Aims
Focal knee arthroplasty is an attractive alternative to knee arthroplasty for young patients because it allows preservation of a large amount of bone for potential revisions. However, the ...mechanical behaviour of cartilage has not yet been investigated because it is challenging to evaluate in vivo contact areas, pressure, and deformations from metal implants. Therefore, this study aimed to determine the contact pressure in the tibiofemoral joint with a focal knee arthroplasty using a finite element model.
Methods
The mechanical behaviour of the cartilage surrounding a metal implant was evaluated using finite element analysis. We modelled focal knee arthroplasty with placement flush, 0.5 mm deep, or protruding 0.5 mm with regard to the level of the surrounding cartilage. We compared contact stress and pressure for bone, implant, and cartilage under static loading conditions.
Results
Contact stress on medial and lateral femoral and tibial cartilages increased and decreased, respectively, the most and the least in the protruding model compared to the intact model. The deep model exhibited the closest tibiofemoral contact stress to the intact model. In addition, the deep model demonstrated load sharing between the bone and the implant, while the protruding and flush model showed stress shielding. The data revealed that resurfacing with a focal knee arthroplasty does not cause increased contact pressure with deep implantation. However, protruding implantation leads to increased contact pressure, decreased bone stress, and biomechanical disadvantage in an in vivo application.
Conclusion
These results show that it is preferable to leave an edge slightly deep rather than flush and protruding.
Cite this article:
Bone Joint Res
2023;12(8):497–503.
Theoretical studies have suggested relationships between the size, stability and topology of a protein fold and the rate and mechanisms by which it is achieved. The recent characterization of the ...refolding of a number of simple, single domain proteins has provided a means of testing these assertions. Our investigations have revealed statistically significant correlations between the average sequence separation between contacting residues in the native state and the rate and transition state placement of folding for a non-homologous set of simple, single domain proteins. These indicate that proteins featuring primarily sequence-local contacts tend to fold more rapidly and exhibit less compact folding transition states than those characterized by more non-local interactions. No significant relationship is apparent between protein length and folding rates, but a weak correlation is observed between length and the fraction of solvent-exposed surface area buried in the transition state. Anticipated strong relationships between equilibrium folding free energy and folding kinetics, or between chemical denaturant and temperature dependence-derived measures of transition state placement, are not apparent. The observed correlations are consistent with a model of protein folding in which the size and stability of the polypeptide segments organized in the transition state are largely independent of protein length, but are related to the topological complexity of the native state. The correlation between topological complexity and folding rates may reflect chain entropy contributions to the folding barrier.
IZUMO1, belonging to the family of mammalian immunoglobulin proteins, has been well characterized in the mouse. Here, we describe the molecular cloning and expression analysis of porcine IZUMO1 ...(pIZUMO1). Partial sequence information published in the National Center for Biotechnology Information (NCBI) database was used to generate the full‐length sequence for IZUMO1 using rapid amplification of cDNA ends (RACE). A search of the porcine genomic sequence in the NCBI database identified a bacterial artificial chromosome (BAC) encoding the pIZUMO1 gene. This BAC is derived from porcine chromosome 6 and is syntenic with the corresponding regions of mouse, bovine, and human genomes encoding the IZUMO gene family. This BAC was found to encode an IZUMO1 protein with a predicted amino acid sequence having high similarity with mouse and human IZUMO1. Western blot analysis of proteins from porcine tissues indicated that pIZUMO1 was specifically expressed in the sperm. Furthermore, to confirm whether pIZUMO1 forms complexes, we overexpressed pIZUMO1 in HEK293 cells. The recombinant pIZUMO1 from cell extracts was found to form complexes. Our finding suggests that pIZUMO1 forms homodimeric complex on the sperm membrane. Furthermore, an IVF inhibition assay with an antibody for the porcine IZUMO1 Ig‐like domain showed that Ig‐like domain effectively prevented pig sperm–egg interactions.
