Biomedical subjects

Y Li

Publications and source records attributed to Y Li.

At least 235 records · Page 13Linked to original sources

PubMed2004

Efficacy of mycophenolate mofetil versus azathioprine after renal transplantation: a systematic review.

INTRODUCTION: Our objective was to evaluate the efficacy of mycophenolate acid (MMF) versus azathioprine (AZA) after renal transplantation. MATERIALS AND METHODS: The following electronic databases were searched: Medline, Embase, Cochrane library, and Chinese Biomedicine database (CBM). Randomized controlled trials (RCTs) were subjected to Revman 4.11 for statistical analyses. RESULTS: Twenty-three RCTs were identified to compare MMF and AZA for antirejection, prophylaxis after renal transplantation. The data showed that MMF (2 g/d) was more beneficial than AZA to improve graft and long-term patient survivals, but there was no statistical differences between MMF (3 g/d) and AZA. Whether at 6 months or at 1 year after renal transplantation, the use of MMF (2 g/d) or MMF (3 g/d) markedly reduced the incidence of biopsy-proven rejection. CONCLUSION: Compared with AZA, MMF is a more potent immunosuppressive drug, that is more efficient in reducing the incidence of acute rejection episodes after renal transplantation. MMF can improve the graft and patient survival rate. The 2 g per day dosage is more acceptable.

Azathioprine↗

PubMed2004

Study of renal function matching between Banna Minipig Inbred line and human.

Pigs have been thought to be ideal candidates for xenotransplant donors. However besides the immunological barrier, physiological and pharmacokinetic comparabilities of kidney function between donor animals and humans are important factors for successful xenotransplantation. As a unique large inbred animal, Banna Minipig Inbred (BMI) has been reported to be a potential large animal suitable for xenotransplantation. However, its physical and pharmacokinetic compatibilities with humans have not been documented. The purpose of this investigation was to measure renal routine function, glomerular filtration rate (GFR), renal blood flow (ERPF), and drug metabolism to evaluate comparability to humans. The results suggested that the renal function of BMI was similar to that of humans to eliminate nonprotein nitrogenous end products of metabolism. Pharmacokinetics of p-aminohippurate (PAH) and inulin--the most widely used methods to assess ERPF and GFR--showed that BMI showed lower values than humans for GFR, but similar function to humans in ERPF. The pharmacokinetics of cefazolin; a widely used model drug to study kidney drug metabolizing capacity, showed greater overall renal drug elimination of BMI than of humans. These results suggested that BMI did show comparable data to human renal function.

Adult↗

PubMed2004

Activation of human coagulation system by liver-derived clotting factors of Banna minipig inbred line.

The liver synthesizes most of the coagulation factors that play a major role in arresting hemorrhage. Matching hepatic coagulation factors is an important premise in successful xenotransplantation. As a unique inbred pig, the Banna minipig inbred (BMI) animals have a huge potential value for pig-to-human xenotransplantation, due to its clear genetic background and tiny interindividual differences. Whether the coagulation factors synthesized by porcine liver can trigger human clotting pathways has not been reported. This study focused on the activities of BMI coagulant factors synthesized exclusively by the liver to activate human clotting pathways. In these experiments we prepared coagulant factors II, V, VII, X, and XII synthesized exclusively by liver from BMI and humans. The factors were used in common correction tests, added to the corresponding factor-deficient human plasma to determine prothrombin times or activated partial thromboplastin time, thereby calculating BMI and human coagulant factor activities. BMI clotting factors XII, VII, and X triggered human intrinsic, extrinsic, and common pathways, respectively. BMI clotting factors II, V, VII, X, and XII activities were 3.2-, 3.7-, 4.7-, 2.9-, and 4.5-fold as potent as those from humans.

Adult↗

PubMed2004

Study of hepatic function matching between Banna minipig inbred and humans.

