Biomedical subjects

L Pan

Publications and source records attributed to L Pan.

At least 55 records · Page 3Linked to original sources

PubMed2000

A genetic investigation of E2A function in lymphocyte development.

Lymphocytes are derived from hematopoietic stem cells (HSC) following a series of regulated differentiation events. Multipotent HSCs become committed to the B cell lineage in bone marrow and the T cell lineage in the thymus after receiving appropriate signals from the corresponding microenvironment. These committed lymphoid cells must then undergo V(D)J recombination at the immunoglobulin gene or T cell receptor gene locus resulting in clonal production of functional B or T lymphocytes, respectively. Lymphocyte commitment and differentiation are accompanied by programmed gene expression or repression events which are driven by lineage and stage specific transcription factors. The basic-helix-loop-helix (bHLH) transcription factors encoded by the E2A gene are involved in several differentiation events during B and T cell development, including lineage commitment, initiation of V(D)J recombination, and antigen receptor mediated proliferation and differentiation. Several recent reviews have provided a comprehensive discussion of biochemical, cellular, and genetic research on E2A function in lymphocyte development (1,2). Here, we only discuss some of the genetic approaches our laboratory (except where it is noted) has undertaken to investigate the molecular pathways mediated by E2A transcription factors in lymphocyte development.

Animals↗

PubMed2000

Gamma knife radiosurgery as a primary treatment for prolactinomas.

OBJECT: The purpose of this study was to estimate the efficacy of gamma knife radiosurgery (GKS) in controlling tumor growth and endocrinopathy associated with prolactinomas. METHODS: Between 1993 and 1997, 164 of 469 patients with pituitary adenomas treated by GKS harbored prolactinomas. The dose to the tumor margin ranged from 9 to 35 Gy (mean 31.2 Gy), and the visual pathways were exposed to a dose of less than 10 Gy. The mean tumor diameter was 13.4 mm. The mean follow-up time for 128 cases was 33.2 months (range 6-72 months). Tumor control was observed in all but two patients who underwent surgery 18 and 36 months, respectively, after GKS. Clinical cure was achieved in 67 cases. Clinical improvement was noted with a decrease in the hyperprolactinemia after GKS. Nonetheless, in 31 (29%) of 108 patients who were followed for more than 2 years no improvement in serum prolactin levels was demonstrated, although this could be normalized by bromocriptine administration after treatment. Nine infertile women became pregnant 2 to 13 months after GKS and all gave birth to normal children. There was no visual deterioration related to GKS. Five women experienced premature menopause. In these patients there was subtotal disappearance of the tumor and an empty sella developed. CONCLUSIONS: Gamma knife radiosurgery as a primary treatment for prolactinomas can be safe and effective both for controlling tumor growth and for normalization of prolactin hypersecretion. A higher margin dose (> or = 30 Gy) seemed to be associated with a better clinical outcome. Gamma knife radiosurgery may make prolactinomas more sensitive to the bromocriptine.

Humans↗

PubMed2000

Novel Single- and Double-Layer and Three-Dimensional Structures of Rare-Earth Metal Coordination Polymers: The Effect of Lanthanide Contraction and Acidity Control in Crystal Structure Formation.

Lanthanide atom sizes (the lanthanide contraction) directly control the type of structure formed by the coordination of a single multidentate ligand, 3,5-pyrazoledicarboxylic acid (H(3)pdc). Single-layer, double-layer ([Eu(2)(Hpdc)(3)(H(2)O)(6)], see picture), and three-dimensional networks were found. Control of the reaction pH plays a key role in the structure formation in this system.

Journal Article↗

PubMed2000

[Study of mdr1 antisense oligodeoxynucleotides on reversal of multidrug resistance in ovarian carcinoma cell line SKOV3].

