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Biomedical subjects

Yan Liu

Publications and source records attributed to Yan Liu.

At least 325 records · Page 18Linked to original sources
PubMed2004

[Reasons why the quality of medico-legal autopsy in the medical tangle varies from two areas].

OBJECTIVE: To study reasons that the quality of medico-legal autopsy in the medical tangle varies from different area. METHODS: Collecting the cases of medical tangle in two medico-legal agencies, then counting percent of classes on the ten key-points, analyzing the data of the cases by chi-square test and t-test. RESULTS: It is indicated that the applied methods and standards of the two agencies are different. There are more different in seven keypoint of medicolegal autopsy by chi-square test. CONCLUSION: Six key-points are found to be more important to medico-legal appraiser, standardization of forensic autopsy, standardization of picking up specimen from the body, diagnosis standardization of the cause of death, consultation system and standardization of writing documents on medico-legal autopsy.

Analysis of Variance↗
PubMed2003

Prevention of glucocorticoid-induced apoptosis in osteocytes and osteoblasts by calbindin-D28k.

UNLABELLED: This study show for the first time that calbindin-D28k can prevent glucocorticoid-induced bone cell death. The anti-apoptotic effect of calbindin-D28k involves inhibition of glucocorticoid induced caspase 3 activation as well as ERK activation. INTRODUCTION: Recent studies have indicated that deleterious effects of glucocorticoids on bone involve increased apoptosis of osteocytes and osteoblasts. Because the calcium-binding protein calbindin-D28k has been reported to be anti-apoptotic in different cell types and in response to a variety of insults, we investigated whether calbindin-D28k could protect against glucocorticoid-induced cell death in bone cells. MATERIALS AND METHODS: Apoptosis was induced by addition of dexamethasone (dex; 10-6 M) for 6 h to MLO-Y4 osteocytic cells as well as to osteoblastic cells. Apoptosis percentage was determined by examining the nuclear morphology of transfected cells. Caspase 3 activity was evaluated in bone cells and in vitro. SELDI mass spectrometry (MS) was used to examine calbindin-D28k-caspase 3 interaction. Phosphorylation of calbindin-D28k was examined by 32P incorporation as well as by MALDI-TOF MS. ERK activation was determined by Western blot. RESULTS: The pro-apoptotic effect of dex in MLO-Y4 cells was completely inhibited in cells transfected with calbindin-D28k cDNA (5.6% apoptosis in calbindin-D28k transfected cells compared with 16.2% apoptosis in vector-transfected cells, p < 0.05). Similar results were observed in osteoblastic cells. We found that dex-induced apoptosis in bone cells was accompanied by an increase in caspase 3 activity. This increase in caspase 3 activity was inhibited in the presence of calbindin-D28k. In vitro assays indicated a concentration-dependent inhibition of caspase 3 by calbindin-D28k (Ki = 0.22 microM). Calbindin-D28k was found to inhibit caspase 3 specifically because the activity of other caspases was unaffected by calbindin-D28k. The anti-apoptotic effect of calbindin-D28k in response to dex was also reproducibly associated with an increase in the phosphorylation of ERK 1 and 2, suggesting that calbindin-D28k affects more than one signal in the glucocorticoid-induced apoptotic pathway. CONCLUSION: Calbindin-D28k, a natural non-oncogenic protein, could be an important target in the therapeutic intervention of glucocorticoid-induced osteoporosis.

Animals↗
PubMed2003

[Cephalometric comparison of hard-tissue morphology between extraction and non-extraction orthodontic treatment in borderline cases].

