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Biomedical subjects

Ming Zhang

Publications and source records attributed to Ming Zhang.

At least 127 records · Page 7Linked to original sources
PubMed2005

A quasi-dynamic nonlinear finite element model to investigate prosthetic interface stresses during walking for trans-tibial amputees.

BACKGROUND: To predict the interface pressure between residual limb and prosthetic socket for trans-tibial amputees during walking. METHODS: A quasi-dynamic finite element model was built based on the actual geometry of residual limb, internal bones and socket liner. To simulate the friction/slip boundary conditions between the skin and liner, automated surface-to-surface contact was used. Besides variable external loads and material inertia, the coupling between the large rigid displacement of knee joint and small elastic deformation of residual limb and prosthetic components were also considered. RESULTS: Interface pressure distribution was found to have the same profile during walking. The high pressures fall over popliteal depression, middle patella tendon, lateral tibia and medial tibia regions. Interface pressure predicted by static or quasi-dynamic analysis had the similar double-peaked waveform shape in stance phase. INTERPRETATION: The consideration of inertial effects and motion of knee joint cause 210% average variation of the area between the pressure curve and the horizontal line of pressure threshold between two cases, even though there is only a small change in the peak pressure. The findings in this paper show that the coupling dynamic effects of inertial loads and knee flexion must be considered to study interface pressure between residual limb and prosthetic socket during walking.

Artificial Limbs↗
PubMed2005

Design of monolimb using finite element modelling and statistics-based Taguchi method.

BACKGROUND: Monolimb is a transtibial prosthesis having the socket and shank molded into one piece of thermoplastic material. If properly designed, the shank of a monolimb can have a controlled deflection during walking which simulates the ankle joint motions to some extent. However, there is no clear guidance for the design of monolimb considering the dilemma between shank flexibility and structural integrity. METHODS: Finite element analysis was used to simulate structural tests based on ISO10328 on monolimbs of different configurations. Statistics-based Taguchi method was employed to identify the significance of each design factor in controlling the deformation and stress within monolimbs. The design factors considered were the thickness of the thermoplastics, anteroposterior and medialateral dimensions of the elliptical shank, and depth of the posterior seam line. By progressively fine-tuning the design factors, the monolimb configuration was optimized giving offering appropriate flexibilities of the shank and would not structurally fail in normal uses. Experimental structural test was used to validate the finite element model. FINDINGS: Anteroposterior dimension of the shank was shown to be the most important design factor determining the peak von Mises stress values, deformation and dorsiflexion angles of monolimbs. Depth of seam line appears much less important than the other three factors. A monolimb fulfilling the design requirements was suggested. Experimental test results reasonably matched with the finite element results. INTERPRETATION: Finite element analysis and Taguchi method was shown to be an effective method in optimizing the structural design of prostheses. Further prosthetic design can be facilitated based on the degree of importance of the design factors on the structural behavior of the prosthesis. Gait analysis of amputees using the suggested monolimb design is needed in the future.

Algorithms↗
PubMed2005

Changes in integrin expression during adipocyte differentiation.

3T3-L1 preadipocytes require cAMP for maximal differentiation. Microarray analysis reveals that the integrins alpha5 and alpha6 are coordinately regulated by cAMP. alpha5 expression is gradually diminished during adipogenesis, whereas alpha6 is increased. Overexpression of alpha5 in preadipocytes results in enhanced proliferation and attenuated differentiation. Conversely, alpha6 overexpression is without effect. The GTPase Rac is normally inhibited during differentiation. However, overexpression of integrin alpha5 increases Rac activity. Constitutively active but not dominant-negative Rac inhibits differentiation when overexpressed in preadipocytes, implying its role downstream of alpha5 integrin in maintaining preadipocytes in an undifferentiated state. Moreover, alpha6 integrin is critically involved in clustering growth-arrested preadipocytes on basement membrane Matrigel. Perturbation of such clustering enhances Rho activity and promotes growth-arrested preadipocytes to reenter the cell cycle. These findings demonstrate a role for integrin alpha6 in connecting morphogenesis with signaling processes leading to terminal differentiation.