OBJECTIVE: To investigate the effect of mdr1 antisense oligodeoxynucleotides (ASON) on reversal of multidrug resistance in ovarian carcinoma cells. METHODS: Drug resistance ovarian carcinoma cells SKOV3/mdr1 transducted with human multidrug resistance gene (mdr1) were served as models. The positive rate and function of the mdr1 gene product P-glycoprotein (P-gp) in SKOV3/mdr1 cells after mdr1-ASON (250 micrograms/ml) treatment were determined by flow cytometry and rhodamine 123 efflux trial. Drug resistance of SKOV3/mdr1 cells was also observed by cell colony culture. RESULTS: P-gp positive rate of SKOV3/mdr1 cells after mdr1-ASON treatment was decreased from 38.9% to 21.3% (P < 0.01). Intracellular rhodamine retension in SKOV3/mdr1 cells after mdr1-ASON treatment was increased from 32.1% to 50.7% (P < 0.01). Under effect of Taxol 5 ng/ml, the relative percents of drug-resistant colony in mdr1-ASON treated SKOV3/mdr1 cells and in SKOV3/mdr1 cells was 8% and 63%, respectively, (P < 0.01). Under effect of Doxorubicin 100 ng/ml, the relative percents of drug-resistant colony in mdr1-ASON treated SKOV3/mdr1 cells and in SKOV3/mdr1 cells was 34% and 79%, respectively, (P < 0.01). CONCLUSION: mdr1-ASON can reverse multidrug resistance of ovarian carcinoma cell in a certain extent so as to increase chemotherapeutic sensitivity of ovarian carcinoma cells.

Drug Resistance, Neoplasm↗

PubMed2000

[Determination of fructose-1,6-diphosphate with aldolase-DNPH by the colorimetric method].

This paper presents a modified method of enzymatic assay for Fructose-1,6-diphosphate(FDP). FDP is split to dihydroxyacetone phosphate (DAP) and glyceraldehyde-3-phosphate (GAP) by the action of aldolase. DAP is hydrolyzed at room temperature to free triose. Under alkaline conditions, the free triose is reacted with 2,4-dinitrophenylhydrazine (DNPH), yielding a 2,4-dinitrophenylhydrazine derivative which dissolve in alkali forming a purple color mixture, with maximum absorption at 540.nm. It is proportional to the contents of FDP. Because the method depends on the colorimetric determination of triose formed from fructose-1,6-diphosphate only by aldolase, glycerophosphate dehydrogenase/triosephosphate isomerase (GDH/TIM) and reduced nicotinamide adenine dinucleotide (NADH) which usually applied in multienzymatic method, are omitted in the modified method. The method is specific, convenient and accuracy for the determination of FDP.

Colorimetry↗

PubMed2000

[Chemoprotection of transfer of multidrug resistance gene into human hematopoietic progenitor cell].

OBJECTIVE: To observe the effect of the transfer of multidrug resistance gene (mdr1) into human hematopoietic progenitor cells (HPC) on the chemoprotection. METHODS: Human CD34+ cells served as a target of mdr1 gene transfer. Retroviral vector SF-mdr containing human total length mdr1cDNA was introduced into packing cells GP-envAM12 by liposome-mediated transfection. The mdr1 gene was transduced into human CD34+ cells by retroviral supernatants of packing cells. The integration and expression of the mdr1 gene and its protein (P170) in transduced cells were determined by PCR, RT-PCR, and flow cytometry. The drug resistance of chemotherapy in transduced HPC was determined by culturing colonies. RESULTS: The mdr1 gene was integrated and expressed in transduced CD34+ cells. The efficiency of mdr1 gene transfer was 10%-14%. Compared with untransduced controls, within a certain range of drug concentration, the number of drug-resistant colony in transduced HPC for taxol, doxorubicin, VCR and VP16 were increased by 3.6 +/- 2.1 fold, 2.9 +/- 0.3 fold, 1.9 +/- 0.4 fold, and 3.5 +/- 0.5 fold, respectively. CONCLUSION: The transfer of the mdr1 gene into human HPC can increase the drug resistance of the transduced cells to corresponding chemotherapeutic drugs that may provide some degree of chemoprotection for HPC.

Antigens, CD34↗

PubMed2000

[High-dose chemotherapy with peripheral-blood stem cells transplantation in patients with advanced gynecological malignant tumors].

