Biomedical subjects

Ming Zhang

Publications and source records attributed to Ming Zhang.

At least 55 records · Page 3Linked to original sources

PubMed2006

MAPK activation and apoptotic alterations in hearts subjected to calcium paradox are attenuated by taurine.

OBJECTIVE: The Ca2+ -paradox is an important phenomenon to study cell injury induced by Ca2+ -overload in myocardium. Although intracellular Ca2+ -overload acts as a trigger and modulator of cell death due to apoptosis under various pathophysiological conditions, the presence of apoptosis in hearts subjected to Ca2+ -paradox has not been demonstrated. Since taurine attenuates the changes in cardiac function due to Ca2+ -paradox, this study investigated the occurrence and mechanisms of apoptosis in Ca2+ -paradoxic hearts treated in the absence and presence of taurine. METHODS: Ca2+ -paradox was induced by perfusing the isolated rat heart with Ca2+ -free medium for 5 min followed by reperfusion with Ca2+ -containing medium for 30 min. Apoptosis related signal transduction mechanisms were determined in Ca2+ -paradoxic hearts perfused with or without 10 mM taurine. RESULTS: Marked alterations in cardiac function and the presence of apoptosis were seen in Ca2+ -paradoxic hearts reperfused for 30 min. Unlike the total protein contents in hearts subjected to Ca2+ -paradox, the contents of phosphorylated p38 mitogen-activated protein kinase (MAPK), extracellular signal regulated kinase (ERK)1, ERK2 and c-jun amino-terminal kinase were increased by 125 +/- 8.6%, 296 +/- 14.3%, 213 +/- 8.5% and 133 +/- 4.2%, respectively vs. control. Caspase-3 and phosphorylated Bcl-2 contents were also increased by 193 +/- 10.2% and 134 +/- 5.0% vs. control whereas phosphorylated Bad and the ratio of Bcl-2/Bad were depressed by 32 +/- 10.8% and 0.23 +/- 0.5% vs. control in Ca2+ -paradoxic hearts. The apoptosis as seen in Ca2+ -paradoxic hearts reperfused for 30 min was not evident in hearts at 10 min Ca2+ -repletion but was similar to hearts subjected to 60 min Ca2+ -repletion. These changes in the apoptotic pathway in cardiomyocytes subjected to Ca2+ -paradox were prevented by taurine. Furthermore, taurine attenuated the KCl- or ATP-induced increase in intracellular concentration of Ca2+ in cardiomyocytes. CONCLUSIONS: This study suggests that cardiac dysfunction due to Ca2+ -paradox may be associated with apoptosis. In addition, the beneficial effects of taurine on cardiac function may be related to the attenuation of changes in MAPK and apoptotic signal transduction mechanisms in Ca2+ -paradoxic hearts.

Adenosine Triphosphate↗

PubMed2006

The clinical study of autologous peripheral blood stem cell transplantation by intracoronary infusion in patients with acute myocardial infarction (AMI).

PURPOSE: To investigate the effects and safety of autologous peripheral blood stem cell (PBSCs) transplantation by intracoronary infusion in patients with acute myocardial infarction (AMI). METHODS: 70 patients with AMI were allocated to two groups, one was PBSCs transplantation group (n=35) that received optimal post-infarction medical treatment (standard drug and coronary artery intervention therapy) and intracoronary transplantation of PBSCs; the other was control group (n=35) that received optimum post-infarction medical treatment (standard drug and coronary artery intervention therapy). The PBSCs transplantation group received granulocyte colony-stimulating factor (G-CSF: Filgrastim, 300 microg) with the dose of 300-600 microg/day to mobilize the stem cell, and the duration of administration G-CSF was 5 days. On the sixth day, PBSCs were separated by Baxter CS 3000 blood cell separator into suspend liquid 57 ml. Then, the suspend liquid was transferred into the infarct-related artery (IRA) by occluding the over-the-wire balloon and infusing artery through balloon center lumen. In the process of the mobilization, separation and intracoronary infusion of PBSCs, the complications have been investigated. Changes in left ventricular function were assessed at 6-month follow-up. RESULTS: 35 cases had finished follow-up in the treated group, while 23 cases in control group. After 6 months, within the treated group, there was a significant improvement in global left ventricular function ejection fraction (EF) from a baseline of 50.0+/-8.2% to 57.1+/-7.8% (P<0.0001), wall motion score index (WMSI) from 1.219+/-0.190 to 1.101+/-0.118 (P<0.0001), left end-systolic volume (ESV) from 63.8+/-23.9 ml to 52.6+/-20.3 ml (P=0.01) and left end-diastolic volume (EDV) from 134.2+/-36.7 ml to 119.2+/-30.3 ml (P=0.07); in the control group, there was no significant improvement in EF, WISM, EDV and ESV (P=0.490, 0.259, 0.117, 0.395). After 6-month follow-up, according to treatment group vs. control group, there was a significant improvement in EF from 57.1+/-7.8 to 52.6+/-5.7 (P=0.041) and WISM from 1.101+/-0.118 to 1.184+/-0.138 (P=0.034). There were a total of 25 cases with complications during the mobilization, separating and infusion of PBSC. The incidence of complications relating to mobilization was 37.1% (13/35), relating to separating was 14.3% (5/35) and relating to intracoronary infusion was 20.0% (7/35). No death was observed. CONCLUSION: Autologous PBSCs transplantation by intracoronary infusion is feasible and safe, and it can improve left ventricular function in the 6-month follow-up.