OBJECTIVE: To compare hard-tissue morphology by cephalometric measurements between extraction and non-extraction orthodontic treatment in borderline cases. METHODS: The samples consisted of 33 cases selected as borderline cases by 5 orthodontic specialists. They were divided into 21 extraction cases (including 13 four first premolar extraction cases and 8 second premolar extraction cases) and 12 nonextraction cases by checking patients' treatment records. Conventional cephalometric analysis was made to compare hard tissue structures before and after orthodontic treatment and the same comparison was made between two different extraction patterns. RESULTS: No statistical difference was found on pretreatment hard-tissue morphology between extraction and non-extraction groups divided from borderline cases. The SNB angle of the four first premolars extraction group was smaller than that of the four second premolars extraction group by (4.0+/-1.3) degrees P<0.01 . The statistical significant differences of the post-treatment hard-tissue cephalometry between extraction and nonextraction and between two different extraction patterns were found to be limited to the items related to the tooth position. CONCLUSION: Conventional cephalometric analysis cannot differentiate extraction or non-extraction treatment selection from borderline cases. The differences between extraction and non-extraction orthodontic treatments were limited to tooth positions but had no skeletal relation. Extraction of the four second premolars could prevent upper incisors from uprighting as it often follows the four first premolar extraction treatment. Extraction of the four first premolars could change the incisor position much more than extraction of the four second premolars. The changes of four second premolar extraction treatment were much similar to non-extraction treatment.

Cephalometry↗
PubMed2003

[Peroxisome proliferation-activated receptor-gamma ligands ameliorate autoimmune myocarditis associated with inhibition of T cell immunity].

OBJECTIVE: To investigate the role of peroxisome proliferator-activated receptor-gamma (PPAR gamma) on autoimmune myocarditis, and to test the hypothesis that PPAR-gamma ligands reduce experimental autoimmune myocarditis (EAM) associated with inhibition of the expansion and activation of self-sensitive T cells. METHODS: EAM was induced in Lewis rats by immunization with porcine cardiac myosin. Then the rats were divided into 3 groups of 9 rats: PPAR-gamma ligand 15-deoxy-(12,14)-PGJ(2) (15d-PGJ(2)) group (15d-PGJ(2) was injected intraperitoneally at the dosage of 200 microg.kg(-1).d(-1)), pioglitazone (PIO) group (PIO was mixed with the food and than fed at the dosage of 10 mg.kg(-1).d(-1)), and positive control group (phosphate-buffered saline was injected intraperitoneally). Nine normal rats were used as normal controls. Three weeks later, the rats underwent thoracotomy to undergo pathologic examination. The numbers of CD4(+) cells, CD8(+) cells, and macrophages were calculated by microscopy. Immunohistochemistry was used to examine the location and expression of PPAR gamma. Western blotting was used to examine the relative amount of PPAR gamma protein. The proliferative response and the cytotoxicity of T cell-enriched splenocytes and lymph node cells were determined. Another rats were killed 12 days after immunization. Their spleens and lymph nodes were taken out. T-cell rich splenocytes and cells from the lymph nodes were cultured. Cardiac myosin and 15d-PGJ(2) were added. [(3)H] thymine was added 72 hours after. ELISA was used to examine the interferon-gamma (IFN-gamma) in the supernatant. 15d-PGJ(2), PIO, or PBS were given to immunize the rats. The rats were killed 12 days after. The lymph nodes were taken out to make single cell suspension. (51)Cr was used to label the cells so as to calculate the %cytotoxicity. RESULTS: All immunized rats showed myocarditis. The numbers of CD4(+) cells, CD8(+) T cells, and macrophages, were 18 +/- 5, 7 +/- 2, and 45 +/- 8/six 0.25 mm x 0.25 mm squares. PPAR gamma was mainly located in the nuclear and perinuclear regions of infiltrating inflammatory cells, such as mononuclear cells and macrophage-like cells. The expression of PPAR gamma in the myocardium of EAM rats was 3.7 times higher than of the normal rats. The heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores of the 15d-PGJ group were significantly lower than those of the positive control group. The numbers of CD4(+) cells of the 15d-PGJ and PIO groups were 8 +/- 2 and 10 +/- 3, both significantly lower than that of the positive control group (both P < 0.01), the numbers of CD8(+) cells of the 15d-PGJ and PIO groups were 3 +/- 1 and 4 +/- 2 respectively, both significantly lower than that of the positive control group (P < 0.01 and P < 0.05), and the numbers of macrophages of the 15d-PGJ and PIO groups were 22 +/- 4 and 26 +/- 6 respectively, both significantly lower than that of the positive control group (both P < 0.01). The myocardiogenicity and the severity of myocarditis of the 15d-PGJ(2)- and PIO-groups were at lower degrees compared with those of the positive control group. The % cytotoxic activity was 10.2% +/- 2.6% in the 15d-PGJ(2) group and was 11.6% +/- 3.7% in the PIO group, both significantly lower than that of the positive control group (37.7% +/- 8.4%, both P < 0.01) Stimulated by cardiac myosin, the T-cell rich splenocytes and cells from lymph nodes showed obvious proliferation and production of IFN-gamma. The cardiac myosin-stimulated cell proliferation and production of IFN-gamma in the 15d-PGJ(2) and PIO groups were significantly reduced in comparison with those in the positive control group. CONCLUSION: PPAR-gamma ligands ameliorate EAM associated with inhibition of expansion and activation of the self-sensitive T cells.

