The electrochemical and spectroelectrochemical behaviors of SOD at cysteine modified gold electrode

Different promoters were used to enhance the rate of the electron transfer process of superoxide dismutase (SOD). A quasi-reversible cyclic voltammogram (CV) of SOD was observed on the cysteine-modified gold wire electrode. The coupled adsorption/desorption processes and the characteristic Raman spectra of different states of SOD molecules on the electrode surface were studied with electrochemical quartz crystal microbalance (EQCM) and in-situ Raman spectroelectrochemical techniques. The possible promotion mechanism was discussed.

Determination of menadione sodium bisulfite in pharmaceutical preparations by flow-injection on-line photochemical spectrofluorometry

A flow-injection on-line photochemical spectrofluorometry (FI-PF) was developed for the determination of menadione sodium bisulfite (MSB) using acetone and sodium sulfite as sensitizing reagents. An injected sample band carried by a water stream was on-line merged with a mixed NaOH, Na2SO3 and acetone solution in a "T" connector. It was then driven to pass a knotted PTFE photochemical reactor (0.5 mm i.d. x 200 cm, KR) that was freely coiled around a 6-W low-pressure mercury lamp. While passing the KR, MSB was derived into an intensively fluorescent compound that was on-line delivered into a flow-through cell and detected therein at an emission wavelength of 459 nm and an excitation wavelength of 336 nm. Under optimized conditions a detection limit of 0.38 microg l(-1) was achieved at a sampling rate of 90 h(-1). Eleven determinations of 0.5 mg l(-1) and 0.05 mg l(-1) MSB standard solution gave RSDs of 0.75% and 1.3%, respectively. The calibration curve was linear in the MSB concentration range 0.005-1.5 mg l(-1). The proposed method was successfully applied to assay the MSB content in MSB injection.

Dendritic cells support hematopoiesis of bone marrow cells

BACKGROUND

We previously observed that vaccination of normal mice with bone marrow (BM) -derived dendritic cells (DCs) could increase the number of peripheral white blood cells (WBCs) and platelets. In the present study, we investigated the potential of DCs to support the hematopoiesis of BM cells in vitro and in vivo.

METHODS

In the absence of exogenous cytokines, the expansion of CD34+ stem cells was observed when cultured with DC-derived supernatant or contact cocultured with DC. After culture in supernatant of DCs or contact coculture with DCs for 3 days, CD34+ progenitor cells were cultured in the semisolid media to test their ability to generate the clonogeneic cells. Then, BM cells combined with DCs or not were transferred into lethally irradiated syngeneic recipients to determine the effects of DCs on hematopoietic recovery.

RESULTS

After culture in the supernatant of DCs, especially in the supernatant of OVA-DCs (OVA-stimulated DC), the proliferation of CD34+ stem cells and generation of clonogeneic cells were augmented in correspondence with the concentration of DCs. After contact coculture with DCs, the proliferation of CD34+ stem cells and generation of clonogeneic cells were more significant than that in noncontact cultures. Moreover, when cultured with DCs or supernatant of DCs, CD34+ progenitor cells were preferentially differentiated to megakaryocytes. After coculture with OVA-DCs, markedly greater generation of colony forming units-granulocyte/macrophages (CFU-GM): colony forming units-megakaryocytes (CFU-MK) was found than that in coculture with unstimulated DCs. Pretreatment of DC with antibodies to thrombopoietin (TPO), interleukin (IL) -6, IL-12, or anti-mouse intercellular adhesion molecule-1 (ICAM-1) could inhibit the ability of DCs to support the generation of CFU-GM, CFU-MK. After transplant with BM cells and DCs, the number of peripheral platelets of the recipients increased significantly and, to a lesser extent, peripheral WBC counts increased. The survival periods were significantly prolonged when the lethally irradiated mice were transplanted with BM cells combined with DCs or OVA-DCs. High levels of TPO, IL-6, and IL-12 could be detectable in the supernatant of DCs, and TPO expression by DCs was further confirmed by reverse transcription-polymerase chain reaction analysis and intracellular staining with anti-TPO antibody.

