Biomedical subjects

M Wu

Publications and source records attributed to M Wu.

At least 235 records · Page 13Linked to original sources

PubMed1998

RNA folding causes secondary structure rearrangement.

The secondary structure of the P5abc subdomain (a 56-nt RNA) of the Tetrahymena thermophila group I intron ribozyme has been determined by NMR. Its base pairing in aqueous solution in the absence of magnesium ions is significantly different from the RNA in a crystal but is consistent with thermodynamic predictions. On addition of magnesium ions, the RNA folds into a tertiary structure with greatly changed base pairing consistent with the crystal structure: three Watson-Crick base pairs, three G.U base pairs, and an extra-stable tetraloop are lost. The common assumption that RNA folds by first forming secondary structure and then forming tertiary interactions from the unpaired bases is not always correct.

Animals↗

PubMed1998

Genetic relationship of populations in China.

Despite the fact that the continuity of morphology of fossil specimens of modern humans found in China has repeatedly challenged the Out-of-Africa hypothesis, Chinese populations are underrepresented in genetic studies. Genetic profiles of 28 populations sampled in China supported the distinction between southern and northern populations, while the latter are biphyletic. Linguistic boundaries are often transgressed across language families studied, reflecting substantial gene flow between populations. Nevertheless, genetic evidence does not support an independent origin of Homo sapiens in China. The phylogeny also suggested that it is more likely that ancestors of the populations currently residing in East Asia entered from Southeast Asia.

Animals↗

PubMed1998

Lysophosphatidic acid as a potential biomarker for ovarian and other gynecologic cancers.

CONTEXT: Lysophosphatidic acid (LPA) has been shown to stimulate proliferation of ovarian cancer cells and is present in the ascitic fluid of patients with ovarian cancer. OBJECTIVES: To determine whether elevated levels of LPA are present in plasma from patients with ovarian cancer and other gynecologic malignancies compared with healthy controls and to evaluate whether an elevated LPA plasma level may be a biomarker for these diseases. DESIGN: A research assay was used to measure total LPA levels in plasma from healthy women and women with different diseases. All LPA assays and comparison of LPA levels and CA125 (an ovarian cancer biomarker) levels were performed by observers blinded to patient status or group. SETTING: The Cleveland Clinic Foundation. PARTICIPANTS: A convenience sample of 48 healthy control women, 48 women with ovarian cancer, 36 women with other gynecologic cancers, 17 women with benign gynecologic diseases, 11 women with breast cancer, and 5 women with leukemias. MAIN OUTCOME MEASURES: Total LPA levels in plasma samples from patients and controls. RESULTS: Patients in the ovarian cancer group had significantly higher plasma LPA levels (mean, 8.6 micromol/L; range, 1.0-43.1 micromol/L) compared with the healthy control group (mean, 0.6 micromol/L; range, <0.1-6.3 micromol/L) (P<.001). Elevated plasma LPA levels were detected in 9 of 10 patients with stage I ovarian cancer, 24 of 24 patients with stage II, III, and IV ovarian cancer, and 14 of 14 patients with recurrent ovarian cancer. Of 36 patients with other gynecologic cancers, 33 also showed higher LPA levels(mean, 14.9 micromol/L; range, <0.1-63.2 pmol/L), compared with healthy controls (P<.001). Elevated plasma LPA levels were detected in 5 of 48 controls and 4 of 17 patients with benign gynecologic diseases and in no women with breast cancer or leukemia. In comparison, among a subset of patients with ovarian cancer, 28 of 47 had elevated CA125 levels, including 2 of 9 patients with stage I disease. CONCLUSIONS: Plasma LPA levels may represent a potential biomarker for ovarian cancer and other gynecologic cancers. However, these findings are preliminary and require confirmation in larger studies.

Adult↗

PubMed1998

Conformational probes for elucidating the nature of substance P binding to the NK1 receptor: initial efforts to map the Phe7-Phe8 region.