Animals↗
PubMed2003

A methodological issue in the analysis of second-primary cancer incidence in long-term survivors of childhood cancers.

Survival of childhood cancer patients has increased remarkably in the last several decades due to therapeutic improvements. Associated with this progress is the emerging need to accurately assess/minimize late effects of cancer therapy in long-term survivors. This paper considers a methodological issue in assessing the risk of second-primary malignant neoplasms, a major late effect of concern, using second-primary female breast cancer as an example. In the assessment of second-primary malignant neoplasm risk, attained age is a critical factor that must be taken into account. Even with follow-up of decades, childhood-cancer survivors are still at relatively young ages for developing adult-onset diseases. Attained ages at follow-up, however, modify cancer risk considerably; for example, in the general population, women aged 40 years have about fivefold increased breast cancer risk compared with women aged 30 years. A failure to account for the natural age-associated increase of risk could alter, or even reverse, analytical conclusions. This problem was studied empirically by both descriptive and regression analyses of two major studies of long-term childhood-cancer survivors, the Childhood Cancer Survivor Study (1975-1999) and the Late Effects Study Group (1955-1994). These showed appreciable differences in the analytical results by not accounting for the natural age-associated increase of risk, illustrating a significant impact of this methodological issue on study conclusions.

Adolescent↗
PubMed2003

Versatile 3-channel high-voltage power supply for microchip capillary electrophoresis.

The fabrication of a battery operated 3-channel high voltage power supply for microchip capillary electrophoresis is described. The power supply consists of two positive and one negative DC-DC converters, a microprocessor controlled timer, a battery and a transformer to recharge the battery and feed the high voltage relays. This arrangement allows the possibility to control the potentials applied in the 0 to +/-4000 V range to a variety of microchip setups. It can also be easily adapted to perform either gated or pinched injection. The inclusion of a rechargeable battery was adopted to feed the DC-DC converters to reduce noise levels and achieve portability.

Journal Article↗
PubMed2003

A transforming growth factor-beta control element required for SM alpha-actin expression in vivo also partially mediates GKLF-dependent transcriptional repression.

We previously demonstrated that a conserved transforming growth factor-beta control element (TCE) within the 5'-region of the smooth muscle cell (SMC) differentiation marker gene SM alpha-actin could mediate both transcriptional activation and repression in cultured SMCs through interaction with members of the zinc finger Kruppel-like transcription factor (KLF) family. The aims of the present studies were to: 1) determine the role of the SM alpha-actin TCE in vivo through mutagenesis studies in transgenic mice and 2) further characterize the possible role and mechanisms by which the TCE-binding factor GKLF/KLF4 induces repression of SMC marker genes in various SMC model systems in vitro. Our results showed that the TCE was required for SM alpha-actin promoter activity in transgenic mice in vivo. Results of transient transfection studies showed that GKLF-induced repression of a SM alpha-actin promoter/luciferase reporter gene partially depended on the TCE. Furthermore, a GKLF overexpressing adenovirus inhibited whereas GKLF morpholino antisense oligos increased expression of endogenous SMC marker genes. Results of chromatin immunoprecipitation assays showed GKLF binding to TCE containing regions of various SMC marker gene promoters within intact chromatin. Finally, results of co-transfection studies showed that overexpression of IKLF/KLF5 reversed GKLF-dependent repression thus supporting a model of reciprocal activation-repression of SMC gene expression by different members of the KLF gene family.