CONCLUSIONS

We first demonstrated that DCs, especially antigen-stimulated DCs, can promote the expansion of hematopoietic progenitors and support hematopoiesis, preferentially support megakaryopoiesis of BM cells, by expressing soluble factors, including TPO, IL-6, IL-12, and by direct cell-to-cell interaction with stem cells in vitro and in vivo.

DIgR1, a novel membrane receptor of the immunoglobulin gene superfamily, is preferentially expressed by antigen-presenting cells

A novel membrane receptor of immunoglobulin gene superfamily (IgSF) has been identified from mouse dendritic cells (DC) and designated as DC-derived Ig-like receptor 1 (DIgR1). It encodes a 228-amino-acid (aa) residue polypeptide with a 21-aa signal peptide, a 20-aa transmembrane region, a 189-aa extracellular region, and a 19 aa intracellular region. Its extracellular region contains a single V domain of Ig. So it is a novel type I transmembrane glycoprotein of IgSF. DIgR1 shows significant homologies to human CMRF-35 antigens and polymeric immunoglobulin receptors (pIgR). The mRNA expression of DIgR1 was highly abundant in mouse spleen. The preferential expression of DIgR1 mRNA is observed in the known antigen-presenting cells (APC) including DC, monocytes/macrophages, and B lymphocytes. A 40 kDa of protein in NIH/3T3 cells transfected with the DIgR1 cDNA was detected by Western blot analysis using anti-DIgR1 polyclonal antibodies. The expression of DIgR1 protein on DC is not regulated by LPS stimulation. Further study should be conducted to investigate what were biological functions of DIgR1 in the immunobiology of APC.

Dysfunction of microvascular endothelial cells induced by tumor necrosis factor (TNFalpha): cellular and molecular mechanism

The dysfunction of rat pulmonary microvascular endothelial cells (RPMVEC) induced by tumor necrosis factor alpha (TNFalpha) was investigated in cell culture. The TNFalpha concentrations added into culture were 1000-5000 u/ml. The study was done at different steps as follows: (1) cell proliferation dynamic, (2) coagulation and anti-coagulation, (3) adhesive molecule, (4) nitric oxide (NO), (5) oncogens, and (6) apoptosis. It was concluded that attention should be paid to the metabolic disorder and dysfunction of RPMVEC induced by TNFalpha which can not be found easily according to the morphological changes. This might be the common pathway in the pathogenesis of some diseases related to TNFalpha.

Intrasplenic transplantation of IL-18 gene-modified hepatocytes: an effective approach to reverse hepatic fibrosis in schistosomiasis through induction of dominant Th1 response

Hepatic fibrosis is a common outcome of chronic liver diseases. In schistosomiasis, chronic parasite egg-induced granuloma formation can lead to fibrosis, which is immunologically characterized by the dominant Th2 response. Recently, it has been shown that gene therapy is an attractive approach for the treatment of hepatic fibrosis. To investigate the antifibrotic effects of IL-18 gene transfer, a normal murine liver cell line BNL.CL2 was transfected with recombinant adenovirus encoding mouse IL-18, and then intrasplenically transplanted into mice infected with Schistosoma japonicum (S. japonicum). Our data show that IL-18 gene-modified hepatocytes intrasplenically transplanted into mice can effectively express IL-18 in the liver and in peripheral blood. Intrasplenic transplantation of IL-18 gene-modified hepatocytes into S. japonicum-infected mice could result in a significantly increased IFN-gamma and IL-2 but decreased IL-4 and IL-10 concentration both in the liver and in the serum, suggesting that the dominant Th2 response in mice with schistosomiasis could be reversed by this intervention. Consistent with the changes in Th1 and Th2 cytokine production, mice intrasplenically transplanted with IL-18 gene-modified hepatocytes developed much less hepatic fibrosis at 20 weeks after infection, which was evaluated by liver content of hydroxyproline, collagens, and hepatic mRNA expression of procollagens. These data indicate that intrasplenic transplantation of IL-18 gene-modified hepatocytes can be a candidate for therapeutic intervention in hepatic fibrosis through induction of a dominant Th1 response.

