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L Bai

Publications and source records attributed to L Bai.

At least 37 records · Page 2Linked to original sources
PubMed2001

Transcriptional regulation of rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene by Sp1 transcription factor.

The rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene promoter lacks a TATA box and is very GC rich. A minimal promoter extending from bp -36 to +116 directs high-level expression of NHE-2 in mouse inner medullary collecting duct (mIMCD-3) cells. Four Sp1 consensus elements were found in this region. The introduction of mutations within these Sp1 consensus elements and DNA footprinting revealed that only two of them were utilized and are critical for basal transcriptional activation in mIMCD-3 cells. The use of Sp1, Sp3, and Sp4 antisera in electrophoretic mobility shift assays demonstrated that Sp1, Sp3, and Sp4 bound to this minimal promoter. We further analyzed the transcriptional regulation of NHE-2 by members of the Sp1 multigene family. In Drosophila SL2 cells, which lack endogenous Sp1, the minimal promoter cannot drive transcription. Introduction of Sp1 activated transcription over 100-fold, suggesting that Sp1 is critical for transcriptional regulation. However, neither Sp3 nor Sp4 was able to activate transcription in these cells. Furthermore, in mIMCD-3 cells, Sp1-mediated transcriptional activation was repressed by expression of Sp3 and Sp4. These data suggest that Sp1 is critical for the basal promoter function of rat NHE-2 and that Sp3 and Sp4 may repress transcriptional activation by competing with Sp1 for binding to core cis-elements.

Animals↗
PubMed2001

Epidermal growth factor regulation of rat NHE2 gene expression.

Epidermal growth factor (EGF) is involved in acute regulation of Na(+)/H(+) exchangers (NHEs), but the effect of chronic EGF administration on NHE gene expression is unknown. The present studies showed that EGF treatment increased NHE2-mediated intestinal brush-border membrane vesicle Na(+) absorption and NHE2 mRNA abundance by nearly twofold in 19-day-old rats. However, no changes were observed in renal NHE2 mRNA or intestinal and renal NHE3 mRNA abundance. To understand the mechanism of this regulation, we developed the rat intestinal epithelial (RIE) cell as an in vitro model to study the effect of EGF on NHE2 gene expression. EGF increased functional NHE2 activity and mRNA abundance in cultured RIE cells, and this stimulation could be blocked by actinomycin D (a transcriptional inhibitor). Additionally, NHE2 promoter reporter gene assays in transiently transfected RIE cells showed an almost twofold increase in promoter activity after EGF treatment. We conclude that rat NHE2 activity can be stimulated by chronic EGF treatment and that this response is at least partially mediated by gene transcription.

Animals↗
PubMed2001

Spatiotemporal properties of an evoked population activity in rat sensory cortical slices.

We have examined the spatiotemporal properties of ensemble activity, an evoked all-or-none polysynaptic activity in rat neocortical slices. Ensemble activity occurred in cortical slices bathed in normal artificial cerebrospinal fluid (ACSF) and was evoked by a single electrical shock either to the white matter or directly to the cortical tissue. This activity was seen in slices of somatosensory and auditory cortices; in other cortical areas we have not been able to evoke it. The activity developed 10 to 250 ms poststimulus and lasted 280 +/- 120 ms in local field potential (LFP) recordings. Voltage-sensitive dye imaging showed that this activity was an area of activation 0.8 +/- 0.4 mm wide that propagated slowly (11.4 +/- 6.2 mm/s, n = 60, 6 animals) in the horizontal direction. Due to this propagation, the actual duration in the whole tissue may be longer (approximately 400 ms) than that recorded by a single LFP electrode. Ensemble activity produced a low-amplitude optical signal (7-14% of the interictal-like spikes in the same tissue), suggesting a moderate net depolarization of the population. These were very different from hyperexcitable (epileptiform) events in the same tissue that had about 10 times the optical signal amplitude and propagated at 125 +/- 24 mm/s (n = 21, 6 animals). On a global spatial scale (approximately 0.8 mm wide in layers II-III) ensemble activity had a smooth waveform in voltage-sensitive dye signals (population transmembrane potential). On a local scale, field potential recordings showed large fluctuations with complex oscillations and substantial trial-to-trial variation. This suggests that oscillations in cortical circuits occurred only in small clusters of correlated neurons. Ensemble activity was sensitive to the excitation-inhibition balance of the local network. Antagonists of N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and GABAa receptors, and muscarinic agonists and other modest manipulations such as increasing bath concentration of Mg(2+) to 2.5-4 mM (normally at 2 mM), or K(+) to 5-7 mM (normally 3 mM), all significantly reduced the probability of evoking the activity. The metabotropic glutamate receptor agonist, aminocyclopentane-1,3-dicarboxylic acid, blocked the activity at a low concentration (10-15 microM), while the antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine had no effect even at high concentration (240 microM). Our data suggest that locally organized neuronal clusters may play a role in the organization of oscillatory activities in the gamma band and may participate in cortical integration/amplification occurring on a scale of approximately 1 mm x 300 ms.

