Search PubMed⌕ Search

Biomedical subjects

Jun Li

Publications and source records attributed to Jun Li.

At least 505 records · Page 28Linked to original sources
PubMed2003

Au20: a tetrahedral cluster.

Photoelectron spectroscopy revealed that a 20-atom gold cluster has an extremely large energy gap, which is even greater than that of C60, and an electron affinity comparable with that of C60. This observation suggests that the Au20 cluster should be highly stable and chemically inert. Using relativistic density functional calculations, we found that Au20 possesses a tetrahedral structure, which is a fragment of the face-centered cubic lattice of bulk gold with a small structural relaxation. Au20 is thus a unique molecule with atomic packing similar to that of bulk gold but with very different properties.

Journal Article↗
PubMed2003

The efficiency of humoral immune transfer depends on both the graft and the immunosuppressive treatment.

The present study was designed to compare the efficiency of adoptive transfer of humoral immunity after liver, kidney, and heart transplantation in relation to the number of passenger lymphocytes, and to estimate the risk of a detrimental effect and the chance of a beneficial effect. Hepatitis B virus surface-antigen-vaccinated brown Norway rats (BNs) and AxC 9935 Irish (ACI rats) served as donors, and naïve Lewis (LEW) rats as recipients. The liver grafts contained 100 times more passenger lymphocytes than heart grafts, and the kidney grafts approximately ten times more, indicated by monoclonal CD45 antibody staining. Transient anti-HBs immunity did occur after transplantation of all three organ grafts. In all rejecting groups, the serum recipient-to-donor anti-HBs titer ratio (R/D ratio) was below 0.10%, with heart recipients showing half the level (0.05%) of liver recipients (0.09%). Under immunosuppression, R/D ratio doubled in liver or kidney recipients, but remained unaffected in heart recipients. Immune transfer was most efficient in immune-suppressed liver recipients in the spontaneously tolerant strain combination as indicated by a significantly higher R/D ratio (0.32%) and a longer titer persistence (up to 9 weeks) than in all other groups. Therefore, mainly liver and kidney graft recipients carry a risk, but also a chance of benefiting from the transfer of donor-derived immunity.

Animals↗
PubMed2003

Asymmetric flaccid paralysis: a neuromuscular presentation of West Nile virus infection.

The neuromuscular aspects of West Nile virus (WNV) infection have not been characterized in detail. We have studied a group of six patients with proven WNV infection. All cases presented with acute, severe, asymmetric, or monolimb weakness, with minimal or no sensory disturbance after a mild flu-like prodrome. Four cases also had facial weakness. Three of our cases had no encephalitic signs or symptoms despite cerebrospinal fluid pleocytosis. Electrophysiological studies showed severe denervation in paralyzed limb muscles, suggesting either motor neuron or multiple ventral nerve root damage. This localization is supported further by the finding of abnormal signal intensity confined to the anterior horns on a lumbar spine magnetic resonance imaging. Muscle biopsies from three patients showed scattered necrotic fibers, implicating mild direct or indirect muscle damage from the WNV infection. In summary, we describe a group of patients with acute segmental flaccid paralysis with minimal or no encephalitic or sensory signs. We have localized the abnormality to either the spinal motor neurons or their ventral nerve roots. It will be important for physicians to consider WNV infection in patients with acute asymmetric paralysis with or without encephalitic symptoms.

Acute Disease↗
PubMed2003

Motor unit number estimate of distal and proximal muscles in Charcot-Marie-Tooth disease.

In order to determine the utility of motor unit number estimation (MUNE) in assessing axonal loss in chronic inherited neuropathies, we determined MUNEs in 54 patients with Charcot-Marie-Tooth (CMT) disease (29 patients with CMT-1A, 13 with CMT-X, and 12 with CMT-2) by using spike-triggered averaging (STA) of the ulnar-innervated abductor digiti minimi/hypothenar muscles (ADM) and the musculo-cutaneous innervated biceps/brachialis (BB) muscles. MUNEs were analyzed in relationship to the corresponding compound muscle action potential (CMAP) amplitudes as well as to clinical strength. Proximal muscles, which appeared strong clinically, had evidence of chronic denervation/reinnervation, although to a lesser extent than weak distal hand muscles, supporting the concept that axonal loss in CMT occurs in a length-dependent fashion. The reduction in ADM-MUNE strongly correlated with clinical weakness in the hand. Both the ADM-MUNE and BB-MUNE were abnormal more often than CMAP amplitude, probably reflecting extensive motor unit reconfiguration and enlargement that maintains CMAP amplitude despite severe motor unit loss. This study suggests that MUNE can assess motor unit loss in CMT and may better reflect axonal loss than CMAP amplitude. The STA technique of MUNE may be useful in longitudinal studies of proximal and distal motor unit changes in CMT.

