Rigid dimers formed through strong interdigitated H-bonds yield compact 1D supramolecular helical polymers

Hierarchical self-assembly of small abiotic molecular modules interacting through noncovalent forces is increasingly being used to generate functional structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H-bond supramolecular architectures, especially in H-bonded supramolecular polymers, can be achieved by using conformationally rigid molecular modules undergoing self-assembly through strong H-bonds. Their binding strength depends on the multiplicity of the H-bonds, the nature of donor/acceptor pairs and their secondary attractive/repulsive interactions. Here a functionalized molecular module is described, which is capable of self-associating through self-complementary H-bonding patterns comprising four strong and two medium-strength H-bonds to form dimers. The self-association of these phenylpyrimidine-based dimers through directional H-bonding between two lateral pyridin-2(1H)-one units of neighboring molecules allows the formation of highly compact 1D supramolecular polymers by self-assembly on graphite. A concentration-dependent study by scanning tunneling microscopy at the solid-liquid interface, corroborated by dispersion-corrected density functional studies, reveals the controlled generation of either linear supramolecular 2D arrays, or long helical supramolecular polymers with a high shape persistence.

Towards supramolecular engineering of functional nanomaterials: pre-programming multi-component 2D self-assembly at solid-liquid interfaces

Materials with a pre-programmed order at the supramolecular level can be engineered with a sub-nanometer precision making use of reversible non- covalent interactions. The intrinsic ability of supramolecular materials to recognize and exchange their constituents makes them constitutionally dynamic materials. The tailoring of the materials properties relies on the full control over the self-assembly behavior of molecular modules exposing recognition sites and incorporating functional units. In this review we focus on three classes of weak-interactions to form complex 2D architectures starting from properly designed molecular modules: van der Waals, metallo-ligand and hydrogen bonding. Scanning tunneling microscopy studies will provide evidence with a sub-nanometer resolution, on the formation of responsive multicomponent architectures with controlled geometries and properties. Such endeavor enriches the scientist capability of generating more and more complex smart materials featuring controlled functions and unprecedented properties.

[Serial amniocentesis in TTTS]

AIM OF THE STUDY

The aim of our study was to estimate the efficacy of serial amniocentesis in cases of acute polyhydramnion in TTTS. We analyzed the time and the route of delivery, as well as the status of newborns.

MATERIAL AND METHODS

The study group consisted of 13 twins with confirmed hydramnios. In each case thorough examination allowed to make the diagnosis of TTTS. After the examination patients were prepared for amnioreduction. During the procedure the excess of amniotic fluid was removed through the punction needle.

RESULTS

The therapy of TTTS was based mainly on serial amniocentesis. In 2 cases, due to an extremely high amniotic volume, the therapy was started with placing the catheter to provide continuous amniotic drainage. The volume of AF removed during the single amniocentesis varied between 700-3000 ml and depended on AFI and the gestational age. In one case maternal treatment with indomethacin was introduced beside amniocentesis and in 3 pregnancies the Digoxin therapy was implemented together with amniocentesis. In all cases the deliveries were preterm. The mean donor weight was 730 +/- 290 g and the mean recipient weight was 1145 +/- 435 g (the difference was approximately 37%). In 7 cases we observed an intrauterine demise of one fetus. The 5th min Apgar score was 1 pt (median). When the analysis was performed after exclusion of stillborns, the median Apgar score for donors and recipients was 4 and 2 pt respectively.

CONCLUSIONS

1. Acute TTTS is a rare pathology occurring in monochorionic twin gestations. 2. The concomitant pathologies include: acute hydramnios, preterm labor and delivery, intrauterine growth restriction, cardiac failure. 3. Serial amniocentesis are effective in significant prolongation of gestation (the mean interval between diagnosis and delivery 24 days). 4. The improvement of perinatal outcomes in twin gestations complicated by TTTS can be achieved by the combination of serial amniocentesis and the laser ablation of anastomoses.

[Doppler evaluation as a predictor of asphyxia in fetuses with intrauterine growth retardation (IUGR)]

Many papers showed that the pulsatility index of the fetal middle cerebral artery decreases during gestation. We observed equalization of the PI in MCA and PI in UMB in the perinatal period (after 38 weeks of gestation). We observed the increase the diastolic cerebral flow through the brain in cases of hypoxia. We interpreted that situation as a vasomotor response to fetal hypoxia (for example in IUGR). This phenomenon, is called in the literature as brain sparing effect. The aim of our study was estimation of application Doppler technique in diagnosis of changes in circulatory system in pregnancies complicated by intrauterine growth restriction (IUGR). We included 66 fetuses with IUGR and sonographic signs of the brain sparing effects, without any congenital malformation, oedema and genetic abnormalities to the study group. We included 1730 foetuses from normal, physiological pregnancies to the control group. In all cases time of gestation were calculated from Naegele's rule and were confirmed in sonographic examination before 16 weeks of gestation. SGA fetuses were defined on the basis of ultrasonographic measurements of BPD, HC, AC, FL and weight below 10th percentile of our reference curve. Sonographic examination were performed on Acuson 128 XP/10 with transducers (2.5 MHz-5 MHz). We performed Doppler examinations in MCA and UMB. Redistribution (brain sparing effect) was diagnosed when CPR (cerebroplacental ratio) was less than 1. We analysed the way and time of delivery and neoanatal follow up. Obtained in advance of researches results made possible expression of following conclusions: 1. Use of Doppler techniques in pregnancies complicated by IUGR makes possible diagnosis of hypoxia that helps in settlement of continuing or ending of pregnancy. 2. Changes in Doppler flows in foetus resoluteness outdistance irregular other values of biophysical methods of foetus monitoring.