Animals↗
PubMed2000

Nuclear factor 1 (NF1) affects accurate termination and multiple-round transcription by human RNA polymerase III.

We have shown previously that the TFIIIC1/TFIIIC1' fraction interacts specifically with the VA1 terminator regions to affect both termination and initiation/reinitiation of transcription by human RNA polymerase III. Here, we further purified the VA1 terminator-binding factor to apparent homogeneity and found, by peptide sequence analysis, that it belongs to the NF1 protein family. NF1 interacts specifically with the NF1-binding sites within the terminator regions of the VA1 gene and with two subunits (TFIIIC220 and TFIIIC110) of human TFIIIC2. Immunodepletion with anti-NF1 antibodies dramatically decreases transcription from the VA1 template in nuclear extract, and mutation at the NF1-binding site in the terminator region of the VA1 gene selectively affects multiple-round transcription (reinitiation of transcription) and termination. In addition, NF1 acts in conjunction with TFIIIC to promote accurate termination by RNA polymerase III on a C-tailed VA1 template.

Base Sequence↗
PubMed2000

Molecular cloning of murine sodium-phosphate cotransporter type IIb (Na/P(i)-IIb) gene promoter and characterization of gene structure.

We report the cloning of the murine Na/P(i)-IIb cotransporter gene, which spans more than 18 kilobases and consists of 12 introns and 13 exons. Three promoter/reporter gene constructs, -159/+73, -429/+73 and -954/+73, showed significant luciferase activity (22-82-fold over background) when transfected into in rat intestinal epithelial (RIE-1) cells.

Animals↗
PubMed2000

Transcription factor ZBP-89 cooperates with histone acetyltransferase p300 during butyrate activation of p21waf1 transcription in human cells.

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(waf1) transcription is mediated through proximal GC-rich sites. Prior studies have shown that Sp1, Sp3, and the histone acetylase co-activator p300 are components of the complexes binding to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. This study sought to determine whether ZBP-89 rather than Sp1 is the direct target of p300 during butyrate induction of p21(waf1). ZBP-89 (BFCOL1, BERF-1, ZNF 148) is a Krüppel-type zinc finger transcription factor that binds to GC-rich elements and represses or activates known target genes. Adenoviral-mediated expression of ZBP-89 in HT-29 cells revealed that ZBP-89 potentiates butyrate induction of endogenous p21(waf1) gene expression. Further, cotransfection of a ZBP-89 expression vector with a 2.3-kilobase p21(waf1) reporter recapitulated the potentiation by butyrate. DNase I footprinting analysis of the human p21(waf1) promoter with recombinant ZBP-89 identified a binding site at -245 to -215. Electrophoretic mobility shift assays confirmed that both recombinant and endogenous ZBP-89 and Sp1 bind to this element. The potentiation was abolished in the presence of adenoviral protein E1A. Deletion of the N-terminal domain of ZBP-89 abolished the potentiation mediated by butyrate treatment. This same deletion mutant abolished the ZBP-89 interaction with p300. Cotransfection of p300 with ZBP-89 stimulated the p21(waf1) promoter in the absence of butyrate. p300 co-precipitated with ZBP-89 but not with Sp1, whereas ZBP-89 co-precipitated with Sp1. Together, these findings demonstrate that ZBP-89 also plays a critical role in butyrate activation of the p21(waf1) promoter and reveals preferential cooperation of this four-zinc finger transcription factor with p300.