Action Potentials↗
PubMed2003

BMP-2 and CDMP-2: stimulation of chondrocyte production of proteoglycan.

A hallmark of intervertebral disc degeneration is loss of proteoglycans. Cytokines may be used to stimulate proteoglycan production in the disc to reverse or prevent disc degeneration. The effects of bone morphogenetic protein 2 (BMP-2) and cartilage-derived morphogenetic protein 2 (CDMP-2) (singly and jointly) on proteoglycan synthesis by a chondrocytic cell line (MC615) were studied. MC615 cells were dosed with BMP-2, CDMP-2, or both, cultured for 6 days, and then assayed as follows: (1). The proteoglycan content of the medium and extracellular matrix were determined by dimethyl-methylene blue staining; (2). cell numbers were determined after 6 days of culture using the Hoechst dye DNA assay; (3). aggrecan mRNA was measured with the reverse transcription-polymerase chain reaction and Northern blotting assays. Both BMP-2 and CDMP-2 significantly enhanced proteoglycan production and aggrecan mRNA expression in a dose-dependent manner, although BMP-2 is more effective than CDMP-2 in increasing sulfated proteoglycan production. But BMP-2 and CDMP-2 have only a slight, nonsignificant effect on cell proliferation. There is no evidence of antagonism or synergy between the two growth factors in the aggrecan gene expression.

Animals↗
PubMed2003

Detection of antigen-specific T cell interferon gamma expression by ELISPOT and cytokine flow cytometry assays in rhesus macaques.

Both enzyme-linked immunospot (ELISPOT) and cytokine flow cytometry (CFC) methods have been developed for the detection of low-frequency, antigen-specific, cytokine-producing T cells following short-term in vitro stimulation. Peptide-based ELISPOT and CFC assays were compared for the quantitative detection of interferon gamma-positive (IFN-gamma+) antigen-specific T cells in rhesus macaques. Ten normal and nine simian immunodeficiency virus (SIV)-infected monkeys were tested for the detection of IFN-gamma+ memory T cells specific for p27(gag) peptides of SIV with both assays. The CFC assay detected more IFN-gamma+ cells than the ELISPOT assay and this assay was more informative in identifying the phenotype of responding cells. Cryopreserved cells were as functional as fresh cells in heparinized blood samples and compared to EDTA, heparin was the better anticoagulant for yielding IFN-gamma+ cells. Using overlapping peptide pools, 20-mer peptides were more efficient in stimulating CD4+ T cells than 15-mer peptides in the ELISPOT assay, but there was no significant difference between 20- and 15-mer peptides in detecting CD4 or CD8+, IFN-gamma+ T cells in the CFC assay.

Animals↗
PubMed2003

A gene family from Echinococcus granulosus differentially expressed in mature adult worms.

Differences in mRNA expression between immature adult worms (IAW) and mature adult worms (MAW) of Echinococcus granulosus were determined using polymerase chain reaction-based differential display (DDRT-PCR). Twenty-eight putative differential cDNA fragments were isolated, cloned and sequenced. mRNAs from IAW and MAW were probed with the labelled fragments. Six cDNA fragments (coded as egM12, egM13, egM22, egM26, egM30 and egM34) were putatively determined to be specific to MAW by Northern hybridisation. The stage-specificity of egM12, egM13 and egM34 was confirmed by RT-PCR. RNAs of IAW, MAW, protoscoleces and oncospheres, probed with egM13 and egM30, showed that the mRNAs were expressed exclusively in MAW, which implied involvement in the regulation of egg development. Using the labelled fragments to screen a cDNA library of MAW, 99 clones were identified and analysed. An alignment of selected clones showed that the MAW-specific mRNAs belonged to a family. Examination of the deduced amino acid sequence of three of the corresponding cDNAs (egM4, egM9 and egM123) indicated they were cysteine-rich and contained a 24 amino acid repeat sequence, repeated four to six times. The repeat regions were predominantly alpha helical in nature with interspersed turns, forming alternating zones of positive and negative charge. The functional significance of each of the cDNAs identified is unclear as none had significant sequence similarity to genes of known function. However, polypeptides encoded by egM4 and egM123 were recognised by antibodies in a serum pool from dogs experimentally infected with E. granulosus, suggesting they could prove of value in serodiagnosis of definitive hosts.