Monitoring landscape carbon storage is critical for supporting and validating climate change mitigation policies. These may be aimed at reducing deforestation and degradation, or increasing ...terrestrial carbon storage at local, regional and global levels. However, due to data-deficiencies, default global carbon storage values for given land cover types such as 'lowland tropical forest' are often used, termed 'Tier 1 type' analyses by the Intergovernmental Panel on Climate Change (IPCC). Such estimates may be erroneous when used at regional scales. Furthermore uncertainty assessments are rarely provided leading to estimates of land cover change carbon fluxes of unknown precision which may undermine efforts to properly evaluate land cover policies aimed at altering land cover dynamics. Here, we present a repeatable method to estimate carbon storage values and associated 95% confidence intervals (CI) for all five IPCC carbon pools (aboveground live carbon, litter, coarse woody debris, belowground live carbon and soil carbon) for data-deficient regions, using a combination of existing inventory data and systematic literature searches, weighted to ensure the final values are regionally specific. The method meets the IPCC 'Tier 2' reporting standard. We use this method to estimate carbon storage over an area of33.9 million hectares of eastern Tanzania, reporting values for 30 land cover types. We estimate that this area stored 6.33 (5.92-6.74) Pg C in the year 2000. Carbon storage estimates for the same study area extracted from five published Africa-wide or global studies show a mean carbon storage value of ∼50% of that reported using our regional values, with four of the five studies reporting lower carbon storage values. This suggests that carbon storage may have been underestimated for this region of Africa. Our study demonstrates the importance of obtaining regionally appropriate carbon storage estimates, and shows how such values can be produced for a relatively low investment.
Multiple aspects of cornea development, including the innervation of the cornea by trigeminal axons, are sensitive to embryonic levels of thyroid hormone (TH). Although previous work showed that ...increased TH levels could enhance the rate of axonal extension within the cornea in a thyroxine (T4)-dependent manner, details underlying the stimulatory effect of TH on cornea innervation are unclear. Here, by examining the effects throughout all stages of cornea innervation of the two main THs, triiodothyronine (T3) and T4, we provide a more complete characterization of the stimulatory effects of TH on corneal nerves and begin to unravel the underlying molecular mechanisms. During development, trigeminal axons are initially repelled at the corneal periphery and encircle the cornea in a pericorneal nerve ring prior to advancing into the corneal stroma radially from all along the nerve ring. Overall, exogenous T3 led to pleiotropic effects throughout all stages of cornea innervation, whereas the effects of exogenous T4 was confined to timepoints following completion of the nerve ring. Specifically, exogenous T3 accelerated the formation of the pericorneal nerve ring. By utilizing in vitro neuronal explants studies we demonstrated that T3 acts as a trophic factor to directly stimulate trigeminal nerve growth. Further, exogenous T3 caused disorganized and precocious innervation of the cornea, accompanied by the downregulation of inhibitory Robo receptors that normally act to regulate the timing of nerve advancement into the Slit-expressing corneal tissues. Following nerve ring completion, the growth rate and branching behavior of nerves as they advanced into and through the cornea were found to be stimulated equally by T3 or T4. These stimulatory influences of T3/T4 over nerves likely arose as secondary consequences brought on by TH-mediated modulations to the corneal extracellular matrix. Specifically, we found that the levels of nerve-inhibitory keratan- and chondroitin-sulfate containing proteoglycans and associated sulfation enzymes were dramatically altered in the presence of exogenous T3 or T4. Altogether, these findings uncover new roles for TH on corneal development and shed insight into the mechanistic basis of both T3 and T4 on cornea innervation.
•Pericorneal nerve ring formation was accelerated and corneas became precociously innerved in T3-treated embryos.•T3 acts as a trophic factor to directly stimulate trigeminal nerve growth.•Robo/Slit pathway expression is reduced in eyefronts following T3 exposure.•Growth rate and defasciculation of nerves increased within T3 or T4-treated corneas.•KSPG/CSPG and sulfation enzyme levels were modulated in T3 and T4-treated corneas.
We report a search for X ( 3872 ) and X ( 3915 ) in B+ → χc1π0K+ decays. We set an upper limit of B ( B+ → X ( 3872 ) K+ ) × B ( X ( 3872 ) → χc1π0 ) <8.1×10-6 and B ( B+ → X ( 3915 ) K+ ) × B ( X ( ...3915 ) → χc1π0 ) <3.8×10-5 at 90% confidence level. We also measure B ( X ( 3872 ) → χc1π0 ) / B ( X ( 3872 ) → J / ψπ+π- ) <0.97 at 90% confidence level. The results reported here are obtained from 772×106 B B ¯ events collected at the Υ ( 4S ) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
A series of experiments were performed to provide validation data for explosively driven multiphase flows at moderate-to-high volume fractions. A
13
×
6
mm cylindrical packet of 115-
μ
m steel ...particles was dispersed explosively. In contrast to shock tube studies, the particles were subjected to a high-Mach-number shock, in the presence of an ambient fluid, and a contact interface between the ambient and the explosive products. The first five experiments lowered the global volume fraction by replacing portions of the particle bed with hollow glass microspheres, dispersing the particles into vacuum. Three global fractions were investigated: 60%, 40%, and 20%. The next five experiments did not lower the volume fraction but instead varied the ambient fluid. Three ambient fluids were investigated: air, xenon, and SF
6
. To penetrate the optically opaque explosive products present and track the dispersed particle cloud, proton radiography was performed. The high-volume-fraction cases exhibit a piston-like motion for all ambient conditions, with an increasingly stochastic motion present for the lower volume fractions. Particle fronts extracted from the transmission radiographs exhibit almost constant velocity. Furthermore, centerline particle fronts for the high-volume-fraction cases, with both vacuum and varying ambient gas conditions, were almost the same, suggesting the primary impulse to particle bed motion arises from the contact interface between the ambient and the detonation products. Lower volume fractions were accelerated to higher velocities, behaving as though they were a single object of decreased density being acted on by a force of constant magnitude.
