Biomedical subjects

Z Luo

Publications and source records attributed to Z Luo.

At least 91 records · Page 5Linked to original sources

PubMed1999

Early cell loss after angioplasty results in a disproportionate decrease in percutaneous gene transfer to the vessel wall.

Acute cell loss has been documented following angioplasty of normal rat and rabbit arteries. Here we analyzed the effects of balloon injury intensity on early cellular loss in single- and double-injury models and how it influences the efficiency of percutaneous gene delivery to the vessel wall. Rabbits underwent bilateral iliac angioplasties (n = 52) with 2.5-mm (balloon-to-artery [B/A] ratio, 1.08 to 1.13) and 3.0-mm (B/A ratio, 1.29 to 1.34) balloons. In the single-injury model, the 3.0-mm balloon induced a 61% reduction in medial cellularity at 3 days postinjury (p < 0.001) while the 2.5-mm balloon did not produce significant cell loss. In the double-injury model, the effects were more pronounced, with 35% (p < 0.01) and 91% (p < 0.001) reductions in medial cellularity at 3 days with the 2.5- and 3.0-mm balloons, respectively, but neointimal cellularity was decreased only with the 3.0-mm balloon (37% reduction, p = 0.025). Adenovirus-mediated beta-galactosidase gene delivery with a channel balloon (n = 24) revealed that larger balloon-to-artery ratios decreased both absolute levels and relative frequencies of transgene expression in the vessel wall. In the single-injury model, gene transfer efficiency was 4.2+/-1.1 and 1.3+/-0.25% (p < 0.05) for the small and large balloons, respectively. In the double-injury model, gene transfer efficiency was 6.6+/-1.6 and 2.3+/-0.8% (p < 0.05) in the neointima and 4.1+/-1.2 and 2.6+/-1.2% (p = NS) in the media for the small and large balloon, respectively. We conclude that early cell loss is dependent on the intensity of the injury in both single- and double-injury models of balloon angioplasty, with greater frequencies of cell loss occurring in the media than in the neointima. In both models, larger balloon-to-artery ratios result in disproportionate reductions in percutaneous adenovirus-mediated gene delivery.

Adenoviridae↗

PubMed1999

Adenovirus-mediated delivery of the Gax transcription factor to rat carotid arteries inhibits smooth muscle proliferation and induces apoptosis.

Adenovirus-mediated gene delivery in animal models of vascular injury has provided insights into the mechanisms underlying vessel wall pathologies. We have previously demonstrated that overexpression of the Gax transcription factor inhibits neointimal formation in rat and rabbit models of arterial injury. Here, we evaluate potential mechanisms for the reduction in stenotic lesion size due to Gax overexpression. At 3, 7 and 14 days after injury the Ad-Gax-infected arteries displayed a marked decrease in medial vascular smooth muscle cell number (3 days, 54% reduction P < 0.01; 7 days, 41% reduction P < 0.003; 14 days, 49% reduction P < 0.02). At 3 days after injury, PCNA expression was attenuated in the Ad-Gax-treated vessels compared with control vessels (65% reduction P < 0.02), indicating a reduction in cellular proliferation. At 7 days and 14 days after injury Ad-Gax-infected arteries exhibited elevated number of TUNEL-positive medial VSMCs compared with control-treated arteries (7 days, 9.2-fold increase P < 0.03; 14 days, 17.2-fold increase P < 0.03), indicating an induction of apoptotic cell death. These data suggest that deregulated Gax expression induces first cell cycle arrest and then apoptosis in the vascular smooth muscle cells that contribute to the neointimal layer. Therefore, the efficacy of this therapeutic strategy appears to result from the ability of the Gax transcriptional regulator to modulate multiple cellular responses.

Adenoviridae↗

PubMed1999

A neural network approach to the biopsy diagnosis of early acute renal transplant rejection.