Acetyltransferases↗
PubMed2000

[Effects of sodium selenite on the activity of GSH-Px and the life-span of Drosophila].

In order to investigate the effects of sodium selenite on the activity of glutathione peroxidase and the life-span of drosophila melanogaster, newly enclosed flies were divided randomly into 4 groups and fed with mediums containing different concentrations of sodium selenite. The activity of GSH-Px was determined by 5,5'-dithionbis (2-nitrobenzoic acid) (DTNB) photometric method. The life-span of drosophila was calculated after survival test. The results showed that the activity of GSH-Px in the female and male flies were increased by the increase of sodium selenite in the medium (P < 0.05). The average life-span and the average maximum life-span of flies in selenium groups were increased significantly as compared with control group (P < 0.05). The response of GSH-Px activity and life-span of male flies to selenium intake was better than that of females.

Animals↗
PubMed2000

In vitro cytotoxic effects of fludarabine (2-F-ara-A) in combination with commonly used antileukemic agents by isobologram analysis.

Fludarabine phosphate (2-F-ara-AMP) is an adenine nucleoside analogue that shows significant activity against chronic lymphocytic leukemia and indolent lymphoma. We assessed the cytotoxic interaction produced by the combination of the active metabolite of fludarabine phosphate, fludarabine (9-beta-D-arabinofuranosyl-2-fluoroadenine, 2-F-ara-A), and some commonly used antileukemic agents against human hairy cell leukemia cell line JOK-1, human chronic lymphocytic leukemia cell line SKW-3, and adult T cell leukemia cell lines ED-40810 (-) and SALT-3. The leukemia cells were exposed simultaneously to 2-F-ara-A and to the other agents for 4 days. Cell growth inhibition was determined using MTT reduction assay. The isobologram method of Steel and Peckham was used to evaluate the cytotoxic interaction. 2-F-ara-A and cytarabine showed synergistic effects in SKW-3 cells, additive and synergistic effects in JOK-1 and SALT-3 cells, and additive effects in ED-40810(-) cells. 2-F-ara-A and doxorubicin showed additive effects in SKW-3, ED-40810(-) and SALT-3 cell lines, and additive and synergistic effects in JOK-1 cells. 2-F-ara-A showed additive effects with etoposide, 4-hydroperoxy-cyclophosphamide, and hydroxyurea in all four cell lines. 2-F-ara-A showed antagonistic effects with methotrexate and vincristine in all four cell lines. Our findings suggest that the simultaneous administration of fludarabine phosphate with cytarabine, doxorubicin, etoposide, cyclophosphamide, or hydroxyurea would be advantageous for cytotoxic effects. Among these agents, cytarabine may be the best agent for the combination with fludarabine phosphate. The simultaneous administration of fludarabine phosphate with methotrexate or vincristine would have little cytotoxic effect, and this combination may be inappropriate. These findings may be useful in clinical trials of combination chemotherapy with fludarabine phosphate and these agents.

Antimetabolites, Antineoplastic↗
PubMed2000

Cloning and characterization of a type III Na-dependent phosphate cotransporter from mouse intestine.

Intestinal and renal absorption of inorganic phosphate (P(i)) is critical for phosphate homeostasis in mammals. We have isolated a cDNA that encodes a type III Na-dependent phosphate cotransporter from mouse small intestine (mPit-2). The nucleotide sequence of mPit-2 predicts a protein of 653 amino acids with at least 10 putative transmembrane domains. Kinetic studies, carried out in Xenopus oocytes, showed that mPit-2 cRNA induces significant Na-dependent P(i) uptake with an apparent Michaelis constant (K(m)) for phosphate of 38 microM. The transport of phosphate by mPit-2 is inhibited at high pH. Northern blot analysis demonstrated the presence of mPit-2 mRNA in various tissues, including intestine, kidney, heart, liver, brain, testis, and skin. The highest expression of mPit-2 in the intestine was found in the jejunum. In situ hybridization revealed that mPit-2 mRNA is expressed throughout the vertical crypt-villus axis of the intestinal epithelium. The presence of mPit-2 in the mouse intestine and its unique transport characteristics suggest that multiple Na-dependent cotransporters may contribute to phosphate absorption in the mammalian small intestine.

