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Biomedical subjects

J Han

Publications and source records attributed to J Han.

At least 91 records · Page 5Linked to original sources
PubMed2001

[Effects of air staging with absorbents on trace metal during coal combustion].

Staged combustion was carried out on laboratory-scale pulverized coal combustion with different absorbents. The experiment indicated staged combustion increased emission of submicron particles, which went against the control of trace elements, especially for those of high volatile elements, such as Cu, Ni. The thermodynamics calculation also indicate the transformation of trace metal was different with different atmosphere, suboxidized and reduced species were more easily formed under reduced condition. In both conditions, absorbents show a certain absorptive ability to trace metal, and different absorbent had different ability. For unstaged combustion, kaolinite was the best for Co, Cr and Ni; dolomite for Be, and CaO for Cu. But for under staged condition, HZ- dolomite was the best for Be, Cr and Ni; Kaolinite for Co and Cu.

Absorption↗
PubMed2001

Primary culture of porcine pancreatic acinar cells.

OBJECTIVE: To develop a method for the primary culture of porcine pancreatic acinar cells. INTERVENTIONS: Dispersed pancreatic acinar cells available utilizing RPMI-1640 medium containing collagenase III. After purification, the isolated acinar cells were cultured in RPMI-1640 medium with the addition of 2.5% fetal bovine serum. MAIN OUTCOME MEASURES: The morphological characteristics of acinar cells were described. (3)H-thymidine incorporation of acinar cells and the activity of amylase or lipase were determined during the culture process. RESULTS: There were no remarkable morphological changes in the pancreatic acinar cells during the 20 days culture. The acini showed a tendency to gather but did not attach to the walls of the culture disks. A good (3)H-thymidine incorporation of acinar cells in the primary culture was maintained. The secretion of amylase or lipase from the acini decreased with the length of time of the culture. DISCUSSION: The primary culture of acinar cells from a porcine pancreas which was carried out in this study maintained the normal morphology of the acinar cells and their ability to grow but not their secretion of amylase or lipase. The method would benefit by the further experiments on acini of porcine pancreas.

Animals↗
PubMed2001

[Effects of selective RAR or/and RXR retinoids on the proliferation and differentiation of NB4 cells and their mechanisms].

OBJECTIVE: To investigate the effects of RARbeta selective agonist and RARalpha antagonist (RARbeta +/RARalpha -) BMS453 in combination with RXR selective agonist (RXR+) BMS649 on the proliferation and differentiation of NB4 cells, and illustrate the mechanism. METHODS: The proliferation and differentiation of NB4 cells were detected by cell count, morphological observation, NBT reduction assay, immunofluorescence analysis, flow cytometry and RT-PCR. RESULTS: BMS453 in combination with BMS649 could significantly inhibited the growth of NB4 cell in the manner of dose and time dependence. NB4 cells treated with BMS453 and BMS649 were irreversibly committed to morphologically and functionally more differentiated granulocytic cells. When NB4 cells were treated with BMS453 and BMS649 for 0, 1, 3, 12, 24 and 48 h, RARalpha, RARbeta and RXRalpha expressions were up regulated at 1 h and 3h, respectively. As compared to ATRA, the situations had no significant difference. In contrast, BMS453 or BMS649 alone was ineffective on NB4 cells. CONCLUSION: BMS453 (RARbeta+/RARalpha-) in combination with BMS649 (RXR+) significantly and synergistically inhibit proliferation of NB4 cells and induce them into granulocytic differentiation, the mechanism of which may be mediated by the AF-2 activity of RXR.

Cell Differentiation↗
PubMed2001

[Study of specific targeting cytotoxicity mediated by anti-CD(3)/anti-CD(20) Diabody].

OBJECTIVE: To study the specific targeting cytotoxicity mediated by an anti-CD(3)/anti-CD(20) diabody. METHODS: The diabody was purified by affinity chromatography and identified by Western blot assay, size exclusion chromatography, FACS and rosetting assay; the effect of the anti-CD(3)/anti-CD(20) diabody mediated lysis of CD(20)-expressing tumor cells was assayed by (51)Cr release assay in vitro and by human B cell tumor nude mice xenograft model in vivo. RESULTS: The anti-CD(3)/anti-CD(20) diabody could bind both Jurkat cells (CD(3)(+)) and Daudi cells (CD(20)(+)) and appeared to be potent in targeting activated peripheral blood mononuclear cell (PBMC) to lyse Daudi cells in vitro. Furthermore, it inhibited tumor growth and prolonged the survival of mice bearing xenografted Raji cells. CONCLUSION: The diabody proved to be a potent agent for targeting peripheral blood lymphocytes to lyse CD(20) antigen expressing tumor cells in vitro and in vivo.

Animals↗
PubMed2001

[Percutaneous testicular sperm aspiration and intracytoplasmic sperm injection in the treatment of severe male infertility].

OBJECTIVE: To investigate the efficacy of intracytoplasmic sperm injection (ICSI) combined with percutaneous testicular sperm aspiration (PTSA) in the treatment of severe male infertility. METHODS: From October 1998 to December 2000, 162 couples were enrolled, and ICSI and PTSA were adopted. Ovarian stimulation was achieved by the short protocol. All metaphase II (M II) oocytes were selected for ICSI. RESULTS: 1,517 M II oocytes were injected in 185 cycles, 990 fertilized (65.3%), and 152 embryo implanted. 54 couples achieved clinical pregnancy (35.5%). CONCLUSION: PTSA combined with ICSI is a rapid, convenient, painless and effective approach for the treatment of severe male infertility.

Adult↗
PubMed2001

[Effects of IL-8 on neutrophils under fluid shear].