AIMS: To develop and test a neural network to assist in the histological diagnosis of early acute renal allograft rejection. METHODS AND RESULTS: We used three sets of biopsies to train and test the network: 100 'routine' biopsies from Leicester; 21 selected difficult biopsies which had already been evaluated by most of the renal transplant pathologists in the UK, in a study of the Banff classification of allograft pathology and 25 cases which had been classified as 'borderline' according to the Banff classification in a review of transplant biopsies from Oxford. The correct diagnosis for each biopsy was defined by careful retrospective clinical review. Biopsies where this review did not provide a clear diagnosis were excluded. Each biopsy was graded for 12 histological features and the data was entered into a simple single layer perception network, designed using the MATLAB neural network toolbox. Results were compared with logistic regression using the same data, and with 'conventional' histological diagnosis. If the network was trained only with the 100 'routine' cases, its performance with either of the other sets was poor. However, if either of the 'difficult' sets was added to the training group, testing with the other 'difficult' group improved dramatically; 19 of the 21 'Banff' study cases were diagnosed correctly. This was achieved using observations made by a trainee pathologist. The result is better than was achieved by any of the many experienced pathologists who had previously seen these biopsies (maximum 18/21 correct), and is considerably better than that achieved by using logistic regression with the same data. CONCLUSION: A neural network can provide a considerable improvement in the diagnosis of early acute allograft rejection, though further development work will be needed before this becomes a routine diagnostic tool. The selection of cases used to train the network is crucial to the quality of its performance. There is scope to improve the system further by incorporating clinical information. Other related areas where this approach is likely to be of value are discussed.

Acute Disease↗

PubMed1999

Amino acid substitutions within the leucine zipper domain of the murine coronavirus spike protein cause defects in oligomerization and the ability to induce cell-to-cell fusion.

The murine coronavirus spike (S) protein contains a leucine zipper domain which is highly conserved among coronaviruses. To assess the role of this leucine zipper domain in S-induced cell-to-cell fusion, the six heptadic leucine and isoleucine residues were replaced with alanine by site-directed mutagenesis. The mutant S proteins were analyzed for cell-to-cell membrane fusion activity as well as for progress through the glycoprotein maturation process, including intracellular glycosylation, oligomerization, and cell surface expression. Single-alanine-substitution mutations had minimal, if any, effects on S-induced cell-to-cell fusion. Significant reduction in fusion activity was observed, however, when two of the four middle heptadic leucine or isoleucine residues were replaced with alanine. Double alanine substitutions that involved either of the two end heptadic leucine residues did not significantly affect fusion. All double-substitution mutant S proteins displayed levels of endoglycosidase H resistance and cell surface expression similar to those of the wild-type S. However, fusion-defective double-alanine-substitution mutants exhibited defects in S oligomerization. These results indicate that the leucine zipper domain plays a role in S-induced cell-to-cell fusion and that the ability of S to induce fusion may be dependent on the oligomeric structure of S.

Amino Acid Sequence↗

PubMed1999

Regulation of smooth muscle cell migration and integrin expression by the Gax transcription factor.

Homeobox transcription factors specify body plan by regulating differentiation, proliferation, and migration at a cellular level. The homeobox transcription factor Gax is expressed in quiescent vascular smooth muscle cells (VSMCs), and its expression is downregulated by vascular injury or other conditions that lead to VSMC proliferation. Previous investigations demonstrate that Gax may regulate VSMC proliferation by upregulating the cyclin-dependent kinase (cdk) inhibitor p21. Here we examined whether Gax influences VSMC migration, a key feature in the development of stenotic lesions after balloon injury. Transduction of a Gax cDNA inhibited the migratory response of VSMCs toward PDGF-BB, basic fibroblast growth factor, or hepatocyte growth factor/scatter factor. Gax expression also inhibited migration of NIH.3T3 fibroblasts and embryonic fibroblasts lacking p53. Gax was unable to inhibit the migration of fibroblasts lacking p21, but this effect could be restored in these cells by providing exogenous p21 or by overexpressing another cdk inhibitor, p16. Flow cytometric analysis implicated a Gax-mediated downregulation of alpha(v)beta(3) and alpha(v)beta(5) integrin expression in VSMCs as a potential cause for reduced cell motility. Gax specifically downregulated beta(3) and beta(5) in VSMCs in culture and after acute vascular injury in vivo. Repression of integrin expression was also found in NIH 3T3 cells and p53 knockout fibroblasts, but not in p21-knockout fibroblasts, unless these cells express exogenous p21 or p16. These data suggest that cycle progression, integrin expression, and cell migration can be regulated in VSMCs by the homeobox gene product Gax.

