Probing the geochemical characteristics of rare earth elements in the weathering profile of yttrium-rich heavy rare earth mine.

Understanding the complex geochemical characteristics of rare earth elements (REEs) in the weathering profile of ion-adsorbed rare earth ore is a crucial issue for establishing the best leaching agent dosage during in-situ leaching processes. This study focuses on soil samples collected from nine drill holes located at three hillslopes of a mining area in southwest Fujian. Analyzing the geochemical features of REEs revealed that the ore predominantly comprises Y, La, Ce, and Nd, with Y being the most abundant, constituting 20.24 %-33.64 % of total rare earth elements (TREEs) in each weathering profile. This categorizes the ore as an yttrium-rich heavy rare earth ion-adsorbed mine. Notably, REEs exhibit a concentration in the middle layer of the weathering profile, with content increasing first and then declining with deeper depth from the surface to the bottom. The ratio of light rare earth elements (LREEs) to heavy rare earth elements (HREEs) diminishes noticeably from shallow soil to middle soil, while deep soil reveals a slightly higher ratio than middle soil. These findings offer valuable insights into the scientific mining of this area and similar ion-adsorbed rare earth mines concerning their economic potential.

Genome-Wide Association Study Uncovers Genomic Regions Associated with Coleoptile Length in a Worldwide Collection of Oat.

The length of coleoptile is crucial for determining the sowing depth of oats in low-precipitation regions, which is significant for oat breeding programs. In this study, a diverse panel of 243 oat accessions was used to explore coleoptile length in two independent experiments. The panel exhibited significant variation in coleoptile length, ranging from 4.66 to 8.76 cm. Accessions from Africa, America, and the Mediterranean region displayed longer coleoptile lengths than those from Asia and Europe. Genome-wide association studies (GWASs) using 26,196 SNPs identified 34 SNPs, representing 32 quantitative trait loci (QTLs) significantly associated with coleoptile length. Among these QTLs, six were consistently detected in both experiments, explaining 6.43% to 10.07% of the phenotypic variation. The favorable alleles at these stable loci additively increased coleoptile length, offering insights for pyramid breeding. Gene Ontology (GO) analysis of the 350 candidate genes underlying the six stable QTLs revealed significant enrichment in cell development-related processes. Several phytochrome-related genes, including auxin transporter-like protein 1 and cytochrome P450 proteins, were found within these QTLs. Further validation of these loci will enhance our understanding of coleoptile length regulation. This study provides new insights into the genetic architecture of coleoptile length in oats.

Genome-Wide Association Mapping of QTL Underlying Groat Protein Content of a Diverse Panel of Oat Accessions.

Groat protein content (GPC) is a key quality trait attribute in oat. Understanding the variation of GPC in oat germplasms and identifying genomic regions associated with GPC are essential for improving this trait. In this study, the GPC of 174 diverse oat accessions was evaluated in three field trials. The results showed a wide variation in GPC, ranging from 6.97% to 22.24% in this panel. Hulless oats displayed a significantly higher GPC compared to hulled oats across all environments. A GWAS analysis was performed based on 38,313 high-quality SNPs, which detected 27 non-redundant QTLs with 41 SNPs significantly associated with GPC. Two QTLs on chromosome 6C (QTL16) and 4D (QTL11) were consistently detected in multiple environments, with QTL16 being the most significant and explaining the highest proportion of the phenotypical variation in all tested environments except in CZ20. Haplotype analysis showed that the favorable haplotypes for GPC are more prevalent in hulless oats. These findings provide a foundation for future efforts to incorporate favorable alleles into new cultivars through introgression, fine mapping, and cloning of promising QTLs.

Reference genome assemblies reveal the origin and evolution of allohexaploid oat.

Common oat (Avena sativa) is an important cereal crop serving as a valuable source of forage and human food. Although reference genomes of many important crops have been generated, such work in oat has lagged behind, primarily owing to its large, repeat-rich polyploid genome. Here, using Oxford Nanopore ultralong sequencing and Hi-C technologies, we have generated a reference-quality genome assembly of hulless common oat, comprising 21 pseudomolecules with a total length of 10.76 Gb and contig N50 of 75.27 Mb. We also produced genome assemblies for diploid and tetraploid Avena ancestors, which enabled the identification of oat subgenomes and provided insights into oat chromosomal evolution. The origin of hexaploid oat is inferred from whole-genome sequencing, chloroplast genomes and transcriptome assemblies of different Avena species. These findings and the high-quality reference genomes presented here will facilitate the full use of crop genetic resources to accelerate oat improvement.

