Experimental and Theoretical Characterization of the Valence Isomerization of Bi-2H-azirin-2-yls to Diazabenzenes

3,4-diazidocyclobutenes 16 were prepared from the corresponding dihalides. Some of these diazides, such as parent compound 16 d and phenyl-substituted derivatives 16 c,f, underwent spontaneous stereoselective electrocyclic ring opening below room temperature, whereas the tetraalkyl derivatives of 16 had to be heated to force the same reaction. In most cases, the resulting 1,4-diazidobuta-1,3-dienes 8 were isolated to study their photochemical transformation into bi-2H-azirin-2-yls 9 via intermediate mono-azirines 17. Except for starting materials with a low number of substituents such as 9 d and 9 f, title compounds 9 underwent a thermal valence isomerization which led exclusively to pyridazines 18 at surprisingly low temperatures. Based on quantum-chemical calculations for the parent bi-2H-azirinyl-2-yl 9 d at the UB3LYP/6-31+G(d) and MR-MP2/TZV(2df,2p) levels, the valence isomerization process is best explained by simultaneous homolytic cleavage of both C--N single bonds of 9 to generate energetically favorable N,N' diradicals 26, which cyclize to 18. The theoretical studies indicate also that one stereoisomer of 9, namely, the rac compound, should undergo valence isomerization more easily than the other, which is in conformity with different rates of these rearrangement reactions found experimentally. For the tetramethyl-bi-2H-azirin-2-yls 9 g, which are better models for the experimentally studied compounds, simultaneous homolytic cleavage of both C--N single bonds is also predicted by the calculations, although the intermediate diradicals 26 g are significantly higher in energy than those of the parent system 9 d.

Downregulation of Apaf-1 and caspase-3 by RNA interference in human glioma cells: Consequences for erucylphosphocholine-induced apoptosis

Erucylphosphocholine (ErPC) exerts strong anticancer activity in vivo and in vitroand induces apoptosis even in chemoresistant glioma cell lines. We investigated the contribution of Apaf-1 and caspase-3 to the apoptotic response to ErPC using RNA interference (RNAi) in human glioblastoma cells. We could demonstrate that human glioma cell lines are susceptible to RNAi. Apaf-1 and caspase-3 are amenable to specific small interfering RNA (siRNA)-induced degradation resulting in a reduction of protein levels to 8-33% (Apaf-1) and to 30-50% (caspase-3). Transfection of siRNA directed to Apaf-1 and caspase-3 specifically reduced caspase-3 processing induced by ErPC treatment and yielded a reduction in cells that undergo ErPC-induced apoptosis to 17-33% (Apaf-1) and to 38-50% (caspase-3). The caspase-3 siRNA experiments were corroborated in caspase-3-deficient and -reconstituted MCF-7 breast cancer cells. Survival assays and morphological observations revealed that caspase-3 reconstitution significantly sensitized MCF-7 cells to ErPC. Exploring the caspase cascade responsible for ErPC-induced apoptosis MCF-7 cells provided evidence that caspase-3 is required for the activation of caspases-2, -6 and -8 and also participates in a feedback amplification loop. Our results provide evidence that Apaf-1 and caspase-3 are major determinants of ErPC-induced apoptosis and the possible use of ErPC in a clinical setting is discussed.

[The Estonian Genome Project in the context of European genome research]

It is the aim of the Estonian Genome Project to establish a database which compiles phenotype and genotype data of a large part of the Estonian population. The Gene Bank will only be used for scientific and public health research. Researchers hope that it will help identify disease genes and prepare the ground for the personalized medicine of the future. Additionally, the project will improve Estonian's international competitiveness in high technology and have a strong educational effect on the population. The legal framework, the Human Genes Research Act, was passed by the Estonian parliament in December 2000. It had been drafted by a group of experts who took into account all available international guidance documents on genetic research. With the pilot project involving three selected regions successfully finished, the main project has now started.

Femtosecond formation of coupled phonon-plasmon modes in InP: Ultrabroadband THz experiment and quantum kinetic theory

The ultrafast transition of an optical phonon resonance to a coupled phonon-plasmon system is studied. After 10-fs photoexcitation of i-InP, the buildup of coherent beats of the emerging hybrid modes is directly monitored via ultrabroadband THz spectroscopy. The anticrossing is mapped out as a function of time and density. A quantum kinetic theory of microscopic carrier-carrier and carrier-LO-phonon interactions explains the delayed formation of the collective modes. The buildup time is quantitatively reproduced to scale with the oscillation cycle of the upper branch of the coupled resonance.

