Prenatal diagnosis of Pallister–Killian syndrome: Resolution of cytogenetic ambiguity by use of fluorescent in situ hybridization

We report a case of Pallister-Killian syndrome initially diagnosed prenatally as tetrasomy 21. A 33-year-old primiparous woman was noted at 24 weeks' gestation to have moderate polyhydramnios. Ultrasonography showed diminished fetal stomach filling, hydronephrosis, and prominence of the cisterna magna. Cytogenetic analysis of cultured amniocytes was initially interpreted as mosaic tetrasomy 21: 46,XX/47,XX,+i(21q). The patient was then referred to our centre for genetic counselling. At 34 weeks' gestation, a dysmorphic infant was delivered and died within 30 min. Physical features were consistent with the Pallister-Killian syndrome. Renal, gastrointestinal, and central nervous system anomalies were found at post-mortem examination. Analysis of peripheral lymphocytes revealed 5 per cent of cells with a marker chromosome, while 92 per cent of cultured fibroblasts had this same marker. Fluorescent in situ hybridization (FISH) using an alpha-satellite probe for chromosomes 13 and 21 failed to hybridize to the marker, while a chromosome 12 centromeric probe unequivocally identified it as an i(12p). Use of FISH can provide rapid, specific prenatal diagnosis of ambiguous marker chromosomes and improve prenatal counselling.     

A canadian collaborative study of mosaicism in amniotic fluid cell cultures

Data on chromosomal mosaicism was collected retrospectively on 12 386 amniotic fluid samples cultured over a 10 year period in 14 Canadian centres. Level I mosaicism (a single abnormal cell—excluding single cell monosomy) was encountered in 863 cases (7.1 per cent). Level II mosaicism (multiple cells with the same abnormality in a single flask or colony) was encountered in 138 cases (1.1 per cent). Level III mosaicism (multiple cells distributed over multiple flasks or colonies) was encountered in 34 cases (0.3 per cent). Analysis of the details of these cases allowed five major conclusions to be drawn: (1) Single cell abnormalities should not be taken as an indication of true fetal mosaicism. Only rarely will this interpretation prove to be incorrect. (2) Mosaicism involving multiple cells confined to a single flask should not be regarded as an indication of true fetal mosaicism. Only occasionally will this interpretation prove to be incorrect. (3) Mosaicism involving multiple cells distributed over more than one flask should be regarded as a strong indication of true fetal mosaicism. Sixty per cent will be confirmed by karyotype analysis of the fetus or infant. (4) Mosaicism of the XX/XY type is usually due to maternal cell contamination. Occasionally it can be a female fetus with XY cells from an unknown source. (5) The in situ or colony method of chromosome analysis has no clear advantage over the flask method for either the detection of true fetal mosaicism or for the ability to distinguish true mosaics from false positives.     

Assessing Secchi and photic zone depth in the Baltic Sea from satellite data

Long-term trends in the Secchi depth of the Baltic Sea have been interpreted in terms of eutrophication. The spectral attenuation coefficient Kd (490) can be estimated from remote sensing data. Given the empirical and theoretical relationships between diffuse attenuation and Secchi depth, it is therefore possible to estimate the trophic state from remote sensing data. This paper considers relationships among remotely sensed and in-water measured K (490), and Secchi depth data obtained during dedicated sea-truthing campaigns in the eastern Baltic Proper in 1999 (4) and in the western Baltic Proper/Himmerfj?rden area during 2001 and 2002. In-water measurements are used to establish the relationship between the PAR and the spectral attenuation coefficient in the Baltic Sea via regression analysis. The analysis showed that in the area of investigation Kd(490) is about 1.48 times higher than Kd (PAR). This relationship is then used to define the link between the photic zone depth and the remote sensing optical depth, Kd (490)-1. The results show that the depth of the euphotic zone is about 6.8 times Kd (490)-1. The regression analysis between Kd (PAR) and Secchi depth confirmed previous work that Kd (PAR) is about 1.7 of the inverse Secchi depth. Furthermore, an in-water algorithm between Secchi depth and Kd (490) is used to simulate a Secchi depth map of the Baltic Sea from SeaWiFS Kd(490) data. This map is verified against sea-truthing data. Kd (490) data derived from satellite is compared to in situ Kd (490), and the sources of error are discussed.     