Three substance P analogs with conformation constraints in the Phe7-Phe8 region have been prepared in connection with an effort to differentiate two families of potential conformations for the binding of substance P to its NK1 receptor. While the analogs did not bind the NK1 receptor with high affinity, the synthesis of the analogs demonstrated the utility of a general method for constructing piperazinone based peptidomimetics.

Amino Acid Sequence↗

PubMed1998

Determinants of recombinant production of antimicrobial cationic peptides and creation of peptide variants in bacteria.

Cationic peptides possessing antibacterial activity are virtually ubiquitous in nature, and offer exciting prospects as new therapeutic agents. We had previously demonstrated that such peptides could be produced by fusion protein technology in bacteria and several carrier proteins had been tested as fusion partners including glutathione-S-transferase, S. aureus protein A, IgG binding protein and P. aeruginosa outer membrane protein OprF. However these fusion partners, while successfully employed in peptide expression, were not optimized for high level production of cationic peptides (Piers, K., Brow, M. L., and Hancock, R. E. W. 1993, Gene 137, 7-13). In this paper we took advantage of a small replication protein RepA from E. coli and used its truncated version to construct fusion partners. The minimal elements required for high level expression of cationic peptide were defined as a DNA sequence encoding a fusion protein comprising, from the N-terminus, a 68 amino acid carrier region, an anionic prepro domain, a single methionine and the peptide of interest. The 68 amino acid carrier region was a block of three polypeptides consisting of a truncated RepA, a synthetic cellulose binding domain and a hexa histidine domain. The improved system showed high level expression and simplified downstream purification. The active peptide could be yielded by CNBr cleavage of the fusion protein. This novel vector was used to express three classes of cationic peptides including the alpha-helical peptide CEMA, the looped peptide bactenecin and the extended peptide indolicidin. In addition, mutagenesis of the peptide gene to produce peptide variants of CEMA and indolicidin using the improved vector system was shown to be successful.

Amino Acid Sequence↗

PubMed1998

Substrate specificity of human prolyl-4-hydroxylase.

Proline analogs (3-F, 3-Cl, 3-Br, 3,3-cyclopropyl, 3,3-methylene, 3-Me, and 4-Me) were synthesized, incorporated into CbzGlyPheXGlyOEt, and tested as substrate analogues/mechanistic probes for the human prolyl-4-hydroxylase catalyzed hydroxylation reaction. With the exception of the 3-fluoroproline containing peptide, none of these peptides were substrates for the enzyme.

Humans↗

PubMed1998

Roles of the tumor suppressor p53 and the cyclin-dependent kinase inhibitor p21WAF1/CIP1 in receptor-mediated apoptosis of WEHI 231 B lymphoma cells.

Treatment of WEHI 231 immature B lymphoma cells with an antibody against their surface immunoglobulin M (anti-IgM) induces apoptosis and has been studied extensively as a model of self-induced B cell tolerance. Since the tumor suppressor protein p53 has been implicated in apoptosis in a large number of cell types and has been found to be mutated in a variety of B cell tumors, here we sought to determine whether p53 and the p53 target gene cyclin-dependent kinase inhibitor p21(WAF1/CIP1) were involved in anti-IgM-induced cell death. Anti-IgM treatment of WEHI 231 cells increased expression of p53 and p21 protein levels. Ectopic expression of wild-type p53 in WEHI 231 cells induced both p21 expression and apoptosis. Ectopic expression of p21 similarly induced apoptosis. Rescue of WEHI 231 cells from apoptosis by costimulation with CD40 ligand ablated the increase in p21 expression. Lastly, a significant decrease in anti-IgM-mediated apoptosis was seen upon downregulation of endogenous p53 activity by expression of a dominant-negative p53 protein or upon microinjection of an antisense p21 expression vector or antibody. Taken together, the above data demonstrate important roles for p53 and p21 proteins in receptor-mediated apoptosis of WEHI 231 B cells.

