Experimental Study of Low Dose Ultrashortwave Promoting Nerve Regeneration after Acellular Nerve Allografts Repairing the Sciatic Nerve Gap of Rats

Objectives To observe the effect of ultrashortwave (USW) therapy on nerve regeneration after acellular nerve allografts(ANA) repairing the sciatic nerve gap of rats and discuss its acting mechanisms. Methods Sixteen Wistar rats weighing 180–220 g were randomly divided into four groups with four rats in each group: normal control group; acellular group (ANA, treated by hypotonic-chemical detergent, was applied for bridging a 10 mm-long sciatic nerve defect); USW group (After 24 h of ANA repairing the sciatic nerve gap, low dose USW was administrated for 7 min, once a day, 20 times a course of treatment, three courses of treatment in all); and autografts group. 12 weeks after operation, a series of examinations was performed, including electrophysiological methods, the restoring rate of tibialis anterior muscle wet weight, histopathological observation (myelinated nerve number, myelin sheath thickness, and axon diameter), vascular endothelial growth factor (VEGF) mRNA expression of spinal cord, and muscle at injury site, and analyzed statistically. Results Compared to acellular nerve allografts alone, USW therapy can increase nerve conductive velocity, the restoring rate of tibialis anterior muscle wet weight, myelinated nerve number, axon diameter, VEGF mRNA expression of spinal cord, and muscle at injury site, the difference is significant. There were no differences between USW group and autografts group except myelin sheath thickness. Conclusions USW therapy can promote nerve axon regeneration and Schwann cells proliferation after ANA repairing the sciatic nerve gap of rats, the upregulation of VEGF mRNA expression of spinal cord and muscle may play an important role.     

Amino acid variations resulting in functional and nonfunctional zebrafish P2X<Subscript>1</Subscript> and P2X<Subscript>5.1</Subscript> receptors

Several zebrafish P2X receptors (zP2X(1), zP2X(2), and zP2X(5.1)) have been reported to produce little or no current although their mammalian orthologs produce functional homomeric receptors. We isolated new cDNA clones for these P2X receptors that revealed sequence variations in each. The new variants of zP2X(1) and zP2X(5.1) produced substantial currents when expressed by Xenopus oocytes, however the new variant of zP2X(2) was still nonfunctional. zP2X(2) lacks two lysine residues essential for ATP responsiveness in other P2X receptors; however introduction of these two lysines was insufficient to allow this receptor to function as a homotrimer. We also tested whether P2X signaling is required for myogenesis or synaptic communication at the zebrafish neuromuscular junction. We found that embryonic skeletal muscle expressed only one P2X receptor, P2X(5.1). Antisense knockdown of P2X(5.1) eliminated skeletal muscle responsiveness to ATP but did not prevent myogenesis or behaviors that require functional transmission at the neuromuscular junction.     

Compositional reasoning of performance in component-based distributed systems

Rapid prototyping of distributed systems can be achieved by integrating commercial off-the-shelf (COTS) components. With components as the building blocks, it is important to predict the performance of the system based on the performance of individual components. In this paper, performance prediction of a system consisting of a small number of components is investigated under different inter-component communication patterns, and the number of threads provided by components. Based on the experimental results, it can be inferred that the proposed composition rules provide a reasonably accurate prediction of the performance of a system made out of these components.

The essential requirement of an animal heme peroxidase protein during the wing maturation process in Drosophila

Background

Thus far, a handful of genes have been shown to be related to the wing maturation process in insects. A novel heme peroxidase enzyme known as curly suppressor (Cysu)(formerly CG5873), have been characterized in this report because it is involved in wing morphogenesis. Using bioinformatics tools we found that Cysu is remarkably conserved in the genus Drosophila (>95%) as well as in invertebrates (>70%), although its vertebrate orthologs show poor homology. Time-lapse imaging and histochemical analyses have confirmed that the defective wing phenotype of Cysu is not a result of any underlying cellular alterations; instead, its wings fail to expand in mature adults.

Results

The precise requirement of Cysu in wings was established by identifying a bona fide mutant of Cysu from the Bloomington Drosophila Stock Centre collection. Its requirement in the wing has also been shown by RNA knockdown of the gene. Subsequent transgenic rescue of the mutant wing phenotype with the wild-type gene confirmed the phenotype resulting from Cysu mutant. With appropriate GAL4 driver like engrailed-GAL4, the Cysu phenotype was compartmentalized, which raises a strong possibility that Cysu is not localized in the extracellular matrix (ECM); hence, Cysu is not engaged in bonding the dorsal and ventral cuticular layers. Finally, shortened lifespan of the Cysu mutant suggests it is functionally essential for other biological processes as well.

Conclusion

Cysu, a peroxinectin-like gene, is required during the wing maturation process in Drosophila because as a heme peroxidase, Cysu is capable of utilizing H₂O₂, which plays an essential role in post-eclosion wing morphogenesis.