3T3 Cells↗

PubMed1999

Hyperglycemia inhibits insulin activation of Akt/protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle.

Sustained hyperglycemia impairs insulin-stimulated glucose utilization in the skeletal muscle of both humans and experimental animals--a phenomenon referred to clinically as glucose toxicity. To study how this occurs, a model was developed in which hyperglycemia produces insulin resistance in vitro. Rat extensor digitorum longus muscles were preincubated for 4 h in Krebs-Henseleit solution containing glucose or glucose + insulin at various concentrations, after which insulin action was studied. Preincubation with 25 mmol/l glucose + insulin (10 mU/ml) led to a 70% decrease in the ability of insulin (10 mU/ml) to stimulate glucose incorporation into glycogen and a 30% decrease in 2-deoxyglucose (2-DG) uptake, compared with muscles incubated with 0 mmol/l glucose. Glucose incorporation into lipid and its oxidation to CO2 were marginally diminished, if at all. The alterations of glycogen synthesis and 2-DG uptake were first evident after 1 h and were maximal after 2 h of preincubation; they were not observed in muscles preincubated with 25 mmol/l glucose + insulin for 5 min. Preincubation for 4 h with 25 mmol/l glucose in the absence of insulin produced a similar although somewhat smaller decrease in insulin-stimulated glycogen synthesis; however, it did not alter 2-DG uptake, glucose oxidation to CO2, or incorporation into lipids. Studies of insulin signaling in the latter muscles revealed that activation of Akt/protein kinase B (PKB) was diminished by 60%, compared with that of muscles preincubated in a glucose-free medium; whereas activation of phosphatidylinositol (PI) 3-kinase, an upstream regulator of Akt/PKB in the insulin-signaling cascade, and of mitogen-activated protein (MAP) kinase, a parallel signal, was unaffected. Immunoblots demonstrated that this was not due to a change in Akt/PKB abundance. The results indicate that hyperglycemia-induced insulin resistance can be studied in rat skeletal muscle in vitro. They suggest that impairment of insulin action in these muscles is related to inhibition of Akt/PKB by events that do not affect PI 3-kinase.

Animals↗

PubMed1999

An interleaved T1-T2* imaging sequence for assessing myocardial injury.

We developed a sequence by which T1- and T2*-weighted images can be acquired simultaneously and demonstrated its validity for assessing myocardial injury. The interleaved T1-T2* imaging sequence consisted of one preparatory pulse (a 90 degrees pulse) and a gradient-echo imaging sequence with a dynamically variable echo time varying between 4.2 msec for T1-weighted imaging and 15 msec for T2*-weighted imaging. The sequence was tested and validated on isolated blood-perfused pig hearts (n = 4). We found that contrast agent-induced T1 and T2* effects were clearly delineated during the first-pass and steady-state periods of a contrast agent (gadolinium diethylenetriaminopentaacetic acid). With a bolus injection of contrast agent, the maximum changes in T2* signal intensity occur significantly earlier than the changes in T1 signal. We also found that the maximum change in T1 signal intensity during the first pass of contrast agent was significantly greater in a reperfused-infarcted region than in normal regions. The suppression of T2* signal was similar in both regions. At steady state of contrast agent, T2* signal intensities gradually recovered to a significantly higher level in the reperfused-infarcted region than in normal regions. This suggests that the contrast agent diffused into the intracellular space, indicating the loss of cell membrane integrity. As a result, T1 signal intensity was also higher in the reperfused-infarcted myocardium than in normal myocardium. T1- and T2*-weighted images can be acquired simultaneously. The interleaved T1-T2* sequence is useful in assessing myocardial injury.