As a unique inbred pig Banna minipig inbred (BMI) is potentially suitable for pig-to-human xenotransplantation due to its clear genetic background and minor interindividual differences. Previous studies of BMI have focused on immunological barriers between BMI and humans. However, a comparison of liver function between donor animals and humans is an essential premise for successful xenotransplantation. In this study, we investigated routine hepatic functions, protein electrophoresis, and drug metabolism to compare capacity of liver synthesis, metabolism, and drainage between BMI and humans. The results showed no significant differences in the concentrations of albumin and globulin synthesized in the liver (alpha1, alpha2, and beta-globulin). Serum enzyme activities in BMI were higher than those in humans, and levels of total bilirubin and direct-reacting bilirubin of BMI were lower than those of humans. In BMI, the clearance of antipyrine, a widely used model drug to study hepatic drug metabolism, was 16 times greater than that by humans, with a mean residual time of antipyrine in BMI, one-tenth of that in human. These findings suggested that BMI livers are similar to humans in albumin and alpha, beta-globulin synthesis, but stronger in bilirubin elimination, enzyme activity, and drug metabolism. BMI livers may have stronger functions compared with those of humans. No incompatibility was identified in hepatic function between BMI and humans.

Adult↗

PubMed2004

Lack of infection of vertebrate cells by the densovirus from the maize worm Mythimna loreyi (MlDNV).

Several densoviruses have been used successfully in biological control of pests in the tropics. The densovirus from Mythimna loreyi (MlDNV) could also be an important tool in biological control of important pests. However, safety concerns remain as previous reports suggested that densoviruses may infect and transform L cells (from mouse). In this study, we show using molecular-biology tools that neither L nor other vertebrate cells support replication or transcription of densovirus, either after infection or after transfection. Quantitative PCR indicated no increase of viral DNA due to replication in vertebrate cells, in contrast to that in insect LD652 cells. After transfection, both the NS and VP mRNAs could be detected in LD652 cells but not in L cells. Moreover, the viral genome was excised from the plasmid after transfection of the infectious clone in LD652 cells, indicative of viral NS protein production, in contrast to L cells. The viral genome was able to integrate in the host chromosome of L cells after transfection, but not after infection. However, no viral transcription could be detected after integration.

Animals↗

PubMed2004

CNS gene transfer mediated by a novel controlled release system based on DNA complexes of degradable polycation PPE-EA: a comparison with polyethylenimine/DNA complexes.

Nonviral gene delivery systems based upon polycation/plasmid DNA complexes are quickly gaining recognition as an alternative to viral gene vectors for their potential in avoiding immunogenicity and toxicity problems inherent in viral systems. We investigated in this study the feasibility of using a controlled release system based on DNA complexed with a recently developed polymeric gene carrier, polyaminoethyl propylene phosphate (PPE-EA), to achieve gene transfer in the brain. A unique feature of this gene delivery system is the biodegradability of PPE-EA, which can provide a sustained release of DNA at different rates depending on the charge ratio of the polymer to DNA. PPE-EA/DNA complexes, naked DNA, and DNA complexed with polyethylenimine (PEI), a nondegradable cationic polymer known to be an effective gene carrier, were injected intracisternally into the mouse cerebrospinal fluid. Transgene expression mediated by naked DNA was mainly detected in the brain stem, a region close to the injection site. With either PPE-EA or PEI as a carrier, higher levels of gene expression could be detected in the cerebral cortex, basal ganglia, and diencephalons. Transgene expression in the brain mediated by PPE-EA/DNA complexes at an N/P ratio of 2 persisted for at least 4 weeks, with a significant higher level than that produced by either naked plasmid DNA or PEI/DNA at the 4-week time point. Furthermore, PPE-EA displayed much lower toxicity in cultured neural cells as compared to PEI and did not cause detectable pathological changes in the central nervous system (CNS). The results established the potential of PPE-EA as a new and biocompatible gene carrier to achieve sustained gene expression in the CNS.

Animals↗

PubMed2004

IL-18 gene therapy develops Th1-type immune responses in Leishmania major-infected BALB/c mice: is the effect mediated by the CpG signaling TLR9?