Apoptosis↗

PubMed1998

[Molecular cytogenetic study on four human esophageal cancer cell lines].

OBJECTIVE: To investigate the possible involvement of chromosome abnormalities in pathogenesis of human esophageal cancer. METHODS: Four cell lines of human esophageal cancer (EC) established in our laboratory were analysed using interphase fluorescence in situ hybridization (FISH), chromosome painting technique and comparative genomic hybridization (CGH). RESULTS: Chromosome gain of 1,2,3,8,16, 17, and 20 was found in the four cell lines, and loss of chromosome Y in cell line EC8712, EC8733 and EC8501 was noted. Other frequent changes were partial deletion of 1p, translocation of 2q and amplification of 5p in all 4 cell lines, and amplification of 8q and 13q in EC8733 and deletion of 17p in EC8712. CONCLUSION: The data suggest that nonrandom chromosome aberrations may play an important role in the pathogenesis of human esophageal cancer.

Adult↗

PubMed1998

Developing online support for clinical information system developers: the FAQ approach.

OBJECTIVE: We investigate a knowledge-based help system for developers of an integrated clinical information system (CIS). The first objective in the study was to determine the system's ability to answer users' questions effectively. User performance and behavior were studied. The second objective was to evaluate the effect of using questions and answers to augment or replace traditional program documentation. DESIGN: A comparative study of user and system effectiveness using a collection of 47 veritable questions regarding the CIS, solicited from various CIS developers, is conducted. Most questions were concerning the clinical data model and acquiring the data. MEASUREMENTS: Answers using current documentation known by users were compared to answers found using the help system. Answers existing within traditional documentation were compared to answers existing within question-answer exchanges (Q-A's). RESULTS: The support system augmented 39% of users' answers to test questions. Though the Q-A's were less than 5% of the total documentation collected, these files contained answers to nearly 50% of the questions in the test group. The rest of the documentation contained about 75% of the answers. CONCLUSIONS: A knowledge-based help system built by collecting questions and answers can be a viable alternative to large documentation files, providing the questions and answers can be collected effectively.

Artificial Intelligence↗

PubMed1998

Treatment of hepatocellular carcinoma with the cellular tumor vaccines generated by in vitro modification of tumor cells with non gene transfer approaches.

Anti-tumor immune responses are mediated primarily by T cells. Down regulation of major histocompatibility complex (MHC) and the molecules that costimulate the immune responses is associated with defective signaling of tumor cells for T cell activation. In vitro fusion of autologous tumor cells with antigen presenting cells (APCs) or treatment of tumor cells with a combination of cytokines significantly increased the expression of MHC class I and adhesion molecules on tumor cell surfaces that costimulate host immune responses. The hybrid cells generated by fusion of tumor cells with APCs and the tumor cells treated in vitro with a combination of cytokines and pre-incubated with a bispecific monoclonal antibody (bi-Mab) cross-linking antigen on tumor cells to CD28 on T cells, become immunogenic and able to stimulate naive T cells with generation of tumor specific cytotoxic T cells both in vitro and in vivo. Immunization with the modified tumor cells elicits an immune response mediated by both CD4+ and CD8+ T cells. This response protected against a parental tumor cell challenge and cured established tumors. The approach was effective in both low immunogenic and non-immunogenic tumor systems. Modification of tumor cells with tumor:APC fusion or the two-step procedure may provide a strategy for development of tumor vaccines that is effective for cancer immunotherapy.

Animals↗

PubMed1998

Computer aided prediction and control of shrinkage porosity in titanium dental castings.