OBJECTIVE: To evaluate the clinical effectiveness of high dose chemotherapy(HDC) with peripheral-blood stem cells transplantation(PBSCT) in the patients with advanced malignant tumors. METHODS: Four patients with advanced or refractory ovarian carcinoma and 1 patient with recurrent fallopian tube carcinoma received the HDC with PBSCT after optimal tumor debulking. Of whom 4 patients were with the recurrent or progressive tumors, 1 patient received HDC as primary chemotherapy. The response and toxicity were assessed after treatment. RESULTS: Among 5 patients, four patients are survival. One case died from the recurrence of juvenile granulosa cell tumor. The average survival periods were 21 months. The tumors were all recurrent among the 4 survival patients. The average periods of recurrence after HDC treatment was 9 months. The main toxicity of HDC was severe marrow suppression. The lowest value of the neutrophil count and platelet count was 0.05-0.2 x 10(9)/L and 7 x 10(9)/L-8 x 10(9)/L respectively. The median time to recover a neutrophil count greater than 0.5 x 10(9)/L was 14 days and a platelet count greater than 50 x 10(9)/L was 17 days. None of the patients was complicated with severe complications. CONCLUSIONS: HDC and PBSCT used for ovarian carcinoma was flexibility and security if the patient was selected strictly though its toxicity was severe. Further study among the chemorefactory recurrent patients need to try in the future.

Adult↗

PubMed2000

[Effects of arsenic trioxide on K562 cells stably expressing two promyelocytic leukemia-specific fusion proteins].

OBJECTIVE: To illustrate the possible roles of acute promyelocytic leukemia-specific chimeric proteins PML-RARalpha and PLZF-RARalpha in the effects of arsenic trioxide (As(2)O(3)). METHODS: K562 sublines stably expressing PML-RARalpha (K(PML() and PLZF-RARalpha (K(PLZF)) were established by retrovirus transfection with K(V) transfected empty vectors as controls. Effects of As(2)O(3) and all-trans retinoic acid (ATRA) on these sublines were analyzed through cell count, morphology, measurement of cellular DNA contents and differentiation antigens on flow cytometry. Subcellular distributions of PML-RARalpha proteins were observed with immunofluorescence. RESULTS: 1.0 micromol/L of As(2)O(3) did not induce cell apoptosis and differentiation, but it significantly inhibited the growth of K(V) sublines. As(2)O(3) showed the similar but more potent effects in K(PML) and K(PLZF) sublines. 1.0 micromol/L As(2)O(3) treatment for 3 days induced growth inhibition by 32% +/- 3%, 57% +/- 4% and 54% +/- 6%, respectively in K(V), K(PML) and K(PLZF) sublines. 1.0 micromol/L ATRA also exerted, to a less extent than As(2)O(3), growth-inhibitory effects in K(V) sublines, which became more obvious in K(PML) but not in K(PLZF) sublines. In addition, PML/PML-RARalpha proteins were decreased and even disappeared in K(V) and K(PML) sublines with the treatment of 1.0 micromol/L As(2)O(3) for 48 hours. CONCLUSION: PML-RARalpha and PLZF-RARalpha markedly enhance growth-inhibitory effects of As2)O3) on K562 cells.

Antineoplastic Agents↗

PubMed2000

[Dural arterovenous fistula involving cavernous sinus].

OBJECTIVE: To study the pathogenesis and treatment of dural arteriovenous fistulas (DAVFS) involving the cavernous sinus. METHODS: 32 cases were embolized with particle by microcatheterization via endovascular approach and ervation by digital substraction angiography. Of the 32 cases, 14 were embolized by microsoils through superior petrosal sinus approach into the cavernous sinus. RESULTS: In 28 of the 32 cases the fistulas were completely embolized angiographically. The fistulas were partly embolized in 4 of the 32 cases. The carotid artery was compressed for 6 months. One week later, the fistula disappeared angiographically. No fistulas were found during the follow-up for 6 months to 8 years. CONCLUSION: Endovascular treatment of DAVFS involving the cavernous sinus is effective.

Adolescent↗

PubMed2000

[Radiographic studies of cervical spine motion range in normal Chinese subjects with computer-assisted image analysis: full flexion and extension].

