Strength-fracture toughness synergy strategy in ostrich tibia's compact bone: Hierarchical and gradient

Ostriches are the fastest bipeds in the world, but their tibias are very thin. How the thin tibia can withstand the huge momentum impacts of the heavy body during running? The present work revealed that the combination of hierarchical and gradient design strategies was the main reason for their high strength and fracture toughness. The microstructure of ostrich's tibias compact bone was self-assembled into the 6-level hierarchical structure from the hydroxyapatite (HAP) crystals, collagen fiber (sub-nano), mineralized collagen fiber (nano-), mineralized collagen fiber bundle (sub-micro), lamellae (micro-) and osteon (macro-scales). The most distinctive design in the ostrich compact bone was that the HAP crystals were embedded in collagen fibers as well as wrapped in the outer layer of mineral collagen fibers (MCFs) in the form of HAP nanocrystals, thus achieving a high degree of soft and hard combination from the nanoscale. The bending strength was gradient-structure dependent and up to 787.2 ± 40.5 MPa, 4 times that of a human's compact bone. The fracture toughness (K_Jc) is 5.8 ± 0.1 MPa m^1/2. Several toughening mechanisms, such as crack deflection/twist, bridging, HAP fibers pulling-out, and fracture of the MCF bundles were found in the compact bone.

[Retrospective analysis of 4 rare cases of temporomandibular joint disc ossification]

Objective: To summarize the clinical manifestation and treatment of temporomandibular joint (TMJ) disc ossification, providing reference for clinical diagnosis and treatment of TMJ disc ossification. Methods: From January 2006 to January 2018, 4 patients with TMJ disc ossification (2 males and 2 females, aged 20-55 years with an average age of 35.5 years) which were admitted to the Department of Oral and Maxillofacial Surgery, Shenzhen Second People's Hospital were analyzed retrospectively. Ossification of TMJ disc was found in 4 cases during TMJ surgery. Two cases underwent partial ossification resection plus disc reduction and anchorage, and two cases underwent discectomy plus temporalis myofascial flap replacement. The causes, clinical manifestations and surgical effects of TMJ disc ossification were analyzed by comparing the maximal interincisal opening, visual analogue scale (VAS) score and MRI imaging indexes before and after operation. Results: The history of anterior disc displacement of TMJ in 4 patients was long (average 11.5 years). In clinic, TMJ disc ossification was characterized by TMJ pain and limitation of mouth opening. The maximal interincisal opening was (32.1±6.1) mm and the VAS score was (7.3±0.4) before operation. MRI showed that the displaced discs of the affected sides were displaced and the condyle bones were worn. During the operation, ossification of TMJ discs was found yellow and hard, and the original elasticity was lost. Pathologic findings showed that the TMJ disc cartilage were ossified to osteoid tissue. Under the microscope, bone cells scattered around the bone cells and red trabecular bone were seen, and there were bone trabecula formed. In a follow-up of one year, TMJ pain was significantly decreased [VAS: (1.7±0.2)], and the maximal interincisal opening was (38.5±2.2) mm. MRI showed that the TMJ disc returned to normal position, and the sign of repairing and reconstruction of condyle bone could be found. Conclusions: Long term displacement of TMJ disc may cause ossification with pain and limitation of interincisal opening. According to the degree and extent of ossification, partial ossification plus disc reduction and anchorage or discectomy plus temporalis myofascial flap replacement is feasible, and the clinical effects are satisfactory.