OBJECTIVES: The main objectives were to investigate the possibility and reliability of quantitative prediction and control of the concentrated shrinkage porosity (macroporosity) in titanium dental castings by means of a numerical simulation technique; and finally to optimize the filling and feeding system design for dental castings. METHODS: A commercial software, MAGMASOFT (Giessereitechnologie GmbH, Germany), was employed to simulate the mold filling and solidification process, and predict the shrinkage tendency in a sample dental casting, two simplified tooth crowns with a connector bar between them. The numerically predicted shrinkages were compared with the experimental results. The experiments were carried out on a centrifugal casting machine. The same geometric and processing parameters of the casting as in the simulations were strictly controlled. RESULTS: The computer predicted shrinkage porosity coincided with the performed experiments, demonstrating the reliability of the numerical model and the thermal physical data chosen for the calculations. Based on the above numerical model, several filling and feeding systems for the same casting were numerically simulated and compared. Finally an optimized design for this sample casting was proposed, and porosity-free castings were obtained. SIGNIFICANCE: It was expected that the numerical simulation technique could be further developed for dental laboratories to aid the real dental casting design.

Computer Simulation↗

PubMed1998

Clarithromycin significantly improves interleukin-12-mediated anti-Mycobacterium avium activity and abolishes toxicity in mice.

Treatment of experimental murine Mycobacterium avium (MAC) infection with interleukin-12 (IL-12) significantly decreased MAC organisms in tissue but resulted in toxicity. Because IL-12-related toxicity was seen only in infected mice, IL-12 was combined with clarithromycin in an attempt to decrease bacterial burden. Clarithromycin (200 mg/kg/day) was administered alone to M. avium-infected mice for 1 week, and from week 2, IL-12 (20 microg/kg twice per week) was added to the regimen for 4 weeks. Treatment with IL-12 resulted in 60% mortality, compared with 40% mortality in untreated control mice and 20% when IL-12 was given with clarithromycin (P < .05). Clarithromycin plus IL-12 resulted in increased activity compared with either clarithromycin or IL-12 alone in reducing the number of bacteria in spleen and blood. Although potentially toxic, IL-12 is an effective immunotherapy for MAC infection, and combination with clarithromycin reduces IL-12 toxicity.

Animals↗

PubMed1998

Characterization of provirus clones of simian foamy virus type 1.

We have cloned proviral DNA of simian foamy virus type 1 (SFV-1) from linear unintegrated DNA (pSFV-1). Transfection of pSFV-1 induces cytopathology in several cell lines with supernatants from the transfected cell culture containing infectious viral particles. Electron microscopy of the transfected cells revealed foamy virus particles. Deletion analysis of pSFV-1 indicated that the transcriptional transactivator (tas) gene located between env and the long terminal repeat is critical for virus replication, whereas the second open reading frame (ORF-2) in this region is dispensable. Although the tas and ORF-2 regions of foamy viruses have significantly diverged, the results presented here suggested that the gene products have similar functions. Recombinant pSFV-1 containing the cat gene was able to transduce the heterologous gene, indicating the utility of SFV-1 as a vector. An infectious clone of SFV-1 which is distantly related to the human foamy virus will provide a means to understand the biology of this unique group of viruses.

Animals↗

PubMed1998

cis-Acting sequences required for simian foamy virus type 1 vectors.

We have constructed a series of vectors based on simian foamy virus type 1 (SFV-1) to define the minimum cis-acting elements required for gene transfer. To characterize these vectors, we inserted the coding sequence of the bacterial lacZ gene linked to the cytomegalovirus immediate-early gene promoter. Introduction of a deletion mutation in the leader region between the 5' long terminal repeat and the start of the gag gene at position 1659 to 1694 completely abrogated gene transfer by the SFV-1 vector. Deletion of 39 nucleotides from position 1692 to 1731 in the leader region resulted in a significant reduction in the transducing-particle titer. Furthermore, we have identified a second cis-acting element located at the 3' end of the pol gene between position 6486 and 6975 to be critical for SFV-1 vector transduction. These results identify the two important cis-acting elements required for SFV-1 vector construction, and the finding of a cis-acting element in the pol gene is unique among retroviruses.

Animals↗

PubMed1998

Neutrophil-dependent augmentation of PAF-induced vasoconstriction and albumin flux in coronary arterioles.