First Report of Epicoccum sorghinum Causing Leaf Spot on Paeonia suffruticosa in China.

Tree peony (Paeonia suffruticosa Andr.; Paeoniaceae) is highly valued in Chinese culture for their ornamental and medicinal benefits in anti-inflammation, anti-arrhythmia, activating the immune system and protecting the cardiovascular system (Zhai et al. 2020). In May from 2019 to 2021, leaf spot symptoms were observed on tree peony in an area of 0.8 hm2 in Bozhou, Anhui Province, China; with a disease incidence of 35%. Initially, black-brown spots (0.5-2.4 mm) appeared on the leaves, as the disease developed, the spots enlarged to form round, black lesions. Small pieces of tissue taken from the margins of lesions were surface-disinfected by 75% ethanol for 20 s followed by 0.1% mercuric chloride for 3 min, rinsed with distilled sterile water for three times, placed on potato dextrose agar (PDA) at 25 ºC for 7 days in the dark.Fifteen single spore isolates were obtained as described (Dong 2009). When cultured on PDA for 10 days, colonies were white, villose, then became gray-brown, with the reverse side becoming reddish-brown; Chlamydospores globose or irregular shaped, dark brown, unicellular or multicellular (4.3 to 12.2 × 13.1 to 33.7 µm) (n = 200). Pycnidia were black-brown, mostly spheroid, and 86 to 128 × 110 to 197 µm (n = 50); Conidia were hyaline, ellipsoidal, unicellular, aseptate, and 4.1 to 5.2 × 1.8 to 2.4 µm (n = 200) . The DNA of a representative isolate AF21-1-2 was extracted using the CTAB protocol (Doyle and Doyle 1987). The rDNA internal transcribed spacer (ITS), ß-tubulin (TUB) and 28s nrDNA (LSU) genes were amplified and sequenced using the primers ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass et al. 1995), and LR5/LR0R (Vilgalys and Hester, 1990), respectively (OK485136, OK631973, and ON358331). BLASTn analysis showed that the ITS, TUB, and LSU sequences had 99% (497/501 bp), 98% (530/539 bp), and 99% (878/882 bp) identity with the Epicoccum sorghinum isolates ESCZO20 (MN944541), CZ01 (MT254851) and Dl16-338 (LN907481), respectively. Maximum likelihood phylogenetic tree revealed that AF21-1-2 clustered with E. sorghinum isolates. For pathogenicity test, leaves of 3-year-old healthy tree peony plant in the field were inoculated with 105 conidia/ml spore suspension (prepared with 30-day-old cultures on PDA), added with 0.1% (v/v) Tween-80. Ten surface-sterilized leaves per plant were sprayed with 30 ml suspension until runoff, a total of 3 plants were inoculated. Leaves sprayed with sterilized water serve as a negative control. Each plant was covered with a plastic bag to maintain high relative humidity at 15 to 23°C and was monitored daily for symptom development. Typical symptoms appeared on more than 80% of the leaves after 7 days of inoculation, while control leaves remained symptomless. Cultures isolated from inoculated leaves had the same morphological and molecular traits as those that were previously used to test Koch's postulates. Based on the morphological and molecular characteristics, the causal agent on tree peony was identified as E. sorghinum (Aveskamp et al. 2010). To our knowledge, this is the first report of E. sorghinum causing leaf spot on tree peony in China. The disease will cause serious economic loss for tree peony if it is not managed properly. This report may provide the basis for diagnosis and control of the disease.

Regulation of pathophysiological and tissue regenerative functions of MSCs mediated via the WNT signaling pathway (Review).