Amino Acid Sequence↗
PubMed2003

Overexpression of a small medicinal peptide from ginseng in the yeast Pichia pastoris.

A medicinal peptide, Gsp, which was initially extracted from the traditional medicinal herb ginseng, has potential use as a drug against diabetes. Gsp is a low molecular weight protein that we have secreted in a recombinant form from the yeast Pichia pastoris. A DNA fragment encoding four copies of the Gsp protein each separated by a basic amino acid was synthesized and inserted into the P. pastoris expression vector plasmid pPIC9. After electroporation of the resulting vector, pPIC9-Gsp, into the yeast, transformants were selected. Recombinant pre-Gsp secreted from P. pastoris had a molecular weight of 5.9 kDa and mature recombinant Gsp had a primary structure indistinguishable from native Gsp. After optimization of the culturing process, the yield of pre-Gsp reached 800 mg/L in the clarified broth. A continuous batch fermentation process was developed that allowed the same population of cells to be reutilized five times without loss of expression level. This continuous culturing process resulted in a substantial saving of both time and cost in pharmaceutical production and should be applicable to the production of other recombinant proteins in P. pastoris.

Animals↗
PubMed2003

Ionizing radiation increases adenovirus uptake and improves transgene expression in intrahepatic colon cancer xenografts.

Specific targeting and transgene expression in tumors are critical in adenovirus gene therapy for intrahepatic colon carcinoma metastases. In this study, we investigated if ionizing radiation could increase adenoviral uptake by cells. Various human cell lines and rat hepatocytes were irradiated prior to exposure to a cytomegalovirus (CMV) promoter-driven green fluorescent protein (GFP) marker gene adenoviral vector. We found that gamma-radiation increased the number of GFP-positive cells in a dose- and time-dependent manner for most cells, ranging from 4.6- to 27.1-fold after a 4-Gy treatment. No induction occurred for lentiviral vector, lipofection, or naked plasmid exposure. Preincubation of cells with adenovirus failed to show an increase, suggesting that radiation might mediate adenoviral infection by inducing viral uptake into cells. We demonstrated that radiation induced internalization of a fluorescence-labeled adenovirus (Cy3-Ad) and an increase in intracellular viral DNA content. Rats bearing intrahepatic colon carcinoma xenografts were irradiated in the tumor region followed by portal venous administration of an adenoviral vector containing a CMV-beta-galactosidase (beta-gal) gene. Radiation increased beta-gal activity in tumors as much as 5.4-fold after a 25-Gy treatment. These data suggest that a combination of regional radiation treatment with adenovirus gene therapy is a rational strategy for improving adenoviral targeting and transgene expression in tumors.

Adenoviridae↗
PubMed2003

Gene identification and expression analysis of 86,136 Expressed Sequence Tags (EST) from the rice genome.

Expressed Sequence Tag (EST) analysis has pioneered genome-wide gene discovery and expression profiling. In order to establish a gene expression index in the rice cultivar indica, we sequenced and analyzed 86,136 ESTs from nine rice cDNA libraries from the super hybrid cultivar LYP9 and its parental cultivars. We assembled these ESTs into 13,232 contigs and leave 8,976 singletons. Overall, 7,497 sequences were found similar to existing sequences in GenBank and 14,711 are novel. These sequences are classified by molecular function, biological process and pathways according to the Gene Ontology. We compared our sequenced ESTs with the publicly available 95,000 ESTs from japonica, and found little sequence variation, despite the large difference between genome sequences. We then assembled the combined 173,000 rice ESTs for further analysis. Using the pooled ESTs, we compared gene expression in metabolism pathway between rice and Arabidopsis according to KEGG. We further profiled gene expression patterns in different tissues, developmental stages, and in a conditional sterile mutant, after checking the libraries are comparable by means of sequence coverage. We also identified some possible library specific genes and a number of enzymes and transcription factors that contribute to rice development.

Arabidopsis↗
PubMed2003

The growth-inhibitory Ndrg1 gene is a Myc negative target in human neuroblastomas and other cell types with overexpressed N- or c-myc.

