Effect of sex difference on the in vitro and in vivo metabolism of aflatoxin B1 by the rat.
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Hepatic microsome-catalyzed metabolism of aflatoxin B1 (AFB1) to aflatoxin M1 and aflatoxin Q1 and the "metabolic activation" of AFB1 to DNA-alylating metabolite(s) were studied in normal male and female Sprague-Dawley rats, in gonadectomized animals, and in castrated males and normal females treated with testosterone. Microsomes from male animals formed 2 to 5 times more aflatoxin M1, aflatoxin Q1, and DNA-alkylating metabolite(s) than those from females. Castration reduced the metabolism of AFB1 by the microsomes from males by about 50%, whereas ovariectomy had no significant effect on AFB1 metabolism by the microsomes from females. Testosterone treatment (4 mg/rat, 3 times/week for about 6 weeks) of castrated immature males and immature females enhanced the metabolism of AFB1 by their microsomes. A sex difference in the metabolism of AFB1 by liver microsomes was also seen in other strains of rats tested: Wistar, Long-Evans, and Fischer. The activity of kidney microsomes for metabolic activation was 1 to 4% that of the liver activity and was generally lower in microsomes from male rats as compared to those from female rats of Sprague-Dawley, Wistar, and Long-Evans strains. The in vitro results obtained with hepatic microsomes correlated well with the in vivo metabolism of AFB1, in that more AFB1 became bound in vivo to hepatic DNA isolated from male rats and from a female rat treated with testosterone than that isolated from control female rats. These data suggest that the differences in hepatic AFB1 metabolism may be the underlying cause of the sex difference in toxicity and carcinogenicity of AFB1 observed in rats. (
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The sonographic identification of fetal gender from 11 to 14 weeks of gestation.
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OBJECTIVE: To determine the feasibility of correctly identifying fetal gender from 11 to 14 weeks' gestation. METHODS: A prospective cross-sectional study in a university Department of Obstetrics and Gynaecology, London. A total of 524 women from an unselected population underwent a detailed assessment of fetal anatomy at 11-14 weeks of gestation (confirmed by crown-rump length) by means of transabdominal sonography, and transvaginal sonography (26%) when necessary. Fetal gender was identified in the transverse and sagittal planes, and was confirmed at birth. RESULTS: The overall success of correctly assigning fetal gender increased with gestational age from 46% to 75%, 79% and 90% at 11, 12, 13 and 14 weeks, respectively. The ability of the operator to assign fetal gender significantly improved with increasing gestational age (p < 0.0001), being 59%, 87%, 92% and 98% at 11, 12, 13 and 14 weeks, respectively. The accuracy of correctly identifying fetal gender when attempted did not change with gestational age. Fetal gender or the performance of the scan by different operators did not affect the results. CONCLUSION: Whilst the accuracy of sonographic determination of fetal gender at 11-14 weeks is good, it still falls significantly short of invasive karyotyping tests. (
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First-trimester determination of fetal gender by ultrasound.
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OBJECTIVE: To assess the accuracy of fetal sex determination at 11-14 weeks of gestation. METHODS: Fetal gender assessment by ultrasound was prospectively carried out in 172 singleton pregnancies at 11-14 weeks of gestation immediately before chorionic villus sampling for karyotyping. The genital region was examined in a midsagittal plane and the fetal gender was assigned as male if the angle of the genital tubercle to a horizontal line through the lumbosacral skin surface was greater than 30 degrees and female when the genital tubercle was parallel or convergent (less than 30 degrees) to the horizontal line. RESULTS: The accuracy of sex determination increased with gestation from 70.3% at 11 weeks, to 98.7% at 12 weeks and 100% at 13 weeks. In the male fetuses, there was a significant increase in the angle of the genital tubercle from the horizontal with crown-rump length. Male fetuses were wrongly assigned as female in 56% of cases at 11 weeks, 3% at 12 weeks and 0% at 13 weeks. In contrast, only 5% of the female fetuses at 11 weeks were incorrectly assigned as male and this false-positive rate was 0% at 12 and 13 weeks. CONCLUSION: The clinical value of determination of fetal sex by ultrasound is in deciding whether to carry out prenatal invasive testing in pregnancies at risk of sex-linked genetic abnormalities, because invasive testing would be necessary only in pregnancies with male fetuses. Our results suggest that a final decision on invasive testing for sex-linked conditions should be undertaken only after 12 weeks of gestation. (
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Estrogen receptor in the human eye: influence of gender and age on gene expression.