IL-18 regulates either Th1 or Th2 responses depending on the cytokine microenvironment. Administration of recombinant IL-18 (rIL-18) alone does not promote Th1 response, but rather induces Th2 response and exacerbates Leishmania major infection in susceptible BALB/c mice. Here, we treated BALB/c mice with an IL-18-expressing plasmid by using a gene gun weekly after L. major infection. This gene therapy resulted in improved pathogenic process and preferential induction of Th1 responses by inducing the expression of IL-12 p40, but treatment with rIL-18 did not. Notably, simultaneous administration of rIL-18 with an empty plasmid vector rendered BALB/c mice resistant to the infection, despite the fact that treatment with either rIL-18 alone or the plasmid vector alone did not influence the susceptibility. The synergistic role of the vector with rIL-18 was found to depend on CpG motifs, which enhanced expression of proinflammatory cytokines, especially IL-12, from APCs through Toll-like receptor (TLR) 9 ligation. Treatment with methylated plasmid vector in which CpG was disrupted could no longer prevent the disease development in coadministration with rIL-18. Taken together, IL-18 gene therapy was shown to develop Th1-type protective immunity in L. major-infected BALB/c mice without the requirement of exogenous IL-12, probably via CpG-TLR9 signaling pathway.

Animals↗

PubMed2004

Regulation of transgene expression in muscles by ultrasound-mediated hyperthermia.

Heat-sensitive transgene expression systems have been proposed recently for use in gene therapy to enable both spatial and temporal control of the gene activity. The transgene was put under the control of HSP-related promoters and could be turned on by external heat treatment. While the 'heat activation' phenomenon of the HSP-related promoters in vitro had been well documented, the detailed time response and temporal regulation profile in vivo were not fully understood. We reported here the regulation of transgene luciferase expression in vivo in muscles using a custom-built ultrasound-mediated hyperthermia instrument. The effects of different heating parameters and treatment regimens were evaluated. Optimal activation of gene expression was found at 39 degrees C. Significant tissue damage was observed at 41 degrees C and above, which directly correlated with the greatly reduced gene expression. The gene constructs remained stable and silent in muscle cells, and could be turned on at a later time without losing much activity. Repeated activation was also possible, but required heat treatment at a higher temperature to overcome thermotolerance.

Animals↗

PubMed2004

Improved transduction of primary murine hepatocytes by recombinant adeno-associated virus 2 vectors in vivo.

Adeno-associated virus 2 (AAV) vectors are currently in use in Phase I/II clinical trials for gene therapy of cystic fibrosis and hemophilia B. Although 100% of murine hepatocytes can be targeted by AAV vectors, the transgene expression is limited to approximately 5% of hepatocytes. Since the viral genome is a single-stranded DNA, and single strands of both polarities are encapsidated with equal frequency, it has been suggested that failure to undergo DNA strand-annealing accounts for the lack of efficient transgene expression. We and others, on the other hand, have proposed that failure to undergo viral second-strand DNA synthesis attributes to the observed low efficiency of transgene expression. We have previously documented that a cellular protein, designated FKBP52, when present in phosphorylated forms, inhibits the viral second-strand DNA synthesis, and consequently, limits transgene expression in nonhepatic cells, whereas unphosphorylated forms of FKBP52 have no effect. To further evaluate whether phosphorylated FKBP52 is also involved in regulating AAV-mediated transgene expression in murine hepatocytes, we generated transgenic mice overexpressing the cellular T-cell protein tyrosine phosphatase (TC-PTP) protein, known to catalyze dephosphorylation of FKBP52, as well as mice deficient in FKBP52. We demonstrate here that dephosphorylation of FKBP52 in TC-PTP transgenic (TC-PTP-TG) mice, and removal of FKBP52 in FKBP52-knockout (FKBP52-KO) mice results in efficient transduction of murine hepatocytes following tail-vein injection of recombinant AAV vectors. We also document efficient viral second-strand DNA synthesis in hepatocytes from both TC-PTP-TG and FKBP52-KO mice. Thus, our data strongly support the contention that the viral second-strand DNA synthesis, rather than DNA strand-annealing, is the rate-limiting step in the efficient transduction of hepatocytes, which should have implications in the optimal use of recombinant AAV vectors in human gene therapy.

Animals↗

PubMed2004

Characterization of the distinct orthotopic bone-forming activity of 14 BMPs using recombinant adenovirus-mediated gene delivery.