[Automatic analysis and research on the trend of ST-T segment based on KL transform]

In view of the limitation of monitoring the trend of ST segment with the traditional method(ST level), we introduce a new monitor method based on KL transform. This method has overcome many disadvantages of ST level, e.g. the susceptibility to interference, a large variation of performance and the reflection of isolated characteristic. This method can characterize the signals stably and adequately. We have made experiment and analyzed the property of this method by using the standard database. The results indicate that the KL transform is of great clinical significance in detecting and monitoring the abnormality of the ST-T segment waveform over a long period of time, and the effect of monitor is also laid on the selection of KL series.

[Immunological mechanism of human alpha-interferon gene therapy for treatment of melonoma]

OBJECTIVE

To investigate the possibility of alpha-INF gene therapy for treatment of melonoma.

METHODS

An experimental model of fibroblast-mediated human alpha-IFN gene therapy was established for treatment of melonoma and the activity of NK and M phi was determined.

RESULTS

The NK and M phi activity was increasing significantly after the implantation of alpha-IFN secreted by cloning the fibroblast in vivo. Good therapeutic results could be achived if the NIH3T3-IFN-alpha+ cells were combined with the IL-2/AK.

CONCLUSION

The results has indicated that the fibroblast-mediated gene therapy could be good to use it for the treatment of human melonoma. More effective results could be achieved by using it in combination with IL-2.

Enhancement of antigen-presenting ability of B lymphoma cells by immunostimulatory CpG-oligonucleotides and anti-CD40 antibody

Immunostimulatory oligodeoxynucleotides containing the CpG motifs (CpG-ODN) can activate antigen-presenting cells including dendritic cells, macrophages, B cells, and enhance production of Thl cytokines. So, CpG-ODN has been regarded as a promising immune adjuvant. Using the A20 B lymphoma cell model, we investigated the effect of CpG-ODN on the immunogenicity of B lymphoma cells and whether CpG-ODN could enhance the antigen-presenting ability of B lymphoma cells. After incubation with CpG-ODN, proliferation of A20 cells remained unchanged. But CpG-ODN stimulation up-regulated the expression of MHC-I, MHC-II, CD40, ICAM-1 molecules in A20 cells, enhanced the antigen uptake ability of A20 cells, and promoted A20 cell production of IgM and IgG. More importantly, A20 cells activated by CpG-ODN could stimulate allogeneic T cells in MLR and antigen-primed T cells to proliferate more efficiently, suggesting the antigen-presenting ability of A20 B lymphoma cells could be enhanced by CpG-ODN stimulation and CpG-ODN-activated B lymphoma cells might be used as a potent cellular vaccine. Although anti-CD40 mAb was as effective as CpG-ODN at activating A20 cells and A20 cells expressed more CD40 molecules after CpG-ODN stimulation, a combination of CpG-ODN and anti-CD40 mAb had no synergistic effect on A20 cell activation. Our data expanded the potential application of CpG-ODN as an immunotherapeutic agent in cancer treatment.

Significant augmentation of pro-apoptotic gene therapy by pharmacologic bcl-xl down-regulation in mesothelioma

The ratio of pro-apoptotic (PAP) and anti-apoptotic (AAP) bcl-2 proteins is important in apoptosis regulation. We sought to determine if inhibition of the AAP bcl-xl by sodium butyrate (SB) would augment apoptotic cellular death in mesothelioma when combined with adenoviral pro-apoptotic gene therapy (PAGT) by simultaneously increasing PAP and decreasing AAP in these cells. Human mesothelioma cell lines were exposed to AdBax, AdBak, Adp53, and SB alone as well as all vectors combined with SB at varying doses and time points. Cell death was assessed, and apoptosis evaluated by morphology and FACS. Isobologram analysis evaluated additive or synergistic effect. Cellular death and apoptosis were augmented by PAGT/SB combinations compared to monotherapy. Following AdBax/SB and AdBak/SB, a decrease of the AAP bcl-xl was noted in combination with increases in PAP bax and bak. By isobologram analysis, additive or synergistic cell killing was noted with both combinations. SB treatment did not significantly augment cell killing or apoptosis in combination with Adp53. PAGT/SB was more effective than monotherapy in induction of apoptotic cell death. Synergy may be due to the ability of SB to decrease bcl-xl with marked increases in PAP engendered by PAGT. Combination therapy with agents that down-regulate AAP in addition to PAGT may prove useful clinically.