Animals↗
PubMed2000

Correlative factors of insulin resistance in essential hypertension.

Essential Hypertension (EH) is correlated with a metabolic disturbance characterized by insulin resistance (IR). In this study, there were observed in 47 subjects with EH and 30 subjects with normal blood pressure. Serum levels of insulin-like growth factor-1 (IGF-1), serum levels of growth hormone (GH), the activity of erythrocyte insulin receptors (EIR), and ATP levels in erythrocytes, the insulin sensitivity index (ISI) was used to study the correlative factors of essential hypertension. 1. Among patients with EH, ISI, GH, and low-affinity insulin binding sites of EIRs (RT2) were found to be in significantly lower amounts, IGF-1 levels and the KD2 of the erythrocyte insulin receptors were noted to be significantly higher. Compared with the control group, there was a marked difference between EH group and the control group. However, no statistical difference was observed between the hypertensive group and the group with normal blood pressure as regards erythrocyte ATP levels, high-affinity insulin binding sites of EIRs (RT1), and the KD1 of EIRs. 2. In the hypertensive group, the ISI was negatively correlated with mean arterial blood pressure (MBP), a family history of hypertension, the body mass index (BMI), the waist-hip ratio (WHR) and IGF-1 levels (r=-0.614delta, -0.354**, -0.386**, -0.472**, -0.298*, delta p < 0.001, **p < 0.01, *p < 0.05), were positively correlated with RT2 and GH levels (r=0.301**, 0.275*, **p < 0.01, *p < 0.05). There were no statistically significant differences between ISI and age, sex, smoking history, drinking, RT1, KD1, and ATP levels in erythrocytes. 3. The ISI was used as the dependent variable in multiple linear stepwise regression analysis. MBP (X1), a family history of EH (X2), WHR (X3), GH (X4), IGF-1 (X5), RT2 (X6), and the body mass index (X7) was used as independent variables. X1, X2, X3, X5, X6, and X7 were used in the equations. The results indicate that patients with EH also tend to have IR. We suggest that MBP, a family history of hypertension, BMI, WHR, IGF-1, and RT2 might be independent factors affecting IR in cases of essential hypertension.

Adenosine Triphosphate↗
PubMed2000

Newcastle disease virus activates macrophages for anti-tumor activity.

Newcastle Disease Virus (NDV), an agent with interesting immune stimulatory and anti-tumor activity, was investigated for its capacity to activate anti-tumor activity in murine macrophages in vitro and in vivo. Direct macrophage activation was seen under a variety of experimental conditions using two different strains of NDV, different sources of macrophages (spleen and peritoneum) and different strains of mice (DBA/2, C57BL/6, 615). Various macrophage enzymes (ADA, iNOS, lysozyme, acid phosphatase) became upregulated and anti-tumor effector molecules such as nitric oxide (NO) and TNF-alpha were found in the supernatant. NDV activated macrophages performed anti-tumor activity in vitro such as anti-tumor cytostasis and anti-tumor cytotoxicity. The cytotoxic anti-tumor activity was broad and active against all tumor lines tested including mammary carcinoma, lung carcinoma, mastocytoma and immune escape variants (lymphoma). Macrophage activation via BCG/LPS also caused a broad range anti-tumor cytotoxic activity while activation via mixed lymphocyte culture conditioned medium had restricted anti-tumor activity. Anti-tumor activity of NDV activated macrophages could be transfered in vivo. Transfer of macrophages which had not been appropriately activated exerted either no effect or a tumor growth augmenting effect. Repeated intravenous transfer of NDV activated macrophages exerted a significant suppressive effect on pulmonary metastases in a mammary carcinoma tumor model as well as in a lung carcinoma model. Taken together these results demonstrate that NDV can strongly activate macrophages to perform anti-tumor activities in vitro and in vivo.

Animals↗
PubMed2000

[Clinical application of magnetic resonance angiography in the body].