Efficacious bone regeneration could revolutionize the clinical management of bone and musculoskeletal disorders. Although several bone morphogenetic proteins (BMPs) (mostly BMP-2 and BMP-7) have been shown to induce bone formation, it is unclear whether the currently used BMPs represent the most osteogenic ones. Until recently, comprehensive analysis of osteogenic activity of all BMPs has been hampered by the fact that recombinant proteins are either not biologically active or not available for all BMPs. In this study, we used recombinant adenoviruses expressing the 14 types of BMPs (AdBMPs), and demonstrated that, in addition to currently used BMP-2 and BMP-7, BMP-6 and BMP-9 effectively induced orthotopic ossification when either AdBMP-transduced osteoblast progenitors or the viral vectors were injected into the quadriceps of athymic mice. Radiographic and histological evaluation demonstrated that BMP-6 and BMP-9 induced the most robust and mature ossification at multiple time points. BMP-3, a negative regulator of bone formation, was shown to effectively inhibit orthotopic ossification induced by BMP-2, BMP-6, and BMP-7. However, BMP-3 exerted no inhibitory effect on BMP-9-induced bone formation, suggesting that BMP-9 may transduce osteogenic signaling differently. Our findings suggest that BMP-6 and BMP-9 may represent more effective osteogenic factors for bone regeneration.

Adenoviridae↗

PubMed2004

Retroviral delivery of GAD-IgG fusion construct induces tolerance and modulates diabetes: a role for CD4+ regulatory T cells and TGF-beta?

Previous studies have demonstrated that antigen-specific tolerance could be induced by lipopolysaccharide (LPS)-stimulated B cells retrovirally transduced with an immunoglobulin-antigen (or epitope-containing peptide) fusion construct. To investigate the mechanism of this gene therapy system, we now adapted this approach to immunotherapy of spontaneous diabetes in nonobese diabetic (NOD) mice, a T-cell-mediated autoimmune disease triggered, in part, by a pathogenic response to glutamate decarboxylase (GAD) 65. We demonstrate that LPS-stimulated splenocytes, retrovirally transfected with GAD-IgG fusion construct, induce a significant antigen-specific hyporesponsiveness at both cellular and humoral levels and reduce the incidence of diabetes in female NOD mice. Parallel with disease protection, we observed a prolonged increase of the numbers of CD4+CD25+ T cells in the periphery of GAD-IgG-treated mice, compared to those treated with a control IgG vector, both in the prediabetic period and persisting even 8 months after gene therapy. This increase appeared to be induced by the repeated stimulation of the antigen in the periphery instead of a result of differentiation of T-cell precursor in the thymus. Moreover, CD4+CD25+ T cells induced by GAD-IgG fusion construct were capable of suppressing the proliferative response of CD4+CD25- T cells in vitro; and ablation of the activity of CD4+CD25+ T cells by blocking antibody against CD25 could reverse GAD-specific T-cell hyporesponsiveness. These results suggested that CD4+CD25+ T-cell subset induced in GAD-IgG-treated NOD mice represented the regulatory or suppressive CD4+CD25+ T cells (Treg) and might play an important role in the induction and maintenance of tolerance in NOD mice. Furthermore, the numbers of splenic CD4+CD62L+ regulatory T cells in GAD-IgG-treated mice during the prediabetic period and serum TGF-beta levels in 34-38-week-old GAD-IgG-protected mice were also increased, compared to control IgG-treated ones. Therefore, we propose that the induction of tolerance and the prevention of diabetes incidence in NOD female mice induced by the GAD-IgG fusion construct may require CD4+ regulatory T cells, and the possible mediation of TGF-beta.

Animals↗

PubMed2004

Experimental and CFD evidence of multiple solutions in a naturally ventilated building.

This paper considers the existence of multiple solutions to natural ventilation of a simple one-zone building, driven by combined thermal and opposing wind forces. The present analysis is an extension of an earlier analytical study of natural ventilation in a fully mixed building, and includes the effect of thermal stratification. Both computational and experimental investigations were carried out in parallel with an analytical investigation. When flow is dominated by thermal buoyancy, it was found experimentally that there is thermal stratification. When the flow is wind-dominated, the room is fully mixed. Results from all three methods have shown that the hysteresis phenomena exist. Under certain conditions, two different stable steady-state solutions are found to exist by all three methods for the same set of parameters. As shown by both the computational fluid dynamics (CFD) and experimental results, one of the solutions can shift to another when there is a sufficient perturbation. These results have probably provided the strongest evidence so far for the conclusion that multiple states exist in natural ventilation of simple buildings. Different initial conditions in the CFD simulations led to different solutions, suggesting that caution must be taken when adopting the commonly used 'zero initialization'.