Tissues have remarkable natural capabilities to regenerate for the purpose of physiological turnover and repair of damage. Adult mesenchymal stem cells (MSCs) are well known for their unique self­renewal ability, pluripotency, homing potential, paracrine effects and immunomodulation. Advanced research of the unique properties of MSCs have opened up new horizons for tissue regenerative therapies. However, certain drawbacks of the application of MSCs, such as the low survival rate of transplanted MSCs, unsatisfactory efficiency and even failure to regenerate under an unbalanced microenvironment, are concerning with regards to their wider therapeutic applications. The activity of stem cells is mainly regulated by the anatomical niche; where they are placed during their clinical and therapeutic applications. Crosstalk between various niche signals maintains MSCs in homeostasis, in which the WNT signaling pathway plays vital roles. Several external or internal stimuli have been reported to interrupt the normal bioactivity of stem cells. The irreversible tissue loss that occurs during infection at the site of tissue grafting suggests an inhibitory effect mediated by microbial infections within MSC niches. In addition, MSC­seeded tissue engineering success is difficult in various tissues, when sites of injury are under the effects of a severe infection despite the immunomodulatory properties of MSCs. In the present review, the current understanding of the way in which WNT signaling regulates MSC activity modification under physiological and pathological conditions was summarized. An effort was also made to illustrate parts of the underlying mechanism, including the inflammatory factors and their interactions with the regulatory WNT signaling pathway, aiming to promote the clinical translation of MSC­based therapy.

Position Validation of the Dwarfing Gene Dw6 in Oat (Avena sativa L.) and Its Correlated Effects on Agronomic Traits.

An F6 : 8 recombinant inbred line (RIL) population derived from the cross between WAOAT2132 (Dw6) and Caracas along with the two parents were used to evaluate the genetic effects of Dw6 dwarfing gene on plant height and other agronomic traits in oat (Avena sativa L.) across three environments, and develop closely linked markers for marker-assisted selection (MAS) for Dw6. The two parents differed in all investigated agronomic traits except for the number of whorls. The RIL lines showed a bimodal distribution for plant height in all three tested environments, supporting the height of this population was controlled by a single gene. Dw6 significantly reduced plant height (37.66∼44.29%) and panicle length (13.99∼22.10%) but without compromising the coleoptile length which was often positively associated with the reduced stature caused by dwarfing genes. Dw6 has also strong negative effects on hundred kernel weight (14.00∼29.55%), and kernel length (4.21∼9.47%), whereas the effects of Dw6 on the kernel width were not uniform across three environments. By contrast, lines with Dw6 produced more productive tillers (10.11∼10.53%) than lines without Dw6. All these together suggested the potential yield penalty associated with Dw6 might be partially due to the decrease of kernel weight which is attributed largely to the reduction of kernel length. Eighty-one simple sequence repeat (SSR) primer pairs from chromosome 6D were tested, five of them were polymorphic in two parents and in two contrasting bulks, confirming the 6D location of Dw6. By using the five polymorphic markers, Dw6 was mapped to an interval of 1.0 cM flanked by markers SSR83 and SSR120. Caution should be applied in using this information since maker order conflicts were observed. The close linkages of these two markers to Dw6 were further validated in a range of oat lines. The newly developed markers will provide a solid basis for future efforts both in the identification of Dw6 in oat germplasm and in the determination of the nature of the gene through positional cloning.

New evidence confirming the CD genomic constitutions of the tetraploid Avena species in the section Pachycarpa Baum.

The tetraploid Avena species in the section Pachycarpa Baum, including A. insularis, A. maroccana, and A. murphyi, are thought to be involved in the evolution of hexaploid oats; however, their genome designations are still being debated. Repetitive DNA sequences play an important role in genome structuring and evolution, so understanding the chromosomal organization and distribution of these sequences in Avena species could provide valuable information concerning genome evolution in this genus. In this study, the chromosomal organizations and distributions of six repetitive DNA sequences (including three SSR motifs (TTC, AAC, CAG), one 5S rRNA gene fragment, and two oat A and C genome specific repeats) were investigated using non-denaturing fluorescence in situ hybridization (ND-FISH) in the three tetraploid species mentioned above and in two hexaploid oat species. Preferential distribution of the SSRs in centromeric regions was seen in the A and D genomes, whereas few signals were detected in the C genomes. Some intergenomic translocations were observed in the tetraploids; such translocations were also detected between the C and D genomes in the hexaploids. These results provide robust evidence for the presence of the D genome in all three tetraploids, strongly suggesting that the genomic constitution of these species is DC and not AC, as had been thought previously.

Genetic diversity and genome-wide association analysis in Chinese hulless oat germplasm.

