Prenatal diagnosis of a stable de novo centric fission: a case report.

We report on the prenatal diagnosis of a baby with a de novo centromeric fission of chromosome 21. Both fission products were mitotically stable. Follow-up chromosome analysis after birth confirmed the centromere fission. This chromosome fission appears to be without clinical significance for this patient.

Incremental cost-effectiveness of incorporating oestriol evaluation in Down syndrome screening programmes.

As screening for Down syndrome becomes increasingly sophisticated, it is important to evaluate the newer technologies in terms of their cost-effectiveness. One recent addition to Down syndrome screening programmes is maternal serum unconjugated oestriol (uE3), especially when used in conjunction with maternal serum alpha-fetoprotein and human chorionic gonadotropin. Using assumptions used in a California proposal to justify an expanded screening programme for Down syndrome, we calculated both the average and the incremental cost-effectiveness of adding uE3. Using the base case assumptions, including an $8 fee for the uE3, the incremental cost-effectiveness of adding uE3 to the proposed California programme is $119,100 per case detected, a value that compares favourably with other Down syndrome screening programmes. The sensitivity analysis supports this conclusion over a wide range of assumptions. However, because of the uncertainty with some key data, it is still too early to fully support the inclusion of uE3 in Down syndrome screening programmes.

Disruption of ovarian development in alligator embryos treated with an aromatase inhibitor.

It has been suggested that sex differentiation in vertebrates is steroid hormone dependent, that estrogens play a critical role in ovarian differentiation, and that male sex differentiation will occur in the absence of estrogens. Using the model of the alligator in which sex can be manipulated by incubation conditions (eggs incubated at a constant temperature of 30 degrees produce 100% females, and at 33 degrees produce 100% males), a series of experiments using antiestrogens, antiandrogen, estradiol-17 beta, dihydrotestosterone (DHT), and aromatase inhibitors were performed. Test substances were injected into alligator eggs prior to gonadal sex differentiation and the eggs were incubated at male or female temperatures until just before expected date of hatching. Gonads were excised and the sex was verified histologically. Control embryos injected with vehicle produced the expected sex: females at 30 degrees and males at 33 degrees. Estradiol in eggs at 33 degrees (male temperature) produced 100% females and did not alter female development in eggs at 30 degrees. Antiandrogen, DHT, and a steroid antiestrogen had no discernible effect in either the 30 degrees or the 33 degrees eggs at the doses tested. The aromatase inhibitors aminoglutethimide and 4-hydroxyandrostenedione caused a moderate disruption of ovarian development and had no apparent effect on testicular development. The nonsteroidal aromatase inhibitor, Ciba Geigy 16949A, caused inhibition of ovarian development in all treated embryos. The Mullerian ducts did not appear to be affected by this treatment, or by any of the other treatments, and the gonads did not appear masculinized. We conclude that estrogen appears to be necessary for normal ovarian development, but that inhibition of estrogen synthesis alone is insufficient to cause masculinization. Likewise, exogenous androgens appear unable to masculinize embryonic gonads. The evidence suggests that testicular differentiation in amniote vertebrates is dependent on factors other than androgens or level of estrogens.

Prospective evaluation of maternal serum human chorionic gonadotropin levels in 3428 pregnancies.

As part of a multicenter prospective study, second-trimester human chorionic gonadotropin and alpha-fetoprotein concentrations were evaluated. Data included maternal age, human chorionic gonadotropin level, alpha-fetoprotein level, weight, race, and pregnancy outcome of 3428 pregnancies at between 15 and 20 weeks' gestation. The results of the study indicate that human chorionic gonadotropin levels decrease as maternal weight increases, that weight-adjusted human chorionic gonadotropin levels for Oriental and black women are higher than for white or Hispanic women, and that twin pregnancies have higher human chorionic gonadotropin levels than singleton pregnancies. Of 255 pregnancies that did not have normal outcomes, 54 (21.2%) had human chorionic gonadotropin levels greater than 2.0 multiples of the median and 26 (10.2%) had alpha-fetoprotein levels greater than 2.5 multiples of the median. Of 11 pregnancies with fetal aneuploidy, 6 (54.5%) had human chorionic gonadotropin levels greater than 2.0 multiples of the median. It is concluded that in human chorionic gonadotropin screening programs for fetal Down syndrome, weight and race adjustments are necessary for accurate risk assessment.