Aged↗

PubMed2006

jpHMM at GOBICS: a web server to detect genomic recombinations in HIV-1.

Detecting recombinations in the genome sequence of human immunodeficiency virus (HIV-1) is crucial for epidemiological studies and for vaccine development. Herein, we present a web server for subtyping and localization of phylogenetic breakpoints in HIV-1. Our software is based on a jumping profile Hidden Markov Model (jpHMM), a probabilistic generalization of the jumping-alignment approach proposed by Spang et al. The input data for our server is a partial or complete genome sequence from HIV-1; our tool assigns regions of the input sequence to known subtypes of HIV-1 and predicts phylogenetic breakpoints. jpHMM is available online at http://jphmm.gobics.de/.

Genome, Viral↗

PubMed2006

Curcumin-attenuated trinitrobenzene sulphonic acid induces chronic colitis by inhibiting expression of cyclooxygenase-2.

AIM: To explore the possible mechanisms of curcumin in rat colitis induced by trinitrobenzene sulfonic (TNBS) acid. METHODS: Rats with TNBS acid-induced colitis were treated with curcumin (30 mg/kg or 60 mg/kg per day ip). Changes of body weight and histological scores as well as survival rate were evaluated. Leukocyte infiltration was detected by myeloperoxidase (MPO) activity assay. The expression of cyclooxygenase-2 (COX-2) was detected by RT-PCR and Western blot. Inflammation cytokines were determined by RT-PCR. Local concentration of prostaglandin E(2) (PGE(2)) in colon mucosa was determined by ELISA. RESULTS: Curcumin improved survival rate and histological image, decreased the macroscopic scores and MPO activity. Also curcumin reduced the expression of COX-2 and inflammation cytokines. In addition, treatment with curcumin increased the PGE(2) level. CONCLUSION: Curcumin has therapeutic effects on TNBS acid-induced colitis, the mechanisms seem to be related to COX-2 inhibition and PGE(2) improvement.

Animals↗

PubMed2006

The role of natural IgM in myocardial ischemia-reperfusion injury.

Myocardial ischemia-reperfusion injury represents a combination of factors, namely the intrinsic cellular response to ischemia and the extrinsic acute inflammatory response. Recent studies in mesenteric and skeletal muscle reperfusion models identified natural IgM as a major initiator of pathology through the activation of the complement system and inflammatory cells. To determine whether a similar mechanism is involved in myocardial tissues, mice bearing an altered natural IgM repertoire (Cr2-/-) were examined in a murine model of coronary artery ischemia. Notably, these mice were significantly protected based on the reduced infarct size, limited apoptosis of cardiomyocytes, and decreased neutrophil infiltration. Protection was IgM-dependent as reconstitution of these mice with wild-type IgM restored myocardial reperfusion injury. These results support a model in which natural IgM initiates the acute inflammatory response in the myocardium following ischemia and reperfusion.

Animals↗

PubMed2006

ZnO/PS core-shell hybrid microspheres prepared with miniemulsion polymerization.

The hybrid microspheres of ZnO/PS with different core-shell structures were prepared in miniemulsion polymerization. 3-(trimethoxysilyl)propyl methacrylate (MPS) was used as a functional co-monomer to enhance the surface polarity of ZnO nanoparticles and to prevent water from quenching the luminescent properties of ZnO. The morphology of hybrid particles was examined with a transmission electron microscope. The luminescence spectra were measured using a Shimadzu RF-5301 PC spectrofluorimeter (Xe source) at room temperature. The crystallization structure of samples was characterized with a Rigaku wide-angle X-ray diffractometer. The chemical composition and structure of the ZnO colloids, MPS-modified ZnO colloids, and ZnO/PS hybrid microspheres were analyzed with IR.