Animals↗

PubMed1999

[Enhancing effect of Chinese herbal medicine mixture on peripheral blood lymphocyte proliferation and interleukin-2 production in patients of burn].

OBJECTIVE: To study the regulatory effect of Chinese herbal medicine mixture (CHMM) on cell-mediated immune function in patients of burn. METHODS: Patients of burn were treated with CHMM and the therapeutic effect was evaluated by their peripheral blood T-lymphocyte (PBL) proliferation and interleukin-2 (IL-2) production determination. RESULTS: The PBL proliferation began to increase after 5 days of medication and the response was significant between the 10th to 20th day, which was in accordance with the change of IL-2 production. CONCLUSION: CHMM has immune regulatory effect on cell-mediated immune function in patients of burn.

Adjuvants, Immunologic↗

PubMed1999

[Combined use of rhBMP2/BCB and free periosteum in repairing segmental defects in radii of rabbits].

OBJECTIVE: To study the efficacy of combined use of rhBMP2/BCBand free periosteal graft in repairing segmental bony defects. METHODS: A new grafting material (rhBMP2/BCB) was made by combining recombinant human BMP2 (rhBMP2) and an antigen-free bovine cancellous bone (BCB) as a carrier. rhBMP2/BCB was used alone in conjunction with free periosteal graft to repair a 1.5 cm defect in the radius of the rabbit. The defect-repairing capability for each of the treatment modalities was assessed radiographically, biomechanically, and by densitometry and histological studies. RESULTS: rhBMP2/BCB used alone was capable of healing the defect in large by 16 weeks, with a similar repair process and mechanism seen with RBX. Combined use of rhBMP2/BCB and free periosteal graft was superior in terms of increased amount and quality of the new bone formed at the early stage of the repair process (within 12 weeks) to rhBMP2/BCB used in isolation, with the defect basically healed by 12 weeks. CONCLUSIONS: Both methods are effective in repairing segmental bony defects, with rhBMP2/BCB used in conjunction with free periosteal graft being most preferred, considering the satisfactory osteogenesis, osteoconduction and osteoinduction.

Animals↗

PubMed1999

[Changes of PMN apoptosis in rabbits after burn].

OBJECTIVES: To study the dynamic changes of apoptosis of PMN from rabbits in the early stage after severe burn in vivo and investigate the effect of burn serum and wound exudate on PMN apoptosis in vitro. METHODS: 12 rabbits were randomly divided into 2 groups: control group (37 degrees C) and burn group (95 degrees C, 15 sec, III degrees 30% TBSA). Whole blood from the burn group at 0, 4, 8, 12, 24 h postburn was stained with acridine orange/ethidium bromide (AO + EB), and observed under UV microscopy. PMNs were isolated from both groups and cultured for 24 h (37 degrees C, 5% CO(2)) with normal serum (NS), burn serum (BS), and subeschar tissue fluid (STF) respectively. Morphological assessment and quantitation of apoptosis were performed with AO + EB stain and flow cytometric analysis. RESULTS: The number of apoptotic PMN in vivo decreased in the early stage postburn. In the BS + PMN group and STF + PMN group, the percentage of apoptotic PMN reduced (vs NS + PMN group, P < 0.05) and the specific DNA "ladder" pattern for apoptotic cells was not detected by agarose gel electrophoresis. We observed that both burn serum and STF could similarly suppressed PMN apoptosis while there was no significant difference between NS + normal PMN group and NS + burn PMN group. CONCLUSIONS: Apoptosis is inhibited in PMN from rabbits postburn in the early stage. Both burn serum and STF from rabbits postburn can inhibit PMN apoptosis in vitro.

Animals↗

PubMed1999

[Modulation of endothelin-1 on pulmonary surfactant synthesis of cultured alveolar type II cells].

