[Effects of heavy-load exercise on skeletal muscle cells apoptosis and mechanisms of mitochondrial apoptosis in rats].

OBJECTIVE: To analyze the molecular mechanisms of skeletal muscle cells apoptosis induced by heavy-load exercise with Omi as the entry point. METHODS: One hundred and twenty-six adult SD rats were randomly divided into five groups: control group(C), eccentric exercise group (E), simple blocking group (U), DMSO group (D) and exercise block group (EU). In addition to the C group, the other four groups were randomly divided into 0 h after experiment, 12 h after experiment, 24 h after experiment, 48 h after experiment and 72 h after experiment with 6 rats in each group. E and EU group were submitted to a heavy-load exercise on a treadmill down a 16° decline, 16 m/min for 90 minutes. U, D and EU group were one-time intervened with drugs. U and EU groups were intraperitoneally injected with 1.5 µmol/kg ucf-101, D group were intraperitoneally injected with 1.5 µmoL/kg 0.5% DMSO. The rats were sacrificed in batches at different time points after experiment, then the soleus were saved to detect the Caspase-3,-8,-9,-12 activities and protein expressions of Omi and XIAP. RESULTS: Compared with group C, the mitochondrial distribution and morphology appeared the typical ultrastructure pathological changes, the opening degree of MPTP was increased significantly (P＜0.01) or (P＜0.05), protein expressions of Omi and XIAP were increased significantly (P＜0.01 or P＜0.05), the activities of Caspase-9 and Caspase-3 were increased significantly (P＜0.01 or P＜0.05) in group E. Compared with group C, there was no significant difference in XIAP protein and caspase-9, - 3 activities in group U and Group D. The change trend of XIAP protein and Caspase-9, - 3 activities was the same as those between EU group and E group, but the change range of XIAP protein in EU group was significantly higher than that in E group (P＜0.01), and the change ranges of caspase-9, - 3 activities in EU group were significantly lower than those in E group (P＜0.01). CONCLUSION: A single heavy-load exercise can induce changes in the mitochondria morphology and structure in rats, open the high permeability of MPTP, and improve the expression of Omi protein, then through its downstream XIAP-Caspase pathway, start the mitochondrial apoptosis pathway mediated by caspase-9, and finally lead to myocyte apoptosis. The inhibition of Omi can reduce the cell apoptosis level of motor induced skeletal muscle cells.

Supramolecular hydrogel-infiltrated ceramics composite coating with combined antibacterial and self-lubricating performance.

Inspired by the structure and dynamic weeping lubricating mechanism of articular cartilage, a novel composite coating composed of a textured Y2O3-stabilized ZrO2 (YSZ) ceramics reservoir and silver nanoparticles (AgNPs) hybrid supramolecular hydrogel was developed on the basis of a soft/hard combination strategy. The precursor solution including the poly(ethylene glycol) (PEG)-modified AgNPs and α-cyclodextrins (α-CDs) could be infiltrated deep into (50-60 µm) the pores of a textured YSZ ceramics substrate by a vacuum infiltration method, in situ forming a supramolecular hydrogel within the pores through host-guest inclusion between α-CDs and PEG chains distributed onto the surface of AgNPs. The AgNPs hybrid hydrogel showed thixotropic and thermoresponsive gel-sol transition behavior, low cytotoxicity, and excellent drug-loading capacity, as well as significant antibacterial properties. The textured YSZ ceramics not only provided a hard supporting skeleton and stable reservoir to protect the supramolecular hydrogel from destruction under load-bearing or shear condition, but also allowed retaining the stimuli-responsive gel-sol transition property and drug-release capability of the infiltrated hydrogel, endowing the composite coating with excellent antibacterial properties, and self-lubrication and wear-resistance performance. The composite coating in this work brings a new insight into the design of antibacterial and self-lubricating ceramic coatings for artificial joint applications.

Structure Identification and In Vitro Anticancer Activity of Lathyrol-3-phenylacetate-5,15-diacetate.