Journal Article↗

PubMed2006

Maspin is physically associated with [beta]1 integrin regulating cell adhesion in mammary epithelial cells.

Maspin is a tumor-suppressor serpin (serine protease inhibitor), which inhibits cell invasion and migration. Here, we analyzed maspin function in cell adhesion in nontransformed mammary epithelial cells and investigated the underlying mechanism involved in this process. We report that maspin acts in the early steps in the cell adhesion process. Addition of recombinant maspin rapidly increased MCF-10A cell adhesion to the endogenously deposited matrix, and conversely both an antimaspin antibody (Ab) and maspin knockdown by RNA interference resulted in decreased cell adhesion. Mutation analyses revealed that a region of 86 amino acids located between aa 139 and aa 225 was responsible for maspin effect on adhesion. In addition, we show that maspin is associated with detergent-insoluble cortical cytoskeleton elements. Collectively, these results suggest that maspin is part of the supramolecular structure of the adhesion plaque and it modulates cell adhesion via a beta1 integrin-dependent mechanism.

Base Sequence↗

PubMed2006

A jumping profile Hidden Markov Model and applications to recombination sites in HIV and HCV genomes.

BACKGROUND: Jumping alignments have recently been proposed as a strategy to search a given multiple sequence alignment A against a database. Instead of comparing a database sequence S to the multiple alignment or profile as a whole, S is compared and aligned to individual sequences from A. Within this alignment, S can jump between different sequences from A, so different parts of S can be aligned to different sequences from the input multiple alignment. This approach is particularly useful for dealing with recombination events. RESULTS: We developed a jumping profile Hidden Markov Model (jpHMM), a probabilistic generalization of the jumping-alignment approach. Given a partition of the aligned input sequence family into known sequence subtypes, our model can jump between states corresponding to these different subtypes, depending on which subtype is locally most similar to a database sequence. Jumps between different subtypes are indicative of intersubtype recombinations. We applied our method to a large set of genome sequences from human immunodeficiency virus (HIV) and hepatitis C virus (HCV) as well as to simulated recombined genome sequences. CONCLUSION: Our results demonstrate that jumps in our jumping profile HMM often correspond to recombination breakpoints; our approach can therefore be used to detect recombinations in genomic sequences. The recombination breakpoints identified by jpHMM were found to be significantly more accurate than breakpoints defined by traditional methods based on comparing single representative sequences.

Algorithms↗

PubMed2006

Antisense oligonucleotide inhibition of tumor necrosis factor receptor 1 protects the liver from radiation-induced apoptosis.

PURPOSE: Liver damage by radiation limits its efficacy in cancer treatment. As radiation can generate apoptotic signals, we wished to examine the potential to protect the liver by inhibiting apoptosis through two key mediators, FAS and tumor necrosis factor receptor 1 (TNFR1). EXPERIMENTAL DESIGN: Radiation-induced liver damage was assessed by serum aspartate aminotransferase and alanine aminotransferase, hepatocyte micronucleus formation, and apoptosis assays (terminal nucleotidyl transferase-mediated nick end labeling and caspase-3 cleavage) in mice. Protection was evaluated by pretreating mice with antisense oligonucleotides (ASO) for FAS or TNFR1 prior to radiation. TNF-alpha production in liver and in Kupffer cells were determined by ELISA. RESULTS: Radiation increased liver FAS and TNFR1 transcription in a dose- and time-dependent manner (maximized at 25 Gy and 8 hours postirradiation). Pretreatment with ASOs for FAS and TNFR1 resulted in the inhibition of liver FAS and TNFR1 by 78% and 59%, respectively. Inductions of serum aspartate aminotransferase and alanine aminotransferase were observed at 2 hours after radiation and could be reduced by pretreating mice with ASO for TNFR1 but not FAS or control oligonucleotide. Radiation-induced liver apoptosis (terminal nucleotidyl transferase-mediated nick end labeling staining and caspase-3 activation on Western blot) and hepatocyte micronucleus formation were reduced by pretreatment with ASO for TNFR1. In addition, radiation stimulated TNF-alpha production both in irradiated liver and in cultured Kupffer cells by >50% and 100%, respectively. CONCLUSION: This study suggests that ionizing radiation activates apoptotic signaling through TNFR1 in the liver, and thus provides a rationale for anti-TNFR1 apoptotic treatment to prevent radiation-induced liver injury.

