Rocking-horse phenomenon of the glenoid component: the importance of inclination.

BACKGROUND: Abnormal glenoid version positioning has been recognized as a cause of glenoid component failure caused by the rocking horse phenomenon. In contrast, the importance of the glenoid inclination has not been investigated. MATERIALS AND METHODS: The computed tomography scans of 152 healthy shoulders were evaluated. A virtual glenoid component was positioned in 2 different planes: the maximum circular plane (MCP) and the inferior circle plane (ICP). The MCP was defined by the best fitting circle of the most superior point of the glenoid and 2 points at the lower glenoid rim. The ICP was defined by the best fitting circle on the rim of the inferior quadrants. The inclination of both planes was measured as the intersection with the scapular plane. We defined the force vector of the rotator force couple and calculated the magnitude of the shear force vector on a virtual glenoid component in both planes during glenohumeral abduction. RESULTS: The inclination of the component positioned in the MCP averaged 95° (range, 84°-108°) and for the ICP averaged 111° (range, 94°-126°). A significant reduction in shear forces was calculated for the glenoid component in the ICP vs the MCP: 98% reduction in 60° of abduction to 49% reduction in 90° of abduction. CONCLUSION: Shear forces are significantly higher when the glenoid component is positioned in the MCP compared with the ICP, and this is more pronounced in early abduction. Positioning the glenoid component in the inferior circle might reduce the risk of a rocking horse phenomenon.

The rotavirus nonstructural protein NSP5 coordinates a [2Fe-2S] iron-sulfur cluster that modulates interaction to RNA.

During rotavirus infection, replication and packaging of the viral genome occur in viral factories, termed viroplasms. The viral nonstructural protein NSP5 is a major building block of viroplasms; it recruits the viral polymerase VP1, the core protein VP2, and the ATPase NSP2 inside the viroplasm to form the viral replication complex. Here we report that NSP5 is a unique viral metalloprotein that coordinates a [2Fe-2S] iron-sulfur cluster as demonstrated by the metal and labile sulfide contents, UV-visible light absorption, and electron paramagnetic resonance. Point mutations in NSP5 allowed us to identify C171 and C174, arranged in a CXC motif, as essential residues for cluster coordination. When coexpressed with NSP2, an NSP5 mutant devoid of the iron-sulfur cluster still forms viroplasm-like structures. The cluster is therefore neither involved in the interaction with NSP2 nor in the formation of viroplasm-like structures and thus presumably in viroplasm formation. Finally, we show using microscale thermophoresis that the iron-sulfur cluster modulates the affinity of NSP5 for single-stranded RNA. Because the cluster is near the binding sites of both the polymerase VP1 and the ATPase NSP2, we anticipate that this cluster is crucial for NSP5 functions, in either packaging or replication of the viral genome.

Canonical initiation factor requirements of the Myc family of internal ribosome entry segments.

Initiation of protein synthesis in eukaryotes requires recruitment of the ribosome to the mRNA and its translocation to the start codon. There are at least two distinct mechanisms by which this process can be achieved; the ribosome can be recruited either to the cap structure at the 5' end of the message or to an internal ribosome entry segment (IRES), a complex RNA structural element located in the 5' untranslated region (5'-UTR) of the mRNA. However, it is not well understood how cellular IRESs function to recruit the ribosome or how the 40S ribosomal subunits translocate from the initial recruitment site on the mRNA to the AUG initiation codon. We have investigated the canonical factors that are required by the IRESs found in the 5'-UTRs of c-, L-, and N-myc, using specific inhibitors and a tissue culture-based assay system, and have shown that they differ considerably in their requirements. The L-myc IRES requires the eIF4F complex and the association of PABP and eIF3 with eIF4G for activity. The minimum requirements of the N- and c-myc IRESs are the C-terminal domain of eIF4G to which eIF4A is bound and eIF3, although interestingly this protein does not appear to be recruited to the IRES RNA via eIF4G. Finally, our data show that all three IRESs require a ternary complex, although in contrast to c- and L-myc IRESs, the N-myc IRES has a lesser requirement for a ternary complex.

Modeling rotavirus-like particles production in a baculovirus expression vector system: Infection kinetics, baculovirus DNA replication, mRNA synthesis and protein production.

Rotavirus is the most common cause of severe diarrhoea in children worldwide, responsible for more than half a million deaths in children per year. Rotavirus-like particles (Rota VLPs) are excellent vaccine candidates against rotavirus infection, since they are non-infectious, highly immunogenic, amenable to large-scale production and safer to produce than those based on attenuated viruses. This work focuses on the analysis and modeling of the major events taking place inside Spodoptera frugiperda (Sf-9) cells infected by recombinant baculovirus that may be critical for the expression of rotavirus viral proteins (VPs). For model validation, experiments were performed adopting either a co-infection strategy, using three monocistronic recombinant baculovirus each one coding for viral proteins VP(2), VP(6) and VP(7), or single-infection strategies using a multigene baculovirus coding for the three proteins of interest. A characteristic viral DNA (vDNA) replication rate of 0.19+/-0.01 h(-1) was obtained irrespective of the monocistronic or multigene vector employed, and synthesis of progeny virus was found to be negligible in comparison to intracellular vDNA concentrations. The timeframe for vDNA, mRNA and VP synthesis tends to decrease with increasing multiplicity of infection (MOI) due to the metabolic burden effect. The protein synthesis rates could be ranked according to the gene size in the multigene experiments but not in the co-infection experiments. The model exhibits acceptable prediction power of the dynamics of intracellular vDNA replication, mRNA synthesis and VP production for the three proteins involved. This model is intended to be the basis for future Rota VLPs process optimisation and also a means to evaluating different baculovirus constructs for Rota VLPs production.