Actins↗
PubMed2003

Peroxisome proliferation-activated receptor-gamma ligands ameliorate experimental autoimmune myocarditis.

BACKGROUND: Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands have been shown to ameliorate a variety of inflammatory conditions. The present study tested the hypothesis that PPAR-gamma ligands reduce experimental autoimmune myocarditis (EAM) associated with inhibition of the expansion and activation of T cells, as well as suppression of the expression of proinflammatory cytokines. METHODS AND RESULTS: EAM was induced in Lewis rats by immunization with porcine cardiac myosin. PPAR-gamma ligands, 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) 200 microg/kg/day i.p. and pioglitazone (PIO) 10 mg/kg/day orally, were administered for 3 weeks to rats with EAM. The results showed that enhanced PPAR-gamma expression was prominently stained in the nuclear and perinuclear regions of infiltrating inflammatory cells. Administration of PPAR-gamma ligands markedly reduced the severity of myocarditis, as shown by comparing the heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores. PPAR-gamma ligands suppressed myocardial mRNA expression of inflammatory cytokines and the expression of interleukin (IL)-1beta protein in rats with EAM. In addition, 15d-PGJ(2) and PIO treatment suppressed the proliferative response and interferon-gamma production of T cell-enriched splenocytes from rats with EAM. Furthermore, the cytotoxic activity and myocardiogenic potential of these T cells were inhibited by 15d-PGJ(2) treatment. CONCLUSIONS: PPAR-gamma may play a role in the pathophysiology of EAM. PPAR-gamma ligands ameliorate the EAM associated with suppression of the expansion and activation of myocardiogenic T cells, as well as inhibition of the expression of proinflammatory cytokines. These results suggest that PPAR-gamma ligands such as 15d-PGJ(2) and PIO may have the potential to modulate human inflammatory heart diseases such as myocarditis.

Animals↗
PubMed2003

Body mass index and risk of prostate cancer in U.S. health professionals.

The relationship between body mass index (BMI) and prostate cancer risk may be complex because obesity is associated with various hormonal factors and because the influence of BMI may differ according to whether the cancers are hereditary or sporadic. We used data from the Health Professionals Follow-Up Study, in which 2896 incident cases of prostate cancer were reported from February 1, 1986, through January 31, 2000, to determine prospectively whether BMI was associated with the risk of hereditary (men <60 years of age or with a positive family history of prostate cancer) and sporadic (men > or =60 years of age and without such a family history) prostate cancer. The risk of prostate cancer in men with a higher BMI (> or =30 kg/m2) was lower than that in men with a lower BMI (23-24.9 kg/m2) but only if they were younger (<60 years old) (relative risk = 0.52, 95% confidence interval = 0.33 to 0.83; P(trend)<.001) or had a family history of prostate cancer (relative risk = 0.74, 95% confidence interval = 0.45 to 1.19; P(trend) =.01). However, for groups with more sporadic cancers, BMI had a weak, non-statistically significant positive association with prostate cancer. We observed statistically significant interactions between BMI and age (P(interaction)<.001, two-sided Wald test) and between BMI and family history of prostate cancer (P(interaction) =.006, two-sided Wald test). Patterns for BMI and waist circumference were similar. Because obesity is associated with lower circulating concentrations of testosterone, our results suggest the hypothesis that androgens may play a more direct role for early-onset or hereditary prostate cancers than for sporadic prostate cancers.

Adult↗
PubMed2003

Troponin I binds polycystin-L and inhibits its calcium-induced channel activation.