Animals↗

PubMed2006

Curcumin inhibits trinitrobenzene sulphonic acid-induced colitis in rats by activation of peroxisome proliferator-activated receptor gamma.

Curcumin is a widely used spice with anti-inflammatory and anti-cancer properties. It has been reported that curcumin held therapeutic effects on experimental colitis by inhibition of nuclear factor kappa B (NF-kappaB). The peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor with anti-tumor and anti-inflammatory effects and its activation may inhibit the nuclear translocation of NF-kappaB. Several studies have shown that PPARgamma ligands had an important therapeutic effect in colitis. However there is no report about the alteration of PPARgamma in trinitrobenzene sulphonic acid (TNBS)-induced colitis treated with curcumin. In this study, we administered curcumin (30 mg/kg/day) by intraperitoneal injection immediately after colitis was induced and the injection lasted for two weeks. have evaluated the effects of curcumin on the colitis induced by trinitrobenzene sulphonic acid (TNBS). Curcumin (30 mg/kg d) was administered by intraperitoneal just after colitis was induced and lasted for two weeks. Therapeutic effects of dexamethasone (Dex, 2 mg/kg d) alone and the combined effects of curcumin+Dex were also examined. We found that curcumin improved long-term survival rate of disease-bearing rats, promoted rat body weight recovery, and decreased macroscopic scores of the colitis. The expression levels of PPARgamma, 15-deoxy-D12,14-prostaglandin J(2) (15d-PGJ(2)) and prostaglandin E(2) (PGE(2)) were all increased, but the expression level of cyclooxygenase-2 (COX-2) was decreased in rats after administration of curcumin. Treatment with Dex improved PPARgamma expression and inhibited the expression of COX-2, 15d-PGJ(2) and PGE(2). Combined effects of curcumin+Dex were similar to that of Dex. In summary, curcumin showed therapeutic effects on TNBS-induced colitis and the mechanisms by which curcumin exerts its effects may involve activation of PPARgamma and its ligands.

Animals↗

PubMed2006

Cluster model analysis of late rectal bleeding after IMRT of prostate cancer: a case-control study.

PURPOSE: Cluster models are newly developed normal-tissue complication probability models in which the spatial aspects of radiation-induced injury are taken into account by considering the size of spatially contiguous aggregates of damaged tissue units. The purpose of this study was to test the validity of a two-dimensional cluster model of late rectal toxicity based on maximum cluster size of damage to rectal surface. METHODS AND MATERIALS: A paired case-control study was performed in which each of 9 patients experiencing Grade 2 or higher late rectal toxicity after intensity-modulated radiation therapy of localized prostate cancer was paired with a patient having a similar rectal dose-surface histogram but free of rectal toxicity. Numeric simulations were performed to determine the distribution of maximum cluster size on each rectal surface for each of many different choices of possible model parameters. RESULTS: Model parameters were found for which patients with rectal toxicity were consistently more likely to have a significantly larger mean maximum cluster size than their matched controls. These parameter values correspond to a 50% probability of tissue-unit damage at doses near 30 Gy. CONCLUSIONS: This study suggests that a cluster model based on maximum cluster size of damage to rectal surface successfully incorporates spatial information beyond that contained in the rectal dose-surface histogram and may therefore provide a useful new tool for predicting rectal normal-tissue complication probability after radiotherapy.

Case-Control Studies↗

PubMed2006

Shear stress regulates forward and reverse planar cell polarity of vascular endothelium in vivo and in vitro.

Cultured vascular endothelium displays profound morphological adaptations to shear stress that include planar cell polarity (PCP) that is directed downstream. Endothelial cells in blood vessels are also polarized; however, the direction of polarity is vessel specific, and shear-independent mechanisms have been inferred. The regulation of endothelial PCP is therefore controversial. We report that the direction of PCP in blood vessels is age and vessel specific; nonetheless, it is caused by shear-related regulation of glycogen synthase kinase-3beta (GSK-3beta), a profound regulator of endothelial microtubule stability. When GSK-3beta is inhibited, PCP reverses direction. Endothelium is the only cell type studied to date that can reverse direction of polarity. Tight regulation of GSK-3beta, microtubule dynamics, and cell polarity was also required for the striking morphological responses of endothelium to shear stress (cell elongation and orientation with shear). Finally, the cytoskeletal polarity displayed in blood vessels is associated with polarized (shear-directed) cell mitoses that have important effects on endothelial repair. Vascular endothelium therefore displays a novel mode of mechanosensitive PCP that represents the first example of a single cell type that can reverse direction of polarity.