A major prognostic marker for neuroblastoma (Nb) is N-myc gene amplification, which predicts a poor clinical outcome. We sought genes differentially expressed on a consistent basis between multiple human Nb cell lines bearing normal versus amplified N-myc, in hopes of finding target genes that might clarify how N-myc overexpression translates into poor clinical prognosis. Using differential display, we find the previously described growth-inhibitory gene Ndrg1 is strongly repressed in all tested Nb cell lines bearing N-myc amplification, as well as in a neuroepithelioma line with amplified c-myc. Overexpression of N-myc in non-amplified Nb cells leads to repression of Ndrg1, as does activation of an inducible c-myc transgene in fibroblasts. Conversely, N-myc downregulation in N-myc-amplified Nb cells results in re-expression of the Ndrg1, and stimuli known to induce Ndrg1 do so in Nb cells while simultaneously down-regulating N-myc. Relevant to these results, we demonstrate an in vitro interaction of Myc protein with the Ndrg1 core promoter. We also find that Ndrg1 levels increase dramatically during in vitro differentiation of two cell lines modeling neural and glial development, while c- and N-myc levels decline. Our results combined with previous information on the Ndrg1 gene product suggest that downregulation of this gene is an important component of N-Myc effects in neuroblastomas with poor clinical outcome. In support of this notion, we find that re-expression of Ndrg1 in high-Myc Nb cells results in smaller cells with reduced colony size in soft-agar assays, further underscoring the functional significance of this gene in human neuroblastoma cells.

Agar↗
PubMed2003

Resources for targeted insertional and deletional mutagenesis in Arabidopsis.

The maize transposons Activator (Ac) and Dissociation (Ds) are active in many monocots and dicots, including Arabidopsis. We describe a new Ac-derived transposon construct, designated the Ds-loxP T-DNA, which can be used for both insertional and deletional mutagenesis. There are loxP sites in both orientations on both the transposon and the donor site T-DNA and an arrangement of marker genes that permits selection of transposition events, as well as deletions and inversions extending from the donor site to a transposon reinserted on either side of it. We show that Cre-mediated deletions and inversions occur at a high frequency. The tendency of Ac-Ds transposons to reinsert near the donor site can be used to target both insertional and deletional mutagenesis, but efficient exploitation of this property requires a library of mapped marked donor sites distributed in the genome. We have created a population of independent Ds T-DNA transformants and we have mapped an initial set of 75 Ds T-DNA integration sites. We assessed the potential efficiency of targeted mutagenesis by detecting Ds reinsertion events at several loci over a 400 kb interval from each of two donor sites with different Ds T-DNA constructs. The distribution of reinsertion sites is similar around the two tested loci, with roughly 10, 4, and ca. 1% of reinsertions detected within 1-2 kb of sites 10, 100, and 200-400 kb from the donor site, respectively. To facilitate the use of this targeted mutagenesis system. we have constructed a searchable database of the mapped Ds T-DNA integration sites.

Arabidopsis↗
PubMed2003

Spiers memorial lecture. The quantum chemistry of d- and f-element complexes: from an approximate existence to functional happiness.

The field of modern quantum inorganic chemistry is just over 50 years old, dating back to 1951, when quantitative LCAO molecular orbital theory was developed and ferrocene was discovered. This Lecture provides a survey of the development of the field through about 1980, which has led to its current state. The application of modern quantum chemical techniques are illustrated via two disparate examples from the authors' research group. First, the recent discovery of uranium-noble gas bonds is discussed including the synergy between the theoretical and experimental investigations of this phenomenon. New theoretical results using coupled-cluster [CCSD(T)] methodology is contrasted to the original scalar-relativistic density functional theory results. Second, new applications of time-dependent density functional theory to the rich photochemistry of a dinuclear organometallic complex, (eta5-C5H5)2Fe2(mu-CO)2(CO)2, are discussed.

Journal Article↗
PubMed2003

Immunoglobulin profiles in a murine intermediate host model of resistance for Echinococcus granulosus infection.

We have shown previously that primary infection of Chinese Kunming (CKM) mice with Echinococcus granulosus oncospheres is protective against subsequent challenge. Nine groups of mice were infected with the oncospheres of E. granulosus by different routes (intraperitoneal, subcutaneous or intravenous injection). After infection, serum was collected after different periods of time and serum antibodies were tested by ELISA against oncospheral proteins and hydatid cyst fluid antigens. The results indicated that CKM mice produced low levels of antibodies before a secondary challenge infection given 3 weeks later by a different route. Most mice did not evoke significant antibody responses against oncospheral antigens until 5 weeks after infection. The level of IgG, especially IgG1 against oncospheral antigens increased from week 4 post-infection (p.i.), to a maximum at week 9 p.i. In addition, antibodies against hydatid cyst fluid antigens increased at the same time as the recognition of oncospheral antigens. Immunoblots using hydatid cyst fluid showed that the first antigen that was recognized - an 8-kDa protein, possibly the smallest subunit of Antigen B - appeared 5-6 weeks p.i. and reactivity to this molecule was intensive at week 9 p.i. The results suggest that protection against secondary infection was not principally antibody-mediated during the initial phases of infection, when cellular immune responses may play a pivotal role in the protective mechanism.