OBJECTIVE: To identify the accuracy and reliability of magnetic resonance angiography (MRA) in evaluating patients with vascular lesions in the body. METHODS: 171 patients with suspected vascular lesions in the body were examined by MRA and compared with the results of X-ray angiography (XRA) or operation. RESULTS: MRA showed abnormal vein in 12 patients and normal in 6 corresponding to XRA or operation. MRA revealed aneurysm in 54 patients: aortic dissection (26), aortic aneurysm (15) and peripheral aneurysm (13). Two peripheral aneurysms could not only be found by MRA. The sensitivity of MRA was 97% for aneurysm lesions. The sensitivity of MRA in the diagnosis of suspicious peripheral artery stenosis in 84 patients was 95%, the specificity 89%, and the accuracy 92% in comparison with those of XRA and operation. CONCLUSION: MRA is accurate and reliable in evaluating vascular lesion in the body and can replace XRA in many cases.

Adolescent↗
PubMed2000

[Expression of lipofect AMINE mediated human GM-CSF eukaryotic expressing vector in HFCL cells].

OBJECTIVE: To construct an eukaryotic expressing vector-pIRES1neo/hGM-CSF and express it in human bone marrow stromal cell line HFCL. METHODS: Human granulocyte/macrophage colony-stimulating factor cDNA (hGM-CSF cDNA, 751 bp) was inserted into an effective eukaryotic expressing vector-pIRES1neo which contains the human cytomegalovirus (CMV) major immediate early promoter/enhancer and the internal ribosome entry site (IRES) of the encephalomyocarditis virus (ECMV). HFCL cells were transfected with the recombinant vector pIRES1neo/hGM-CSF by liposome-mediated gene transfer method. Integration of hGM-CSF in the genome, transcription of its mRNA and expression of its protein in the transfected HFCL cells were assayed by Southern blot, Northern blot, ELISA and hGM-CSF dependent cell line TF-1. RESULTS: hGM-CSF cDNA was integrated into HFCL genome successfully, hGM-CSF mRNA was transcripted and hGM-CSF protein was expressed of (56.9 +/- 0.7) ng/10(6) cells by ELISA and (6.56 +/- 0.16) x 10(3) U/10(6) cells per day by TF-1 cell assay in the supernatant. CONCLUSION: The recombinant vector is proved to be stably expressed in HFCL cells and the biological activity of hGM-CSF was detectable in the supernatant of the transfected cells.

Blotting, Northern↗
PubMed2000

[Experimental studies on the characteristics of suicide gene system HSV-tk/GCV and its effect on dendritic cells].

OBJECTIVE: To study the characteristics of suicide gene system of the herpes simplex virus thymidine kinase (HSV-tk) gene in tumor cells and explore the apoptosis phenomena in this system and its effect on dendritic cells (DC). METHOD: HSV-tk was transduced into the breast cancer cell line MCF-7 cells with a retrovirus vector. Apoptosis was examined by electro-microscopy and FACS. DCs were induced from cord blood CD(34)(+) cells with a combination of cytokines (GM-CSF, TNF-alpha, SCF and FL) and (3)H-TdR was adopted to determine the proliferation of T cells. RESULTS: In vitro experiment showed a dose-dependent cell killing of the HSV-tk gene transducted cells on ganciclovir (GCV) treatment. The apoptosis rate increased to 31.3% from the control group of 19.3%. Apoptosis is the important mechanism in bystander effect of HSV-tk/GCV system. The CD(1a)(+) and HLA-DR(+) cells in the induced DC were of (27.18 +/-1.56)% and (93.7 +/- 1.0)%, respectively. Co-incubation of DC with apoptotic cells further stimulated the proliferation of T cells. CONCLUSION: It suggested that HSV-tk/GCV system, alone or combined with radiotherapy, be a promising suicide gene therapy for cancer patient and an approach to enhancing DC function.

3T3 Cells↗
PubMed1999

Molecular cloning, functional characterization, tissue distribution, and chromosomal localization of a human, small intestinal sodium-phosphate (Na+-Pi) transporter (SLC34A2).