OBJECTIVES: To study the degenerative regularity of normal Chinese cervical spine by observing the motion range of full cervical flexion and extension, and to provide evidences for further investigation of cervical segmental instability. METHODS: 764 X-ray plain films of full cervical flexion and extension in 382 normal Chinese subjects (214 were male and 168 female) were investigated using self-designed cervical X-ray image analysis system. The subjects within the same sex group were divided into three groups according to the age: group A (20 years to 39 years), group B (40 years to 59 years) and group C (60 years to 76 years). During the full cervical flexion and extension motion, total intervertebral motion range (from C(2) - C(3) to C(6) - C(7)) and intervertebral motion range at each level were major parameters. RESULTS: The range of total intervertebral motion showed much greater mobility in group A than in group B and group C (P < 0.01) but no statistically significant difference between group B and group C (P > 0.05). The range of intervertebral motion was maximal at C(5) - C(6) in group A. The place of maximal motion shifted to the C(4) - C(5) in both group B and group C. C(2) - C(3) showed minimal mobility in all three groups. There was no statistically significant difference (P > 0.05) between male and female. CONCLUSIONS: The motion range and degenerative regularity of normal Chinese cervical spine were similar in either sex. The range of total intervertebral motion (from C(2) - C(3) to C(6) - C(7)) had a tendency to decrease rapidly and then became steady with age. For the range of intervertebral motion, the place of maximal motion shifted to the higher level with age from C(5) - C(6) in group A to C(4) - C(5) in group B and group C.

Adult↗

PubMed2000

[Exploration of factors increasing transfer efficiency of retroviral mediated multidrug resistance gene (mdr1) into human CD(34)(+) cells].

OBJECTIVE: To explore factors influencing transfer of retroviral mediated multidrug resistance gene (mdr1) into human CD(34)(+) cells. METHODS: Transduction efficiency in the presence of different combinations of cytokines and human bone marrow stromal cells plus cytokines were determined by flow cytometry (FCM). Drug resistance was evaluated by plating yields of cultured hematopoietic progenitor cells. The effect of Taxol at different concentrations on mdr1 gene transfer cells was determined by FCM. RESULT: Transduction efficiency in the presence of SCF + FL + IL-3 was higher than that in other combinations of cytokines (SCF + IL-6 + IL-3, SCF + IL-6 + IL-3 + Tpo, SCF + IL-3). Transduction efficiency (20.5%) in the presence of bone marrow stromal cells plus cytokines (SCF + FL + IL-3) was higher than that (15.2%) without stromal cells, and the number of drug-resistant colony-forming cells was more in the former than in the latter. The percentage of CD(34)(+) cell with the gene transduction at 10 ng/ml Taxol reached 38.5%. CONCLUSION: Human bone marrow stromal cells plus cytokines (SCF + FL + IL-3) is more effective in enhancing mdr1 gene transduction. Taxol at a certain concentration can enrich mdr1 gene transferred cells.

Antigens, CD34↗

PubMed2000

[Mechanism of tissue factor expression on NB4 cells down-regulated by all-trans retinoic acid and arsenic trioxide].

OBJECTIVE: To investigate molecular mechanism of tissue factor (TF) expression on acute promyelocytic leukemia cell line NB4 cells down-regulated by all-trans retinoic acid (ATRA) and arsenic trioxide (As(2)O(3)). METHODS: Cyclohexamide (CHX) inhibition test for de novo protein synthesis and actinomycin D (Act D) inhibition test for RNA synthesis were used to check the effect of ATRA on the TF expression. TF antigen of U937 cells transfected with pMSCV-PML-RARalpha treated with or without ATRA and As(2)O(3) was detected. RESULTS: CHX treatment completely suppressed the down-regulation effect of ATRA on the TF mRNA expression, Act D inhibition test showed that half-life of TF mRNA in treated NB4 cells was shortened to about 30 min from that of around 60 min in untreated NB4 cells. The TF antigen contents in U937 cells transfected with pMSCV-PML-RARalpha were significantly higher than that in transfected U937 cells with retrovirus vector. Both ATRA and As(2)O(3) could down-regulate the TF antigen level in U937 cells transfected with or without PML-RARalpha. CONCLUSION: The modulation of the TF mRNA expression in NB4 cells by ATRA might be indirect. TF mRNA destabilization was involved in the TF regulation process mediated by ATRA. Elevated TF antigen level in U937 cells transfected with pMSCV-PML-RARalpha may be related to the fusion protein PML-RARalpha. The down-regulation effect of ATRA and As(2)O(3) on the TF expression of U937 cells might not involve the fusion protein.