Platelet-activating factor (PAF) has been implicated in the pathogenesis of ischemic heart disease, reperfusion injury, and inflammatory reactions. Although neutrophils have been shown to primarily mediate PAF-induced microvascular dysfunction, the vasoactive effect of PAF and its neutrophil-dependent mechanism have not been directly and systematically studied in coronary resistance vessels. Therefore, the aim of this study was to examine the effects of PAF on coronary arteriolar function and neutrophil dynamics using an isolated and perfused microvessel preparation. Topical application of PAF to the vessels induced a dose-dependent decrease in the diameter but an increase in the apparent permeability coefficient of albumin. Disruption of the endothelium abolished the vasomotor response to PAF, and perfusion of neutrophils significantly augmented PAF-induced changes in vasomotor tone and permeability. Furthermore, the interaction between neutrophils and the endothelium was studied in the intact perfused coronary arterioles. Under control conditions, there were no adherent neutrophils observed in the vessels at varied intraluminal flow velocities. However, administration of PAF caused neutrophil adhesion to the endothelium of coronary arterioles at low flow velocities. Western blot analysis indicated that PAF upregulated the expression of intercellular adhesion molecule-1 in cultured coronary microvascular endothelial cells. Taken together, the results suggest that 1) PAF induces vasoconstriction and hyperpermeability in coronary arterioles via an endothelium-dependent and neutrophil-mediated mechanism, and 2) PAF is able to stimulate neutrophil adhesion in coronary arterioles under a condition of low flow rate.

Animals↗

PubMed1998

GABAergic disinhibition affects responses of bat inferior collicular neurons to temporally patterned sound pulses.

Using the big brown bat, Eptesicus fuscus, as a model mammalian auditory system, we studied the effect of GABAergic disinhibition by bicuculline on the responses of inferior collicular (IC) neurons to temporally patterned trains of sound pulses delivered at different pulse repetition rates (PRRs) under free-field stimulation conditions. All 66 neurons isolated from eight bats either discharged one to two impulses (phasic on responders, n = 41, 62%), three to eight impulses (phasic bursters, n = 19, 29%), or many impulses throughout the entire duration of the stimulus (tonic responders, n = 6, 9%). Whereas 50 neurons responded vigorously to frequency-modulated (FM) pulses, 16 responded poorly or not at all to FM pulses. Bicuculline application increased the number of impulses of all 66 neurons in response to 4 ms pulses by 15-1,425%. The application also changed most phasic on responders into phasic bursters or tonic responders, resulting in 12 (18%) phasic on responders, 34 (52%) phasic bursters, and 20 (30%) tonic responders. Response latencies of these neurons were either shortened (n = 25, 38%) by 0.5-6.0 ms, lengthened (n = 9, 14%) by 0. 5-2.5 ms or not changed (n = 32, 48%) on bicuculline application. Each neuron had a highest response repetition rate beyond which the neuron failed to respond. Bicuculline application increased the highest response repetition rates of 62 (94%) neurons studied. The application also increased the highest 100% pulse-locking repetition rates of 21 (32%) neurons and facilitated 27 (41%) neurons in response to more pulses at the same PRR than predrug conditions. According to average rate-based modulation transfer functions (average rate MTFs), all 66 neurons had low-pass filtering characteristics both before and after bicuculline application. According to total discharge rate-based modulation transfer functions (total rate MTFs), filtering characteristics of these neurons can be described as band-pass (n = 52, 79%), low-pass (n = 12, 18%), or high-pass (n = 2, 3%) before bicuculline application. Bicuculline application changed the filtering characteristics of 14 (21%) neurons. According to synchronization coefficient-based modulation transfer functions, filtering characteristics of these neurons can be described as low-pass (n = 41, 62%), all-pass (n = 11, 17%), band-suppression (n = 7, 10.5%), and band-suppression-band-pass filters (n = 7, 10.5%). Bicuculline application changed filtering characteristics of 19 (29%) neurons.

