Genetics and development: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in genetics and development.     

The nucleotide addition cycle of RNA polymerase is controlled by two molecular hinges in the Bridge Helix domain

Background  

Cellular RNA polymerases (RNAPs) are complex molecular machines that combine catalysis with concerted conformational changes in the active center. Previous work showed that kinking of a hinge region near the C-terminus of the Bridge Helix (BH-H_C) plays a critical role in controlling the catalytic rate.     

In vitro anticancer activity and evaluation of DNA duplex binding affinity of phenyl-substituted indoloquinolines

Phenyl-substituted indoloquinolines were studied for their biological activity and their DNA binding affinity. Water-soluble aminoalkyl derivatives were prepared and have shown significant in vitro anticancer activity. Unlike previous reports on the potential role of duplex DNA as target for various indoloquinoline based drugs, duplex UV melting experiments and fluorescence titrations suggest only weak and moderately strong binding of the phenyl-substituted indoloquinolines at 120 mM and 20 mM Na⁺ concentrations, respectively. Binding is suggested by ethidium displacement and circular dichroism experiments to be associated with drug intercalation between base pairs.     

Climate change effects on animal and plant phylogenetic diversity in southern Africa

Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.     

Automatic termination of radiofrequency energy upon catheter dislocation.

Since 1987 radiofrequency (RF) catheter ablation has proven to be an effective treatment for many cardiac arrhythmias. However, catheter dislocation during RF delivery may result in an unintentional heating of healthy non-arrhythmogenic tissue. Therefore, a device was developed (15 cm x 9 cm x 3 cm) consisting of a microprocessor, powered by a 9 V battery and to be connected between the indifferent cable of the RF generator and the patient's back electrode that continuously reads the electrode position information using a 3 dimensional electrode visualization system (LocaLisa). A red light indicates a sudden change in electrode position and an electronic switch is activated by the software to interrupt the connection between the indifferent electrode and the RF generator resulting in a high impedance shutdown and termination of RF energy delivery. Four different sensitivity settings (10 is most and 100 is least sensitive) can be selected and were tested in an in vitro tank setup during electrode dragging speeds of 0.5 to 20 cm/sec. For the sensitivity levels 10, 20, 50 and 100, an immediate termination of RF (Atakr II, Medtronic, 25 W) was demonstrated for an electrode dragging speed of greater or equal than 1, 2, 5 and 10 cm/sec, respectively. We conclude that the developed device may improve safety during ablation procedures of cardiac arrhythmias.     

A Biofilm Pocket Model to Evaluate Different Non-Surgical Periodontal Treatment Modalities in Terms of Biofilm Removal and Reformation,Surface Alterations and Attachment of Periodontal Ligament Fibroblasts

Background and Aim

There is a lack of suitable in vitro models to evaluate various treatment modalities intending to remove subgingival bacterial biofilm. Consequently, the aims of this in vitro-study were: a) to establish a pocket model enabling mechanical removal of biofilm and b) to evaluate repeated non-surgical periodontal treatment with respect to biofilm removal and reformation, surface alterations, tooth hard-substance-loss, and attachment of periodontal ligament (PDL) fibroblasts.

Material and Methods

Standardized human dentin specimens were colonized by multi-species biofilms for 3.5 days and subsequently placed into artificially created pockets. Non-surgical periodontal treatment was performed as follows: a) hand-instrumentation with curettes (CUR), b) ultrasonication (US), c) subgingival air-polishing using erythritol (EAP) and d) subgingival air-polishing using erythritol combined with chlorhexidine digluconate (EAP-CHX). The reduction and recolonization of bacterial counts, surface roughness (Ra and Rz), the caused tooth substance-loss (thickness) as well as the attachment of PDL fibroblasts were evaluated and statistically analyzed by means of ANOVA with Post-Hoc LSD.

Results

After 5 treatments, bacterial reduction in biofilms was highest when applying EAP-CHX (4 log10). The lowest reduction was found after CUR (2 log10). Additionally, substance-loss was the highest when using CUR (128±40 µm) in comparison with US (14±12 µm), EAP (6±7 µm) and EAP-CHX (11±10) µm). Surface was roughened when using CUR and US. Surfaces exposed to US and to EAP attracted the highest numbers of PDL fibroblasts.

Conclusion

The established biofilm model simulating a periodontal pocket combined with interchangeable placements of test specimens with multi-species biofilms enables the evaluation of different non-surgical treatment modalities on biofilm removal and surface alterations. Compared to hand instrumentation the application of ultrasonication and of air-polishing with erythritol prevents from substance-loss and results in a smooth surface with nearly no residual biofilm that promotes the reattachment of PDL fibroblasts.