A cadaveric study of age-related changes in the triangular fibrocartilage of the wrist in Hong Kong Chinese confirms the high incidence of tears with increasing age. There appears to be two distinct types, linear and degenerate, with no clear evidence that the former is simply a precursor of the latter.
Summary: Partial patellectomy for patellar fracture was performed in 56 patients. The patellar tendon-to-bone repair was reinforced by a figure-of-eight tension band wire loop from the patella down to the tibial tubercle. Early mobilization and weight bearing of the injured extremity was initiated within the first postoperative week. Thirty-one patients treated between 1977 and 1980 were reviewed retrospectively at an average of 22 months (range 3-49 months). Twenty-five patients treated between 1984 and 1987 were studied prospectively: Knee function was monitored at 5.5 weeks after injury, at 3 months, and at final follow-up at a mean of 25 months (range 8-48 months). Satisfactory knee function was recovered by 3 months. No disruption of knee extensor mechanism was encountered. Complications were frequent in the retrospective series. A high percentage of patients had radiological osteoarthritis after the fracture. This could be due to alteration of the patellofemoral articulation after part of the patella was excised.
It has been shown that many diseases are linked to abnormalities of the erythrocyte membrane. This study observed the changes in erythrocyte membrane fluidity during an immobilization period of 21 days. The right hindlimbs of male adult New Zealand white rabbits were immobilized for 21 days. Blood samples were collected and heparinized prior to immobilization and on days 1, 3, 7, 14, and 21 of immobilization. The membrane fluidity of erythrocytes was measured by spin-label electron spin resonance (ESR). The membrane fluidity was expressed by the value of order parameter (S). The results showed a significant increase of S on days 7 and 14 of immobilization (p <0.01). The highest value of S was found on day 7 of immobilization; thereafter, S gradually declined. Compared with the value measured before immobilization, there was no significant difference in the value of S on day 21. The results show that immobilization significantly affected erythrocyte membrane fluidity, indicating a systemic and temporal response ofthe immobilized body. This study is the first to document the time-course of changes in erythrocyte membrane fluidity in rabbits with single hindlimb immobilization during 21 days. These results may be helpful in studying the pathophysiology of immobilization.
In this study, the vibrating bar theory is used for modeling the muscle vibration, or vibromyographic (VMG) signal under functional electrical stimulation (FES). The simplified movement equation is derived, with the assumption that the muscle is a bar as a fibrous cable and undergoes transverse vibration only. The numerical simulation is performed with the parameters given either from published literature or by rough estimation. The simulation result is compared with that of experiment to test physiological validity of the model. It is found that the the vibrating bar model can well describe the feature of VMG signal elicited by FES. Finally, the relationship between the peak frequencies of the simulated VMG signals and the mechanical and physiological parameters of muscle, such as muscle tension and muscle stiffness, is discussed. It can be concluded that both muscle tension and stiffness affect the frequency of VMG signal and that the peak frequency is sensitive to the resting bending stiffness, E/sub b0/, when E/sub b0/ is in the range from 1.0/spl times/10/sup 4/ N/m/sup 2/ to 1.0/spl times/10/sup 6/ N/m/sup 2/. Therefore VMG signal analysis may be used as a potential tool for predicting muscle fatigue.
This study examined histologically the potential of using allogeneic cultured chondrocyte pellet (CCP) in enhancing bone-tendon junction (BTJ) healing using a rabbit partial patellectomy model. Chondrocytes isolated from the cartilaginous ribs of 6-week-old New Zealand white rabbits were cultured for 14 days to form CCP. Partial patellectomy was performed on 30 18-week-old rabbits. After removal of the distal third patella, the BTJ gap was repaired surgically with or without CCP interposition. Four samples of patella-patellar tendon complexes (PPTC) for each group were harvested each at 8, 12, and 16 weeks; and two additional PPTC for each group were harvested at 2, 4, and 6 weeks for early observation of fibrocartilage zone regeneration, histologically. Results showed that CCP interposition demonstrated earlier structural integration at the BTJ after 8, 12, and 16 weeks of healing, and formation of a fibrocartilage zone like structure, compared with control specimens. In addition, no immune rejection was observed in CCP experimental group. The results suggested that CCP had a stimulatory effect on BTJ healing. This bioengineering approach might have potential clinical application in treatment of difficult BTJ healing. However, systemic histomorphometric, immunological tests, and biomechanical evaluations are needed before any clinical trials.
The human umbilical cord perivascular cells (HUCPVCs) have been considered as an alternative source of mesenchymal progenitors for cell based regenerative medicine. However, the biological properties of these cells remain to be well characterized. In the present study, HUCPVCs were isolated and sorted by CD146+ pericyte marker. The purified CD146+ HUCPVCs were induced to differentiate efficiently into osteoblast, chondrocyte and adipocyte lineages in vitro. Six weeks following subcutaneous transplantation of CD146+ HUCPVCs-Gelfoam-alginate 3D complexes in severe combined immunodeficiency (SCID) mice, newly formed bone matrix with embedded osteocytes of donor origin was observed. The functional engraftment of CD146+ HUCPVCs in the new bone regenerates was further confirmed in a critical-sized bone defect model in SCID mice. Hypoxic conditions suppressed osteogenic differentiation while increased cell proliferation and colony-forming efficiency of CD146+ HUCPVCs as compared to that under normoxic conditions. Re-oxygenation restored the multi-differentiation potential of the CD146+ HUCPVCs. Western blot analysis revealed an upregulation of HIF-1α, HIF-2α, and OCT-4 protein expression in CD146+ HUCPVCs under hypoxia, while there was no remarkable change in SOX2 and NANOG expression. The gene expression profiles of stem cell transcription factors between cells treated by normoxia and hypoxic conditions were compared by PCR array analysis. Intriguingly, PPAR-γ was dramatically downregulated (20-fold) in mRNA expression under hypoxia, and was revealed to possess a putative binding site in the Hif-2α gene promoter region. Chromatin immunoprecipitation assays confirmed the binding of PPAR-γ protein to the Hif-2α promoter and the binding was suppressed by hypoxia treatment. Luciferase reporter assay showed that the Hif-2α promoter activity was suppressed by PPAR expression. Thus, PPAR-γ may involve in the regulation of HIF-2α for stemness maintenance and promoting the expansion of CD146+ HUCPVCs in response to hypoxia. CD146+ HUCPVCs may serve as a potential autologous cell source for bone regeneration.
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