Isochromosome 21q is overrepresented among false-negative cell-free DNA prenatal screening results involving Down syndrome.

False-negative cell-free DNA (cfDNA) screening results involving Down syndrome are rare, but have high clinical impact on patients and their healthcare providers. Understanding the biology behind these results may allow for improved diagnostic follow-up and counseling. In 5 different centers offering cfDNA prenatal screening, 9 false-negative results were documented in 646 confirmed cases of trisomy 21; a false-negative rate of 1.

Integration of aerobic oxidation and intramolecular asymmetric aza-Friedel-Crafts reactions with a chiral bifunctional heterogeneous catalyst.

A new class of chiral bifunctional heterogeneous materials composed of Au/Pd nanoparticles and chiral phosphoric acids as active orthogonal catalysts was prepared by utilizing a facile pseudo-suspension co-polymerization method. It was found that this heterogeneous catalyst was capable of facilitating the sequential aerobic oxidation-asymmetric intramolecular aza-Friedel-Crafts reaction between benzyl alcohols and -aminoethylpyrroles. Moreover, the designed chiral heterogeneous catalyst could be recovered and reused several times without significant loss of activity or enantioselectivity.

Metal-free, one-pot conversion of proline derivatives into 2-aryl-3-iodo pyrrolidines by a sequential scission-iodination-arylation process.

The metal-free, direct conversion of readily available proline derivatives into 2-aryl-3-iodopyrrolidines is carried out under mild conditions and in good yields, using a sequential radical decarboxylation-oxidation-iodination-arylation reaction. These iodinated pyrrolidines are valuable precursors of other compounds. For instance, they can be cyclized to tricyclic compounds or undergo dehalogenation to 2-aryl-2,5-dihydro-1H-pyrroles, which are iminosugar and 2-arylpyrrole precursors.

Simplification of antitumoral phenanthroindolizidine alkaloids: short synthesis of cytotoxic indolizidinone and pyrrolidine analogs.

Hydroxylated seco-analogs of cytotoxic phenanthroindolizidine alkaloids were prepared in good yields from inexpensive 4-hydroxyproline derivatives, in just two steps. Thus, a sequential oxidative radical scission-oxidation was used for the direct conversion of the proline derivative into a 2-(2-aryl-oxoethyl)pyrrolidine with a variety of aryl and heteroaryl groups. The 4R-stereogenic center allowed ready isomer separation, and stereocontrol in the introduction of new chains (interestingly, the 2,4-cis isomers predominated).

Stereoselective conversion of sugar derivatives into C-nucleosides.

A two-step process for the transformation of readily available carbohydrate derivatives into acyclic C-nucleosides is described. The carbohydrate undergoes a scission process that is followed by the addition of aryl ketone derivatives, allowing the introduction of a variety of aryl rings. The resulting acyclic C-nucleosides are transformed into 2-deoxy cyclic pyranosides in good yield and excellent stereoselectivity.

Synthesis of indolizidinone analogues of cytotoxic alkaloids: monocyclic precursors are also active.

Readily available proline derivatives can be transformed in just two steps into analogues of cytotoxic phenanthroindolizidine alkaloids. The key step uses a sequential radical scission-oxidation-alkylation process, which yields 2-substituted pyrrolidine amides. A second process effects the cyclization to give the desired alkaloid analogues, which possess an indolizidine core.

Ultrasound detection rate of single umbilical artery in the first trimester of pregnancy.

Objective: To determine accuracy of first trimester detection of single umbilical artery (SUA).

Methods: The number of vessels in the umbilical cord was examined in a prospective cohort of 779 singleton, low-risk, unselected pregnancies, in the first (11-13 weeks) and second (17-24 weeks) trimesters, using both power and color Doppler and after delivery, by placental histopathologic exam. Concordance between first and second trimester findings to postnatal diagnoses was compared by calculating kappa coefficients.

Model-predicted performance of second-trimester Down syndrome screening with sonographic prenasal thickness.

Objective: The purpose of this study was to estimate the Down syndrome detection and false-positive rates for second-trimester sonographic prenasal thickness (PT) measurement alone and in combination with other markers.

Methods: Multivariate log Gaussian modeling was performed using numerical integration. Parameters for the PT distribution, in multiples of the normal gestation-specific median (MoM), were derived from 105 Down syndrome and 1385 unaffected pregnancies scanned at 14 to 27 weeks.

Fetal tricuspid valve Doppler at 11-13 weeks and 6 days: reference values and reproducibility.

Objective: To determine normal blood flow velocities across the fetal tricuspid valve (TV) at 11-13 weeks and 6 days of gestation and to examine the reproducibility of these measurements.

Methods: A prospective study involving 166 normal singleton pregnancies examined at 11-13 weeks and 6 days was carried out. Descriptive analysis of E- and A-waves' maximum velocities, E/A ratio, duration of the cardiac cycle (C) and diastole (D) and D/C ratio were calculated.

Fetal obstructive uropathy: is urine sampling useful for prenatal counselling?

Objectives: To evaluate whether fetal urinary sodium and chloride provide clinically useful information in addition to ultrasound in bilateral obstructive uropathy.

Methods: Sonographic features and urinary concentrations of sodium and chloride were evaluated in fetuses with bilateral obstructive uropathy. After a minimum of 12 months of postnatal follow-up, cases that developed increased serum creatinine (greater than 50 micromol/L) were compared with those that did not.

Association between prenatal sonographic findings and post-natal outcomes in 30 cases of isolated spina bifida aperta.

This study presents 30 cases of fetal isolated spina bifida aperta (SBA) to identify prenatal ultrasound findings that could predict the prognosis. Comparisons between surviving patients who had normal (group 1) and abnormal (group 2) post-natal neurological outcomes were made for three different prenatal signs, that is, site of vertebral lesion, presence and degree of ventriculomegaly and presence of talipes. The site of the lesion was the most significant outcome predictor, as high spinal dysraphisms were observed in 2 patients (2/7-28.