Mapping of epicardial deformation using a video processing technique

A method has been developed to measure deformation of the canine epicardium during the cardiac cycle simultaneously in a number (eight) of small regions (1 X 1 cm2). Approximately 50 white markers (diameter 1.5 mm) are attached to the epicardium and their motion is recorded on tape by a video camera. Marker positions are detected by computer processing of the digitized images. In each region the three deformation parameters are calculated from the displacements of all markers in that region by means of a least-squares criterium. In the experimental situation in the center of the area of the epicardium analyzed the accuracy of measuring circumferential strain, base-to-apex strain and shear is +/- 0.005, +/- 0.005 and +/- 0.002 rad, respectively. The method has been applied in an experiment in which local ischemia of the left ventricular wall was induced by occluding the anterior descending branch of the left coronary artery. Healthy and ischemic regions could clearly be distinguished by the differences in deformation.     

Adverse environmental conditions influence age-related innate immune responsiveness

Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder that belongs to a group of conditions called laminopathies which affect nuclear lamins. Mutations in two genes, LMNA and ZMPSTE24, have been found in patients with HGPS. The p.G608G LMNA mutation is the most commonly reported mutation. The aim of this work was to compile a comprehensive literature review of the clinical features and genetic mutations and mechanisms of this syndrome as a contribution to health care workers. This review shows the necessity of a more detailed clinical identification of Hutchinson-Gilford progeria syndrome and the need for more studies on the pharmacologic and pharmacogenomic approach to this syndrome.     

An evaluation of the diet of <Emphasis Type="Italic">Mysis relicta</Emphasis> using gut contents and fatty acid profiles in lakes with and without the invader <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis> (<Emphasis Type="Italic">Onychopoda,Cercopagidae</Emphasis>)

Diets of Mysis relicta from four lakes in central Ontario that had been invaded by Bythotrephes longimanus and three lakes that had not been invaded were investigated using gut content analysis and fatty acid (FA) composition. Gut content analysis of M. relicta revealed a high incidence of cannibalism in all lakes, and consumption of B. longimanus and native zooplanktivorous midges in the genus Chaoborus in lakes where these were present. Cladocera other than B. longimanus were present in the guts of all M. relicta examined except those from Bernard Lake, the lake with the most B. longimanus. In that lake, B. longimanus was the most frequent diet item. Copepod remains were found in 60–100% of M. relicta guts with the lowest frequency occurring in Bernard Lake. Fatty acids (FA) that contributed strongly to the variation in FA composition in M. relicta, as revealed by a principal component analysis, were C16:0 (palmitic acid), C16:1n7 (palmitoleic acid), C18:1n9c (oleic acid), C20:4n6 (arachidonic acid), C20:5n3 (eicosapentaenoic acid), and C22:6n3 (docosahexaenoic acid). Significant differences in FA amount and composition of M. relicta were found between invaded and non-invaded lakes, and among lakes within these groups. Generally, M. relicta in non-invaded lakes had higher concentrations of C16:0, C18:1n9c, C18:2n6c (linoleic acid), C18:3n3 (α-linolenic acid) and C20:4n6, while M. relicta in invaded lakes had higher concentrations of C22:6n3. Two of the non-invaded lakes had lower water transparency, as measured by Secchi depth, which may be the reason why mysids and abundant populations of Chaoborus spp. could be found in the water column during the day. However, differences in FA profiles and gut contents of M. relicta between invaded and non-invaded lakes are consistent with competition for Cladocera in the presence of the invader rather than pre-existing differences among lakes. We conclude that the diet of M. relicta is affected by the invasion of B. longimanus.     

Identifying the important HIV-1 recombination breakpoints

Recombinant HIV-1 genomes contribute significantly to the diversity of variants within the HIV/AIDS pandemic. It is assumed that some of these mosaic genomes may have novel properties that have led to their prevalence, particularly in the case of the circulating recombinant forms (CRFs). In regions of the HIV-1 genome where recombination has a tendency to convey a selective advantage to the virus, we predict that the distribution of breakpoints--the identifiable boundaries that delimit the mosaic structure--will deviate from the underlying null distribution. To test this hypothesis, we generate a probabilistic model of HIV-1 copy-choice recombination and compare the predicted breakpoint distribution to the distribution from the HIV/AIDS pandemic. Across much of the HIV-1 genome, we find that the observed frequencies of inter-subtype recombination are predicted accurately by our model. This observation strongly indicates that in these regions a probabilistic model, dependent on local sequence identity, is sufficient to explain breakpoint locations. In regions where there is a significant over- (either side of the env gene) or under- (short regions within gag, pol, and most of env) representation of breakpoints, we infer natural selection to be influencing the recombination pattern. The paucity of recombination breakpoints within most of the envelope gene indicates that recombinants generated in this region are less likely to be successful. The breakpoints at a higher frequency than predicted by our model are approximately at either side of env, indicating increased selection for these recombinants as a consequence of this region, or at least part of it, having a tendency to be recombined as an entire unit. Our findings thus provide the first clear indication of the existence of a specific portion of the genome that deviates from a probabilistic null model for recombination. This suggests that, despite the wide diversity of recombinant forms seen in the viral population, only a minority of recombination events appear to be of significance to the evolution of HIV-1.     

Cardiac resynchronization: insight from experimental and computational models

Cardiac resynchronization therapy (CRT) is a promising therapy for heart failure patients with a conduction disturbance, such as left bundle branch block. The aim of CRT is to resynchronize contraction between and within ventricles. However, about 30% of patients do not respond to this therapy. Therefore, a better understanding is needed for the relation between electrical and mechanical activation. In this paper, we focus on to what extent animal experiments and mathematical models can help in order to understand the pathophysiology of asynchrony to further improve CRT.     

Left ventricular apical torsion and architecture are not inverted in situs inversus totalis

Occasionally, individuals have a complete, mirror-image reversal of their internal organ position, called situs inversus totalis (SIT). Whereas gross anatomy is mirror-imaged in SIT, this might not be the case for the internal architecture of organs, e.g. the myofiber pattern in the left cardiac ventricle. We performed a Magnetic Resonance Tagging study in nine controls and in eight subjects with SIT to assess the deformation pattern in the apical half of the LV wall. It appeared that both groups had the same LV apical deformation pattern. This implies that not only the superficial LV apical layers in SIT follow a normal, not inverted pattern, but the deeper layers as well. Apparently, the embryonic L/R controlling genetic pathway does determine situs-specific gross anatomy morphogenesis but it is not the only factor regulating fiber architecture within the apical part of the LV wall. We propose that mechanical forces generated in the not-inverted molecular structure of the basic right-handed helical contractile components of the sarcomere play a role in shaping the LV apex.     

An introduction to provisional stenting

Provisional or conditional stenting should be defined as the use of stents limited to those conditions and cases in which the operator, despite an aggressive balloon angioplasty technique with large balloons and high pressure, has been unable to obtain a result that ensures optimal chances of early and late patency. The paramount issue is how to discriminate the patients with optimal results after balloon angioplasty for whom additional stent implantation is unlikely to improve or may even worsen long-term outcome. The better results of elective stent implantation in the OPUS study suggest that visual assessment of the PTCA result is not sufficient to detect lesions with suboptimal lumen gain after PTCA. The addition of physiologic parameters (Doppler flow velocity measurements, fractional flow reserve) has improved the results of the provisional stent group, with the best outcome observed when complex lesions and multivessel treatment were included in these studies (FROST, DESTINI). Intravascular ultrasound, although more expensive and time-consuming, has the additional advantage to guide the dilatation strategy.