Experimental Study about Intraosseous Blood Flow and Bone Volume in Tail-suspended Rat Model

尾部懸垂ラットにおける, 下肢骨髄内血流の変化と, 骨塩量, および骨形態計測パラメーターの変化の関係を検討した。さらに, 骨粗鬆症治療薬の一つであるエルカトニンを投与し, 骨髄内血流の変化を観察した。 水素クリアランス法を用いて脛骨近位部の骨髄内血流を測定した後反対側の脛骨近位部を摘出し, 骨塩量濃度(BMD), マイクロCT装置(μ-CT), 組織学的骨形態計測を行った。さらにエルカトニン投与尾部懸垂ラットについても同様の検査を行った。これらによって, 以下の結論を得た。 1)尾部懸垂ラットの脛骨近位部骨髄内血流量は, 懸垂5日群から有意に低下していた。 2)尾部懸垂ラットでは, 早期の段階から特に骨吸収を示すパラメータの有意な上昇が見られたが, 統計学的に有意に骨髄内血流量と相関していたのは, μ-CT検査におけるMean Intercept Length(MIL)のみであった。 3)エルカトニン投与尾部懸垂ラットでは, 溶媒投与群と比べて有意に骨髄内血流量が上昇していた。 4)尾部懸垂ラットにおいて, 骨髄内血流が骨吸収を抑制することによって骨リモデリングに影響している可能性があり, エルカトニン投与における骨髄内血流量増加が, 骨吸収を抑制することによって骨量低下を抑制している可能性が示唆された。We measured intraosseous blood flow of proximal tibia with the hydrogen washout technique, after that, we excised the opposite side tibia for measuring the BMD with DXA, and morphologic parameters with micro-CT, and histological morphologic parameters. And we measured the same way in the Elcatonin-administrated tail-suspended rats. Our conclusions are : 1) The intraosseous blood flow in the tail-suspended rat was statistically lower than the control rat even the 5-day suspension group. 2) Increase of the absorption parameter was observed in the early phase of the tail-suspension, but there is no statistically relationships between the blood flow and the morphological parameters without MIL. 3) Elcatonin administration made intraosseous blood flow increase in the tail-suspended rat. 4) Intraosseous blood flow may give the influence bone remodeling by restraint of the bone absorption, and increase of the intraosseous blood flow when Elcatonin was administrated may reduce the lowerness of the bone volume by restraint of the bone absorption

Simulation of reaction-diffusion processes in three dimensions using CUDA

Numerical solution of reaction-diffusion equations in three dimensions is one of the most challenging applied mathematical problems. Since these simulations are very time consuming, any ideas and strategies aiming at the reduction of CPU time are important topics of research. A general and robust idea is the parallelization of source codes/programs. Recently, the technological development of graphics hardware created a possibility to use desktop video cards to solve numerically intensive problems. We present a powerful parallel computing framework to solve reaction-diffusion equations numerically using the Graphics Processing Units (GPUs) with CUDA. Four different reaction-diffusion problems, (i) diffusion of chemically inert compound, (ii) Turing pattern formation, (iii) phase separation in the wake of a moving diffusion front and (iv) air pollution dispersion were solved, and additionally both the Shared method and the Moving Tiles method were tested. Our results show that parallel implementation achieves typical acceleration values in the order of 5-40 times compared to CPU using a single-threaded implementation on a 2.8 GHz desktop computer.Comment: 8 figures, 5 table

High-frequency affine mechanics and nonaffine relaxation in a model cytoskeleton

The cytoskeleton is a network of crosslinked, semiflexible filaments, and it has been suggested that it has properties of a glassy state. Here we employ optical-trap-based microrheology to apply forces to a model cytoskeleton and measure the high-bandwidth response at an anterior point. Simulating the highly nonlinear and anisotropic stress-strain propagation assuming affinity, we found that theoretical predictions for the quasistatic response of semiflexible polymers are only realized at high frequencies inaccessible to conventional rheometers. We give a theoretical basis for determining the frequency when both affinity and quasistaticity are valid, and we discuss with experimental evidence that the relaxations at lower frequencies can be characterized by the experimentally obtained nonaffinity parameter

Aberrant behaviours of reaction diffusion self-organisation models on growing domains in the presence of gene expression time delays