3T3-L1 Cells↗
PubMed2005

Three-dimensional finite element analysis of the foot during standing--a material sensitivity study.

Information on the internal stresses/strains in the human foot and the pressure distribution at the plantar support interface under loading is useful in enhancing knowledge on the biomechanics of the ankle-foot complex. While techniques for plantar pressure measurements are well established, direct measurement of the internal stresses/strains is difficult. A three-dimensional (3D) finite element model of the human foot and ankle was developed using the actual geometry of the foot skeleton and soft tissues, which were obtained from 3D reconstruction of MR images. Except the phalanges that were fused, the interaction among the metatarsals, cuneiforms, cuboid, navicular, talus, calcaneus, tibia and fibula were defined as contact surfaces, which allow relative articulating movement. The plantar fascia and 72 major ligaments were simulated using tension-only truss elements by connecting the corresponding attachment points on the bone surfaces. The bony and ligamentous structures were embedded in a volume of soft tissues. The encapsulated soft tissue was defined as hyperelastic, while the bony and ligamentous structures were assumed to be linearly elastic. The effects of soft tissue stiffening on the stress distribution of the plantar surface and bony structures during balanced standing were investigated. Increases of soft tissue stiffness from 2 and up to 5 times the normal values were used to approximate the pathologically stiffened tissue behaviour with increasing stages of diabetic neuropathy. The results showed that a five-fold increase in soft tissue stiffness led to about 35% and 33% increase in the peak plantar pressure at the forefoot and rearfoot regions, respectively. This corresponded to about 47% decrease in the total contact area between the plantar foot and the horizontal support surface. Peak bone stress was found at the third metatarsal in all calculated cases with a minimal increase of about 7% with soft tissue stiffening.

Adult↗
PubMed2005

Murine cytomegalovirus (MCMV) spreads to and replicates in the retina after endotoxin-induced disruption of the blood-retinal barrier of immunosuppressed BALB/c mice.

The goal of this study was to determine whether disruption of the blood-retinal barrier (BRB) facilitates spread of MCMV to the retina in immunosuppressed (IS) BALB/c mice. IS mice were inoculated intravenously (i.v.) with murine cytomegalovirus (MCMV) or with macrophages infected with MCMV for 4 days in vitro. The BRB was disrupted by injection of sodium iodate (i.v.) or lipopolysaccharide (LPS, i.v. or anterior chamber). Frozen sections of ocular tissue were examined for MCMV antigens. The results showed that MCMV-infected cells were observed only in the choroid and ciliary body in IS mice with an intact BRB. After LPS injection, a few positive cells were observed in the retina of IS mice after i.v. injection of MCMV. In lipopolysaccharide (LPS)-treated IS mice, a few PKH-26-positive macrophages or MCMV-positive cells were observed in the retina at 1 or 2 days after injection of macrophages. No PKH-26-positive cells or virus-infected cells were noted in the retina of phosphate-buffered saline (PBS)-treated mice. Ten days after injection of virus-infected macrophages, MCMV-infected cells were observed in choroid and ciliary body of both LPS- and PBS-treated mice, but they were observed in the retina only in LPS-treated mice. The results support the idea that disruption of the BRB allows MCMV to spread to the retina of IS mice and that monocytes/macrophages disseminate MCMV to the retina in mice with a disrupted BRB. By extrapolation, damage to the BRB in immunosuppressed patients may facilitate spread of CMV-infected monocytes/macrophages to the retina.

Animals↗
PubMed2005

HIV type 1 CRF13_cpx revisited: identification of a new sequence from Cameroon and signal for subsubtype J2.