Natural products from the genus Euphorbia show attention-attracting activities, such as anticancer activity. In this article, classical isolation and structure identification were used in a study on Caper Euphorbia Seed. Subsequently, MTT and wound healing assays, flow cytometry, western blotting, Hoechst 33258 staining and fluorescence microscopy examination were applied to investigate the anticancer activity of the obtained compounds. In a result, lathyrol-3-phenyl- acetate-5,15-diacetate (deoxy Euphorbia factor L1, DEFL1) was isolated from Caper Euphorbia Seed. Moreover, the NMR signals were totally assigned. DEFL1 showed potent inhibition against lung cancer A549 cells, with an IC50 value of 17.51 ± 0.85 µM. Furthermore, DEFL1 suppressed wound healing of A549 cells in a concentration-dependent manner. Mechanically, DEFL1 induced apoptosis, with involvement of an increase of reactive oxygen species (ROS), decrease of mitochondrial membrane potential (ΔΨm), release of cytochrome c, activity raise of caspase-9 and 3. Characteristic features of apoptosis were observed by fluorescence microscopy. In summary, DEFL1 inhibited growth and induced apoptosis in lung cancer A549 cells via a mitochondrial pathway.

Degradation of P-glycoprotein by pristimerin contributes to overcoming ABCB1-mediated chemotherapeutic drug resistance in vitro.

ABCB1 (P-glycoprotein, ABCB1/MDR1) is one of the major members of the ABC transporters linked to MDR in cancer cells. In this study, we observed that pristimerin, a natural triterpenoid, potently decreased P-gp in a dose-dependent manner in both drug-resistant KBv200 and stable transfected HEK293/ABCB1 cell lines. Moreover, pristimerin also inhibited cell proliferation and induced apoptosis in both cell lines. Intriguingly, reverse transcription-PCR, real-time PCR and protein turn-over assay revealed that the decrease of P-gp was independent of mRNA level but primarily owing to its protein stability. Furthermore, immunofluorescence study with anti-P-gp antibody showed that pristimerin disturbed the subcellular distribution of P-gp with decreased location in the plasma membrane. Taken together, these data suggest that subcellular distribution of P-gp and subsequent downregulation by pristimerin contribute to overcoming ABCB1-mediated chemotherapeutic drug resistance. Our findings suggested inducing the decrease of P-gp membrane protein could be a new promising alternative therapeutic strategy in ABCB1-mediated MDR.

[The relationship of ECG and pregnancy outcome of older pregnant woman in late pregnancy].

OBJECTIVE: To observe the changes of electrocardiogram (ECG) and pregnancy outcome of the late pregnancy women. METHODS: Late pregnancy women were divided into two groups by age: over 35 group and under 35 group. The incidence of abnormal electrocardiogram was recorded when the patients were subjected to routine ECG examination. Then the pregnancy, delivery outcome and if there's low birth weight newborn were recorded later. RESULTS: The incidence of abnormal ECG in over 35 group was significantly higher than that in under 35 group (P < 0.05). And the incidence of ST segment changes, arrhythmia in the group of former was higher than that in the group of latter (P < 0.05). Among the different type of arrhythmia, the incidence of sinus bradycardia and ventricular premature beat in the group of former were higher than those in the group of latter (P < 0.05). But the incidence of sinus tachycardia in the former group was obviously lower than that in the latter group (P < 0.05). The incidence of pregnancy loss in over 35 with abnormal ECG group was significantly higher than that in under 35 with normal or abnormal ECG groups (P < 0.05). The incidence of premature birth in over 35 with abnormal ECG group was significantly higher than that in over 35 with normal ECG group (P < 0.05). The incidence of low body weight in over 35 with abnormal ECG group was significantly higher than that in under 35 with normal ECG group (P < 0.05). CONCLUSION: The late pregnancy women with the age of over 35 are more likely to have ECG abnormalities, such as arrhythmia, myocardial ischemia and so on. The older pregnant women with abnormal ECG easily suffer from pregnancy losing, premature birth and having a low birth weight baby.

Proteomic analysis of synovial fibroblast-like synoviocytes from rheumatoid arthritis.

OBJECTIVES: The purpose of this study was to identity protein expression patterns of fibroblast-like synoviocytes (FLSs) derived from the synovial tissue of patients with rheumatoid arthritis (RA) and osteoarthritis. METHODS: Two-dimensional gel electrophoresis (2-DE) in combination with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) was used to visualise and identify differential cellular protein expression profiles in FLSs between RA and control groups. Western-blot analysis was performed to further verify selected differentially-expressed proteins. RESULTS: A total of 1633 and 1603 protein spots were examined in synovial FLSs of RA patients and controls, respectively. Ninety-two spots in the RA group were statistically over- or under-expressed compared with controls. Among them, 33 proteins over-expressed by more than 3-fold were then identified by MALDI-TOF-MS analysis. These proteins included enzymatic and structural proteins (e.g. PKM1/M2, α-enolase, ERp60, lamin-A/C), signal transduction proteins (e.g. annexin 11, peroxiredoxin 1, TrpRS), heat-shock/chaperone proteins (e.g. TCP-1, GRP75, HspB5, Bip) and some unknown protein species. Three proteins, namely α-enolase, GRP75 and PKM2, were verified by Western blot and the results were found to be consistent with proteomic analysis. CONCLUSIONS: The differentially expressed proteins identified in RA synovial FLSs might be candidate RA-associated proteins and may prove to be promising diagnostic indicators or new therapeutic targets for RA.