     

Altered expression of flowering class B and class C genes in the Appendix tobacco mutant

 In the tobacco (Nicotiana tabacum) Appendix mutant, anthers are tipped by a miniature style and stigma. The outgrowth appears on the anther when it is already differentiating and follows the developmental timing of the central carpel. The Appendix mutation thus represents a late homeotic transformation suggesting that the APPENDIX (APX) gene either could be a misregulated organ identity gene or could be involved in regulating the expression of such genes. RFLP analysis with two class B (TM6 and NTGLO) and a class C (NAG) probes revealed that the Appendix phenotype is not caused by a mutation in one of these genes. However, in situ hybridization showed important changes in the expression of NTGLO and NAG in the mutant when compared with wild-type tobacco. Surprisingly, although no phenotypic alteration other than the style and stigma outgrowth is observed in the Appendix mutant, changes in class B and class C gene expession were not restricted to the anther tip cells from which the outgrowth originates. As expected, NAG was expressed in the Appendix outgrowth but it was also overexpressed in the normal third and fourth whorl organs at the time the outgrowth, as well as the central styles and stigmas, differentiated. Overexpression of a class C gene is probably responsible for the Appendix phenotype. In normal and mutant flowers, NTGLO was expressed in the second, third and fourth whorls up to the time of carpel fusion. Expression of this class B gene then ceased in the fourth whorl organs but was reactivated at later stages only in the styles and stigmas as well as in the outgrowths of the mutant. It thus seems that the function of the APX gene is either to regulate the late expression of organ identity genes or to control cell proliferation in such a way that, in the mutant, some cells are in a state where they respond in an unusual way to developmental signals. Received: 17 October 1997 / Revision accepted: 24 March 1998     

Palmitate acutely raises glycogen synthesis in rat soleus muscle by a mechanism that requires its metabolization (Randle cycle)

The acute effect of palmitate on glucose metabolism in rat skeletal muscle was examined. Soleus muscles from Wistar male rats were incubated in Krebs-Ringer bicarbonate buffer, for 1 h, in the absence or presence of 10 mU/ml insulin and 0, 50 or 100 microM palmitate. Palmitate increased the insulin-stimulated [(14)C]glycogen synthesis, decreased lactate production, and did not alter D-[U-(14)C]glucose decarboxylation and 2-deoxy-D-[2,6-(3)H]glucose uptake. This fatty acid decreased the conversion of pyruvate to lactate and [1-(14)C]pyruvate decarboxylation and increased (14)CO(2) produced from [2-(14)C]pyruvate. Palmitate reduced insulin-stimulated phosphorylation of insulin receptor substrate-1/2, Akt, and p44/42 mitogen-activated protein kinases. Bromopalmitate, a non-metabolizable analogue of palmitate, reduced [(14)C]glycogen synthesis. A strong correlation was found between [U-(14)C]palmitate decarboxylation and [(14)C]glycogen synthesis (r=0.99). Also, palmitate increased intracellular content of glucose 6-phosphate in the presence of insulin. These results led us to postulate that palmitate acutely potentiates insulin-stimulated glycogen synthesis by a mechanism that requires its metabolization (Randle cycle). The inhibitory effect of palmitate on insulin-stimulated protein phosphorylation might play an important role for the development of insulin resistance in conditions of chronic exposure to high levels of fatty acids.     

Biotic and Abiotic Drivers of Peatland Growth and Microtopography: A Model Demonstration

Peatlands are important carbon reserves in terrestrial ecosystems. The microtopography of a peatland area has a strong influence on its carbon balance, determining carbon fluxes at a range of spatial scales. These patterned surfaces are very sensitive to changing climatic conditions. There are open research questions concerning the stability, behaviour and transformation of these microstructures, and the implications of these changes for the long-term accumulation of organic matter in peatlands. A simple two-dimensional peat microtopographical model was developed, which accounts for the effects of microtopographical variations and a dynamic water table on competitive interactions between peat-forming plants. In a case study of a subarctic mire in northern Sweden, we examined the consequences of such interactions on peat accumulation patterns and the transformation of microtopographical structure. The simulations demonstrate plausible interactions between peatland growth, water table position and microtopography, consistent with many observational studies, including an observed peat age profile from the study area. Our model also suggests that peatlands could exhibit alternative compositional and structural dynamics depending on the initial topographical and climatic conditions, and plant characteristics. Our model approach represents a step towards improved representation of peatland vegetation dynamics and net carbon balance in Earth system models, allowing their potentially important implications for regional and global carbon balances and biogeochemical and biophysical feedbacks to the atmosphere to be explored and quantified.     

Variability in the settlement of non-indigenous species in benthic communities from an oceanic island

The introduction of non-indigenous species (NIS) in new environments represents a major threat for coastal ecosystems. A good understanding of the mechanisms and magnitude of the impact of NIS colonisation on native ecosystems is becoming increasingly crucial to develop mitigation measures and prevent new invasions. In this present study, we asked if distinct coastal benthic communities from an oceanic island can have different vulnerability to NIS colonisation process. First, PVC settlement plates were deployed for 1 year on the rocky shore of two different locations of Madeira Island (North versus South coast). Then, we implemented a mesocosm experiment where recruited plate communities were maintained under different levels of NIS propagule pressure in order to assess their vulnerability to NIS colonisation process. Results showed that NIS colonisation success was not influenced by the level of propagule pressure, but however, final colonisation patterns varied depending on the origin of the communities. This variability can be attributed to major structural differences between the preponderant species of each community and therefore to the biotic substrate they offer to colonisers. This study highlights how biotic features can alter the NIS colonisation process and importantly, shows that in an urbanisation context, the nature of the resident communities facing invasions risks needs to be closely assessed.     

Bottom-up approaches in synthetic biology and biomaterials for tissue engineering applications

Synthetic biologists use engineering principles to design and construct genetic circuits for programming cells with novel functions. A bottom-up approach is commonly used to design and construct genetic circuits by piecing together functional modules that are capable of reprogramming cells with novel behavior. While genetic circuits control cell operations through the tight regulation of gene expression, a diverse array of environmental factors within the extracellular space also has a significant impact on cell behavior. This extracellular space offers an addition route for synthetic biologists to apply their engineering principles to program cell-responsive modules within the extracellular space using biomaterials. In this review, we discuss how taking a bottom-up approach to build genetic circuits using DNA modules can be applied to biomaterials for controlling cell behavior from the extracellular milieu. We suggest that, by collectively controlling intrinsic and extrinsic signals in synthetic biology and biomaterials, tissue engineering outcomes can be improved.