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Biomedical subjects

H Lu

Publications and source records attributed to H Lu.

At least 181 records · Page 10Linked to original sources
PubMed1999

Kringle 5 causes cell cycle arrest and apoptosis of endothelial cells.

Angiostatin which contains the first four kringle domains of plasminogen has been documented to be a potent inhibitor of angiogenesis. More recently, another kringle structure within plasminogen but outside angiostatin, known as kringle 5 (K5), was found to inhibit endothelial cell proliferation and migration. Here, we report the cloning and expression of mouse kringle 5 (rK5) in a bacterial expression system. The protein was purified to homogeneity using a Ni-NTA column. rK5 inhibited both proliferation and migration of endothelial cells with ED50's of 10 nM and < 500 nM, respectively. In addition, we show for the first time that rK5 causes cell cycle arrest and apoptosis, shedding further insight into rK5's mechanism of action. Finally, we show that these actions are endothelial cell specific.

Amino Acid Sequence↗
PubMed1999

Competitive inhibition of a glutamate carboxypeptidase by phosphonamidothionate derivatives of glutamic acid.

Several N-thiophosphonyl-glutamates were found to be potent competitive inhibitors of a zinc-dependent glutamyl hydrolase, carboxypeptidase G (CPG). Weak inhibition exhibited by an analogous N-phosphonyl-glutamate suggests that the enhanced potency of the phosphonamidothioates is due to the presence of their sulfur ligand and its favorable interactions with active site features, presumably zinc(II).

Carboxypeptidases↗
PubMed1999

Endostatin induces endothelial cell apoptosis.

Endostatin, a carboxyl-terminal fragment of collagen XVIII, has been shown to regress tumors in mice. In this study, we have analyzed the mechanism of endostatin action on endothelial cells and nonendothelial cells. Endostatin treatment of cow pulmonary artery endothelial cells caused apoptosis, as demonstrated by three methods, annexin V-fluorescein isothiocyanate staining, caspase 3, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling assay. Moreover, addition of endostatin led to a marked reduction of the Bcl-2 and Bcl-XL anti-apoptotic protein, whereas Bax protein levels were unaffected. These effects were not seen in several nonendothelial cells. Collectively, these findings provide important mechanistic insight into endostatin action.

Animals↗
PubMed1999

Traumatic instabilities of the cervical spine caused by high-speed axial compression in a human model. An in vitro biomechanical study.

STUDY DESIGN: Traumatic injury of the cervical spine was produced on human cadavers and evaluated with instability tests and radiographs. OBJECTIVE: To relate traumatic injuries of the cervical spine to instability and patterns of traumatic injury to different levels of impact energy. SUMMARY OF BACKGROUND DATA: Data from young human cadavers are rare in traumatic models of the cervical spine, and instabilities caused by axial compression with different impacts remain unknown. METHODS: Fourteen cervical spine specimens (C2-C4) obtained from fresh human cadavers were divided evenly into two groups and subjected to axial compressive impact with 30 J and 50 J impact energy, respectively. Pure moments in flexion-extension, left/right lateral bending, and left/right axial rotation were applied to each specimen before and after trauma. The maximum moment was 2.0 Nm in each case. Ranges of motion and neutral zones were measured using stereophotogrammetry. RESULTS: Ranges of motion and neutral zones for both groups increased after trauma. No bony injury was observed on the radiographs after trauma with 30 J, but motions increased significantly in flexion, extension, and axial rotation. All specimens showed bony injuries after trauma with 50 J, whereas motions continued to increase significantly in all directions. The relative neutral zone values were larger than the corresponding range of motion values, except in flexion-extension after trauma with 50 J. CONCLUSIONS: The injury patterns of the cervical spine were associated with impact energy, and a high level of impact energy could produce either three-column injury or anterior middle-column injury. Instabilities of the cervical spine caused by compressive trauma increased with the level of impact energy. The neutral zone was more sensitive than the range of motion in representing spinal instability, whereas instability testing was more sensitive than radiographs in evaluating traumatic injury of cervical spine.

Adult↗
PubMed1999

Antiangiogenic activity of restin, NC10 domain of human collagen XV: comparison to endostatin.

Based on a homology search with endostatin, the C-terminus 185 aa of collagen XVIII, we report the cloning, expression, and antiangiogenic activity of a 22 kDa human collagen XV fragment, that we have named restin. Restin was expressed in the prokaryotic pET expression system. We have shown that restin inhibits the migration of endothelial cells in vitro but has no effect on the proliferation of these cells. A polyclonal antibody raised against endostatin cross-reacted with restin. Systemic administration of restin suppressed the growth of tumors in a xenograft renal carcinoma model.

Amino Acid Sequence↗
PubMed1999

Forced unfolding of the fibronectin type III module reveals a tensile molecular recognition switch.