The effects of endothelin-1(ET-1) on pulmonary surfactant(PS) synthesis of cultured AT II cells were observed. The results showed that: 1. ET-1(10(-11)-10(-8) mol.L-1) enhanced PS synthesis of cultured AT II cells in a dose-dependent manner. 2. The minimum effective concentration of ET-1 enhanced PS synthesis of cultured AT II cells was higher than that of lung explants. 3. ETA antagonist BQ123 decreased the effect of ET-1 on PS synthesis, but ETB antagonist BQ788 did not change the effect. 4. ET-1 (10(-12) and 10(-10) mol.L-1) had no effect on the proliferation of AT II cells. These results confirmed that ET-1 can enhance directly and indirectly on the PS synthesis of AT II cells mediated via ETA receptor. The effect of ET-1 on PS synthesis was not induced by changing the number of AT II cells.

Animals↗

PubMed1999

[Affection of epidermal growth factor on VIP secretion and VIPR expression in airway epithelial cells].

In order to confirm the essential role of vasoactive intestinal peptide(VIP) on protection of local airway epithelium and investigate the modulation of the protective effect of VIP, secretion of VIP and expression of VIP receptor(VIPR) were studied in bronchial epithelial cells(BEC), and alveolar macrophages (AM). The radioimmunoassay was used for determining VIP secretion and the radio-ligand affinity analysis for VIPR expression. The effect of epidermal growth factor(EGF) was observed. The results showed that: 1. Both BEC and AM secreted VIP basically without remarkable stimulus, and some vesicles with electron-dense core which usually exist specifically in neuropeptide secreting cells were found in plasma of BEC; 2. In a dose-dependent manner, EGF promoted BEC to secrete VIP(r = 0.84, P < 0.05), and it was found that VIP secretion from AM was also elevated in EGF pretreated group(P < 0.05); 3. EGF exhibited a dose-dependent up-regulatory effect on the expression of VIPR in BEC(r = 0.95, P < 0.01). These results indicate that VIP may play an essential role in the protection at local airway by autocrine or paracrine, and the protective effect can be modulated by growth factors.

Animals↗

PubMed1999

[Detection of bcr/abl gene expression on bone marrow cell colonies in chronic myelogenous leukemia by reverse transcriptase-polymerase chain reaction].

The t(9;22) (q34;q11) between abl and bcr genes plays a pivotal role in the diagnosis and pathogenesis of chronic myelogenous leukemia(CML). To explore the bcr/abl fusion mRNA expression on hematopoietic precursors, reverse transcriptase-polymerase chain reaction(RT-PCR) was applied to detect bcr/abl mRNA expression on bone marrow cell colonies. Meanwhile, bcr/abl mRNA expressions on 14- or 28-day colonies using HPP-CFC and CFU-GM semisolid agar culture assay were also determined in 4 cases of confirmed Ph-positive CML by karyotyping analysis. The results showed that the bcr/abl mRNA expressions on 14-day colonies and some 14- or 28-day colonies detected singly were positive at presentation by RT-PCR, in agreement with results by karyotype analysis. Thus, a sensitive and powerful technique was offered for studying gene expression on hematopoietic precursors, diagnosis and therapeutic monitoring of CML. Furthermore, this can be used as an ideal method for revealing molecular mechanisms of pathogenesis of CML and screening anti-CML drugs.

Adult↗

PubMed1999

[Cloning of a new cDNA: responded to all-trans retinoic acid in HL-60 cell differentiation].

In this paper a new type of cDNA fragment named as W-1 gene was first cloned and sequenced from ATRA induced HL-60 cells by using differential display PCR (DD-PCR) and DNA sequencing techniques. These differentially expressing products of the gene responding to ATRA were further confirmed by Northern blotting analysis. The results showed that the expressing level of this gene induced by ATRA (10(-6) mol.L-1) for 16 hrs was much higher than that in the control HL-60 cells, but its expression in HL-60 was reduced to an unestimable level after induction of ATRA (10(-6) mol.L-1) for 24 hrs. It suggests that ATRA may increase the expression of W-1 gene during the early stage of HL-60 cell differentiation. The exact mechanism of action is being studied further.

Antineoplastic Agents↗

PubMed1999

[The design of a reflection sensor of NIRS tissue oximetry].

