Structural chromosomal mosaicism and prenatal diagnosis

True structural chromosomal mosaicism are rare events in prenatal cytogenetics practice and may lead to diagnostic and prognostic problems. Here is described the case of a fetus carrying an abnormal chromosome 15 made of a whole chromosome 2p translocated on its short arm in 10% of the cells, in association with a normal cell line. The fetal karyotype was 46,XX,add(15)(p10).ish t(2;15)(p10;q10)(WCP2+)[3]/46,XX[27]. Pregnancy was terminated and fetus examination revealed a growth retardation associated with a dysmorphism including dolichocephaly, hypertelorism, high forehead, low-set ears with prominent anthelix and a small nose, which were characteristic of partial trisomy 2p. Possible aetiologies for prenatal mosaicism involving a chromosomal structural abnormality are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Prenatal diagnosis of trisomy 9. Six cases and a review of the literature

Six prenatally diagnosed cases of trisomy 9 are reported and 22 previously reported cases are reviewed; the difficulty of genetic counselling for such cases and the variation in the percentage of trisomic cells in different tissues, thus making accurate diagnosis of trisomy 9 difficult, are emphasized. In addition to karyotyping results, ultrasound findings are important in achieving diagnoses. Finally, a course of action when prenatal trisomy 9 is detected is proposed.     

Ecosystems and human health: The local benefits of forest cover in Indonesia

This paper documents the effect of primary forest cover loss on increased incidence of malaria. The evidence is consistent with an ecological response. I show that land use change, anti-malarial programs or migration cannot explain the effect of primary forest cover loss on increased malarial incidence. Falsification tests reveal that the effect is specific to malaria, with forest cover having no discernible effect on other diseases with a disease ecology different from that of malaria. Back-of-the-envelope calculations indicate that the morbidity-related malaria-reducing local benefits of primary forests are at least $1-$2 per hectare.     

Emission reduction and profit-neutral permit allocations

The present paper addresses two policy objectives: to implement a market for pollution permits and to make regulation acceptable for businesses. Profit-neutral permit allocations are defined as the number of permits that the regulator should give for free so that post-regulation profits (i.e. a firm's profits in the products market plus the value of the allowances granted for free) are equal to pre-regulation profits. The proposed model is developed by assuming that firms use polluting technologies and compete “à la Cournot”. The paper demonstrates that a low number of free allowances is sufficient to meet these two goals. Moreover, the regulator can fully offset losses, even when the reduction in emissions is high, provided that the sectors concerned are not monopolies, both for isoelastic and linear demand functions.     

Mosaicism for trisomy 12: Four cases with varying outcomes

Trisomy 12 observed in chorionic villus sampling (CVS) may reflect generalized mosaicism or indicate mosaicism confined to only the placenta. In this report, four cases of trisomy 12 observed in CVS or cultured placental biopsies with varying outcomes are presented. Seven dinucleotide repeat polymorphisms for chromosome 12 were used to determine the chromosome 12 origins in the fetus or child and to delineate the mechanism(s) that gave rise to the trisomy. In two cases (cases A and C), the mosaicism was confined to the placenta, resulting in normal liveborns. Although, in one case, the molecular results suggested an apparent duplication of one paternal chromosome 12 in the placenta, normal biparental inheritance was found in the diploid fetal cell line in both cases. In two other cases (cases B and D), trisomy 12 was observed in both extraembryonic and fetal tissues. In one of these pregnancies, a child was born by Caesarean section at 37 weeks because of intrauterine growth retardation and oligohydramnios, and resulted in neonatal death. Molecular markers and fluorescence in situ hybridization (FISH) revealed low-level trisomy 12 mosaicism in the spleen. In the fourth case, fetal abnormalities were detected on ultrasound and low-level trisomy 12 mosaicism was observed in amniotic fluid cells using conventional cytogenetics and FISH. Molecular markers revealed a maternal meiosis I non-disjunction of chromosome 12 in DNA from a cultured placental biopsy. Although predicting the outcomes of pregnancies involving confined placental mosaicism remains difficult, molecular techniques are valuable tools for distinguishing uniparental from biparental disomy and mechanisms of mosaicism.     

Elevated alpha-fetoprotein and human chorionic gonadotropin as a marker for placental trisomy 16 in the second trimester?

In a series of 2961 consecutive cases with second-trimester biochemical triple screening for Down's syndrome and neural tube defect (NTD), ten (0.3 per cent) showed an apparent increased risk for both conditions. Three cases had chromosomal abnormalities, namely trisomy 16 confined to the placenta. Since placental trisomy 16 as well as cases with increased alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) are associated with (intrauterine growth retardation (IUGR), oligohydramnios, and fetal demise, at least some cases with this atypical biochemical profile could be explained by this chromosomal abnormality. From our results we recommend that in cases with increased risk for both Down's syndrome and NTD, fetal karyotyping should preferably be done on a placental biopsy, especially when ultrasound in the absence of anomalies demonstrates early IUGR.     

13C脉冲标记法定量冬小麦光合碳分配及其向地下的输入

研究冬小麦生长向地下部分的输入对于土壤固碳和作物生产具有重要意义.分别在分蘖期、拔节期、花期和灌浆期,用~(13)CO2对冬小麦进行脉冲标记7 h,标记结束后28 d(示踪期)破坏性取样,测定冬小麦地上部、根、土壤和土壤呼吸中的~(13)C含量等指标.研究结果表明,在各标记时期,冬小麦光合固定的~(13)C大部分保留在地上部(51.6%~90.8%),且随小麦生长的进行而逐渐向地上部分配,向地下部分(根系、土壤和根际呼吸)的转移随生长进程的延续而降低.转移到地下部的~(13)C中,有22.9%~65.3%被根际呼吸消耗,24.3%~59.3%在根部保存,10.4%~17.8%通过根际沉积转化为土壤有机碳.示踪期28d内最后2 d呼吸产生的~(13)C只占整个示踪期根际呼吸~(13)C量的0.7%~2.7%,说明28 d的示踪期可以确保光合碳在各系统分配完全.在整个生育期内,冬小麦净吸收的光合碳分配到地上部、根部、土壤有机碳和根际呼吸的比例分别为78.5%、6.0%、3.1%和12.4%.结合当地生产方式估算,冬小麦在整个生育期内输入到地下的总碳量为1.72 t·hm~(-2),其中有0.99t·hm~(-2)被根际呼吸消耗,根部固持碳量为0.48 t·hm~(-2),0.25 t·hm~(-2)以有机碳沉积的形式进入土壤.