KEY MESSAGE: Genotyping-by-sequencing (GBS)-derived molecular markers reveal the distinct genetic population structure and relatively narrow genetic diversity of Chinese hulless oat landraces. Four markers linked to the naked grain gene (N1) are identified by genome-wide association study (GWAS). Interest in hulless oat (Avena sativa ssp. nuda), a variant of common oat (A. sativa) domesticated in Western Asia, has increased in recent years due to its free-threshing attribute and its domestication history. However, the genetic diversity and population structure of hulless oat, as well as the genetic mechanism of hullessness, are poorly understood. In this study, the genetic diversity and population structure of a worldwide sample of 805 oat lines including 186 hulless oats were investigated using genotyping-by-sequencing. Population structure analyses showed a strong genetic differentiation between hulless landraces vs other oat lines, including the modern hulless cultivars. The distinct subpopulation stratification of hulless landraces and their low genetic diversity suggests that a domestication bottleneck existed in hulless landraces. Additionally, low genetic diversity within European oats and strong differentiation between the spring oats and southern origin oat lines revealed by previous studies were also observed in this study. Genomic regions contributing to these genetic differentiations suggest that genetic loci related to growth habit and stress resistance may have been under intense selection, rather than the hulless-related genomic regions. Genome-wide association analysis detected four markers that were highly associated with hullessness. Three of these were mapped on linkage group Mrg21 at a genetic position between 195.7 and 212.1 cM, providing robust evidence that the dominant N1 locus located on Mrg21 is the single major factor controlling this trait.

Phylogenetic relationships in the genus Avena based on the nuclear Pgk1 gene.

The phylogenetic relationships among 76 Avena taxa, representing 14 diploids, eight tetraploids, and four hexaploids were investigated by using the nuclear plastid 3-phosphoglycerate kinase gene (Pgk1). A significant deletion (131 bp) was detected in all the C genome homoeologues which reconfirmed a major structural divergence between the A and C genomes. Phylogenetic analysis indicated the Cp genome is more closely related to the polyploid species than is the Cv genome. Two haplotypes of Pgk1 gene were obtained from most of the AB genome tetraploids. Both types of the barbata group showed a close relationship with the As genome diploid species, supporting the hypothesis that both the A and B genomes are derived from an As genome. Two haplotypes were also detected in A. agadiriana, which showed close relationships with the As genome diploid and the Ac genome diploid, respectively, emphasizing the important role of the Ac genome in the evolution of A. agadiriana. Three homoeologues of the Pgk1 gene were detected in five hexaploid accessions. The homoeologues that might represent the D genome were tightly clustered with the tetraploids A. maroccana and A. murphyi, but did not show a close relationship with any extant diploid species.

Genetic mapping and a new PCR-based marker linked to a dwarfing gene in oat (Avena sativa L.).

Short straw is a desired trait in cultivated hexaploid oat (Avena sativa L.) for some production environments. Marker-assisted selection, a key tool for achieving this objective, is limited by a lack of mapping data and available markers. Here, bulked-segregant analysis was used to identify PCR-based markers associated with a dwarfing gene. Genetic analysis identified a monogenic dominant inheritance of one dwarfing gene from WAOAT2132, temporarily designated DwWA. A simple sequence repeat (SSR) marker (AME117) that was already available and a new codominant PCR-based marker (bi17) developed by homologous cloning in the present study were both associated with the dwarfing gene. The two markers were located 21 and 1.2 cM from DwWA, respectively. The bi17 marker was mapped to neighboring SNP markers on chromosome 18D of the oat consensus map. Since Dw6 was previously mapped on chromosome 18, and since our new marker bi17 is also diagnostic for NILs generated for Dw6, there is strong evidence that the dwarfing gene identified in WAOAT2132 is Dw6. The newly developed markers could find applications in the identification of this gene in oat germplasm and in the fine mapping or positional cloning of the gene.

High-density marker profiling confirms ancestral genomes of Avena species and identifies D-genome chromosomes of hexaploid oat.

KEY MESSAGE: Genome analysis of 27 oat species identifies ancestral groups, delineates the D genome, and identifies ancestral origin of 21 mapped chromosomes in hexaploid oat. We investigated genomic relationships among 27 species of the genus Avena using high-density genetic markers revealed by genotyping-by-sequencing (GBS). Two methods of GBS analysis were used: one based on tag-level haplotypes that were previously mapped in cultivated hexaploid oat (A. sativa), and one intended to sample and enumerate tag-level haplotypes originating from all species under investigation. Qualitatively, both methods gave similar predictions regarding the clustering of species and shared ancestral genomes. Furthermore, results were consistent with previous phylogenies of the genus obtained with conventional approaches, supporting the robustness of whole genome GBS analysis. Evidence is presented to justify the final and definitive classification of the tetraploids A. insularis, A. maroccana (=A. magna), and A. murphyi as containing D-plus-C genomes, and not A-plus-C genomes, as is most often specified in past literature. Through electronic painting of the 21 chromosome representations in the hexaploid oat consensus map, we show how the relative frequency of matches between mapped hexaploid-derived haplotypes and AC (DC)-genome tetraploids vs. A- and C-genome diploids can accurately reveal the genome origin of all hexaploid chromosomes, including the approximate positions of inter-genome translocations. Evidence is provided that supports the continued classification of a diverged B genome in AB tetraploids, and it is confirmed that no extant A-genome diploids, including A. canariensis, are similar enough to the D genome of tetraploid and hexaploid oat to warrant consideration as a D-genome diploid.