Antineoplastic Agents↗

PubMed1999

Evolutionally conserved plant homologue of the Bax inhibitor-1 (BI-1) gene capable of suppressing Bax-induced cell death in yeast(1).

The plant homologue of Bax Inhibitor-1, a gene described to suppress the cell death induced by Bax gene expression in yeast, was isolated from Oryza sativa L. (rice) and Arabidopsis. The amino acid sequence of the predicted protein was well conserved in both animal and plant (45% in amino acids) and contained six or seven membrane-spanning segments. Northern blot analysis showed that OsBI-1 transcripts were present in all tissues examined. The OsBI-1 cDNA suppressed cell death induced by mammalian Bax in yeast, suggesting functional conservation of this BI-1 homologue in the plant kingdom.

Amino Acid Sequence↗

PubMed1999

Stat protein transactivation domains recruit p300/CBP through widely divergent sequences.

The signal transduction and activator of transcription (Stat) gene family has been highly conserved throughout evolution. Gene duplication and divergence has produced 7 mammalian Stat genes, each of which mediates a distinct process. While some Stat proteins are activated by multiple cytokines, Stat2 is highly specific for responses to type I interferon. We have cloned mouse Stat2 and found that while its sequence was more divergent from its human homologue than any other mouse-human Stat pairs, it was fully functional even in human cells. Overall sequence identity was only 69%, compared with 85-99% similarity for other Stat genes, and several individual domains that still served similar or identical functions in both species were even less well conserved. The coiled-coil domain responsible for interaction with IRF9 was only 65% identical and yet mouse Stat2 interacted with either human or mouse IRF9; the carboxyl terminus was only 30% identical and yet both regions functioned as equal transactivation domains. Both mouse and human transactivation domains recruited the p300/CBP coactivator and were equally sensitive to inhibition by adenovirus E1A protein. Interestingly, the Stat3 carboxyl terminus also functioned as a transactivator capable of recruiting p300/CBP, as does the Stat1 protein, although with widely differing potencies. Yet these proteins share no sequence similarity with Stat2. These data demonstrate that highly diverged primary sequences can serve similar or identical functions, and that the minimal regions of similarity between human and mouse Stat2 may define the critical determinants for function.

Amino Acid Sequence↗

PubMed1999

Human anti-porcine T cell response: blocking with anti-class I antibody leads to hyporesponsiveness and a switch in cytokine production.

Intervention in the molecular interactions that lead to an immune response is possible at various stages of Ag recognition and T cell activation. Perturbation of the interaction of the TCR with the MHC/peptide ligand complex is one approach that has shown promise for autoimmunity and graft rejection in blocking T cell-activated responses. In this study, we investigated the effect of altering the target MHC class I molecule by blocking with Abs. We established a system that analyzed the human T cell response against MHC class I+/class II- porcine stimulatory cell targets. The primary human response against porcine smooth muscle cells was CD8+ T cell dependent. In the presence of F(ab')2 fragments of the MHC class I-reactive Ab, PT-85, the proliferative response was inhibited and production of IL-2 and IFN-gamma was blocked. Moreover, in a secondary response, proliferation was reduced and type 1 cytokine levels were inhibited. In contrast, levels of IL-10 and IL-4 were sustained or slightly increased. These findings indicate that Ab against MHC class I blocked the recognition of porcine cells by the human CD8+ T cells and altered the cytokine secretion profile. Thus, a single treatment with PT-85 F(ab')2 directed against the MHC class I molecule provides an attractive approach to the induction of T cell tolerance that may provide long-term graft survival in porcine-to-human cell transplantation.

Animals↗

PubMed1999

Granulocyte colony-stimulating factor-mobilized allogeneic stem cell transplantation maintains graft-versus-leukemia effects through a perforin-dependent pathway while preventing graft-versus-host disease.