Maternal serum hCG and SP1 in pregnancies with fetal aneuploidy.

In a retrospective study, maternal serum levels of chorionic gonadotropin (hCG) and pregnancy specific beta 1-glycoprotein (SP1) from 63 pregnancies with aneuploid fetuses were compared to the levels observed in pregnancies with a chromosomally normal fetus. Thirty-eight percent of the abnormal pregnancies had elevated levels (greater than 2.0 multiples of the normal median [MoM]) of hCG and 14% had depressed levels (less than 0.25 MoM). With a false-positive rate of 5%, 44% of the 42 fetuses with trisomy 21 would have been detected by elevated hCG levels. With the same false-positive rate, only 21% had elevated SP1 levels. hCG was significantly depressed in 12 pregnancies affected by fetal trisomy 18.

Terminal deletions of the long arm of chromosome 7: five new cases.

Twenty-two cases of terminal deletions of the long arm of chromosome 7 have been reported. We present 5 new cases, 3 of which were ascertained due to fetal holoprosencephaly, one due to anencephaly, and one due to multiple structural defects in a 15-year-old boy. The presence of holoprosencephaly in 3 of the 5 cases reported herein and in 2 previously reported cases suggests that this manifestation may be commonly observed in individuals with deletion 7q.

The production of mouse fetal-placental chimeras using trisomy 16 and euploid blastocysts.

By means of a combination of immunosurgery and a modified method of microsurgery, blastocysts were reconstructed to produce viable chimeric fetal-placental units. Reciprocal reconstituted blastocysts were produced using euploid and trisomy 16 blastocysts. Reconstructed blastocysts yielded significantly smaller fetuses at day 17 of pregnancy than simultaneously transferred control blastocysts (mean body weight 0.49 g vs 0.64 g, P less than 0.01). However, apart from reduced size, no abnormalities were observed for any euploid fetus-euploid placenta construct. The three reconstructed blastocysts that yielded a trisomic fetus-trisomic placenta were viable when examined on day 17 and displayed the abnormalities typical of mouse trisomy 16. No reconstructed blastocyst that yielded a trisomic fetus-euploid placenta or a euploid fetus-trisomic placenta was viable beyond day 13 of development. One case in which a trisomic fetus had a placenta that was chimeric (euploid/trisomic) examined on day 17 displayed the abnormalities typical of a trisomic fetus but the placenta appeared histologically normal. The findings suggest that there is a coordination of the development of the fetus and the placenta that is essential for the development of the fetus.

Human chorionic gonadotropin levels in pregnancies with aneuploid fetuses.

Maternal serum human chorionic gonadotropin (hCG) and the free alpha-hCG subunit were evaluated in 249 women from 9 to 11 weeks gestation who subsequently underwent chorionic villus sampling for determination of fetal karyotype and in 20 women of 18 or more weeks gestation who were ascertained to have an aneuploid fetus by genetic amniocentesis. Seven of the first-trimester pregnancies were determined to be aneuploid and six had hCG levels in the normal range (one triploid pregnancy had elevated hCG levels) whereas 12 of the 20 second-trimester cases had abnormal hCG levels and an additional three had elevated levels of alpha-hCG. This study confirms the previous report of abnormal maternal serum hCG levels in women with an aneuploid fetus at greater than or equal to 18 weeks gestation and demonstrates that hCG evaluation is not useful at 9-11 weeks gestation for selecting pregnancies at risk for fetal aneuploidy.

Abnormal maternal serum chorionic gonadotropin levels in pregnancies with fetal chromosome abnormalities.