Tandutinib (MLN518/CT53518) targeted to stem-like cells by inhibiting the function of ATP-binding cassette subfamily G member 2.

Tandutinib is a novel inhibitor of tyrosine kinases FLT3, PDGFR and KIT. Our study was to explore the capability of tandutinib to reverse ABC transporter-mediated multidrug resistance. Tandutinib reversed ABCG2-mediated drug resistance in ABCG2-482-R2, ABCG2-482-G2, ABCG2-482-T7 and S1-M1-80 cells and increased the accumulation of doxorubicin, rhodamine 123 and [H(3)] mitoxantrone in ABCG2-overexpressing cells. Importantly, tandutinib selectively sensitized side population cells to mitoxantrone. Taken together, our results advocate the potency of tandutinib as an ABCG2 modulator and stem-like cells targeted agent to increase efficiency of anticancer drugs.

BIRB796, the inhibitor of p38 mitogen-activated protein kinase, enhances the efficacy of chemotherapeutic agents in ABCB1 overexpression cells.

ATP-binding-cassette family membrane proteins play an important role in multidrug resistance. In this study, we investigated BIRB796, an orally active inhibitor of p38 mitogen-activated protein kinase, reversed MDR induced by ABCB1, ABCG2 and ABCC1. Our results showed that BIRB796 could reverse ABCB1-mediated MDR in both the drug selected and transfected ABCB1-overexpressing cell models, but did not enhance the efficacy of substrate-chemotherapeutical agents in ABCC1 or ABCG2 overexpression cells and their parental sensitive cells. Furthermore, BIRB796 increased the intracellular accumulation of the ABCB1 substrates, such as rhodamine 123 and doxorubicin. Moreover, BIRB796 bidirectionally mediated the ATPase activity of ABCB1, stimulating at low concentration, inhibiting at high concentration. However, BIRB796 did not alter the expression of ABCB1 both at protein and mRNA level. The down-regulation of p38 by siRNA neither affected the expression of ABCB1 nor the cytotoxic effect of paclitaxel on KBV200. The binding model of BIRB796 within the large cavity of the transmembrane region of ABCB1 may form the basis for future lead optimization studies. Importantly, BIRB796 also enhanced the effect of paclitaxel on the inhibition of growth of the ABCB1-overexpressing KBV200 cell xenografts in nude mice. Overall, we conclude that BIRB796 reverses ABCB1-mediated MDR by directly inhibiting its transport function. These findings may be useful for cancer combinational therapy with BIRB796 in the clinic.

Effect of dicycloplatin, a novel platinum chemotherapeutical drug, on inhibiting cell growth and inducing cell apoptosis.

Dicycloplatin, a new supramolecular platinum-based antitumor drug, has been approved by the State Food and Administration (SFDA) of China. In this study, we investigated the anticancer activity of dicycloplatin in cancer cells and signaling pathways involved in dicycloplatin-induced apoptosis. Dicycloplatin inhibited the proliferation of cancer cells and increased the percentage of apoptosis in a concentration-dependent manner. Besides, some apoptosis related events were observed after treatment with dicycloplatin, including increase of reactive oxygen species (ROS), collapse of mitochondrial membrane potential (Δψm), release of cytochrome c from the mitochondria to the cytosol, upregulation of p53, which were accompanied by activation of caspase-9, caspase-3, caspase-8, and poly (ADP-ribose) polymerase cleavage in a concentration-dependent manner. The role of apoptosis in dicycloplatin-mediated cell death was further confirmed by the concomitant treatment with caspase-8 or caspase-9 inhibitors, which inhibited apoptosis and PARP cleavage. Intracellular glutathione (GSH) was also found to inhibit the cytotoxic effect of dicycloplatin. In conclusion, these findings suggest that dicycloplatin induces apoptosis through ROS stress-mediated death receptor pathway and mitochondrial pathway which is similar to carboplatin.