Genome size variation in the genus Avena.

Genome size is an indicator of evolutionary distance and a metric for genome characterization. Here, we report accurate estimates of genome size in 99 accessions from 26 species of Avena. We demonstrate that the average genome size of C genome diploid species (2C = 10.26 pg) is 15% larger than that of A genome species (2C = 8.95 pg), and that this difference likely accounts for a progression of size among tetraploid species, where AB < AC < CC (average 2C = 16.76, 18.60, and 21.78 pg, respectively). All accessions from three hexaploid species with the ACD genome configuration had similar genome sizes (average 2C = 25.74 pg). Genome size was mostly consistent within species and in general agreement with current information about evolutionary distance among species. Results also suggest that most of the polyploid species in Avena have experienced genome downsizing in relation to their diploid progenitors. Genome size measurements could provide additional quality control for species identification in germplasm collections, especially in cases where diploid and polyploid species have similar morphology.

Phylogenetic analysis of the genus Avena based on chloroplast intergenic spacer psbA-trnH and single-copy nuclear gene Acc1.

Two uncorrelated nucleotide sequences, chloroplast intergenic spacer psbA-trnH and acetyl CoA carboxylase gene (Acc1), were used to perform phylogenetic analyses in 75 accessions of the genus Avena, representing 13 diploids, seven tetraploid, and four hexaploids by maximum parsimony and Bayesian inference. Phylogenic analyses based on the chloroplast intergenic spacer psbA-trnH confirmed that the A genome diploid might be the maternal donor of species of the genus Avena. Two haplotypes of the Acc1 gene region were obtained from the AB genome tetraploids, indicating an allopolyploid origin for the tetraploid species. Among the AB genome species, both gene trees revealed differences between Avena agadiriana and the other species, suggesting that an AS genome diploid might be the A genome donor and the other genome diploid donor might be the Ac genome diploid Avena canariensis or the Ad genome diploid Avena damascena. Three haplotypes of the Acc1 gene have been detected among the ACD genome hexaploid species. The haplotype that seems to represent the D genome clustered with the tetraploid species Avena murphyi and Avena maroccana, which supported the CD genomic designation instead of AC for A. murphyi and A. maroccana.

[Effect of Salvia Miltiorrhiza Bunge on expression of osteoprotegerin in cultured human periodontal ligament fibroblasts].

PURPOSE: To study the effect of Salvia Miltiorrhiza Bunge on the expression of osteoprotegerin (OPG) in cultured human periodontal ligament fibroblasts. METHODS: Primary culture of human periodontal ligament fibroblasts was established and the fifth passage cells were used in this study. Concentration-dependent effect of Salvia Miltiorrhiza Bunge on OPG mRNA and OPG protein secretion were determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbant assay (ELISA), respectively. The data were analyzed with SPSS15.0 software package. RESULTS: OPG mRNA expression was increased after 1 h exposure to various concentrations of Salvia Miltiorrhiza Bunge compared with the control group (P<0.05). OPG protein secretion was significantly increased after 12 h exposure to various concentrations of Salvia Miltiorrhiza Bunge compared with the control group (P<0.05). CONCLUSION: Salvia Miltiorrhiza Bunge can up-regulate the expression of OPG in cultured human periodontal ligament fibroblasts.

[The clinical study of protraction face mask combining with MEAW technique to correct skeletal Class III malocclusion in the early permanent tooth].