[Raman spectra of Cu/Zn superoxide dismutase and L-cysteine used as an electron transfer promoter]

In author's laboratory, it has been demonstrated with electrochemical techniques that L-cysteine can be used as an effective electron transfer promoter to accelerate the electron transfer process of Cu/Zn superoxide dismutase on gold electrode. In order to reveal the mechanism of this promotion, confocal microscopic Raman spectroscopic technique is employed here to obtain Raman spectra of solid state SOD and L-cysteine modified gold electrode. Moreover, Raman spectra of L-cysteine modified gold electrode with two different approaches are also obtained. Analysis and discussion for these Raman spectra are reported.

Effects of redox potential and pH value on the release of rare earth elements from soil

Equilibrium release experiments were conducted under three different pH values of 3.5, 5.5 and 7.5 as well as three redox potentials of 400, 0 and -100 Mv to investigate the influence of redox potential and pH value on the La, Ce, Gd and Y release of from the simulated-REEs-accumulation (SRA) soil. Oxygen and nitrogen were allowed to flow into soil suspension to adjust redox potential to a preset value, and 1 mol/l HCl or 1 mol/l NaOH solutions were added into the soil suspension to keep pH at a preset value. Results indicated that La, Ce, Gd and Y release increased gradually with the decrease of pH value or Eh, and the influence of redox potential on Ce was more remarkable than on La, Gd and Y. At the same time. It was observed that La, Ce, Gd and Y releases were positively correlated with the release of Fe and Mn, indicating that La, Ce, Gd and Y releases might originate from dissolution of Fe-Mn oxyhydroxides under reduction and low pH conditions. Moreover, it was found that alteration of pH value and redox potential might affect the change of La, Ce, Gd and Y species in the soil. The contents of La, Ce, Gd and Y in exchangeable fraction and Fe-Mn oxide fraction in the solid phase from soil suspension separation decreased with the decline of pH value and redox potential. Multiple stepwise regression analysis showed that exchangeable fraction and Fe-Mn oxide fraction predominately contributed to the La, Ce, Gd and Y release. Low pH value and redox potential were more favorable to La, Ce, Gd and Y releases following the change of their species. The La, Ce, Gd and Y contents in exchangeable fraction and Fe-Mn oxide fraction are the main contributors to their release.

Development and certification of a coal fly ash certified reference material for selected polycyclic aromatic hydrocarbons

The development and certification of a coal fly ash certified reference material (CRM) for polycyclic aromatic hydrocarbons (PAH) is described; this is the first natural matrix CRM for organic environmental analysis in China. The homogeneity and stability of this material have been tested by HPLC. The concentrations of several PAH were determined by use of two independent, different methods--solvent extraction-HPLC analysis with UV detection coupled with fluorescence detection (FLD) and solvent extraction, isolation with a silica column, and GC analysis with flame ionization detection (FID). Five certified values were determined: phenanthrene 7.1 +/- 2.6 microg g(-1), anthracene 2.0 +/- 0.8 microg g(-1), fluoranthene 7.4 +/- 1.9 microg g(-1), pyrene 7 +/- 2 microg g(-1), and benzo[a]pyrene 1.3 +/- 0.3 microg g(-1). Reference values for several other PAH are also suggested.

Molecular cloning and characterization of a novel calcium/calmodulin-dependent protein kinase II inhibitor from human dendritic cells

Calcium/calmodulin-dependent protein kinase II (CaMKII) is a widely distributed protein kinase that regulates numerous physiological functions. Inhibitors of CaMKII are useful tools for investigating the CaMKII functions. Here we identified a novel CaMKII inhibitor protein (CaM-KIIN) from the human dendritic cell cDNA library by large-scale random sequencing. Human CaM-KIIN contains 79 amino acids, which shares 98% identity and 98% positives with rat CaMKII inhibitor protein beta and 65% identity and 78% positives with rat CaMKII inhibitor alpha. Human CaM-KIIN mRNA expression was detectable in various tissues and cell lines by Northern blot and RT-PCR. To investigate its biological functions, full-length human CaM-KIIN was overexpressed in colon adenocarcinoma LoVo cells. When expressed in LoVo cells, it could inhibit cell proliferation, block cell growth, and decrease the viable cell number. These results characterize a potential cellular inhibitor protein of CaMKII that plays an important role in the regulation of cell growth.