Enhancing chemosensitivity in ABCB1- and ABCG2-overexpressing cells and cancer stem-like cells by an Aurora kinase inhibitor CCT129202.

Imidazopyridine CCT129202 is an inhibitor of Aurora kinase activity and displays a favorable antineoplastic effect in preclinical studies. Here, we investigated the enhanced effect of CCT129202 on the cytotoxicity of chemotherapeutic drugs in multidrug resistant (MDR) cells with overexpression of ATP-binding cassette (ABC) transporters and cancer stem-like cells. CCT129202 of more than 90% cell survival concentration significantly enhanced the cytotoxicity of substrate drugs and increased the intracellular accumulations of doxorubicin and rhodamine 123 in ABCB1 and ABCG2 overexpressing cells, while no effect was found on parental sensitive cells. Interestingly, CCT129202 also potentiated the sensitivity of cancer stem-like cells to doxorubicin. Importantly, CCT129202 increased the inhibitory effect of vincristine and paclitaxel on ABCB1 overexpressing KBv200 cell xenografts in nude mice and human esophageal cancer tissue overexpressing ABCB1 ex vivo, respectively. Furthermore, the ATPase activity of ABCB1 was inhibited by CCT129202. Homology modeling predicted the binding conformation of CCT129202 within the large hydrophobic cavity of ABCB1. On the other hand, CCT129202 neither apparently altered the expression levels of ABCB1 and ABCG2 nor inhibited the activity of Aurora kinases in MDR cells under the concentration of reversal MDR. In conclusion, CCT129202 significantly reversed ABCB1- and ABCG2-mediated MDR in vitro, in vivo and ex vivo by inhibiting the function of their transporters and enhanced the eradication of cancer stem-like cells by chemotherapeutic agents. CCT129202 may be a candidate as MDR reversal agent for antineoplastic combination therapy and merits further clinical investigation.

Neratinib reverses ATP-binding cassette B1-mediated chemotherapeutic drug resistance in vitro, in vivo, and ex vivo.

Neratinib, an irreversible inhibitor of epidermal growth factor receptor and human epidermal receptor 2, is in phase III clinical trials for patients with human epidermal receptor 2-positive, locally advanced or metastatic breast cancer. The objective of this study was to explore the ability of neratinib to reverse tumor multidrug resistance attributable to overexpression of ATP-binding cassette (ABC) transporters. Our results showed that neratinib remarkably enhanced the sensitivity of ABCB1-overexpressing cells to ABCB1 substrates. It is noteworthy that neratinib augmented the effect of chemotherapeutic agents in inhibiting the growth of ABCB1-overexpressing primary leukemia blasts and KBv200 cell xenografts in nude mice. Furthermore, neratinib increased doxorubicin accumulation in ABCB1-overexpressing cell lines and Rhodamine 123 accumulation in ABCB1-overexpressing cell lines and primary leukemia blasts. Neratinib stimulated the ATPase activity of ABCB1 at low concentrations but inhibited it at high concentrations. Likewise, neratinib inhibited the photolabeling of ABCB1 with [(125)I]iodoarylazidoprazosin in a concentration-dependent manner (IC(50) = 0.24 µM). Neither the expression of ABCB1 at the mRNA and protein levels nor the phosphorylation of Akt was affected by neratinib at reversal concentrations. Docking simulation results were consistent with the binding conformation of neratinib within the large cavity of the transmembrane region of ABCB1, which provides computational support for the cross-reactivity of tyrosine kinase inhibitors with human ABCB1. In conclusion, neratinib can reverse ABCB1-mediated multidrug resistance in vitro, ex vivo, and in vivo by inhibiting its transport function.

Structure identification of Euphorbia factor L3 and its induction of apoptosis through the mitochondrial pathway.

In this article, we have focused on the structure identification of Euphorbia factor L3 belonging to the lathyrane diterpenoids isolated from Caper Euphorbia Seed. Its anticancer activity in vitro against lung cancer A549 cells was also investigated and the IC(50) values were 34.04 ± 3.99 µM. Furthermore, Euphorbia factor L3 could induce apoptosis in A549 cells via the mitochondrial pathway including loss of mitochondrial potential and release of cytochrome c.

[Effect of down-regulation of Id3 expression by microRNA on proliferation and apoptosis of A549 cells].