MULTIPLE ORIGIN OF VIVIPARITY IN SOUTHEAST ASIAN GASTROPODS (CERITHIOIDEA: PACHYCHILIDAE) AND ITS EVOLUTIONARY IMPLICATIONS

This study aims at a better understanding of the evolutionary significance of viviparity in some freshwater gastropods. We use a phylogeny based on partial sequences of the mitochondrial 16S gene of representatives of the limnetic and pantropical Pachychilidae to infer the relationships within this particular group of cerithioideans and the evolution of reproductive strategies. The phylogeny presented herein implies a new systematization and suggests that viviparity has appeared three times among the Pachychilidae. This is supported by the finding of very distinct reproductive morphologies in different lineages of viviparous taxa that are exclusively found in Southeast Asia. Based on the observation that oviparity is the ancestral character state in this freshwater family, we conclude that viviparity has evolved subsequent to the exploration of freshwater. We present data showing that all Pachychilidae produce considerably larger but fewer egg capsules compared to most marine snails. In other studies on freshwater gastropods, this has been discussed as an adaptation to freshwater environments. In this context we hypothesize that the increased parental investment involved in the enlargement of eggs in concert with the reduction of clutch sizes was the driving factor that ultimately lead to the evolution of viviparity in the Asian taxa. Consequently, although not directly correlated with the colonization of the new adaptive zone, viviparity is strongly favored by other consequences of this step. Hence, we hypothesize that the production of large eggs, which is necessitated by the exploration of freshwater, represents a preadaptation existing in those ancestors from which viviparous pachychilid lineages eventually evolved in Southeast Asia.

[Health telematics/telemedicine in the republic of Estonia]

The people of Estonia, who until their independence had been systematically deprived of all forms of information, have shown a ready acceptance of the use of information technology in all areas of life. This environment and an excellent IT infrastructure have since the beginning of the new century provided favourable conditions for developing various individual projects in telemedicine. At the core of current telemedical applications in Estonia is the BITNET Project (in neurology, general medicine), built up with Swedish cooperation, and three German-Estonian projects (in telecardiology and telepathology). These projects are accompanied by studies of their cost-effectiveness. They constitute the basis for the plan that routine telemedical services be taken over by the Estonian health insurance. Differing from the situation in the Scandinavian countries, which have had an effective national telemedical service for over ten years, the special feature of telematrics in Estonia is its international networking with foreign centres of excellence. This has its origin in the aim of Estonian health policy to ensure medical services within its own country in all branches of medicine.

[Interventional cardiology in Latvia from 1993 to 2003]

A nationale programme for combatting cardiovascular diseases is being implemented in Letvia. A milestone was reached in 1993 with the establishment of a Letvian Centre for Cardiology. Within 10 years the only cardiac catheterization unit in the country has developed into a centre of excellence. But to meet the cardiological needs for all of Letvia requires at least three additional units for left heart catheterization and one for paediatric a cardiac catheterization.

Magneto-Structural Characterization of Metallocene-Bridged Nitronyl Nitroxide Diradicals by X-Ray, Magnetic Measurements, Solid-state NMR Spectroscopy, and Ab Initio Calculations

Crystallization of ferrocene and ruthenocene substituted in the 1- and 1'-positions by two nitronyl nitroxide radicals gave the new crystal phases beta-1 (besides the known phase alpha-1), alpha-2, and beta-2 whose structures were determined by X-ray analysis. In beta-1 the radical moieties adopt transoid positions, whereas two different cisoid conformations are adopted by alpha-2 and beta-2. These conformations result from inter- and intramolecular hydrogen bonds, respectively. All compounds experience antiferromagnetic interactions, and J/k(B) values up to -7 K have been found by fitting the experimental magnetic susceptibilities to a modified Bleaney-Bowers equation. The solid diradicals alpha-1, beta-1, alpha-2, and beta-2 as well as the ferrocene 3, which was substituted by a unique nitronyl nitroxide, were investigated by (13)C and (1)H NMR spectroscopy with magic angle spinning. The carbon signals cover a range of 2000 ppm, and are well resolved such that the structure could be confirmed. Conversion of the signal shifts into spin densities disclosed the mechanisms by which spin delocalization from the nitronyl nitroxide substituents to the metallocene core occurs. The spin density distribution in alpha-1, beta-1, and 3 was also predicted by DFT calculations. There is good agreement between the experimental and theoretical trends of the spin delocalization. The magnetic interactions were discussed in the light of intramolecular spin transfer and its dependence on geometric constraints, demonstrating that the 1,1'-metallocenylene bridge is not a robust magnetic coupler.