[Treatment of spontaneous metastatic lung cancer with tumor antigen-pulsed, interleukin-18 gene-modified dendritic cells]

OBJECTIVE

To investigate the effect of tumor antigen-pulsed, interleukin-18 (IL-18) gene-modified dendritic cells in treatment of spontaneous metastatic lung cancer.

METHODS

3LL Lewis lung cancer cells were injected into the footpads of C57BL/6 mice to establish a spontaneous metastatic lung cancer model. Ninety-six mice with lung cancer were divided into 8 groups, 12 in each. treated differently. One group was treated by subcutaneous vaccination for two times of tumor antigen peptide Mut1-pulsed, IL-18 gene-modified dendritic cells (DC-IL-18/Mut1) that were derived from normal bone marrow. The other groups were treated with other measures. After treatment, the lung weight, number of metastatic nodes on the lung surface, survival time, and NK and CTL activities were examined.

RESULTS

Compared with the mice treated with Mut1-pulsed control LacZ gene-modified DC and those treated with untreated DC, the tumor-bearing mice treated with DC-IL-18/Mut1 had the lightest lung weight (215 mg +/- 20 mg Vs 398 mg +/- 23 mg and 987 mg +/- 45 mg, t = 14.7 and 38.4, P < 0.01), the least lung metastatic nodes (0 Vs 7.8 +/- 2.7 and 49, P < 0.01), the longest survival time (chi(2) = 6.78 and 10.49 respectively, P < 0.01), the strongest cytotoxic T cell activity (53.4 +/- 3.1 Vs 41.3 +/- 2.6 and 9.8 +/- 2.1, t = 13.4 and 15, 7 respectively, P < 0.01), and increased proportions of CD4 + Tcells, CD8 + Tcells, and NK cells.

CONCLUSION

Tumor antigen-pulsed, IL-18 gene-modified dendritic cells have a significant therapeutic effect on spontaneous netastatic lung cancer through induction of anti-tumor immunological responses.

A transcriptionally [correction of transcriptively] active complex of APP with Fe65 and histone acetyltransferase Tip60

Amyloid-beta precursor protein (APP), a widely expressed cell-surface protein, is cleaved in the transmembrane region by gamma-secretase. gamma-Cleavage of APP produces the extracellular amyloid beta-peptide of Alzheimer's disease and releases an intracellular tail fragment of unknown physiological function. We now demonstrate that the cytoplasmic tail of APP forms a multimeric complex with the nuclear adaptor protein Fe65 and the histone acetyltransferase Tip60. This complex potently stimulates transcription via heterologous Gal4- or LexA-DNA binding domains, suggesting that release of the cytoplasmic tail of APP by gamma-cleavage may function in gene expression.

Effect of contact time and inhibitor concentration on the affinity mediated adsorption of cells to surfaces

Cell detachment by shear stress under conditions of laminar flow was used to investigate the effect of incubation time and soluble binding competitors on affinity mediated cell/surface interactions. Fractional attachment between yeast and a Concanavalin A (Con A) coated surface was studied as a function of adhesion time prior to exposure to shear in a parallel plate flow chamber. Two, four and sixteen hours adhesion times gave rise to significantly different fractional attachment profiles, with four hours giving greater cell retention.The effect of dextran as a competitive displacer of pre-attached cells was also examined using a number of exposure regimes. While the presence of dextran in the displacement buffer led to higher fractional displacement of pre-attached cells, this effect was magnified if an equilibration period between dextran solution and pre-attached cells was allowed before detachment was attempted. The decline in fractional attachment increased with incubation time up to 30 min, with longer periods resulting in a smaller effect. Pre-incubation of the Con A surface with dextran prior to the introduction of cells led to a 60% reduction in attachment.Attempts to determine critical shear values were complicated by the presence of a tightly bound cell fraction of approximately 15% that was not removed at the highest shear values used.