Correlation between bioassay-derived P4501A1 induction activity and chemical analysis of clam (Laternula elliptica) extracts from McMurdo Sound, Antarctica

Variable levels of halogenated aromatic hydrocarbons were measured in clams (Laternula elliptica) collected from McMurdo Sound, Antarctica. Clams collected in and near Winter Quarters Bay contained high levels of organochlorine compounds, particularly polychlorinated biphenyls (PCBs). A strong gradient has been documented in Winter Quarters Bay that been linked to human activities at McMurdo Station. The activity of clam extracts as inducers of P4501A1-dependent ethoxyresorufin O-deethylase (EROD) activity was determined using in vitro bioassays utilizing rat hepatoma H4IIE cells. The extracts which exhibited the highest induction activities were those derived from clams collected in contaminated areas. Additionally, there was an excellent linear correlation between induced EROD activity versus total PCB levels (r²=0.96). The complimentary nature of both the analytical and bioanalytical data confirms the utility of the latter assay and provides a method for estimating the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents in extracts from marine biota.     

Synthesis, isolation and purification of C10-C13 polychloro-n-alkanes for use as standards in environmental analysis

Short chain (C10-C13) polychloro-n-alkanes (sPCAs) mixtures were synthesized by refluxing pure n-alkane (> 99%) with sulfuryl chloride (SO2Cl2) in the presence of UV-light (550 W). The free radical initiated reactions produced analogs containing approximately 4-9 chlorine atoms on each carbon chain. Purification of reaction products was achieved by adsorption chromatography on Florisil. The products were characterized by high-resolution gas chromatography/mass spectrometry (HRGC/MS) operated in the electron capture negative ionization (ECNI) and in electron ionization (EI) modes. Individual standards can now be combined to create standards whose profiles resemble that of environmental samples. Quantification of a known amount of the newly synthesized sPCAs mixture, using an industrial formulation as an external standard, resulted in an overestimation (approximately 28%) in its true value.     

Selective removal of organic contaminants from sediments: a methodology for toxicity identification evaluations (TIEs)

Aqueous slurries of a test sediment spiked with dibenz[a,h]anthracene, 2,4,5,2',4',5'-hexachlorobiphenyl, p,p'-DDE, or phenanthrene were subjected to decontamination experimentation. The spiked sediments were agitated at elevated temperatures for at least 96 h in the presence of either of the two contaminant-absorbing media: clusters of polyethylene membrane or lipid-containing semipermeable membrane devices (SPMDs). The effects of treatment temperature and surface area of media on the removal of contaminants were explored. This work is part of a larger methodology for whole-sediment toxicity identification evaluation (TIE). A method is being sought that is capable of detoxifying sediments with respect to organic contaminants while leaving toxicity attributable to inorganic contaminants unaffected.     

Biological dehalogenation and halogenation reactions

A large number of halogenated compounds is produced by chemical synthesis. Some of these compounds are very toxic and cause enormous problems to human health and to the environment. Investigations on the degradation of halocompounds by microorganisms have led to the detection of various dehalogenating enzymes catalyzing the removal of halogen atoms under aerobic and anaerobic conditions involving different mechanisms. On the other hand, more than 3500 halocompounds are known to be produced biologically, some of them in great amounts. Until 1997, only haloperoxidases were thought to be responsible for incorporation of halogen atoms into organic compounds. However, recent investigations into the biosynthesis of halogenated metabolites by bacteria have shown that a novel type of halogenating enzymes, FADH(2)-dependent halogenases, are involved in biosyntheses of halogenated metabolites. In every gene cluster coding for the biosynthesis of a halogenated metabolite, isolated so far, one or several genes for FADH(2)-dependent halogenases have been identified.     

Clock-shift experiments with Savannah sparrows, Passerculus sandwichensis, at high northern latitudes

Orientation can be difficult for nocturnal bird migrants at high northern latitudes because of the large changes of magnetic declinations, rapid longitudinal time-shifts experienced during a long-distance flight and the invisibility of stars during the polar summer. Both sunset cues as well as geomagnetic cues have been shown to be of great importance in the orientation system of Savannah sparrows, Passerculus sandwichensis. We used clock-shift experiments to investigate whether geomagnetic and sunset cues were used for migratory orientation by wild-caught young Savannah sparrows at high geomagnetic latitudes in Northern Canada. We exposed birds to a 4-h slow clock-shift, expecting a 60° clock-wise shift in orientation after the treatment. Under natural clear skies in the local geomagnetic field, the birds responded by showing a significant axial mean orientation directed towards the position of the setting sun in the NW and towards their preferred migratory direction in the SE. After exposure to the clock-shift for 6 days and nights the birds showed a clear response to the treatment and shifted significantly towards NNE. Birds that first oriented towards NW in the experiments before clock-shift tended to shift clock-wise, thus reacted to the clock-shift in the expected way. The reaction of the individual birds that originally oriented towards SE seems to vary. In summary, our birds did not select a constant angle (menotaxis) in relation to the sun's position during the experiments, but presumably were affected by the sun showing phototaxis or followed their magnetic compass. Possible explanations of the unexpected experimental results are discussed. Electronic Publication