A design of the reflection light-electric Sensor suited to monitoring the statues of tissue blood oxygen on the surface of body is described. The designed sensors have been used too to detect blood oxygen statues of brain and muscle respectively, and many useful informations have been acquired Therefore The above-mentioned design is reasonalle and Feasikle.

Algorithms↗

PubMed1998

"Propylene spaced" allyl tin reagents: a new class of fluorous tin reagents for allylations under radical and metal-catalyzed conditions.

A new generation of propylene-spaced fluorous allyltin reagents [(Rf(CH2)3)3SnCH2CH = CH2] is described. These succeed in radical allylations where their lower homologs (ethylene-spaced) fail, and they provide improved performance in transition metal catalyzed allylations. The reagents and byproducts are readily separated by simple fluorous-organic liquid-liquid or solid-liquid extractions.

Aldehydes↗

PubMed1998

A dimeric 14-3-3 protein is an essential cofactor for Raf kinase activity.

cRaf-1 is a mitogen-activated protein kinase that is the main effector recruited by GTP-bound Ras in order to activate the MAP kinase pathway. Inactive Raf is found in the cytosol in a complex with Hsp90, Hsp50 (Cdc37) and the 14-3-3 proteins. GTP-bound Ras binds Raf and is necessary but not sufficient for the stable activation of Raf that occurs in response to serum, epidermal growth factor, platelet-derived growth factor or insulin. These agents cause a two- to threefold increase in overall phosphorylation of Raf on serine/threonine residues, and treatment of cRaf-1 with protein (serine/threonine) phosphatases can deactivate it, at least partially. The role of 14-3-3 proteins in the regulation of Raf's kinase activity is uncertain and is investigated here. Active Raf can be almost completely deactivated in vitro by displacement of 14-3-3 using synthetic phosphopeptides. Deactivation can be substantially reversed by addition of purified recombinant bacterial 14-3-3; however, Raf must have been previously activated in vivo to be reactivated by 14-3-3 in vitro. The ability of 14-3-3 to support Raf activity is dependent on phosphorylation of serine residues on Raf and on the integrity of the 14-3-3 dimer; mutant monomeric forms of 14-3-3, although able to bind Raf in vivo, do not enable Raf to be activated in vivo or restore Raf activity after displacement of 14-3-3 in vitro. The 14-3-3 protein is not required to induce dimerization of Raf. We propose that dimeric 14-3-3 is needed both to maintain Raf in an inactive state in the absence of GTP-bound Ras and to stabilize an active conformation of Raf produced during activation in vivo.

14-3-3 Proteins↗

PubMed1998

Roles in cell-to-cell fusion of two conserved hydrophobic regions in the murine coronavirus spike protein.

The spike (S) protein of coronavirus mouse hepatitis virus (MHV), mediates attachment and fusion during viral entry and cell-to-cell fusion later in infection. By analogy with other viral proteins that induce cell fusion the MHV S protein would be expected to have a hydrophobic stretch of amino acids that serves as a fusion peptide. Sequence analysis suggests that the S protein falls within the group of fusion proteins having internal rather than N-terminal fusion peptides. Based on the features of known viral fusion peptides, we identified two regions (PEP1 and PEP2) of MHV-A59 S2 as possible fusion peptides. Site-directed mutagenesis and an in viro cell-to-cell fusion assay were used to evaluate the roles of PEP1 and PEP2, as well as a third previously identified putative fusion domain (PEP3) in membrane fusion. Substitution of bulky hydrophobic residues with charged residues within PEP1 affects the fusion activity of the S protein without affecting processing and surface expression. Similar substitutions within PEP2 result in a fusion-negative phenotype; however, these mutant S proteins also exhibit defects in protein processing and surface expression which likely explain the loss of the ability to induce fusion. Thus PEP1 remains a candidate fusion peptide, while PEP2 may play a significant role in the overall structure or oligomerization of the S protein. PEP3 is an unlikely putative fusion peptide since it is not conserved among coronaviruses and nonconservative amino acid substitutions in PEP3 have minimal effects on cell-to-cell fusion.

Amino Acid Sequence↗