Cloning and Characterization of Siglec-10, a Novel Sialic Acid Binding Member of the Ig Superfamily, from Human Dendritic Cells

The Siglecs (sialic acid-binding Ig-like lectins) are a subfamily of I-type lectins, which specifically recognize sialic acids. Nine members of the family have been identified thus far. We have obtained a novel cDNA clone from a human dendritic cell cDNA library encoding a protein with sequence and structural features of the Siglec family, hence designated as Siglec-10. The full-length Siglec-10 cDNA encodes a type 1 transmembrane protein containing four extracellular immunoglobulin-like domains, a transmembrane region, and a cytoplasmic tail with two classical immunoreceptor tyrosine-based inhibitory motifs. The N-terminal V-set Ig domain has most of the amino acid residues typical of the Siglecs. Siglec-10 shows the closest homology to Siglec-5 and Siglec-3/CD33. Various cells and cell lines including monocytes and dendritic cells express Siglec-10. High levels of mRNA expression were seen in peripheral blood leukocytes, spleen, and liver. When expressed on COS-7 cells, Siglec-10 was able to bind human red blood cells and soluble sialoglycoconjugates in a sialic acid-dependent manner. The identification of Siglec-10 as a new Siglec family member and its expression profile, together with its sialic acid-dependent binding capacity, suggest that it may be involved in cell-cell recognition by interacting with sialylated ligands expressed on specific cell populations.

Protein kinase C epsilon-Src modules direct signal transduction in nitric oxide-induced cardioprotection: complex formation as a means for cardioprotective signaling

An essential role for protein kinase C epsilon (PKCepsilon) has been shown in multiple forms of cardioprotection; however, there is a distinct paucity of information concerning the signaling architecture that is responsible for the manifestation of a protective phenotype. We and others have recently shown that signal transduction may proceed via the formation of signaling complexes (Circ Res. 2001;88:59-62). In order to understand if the assembly of multiprotein complexes is the manner by which signaling is conducted in cardioprotection, we designed a series of experiments to characterize the associations of Src tyrosine kinase with PKCepsilon in a conscious rabbit model of nitric oxide (NO)-induced late preconditioning. Our data demonstrate that PKCepsilon and Src can form functional signaling modules in vitro: PKCepsilon interacts with Src; the association with PKCepsilon activates Src; and adult cardiac cells receiving recombinant adenoviruses encoding PKCepsilon exhibit increased Src activity. Furthermore, our results show that NO-induced late preconditioning involved PKCepsilon-Src module formation and enhanced the enzymatic activity of PKCepsilon-associated Src. Inhibition of PKC blocked cardioprotection, module formation, and PKCepsilon-associated Src activity, providing direct evidence for a functional role of the PKCepsilon-Src module in the orchestration of NO-induced cardioprotection in conscious rabbits.

Defining the concentration gradient of nerve growth factor for guided neurite outgrowth

The developing axon is believed to navigate towards its target tissue in response to a concentration gradient of neurotrophic factors, among other diffusible and surface-bound stimuli. However, the minimum concentration gradient required for guidance over the maximum distance is still unknown, largely because well-defined systems have not been utilized to address this question. In this study, a linear concentration gradient of nerve growth factor was achieved across a 5-mm agarose membrane that separated a nerve growth factor source compartment from a sink compartment. The concentrations in both compartments were maintained constant (and different). Both concentration and concentration gradient were well defined across the membrane, allowing us to study the relative importance of concentration gradient vs concentration for neurite guidance. The orientation of PC12 cell neurites was studied in response to a series of nerve growth factor concentration gradients in vitro. For effective guidance of PC12 cell neurite outgrowth, a minimum concentration gradient of 133ng/ml per mm was required, below which guidance was ineffective. Higher gradients were effective for guidance yet were limited by the concentration of nerve growth factor in the source compartment. At a nerve growth factor concentration of 995ng/ml, the PC12 cells' receptors were saturated, thereby limiting the maximum effective distance for guidance to less than 7.5mm in response to a diffusible nerve growth factor cue. This distance exceeds the 0.5-2mm distance observed by others for effective neurite guidance. Using this model system, we propose that the minimum concentration gradient can be defined for other cells and growth factors. Ultimately, it is anticipated that such concentration gradients could be included in a device to promote regeneration.

