Nucleic-Acid Analogs with Restricted Conformational Flexibility in the Sugar-Phosphate Backbone (‘Bicyclo-DNA’). Part 5. Synthesis, Characterization, and Pairing Properties of Oligo-αlpha-D-(bicyclodeoxynucleotides) of the Bases Adenine and Thymine (αlpha-Bicyclo-DNA)

10.1002/hlca.19950780816.abs A conformational analysis of the (3′S,5′R)-2′-deoxy-3′,5′-ethano-α-D-ribonucleosides (a-D-bicyclodeoxynucleosides) based on the X-ray analysis of N4-benzoyl-α-D-(bicyclodeoxycytidine) 6 and on 1H-NMR analysis of the α-D-bicyclodeoxynucleoside derivatives 1-7 reveals a rigid sugar structure with the furanose units in the l′-exo/2′-endo conformation and the secondary OH groups on the carbocyclic ring in the pseudoequatorial orientation. Oligonucleotides consisting of α-D-bicyclothymidine and α-D-bicyclodeoxyadenosine were successfully synthesized from the corresponding nucleosides by phosphoramidite methodology on a DNA synthesizer. An evaluation of their pairing properties with complementary natural RNA and DNA by means of UV/melting curves and CD spectroscopy show the following characteristics: i) α-bcd(A10) and α-bcd(T10) (α = short form of α-D)efficiently form complexes with complementary natural DNA and RNA. The stability of these hybrids is comparable or slightly lower as those with natural β-d(A10) or β-d(T10)( β = short form ofβ-D). ii) The strand orientation in α-bicyclo-DNA/β-DNA duplexes is parallel as was deduced from UV/melting curves of decamers with nonsymmetric base sequences. iii) CD Spectroscopy shows significant structural differences between α-bicyclo-DNA/β-DNA duplexes compared to α-DNA/β-DNA duplexes. Furthermore, α-bicyclo-DNA is ca. 100-fold more resistant to the enzyme snake-venom phosphodiesterase with respect to β-DNA and about equally resistant as α-DNA.

Reciprocity as a trigger of social cooperation in contemporary immigration societies?

While the system stabilizing function of reciprocity is widely acknowledged, much less attention has been paid to the argument that reciprocity might initiate social cooperation in the first place. This paper tests Gouldner’s early assumption that reciprocity may act as a ‘starting mechanism’ of social cooperation in consolidating societies. The empirical test scenario builds on unequal civic engagement between immigrants and nationals, as this engagement gap can be read as a lack of social cooperation in consolidating immigration societies. Empirical analyses using survey data on reciprocal norms and based on Bayesian hierarchical modelling lend support for Gouldner’s thesis, underlining thereby the relevance of reciprocity in today’s increasingly diverse societies: individual norms of altruistic reciprocity elevate immigrants’ propensity to volunteer, reducing thereby the engagement gap between immigrants and natives in the area of informal volunteering. In other words, compliance with altruistic reciprocity may trigger cooperation in social strata, where it is less likely to occur. The positive moderation of the informal engagement gap through altruistic reciprocity turns out to be most pronounced for immigrants who are least likely to engage in informal volunteering, meaning low, but also high educated immigrants.

Vertebral artery stenosis in the Basilar Artery International Cooperation Study (BASICS): prevalence and outcome

We assessed the prevalence of vertebral artery (VA) stenosis or occlusion and its influence on outcome in patients with acute basilar artery occlusion (BAO). We studied 141 patients with acute BAO enrolled in the Basilar Artery International Cooperation Study (BASICS) registry of whom baseline CT angiography (CTA) of the intracranial VAs was available. In 72 patients an additional CTA of the extracranial VAs was available. Adjusted risk ratios (aRRs) for death and poor outcome, defined as a modified Rankin Scale score ≥4, were calculated with Poisson regression in relation to VA occlusion, VA occlusion or stenosis ≥50 %, and bilateral VA occlusion. Sixty-six of 141 (47 %) patients had uni- or bilateral intracranial VA occlusion or stenosis ≥50 %. Of the 72 patients with intra- and extracranial CTA, 46 (64 %) had uni- or bilateral VA occlusion or stenosis ≥50 % and 9 (12 %) had bilateral VA occlusion. Overall, VA occlusion or stenosis ≥50 % was not associated with the risk of poor outcome. Patients with intra- and extracranial CTA and bilateral VA occlusion had a higher risk of poor outcome than patients without bilateral VA occlusion (aRR, 1.23; 95 % CI 1.02-1.50). The risk of death did not depend on the presence of unilateral or bilateral VA occlusion or stenosis ≥50 %. In conclusion, in patients with acute BAO, unilateral VA occlusion or stenosis ≥50 % is frequent, but not associated with an increased risk of poor outcome or death. Patients with BAO and bilateral VA occlusion have a slightly increased risk of poor outcome.