The 10th type III module of fibronectin possesses a beta-sandwich structure consisting of seven beta-strands (A-G) that are arranged in two antiparallel sheets. It mediates cell adhesion to surfaces via its integrin binding motif, Arg78, Gly79, and Asp80 (RGD), which is placed at the apex of the loop connecting beta-strands F and G. Steered molecular dynamics simulations in which tension is applied to the protein's terminal ends reveal that the beta-strand G is the first to break away from the module on forced unfolding whereas the remaining fold maintains its structural integrity. The separation of strand G from the remaining fold results in a gradual shortening of the distance between the apex of the RGD-containing loop and the module surface, which potentially reduces the loop's accessibility to surface-bound integrins. The shortening is followed by a straightening of the RGD-loop from a tight beta-turn into a linear conformation, which suggests a further decrease of affinity and selectivity to integrins. The RGD-loop therefore is located strategically to undergo strong conformational changes in the early stretching stages of the module and thus constitutes a mechanosensitive control of ligand recognition.

Amino Acid Sequence↗
PubMed1999

Carboxymethyl benzylamide dextran blocks angiogenesis of MDA-MB435 breast carcinoma xenografted in fat pad and its lung metastases in nude mice.

We previously showed that carboxymethyl benzylamide dextran (CMDB7) prevents tumor growth and tumor angiogenesis by binding to angiogenic growth factors, thereby preventing them from reaching their receptors on tumor or stromal cells (Bagheri-Yarmand et al. Br. J. Cancer, 78: 111-118, 1998; Bagheri-Yarmand et al. Cell Growth Differ., 9: 497-504, 1998). In this study, CMDB7 inhibited neovessel formation within the fibroblast growth factor 2-enriched matrigel in mice, and its anticancer effect was then tested in a metastatic breast cancer model. Human MDA-MB435 cells were injected into the mammary fat pad of nude mice, and breast tumors developed within 1 week; all of the mice had lung metastases at 12 weeks. CMDB7 treatment (50, 150, or 300 s.c. or 300 i.v. mg/kg/week for 10 weeks) reduced the incidence of lung metastases to 12%. Histological analysis showed markedly less tumor neovascularization in the CMDB7-treated mice. Pulmonary metastasis incidence was strongly dependent on the intratumoral neoangiogenesis in primary tumors.

Adipose Tissue↗
PubMed1999

Use of V79 cells with stably transfected cytochrome P450 cDNAs in studying the metabolism and effects of cytotoxic drugs.

PURPOSE: Studying the metabolism of cytotoxic drugs has become increasingly necessary to predict clinically significant drug-drug interactions and to understand the basis of interindividual variations in the pharmacokinetics of anticancer agents. The aim of this study was to determine the feasibility of using V79 Chinese hamster fibroblasts, which are stably transfected with cytochrome P450 (CYP) cDNAs, to study the metabolism of cytotoxic drugs in vitro. METHODS: The 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine cell survival after incubation with drugs. Gas chromatography/mass spectroscopy was used for the quantitation of metabolites of cyclophosphamide and ifosfamide in culture medium. The coculture technique was used to study the generation of cytotoxic metabolites in culture medium. RESULTS: After treatment with either cyclophosphamide or ifosfamide (100 microM to 1 mM) cytotoxicity was demonstrated in only cytochrome CYP2B1- and cytochrome CYP3A4-expressing cells. Treatment of parental nontransfected cells that were cocultured with CYP-expressing cells with cyclophosphamide resulted in increased sensitivity to this drug. All active and inactive metabolites of cyclophosphamide and ifosfamide were detected in the culture medium. Cyclophosphamide-induced cytotoxicity in CYP2B1- and CYP3A4-expressing cells was abrogated by metyrapone and midazolam/ troleandomycin, respectively. Paclitaxel showed greater cytotoxicity against parental V79 cells than against the CYP2BI-, 2E1-, or 3A4-expressing cells, which was also influenced by cotreatment with CYP inhibitors. CONCLUSIONS: Stable expression of CYP cDNAs by V79 cells provided an in vitro system to study cytotoxic drug metabolism. Cell viability and metabolite assays were used to determine the differential metabolism and effects in different CYP-transfected cell lines treated with cytotoxic drugs. The potential use of this V79 cell expression system is in studying enzymes involved in the metabolism of cytotoxic drugs, especially early in drug development. In addition, this system may be used to determine drug interactions that may influence the outcome of therapy in patients with cancer.

Animals↗
PubMed1999

Toxicity of ifosfamide and its metabolite chloroacetaldehyde in cultured renal tubule cells.