Regulation of Stat3 activation by MEK kinase 1

Stat3 is a latent transcription factor activated by various cytokines and growth factors. Phosphorylation on Tyr-705 is a prerequisite for dimer formation, nuclear translocation, binding to its cognate DNA sequences, and regulation of the target gene transcription. Ser-727 phosphorylation of Stat3 plays an additional role in the regulation of transcription. MEK kinase 1 (MEKK1) is a mitogen-activated protein kinase (MAPK) kinase kinase (MAPKKK) that activates the c-Jun NH(2)-terminal kinase signaling pathway. Here we report that MEKK1 is involved in the regulation of Stat3 activation by growth factors. Kinase-inactive MEKK1 inhibits Stat3 phosphorylation on tyrosine and serine, and its transcriptional activity stimulated by epidermal growth factor and platelet-derived growth factor in different cell types. In contrast, active MEKK1 induces Stat3 tyrosine and serine phosphorylation leading to a functionally active Stat3 capable of binding DNA and enhancing transcription. Ser-727 is phosphorylated by MEKK1 in vitro, whereas Tyr-705 phosphorylation induced by MEKK1 involves Src and Janus kinases in vivo. These data demonstrate for the first time a novel role of MEKK1 to modulate tyrosine kinases that results in the activation of specific members of STAT family.

Identification and characterization of DPZF, a novel human BTB/POZ zinc finger protein sharing homology to BCL-6

The C2H2 zinc finger protein family is one of the largest families of transcription factors. We identified a novel BTB/POZ zinc finger gene from human dendritic cells (DC), which encodes a 733-residue protein with a BTB/POZ domain at the N-terminal and 4 C2H2 zinc fingers at C-terminal. It was designated dendritic cell-derived BTB/POZ zinc finger (DPZF). DPZF protein shares closest homology to BCL-6, with the highest homology present in the BTB/POZ and zinc finger domains. Like BCL-6, DPZF gene is localized on chromosome 3. It is widely expressed in hematopoietic tissues, including DC, monocytes, B cells, and T cells. DPZF protein expression is detectable in lymphoid neoplasm with a molecular mass of 100 kD, especially in B lymphoma. These indicate that DPZF may be a transcription factor closely related to BCL-6, and may be involved in hematopoiesis, oncogenesis, and immune responses.

[Color reaction of chromogenic reagent O-hydroxybenzenediazoaminoazobenzene with thallium (III) and its application]

The chromogenic reaction of the O-hydroxybenzenediazoaminoazobenzene (O-HDAA) with thallium was studied in this paper. In the presence of Triton X-100 and SDBS and in ammonia medium of 0.54-1.1 mol.L-1, O-HDAA reacts with thallium (III) to form a stable red complex with molar radio of 1:5. The apparent molar absorptivity is 1.4 x 10(5) L.mol-1.cm-1 at the maximum absorption wavelength of 520 nm. Beer's law is obeyed in the concentration range of 0-600 micrograms.L-1 Tl(III). The method has been applied to the direct determination of trace amounts of thallium in waste water and in geological samples by using polyurethane foam to absorb and separate Tl(III) with satisfactory results.

Effects of acute or prolonged exposure to leptin on hepatic glucose oxidation

OBJECTIVE

To observe the short-term and long-term effects of leptin on hepatic glucose oxidation and glucokinase gene expression.

METHODS

Rat hepatic cell line BRL was incubated with leptin of different doses (range from 10 ng/ml-200 ng/ml) for 1 h or 24 h. Glucose oxidation was determined by liquid scintillation counting. Glucokinase gene expression (corrected by beta-actin) was determined by reverse transcription semi-quantitative polymerase chain reaction.

RESULTS

Treatment with leptin 10 ng/ml for 1 h had no significant effects on glucose oxidation in hepatic cells. However, at the doses ranging from 50 ng/ml to 200 ng/ml, leptin significantly inhibited glucose oxidation. These effects disappeared when the hepatic cells were exposed to leptin for 24 h. Glucokinase mRNA expression was reduced significantly after both 1 h and 24 h exposure to leptin (100 ng/ml) as compared to that of the control group.

CONCLUSION

A low dose of leptin has no significant effect on glucose oxidation in hepatic cells. A relatively high dose of leptin has an acute inhibitory effect on the glucose oxidation in hepatic cells. This effect may likely involve the inhibition of glucokinase gene expression. The inhibitory effect on glucose oxidation is transient and disappears with prolonged exposure time.