Minimization of graft-versus-host disease (GVHD) with preservation of the graft-versus-leukemia (GVL) effect is a crucial step to improve the overall survival of allogeneic bone marrow transplantation (BMT) for patients with hematological malignancies. We and other investigators have shown that granulocyte colony-stimulating factor (G-CSF)-mobilized allogeneic peripheral stem cell transplantation (PBSCT) reduces the severity of acute GVHD in murine models. In this study, we investigated whether G-CSF-mobilized PBSC maintain their GVL effect in a murine allogeneic transplant model (B6 --> B6D2F1). B6 mice (H-2(b)) were injected subcutaneously with human G-CSF (100 micrograms/kg/d) for 6 days and their splenocytes were harvested on day 7 as a source of PBSC. G-CSF mobilization dramatically improved transplant survival compared with nonmobilized controls (95% v 0%, P <.001). Systemic levels of lipopolysaccharide and tumor necrosis factor-alpha were markedly reduced in recipients of allogeneic G-CSF-mobilized donors, but cytolytic T lymphocyte (CTL) activity against host tumor target cells p815 was retained in those recipients. When leukemia was induced in recipients by coinjection of p815 tumor cells (H-2(d)) at the time of transplantation, all surviving recipients of G-CSF-mobilized B6 donors were leukemia-free at day 70 after transplant, whereas all mice who received T-cell-depleted (TCD) splenocytes from G-CSF-mobilized B6 donors died of leukemia. When splenocytes from G-CSF-mobilized perforin-deficient (pfp-/-) mice were used for transplantation, 90% of recipients died of leukemia, demonstrating that perforin is a crucial pathway mediating GVL effects after G-CSF-mobilized PBSCT. These data illustrate that G-CSF-mobilized allogeneic PBSCT separate GVL from GVHD by preserving perforin-dependent donor CTL activity while reducing systemic inflammation.

Animals↗

PubMed1999

High-performance liquid chromatography separation and quantitation of ofloxacin enantiomers in rat microsomes.

A sensitive, simple and accurate method for determination of enantiomers of ofloxacin in microsomal incubates was developed by chiral ligand-exchange RP-HPLC with fluorescence detection to examine stereoselective metabolism of ofloxacin in the glucuronidation process. The C18 stationary phase was used as analytical column. The solution of chiral mobile phase additive was made up of 6 mM L-phenylalamine mixed with 3 mM CuSO4 in water. Mobile phase consisted of the solution of chiral mobile phase additive-methanol (86:14). The fluorescence detector was operated at lambda(ex) 330 nm and lambda(em) 505 nm. The flow-rate of mobile phase was set at 1.0 ml/min. The achiral ODS column offers good separation of the two enantiomers in less than 25 min. The recovery of the assay was 97.9+/-6.1% (n=10) for S-ofloxacin and 99.6+/-6.0% (n = 10) for R-ofloxacin. The method provides a high sensitivity and good precision (RSD<10%). The LOD was 0.6 microM for both enantiomers and the LOQ was 5.70+/-0.45 microM (n=8) for S-ofloxacin and 5.66+/-0.47 microM (n=8) for R-ofloxacin. The standard curves showed excellent linearity over the concentration range 5.5-2078 microM for S-(-)-ofloxacin and R-(+)-ofloxacin. The enantioselective method developed has been applied to determine the stereoselectivity of glucuronidation metabolism of ofloxacin optical isomers in rat liver microsomes.

Animals↗

PubMed1999

Bcl10 is involved in t(1;14)(p22;q32) of MALT B cell lymphoma and mutated in multiple tumor types.

MALT B cell lymphomas with t(1;14)(p22;q32) showed a recurrent breakpoint upstream of the promoter of a novel gene, Bcl10. Bcl10 is a cellular homolog of the equine herpesvirus-2 E10 gene: both contain an amino-terminal caspase recruitment domain (CARD) homologous to that found in several apoptotic molecules. Bcl10 and E10 activated NF-kappaB but caused apoptosis of 293 cells. Bcl10 expressed in a MALT lymphoma exhibited a frameshift mutation resulting in truncation distal to the CARD. Truncated Bcl10 activated NF-kappaB but did not induce apoptosis. Wild-type Bcl10 suppressed transformation, whereas mutant forms had lost this activity and displayed gain-of-function transforming activity. Similar mutations were detected in other tumor types, indicating that Bcl10 may be commonly involved in the pathogenesis of human malignancy.

Adaptor Proteins, Signal Transducing↗