Biological organization of hydroxyapatite crystallites into a fibrous continuum toughens and controls anisotropy in human enamel

Enamel forms the outer surface of teeth, which are of complex shape and are loaded in a multitude of ways during function. Enamel has previously been assumed to be formed from discrete rods and to be markedly aniostropic, but marked anisotropy might be expected to lead to frequent fracture. Since frequent fracture is not observed, we measured enamel organization using histology, imaging, and fracture mechanics modalities, and compared enamel with crystalline hydroxyapatite (Hap), its major component. Enamel was approximately three times tougher than geologic Hap, demonstrating the critical importance of biological manufacturing. Only modest levels of enamel anisotropy were discerned; rather, our measurements suggest that enamel is a composite ceramic with the crystallites oriented in a complex three-dimensional continuum. Geologic apatite crystals are much harder than enamel, suggesting that inclusion of biological contaminants, such as protein, influences the properties of enamel. Based on our findings, we propose a new structural model.     

Nuclear DNA fragmentation during postnatal tooth development of mouse and hamster and during dentin repair in the rat

The TUNEL (transferase-mediated. dUTP-biotin nick end labeling) method for in situ labeling of DNA strands was utilized to localize DNA fragmentation in cells involved in tooth formation in the neonatal mouse and hamster. Positive reactions for the presence of DNA fragments were obtained in some epithelial cells of the cervical loop region of incisors, late secretory, transitional and early maturation stage ameloblasts, stratum intermedium cells and in shortened ameloblasts just before eruption. Also, cells of the periodontal ligament of the continuously erupting incisors stained positive shortly before eruption. Odontoblasts were negative but became strongly positive during the formation of physiological osteodentin at the tip of developing incisors. Osteodentin matrix and the surfaces of unerupted enamel and cementum just prior to eruption stained for DNA fragments as well. DNA fragmentation could be elicited in odontoblasts and underlying pulpal tissues of mature erupted molars after mechanical injury to the odontoblast processes during cavity preparation. We conclude that, in rodents. DNA fragmentation and cell death are biological processes which take place in a variety of cells involved in formation of teeth. The TUNEL staining technique is a simple but powerful tool to examine the fate of cells and tissues undergoing either programmed cell death (apoptosis) or fragmentation of nuclear DNA induced by external factors leading to pathological changes.     

Differential expression of IGF-I and its mRNA in mandibular condylar cartilage of rat--direct evidence for servosystem theory of facial growth]

It was studied the expression of IGF-I and its mRNA in the condylar cartilage of 10 7-week-old SD male rats by using in situ hybridization and immunohisto-chemistry technique. The results showed both IGF-I and its gene expressed in growing rat condyle. IGF-I peptide was abundant in germinal zone, and positive reaction of its mRNA was strongest in transitional and maturational zones. These indicate that condylar cartilage has the capability of local production and secretion of IGF-I, mediating the command effect of STH, and differential expression of IGF-I and its mRNA might establish the local feedback loop, which supply a direct evidence for servosystem theory of facial growth.     

创伤性凝血病患者血清hs-CRP及TNF-α水平与预后的关系

目的：探讨创伤性凝血病患者血清hs-CRP及TNF-α水平及与预后的关系。方法回顾性分析50例创伤性凝血病患者的临床资料,根据患者不同预后分为存活组与死亡组,比较2组凝血功能指标及血清 TNF-α及hs-CRP水平。结果治疗28 d时,存活31例,死亡19例,病死率38％;存活组患者入院时PLT显著高于死亡组,且PT、APTT、D-dimer显著低于死亡组,差异均有统计学意义（P＜0.05）;存活组患者入院时血清hs-CRP及TNF-α水平均显著低于死亡组,差异有统计学意义（P＜0.05）。结论创伤性凝血病患者血清hs-CRP及TNF-α水平显著升高,并可作为判断患者预后的指标。     

Microsatellite markers development in the clam,Paphia amabilis (Philippi, 1847)

The clam Paphia amabilis is an important edible shellfish in southern China and Japan. Recently the natural populations of this species has significantly decreased due to the environmental changes and overfishing. To support the conservation and aquaculture of this species, we developed 12 microsatellite markers for the clam and characterized them in a wild population. These markers were polymorphic with the number of alleles per locus ranged from 2 to 9, the observed heterozygosity and expected heterozygosity ranged from 0.22 to 0.79 and from 0.33 to 0.87, respectively. Ten of the 12 markers conformed to Hardy–Weinberg equilibrium. This is the first set of microsatellites developed for P. amabilis and these markers will promote the genetic studies and species protection of this species.