Air Movements↗

PubMed2004

Tunable optical properties of colloidal quantum dots in electrolytic environments.

The absorption spectra of colloidal cadmium sulfide quantum dots in electrolytic solutions are found to manifest a shift in the absorption threshold as the concentration of the electrolyte is varied. These results are consistent with a shift in the absorption threshold that would be caused by electrolytic screening of the field caused by the intrinsic spontaneous polarisation of these würtzite structured quantum dots. These electrolyte-dependent absorption properties provide a potential means of gaining insights on the variable extracellular and intracellular electrolytic concentrations that are present in biological systems.

Journal Article↗

PubMed2004

Chemotherapy- and radiotherapy-induced intestinal damage is regulated by intestinal trefoil factor.

BACKGROUND & AIMS: Injury to the intestinal mucosa is frequently a dose-limiting complication of radiotherapy and chemotherapy. Approaches to limit the damage to the intestine during radiation and chemotherapy have been largely ineffective. Trefoil factors are produced throughout the gastrointestinal tract and regulate cell migration, restitution, and repair. Studies were undertaken to define the role of intestinal trefoil factor in modulating the intestinal response to chemotherapy and radiation. METHODS: The effect of intestinal trefoil factor on migration and cell survival in intestinal epithelial monolayer exposed to methotrexate was studied in vitro. Chemotherapy and radiation damage was assessed in wild-type and intestinal trefoil factor-null mice in the presence or absence of supplemental intestinal trefoil factor administered in drinking water. RESULTS: Radiation and chemotherapy induced a marked reduction in goblet cell number and intestinal trefoil factor messenger RNA, as well as intestinal trefoil factor promoter activity. Intestinal trefoil factor improved intestinal epithelial cell viability and wound repair after chemotherapy exposure in vitro. Intestinal trefoil factor-deficient mice (intestinal trefoil factor(-/-)) were more susceptible to chemotherapy- and radiation-induced mucositis. Oral recombinant intestinal trefoil factor reduced the severity of both chemotherapy-induced and chemotherapy/radiotherapy-induced intestinal mucositis. CONCLUSIONS: These studies suggest that intestinal trefoil factor is involved in protection against and recovery from intestinal mucositis induced by radiation and chemotherapy.

Animals↗

PubMed2004

Influence of different recombinant systems on the cooperativity exhibited by cytochrome P4503A4.

1. The in vitro cooperativity exhibited by cytochrome P450 (CYP) 3A4 is influenced by the nature of the recombinant system in which the phenomenon is studied. Diclofenac, piroxicam and R-warfarin were used as model substrates, and quinidine was the effector. 2. The 5-, 5'- and 10-hydroxylation of diclofenac, piroxicam and R-warfarin, respectively, were enhanced five- to sevenfold by quinidine in human liver microsomal incubations. Whereas these cooperative drug interactions were apparent in incubations with CYP3A4 expressed in human lymphoblast cells, similar phenomena were not observed with the enzyme expressed in insect cells. 3. Insect cell microsomes were treated with a detergent and CYP3A4 was solubilized into a buffer medium. In incubations with CYP3A4 'freed' from its host membrane, the 5-hydroxylation of diclofenac increased with increasing quinidine concentrations, reaching a maximal eightfold elevation relative to controls. The metabolism of piroxicam and warfarin was similarly enhanced by quinidine. 4. Kinetically, enhancement by quinidine of the 5-hydroxylation of diclofenac in incubations with solubilized CYP3A4 was characterized by increases in the rate of metabolism with little change in the substrate-binding affinity. Conversely, the 3-hydroxylation of quinidine was not affected by diclofenac. 5. The data suggest that certain properties of CYP3A4 are masked by expression of the protein in insect cells and reinforce the concept that the enzyme possesses multiple binding domains. The absence of cooperative drug interactions with quinidine when CYP3A4 was expressed in insect cells might be due to an absence of enzyme conformation changes on quinidine binding, or the inability of quinidine to gain access to a putative effector-binding domain. 6. Caution should be exercised when comparing models for CYP3A4 cooperativity derived from different recombinant preparations of the enzyme.