AIM: To investigate the effect of microRNA-mediated exogenous Id3 gene silencing on proliferation and apoptosis of human lung adenocarcinoma A549 cells in vitro. METHODS: A recombinant miRNA expression vector (pcDNA6.2-GW/EmGFPmiR-Id3, pcDNA/miRId3) which targets human Id3 gene was constructed. After 24 h of transfection, the transfection efficiency was monitored by inverted fluorescence microscopy.EGFP expression efficiency in A549 cells was analyzed by flow cytometry (FCM).Id3 expression vector pEGFP/Id3 and pcDNA/miRId3 were cotransfected into A549 cells by liposome-mediated method. After 24 h of transfection, the transfection efficiency was monitored by inverted fluorescence microscopy.Semi-quantitative RT-PCR and Western blot were used for identifying Id3 mRNA and protein expression respectively in A549 cells after transfection. Cell proliferation rate and apoptosis ratio were evaluated by MTT assay and Annexin V/7-ADD staining followed by FCM to observe the down-regulatory effect of Id3 expression by miRNA-mediated RNA interference (RNAi). RESULTS: pcDNA/miRId3 and pEGFP/Id3 were successfully transfected into A549 cells. RT-PCR and Western blot results showed that after 24 h of cotransfection of pEGFP/Id3 and pcDNA/miRId3 in A549 cells, the exogenous expression of Id3 both at mRNA and protein levels were significantly reduced compared with the pEGFP/Id3 group. MTT assay and Annexin V/7-AAD staining showed that after 24 h of transfection with pEGFP/Id3, the proliferation rates were significantly reduced and apoptotic cell ratios were significantly higher than those of pEGFP-transfected cells.Whereas there were not any significant differences in proliferation rates or apoptotic cell ratios between pcDNA/miRId3+pEGFP/Id3 cotransfected group and pEGFP or miRNA negative controls. CONCLUSION: Exogenous expression of Id3 in A549 cells could inhibit proliferation and induce apoptosis of A549 cells. Cotransfection of pcDNA/miRId3 and pEGFP/Id3 into A549 could reverse the Id3-induced proliferation inhibition and apoptosis. Construction and application of Id3-targeting miRNA expression vector may build some foundations for investigation the mechanisms of Id3-induced proliferation inhibition and apoptosis in A549 cells.

[The change of thioredoxin system in myocardial tissue of type 2 diabetic rats undergoing myocardial injury].

The aim of the present study is to investigate the change of thioredoxin (Trx) system in myocardial tissue of type 2 diabetic rats after myocardial injury and the underlying mechanism. Adult Sprague Dawley rats were randomly divided into two groups: normal control (NC) group and diabetes (DM) group. Rats in DM group were subjected to high-sugar, high-fat diet and streptozotocin (STZ) injection. Rats in NC group were only given normal diet and equal amount of citric acid buffer injection. At week 1, 2, 4, 12, 21 after STZ injection, plasma glucose concentration and the concentrations of insulin, creatine kinase MB (CK-MB), cardiac troponin I (cTnI) in serum were measured. Myocardial Trx and thioredoxin reductase (TR) activities, as well as caspase-3 activity, were determined by respective assay methods. Protein and mRNA levels of Trx, TR, Trx interacting protein (TXNIP) were determined by Western blot and real time PCR, respectively. The results showed that type 2 diabetic rat model was successfully established at week 1 after STZ injection, and myocardial injury was induced from week 2. Moreover, caspase-3 activity was significantly increased at week 4, 12 in diabetic rats. The activities of myocardial Trx and TR in diabetic rats was decreased from week 2, and continually aggravated as the disease developed. Compared with those in NC group, the mRNA levels of Trx1, Trx2, TR1, TR2 in DM group decreased at week 4, and then increased in week 12. In DM group, the protein levels of Trx1, Trx2, TR1 and TR2 increased significantly at week 12. The mRNA expressions of myocardial TXNIP in diabetic rats were significantly increased at week 4, 12, 24 and protein expression was increased at week 12. These results suggest diabetes can decrease myocardial Trx, TR activity, inducing myocardial cell apoptosis and heart injury. The inhibitory effect of diabetes is mainly associated with TXNIP up-regulation and Trx nitration.

[Release of S100beta and IL-6 into cerebrospinal fluid after aortic operation assisted by two different cerebral protective methods].