Polycystin-L (PCL) is an isoform of polycystin-2, the product of the second gene associated with autosomal dominant polycystic kidney disease, and functions as a Ca(2+)-regulated nonselective cation channel. We recently demonstrated that polycystin-2 interacts with troponin I, an important regulatory component of the actin microfilament complex in striated muscle cells and an angiogenesis inhibitor. In this study, using the two-microelectrode voltage-clamp technique and Xenopus oocyte expression system, we showed that the calcium-induced PCL channel activation is substantially inhibited by the skeletal and cardiac troponin I (60% and 31% reduction, respectively). Reciprocal co-immunoprecipitation experiments demonstrated that PCL physically associates with the skeletal and cardiac troponin I isoforms in overexpressed Xenopus oocytes and mouse fibroblast NIH 3T3 cells. Furthermore, both native PCL and cardiac troponin I were present in human heart tissues where they indeed associate with each other. GST pull-down and microtiter binding assays showed that the C-terminus of PCL interacts with the troponin I proteins. The yeast two-hybrid assay further verified this interaction and defined the corresponding interacting domains of the PCL C-terminus and troponin I. Taken together, this study suggests that troponin I acts as a regulatory subunit of the PCL channel complex and provides the first direct evidence that PCL is associated with the actin cytoskeleton through troponin I.

3T3 Cells↗
PubMed2003

A critical role for nucleus accumbens dopamine in partner-preference formation in male prairie voles.

Although the role of nucleus accumbens (NAcc) dopamine (DA) in reward learning has been extensively studied, few investigations have addressed its involvement in learning socially relevant information. Here, we have examined the involvement of NAcc DA in social attachment of the "monogamous" prairie vole (Microtus orchrogaster). We first demonstrated that DA is necessary for the formation of social attachment in male prairie voles, because administration of haloperidol blocked, whereas apomorphine induced, partner-preference formation. We then provided the first descriptions of DA neuroanatomy and tissue content in vole NAcc, and mating appeared to induce a 33% increase in DA turnover. We also showed that administration of haloperidol directly into the NAcc blocked partner preferences induced by mating and apomorphine. In addition, administration of apomorphine into the NAcc but not the caudate putamen induced partner preferences in the absence of mating. Together, our data support the hypothesis that NAcc DA is critical for pair-bond formation in male prairie voles.

Animals↗
PubMed2003

Shear stress augments the enhanced adhesive phenotype of cells expressing the Pro33 isoform of integrin beta3.

Adhesion of platelets to the exposed extracellular matrix proteins at sites of vascular injury is partly regulated by the local fluid shear stress. Because the Leu33Pro (Pl(A)) polymorphism of integrin beta(3) confers only a modest increase in adhesion under static conditions, we used CHO and 293 cells expressing the Leu33 or Pro33 isoform of beta(3) in flow chamber experiments to test whether shear forces would alter the Pl(A) adhesive phenotype. We found that shear force augmented the Pro33-mediated enhanced adhesion to fibrinogen. This Pro33-dependent enhancement was aspirin-sensitive and was also observed on immobilized von Willebrand factor and cryoprecipitate, but not fibronectin. Thus, shear stress enhances the adhesive phenotype of the Pro33 cells to multiple physiologic substrates.

Animals↗
PubMed2003

[The Fc region of immunoglobulin suppresses atherosclerosis in apolipoprotein E knockout mice].