Animals↗

PubMed2004

In vitro assessment of intestinal permeability and hepatic metabolism of 4'-bromoflavone, a promising cancer chemopreventive agent.

1. The intestinal permeability and hepatic metabolism of the investigational cancer chemoprevention agent 4'-bromoflavone were investigated in vitro using human intestinal Caco-2 cell monolayers, human liver microsomes and human hepatocytes. Liquid chromatography-mass spectrometry and tandem mass spectrometry were used for quantitative analysis in support of the Caco-2 cell studies and for the characterization of metabolites of 4'-bromoflavone. 2. The Caco-2 cell model indicated that 4'-bromoflavone would be absorbed by the intestine at a moderate rate by means of direction-independent, passive diffusion. There was no indication of active transport or efflux. 3. Three monohydroxylated metabolites and one monohydroxylated, hydrated metabolite of 4'-bromoflavone were detected at relatively low levels in the human liver microsomal and hepatocyte incubations. The structures of these metabolites were confirmed by comparison with synthetic standards. Hydroxylation occurred on the A-ring of 4'-bromoflavone but not on the B-ring, probably due to deactivation of the B-ring by bromine. No phase II metabolites were detected following incubation of 4'-bromoflavone in these in vitro systems. 4. In conclusion, these studies predict that 4'-bromoflavone should show moderate oral bioavailability, and that it would probably be excreted as unchanged compound and monohydroxylated metabolites. The results might be helpful in the design of clinical trials and in the interpretation of pharmacokinetic studies of 4'-bromoflavone.

Antineoplastic Agents↗

PubMed2004

Identification of a novel HLA-DRB1 allele (DRB11147) by sequence-based typing in eight siblings.

We report here a novel DRB1 allele (DRB1*1147) identified by sequence-based typing. The DRB1*1147 allele was detected during routine human leukocyte antigen (HLA)-typing of a patient and his family prior to bone marrow transplantation. This allele was found in the patient and his two sisters and five brothers. The new allele is identical to DRB1*110601 at exon 2 except for a single-nucleotide substitution at codon 37 (TAC-->TCC), changing the encoded tyrosine to serine.

Alleles↗

PubMed2004

Activation of postsynaptic GABAB receptors modulate the firing activity of supraoptic oxytocin and vasopressin neurones: role of calcium channels.

Oxytocin and vasopressin release from neurohypophysial terminals is closely related to the firing activity of magnocellular neurones in the supraoptic (SON) and paraventricular nuclei. It is well established that activation of GABAA receptors potently inhibits the activity of SON neurones and, thus, hormone release. However, whether postsynaptic GABAB receptors are expressed in magnocellular neurones, and the role they play in controlling their firing activity, is still controversial. In the present work, we combined immunohistochemical and electrophysiological techniques to determine whether activation of GABAB receptors in identified oxytocin and vasopressin neurones modulates their firing activity. Patch-clamp recordings from SON neurones were obtained either in the slice preparation or from acutely dissociated neurones. Activation of GABAB receptors with the selective agonist baclofen (10 micro m) inhibited voltage-gated Ca2+ currents, reduced the duration of individual action potentials, as well as the magnitude of the hyperpolarizing after-potential. SON firing activity was reduced by baclofen, and effect that was accompanied by a small membrane hyperpolarization. The inhibition of firing discharge persisted in the presence of synaptic blockade media, and was also observed in acutely dissociated SON neurones. Finally, GABAB-mediated modulation of firing activity was largely blocked by the Ca2+ channel blocker Co2+ (2 mm). In general, baclofen modulatory actions were significantly larger, or observed more predominantly, in vasopressin neurones. In summary, these results support the expression of functional postsynaptic GABAB receptors in SON neurones, activation of which efficiently modulates neuronal excitability, in a Ca2+- and cell-type dependent manner.

Action Potentials↗