Neonatal outcome in discordant eutrophic twins: twin growth.

OBJECTIVE: To compare maternal characteristics and neonatal outcome in discordant twin gestations (DT) and concordant twin gestation (CT). METHOD: Maternal and neonatal data base of live twins >25 weeks' gestation (N=351 pairs) were reviewed for antepartum complications, labor beginning, mode of delivery, neonatal complications, malformations and perinatal mortality. The chi-squared analysis and Student t-tests were used to analyze the differences between discordant and concordant premature and term twin pairs, and appropriate for gestational age (AGA) twins, separately. RESULTS: DT occurred in 15.1% of all twin pregnancies. In preterm and term DT there were significantly more elective cesareans. Growth discordance among preterm and term eutrophic twins was not connected with increased neonatal death or other complications, except higher incidence of early neurological signs in term DT. CONCLUSION: We strongly believed that prematurity and not discordant growth of eutrophic twins has important influence on neonatal outcome.

Self-assembly of multinuclear coordination species with chiral bipyridine ligands: silver complexes of 5,6-CHIRAGEN(o,m,p-xylidene) ligands and equilibrium behaviour in solution.

The complexation reactions between Ag- and a series of enantiopure ligands belonging to the CHIRAGEN (from CHIRAlity GENerator) family (L1, L2, L3, based on (-)-5,6-pinene bipyridine) have been studied in solution. It has been shown that the length of the bridge plays a fundamental role in the self-assembly processes leading to different compounds: mononuclear complexes (with L3), mixtures of polynuclear complexes (with L2) and circular helicates (with L 1). Although the absolute configuration of the chiral centres in all three ligands is the same, the metal-centred chirality of L3 (delta) is inverted with respect to that in the other two complexes with L1 and L2 (delta). The metal configuration is thus opposite in the mononuclear complex with respect to the polynuclear species. Detailed thermodynamic studies were carried out for the Ag+ and L1 ligand system by 1H and 109Ag NMR spectroscopy (as a function of concentration, temperature and pressure). At low temperature and high pressure, the [Ag6L1(6)]6+ hexanuclear circular helicate forms a tetranuclear circular helicate [Ag4L1(4)]4+: 2[Ag6L1(6)]6+ <=> 3 [Ag4L1(4)]4+. The thermodynamics parameters, obtained by temperature and pressure variation, have the following values: K298 = (8.7 +/- 0.7) x 10(-5) mol x kg(-1), deltaHo = -15.65 +/- 0.8 kJ x mol(-1), deltaSo = -130.2 +/- 3 J x mol(-1) x K(-1) and deltaVo(256 K)= -160 +/- 12 cm3 x mol(-1). The reaction volume calculated according to Connolly's method indicates that the calculated structure of [Ag4L1(4)]4+ is plausible. Both the signs and large magnitudes of deltaSo and deltaVo are counterintuitive, yet can be understood by modelling methods.

Predetermined chirality at metal centers of various coordination geometries: a chiral cleft ligand for tetrahedral (T-4), square-planar (SP-4), trigonal-bipyramidal (TB-5), square-pyramidal (SPY-5), and octahedral (OC-6) complexes

Two tetradentate bispinene-bipyridine type ligands, each with six stereogenic carbon centers, were synthesized from (-)-alpha-pinene. Their ability to predetermine chiral configurations at metal centers was studied. The two diastereoisomers, L1 and L2, differ in their absolute configuration at the bridgehead position. These ligands form metal complexes with Ag(I), Pd(II), Zn(II), Cu(II), and Cd(II), with coordination numbers four, five, and six and with complete control of chirality at the metal centers. Using L1 rather than L2 leads to complexes of inverted absolute configuration at the metal centers. These diastereomeric coordination species can be obtained either as separate compounds or, in some cases, as solids containing them in a 1:1 ratio. Ligands L1 and L2 thus show that the pinene-bipyridines are versatile molecules for the formation of metal complexes with predetermined chirality. In all cases, absolute configurations were determined in the solid state by X-ray diffraction methods and in solution by CD spectroscopy. The sign of exciton couplets from the pi-pi* transitions always agrees with the expectations for a given local configuration at the metal center. The five-coordinate, inherently chiral species of Zn(II) and Cu(II) described in this article are the first examples of trigonal-bipyramidal metal complexes with predetermined absolute configuration containing topologically linear ligands.

[The effect of maternal smoking on pregnancy outcome]. / Utjecaj majcina pusenja na ishod trudnoce.

The aim of the study was to determine the influence of smoking on the pregnancy outcome. The retrospective study was based on the original database made at the Department of Gynecology and Obstetrics, Medical School, University of Rijeka, in the period between 1987 and 1997. In the mentioned period we analysed 37,417 total singleton births out of which there were 1,685 (4.5%) preterm and 35,732 (95.5%) term births, as well as 1,739 (4.6%) hypotrophic and 35,678 (95.4%) eutrophic newborns. The analysis of smoking during the whole pregnancy on the gestation outcome was performed in 9,895 (26.4%) parturient smokers and 27,522 (73.6%) parturient nonsmokers (control group). The frequency of preterm and/or term delivery, intrauterine fetal growth retardation, Apgar score, birth weight, as well as morbidity and perinatal mortality, were analysed in both groups. The frequency of preterm deliveries was 5.4% (n = 529) in parturient smokers and 4.2% (n = 1,156) in parturient nonsmokers. This difference is statistically significant (p < 0.001). The frequency of hypotrophic newborns born to parturient smokers (n = 631 or 6.4%) was statistically significantly higher (p < 0.001) compared to the frequency of hypotrophic newborns (n = 1,108 or 4.0%) born to parturient smokers. The obtained results point to the importance of chronic smoking during pregnancy as a risk factor in the development of maternal and/or fetal complications.

Stereoselective Synthesis of Coordination Compounds: Self-Assembly of a Polymeric Double Helix with Controlled Chirality.

Its information content is infinitely smaller than that of DNA, but its structure (see picture) ressembles the double-stranded helix produced by nature. This self-assembled, configurationally predetermined coordination polymer is built up from enantiopure chiral bipyridine-type ligands and silver ions.