Effects of perinatal exposure to nonylphenol on delivery outcomes of pregnant rats and inflammatory hepatic injury in newborn rats

The current study aimed to investigate the effects of perinatal exposure to nonylphenol (NP) on delivery outcome of pregnant rats and subsequent inflammatory hepatic injury in newborn rats. The pregnant rats were divided into 2 groups: control group (corn oil) and NP exposure group. Thirty-four pregnant rats were administered NP or corn oil by gavage from the sixth day of pregnancy to 21 days postpartum, with blood samples collected at 12 and 21 days of pregnancy and 60 days after delivery. The NP concentration was measured by HPLC, with chemiluminescence used for detection of estrogen and progesterone levels. Maternal delivery parameters were also observed. Liver and blood of the newborn rats were collected and subjected to automatic biochemical detection of liver function and blood lipid analyzer (immunoturbidimetry), and ultrastructural observation of the hepatic microstructure, with the TNF-α and IL-1β hepatic tissue levels evaluated by immunohistochemistry. Compared with the control group, the pregnant and postpartum serum NP and estradiol levels of the mother rats in the NP group were significantly increased, together with lowered progesterone level, increased number of threatened abortion and dystocia, and fewer newborn rats and lower litter weight. Serum and hepatic NP levels of the newborn rats measured 60 days after birth were significantly higher than those of the control group, as well as lower testosterone levels and increased estradiol levels. When observed under electron microscope, the hepatocyte nuclei of the control group were large and round, with evenly distributed chromatin. The chromatin of hepatocytes in the NP group presented deep staining of the nuclei, significant lipid decrease in the cytoplasm, and the majority of cells bonded with lysate. The results of immunohistochemistry showed that there was almost no TNF-α or IL-1β expression in the hepatocytes of the control group, while the number of TNF-α-, PCNA-, and IL-1β-positive cells in the NP group was increased, with higher integral optical density than the control group. Compared to the control group, the serum levels of alanine aminotransferase, aspartate aminotransferase, triglyceride and low-density lipoprotein in the newborn rats of the NP group were significantly increased. There was no significant difference in the serum level of high-density lipoprotein or cholesterol between the groups. Perinatal exposure to NP can interfere with the in vivo estrogen and progesterone levels of pregnant rats, resulting in threatened abortion, dystocia and other adverse delivery outcomes. High liver and serum NP levels of the newborn rats led to alteration of liver tissue structure and function. The NP-induced hepatotoxicity is probably mediated by inflammatory cytokines TNF-α and IL-1α.

Shear Wave Elastography--A New Quantitative Assessment of Post-Irradiation Neck Fibrosis

PURPOSE

Shear wave elastography (SWE) is a new technique which provides quantitative assessment of soft tissue stiffness. The aim of this study was to assess the reliability of SWE stiffness measurements and its usefulness in evaluating post-irradiation neck fibrosis.

MATERIALS AND METHODS

50 subjects (25 patients with previous radiotherapy to the neck and 25 sex and age-matched controls) were recruited for comparison of SWE stiffness measurements (Aixplorer, Supersonic Imagine). 30 subjects (16 healthy individuals and 14 post-irradiated patients) were recruited for a reliability study of SWE stiffness measurements. SWE stiffness measurements of the sternocleidomastoid muscle and the overlying subcutaneous tissues of the neck were made. The cross-sectional area and thickness of the sternocleidomastoid muscle and the overlying subcutaneous tissue thickness of the neck were also measured. The post-irradiation duration of the patients was recorded.

RESULTS

The intraclass correlation coefficients for the intraoperator and interoperator reliability of deep and subcutaneous tissue SWE stiffness ranged from 0.90-0.99 and 0.77-0.94, respectively. The SWE stiffness measurements (mean +/- SD) of deep and subcutaneous tissues were significantly higher in the post-irradiated patients (64.6 ± 46.8 kPa and 63.9 ± 53.1 kPa, respectively) than the sex and age-matched controls (19.9 ± 7.8 kPa and 15.3 ± 8.37 respectively) (p < 0.001). The SWE stiffness increased with increasing post-irradiation therapy duration in the Kruskal Wallis test (p < 0.001) and correlated with muscle atrophy and subcutaneous tissue thinning (p < 0.01).

CONCLUSION

SWE is a reliable technique and may potentially be an objective and specific tool in quantifying deep and subcutaneous tissue stiffness, which in turn reflects the severity of neck fibrosis.