A nearly full-length genome sequence of an HIV-1 isolate originating from Cameroon, 02CM.3226MN, was found to cluster together with previously reported CRF13 sequences 96CM-4164 and 96CM-1849. Similarity plotting, bootscanning, breakpoint analysis, and phylogenetic trees confirmed similar genomic structures with almost identical breakpoint positions among these three isolates. Thus, CRF13 now fulfills the HIV-1 nomenclature requirements. A X2 analysis across all three genomes simultaneously was applied to more accurately determine breakpoints and address the uncertainty in such estimates. Some fragments were found to be difficult to classify, as indicated by a low branching index (BI), due to limited knowledge about parental and reference subtype sequences. One fragment with low BI association to reference subtype J sequences (BI = 0.27, cut-off for subtype classification >0.55) was found to be closer to J fragments of CRF11 similar to the way that A1-A2 and F1-F2 subsubtypes associate. This suggests that subtype J may need to be reclassified into subsubtypes J1 and J2. The CRF13 genome consists of fragments from subtypes A1, G, and both J1 and J2 as well as CRF01 and one region that was left unclassified.

Cameroon↗
PubMed2005

Does the investing layer of the deep cervical fascia exist?

BACKGROUND: The placement of the superficial cervical plexus block has been the subject of controversy. Although the investing cervical fascia has been considered as an impenetrable barrier, clinically, the placement of the block deep or superficial to the fascia provides the same effective anesthesia. The underlying mechanism is unclear. The aim of this study was to investigate the three-dimensional organization of connective tissues in the anterior region of the neck. METHODS: Using a combination of dissection, E12 sheet plastination, and confocal microscopy, fascial structures in the anterior cervical triangle were examined in 10 adult human cadavers. RESULTS: In the upper cervical region, the fascia of strap muscles in the middle and the fasciae of the submandibular glands on both sides formed a dumbbell-like fascia sheet that had free lateral margins and did not continue with the sternocleidomastoid fascia. In the lower cervical region, no single connective tissue sheet extended directly between the sternocleidomastoid muscles. The fascial structure deep to platysma in the anterior cervical triangle comprised the strap fascia. CONCLUSIONS: This study provides anatomical evidence to indicate that the so-called investing cervical fascia does not exist in the anterior triangle of the neck. Taking the previous reports together, the authors' findings strongly suggest that deep potential spaces in the neck are directly continuous with the subcutaneous tissue.

Aged↗
PubMed2005

Celecoxib, a selective cyclooxygenase-2 inhibitor, decreases monocyte chemoattractant protein-1 expression and neointimal hyperplasia in the rabbit atherosclerotic balloon injury model.

The inflammation in response to vascular injury is becoming increasingly recognized as a potential contributor to restenosis. Cyclooxygenase-2 (COX-2) is the inducible form of cyclooxygenase and has been shown to be involved in the proinflammatory response of vascular tissue. Bilateral femoral artery lesions were induced by air desiccation in New Zealand White rabbits followed by high cholesterol diet feeding for 28 days. Balloon injury and stent implantation were performed at the preinjured vessel segments. Immunostaining showed that uninjured vessel segments stained positive only for COX-1 but not for COX-2. Injured vessel segments showed, in addition to COX-1, significant positive staining for COX-2. In the efficacy study, celecoxib (75 mg/kg/d) was administered orally beginning 3 hours before balloon injury or stent implantation on day 28 and daily for 21 days. Monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-2 and -9 (MMPs) expression were quantified in arterial extracts 4 days after balloon injury by Western blot and gelatin zymography. Morphometric analysis and immunostaining for macrophages were performed 21 days after balloon injury. Celecoxib treatment significantly decreased MCP-1 expression (P < 0.01). Neointimal hyperplasia was significantly inhibited by celecoxib in both balloon injury and stent models (0.49 +/- 0.20 versus 0.70 +/- 0.35 mm2 from balloon injury model, P < 0.05, and 0.81 +/- 0.25 versus 1.69 +/- 0.43 mm2 from stent model, P < 0.05), accompanied by reduced macrophage infiltration. We conclude that celecoxib decreases the inflammatory response and intimal hyperplasia following vascular injury, possibly through inhibition of MCP-1 expression, implying a pivotal role of inflammation in the pathogenesis of restenosis.

Angioplasty, Balloon↗
PubMed2005

Extract of Ginkgo biloba leaves reverses yohimbine-induced spatial working memory deficit in rats.