OBJECTIVE: To investigate the role of immunoglobulin in inhibition of atherosclerosis and its mechanism. METHODS: Apolipoprotein E knockout mice aged 6 weeks were fed with high fat diet containing 20% fat and 0.3% cholesterol for 8 approximately 16 weeks to induce the formation of fatty streak and fibrofatty plaque and were injected intraperitoneally with either human intact immunoglobulin (1 g x kg(-1) x d(-1)) or F(ab')(2) fragments of human immunoglobulin (1 g x kg(-1) x d(-1)) once the other day for 8 or 16 weeks. Sibling mice were injected intraperitoneally with human serum albumin (HSA) 1 g/kg once the other day as controls. 16 weeks later, the mice were killed. Their blood in right atrium was extracted to examine the total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG). The root of aorta and ascending aorta were isolated and made into tissue slices to be examined histochemically to calculate the areas of fatty streak and fibrofatty plaque. Immunohistological staining was conducted to examine the expression of macrophages CD(4)(+) T cells and CD(8)(+) T cell and infiltration of I-A(b+) cells in the specimens of aorta roots. IG or F(ab')(2) fragments and then lipopolysaccharide (LPS) was added into the culture media of cells of human monocyte/macrophage line U(937) carrying Fcgamma receptor surface marker: CD(16), CD(32), and CD(64) molecules. Flow cytometry was used to detect the expression of these Fcgamma receptor surface molecules. RESULTS: The area of fatty streak formation in the mice treated with IG was 4. 22.0%, significantly smaller than that in the control mice (13.6% +/- 4.8%, P < 0.01). However, the area of fatty streak formation in the mice treated with F(ab')(2) fragments was 12.1% +/- 3.7%, not significantly different from that of the controls. The area of fibrofatty plaque in the mice treated with IG was 8.1% +/- 2.7%, significantly smaller than that of the control (21.5% +/- 3.9%, P < 0.01). However, the area of fibrofatty plaque in the mice treated with F(ab')(2) fragments was 20.6% +/- 4.0%, not significantly smaller than that in the controls. Immunohistochemical analysis revealed that the percentage of M(Phi) positive cells in the fatty streak lesions was lower in the mice treated with IG than in the controls, however, the percentage of M(Phi) positive cells in the fatty streak lesions in the mice treated with F(ab')(2) fragments was not significantly different from that in the controls (P = ns vs HSA). There was no significant difference in the expression of CD(4)(+) T cells, CD(8)(+) T cells and the infiltration of I-A(b+) cells between the mice treated with IG or F(ab')(2) fragments and the controls. The serum TC, HDL-C, and TG were not significantly different among any groups. The mean fluorescence intensity (MIF) of CD(32) molecule in the surface of U(937) cells after cultured with IG and LPS was 108% +/- 18%, significantly lower than that in the surface of U(937) cells after cultured with only LPS (156% +/- 26%, n = 4, P < 0.05), however, the MIF of CD(32) molecule in the surface of U(937) cells after cultured with F(ab')(2) fragments was not significantly different from that in the surface of U(937) cells after cultured with only LPS. CONCLUSION: Immunoglobulin therapy remarkably suppressed atherosclerosis due to Fc receptor-mediated anti-inflammatory action. The suppression of the disease is associated with remarkably reduction of macrophage density in the lesions, but not with the reduction of high serum lipid levels.

Animals↗
PubMed2003

New insights into the mechanisms of vitamin D action.

The biologically active metabolite of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a secosteroid whose genomic mechanism of action is similar to that of other steroid hormones and is mediated by stereospecific interaction of 1,25(OH)(2)D(3) with the vitamin D receptor (VDR) which heterodimerizes with the retinoid X receptor (RXR). After interaction with the vitamin D response element (VDRE) in the promoter of target genes, transcription proceeds through the interaction of VDR with coactivators and with the transcription machinery. The identification of the steps involved in this process has been a major focus of recent research in the field. However, the functional significance of target proteins as well as the functional significance of proteins involved in the transport and metabolism of vitamin D is also of major importance. Within the past few years much new information has been obtained from studies using knockout and transgenic mice. New insight has been obtained using this technology related to the physiological significance of the vitamin D binding protein (DBP), used to transport vitamin D metabolites, as well as the physiological significance of target proteins including 25-hydroxyvitamin D(3) 24-hydroxylase (24(OH)ase), 25-hydroxyvitamin D(3)-1 alpha-hydroxylase (1 alpha-(OH)ase), VDR, and osteopontin. The crystal structure of the DBP and the ligand binding domain of the VDR have recently been reported, explaining, in part, the unique properties of these proteins. In addition novel 1,25(OH)(2)D(3) target genes have been identified including the epithelial calcium channel, present in the proximal intestine and in the distal nephron. Thus in recent years a number of exciting discoveries have been made that have enhanced our understanding of mechanisms involved in the pleiotropic actions of 1,25(OH)(2)D(3).