The alpha subunit of human chorionic gonadotropin (alpha-hCG), human chorionic gonadotropin (hCG) and alpha fetoprotein (AFP) were measured in the serum of 25 women with chromosomally abnormal fetuses between 18 and 25 weeks of gestation and in 74 normal pregnancies. AFP levels less than 0.5 multiples of the median (MoM) or greater than 2.5 MoM were observed in 24 per cent of the abnormal pregnancies and in 6.76 per cent of the normal pregnancies. A low concentration of hCG (less than 0.25 MoM) was observed in 8 per cent of abnormals and in 2.7 per cent of normals while an elevated concentration of hCG (greater than 2.5 MoM) was observed in 56 per cent of abnormals and in 1.35 per cent of normals. Elevated hCG-alpha (greater than 2.5 MoM) was observed in 28 per cent of abnormals and in none of the normals. Determination of elevated levels of hCG-alpha or hCG resulted in detection of 68 per cent of pregnancies with chromosomally abnormal fetuses with a false positive rate of 1.35 per cent. Determination of both elevated and depressed gonadotropin levels resulted in detection of 76 per cent of abnormal pregnancies with a false positive rate of 4.05 per cent. Measurement of hCG and hCG-alpha in maternal serum samples can be used as a screening procedure for detecting pregnancies at risk for fetal chromosome abnormalities.

Sex determination: a hypothesis based on steroid ratios.

This paper presents a hypothesis for sex determination based on the ratio of androgen to estrogen in the gonad during sexual differentiation. In vertebrates the ratio of these steroids, and therefore, the sex of an individual is controlled by the quantity of the enzyme aromatase. For animals with a ZZ, ZW sex determining mechanism, such as birds, in which the heterogametic sex is female, an inducer for the aromatase gene is postulated to be on the W chromosome. In animals with an XX, XY system in which the heterogametic sex is male, such as mammals, the Y chromosome is postulated to code for a repressor of the aromatase gene. This hypothesis can account for naturally occurring sex reversal such as seen in some fish and amphibians, experimentally induced sex reversal by administration of steroids in birds, reptiles, fish and amphibians, and temperature-dependent sex determination as in reptiles. For invertebrates the same hypothetical model applies though the specific androgenic and estrogenic steroids differ. Both the X-to-autosome ratio method of sex determination typified by fruit flies and the haplodiploid method of bees as well as hormonal control of sexual differentiation in crustaceans are accounted for by this hypothesis.

Radiation leukemia virus and X-irradiation induce in C57BL/6 mice two distinct T-cell neoplasms: a growth factor-dependent lymphoma and a growth factor-independent lymphoma.

Two different classes of neoplastic T cells were isolated from radiation leukemia virus (RadLV)-inoculated and from X-ray-treated C57BL/6 mice. One consisted of growth factor-dependent T-cell lymphoma (FD-TCL) lines which were established from the spleens and thymuses of treated mice within a day of lymphoma detection. FD-TCL cells were often eudiploid and could be grown in pure culture only at high concentrations, or on stromal feeder layers. Non-thymic, factor-dependent TCL cells produced interleukin-2 upon lectin stimulation, and were autostimulatory because they secreted growth factor(s) constitutively. Single cell cloning of FD-TCL cells in semisolid medium required the addition of exogenous conditioned medium. In vivo, FD-TCL cells that were injected intraperitoneally or intravenously homed to the spleen, proliferated in it and killed the injected mice. FD-TCL cells did not produce local tumors at the site of subcutaneous injection. The isolation and study of FD-TCL cells was facilitated by their cultivation on stromal hematopoietic monolayers in supplemented "lymphocyte medium", until an autostimulating, self-sustaining concentration of FD-TCL cells was obtained. FD-TCL cells could not be grown from lymphoid tissue of normal, control mice. In contrast, T-cell lymphoma (TCL) lines, which were established from virus-induced thymomas which had been kept in situ for 4-6 weeks after detection, consisted of factor-independent cells that possessed an aneuploid karyotype (in some cases trisomic for chromosome No. 15), and produced local tumors at the site of subcutaneous injection. These cells could be cloned in semisolid medium without addition of exogenous factor(s). The phenotypic markers of TCL cells differed from those of FD-TCL cells, suggesting heterogeneity in the stages of differentiation at which cells can give rise to growth factor-independent (TCL) and to growth factor-dependent (FD-TCL) lines.

Autocrine growth and progression of murine X-ray-induced T cell lymphomas.