Extract of Ginkgo biloba is used to alleviate age-related decline in cognitive function, which may be associated with the loss of catecholamines in the prefrontal cortex. The purpose of this study was to verify whether alpha-2 adrenergic activity is involved in the facilitative effects of extract of Ginkgo biloba on prefrontal cognitive function. Male Wistar rats were trained to reach criterion in the delayed alternation task (0, 25, and 50-s delay intervals). A pilot study found that 3 or 4 mg/kg of yohimbine (intraperitoneal) reduced the choice accuracy of the delayed alternation task in a dose and delay-dependent manner, without influencing motor ability or perseverative behaviour. Acute oral pre-treatment with doses of 50, 100, or 200 mg/kg (but not 25 mg/kg) of extract of Ginkgo biloba prevented the reduction in choice accuracy induced by 4 mg/kg yohimbine. These data suggest that the prefrontal cognition-enhancing effects of extract of Ginkgo biloba are related to its actions on alpha-2-adrenoceptors.

Adrenergic alpha-Antagonists↗
PubMed2005

Maspin mediates increased tumor cell apoptosis upon induction of the mitochondrial permeability transition.

Maspin is a unique serpin with the ability to suppress certain types of malignant tumors. It is one of the few p53-targeted genes involved in tumor invasion and metastasis. With this in mind, we attempted to study the molecular mechanism behind this tumor suppression. Maspin-expressing mammary tumors are more susceptible to apoptosis in both implanted mammary tumors in vivo, a three-dimensional spheroid culture system, as well as in monolayer cell culture under lowered growth factors. Subcellular fractionation shows that a fraction of maspin (in both TM40D-Mp and mutant maspinDeltaN cells) translocates to the mitochondria. This translocation of maspin to the mitochondria is linked to the opening of the permeability transition pore, which in turn causes the loss of transmembrane potential, thus initiating apoptotic degradation. This translocation is absent in the other mutant, maspinDeltaRSL. It fails to cause any loss of membrane potential and also shows decreased caspase 3 levels, proving that translocation to the mitochondria is a key event for this increase in apoptosis by maspin. Suppression of maspin overexpression by RNA interference desensitizes cells to apoptosis. Our data indicate that maspin inhibits tumor progression through the mitochondrial apoptosis pathway. These findings will be useful for maspin-based therapeutic interventions against breast cancer.

Animals↗
PubMed2005

Ocular reactivation of MCMV after immunosuppression of latently infected BALB/c mice.

PURPOSE: The purpose of this study was to identify the site(s) of MCMV latency and reactivation in the eye. METHODS: Three months after supraciliary inoculation of 5 x 10(2) PFU of MCMV, BALB/c mice underwent immunosuppression with methylprednisolone and antibodies specific for CD4 T cells, CD8 T cells, and NK cells or with methylprednisolone alone. Control mice were infected but did not receive the immunosuppressants. After 2 or 3 weeks of immunosuppression, the mice were killed. Replicating virus and viral antigen were detected in the injected eyes, peripheral blood leukocytes (PBLs), and extraocular tissues by plaque assay and by staining for early antigen (EA) and beta-galactosidase (beta-gal), respectively. RESULTS: In latently infected, nonimmunosuppressed control mice, replicating-virus-and viral-antigen-positive cells were not detected in the injected eyes or extraocular tissues. After immunosuppression with methylprednisolone and antibodies, EA and beta-gal were detected, and replicating virus was recovered from the injected eye and from several extraocular sites, including liver, lungs, salivary glands, and kidneys. No virus was recovered from PBLs. beta-Gal- or EA-positive cells were observed in the RPE of most mice, and a few virus-infected cells were also observed in the nuclear layers and ganglion cells. Microscopic changes, including retinal folding and detachment, photoreceptor atrophy, macrophage infiltration, and a few EA-positive cytomegalic cells, were observed in the injected eye of immunosuppressed mice. CONCLUSIONS: After immunosuppression, MCMV reactivates in the injected eye and extraocular tissues, and RPE cells are the initial site of MCMV ocular reactivation in the eye. The timing of virus recovery from all sites suggests that MCMV observed in the injected eye is from in situ reactivation of virus and not from spread of virus from extraocular sites via infected PBLs.