Effects of porosity of catalyst layers (CLs) on direct methanol fuel cell (DMFC) performances are investigated using silicon dioxide (SiO2) particles as a pore former. The pore size and volume of CLs ...are controlled by changing the size and content of SiO2. As the size of pore formed by removal of SiO2 increases, DMFC performances are enhanced. The augmentation in performances can be explained by facilitation of fuel transport to catalyst particles, increase of utilization efficiency of catalysts, diminishment in methanol crossover, reduction in activation loss and facilitation of water discharging out of CLs of cathode due to the controlled porosity in CLs. The enhanced fuel transport, accessibility of fuels to Pt catalyst surface, is proved by the active areas of Pt catalyst. In addition to the active area of Pt catalyst, porous CLs exhibit a decline in methanol crossover, leading to increase of open circuit voltage (OCV). The porous CLs also show improvements in activation loss due to high porosity, causing enhancement in DMFC performances. In aspect of pore volume contribution to cathode performance, the SiO2 content is optimized. Based on the DMFC performances, it can be suggested that the optimum conditions of SiO2 are 500 nm in size and 20 wt.% in content. The porosity effect on both electrodes appears as follows: the pores in cathode are more effective on DMFC performances (55.5%) than those of anodes (44.5%) based on the maximum power of DMFC, indicating that the pores in CLs facilitate removal of water from electrodes.
Transforming growth factor (TGF)- beta 1 has biphasic functions in prostate tumorigenesis, having a growth-inhibitory effect in the early stages, but in the late stages promoting tumor angiogenesis ...and metastasis. We demonstrate here that tumor-producing TGF- beta 1 induces vascular endothelial growth factor (VEGF) in prostate cancer cells, and hypoxia-inducible factor (HIF)-1 alpha and HIF-2 alpha has opposite functions in TGF- beta 1 regulation of VEGF expression under non-hypoxic conditions. The promoter response of VEGF to TGF- beta 1 was upregulated by the transfection of HIF-2 alpha or siHIF-1 alpha but downregulated by HIF-1 alpha and siHIF-2 alpha . Both HIF-1 alpha and HIF-2 alpha were induced by TGF- beta 1 at mRNA and protein levels, however, their nuclear translocation was differentially regulated by TGF- beta 1, suggesting its association with their opposite effects. VEGF induction by TGF- beta 1 occurred in a Smad3-dependent manner, and the Smad-binding element 2 (SBE2, -992 to -986) and hypoxia response element (-975 to -968) in the VEGF promoter were required for the promoter response to TGF- beta 1. Smad3 cooperated with HIF-2 alpha in TGF- beta 1 activation of VEGF transcription and Smad3 binding to the SBE2 site was greatly impaired by knockdown of HIF-2 alpha expression. Moreover, the VEGF promoter response to TGF- beta 1 was synergistically elevated by co-transfection of Smad3 and HIF-2 alpha but attenuated by HIF-1 alpha in a dose-dependent manner. Additionally, TGF- beta 1 was found to increase the stability of VEGF transcript by facilitating the cytoplasmic translocation of a RNA-stabilizing factor HuR. Collectively, our data show that tumor-producing TGF- beta 1 induces VEGF at the both transcription and post-transcriptional levels through multiple routes including Smad3, HIF-2 alpha and HuR. This study thus suggests that autocrine TGF- beta 1 production may contribute to tumor angiogenesis via HIF-2 alpha signaling under non-hypoxic conditions, providing a selective growth advantage for prostate tumor cells.
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