Animals↗
PubMed2003

At least at the level of inferior temporal cortex, the stereo correspondence problem is solved.

Stereoscopic vision requires the correspondence problem to be solved, i.e., discarding "false" matches between images of the two eyes, while keeping correct ones. To advance our understanding of the underlying neuronal mechanisms, we compared single neuron responses to correlated and anticorrelated random dot stereograms (RDSs). Inferior temporal neurons, which respond selectively to disparity-defined three-dimensional shapes, showed robust selectivity for correlated RDSs portraying concave or convex surfaces, but unlike neurons in areas V1, MT/V5, and MST, were not selective for anticorrelated RDSs. These results show that the correspondence problem is solved at least in far extrastriate cortex, as it is in the monkey's perception.

Animals↗
PubMed2003

Polycystin-2 associates with tropomyosin-1, an actin microfilament component.

Polycystin-2 (PC2) is the product of the second cloned gene (PKD2) responsible for autosomal dominant polycystic kidney disease and has recently been shown to be a calcium-permeable cation channel. PC2 has been shown to connect indirectly with the actin microfilament. Here, we report a direct association between PC2 and the actin microfilament. Using a yeast two-hybrid screen, we identified a specific interaction between the PC2 cytoplasmic C-terminal domain and tropomyosin-1 (TM-1), a component of the actin microfilament complex. Tropomyosins constitute a protein family of more than 20 isoforms arising mainly from alternative splicing and are present in muscle as well as non-muscle cells. We identified a new TM-1 splicing isoform in kidney and heart (TM-1a) that differs from TM-1 in the C terminus and interacted with PC2. In vitro biochemical methods, including GST pull-down, blot overlay and microtiter binding assays, confirmed the interaction between PC2 and the two TM-1 isoforms. Further experiments targeted the interacting domains to G821-R878 of PC2 and A152-E196, a common segment of TM-1 and TM-1a. Indirect double immunofluorescence experiments showed partial co-localization of PC2 and TM-1 in transfected mouse fibroblast NIH 3T3 cells. Co-immunoprecipitation (co-IP) studies using 3T3 cells and Xenopus oocytes co-expressing PC2 and TM-1 (or TM-1a) revealed in vivo association between the protein pairs. Furthermore, the in vivo interaction between the endogenous PC2 and TM-1 was demonstrated also by reciprocal co-IP using native human embryonic kidney cells and human adult kidney. Considering previous reports that TM-1 acts as a suppressor of neoplastic growth of transformed cells, it is possible that TM-1 contributes to cyst formation/growth when the anchorage of PC2 to the actin microfilament via TM-1 is altered.

3T3 Cells↗
PubMed2003

Monitoring the synthetic reaction of a polyamide/peptide conjugate using electrospray ionization mass spectrometry.

Recently, the chemical structures of a series of monoimidazole/polyamine conjugates were studied in this laboratory using electrospray ionization mass spectrometry (ESI-MS) combined with tandem mass spectrometry (ESI-MS/MS). The method was found to be a powerful tool for the identification of this class of compounds. During the synthesis of targeted polyamide/peptide conjugates as derivatives or analogues of netropsin and distamycin, the method was applied to analyze and track the coupling reaction for the formation of the polyamide, which was difficult to achieve using thin layer chromatography (TLC). Characteristic fragmentation pathways for a nitro-monoimidazole conjugate, an amino-monoimidazole conjugate, and the final product (a nitro-diimidazole conjugate) were explored. The fragmentations of these conjugates were strongly affected by the presence of an amino group instead of a nitro group in the molecule, and led to the identification of the three compounds in the reacting solution or in the final reaction mixture. Consequently, the reaction could be monitored successfully and the synthetic route optimized.

Models, Chemical↗