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PURPOSE: Many epidemiologic studies indicate an increased incidence of certain vision threatening conditions in postmenopausal women. These data suggest that changes in sex steroid homeostasis may affect the physiology of the eye. To provide support to this hypothesis, the expression of estrogen receptor alpha (ERalpha) in human eye tissues was investigated. METHODS: Complementary studies including RNA analysis by reverse transcription polymerase chain reaction, western blot analysis, and immunocytochemistry were used to provide evidence of ERalpha expression. Protein detection was carried out using a mouse monoclonal antibody raised against an epitope located in the ligand binding domain of the human receptor. Cellular localization was studied on formalin-fixed paraffin-embedded eye sections using conventional immunohistochemical techniques. RESULTS: Gender and age differences in ERalpha mRNA expression were observed in retina. The 65-kDa ERalpha protein was detected in the retina and retinal pigment epithelium (RPE) of young female eyes but not in eye tissues dissected from men and postmenopausal women. Immunocytochemistry corroborated ERalpha staining of a young female neurosensory retina and RPE. In addition, ERalpha could be detected in the ciliary body, in the iris, and in the epithelium of the lens. CONCLUSIONS: The presence of the ERalpha in the human eye suggests that the sex steroid hormone axis may play a role in the pathogenesis of certain ocular diseases. (
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Sex ratios, family size, and birth order.
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In many countries, the male:female ratio at birth has varied significantly over the past century, but the reasons for these changes have been unclear. The authors observed a close parallel between decreasing family size and declining male:female sex ratio in Denmark from 1960 to 1994. To explain this finding, they examined the sex ratio and birth order of 1,403,021 children born to 700,030 couples. Overall, 51.2% of the first births were male. However, families with boys were significantly more likely than expected to have another boy (biologic heterogeneity). By the fourth birth to families with three prior boys, 52.4% were male. The increase varied directly with the number of prior boys (p for trend = 0.0007). Furthermore, couples with boys were more likely to continue to have children. In summary, the authors found that the declining male:female ratio in Denmark and probably other European populations is mainly attributable to three effects: declining family size, biologic heterogeneity, and child sex preference. Why families with boys are more likely to have additional boys is unknown. (
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Sexuality in the cellular slime mold Dictyostelium giganteum.
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By pairing of strains of Dictyostelium giganteum in various combinations this species was shown to be heterothallic. Four mating types were identified. Some strains could not be assigned a mating type and others showed no mating reaction. No self-compatible strains were found. Mutations were introduced in several strains and genetic crosses were performed. The results of these crosses show that mating and macrocyst formation are controlled by a single locus-multiple allele incompatibility system. The results also support the view that the myxamoebae that emerge upon germination of the macrocysts are the products of meiosis. (
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Sympathetic activation triggers ventricular arrhythmias in rat heart with chronic infarction and failure.
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OBJECTIVE: To seek direct evidence for a cause-effect relation between sympathetic activation and arrhythmogenesis. METHODS: Rats underwent open-chest surgery with either coronary artery occlusion or sham operation, and were studied 8 weeks later using in situ heart perfusion and nerve stimulation methods. RESULTS: Infarcted rats showed cardiac functional impairment and increased heart and lung weight. The extent of these changes correlated well with infarct size (IS). In in situ perfused hearts, sympathetic nerve stimulation (2 and 4 Hz, 45 s duration) induced a frequency-dependent release of norepinephrine (NE). NE release was lower in MI than that in control groups. In hearts with large IS (> or = 40%, n = 19) ventricular arrhythmias were rare at baseline, but nerve stimulation evoked the onset of ventricular premature beats (95%), tachycardia (37%) and fibrillation (26%), IS and stimulation frequency were key determinants for the inducibility of arrhythmias. Lower K- concentration enhanced arrhythmia inducibility. beta-blockade inhibited the frequency of arrhythmias produced by nerve stimulation. CONCLUSION: In infarcted rat hearts sympathetic activation is a potent trigger for the onset of ventricular tachyarrhythmias. (
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Differentiation of donor primordial germ cells into functional gametes in the gonads of mixed-sex germline chimaeric chickens produced by transfer of primordial germ cells isolated from embryonic blood.
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This study was carried out to elucidate whether primordial germ cells, obtained from embryonic blood and transferred into partially sterilized male and female recipient embryos, could differentiate into functional gametes and give rise to viable offspring. Manipulated embryos were cultured until hatching and the chicks were raised until maturity, when they were mated. When the sex of the donor primordial germ cells and the recipient embryo was the same, 15 out of 22 male chimaeric chickens (68.2%) and 10 out of 16 female chimaeric chickens (62.5%) produced donor-derived offspring. When the sex of the donor primordial germ cells and the recipient embryo was different, 4 out of 18 male chimaeric chickens (22.2%) and 2 out of 18 female chimaeric chickens (11.1%) produced donor-derived offspring. The rates of donor-derived offspring from the chimaeric chickens were 0.6-40.0% in male donor and male recipient and 0.4-34.9% in female donor and female recipient. However, the rates of donor-derived offspring from the chimaeric chickens were 0.4-0.9% in male donor and female recipient and 0.1-0.3% in female donor and male recipient. The presence of W chromosome-specific repeating sequences was detected in the sperm samples of male chimaeric chickens produced by transfer of female primordial germ cells. These results indicate that primordial germ cells isolated from embryonic blood can differentiate into functional gametes giving rise to viable offspring in the gonads of opposite-sex recipient embryos and chickens, although the efficiency was very low. (
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