OBJECTIVE: To evaluate the clinical efficacy of two brain protective methods for aortic operation according to S100beta protein (S100beta) and interleukin-6 (IL-6) in cerebrospinal fluid (CSF). METHODS: From November 2004 to April 2005, 14 patients who underwent aortic operations with circulatory arrest were alternatively allocated to one of two methods of brain protection: only deep hypothermic circulatory arrest (core temperature, 18 degrees C) for descending thoracic aorta operations (group DHCA, n = 5) or selective antegrade cerebral perfusion (core temperature, 20 degrees C; flow rate, 10 ml kg(-1) min(-1)) for aortic arch operations with DHCA (group ASCP, n = 9). Indications for surgical intervention were Stanford type A dissection in 11 patients, Stanford type B dissection in 2 patients, false aneurysm on thoracoabdominal aorta in 1 patient. S100beta and IL-6 in CSF were assayed in all patients from each group before cardiopulmonary bypass, as well as 0, 6, 12, 24, 48, 72 h after the operation. RESULTS: There were no significant differences in lowest core temperature (P > 0.05), hematocrit in lowest core temperature (P > 0.05) and the velocity of rewarming. Mean circulatory arrest time in ASCP group was significant longer than in DHCA group (P < 0.05). There were much more patients with jugular arteries impaired or accompanied with related cerebrovascular diseases in group ASCP compared to group DHCA. The baseline of S100beta in CSF before cardiopulmonary bypass was no difference. S100beta value in CSF ascended to peak level in 12 h after the operation, showing significantly higher in group DHCA than in group ASCP [DHCA vs. ASCP, (0.90 +/- 0.11) microg/ml vs. (0.61 +/- 0.26) pg/ml]. In most hours after operation there was significant intergroup difference. IL-6 value in CSF ascended to peak level in 12 h postoperative for group DHCA and 0 h postoperative for group ASCP. There was no significance difference observed in IL-6 of CSF between two groups except 6 h and 12 h postoperative. CONCLUSIONS: Brain ischemic injury occurred during aortic operations assisted by brain protective methods is not serious. Unilateral ASCP which can delivery adequate oxygen to brain during circulation arrest has some advantage of alleviating ischemic injury compared with only DHCA.

[Expression of MMP-2 and MMP-3 in periodontal tissues of rat periodontitis model].

OBJECTIVE: To investigate the expression of MMP-2 and MMP-3 in periodontal tissues of rat periodontitis model at different stages of inflammation of varied severity. METHODS: The periodontal tissues were immunohistochemically stained by antibody of MMP-2 and MMP-3. RESULTS: MMP-2 and MMP-3 were both strongly positive in gingival epithelia and fibroblasts in periodontal ligament in rat periodontitis model. And chronic periodontitis showed lower expression of MMP-2 and MMP-3 than that of acute gingivitis and acute peridontitis. CONCLUSION: The expression of MMP-2 and MMP-3 varies in different stage of periodontitis. MMP-2 and MMP-3 may play an important role in development of periodontitis.

[Expression of type III collagen mRNA in rat periodontal ligamemt in response to different occlusal force].

OBJECTIVE: To investigate the altered expression level of type III collagen mRNA in the periodontal ligament of rat molar in response to changes in occlusal force. METHODS: A model of the rat experimental occlusal trauma was established, in which the occlusal surface on the upper first molar of (250+/-20) g male SD rats was approximately 1 mm elevated unilaterally. Another model was establishde, in which the upper first molar was extracted to remove occlusal force against the lower first molar. The rats were perfusion-fixed at 12 h and on the 3rd, 7th, 14th and 30th day after treatment. The prepared sagittal sections were processed to study the expression of type III collagen mRNA in rat periondontal ligament by in situ hynbridization. RESULTS: Following the bite-raising,the number and the desity of the positive cells of type III collagen mRNA in the periodontal ligament of the lower first molar increased gradually. The expression of type III collagen mRNA was the strongest on the 7th day (124.03 +/- 14.82). Comparde to the normal rats,the expression level of type III collagen mRNA in the periodontal ligament of the lower first molar significantly decreased on the 14th day (63.07 +/- 5.69). When occlusal force was removed the expression level of type III collagen mRNA in the periodontal ligament of the lower first molar showed a rapid decrease. Subsequently, a gradual increase was recognized. Compared to the normal animal,a more significant increase (154.39 +/- 17.61) was detected on the 7th day after occlusal force was removed. CONCLUSION: The results suggest that type III collagen may play important roles in the process of periodontium remodeling against different occlusal force.