Acetylation↗

PubMed2006

Identification of the target self-antigens in reperfusion injury.

Reperfusion injury (RI), a potential life-threatening disorder, represents an acute inflammatory response after periods of ischemia resulting from myocardial infarction, stroke, surgery, or trauma. The recent identification of a monoclonal natural IgM that initiates RI led to the identification of nonmuscle myosin heavy chain type II A and C as the self-targets in two different tissues. These results identify a novel pathway in which the innate response to a highly conserved self-antigen expressed as a result of hypoxic stress results in tissue destruction.

Animals↗

PubMed2006

Regional variations in microstructural properties of vertebral trabeculae with structural groups.

STUDY DESIGN: Micro-computed tomography (CT) scanning to investigate three-dimensional microstructural properties of L4 vertebral bodies. OBJECTIVE: To identify the regional variations in the three-dimensional microstructural properties of vertebral cancellous bones with respect to structural types for the prediction of related regional fracture risks. SUMMARY OF BACKGROUND DATA: The literature contains no reports on regional variations in morphologic properties of vertebral trabeculae with microstructural types, which may shed light on the patterns of osteoporotic fractures. METHODS: Ninety cubic cancellous specimens were obtained from 6 normal L4 vertebral bodies of 6 male donors 62 to 70 years of age and were scanned using a high-resolution micro-CT system. These specimens were further divided into two groups according to the average structure model index (SMI) of the 15 trabecular specimens in each vertebral body. Adjustment for age differences was done for the microstructural parameters, i.e.-, bone volume fraction, trabecular number, trabecular thickness, structure model index, degree of architectural anisotropy, and connectivity density, to allow investigation on the regional variations in different transverse layers and vertical columns independent of age. RESULTS: Trabecular specimens with lower mass were liable to form high-SMI group and the differences in all parameters reached significance level either between columns or between layers from two groups. CONCLUSIONS: The anterior column in the high-SMI group is more susceptible to vertebral body wedge fracture; and in the low-SMI group, off-axis bone damage is most harmful to the central column of vertebral trabeculae. The data obtained may help to identify the most critical locations of fracture risks at an early stage and provide a microstructural basis for the repair and clinical treatment of vertebral fractures.

Aged↗

PubMed2006

Low intensity pulsed ultrasound accelerated bone remodeling during consolidation stage of distraction osteogenesis.

Bone regeneration in distraction osteogenesis occurs under tensile stress with axial rhythmic distraction after osteotomy. In this study, we evaluated if the low intensity pulsed ultrasound (LIPUS) was also effective on enhancement of bone remodeling during consolidation stage of distraction osteogenesis. Open osteotomy of seventeen 18-week-old female New Zealand rabbit tibiae were performed. The distraction was applied with the rate of 1 mm per day. LIPUS (30 mW/cm(2), 1.5 MHz) was delivered for 20 min per day during 4-week consolidation stage (n=10). The animals without treatment served as sham group (n=7). Plain X-ray, peripheral quantitative computational tomography (pQCT), and torsional test were performed. Results showed that smaller radiolucent interzone of LIPUS treatment group was gradually occupied by calcified tissue in plain X-ray at week 2. The bone mineral density (BMD) measured on radiographs increased by 9.18% in the LIPUS group. Bone mineral content (BMC), hard callus volume, and bone strength index (BSI) measured by pQCT were 83%, 116%, and 94%, respectively, in LIPUS group that were significantly greater than those of the controls. At the 4th week, LIPUS-treated callus showed the development of neocorticalization in the proximal and distal region. The BMC, hard callus volume, and BSI of LIPUS group decreased and was not significantly different from control. This was also confirmed by the maximum torque of LIPUS-treated callus (1424.2+/-457.3 N . mm) obtained at week 4, which did not differ from that of the sham group (1968.8+/-895.1 N . mm). In conclusion, the effective period of LIPUS treatment was at the initial stage of consolidation, with accelerated bone formation and remodeling.

Animals↗

PubMed2006

Analysis of placental growth factor in placentas of normal pregnant women and women with hypertensive disorders of pregnancy.