Renal injury is a common side effect of the chemotherapeutic agent ifosfamide. Current evidence suggests that the ifosfamide metabolite chloroacetaldehyde may contribute to this nephrotoxicity. The present study examined the effects of ifosfamide and chloroacetaldehyde on rabbit proximal renal tubule cells in primary culture. The ability of the uroprotectant medication sodium 2-mercaptoethanesulfonate (mesna) to prevent chloroacetaldehyde-induced renal cell injury was also assessed. Chloroacetaldehyde (12.5-150 microM) produced dose-dependent declines in neutral red dye uptake, ATP levels, glutathione content, and cell growth. Coadministration of mesna prevented chloroacetaldehyde toxicity while pretreatment of cells with the glutathione-depleting agent buthionine sulfoximine enhanced the toxicity of chloroacetaldehyde. Ifosfamide (1000-10,000 microM) toxicity was detected only at concentrations of 4000 microM or greater. Analysis of media collected from ifosfamide-treated cell cultures revealed the presence of several ifosfamide metabolites, demonstrating that renal proximal tubule cells are capable of biotransforming this chemotherapeutic agent. This primary renal cell culture system should prove useful in studying the cause and prevention of ifosfamide nephrotoxicity.

Acetaldehyde↗
PubMed1999

Leptin-induced increase in sympathetic nervous and cardiovascular tone is mediated by proopiomelanocortin (POMC) products.

The mechanism underlying the leptin-induced increased sympathetic nerve activity and cardiovascular tone was investigated in normal rats. The melanocortin (MC) peptides and other fragments derived from proopiomelancortin (POMC) have a diverse array of biological activities and have been implicated in mediating the feeding behavioral responses to leptin. In this study we evaluated the possible involvement of two major products of POMC, alpha-melanocyte stimulating hormone (alpha-MSH) and beta-endorphin, in mediating the effects of leptin on sympathetic activity and mean arterial pressure (MAP) in normal rats. Intraventricular (i.c.v.) cannulas were implanted in normal rats and allowed to recover. On the day of the study the animals were anesthetized with urethane alpha-chloralose and instrumented for the recording of MAP, lumbar sympathetic nerve activity (LSNA), and heart rate (HR). To determine the correlation between the leptin response and the POMC products, alpha-MSH and beta-endorphins were also injected into the lateral ventricle. alpha-MSH acted to increase MAP and LSNA while beta-endorphin decreased these parameters. Leptin administration by i.c.v. cannula increased the MAP and LSNA in normal rats. The i.c.v. administration of agouti protein, an alpha-MSH receptor antagonist, prior to leptin infusion blocked this response. Likewise, pretreatment with naloxone a beta-endorphin receptor antagonist also blocked the response to leptin. From these studies we conclude that the acute increased LSNA and MAP in response to i.c.v. leptin may be mediated by increased POMC and its subsequent production of breakdown product alpha-MSH and/or beta-endorphin and it is the subsequent action of alpha-MSH that increases MAP and LSNA by activation of the MC4 receptor. The naloxone antagonism of the leptin response is likely due to the blockade of presynaptic opioid inhibition of the MC4 receptor-mediated pressor response.

Animals↗
PubMed1999

Adaptation of solid phase extraction to an automated column switching method for online sample cleanup as the basis of a facile and sensitive high-performance liquid chromatographic assay for paclitaxel in human plasma.

An improved method for assaying paclitaxel in human plasma by high-performance liquid chromatography (HPLC) with UV detection at 227 nm has been developed by adapting previously reported sample preparation methods and chromatographic conditions to facilitate semi-automated sample cleanup using a column switching technique. Manual sample manipulations were limited to isolating the drug and internal standard from plasma (1.0 ml) by liquid-liquid extraction using tert-butyl methyl ether. The sample extract was initially loaded onto a short cartridge column containing a cyanopropyl stationary phase. During the predetermined time interval that the drug and internal standard eluted from the cartridge, 1.50-2.20 min, a fully automated 6-position switching valve was used to direct the effluent onto an octylsilica analytical column. The same mobile phase, composed of acetonitrile-methanol-ammonium acetate buffer (pH 5.0; 20 mM) (76:19:105, v/v/v) and delivered at flow rate of 1.0 ml/min, was used for both separations. The overall retention times of paclitaxel and the internal standard were 10.9 and 18.1 min, respectively. The analytical method was thoroughly validated for quantitating paclitaxel in plasma at concentrations ranging from 6 to 586 nM (5-500 ng/ml). The lowest concentration of paclitaxel measured with acceptable day-to-day accuracy (100.2%) and precision (RSD 11.7%, n = 21, 5 months) was 6 nM (5 ng/ml). The sensitivity and selectivity of the assay proved to be more than adequate for monitoring steady-state plasma concentrations of the drug when administered to cancer patients as a 96 h continuous intravenous infusion in combination with other anticancer agents, such as doxorubicin and topotecan. Moreover, the heart-cutting procedure prevented the problematic introduction of interfering nonpolar plasma components onto the analytical column, thereby enhancing sample throughput while decreasing the technical demands of the assay. The method was found to be extremely reproducible and robust during extended use for the routine analysis of plasma specimens acquired from several clinical trials.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Total knee arthroplasty in the presence of severe flexion contracture: a report of 37 cases.