Primary tumors of X-ray-induced murine T cell lymphomas comprise autocrine, growth factor-dependent cells. We have grown cell lines from primary X-ray-induced thymic lymphomas (PXTLs) under conditions which minimize the progression of the cells from factor dependence to factor independence. All (22) PXTL lines grown secrete a growth factor which supports their own growth and which we will call lymphoma growth factor LGF. LGF-dependent cells are non-tumorigenic or poorly tumorigenic, do not clone in soft agar, have no detectable rearrangements in the c-myc or Pim-1 region and possess near diploid or pseudodiploid karyotypes without evidence for trisomy of chromosomes nos. 15 or 17. PXTL-secreted LGF has no interleukin 1, 2, or 3 activity nor do LGF-secreting cells synthesize detectable IL-1, -2, or -3 mRNA. LGF contains no detectable interferon or GM-CSF activity in specific bioassays. Purified EGF, TGF beta, and interleukin preparations are inactive on LGF-dependent PXTL cells. Thus LGF appears to be a new growth factor that is required for the proliferation of non-progressed T lymphoma cells. Upon progression PXTL cells become growth factor independent, are highly tumorigenic in vivo, clone in soft agar, and assume a near triploid karyotype containing numerous chromosomal aberrations. Thus in X-ray-induced lymphomagenesis an autocrine, LGF-dependent phase precedes the progressed phase characterized by rearrangements in the myc and/or Pim-1 regions as well as by many chromosomal aberrations visible in the karyotype.

Prenatal diagnosis and follow up of a child with a complex chromosome rearrangement.

A case of de novo, apparently balanced, three way exchange by translocation plus a pericentric inversion is described. The karyotype is 46,XX,t(6;11)(p21;q21),t(11;21) (q21;p13),inv(6)(p21q11) and was ascertained through second trimester amniocentesis. The structural rearrangements appear balanced. The child was phenotypically normal at birth. Growth and motor development were normal until 30 months, at which time linear growth dropped below the 5th centile. In addition, there was delayed speech development at 2 years of age. As far as we can determine, this is the first report of a three chromosome exchange including a pericentric inversion ascertained through genetic amniocentesis.

Evaluation of amniotic fluid alpha-fetoprotein using an enzyme-linked immunosorbent assay.

A simple, inexpensive enzyme-linked immunosorbent assay using commercially available supplies is described. An examination of amniotic fluid alpha-fetoprotein (AFP) values for 15 to 20 weeks' gestation is presented. The interassay coefficient of variation was 12% (N = 40) at a level of 4.75 micrograms/mL. Repeat freezing, thawing, and storage at 4C for three months had no discernible effect on measured AFP value. Data comparison with a radioimmunoassay (RIA) kit indicates similar reliability for both assays. There were no false-negative values (zero of 20). The false-positive rate for RIA was 4.4% (13 of 295) and for enzyme-linked immunosorbent assay was 5.0% (15 of 295).

Mechanism of T-cell lymphomagenesis: transformation of growth-factor-dependent T-lymphoblastoma cells to growth-factor-independent T-lymphoma cells.

In a previous paper we described the induction by x-irradiation or radiation-induced leukemia virus-inoculation of two classes of lymphoid T-cell neoplasms: The first class, designated T-cell lymphoblastoma (TCLB), consists of growth-factor-dependent eudiploid cells that home to the spleen and give rise to splenic tumors on injection into syngeneic mice; the second class, designated T-cell lymphoma (TCL), consists of growth-factor-independent aneuploid or pseudodiploid cells that give rise to local tumors at the site of subcutaneous injection. This paper describes the generation of a family of growth-factor-independent aneuploid or pseudodiploid TCL cells after the injection into the thymus of growth-factor-dependent diploid TCLB cells. In contrast to the donor TCLB cells, the resulting TCL cells could be cloned in semisolid medium, produced local tumors at the site of subcutaneous injection, and proliferated in a growth-factor-independent fashion in vitro. The induced growth-factor-independent TCL cells were chromosomally and phenotypically unstable and continued to evolve both in vivo and in vitro. After propagation in the thymus, the cells often showed stable translocations in addition to the evolving aneuploidy. We propose that the chromosome abnormalities induced during the proliferation of growth-factor-dependent TCLB cells in the thymus constitute a general mechanism by which neoplastic cells progress from growth-factor dependency to independency.

Congenital anomalies in Lemur variegatus.

In a colony of black and white ruffed lemurs, Lemur (Varecia) variegatus subsp., similar congenital anomalies were found in successive years. Four malformed infants had skull defects, scoliosis, kinked tails, internal anomalies as well as reduced birth weights. The derived from one male and two females whose phenotypes are normal except for the kinked tail of the male. The possible causes including modes of inheritance are considered.