Imaging of viroids in nuclei from tomato leaf tissue by in situ hybridization and confocal laser scanning microscopy.

The intracellular localization of viroids has been investigated by viroid-specific in situ hybridization and analysis by digital microscopy of the distribution of the fluorescent hybridization signals. Isolated nuclei from green leaf tissue of tomato plants infected with potato spindle tuber viroid (PSTVd) were bound to microscope slides, fixed with formaldehyde and hybridized with biotinylated transcripts of cloned PSTVd cDNA. The bound probe was detected with lissamine--rhodamine conjugated streptavidin. Nucleoli were identified by immunofluorescence using the monoclonal antibody Bv96 and a secondary FITC-conjugated antibody. In plants infected with either a lethal or an intermediate PSTVd strain, the highest intensity of fluorescence that arose from hybridization with the probe specific for the viroid (+)strand was found in the nucleoli, confirming results of previous fractionation studies. A similar distribution was found for (-)strand replication intermediates of PSTVd using specific (+)strand transcripts as hybridization probes. In order to determine if viroids are located at the surface or in the interior of the nucleoli, the distribution of the fluorescence hybridization signals was studied with a confocal laser scanning microscope (CLSM). It was shown by three-dimensional reconstruction that viroids are neither restricted to the surface of the nucleoli nor to a peripheral zone, but are instead homogeneously distributed throughout the nucleolus. The functional implications of the intranucleolar location of viroids and their replication intermediates are discussed with respect to proposed mechanisms of viroid replication and pathogenesis

FDI and regional development policy

The transformations in the worldwide division of labour brought about by globalisation and technological change have shown an unintended negative effect, particularly evident in advanced economic systems: uneven spatial distribution of wealth and rising within-country inequality. Although the latter has featured prominently in recent academic and policy debates, in this paper we argue that the relevance of connectivity (here proxied by foreign capital investments, FDI) for regional economic development is still underestimated and suffers from a nation-biased perspective. As a consequence, the relationship between the spatial inequality spurred by the global division of labour and the changes in the structural advantages of regions remains to be fully understood in its implications for economic growth, territorial resilience and industrial policy. Furthermore, even though connectivity entails bi-directional links – i.e. with regions being simultaneously receivers and senders – attractiveness to foreign capital has long been at the centre of policy attention whilst internationalisation through investment abroad has been disregarded, and sometimes purposely ignored, in regional development policy agendas. We use three broad-brushed European case-studies to discuss some guiding principles for a place-sensitive regional policy eager to integrate the connectivity dimension in pursuing local economic development and territorial equity

Developmental changes in the responsiveness to ecdysterone of chromosome region I-18C of Chironomus tentans.

The presence of nascent RNA in chromosome region I-18C was revealed by the method of induced hybrid formation (IEH) and by use of anti-RNA: DNA antibodies. IEH signals were quantitated, and used as a measure of transcriptional activity in the region. The expansion of the I-18C region was also determined and used as an indication of local chromatin decondensation. Chironomus tentans larvae may undergo oligopause or they may develop subitaneously. It was found that the course of basal activity in I-18C differs substantially in these two modes of development. Most interestingly they also differ in activation of I-18C in response to in vitro ecdysterone treatment. Changes in hormonal responsiveness of I-18C parallel changes in the preexisting state of I-18C decondensation. Oligopause stage 5 animals, being most refractory in this respect, exhibit the most condensed I-18C chromosome region

B-Z DNA conformational transition in 1:1 electrolytes: Dependence upon counterion size.

AbstractWe have studied the B-Z transition of poly[d(G-C)] in the presence of alkali metal, tetramethylammonium and tetraethylammonium chlorides at room temperature. The measured critical salt concentrations increase in the order Na, K, Rb, TMA, Cs and are in good agreement with the theoretical values predicted from a statistical-mechanical treatment of the transition