca mulatta) and stump-tailed macaques (Macaca arctoides) by means of spermatocyte analysis many cell generations after irradiation. The yields of translocations recovered from irradiated stump-tailed macaques were lower than those observed in rhesus monkeys and represent in fact the lowest induction rates per Gy ever recorded for experimental mammals. In the rhesus monkey a humped dose-effect relationship was found with (a) a homogeneous response with (pseudo-)linear kinetics below 1 Gy, (b) much more variability at higher doses, and (c) no induction at all at doses of 4 Gy and above. It is suggested that the post-irradiation proliferation differentiation pattern of surviving rhesus monkey spermatogonial stem cells i mainly responsible for these characteristics of the dose-response curve.

Dose-effect relationship for X-ray-induced reciprocal translocations in mouse spermatogonia following pretreatment with 3-aminobenzamide

The influence of 3-aminobenzamide (3-AB) pretreatment on the dose-response relationship for radiation-induced reciprocal translocations in mouse spermatogonial stem cells was studied. The results show that at doses of 3-10 Gy of X-rays the frequencies of translocations were higher in 3-AB-pretreated animals as compared to animals that received X-rays only. The 3-AB pretreatment was not effective at dose levels of 1 and 2 Gy. The shape of the dose-effect curve was similar to that obtained without 3-AB pretreatment, i.e., a humped curve, but the initial slope was clearly steeper and the position of the peak was shifted from 7 to 9 Gy. The effects observed can be explained by a 3-AB-mediated sensitization of normally radioresistant stem cells that are at the stage of stimulation to enter the mitotic cycle, thus increasing the population of radiosensitive spermatogonial stem cells.

X-ray-induced translocations in marmoset (Callithrix jacchus) stem-cell spermatogonia

The induction of reciprocal translocations in spermatogonial stem cells of marmosets (Callithrix jacchus) was studied after irradiation with different doses of X-rays (50, 100 and 200 rad) via spermatocyte analysis many cell generations later. The obtained results show a dose-effect relationship with clear saturation effects at 200 rad. The recorded frequencies of translocations were much lower than those reported for closely related marmosets (Saguinus fuscicollis and Saguinus oepidus). Possible reasons for this difference are discussed.

Reproductive and genetic effects of continuous prenatal irradiation in the pig

The stem germ cells of the prenatal pig are highly vulnerable to the cytotoxic effects of ionizing irradiation. This study was conducted to determine whether sensitivity to killing was also marked by a sensitivity to mutation and how prenatal depletion of the germ-cell population affects reproductive performance. Germ-cell populations were reduced by continuously irradiating sows at dose rates of either 0.25 or 1.0 rad/day for the first 108 days of gestation. The prenatally irradiated boars were tested for sperm-producing ability, sperm abnormalities, dominant lethality, reciprocal translocations, and fertility. Prenatally irradiated females were allowed to bear and nurture one litter, then tested for dominant lethality in a second litter; germ cell survival and follicular development were assessed in their serially sectioned ovaries. Sperm production was not significantly affected in the 0.25-rad boars, but boars irradiated with 1.0 rad per day produced sperm at only 17% of the control level. Incidence of defective sperm was 4.9% and 11.1% in the 0.25 and 1.0 groups, respectively. Four of the 1.0-rad boars were infertile, but prenatal irradiation apparently caused neither dominant lethality nor reciprocal translocations in fertile males. Number of oocytes was reduced to 66 +/- 7% of control in the 0.25-rad gilts, but reproductive performance was unaffected and no dominant lethality was observed. Only 7 +/- 1% of the oocytes survived in the 1.0-rad group. Reproductive performance was normal for the first litter, but four of the 23 sows tested were infertile at the second litter and a significant incidence of dominant lethality was observed.(ABSTRACT TRUNCATED AT 250 WORDS)