To investigate the expressions of placental growth factor (PLGF) in placenta with hypertensive disorders of pregnancy (HDP), 45 women with HDP and 20 normally pregnant women were studied. Among 45 women with HDP, there were 23 cases of severe preeclampsia and one case of eclampsia. The location and level of PLGF proteins was determined by immunohistochemistry and Western blot. The expression of PLGF mRNA in placenta was assessed by reverse transcriptional-polymerase chain reaction (RT-PCR). The results showed that: (1) The distribution of PLGF in placenta with HDP was similar to normal one, which was mainly in the cytoplasm of villous syncytiotrophoblast and villous stroma; (2) The expression of PLGF protein was significantly decreased in placentas with mild and severe preeclampsia compared to the normal ones (0.3 +/- 0.4 vs 0.6 +/- 0.4, 0.2 +/- 0.5 vs 0.6 +/- 0.4, P < 0.01). There were no differences between the gestational hypertension placenta and normal one (0.5 +/- 0.6 vs 0.6 +/- 0.4, P > 0.05); (3) The transcription levels of the PLGF mRNA in placentas with preeclampsia were significantly lower than in normal groups (3.33 +/- 0.39 vs 4.87 +/- 0.60, 1.97 +/- 0.29 vs 4.87 +/- 0.60, P < 0.01), and no differences were found between the gestational hypertension placenta and normal groups. These findings suggest that the abnormal expression of PLGF in placentas is related to the pathogenesis of HDP.

Adult↗

PubMed2006

Is the anatomical protrusion on the posterior hypopharyngeal wall associated with cadavers of only the elderly?

Cricopharyngeal bars are commonly seen on a barium swallow radiologic examination and represent the failure of the cricopharyngeus to relax. Traditionally, the bars have been considered as functional or physiologic protrusions. Recently, anatomical cricopharyngeal protrusion has been found in about 30% of cadavers of the elderly, suggesting that such a structural change may become a physical barrier that affects the normal deglutition in a living person. This suggests that such a radiographic finding should be carefully considered when interpreting radiologic and manometrical examinations and managing dysphagia of the elderly. However, the finding of the anatomical cricopharyngeal protrusion was based on the observation of cadavers of the elderly (mean age = 77 years). The aim of this study was to further investigate whether such an anatomical cricopharyngeal protrusion exists in cadavers of other ages. Using the dissection method, we examined 63 human cadavers that were divided into three age groups: young adult (6 females and 10 males, age = 16-24 years old), adult (8 females and 23 males, age = 25-64 years old), and early elderly (5 females and 11 males, age = 65-69 years old). We found that 57 of the 63 cadavers had a smooth mucosal surface on the posterior hypopharyngeal and upper esophageal wall. A slightly thickened posterior muscular wall was observed at the cricoid level in six cadavers (five from the adult group and one from the early elderly group), but its boundary was not clearly identified. Taking the previous reports together, our results suggest that an anatomical cricopharyngeal protrusion is closely associated with the aging process.

Adolescent↗

PubMed2006

Theoretical analysis of contributions of disuse, basic multicellular unit activation threshold, and osteoblastic formation threshold to changes in bone mineral density at menopause.

Although bone loss at menopause is known to be associated with disuse and estrogen deficit, their contributions and mechanisms are not completely clear. This article presents a computer simulation aimed at clarifying the contributions of various factors that may be responsible for osteoporosis in women. We utilized a mechanical-biological coupled model at the level of basic multicellular units (BMUs) to quantify disuse, changes in BMU activation threshold, and changes in osteoblastic formation threshold on a representative cross section of 100 mm(2) of cancellous bone in the lumbar spine of a postmenopausal woman. The separate and combined contributions were determined by a total of 17 parametrical analyses through comparison to clinical data presented in the literature. An increase in osteoblastic formation threshold alone cannot explain the bone loss patterns seen clinically. Bone mineral density predictions were much closer to the clinical data for the simulation of a maintained increase in BMU activation threshold during menopause or some time after menopause. Maintained disuse alone would result in high rates of bone loss long after menopause. A combination of disuse and an increase in osteoblastic formation threshold, or of an increase in BMU activation threshold and an increase in osteoblastic formation threshold, or of disuse and an increase in BMU activation threshold, or a combination of these three is capable of describing the bone loss found at menopause. It was found that disuse and an increase in the BMU activation threshold may be the major contributors to bone loss at menopause. Understanding the contributions of disuse and the changes in the BMU activation threshold and in the osteoblastic formation threshold that occur at menopause may help to gain more insight into the mechanism of osteoporosis and identify improved osteoporosis treatment and prevention.

Bone Density↗