Animals↗
PubMed2005

Infection of retinal neurons during murine cytomegalovirus retinitis.

PURPOSE: Previous results suggest that retinal neurons are infected early during murine cytomegalovirus (MCMV) infection of the inner retina. The purposes of this study were to identify which retinal neurons are infected and to determine the routes by which MCMV spreads in the retina. METHODS: Immunosuppressed (IS) BALB/c mice were inoculated with 5 x 10(3) PFU of MCMV (k181) through the supraciliary route. Injected eyes were collected at several times after inoculation, sectioned, and examined by electron microscopy and by staining for retinal cell antigens and for MCMV early (EA) or late (LA) antigen. RESULTS: MCMV-infected cells were observed in the choroid and RPE by day 3 after infection (PI) and in the inner retina beginning at day 5 PI. At this time, many horizontal and bipolar cells were MCMV-antigen-positive but only rare MCMV-infected amacrine cells (glycine positive or gamma-aminobutyric acid [GABA] positive) or MCMV-infected ganglion cells (NF positive) were observed in the inner retina. At day 10 PI, most virus-infected cells were glial fibrillary acidic protein (GFAP)- and GABA-positive glia. Virions were observed by electron microscopy in the choroid, RPE, and inner nuclear layer of the retina. Although virions were observed in the endothelium of the retinal vessels and the nearby retinal cells, the endothelial cell lining of the retinal vessels remained intact. Both apoptotic cells and necrotic cells were seen in the inner retina. CONCLUSIONS: In the inner retina, horizontal and bipolar cells were the early (< or = day 7 PI) targets of MCMV infection. Virus spread from the RPE and the photoreceptor layer to the inner retina through infected Muller cells and within the inner retina horizontally through infected horizontal cells.

Animals↗
PubMed2005

Expression of endothelial nitric oxide synthase and vascular endothelial growth factor in association with neovascularization in human primary astrocytoma.

OBJECTIVE: To investigate the relationship between the expression of endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF) and angiogenesis in primary astrocytoma. METHODS: Thirty-seven primary astrocytomas and 4 astrocytic hyperplasia samples were collected and divided into three groups according to histological grade. The expression of eNOS, VEGF and factor VIII related antigen (FVIIIRAg) were assayed by immunohistochemistry. Microvascular density was assessed by FVIIIRAg immunoreactivity. The intensity of immunoreactivity was graded according to the percentage of positive tumor cells. RESULTS: No eNOS and VEGF were expressed in the astrocytes and vascular endothelium in astrocytic hyperplasia. The expression of eNOS or VEGF was light in low-grade astrocytoma and strong in glioblastoma. eNOS expression in astrocytoma was very positively correlated with VEGF. eNOS and VEGF expression in anaplastic astrocytoma was median in contrast to the low grade astrocytoma and glioblastoma. Lower microvascular density was found in low grade astrocytoma than that in higher grade malignant ones. The expressions of eNOS and VEGF were correlated with microvascular density and tumor malignancy. CONCLUSION: This finding suggests that eNOS and VEGF may have cooperative effect in tumor angiogenesis and play an important role in the pathogenesis of primary astrocytoma.

Adolescent↗
PubMed2005

[Effect on synthesis of nitric oxide in myocardium by local cryoablation].

OBJECTIVE: To study the effect on synthesis of nitric oxide in myocardium by local cryoablation and to investigate its mechanism. METHODS: Myocardium was cryoablated locally by a probe cooled to -60 degrees C and rewarmed by normal salt solution, nitric oxide and its synthesis enzyme were measured before and after cryoablation. L-arginine or methylene blue was added before and during cryoablation and the effect of these drugs on synthesis of nitric oxide was studied. RESULTS: Nitric oxide and its synthesis enzyme decreased after cryoablation; L-arginine preserved the synthesis of nitric oxide and methylene blue inhibited the synthesis of nitric oxide. However, nitric oxide in serum did not change. CONCLUSION: Nitric oxide and its synthesis enzyme in myocardium decrease after cryoablation.