Acoustic Stimulation↗

PubMed1998

Role of skeletal muscle in thiazolidinedione insulin sensitizer (PPARgamma agonist) action.

Thiazolidinedione (TZD) insulin sensitizers are specific agonists of peroxisome proliferator activated receptor (PPAR)gamma. However, their mechanism of action and the in vivo target tissue(s) that mediate insulin sensitization remain poorly defined. Although PPARgamma messenger RNA expression has been reported in skeletal muscle, the expression of PPARgamma within myocytes in intact muscle tissue has not been examined. An antipeptide PPARgamma antibody was generated; immunohistochemistry was then used to demonstrate that PPARgamma is present within nuclei of myocytes [in both skeletal (white and red fibers) and cardiac tissue (rodent and human)]. The effect of insulin sensitizer treatment on muscle insulin action was studied using ob/ob mice after 4 days dosing with a potent (6 nM PPARgamma Kd) TZD (10 mg/kg x day). 2-deoxyglucose (2-DOG) uptake was then assessed in freshly isolated soleus muscles from lean vs. ob/ob vs. TZD-treated ob/ob mice. In lean mouse muscles, 2-DOG uptake was stimulated by 82%, 95%, 165% (with 25, 100, 2000 microU/ml insulin); muscles from ob/ob were severely insulin resistant (<80% stimulation with 2000 microU/ml insulin). Muscles from TZD-treated ob/ob displayed a normal insulin response with 100 (71%) or 2000 (158%) microU/ml insulin. Additional studies were performed using ZDF rats treated with/without TZD for 7 days. In vivo 2-DOG glucose uptake into soleus, gastrocnemius, and diaphragm muscles was measured during euglycemic-hyperinsulinemic clamp. Compared with lean rats, muscle 2-DOG uptake in ZDF was reduced by 52% (soleus) or 71% (diaphragm). Partial (40-60%) normalization of the reduced 2-DOG uptake was evident in TZD-treated ZDF rats. In contrast to the effect of in vivo treatment on muscle insulin action, preincubation of isolated soleus muscles from naive lean or ob/ob mice for 5 h with 100 nM TZD did not affect insulin-stimulated 2-DOG uptake. We conclude: 1) PPARgamma is expressed in myocytes within skeletal and cardiac muscle. 2) In vivo activation of PPARgamma by treatment of insulin-resistant mice/rats with a potent TZD corrects impaired muscle insulin action. 3) The lack of a direct effect on muscle after 5 h in vitro TZD incubation suggests that changes in insulin action may require a longer duration of PPARgamma activation or that improved muscle insulin sensitivity may result from an indirect in vivo effect of PPARgamma activation (e.g. changes in systemic lipid metabolism).

Animals↗

PubMed1998

SDS agarose gels for analysis of proteins.

A new agarose-based protein electrophoresis gel system is described. The system consists of a highly resolving agarose, MetaPhor XR (FMC BioProducts, Rockland, ME, USA) dissolved in urea and TBE buffer and a stacking gel composed of a high gel-strength agarose, SeaKem Gold (FMC BioProducts). TBE containing sodium dodecyl sulfate (SDS) is used as electrophoresis buffer. The disadvantages of traditional agarose gels have been overcome, and several advantages over polyacrylamide gels have been demonstrated. The system is capable of high-resolution separation of small proteins and has a dynamic separation range equivalent to a 4%-20% gradient polyacrylamide gel. Furthermore, the staining of protein bands by Coomassie Brilliant Blue is very uniform in this gel, and depending on the protein, higher detection sensitivity can be obtained compared to SDS polyacrylamide gels. In Western blotting, proteins are more efficiently transferred to the membrane from the agarose gel than from polyacrylamide gels. Finally, the exceptional stability of agarose allows for gels to be precast and stored for a year.

Blotting, Western↗