Animals↗
PubMed2003

Radiography of soft tissue of the foot and ankle with diffraction enhanced imaging.

Non-calcified tissues, including tendons, ligaments, adipose tissue and cartilage, are not visible, for any practical purposes, with conventional X-ray imaging. Therefore, any pathological changes in these tissues generally necessitate detection through magnetic resonance imaging or ultrasound technology. Until recently the development of an X-ray imaging technique that could detect both bone and soft tissues seemed unrealistic. However, the introduction of diffraction enhanced X-ray imaging (DEI) which is capable of rendering images with absorption, refraction and scatter rejection qualities has allowed detection of specific soft tissues based on small differences in tissue densities. Here we show for the first time that DEI allows high contrast imaging of soft tissues, including ligaments, tendons and adipose tissue, of the human foot and ankle.

Adipose Tissue↗
PubMed2003

AMPK-beta1 subunit is a p53-independent stress responsive protein that inhibits tumor cell growth upon forced expression.

In an effort to search for genes responsible for cell growth arrest and/or apoptosis associated with p53 signaling pathways, we profiled a human lung carcinoma line H1299, expressing a temperature-sensitive p53 (V138) against Affymetric human U95Av2 GeneChip A, consisting of 12 000 genes. 133 genes were identified that were either induced or repressed in response to p53-dependent cell growth arrest and apoptotic conditions. Among them, the beta1 subunit, but not other subunits of the AMP-activated protein kinase (AMPK) was strongly induced. The p53 consensus binding site search in the AMPK-beta1 promoter and the first intron identified four such putative sites. However, p53 failed to bind to any of these sites as assayed by in vitro gel retardation and in vivo chromatin immunoprecipitation. Furthermore, northern analysis showed that induction of this gene is independent of p53, as increased expression of the gene was observed in p53 null H1299/Neo control cells when the temperature was shifted to 32 degrees C. Moreover, a DNA damaging agent, etoposide, also induced beta1 subunit expression in multiple human tumor cells, regardless of p53 status. Thus, the beta1 subunit of AMPK is not a p53 downstream target gene, but can be induced by cold shock or the chemotherapeutic drug, etoposide in a p53-independent manner. To determine the biological significance of AMPK-beta1 induction, we over-expressed the gene in two tumor cell lines, H1299 and U2-OS. In both lines, forced AMPK-beta1 expression inhibits tumor cell growth, suggesting that AMPK-beta1 induction may facilitate stress-induced growth inhibition and cell killing.

AMP-Activated Protein Kinases↗
PubMed2003

The free thoracoumbilical flap for resurfacing large soft-tissue defects of the lower extremity.

Both cadavers and living patients were studied regarding a method to resolve large skin defects with bone exposure in the leg, with long-distance thrombosis of the anterior tibial vessels or posterior tibial vessels resulting from traumatic lesions. Forty-six casting mold specimens of cadaveric legs were investigated. There were rich communication branches among the anterior tibial artery, posterior tibial artery, and fibular artery in the foot and ankle, which complemented each other well. Twenty-six patients with large skin defects with bone exposure in the proximal or middle segment of the leg were admitted to the authors' hospital. Among those patients, 19 demonstrated long-distance thrombosis of the anterior tibial vessels or posterior tibial vessels resulting from traumatic lesions. During treatment, a thoracoumbilical flap based on the inferior epigastric vessels was anastomosed to the distal stump of the anterior tibial vessels or the posterior tibial vessels, with reversed flow. All defects were successfully repaired, with good color and texture matches of the flaps. This method can be used for patients with normal anterior tibial vessels or posterior tibial vessels, normal distal stumps of the injured blood vessels, and good reversed flow. The method has the advantages of dissecting blood vessels in the recipient area during the débridement, not affecting the blood circulation of the injured leg, not sacrificing blood vessels of the opposite leg, and not fixing the patient in a forced posture. The muscles are less bulky in the distal one-third of the leg, and the blood vessels are shallow and can be dissected and anastomosed easily. When the flap is used for reconstruction in the proximal two-thirds of the leg, the blood vessel pedicle of the free flap is at a straight angle, without kinking.

Adolescent↗