Animals↗
PubMed2005

[Study of immunoregulation of dendritic cells in allergic rhinitis].

OBJECTIVE: To investigate the immunoregulation of dendritic cells in allergic rhinitis. METHOD: Adopting the cell culture and the enzyme linked immunosorbant assay to examine the patients' Th1/Th2 in the blood. Observing that how is the DC's function in immunoregulation of allergic rhinitis. RESULT: The concentration of the IFN-gamma advanced obviously in post-stimulatory supernatant liquid after using the mature DC. CONCLUSION: The mature dendritic cells can polarize naive T-cells into Th1 effector cells, and are recognized as having a central role in the establishment of T-cell memory and peripheral immune tolerance. DC could be exploited as targets for therapy in asthma and allergic rhinitis.

Adolescent↗
PubMed2005

[Dynamic loads at knee joint of trans-tibial amputee on different terrains].

Dynamic loads at knee joint of amputee are fundamental for rehabilitation of knee injury and prosthesis design. In this paper, a 3-D model for calculation of dynamic load at knee joint of trans-tibial amputee was developed. Gait analysis was done on three terrains including normal level walking, upstairs and downstairs. Dynamic loads at knee joint were calculated during one gait cycle. The results show that gait patterns and dynamic loads at knee joint were different among these three terrains. Although the general waveforms were about the same, the motion range of knee joint, ground reaction forces and loads at knee joint when walking upstairs or downstairs were larger than those in a normal level walking. The quantitative findings provide the theoretical basis of gait analysis and prosthesis design for trans-tibial amputee.

Amputation Stumps↗
PubMed2005

[Effect of multiple micronutrients supplementation on anti-oxidative activity and oxidized DNA damage of lymphocytes in children].

OBJECTIVE: To examine the effect of multiple micronutrients supplementation on anti-oxidative activity and decreasing oxidized DNA damage of lymphocytes in Chinese children. METHODS: 82 healthy children in a rural areas, aged 9-11 years, were selected and randomized allocated into group receiving supplements and control group with each of them 41. 24-hour dietary recall was used to collect data on daily nutrient intakes of the research subjects. The subjects in the supplement group were given vitamin A (VA) 600 microg, beta-carotene (beta-C) 1.0 mg, vitamin E (VE) 100 mg, vitamin C (VC) 300 mg and Na2SeO3(Se) 200 microg in a tablet on daily base while those in the control group took a same-sized color placebo tablet. The trial lasted 8 weeks. 5 ml blood samples from each subject were taken during 7 to 9 o'clock in the morning. DNA damage of lymphocytes and levels of plasma VA, VE, VC, beta-C, Se, malondialdehyde (MDA), activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were then analyzed twice before and after the 8-week of trial. RESULTS: The low intakes of VA, VC and Se only accounted for 50.6%, 65.6% and 67.3% of their recommended nutrient intake (RNI) respectively. After the trial, levels of plasma beta-C, VA, VE, VC and Se in the supplemented group increased by 13.4%, 32.8%, 11.5%, 46.9% and 24.6% respectively, compared with the control group, indicating that nutritional status regarding antioxidant nutrients had largely been improved. GSH-Px activity had a significant increase in the supplement group than before the supplement and in the control group (P < 0.01). GSH-Px before the trial (the 100.4 U/ml) also showed significant increase after the trial (161.7 U/ml) (P < 0.01). However, the values of SOD and MDA significantly decreased after the trial. Analysis of DNA damage indicated that there was no significant difference in the intrinsic damage of DNA (P > 0.05). Significant decreases of oxidized DNA damage induced by 5 micromol/L, 10 micromol/L and 25 micromol/L H2O2 were found more in peripheral lymphocytes of the supplemented group, than in pre-supplement and the control group after the trial (P < 0.01). CONCLUSION: Supplementation of multiple micronutrients could effectively increase the levels of beta-C, VA, VE, VC and Se in plasma, and GSH-Px activity. In the meantime, MDA and oxidized DNA damage induced by a low level H2O2 decreased significantly after the trial. The reason accounted for the decrease of SOD activity after the trial needs to be further studied.

Antioxidants↗