Turing’s pattern formation mechanism exhibits sensitivity to the details of the initial conditions suggesting that, in isolation, it cannot robustly generate pattern within noisy biological environments. Nonetheless, secondary aspects of developmental self-organisation, such as a growing domain, have been shown to ameliorate this aberrant model behaviour. Furthermore, while in-situ hybridisation reveals the presence of gene expression in developmental processes, the influence of such dynamics on Turing’s model has received limited attention. Here, we novelly focus on the Gierer–Meinhardt reaction diffusion system considering delays due the time taken for gene expression, while incorporating a number of different domain growth profiles to further explore the influence and interplay of domain growth and gene expression on Turing’s mechanism. We find extensive pathological model behaviour, exhibiting one or more of the following: temporal oscillations with no spatial structure, a failure of the Turing instability and an extreme sensitivity to the initial conditions, the growth profile and the duration of gene expression. This deviant behaviour is even more severe than observed in previous studies of Schnakenberg kinetics on exponentially growing domains in the presence of gene expression (Gaffney and Monk in Bull. Math. Biol. 68:99–130, 2006). Our results emphasise that gene expression dynamics induce unrealistic behaviour in Turing’s model for multiple choices of kinetics and thus such aberrant modelling predictions are likely to be generic. They also highlight that domain growth can no longer ameliorate the excessive sensitivity of Turing’s mechanism in the presence of gene expression time delays. The above, extensive, pathologies suggest that, in the presence of gene expression, Turing’s mechanism would generally require a novel and extensive secondary mechanism to control reaction diffusion patterning

Perturbation analysis of a multi-morphogen Turing reaction-diffusion stripe patterning system reveals key regulatory interactions

Periodic patterning is widespread in development and can be modelled by reaction-diffusion (RD) processes. However, minimal two-component RD descriptions are vastly simpler than the multi-molecular events that actually occur and are often hard to relate to real interactions measured experimentally. Addressing these issues, we investigated the periodic striped patterning of the rugae (transverse ridges) in the mammalian oral palate, focusing on multiple previously implicated pathways: FGF, Hh, Wnt and BMP. For each, we experimentally identified spatial patterns of activity and distinct responses of the system to inhibition. Through numerical and analytical approaches, we were able to constrain substantially the number of network structures consistent with the data. Determination of the dynamics of pattern appearance further revealed its initiation by ‘activators’ FGF and Wnt, and ‘inhibitor’ Hh, whereas BMP and mesenchyme-specific-FGF signalling were incorporated once stripes were formed. This further limited the number of possible networks. Experimental constraint thus limited the number of possible minimal networks to 154, just 0.004% of the number of possible diffusion-driven instability networks. Together, these studies articulate the principles of multi-morphogen RD patterning and demonstrate the utility of perturbation analysis for constraining RD systems. This article has an associated ‘The people behind the papers’ interview

Application of a Simplified Method of Chloroplast Enrichment to Small Amounts of Tissue for Chloroplast Genome Sequencing

Premise of the study: High-throughput sequencing of genomic DNA can recover complete chloroplast genome sequences, but the sequence data are usually dominated by sequences from nuclear/mitochondrial genomes. To overcome this deficiency, a simple enrichment method for chloroplast DNA from small amounts of plant tissue was tested for eight plant species including a gymnosperm and various angiosperms. Methods: Chloroplasts were enriched using a high-salt isolation buffer without any step gradient procedures, and enriched chloroplast DNA was sequenced by multiplexed high-throughput sequencing. Results: Using this simple method, significant enrichment of chloroplast DNA-derived reads was attained, allowing deep sequencing of chloroplast genomes. As an example, the chloroplast genome of the conifer Callitris sulcata was assembled, from which polymorphic microsatellite loci were isolated successfully. Discussion: This chloroplast enrichment method from small amounts of plant tissue will be particularly useful for studies that use sequencers with relatively small throughput and that cannot use large amounts of tissue (e.g., for endangered species)

Turing patterns on networks

Turing patterns formed by activator-inhibitor systems on networks are considered. The linear stability analysis shows that the Turing instability generally occurs when the inhibitor diffuses sufficiently faster than the activator. Numerical simulations, using a prey-predator model on a scale-free random network, demonstrate that the final, asymptotically reached Turing patterns can be largely different from the critical modes at the onset of instability, and multistability and hysteresis are typically observed. An approximate mean-field theory of nonlinear Turing patterns on the networks is constructed.Comment: 4 pages, 4 figure

Polyamine sensitivity of gap junctions is required for skin pattern formation in zebrafish

Gap junctions allow the direct and bidirectional transfer of small molecules between cells. Polyamine sensitivity, which has been observed for a certain gap junction in vitro, confers rectification property to gap junction. Here we report that the polyamine sensitivity of gap junctions in vivo is crucial for skin pattern formation in zebrafish. Transgenic experiments have revealed that several connexin genes were able to rescue the spot phenotype of mutant zebrafish. Mutational analyses of the N-terminal region of connexins revealed that the ExxxE motif, a hypothetical polyamine-binding site, was important for connexin's role in pattern formation. Ectopic expression of spermidine/spermine N1-acetyltransferase (SSAT), a polyamine metabolic enzyme, also caused stripe pattern changes, which further indicates that the polyamine sensitivity of gap junctions is crucial. This is the first report to show that polyamine sensitivity has a physiologically relevant function and is related to skin pattern formation in animals