Phosphate plays a crucial role in cellular metabolism, and its homeostatic regulation in intestinal and renal epithelia is critical. Apically expressed sodium-phosphate (Na(+)-P(i)) transporters play a critical role in this regulation. We have isolated a cDNA (HGMW-approved symbol SLC34A2) encoding a novel human small intestinal Na(+)-P(i) transporter. The cDNA is shown to be 4135 bp in length with an open reading frame that predicts a 689-amino-acid polypeptide. The putative protein has 76% homology to mouse intestinal type II Na(+)-P(i) transporter (Na/Pi-IIb) and lower homologies with renal type II Na(+)-P(i) transporters. Northern blots showed a singular transcript of 5.0 kb in human lung, small intestine, and kidney. Computer analysis suggests a protein with 11 transmembrane domains and several potential posttranslational modification sites. Functional characterization in Xenopus laevis oocytes showed that this cDNA encodes a functional Na(+)-P(i) transporter. Furthermore, the gene encoding this cDNA was mapped to human chromosome 4p15.1-p15.3 by the FISH method.

Amino Acid Sequence↗
PubMed1999

Characterization of cis-elements required for osmotic response of rat Na(+)/H(+) exchanger-2 (NHE-2) gene.

The Na(+)/H(+) exchanger (NHE-2) has been implicated in osmoregulation in the kidney, because it transports Na(+) across the cell membrane and efficiently alters intracellular osmolarity. On hyperosmotic stress, NHE-2 mRNA increases in abundance in mouse inner medullary collecting duct (mIMCD-3) cells, suggesting possible transcriptional regulation. To investigate the molecular mechanism of potential transcriptional regulation of NHE-2 by hyperosmolarity, we have functionally characterized the 5'-flanking region of the gene in mIMCD-3 cells. Transient transfection of luciferase reporter gene constructs revealed a novel cis-acting element, which we call OsmoE (osmotic-responsive element, bp -808 to -791, GGGCCAGTTGGCGCTGGG), and a TonE-like element (tonicity-responsive element, bp -1201 to -1189, GCTGGAAAACCGA), which together are shown to be responsible for hyperosmotic induction of the NHE-2 gene. Electrophoretic mobility shift assays suggest that different DNA-protein interactions occur between these two osmotic response elements. However, both DNA sequences were shown to specifically bind nuclear proteins that dramatically increase in abundance under hyperosmotic conditions. Isolation of trans-acting factors and characterization of their specific interaction with these osmotic response elements will further elucidate the transcriptional mechanisms controlling NHE-2 gene expression under hyperosmolar conditions.

Animals↗
PubMed1999

Replacement vectors for localized gene cloning in the specified region of Streptomyces lividans 66 and model method for the screening of desired recombinants via counter-selection.

Two DNA fragments (3.5 kb and 3.8 kb in size) flanking both ends of the phi HAU3R gene in the genome of Streptomyces lividans 66 were determined and cloned in their natural relative orientations in pIJ653, a cosmid vector derived from the multi-copy Streptomyces plasmid pIJ101, resulting in pHZ806. After insertion of spectinomycin/streptomycin (spc/str) resistance gene into the pIJ101 replication region in pHZ806 and insertion of a hygromycin (hyg) resistance gene between 3.5 kb and 3.8 kb DNA fragments, a new vector with a non-functional Streptomyces replicon, pHZ808, was obtained. In principle, any DNA fragment cloned between 3.5 kb and 3.8 kb fragments of this vector can be stably integrated between the two corresponding regions after introduction into the wild-type S.lividans strains, with synchronous replacement of the DNA between the two regions of the chromosome within which phi HAU3R gene is located. The resultant recombinant strains will thus become phi HAU3-sensitive (phi HAU3S). This phenotype could serve as a good indication that the desired gene replacement has occurred. This principle was demonstrated to be successful using pHZ808 as vector. phi HAU3-resistance gene (phi HAU3R) from the genome of S.lividans 66 was substituted by the hygromycin resistance gene (hyg) from pHZ808. An additional advantage of using pHZ808 as the vector to clone foreign genes is that hyg could be served as a reportor gene to imply that foreign DNA fragment has been co-integrated with hyg. The recombinants will have both hygR and phi HAU3S.

Anti-Bacterial Agents↗