Involvement of the essential yeast DNA polymerases in induced gene conversion

In the yeast Saccharomyces cerevisiae three different DNA polymerases alpha, delta and epsilon are involved in DNA replication. DNA polymerase alpha is responsible for initiation of DNA synthesis and polymerases delta and epsilon are required for elongation of DNA strand during replication. DNA polymerases delta and epsilon are also involved in DNA repair. In this work we studied the role of these three DNA polymerases in the process of recombinational synthesis. Using thermo-sensitive heteroallelic mutants in genes encoding DNA polymerases we studied their role in the process of induced gene conversion. Mutant strains were treated with mutagens, incubated under permissive or restrictive conditions and the numbers of convertants obtained were compared. A very high difference in the number of convertants between restrictive and permissive conditions was observed for polymerases alpha and delta, which suggests that these two polymerases play an important role in DNA synthesis during mitotic gene conversion. Marginal dependence of gene conversion on the activity of polymerase epsilon indicates that this DNA polymerase may be involved in this process but rather as an auxiliary enzyme.

Involvement of the essential yeast DNA polymerases in induced gene conversion

In the yeast Saccharomyces cerevisiae three different DNA polymerases alpha, delta and epsilon are involved in DNA replication. DNA polymerase alpha is responsible for initiation of DNA synthesis and polymerases delta and epsilon are required for elongation of DNA strand during replication. DNA polymerases delta and epsilon are also involved in DNA repair. In this work we studied the role of these three DNA polymerases in the process of recombinational synthesis. Using thermo-sensitive heteroallelic mutants in genes encoding DNA polymerases we studied their role in the process of induced gene conversion. Mutant strains were treated with mutagens, incubated under permissive or restrictive conditions and the numbers of convertants obtained were compared. A very high difference in the number of convertants between restrictive and permissive conditions was observed for polymerases alpha and delta, which suggests that these two polymerases play an important role in DNA synthesis during mitotic gene conversion. Marginal dependence of gene conversion on the activity of polymerase epsilon indicates that this DNA polymerase may be involved in this process but rather as an auxiliary enzyme.

Coexistence of left inguinal hernia and left colon cancer--a case report and literature review

Data on a patient with a coexisting left inguinal hernia and rectosigmoid cancer are reported. This case and the review of the literature reveal the necessity of full proctologic examination including sigmoidoscopy in each patient with inguinal hernia and nonspecific colorectal signs and symptoms.

Wilson's disease presenting in sisters as fulminant hepatitis with hemolytic episodes

Wilson's disease presenting as fulminant hepatic failure is a rare and poorly recognized disorder. When ophthalmic and neurologic signs are missing and liver biopsy cannot be performed the patients may not be diagnosed and treated specifically. An acute hemolysis only occasionally occurs in Wilson's disease but is considered a distinctive feature in the form of fulminant hepatitis. Two homozygous sisters suffering fatal Wilsonian fulminant hepatitis with hemolytic episodes are presented. Failure or delay in diagnosis seems to be responsible for high mortality in this form of Wilson's disease. Diagnostic value of familial history and laboratory results is discussed.

[The effect of dopamin on the microcirculation on the pancreas in hemorrhagic-shock (author's transl)]

The influence of Dopamine on microcirculation during hemorrhagic shock was investigated by means of the pancreas chamber technique (HEISIG, 1967). Parameter of microcirculation was the corpuscular flow velocity measured with the "flying spot" method. Simultaneously arterial and venous blood pressure, heart rate, blood gases and pH-status were registered. While a Dopamine-dosage of 5 mug/kg/min did not markedly effect perfusion of the pancreas, application of 10 as well as 20 mug/kg/min Dopamine caused a significant improvement of microcirculation. There was no difference between 10 and 20 mug/kg/min Dopamine. The increase of capillary perfusion can certainly not be explained by the small rise of blood pressure that was found under treatment with Dopamine. The results support the statement of the existence of Dopamine-specific receptors in pancreatic vessels. Compared to a group of animals treated with 5 mug/kg/min Dopamine and an untreated control group, survival rate of animals treated with 10 as well as 20 mug/kg/min Dopamine was significantly increased.