Gen-ichi Watanabe

Determination of prenatal sex ratio in man

SummaryThe sex of a conceptus at the early embryonic stage was diagnosed in 1000 induced abortions. Specimens were obtained from women who terminated their pregnancies within 12 menstrual weeks on socio-economic indications. By making use of the triple checking procedures, such as the karyotypic analysis of Giemsa-stained slides, the fluorescent Y chromosome analysis and the Y-body test in interphase nuclei, the sex ratio was determined as 106.6 (516 males/484 females). The sex distribution in the chromosomally normal embryos was 481 in males to 448 in females; that gave the ratio of 107.4. A slight excess of males was already present at this stage of pregnancy. When the ratios were calculated in relation to the maternal age, the lower sex ratio was noted for embryos born to mothers over 30 years. Taking a Y-bearing embryo as male, the ratio in 71 chromosomally aberrant embryos was 97.2 (35 males/36 females). The sex ratio in the cases of chromosome abnormalities was not statistically different from that of the normal embryos.

Chromosome studies in 500 induced abortions

SummaryA survery of the chromosome constitution in 500 induced abortions (5–12 menstrual weeks) was undertaken over a period of 1 1/2 years. There were 34 cases (6.8%) of gross chromosome anomalies: 2 cases of trisomy A; 5 of trisomy C (including XXX and XXY); 1 of mosaic trisomy C; 4 of trisomy D; 2 of trisomy E; 2 of trisomy G; 1 of double trisomy E and G; 1 of XYY; 4 of monosomy C (including XO); 2 of mosaic monosomy C; 1 of mosaicism of ring D chromosome; 1 of extra small metacentric chromosome; 3 of triploidy (including triploidy with double trisomy C and G); and 5 of tetraploidy and its mosaicism.An increased risk for the occurrence of trisomic anomalies was found with advancing age of the mothers. In contrast, the production of monosomies was not age-related. Trisomies were the most common type of anomalies and were found almost at random, regardless of the characteristics of chromosomes. Neither satellited nor smaller chromosomes were predominantly involved in the formation of chromosome anomalies.

Chromosomal aneuploidies and polyploidies in embryos of diabetic mice.

Female mice were given a single intravenous injection of alloxan (60 or 80 mg/kg body weight) and caged with normal males when the blood glucose levels rose significantly. The morning when a vaginal plug was found was designated as day 0.5 of pregnancy. Blastocysts were recovered after sacrifice of mothers on day 3.5 of gestation. Cytogenetic examinations of these embryos were made after air-drying of eggs, and the findings were compared with those observed in embryos taken from control groups. A marked decrease in the number of viable embryos recovered from diabetic pregnant mice was observed. Chromosomal analysis revealed a high incidence of polyploidy and aneuploidy in eggs from the diabetic group as compared with those from controls.

Causes of chromosome anomalies suggested by cytogenetic epidemiology of induced abortions

SummaryWomen who visited hospitals requesting induced abortions were asked about their obstetric and medical histories by attending physicians prior to the operation. The information was solely based on their reports at the interview. The period of coverage was nine weeks, comprising six weeks before and three weeks after the onset of the last menstruation. Both the occurrence of acute respiratory infectious diseases, which included the common cold, upper respiratory tract infection (U.R.T.I.), influenza, and pneumonia, and the use of analgesics and antipyretics were most frequently reported. Regardless of whether they had an acute respiratory illness, the women who took analgesics and antipyretics (including antihistamine, cough remedy, and nasal decongestant) had 13.8% (8/58) gross chromosome anomalies. The women without the treatment had 6.3% (71/1136) anomalies. The difference was statistically significant (P<0.05). Triploid formation was particularly related to drug consumption, thus there were 5.2% (3/58) in the treated group and 0.5% (6/1136) in the untreated group (P=0.0074). In contrast, trisomy was not considered to be related to drug consumption on account of 8.6% (5.58) and 4.1% (47/1136) in the corresponding groups (0.10<P<0.20). When the occurrence of trisomy was examined in connection with two variables, i.e., the presence of drug consumption and the age of mothers, association was not evident (χ2 assoc.=0.883,d.f.=1 by Cochran.s method). Besides these results, neither maternal X-irradiation nor irregularity of the menstrual period was found to be related to the frequency of chromosome anomalies in the progeny.

Eine weitere Chromosomenanalyse bei künstlichen Aborten

The cytogenetic data of 500 unpublished cases of induced abortions are reported. The incidence of gross chromosome abnormalities was 7.4% (37/500). The frequencies of chromosome abnormalities after 6 gestational weeks decreased gradually with advancing the gestational weeks, while the frequency in the group of 5 gestational weeks remained considerably high as 25.0%.SummaryThe cytogenetic data of 500 unpublished cases of induced abortions are reported. The incidence of gross chromosome abnormalities was 7.4% (37/500). The frequencies of chromosome abnormalities after 6 gestational weeks decreased gradually with advancing the gestational weeks, while the frequency in the group of 5 gestational weeks remained considerably high as 25.0%.