Instability in the Central Region of Tropomyosin Modulates the Function of Its Overlapping Ends

The causal link between disparate tropomyosin (Tm) functions and the structural instability in Tm is unknown. To test the hypothesis that the structural instability in the central region of Tm modulates the function of the overlapping ends of contiguous Tm dimers, we used transgenic mice (Tm_DM) that expressed a mutant α-Tm in the heart; S229E and H276N substitutions induce structural instability in the central region and the overlapping ends of Tm, respectively. In addition, two mouse cardiac troponin T mutants (TnT_1–44Δ and TnT_45–74Δ) that have a divergent effect on the overlapping ends of Tm were employed. The S229E-induced instability in the central region of Tm_DM altered the overlapping ends of Tm_DM, thereby it negated the attenuating effect of H276N on Ca²⁺-activated maximal tension. The rate of cross-bridge detachment (g) decreased in Tm_DM+TnT_WT and Tm_H276N+TnT_WT fibers but increased in Tm_DM+TnT_45–74Δ fibers; however, TnT_45–74Δ did not alter g, demonstrating that S229E in Tm_DM had divergent effects on g. The S229E substitution in Tm_DM ablated the H276N-induced desensitization of myofilament Ca²⁺ sensitivity in Tm_DM+TnT_1–44Δ fibers. To our knowledge, novel findings from this study show that the structural instability in the central region of Tm modifies cardiac contractile function via its effect on the overlapping ends of contiguous Tm.     

Chromosomal polymorphism in Drosophila nasuta. III. Inverted gene arrangements in South Indian populations.

Inversion polymorphism, including a total of 33 inverted gene orders, was studied in South Indian populations of D. nasuta nasuta. Of these, the X chromosome has one, chromosome 2 has 10, and chromosome 3 has 22 inversions. D. nasuta nasuta has simple, tandem, included, overlapping, and complex types of paracentrics in its polymorphic system. The phylogenetic considerations of these gene orders are discussed.     

Compression or tension? The stress distribution in the proximal femur

Background  

Questions regarding the distribution of stress in the proximal human femur have never been adequately resolved. Traditionally, by considering the femur in isolation, it has been believed that the effect of body weight on the projecting neck and head places the superior aspect of the neck in tension. A minority view has proposed that this region is in compression because of muscular forces pulling the femur into the pelvis. Little has been done to study stress distributions in the proximal femur. We hypothesise that under physiological loading the majority of the proximal femur is in compression and that the internal trabecular structure functions as an arch, transferring compressive stresses to the femoral shaft.     

Regional differences in WT-1 and Tcf21 expression during ventricular development: implications for myocardial compaction

Background

Morphological and functional differences of the right and left ventricle are apparent in the adult human heart. A differential contribution of cardiac fibroblasts and smooth muscle cells (populations of epicardium-derived cells) to each ventricle may account for part of the morphological-functional disparity. Here we studied the relation between epicardial derivatives and the development of compact ventricular myocardium.

Results

Wildtype and Wt1^CreERT2/+ reporter mice were used to study WT-1 expressing cells, and Tcf21^lacZ/+ reporter mice and PDGFRα^-/-;Tcf21^LacZ/+ mice to study the formation of the cardiac fibroblast population. After covering the heart, intramyocardial WT-1+ cells were first observed at the inner curvature, the right ventricular postero-lateral wall and left ventricular apical wall. Later, WT-1+ cells were present in the walls of both ventricles, but significantly more pronounced in the left ventricle. Tcf21-^LacZ + cells followed the same distribution pattern as WT-1+ cells but at later stages, indicating a timing difference between these cell populations. Within the right ventricle, WT-1+ and Tcf21-lacZ+ cell distribution was more pronounced in the posterior inlet part. A gradual increase in myocardial wall thickness was observed early in the left ventricle and at later stages in the right ventricle. PDGFRα^-/-;Tcf21^LacZ/+ mice showed deficient epicardium, diminished number of Tcf21-^LacZ + cells and reduced ventricular compaction.

Conclusions

During normal heart development, spatio-temporal differences in contribution of WT-1 and Tcf21-^LacZ + cells to right versus left ventricular myocardium occur parallel to myocardial thickening. These findings may relate to lateralized differences in ventricular (patho)morphology in humans.     

In silico characterization of a RNA binding protein of cattle filarial parasite Setaria digitata

Human lymphatic filariasis (HLF) is a neglected tropical disease which threatens nearly 1.4 billion people in 73 countries worldwide. Wuchereria bancrofti is the major causative agent of HLF and it closely resembles cattle filarial parasite Setaria digitata. Due to difficulties in procuring W. bancrofti parasite material, S. digitata cDNA library has been constructed to identify novel drug targets against HLF and many of the cDNA sequences are yet to be assigned structure and function. In this study, a 549 bp long cDNA (sdrbp) has been sequenced and characterized in silico. The shortest ORF of 249 bp from the isolated cDNA encodes a polypeptide of 82 amino acids and shows an amino acid identity of 54% with the RRM domain of human cleavage stimulation factor-64 kDa subunit (CstF-64). Structure of the protein (sdRBP) obtained by homology modelling using RRM of CstF-64 as template adopts classical RRM topology (β1α1β2β3α2β4). sdRBP model built was validated by superimposition tools and Ramachandran plot analysis. CstF-64 plays an important role in pre-mRNA polyadenylation by interacting with specific GU-rich downstream sequence element. Molecular docking studies of sdRBP with different RNA molecules revealed that sdRBP has greater binding affinity to GU-rich RNA and comparable results were obtained upon similar docking of RRM of CstF-64 with the same RNA molecules. Therefore, sdRBP is likely to perform homologous function in S. digitata. This study brings new dimensions to the functional analysis of RNA binding proteins of S. digitata and their evaluation as new drug targets against HLF.     

Effects of different mesenchymal stromal cell sources and delivery routes in experimental emphysema

We sought to assess whether the effects of mesenchymal stromal cells (MSC) on lung inflammation and remodeling in experimental emphysema would differ according to MSC source and administration route. Emphysema was induced in C57BL/6 mice by intratracheal (IT) administration of porcine pancreatic elastase (0.1 UI) weekly for 1 month. After the last elastase instillation, saline or MSCs (1×10⁵), isolated from either mouse bone marrow (BM), adipose tissue (AD) or lung tissue (L), were administered intravenously (IV) or IT. After 1 week, mice were euthanized. Regardless of administration route, MSCs from each source yielded: 1) decreased mean linear intercept, neutrophil infiltration, and cell apoptosis; 2) increased elastic fiber content; 3) reduced alveolar epithelial and endothelial cell damage; and 4) decreased keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8) and transforming growth factor-β levels in lung tissue. In contrast with IV, IT MSC administration further reduced alveolar hyperinflation (BM-MSC) and collagen fiber content (BM-MSC and L-MSC). Intravenous administration of BM- and AD-MSCs reduced the number of M1 macrophages and pulmonary hypertension on echocardiography, while increasing vascular endothelial growth factor. Only BM-MSCs (IV > IT) increased the number of M2 macrophages. In conclusion, different MSC sources and administration routes variably reduced elastase-induced lung damage, but IV administration of BM-MSCs resulted in better cardiovascular function and change of the macrophage phenotype from M1 to M2.