PURPOSE: To investigate the clinical effects of combined multiloop Edgewise arch wire(MEAW) with protraction facemask to treat Class III malocclusion in early permanent dentition, and compare the changes of the periodental tissue and teeth between pre- and post- treatment to explore the mechenism of the method applied to correct Class III malocclusion. METHODS: 23 cases with Class III malocclusion were selected, including 11 males and 12 females, aged from 12 to 14 years old. MEAW and protraction facemask were used to treat Class III malocclusion in early permanent dentition. Lateral cephalometric films were taken for comparison in three stages:before the treatment(T1), seven months (T2) after treatment and in the end of the treatment(T3).SPSS10.0 software package was used for statistical analysis. RESULTS: The alveolar bone changes mainly happaned in the T2 stage, SNA increased by 2.37 degrees in average, OP-MP increased by 4.85 degrees in average; Wits increased by 2. 50 degrees in average. The difference was significant(P<0.05). However there was no significant difference between T2 and T3 stage. In the T2 stage,the overjet and overbite increased 4.43mm and 2.66mm in average, and increase continued after treatment. CONCLUSION: It is suggested that MEAW with protraction facemask is an effective technique to treat Class III malocclusion in early permanent dentition by improving maxillary growth.

[Transoral miniplate fixation of mandibular body fracture without maxillomandibular fixation: report of 45 cases].

PURPOSE: To assess the efficacy of intraoral open reduction of mandibular body fracture using titanium miniplate rigid fixation and intermaxillary traction titanium screw to rigidly tract the jaw during the operation. METHODS: 54 mandibular fractures in 45 patients were included in this study. After general anaesthesia, the intermaxillary traction titanium screw was inserted in the alveolar bone, between the two incisors, between the canine and the first premolar, between the first molar and the second molar, and the intermaxillary traction was finished with 0.5 mm stainless steel wire. After the mandibular arch and occlusion relationship were returned to preoperative condition, transoral mucoperiosteal incision was made to expose the fracture lines and fragments. Two 2.0 mm titanium miniplates were adapted along the Champy's line of ideal osteosynthesis and secured. After operation the stainless steel wire was released. Panoramic radiograph and clinical examination were applied at the first day and three months after operation to exhibit bone union and occlusion. RESULTS: Most patients displayed satisfied occlusion and bone union without major complications. Seventeen patients had numbness of the lower lips after operation, and the symptom was disappeared three months later. Two patients had improvement of numbness of the lower lips. CONCLUSION: Intraoral open reduction of mandibular body fracture using titanium miniplate rigid fixation and intermaxillary traction titanium screw showed high efficiency in fixation of the mandibular arch fractures , which occurred in the body and the angle of the mandible.

[Comparison of friction and abrasion between six different dental materials and natural enamel].

PURPOSE: The purpose of this study was to evaluate and compare the friction and abrasion of six kinds of dental materials that was widely used clinically. The mechanisms were investigated to provide experimental reference for selecting proper restorative material to protect opposite natural enamel of the patients. METHODS: In the experimental groups,pure Ti, Ti alloy, Au-Pd alloy, Ni-Cr alloy, AgHg alloy,ceramic were fabricated into thirty uniform 8.0mmx8.0mmx2.0mm block. Five specimens in each group.In the control group,five recently extracted mandibular third molar of adults were fabricated into 8.0mmx8.0mmx2.0mm block. Steatites were fabricated into discs in the diameter of 25mm and thickness of 2.0mm to act as counter sample materials. The mass loss of each specimen and the opposing steatite were weighted by electric balance. The volume loss of the materials and opposing steatites were analyzed by SPSS11.5 software package and the difference was compared between each group. RESULTS: The ranking of the volume loss of six materials and enamel from the most to the least was group A, group E, group C, group D, group B, group F and group G. Significant difference was found between group A and the other groups. No significance was found between group G and F. The coefficient of friction of group A-G was 0.68, 0.12, 0.11, 0.41, 0.38, 0.48 and 0.65,respectively. CONCLUSION: The six materials in this study were less resistant to wear than natural tooth. The wear of pure Ti, AgHg alloy and Ni-Cr alloy are to enamel.

Tissue-engineering approaches for axonal guidance.

Owing to the profound impact of nervous system damage, extensive studies have been carried out aimed at facilitating axonal regeneration following injury. Tissue engineering, as an emerging and rapidly growing field, has received extensive attention for nervous system axonal guidance. Numerous engineered substrates containing oriented extracellular matrix molecules, cells or channels have displayed potential of supporting axonal regeneration and functional recovery. Most attempts are focused on seeking new biomaterials, new cell sources, as well as novel designs of tissue-engineered neuronal bridging devices, to generate safer and more efficacious neuronal tissue repairs.