Search

Background. First trimetser screening by a combination of maternal age, fetal nuchal translucency and maternal serum free-b-hCG and PAPP-A can identify about 85-90% of fetuses with trisomy 21 and other mayor aneuploidies. The aim of this study was to compare risk calculations performed using two different softwares. materials and methods. PAPP-A and free-b-hCG concentrations were measured by electrochemiluminescent immunoassay /ECL) on Roche Elecsys analyzer. The obtained results were within the target values of internal and external quality assurance programme (UKNEQAS scheme for First Trimester Downs Syndrome Screening). Nuchal translucency was measured by sonographers with FMF Certificate of Competence. Risk calculations were performed using "SsdwLab 5.0.9" (Roche, certified by FMF) and "Fetal Medicine Foundation" softwares. Results. Patients (N=247) were devided into high, intermediate and low risk groups. The obtained distributions per group were: high risk 18 (7, 29%), intermediate risk 36 (14, 57%) and low risk 193(78, 14%)patients using SsdwLab 5.0.9 software vs. high risk 12 (4, 86%), intermediate risk 26 (10, 53%) and low risk 209 (84, 61%) patients using FMF software. 18 patients were classified as high risk by SsdwLab 5.0.9 vs. 10 (55, 6%) as high risk and 8 (44, 4%)as intermediate risk using FMF software. Only one fetus from the high risk group (by both softwares) was trisomy 21 positive, which was confirmed by amniocentesis. Conclusions. Comparing risk calculations performed using "SsdwLab 5.0.9" and "Fetal Medicine Foundation" softwares, we concluded that SSdwLab 5.0.9 calculates higher risk for the same input parameters. Further research will be aimed at discovering the causes of observed differences.

Cyclic nucleotide monophosphate (cNMP) hydrolysis in bacteria and eukaryotes is brought about by distinct cNMP phosphodiesterases (PDEs). Since these enzymes differ in amino acid sequence and properties, they have evolved by convergent evolution. Cyclic NMP PDEs cleave cNMPs to NMPs, and the Rv0805 gene product is, to date, the only identifiable cNMP PDE in the genome of Mycobacterium tuberculosis. We have shown that Rv0805 is a cAMP/cGMP dual specificity PDE, and is unrelated in amino acid sequence to the mammalian cNMP PDEs. Rv0805 is a dimeric, Fe(3+)-Mn(2+) binuclear PDE, and mutational analysis demonstrated that the active site metals are co-ordinated by conserved aspartate, histidine and asparagine residues. We report here the structure of the catalytic core of Rv0805, which is distantly related to the calcineurin-like phosphatases. The crystal structure of the Rv0805 dimer shows that the active site metals contribute to dimerization and thus play an additional structural role apart from their involvement in catalysis. We also present the crystal structures of the Asn97Ala mutant protein that lacks one of the Mn(2+) co-ordinating residues as well as the Asp66Ala mutant that has a compromised cAMP hydrolytic activity, providing a structural basis for the catalytic properties of these mutant proteins. A molecule of phosphate is bound in a bidentate manner at the active site of the Rv0805 wild-type protein, and cacodylate occupies a similar position in the crystal structure of the Asp66Ala mutant protein. A unique substrate binding pocket in Rv0805 was identified by computational docking studies, and the role of the His140 residue in interacting with cAMP was validated through mutational analysis. This report on the first structure of a bacterial cNMP PDE thus significantly extends our molecular understanding of cAMP hydrolysis in class III PDEs.