From 1987 to 1994, 37 total knee arthroplasties were performed in 23 patients with severe, fixed flexion contractures averaging 78 degrees (range, 60 degrees -100 degrees). Fourteen of the knees had flexion contractures of greater than 90 degrees and 7 were fused at 90 degrees. There were 19 women and 4 men. The average age at surgery was 42 years (range, 20-57 years). The diagnoses were rheumatoid arthritis in 17 patients, juvenile rheumatoid arthritis in 3, and ankylosing spondylitis in 3. Preoperatively, all patients were Knee Society Category C, with 14 being nonambulatory and 9 minimally ambulatory. Follow-up averaged 4.3 years (range, 2-8 years). Postoperatively, patients were immobilized in extension when not in continuous passive motion or physical therapy. Flexion contractures were corrected to an average of 7 degrees postoperatively (range, 0 degrees -15 degrees). Arc of motion improved from 25 degrees preoperatively to 82 degrees postoperatively. The average Knee Society knee scores improved from 25 points preoperatively to 78 points postoperatively, and the functional scores improved from 0 points preoperatively to 71 points postoperatively. Five knees were manipulated under anesthesia postoperatively. Complications included 3 transient peroneal nerve palsies, 1 transient episode of vascular insufficiency, 6 delayed wound healings, and 1 deep infection. There were no aseptic loosenings. We conclude that although technically difficult, total knee arthroplasty can be performed successfully in this challenging and highly debilitated subset of patients, giving them marked improvement in quality of life.

Adult↗
PubMed1999

Managing a dropped nucleus during the phacoemulsification learning curve.

Three patients had a pars plana vitrectomy to remove retained nuclei within 72 hours after phacoemulsification performed by a surgeon making the transition from extra-capsular cataract extraction to phacoemulsification. After vitrectomy, the nuclei were brought to the midvitreous cavity from the retinal surface with a posterior segment phacofragmenter, emulsified, and completely removed. Then, a posterior chamber intraocular lens was implanted in the sulcus through the previous cataract surgery incision and remained well centered postoperatively. Postoperative complications included cystoid macular edema in 1 patient and choroidal detachment in another. No other complications were detected. Final visual acuity ranged from 20/60 to 20/30.

Aged↗
PubMed1999

Multiglycosidorum tripterygii, a new immunosuppressant, supresses coronary arteriosclerosis after heart transplantation.

BACKGROUND: Graft coronary arteriosclerosis is the major limiting factor for long-term survival after heart transplantation. In this study, we investigate the effect of multiglycosidorum tripterygii on graft coronary arteriosclerosis and platelet-derived growth factor A mRNA expression of transplanted hearts. METHODS: Three groups of Lewis rats (n = 7/Group) underwent heterotopic heart transplantation from Wistar-King donors and were treated with cyclosporine A (10 mg/ kg/day) for 60 days (Group A) or with multiglycosidorum tripterygii (30 mg/kg/day) for 60 days (Group B) or with cyclosporine A for the first 30 days and followed by multiglycosidorum tripterygii for another 30 days (Group C). Histological evaluations of rejection and coronary arteriosclerosis, as well as Northern blot analysis on graft platelet-derived growth factor A mRNA expression were made 60 days after transplantation. RESULTS: Morphometric results indicated no significant difference in rejection among three groups. However, the extent of graft coronary arteriosclerosis in Group B (1.12 +/- 0.21) and Group C (1.41 +/- 0.19) was significantly less than that seen in Group A (1.72 +/- 0.18) (p < 0.01 andp < 0.05, respectively). Furthermore, the incidence of diseased vessels was significantly less in Group B (29.5% +/- 7.8%) and Group C (42% +/- 9.1%) compared with Group A (69.1% +/- 11%) (p < 0.01 and p < 0.05, respectively). The expression of platelet-derived growth factor A mRNA of cardiac allograft was also significantly suppressed in Group B (25.4 +/- 6.2) and Group C (39.8 +/- 9.4), when compared with Group A (62.2 +/- 12.9) (p < 0.01 and p < 0.05, respectively). CONCLUSION: Multiglycosidorum tripterygii is superior to cyclosporine in prevention and attenuation of graft coronary arteriosclerosis and this efficacy is probably associated with the depressed expression of graft platelet-derived growth factor A mRNA in the multiglycosidorum tripterygii-treated groups.

Animals↗