OBJECTIVE: In order to elucidate the effect of IL-8 on neutrophils in a systematic and all-round way, we introduced an important physiological environment of neutrophils, fluid flow, into this study on the changes in some responses of neutrophils to IL-8 and the inter relationship of those responses under the conditions of different patterns of flow field. METHODS: After using IL-8 and steady flow or sinusoidal-oscillate fluid shear rate simultaneously acting on separated neutrophils for one minute, we measured the expression of CD18, CD62L and the F-actin content with flow cytometry and measured the free calcium concentration inside cells ([Ca2+]i) with the fluorescent stain Fura2/AM using the fluorescent spectrophotometer. RESULTS: It was found that flow shear stress could influence the expression of surface adherence molecule of neutrophils under the action of IL-8. CD18 surface expression increased, and CD62L shed under different flow shear rates, but no significant relationship of these changes with the intensity and pattern of shear stress was noted. On the other hand, the F-actin content in neutrophils under the action of shear stress and IL-8 decreased significantly at low shear rate and then gradually increased at high shear rate (600s -1) to the control value (without shear). The [Ca2+]i concentration under the action of shear stress and IL-8 decreased significantly at low shear rate followed by a quick increase at high shear rate. CONCLUSION: The flow shear stress can influence the activation effects of IL-8 on neutrophils and regulate the magnitude of neutrophil reactions to a great extent, and among these reactions, the change of [Ca2+]i concentration is the most sensitive one and the greatest one. This is in consistence with its second messenger role in the signal transduction pathway. Our results could serve as a basis on which to understand better the mechanism of inflammatory reaction wherein the neutrophils under flow condition of blood are involved.

Actins↗
PubMed2001

[High performance liquid chromatography/electrospray ionization mass spectrometric characterization of recombinant L-asparaginase II].

AIM: To characterize the primary structure of recombinant L-asparaginase II product. METHODS: The molecular weight of the protein was measured by pneumatically-assisted electrospray ionization mass spectrometry with flow injection mode. Subsequently, tryptic peptide mapping was performed by high performance liquid chromatography on a C8 column with tandem UV and MS detection. An easy-to-use and simple denaturation process with trichloroacetic acid was conducted prior to tryptic digest so as to release the digest resistance from the protein structure. The amino acid sequences of the tryptic peptides were elucidated based on their in-source collision-induced dissociation spectra. RESULTS: The measured molecular mass was different from the theoretical value. Three amino acid variations were unambiguously detected along the peptide backbone derived from the gene-encoding sequence. CONCLUSION: This paper revealed that LC/ESI/MS had provided a promising and robust technique in primary structure analysis and quality control of DNA-derived recombinant protein pharmaceuticals.

Amino Acid Sequence↗
PubMed2001

[Growth and osteogenesis characteristics of cultured rat marrow stromal cells under bone induction condition].

OBJECTIVE: To investigate the growth and osteogenesis characteristics of cultured rat marrow stromal cells(rMSCs) under bone induction condition. METHODS: rMSCs were isolated from adult rat using density gradient separation method. The rMSCs attachment formed soon after seeding and grew into colonies with the appearance of fibroblastic cells. The osteogenic induction compound of Dex(10(-8) mol/L), beta-GP(10 mmol/L) and AA(50 micrograms/ml) was added to different passaged rMSCs and the proliferation and osteogenic differentiation of them was observed. RESULTS: The induction compound had strong effect on promoting proliferation, especially on that of further passaged rMSCs, and its stimulation effect on osteogenesis was also well proved with the expression of alkaline phosphatase (ALP) rising after one-week induction. Further subculturing from P1 to P6 led to the increase of proliferation activity of rMSCs. After three-week induction, mineral deposits appeared in the culture. CONCLUSION: The lower expression of ALP in P1 rMSCs and the increase of it in further passages or under induction condition suggest the rMSCs in our culture system are mainly undifferentiated osteoprogenitors.

Alkaline Phosphatase↗
PubMed2000

The p38 pathway provides negative feedback for Ras proliferative signaling.

Ras activates three mitogen-activated protein kinases (MAPKs) including ERK, JNK, and p38. Whereas the essential roles of ERK and JNK in Ras signaling has been established, the contribution of p38 remains unclear. Here we demonstrate that the p38 pathway functions as a negative regulator of Ras proliferative signaling via a feedback mechanism. Oncogenic Ras activated p38 and two p38-activated protein kinases, MAPK-activated protein kinase 2 (MK2) and p38-related/activated protein kinase (PRAK). MK2 and PRAK in turn suppressed Ras-induced gene expression and cell proliferation, whereas two mutant PRAKs, unresponsive to Ras, had little effect. Moreover, the constitutive p38 activator MKK6 also suppressed Ras activity in a p38-dependent manner whereas arsenite, a potent chemical inducer of p38, inhibited proliferation only in a tumor cell line that required Ras activity. MEK was required for Ras stimulation of the p38 pathway. The p38 pathway inhibited Ras activity by blocking activation of JNK, without effect upon ERK, as evidenced by the fact that PRAK-mediated suppression of Ras-induced cell proliferation was reversed by coexpression of JNKK2 or JNK1. These studies thus establish a negative feedback mechanism by which Ras proliferative activity is regulated via signaling integrations of MAPK pathways.

3T3 Cells↗
PubMed2000

Induction of prostaglandin endoperoxide synthase 2 by mitogen-activated protein kinase cascades.

Prostaglandin endoperoxide synthase (PGHS) catalyses the rate-limiting step in the formation of prostaglandin and thromboxane eicosanoids from arachidonic acid released by phospholipase A(2). Two forms of PGHS exist, PGHS-1 and PGHS-2. PGHS-2, normally absent from cells, is rapidly expressed in response to a wide variety of stimuli and has been implicated in the pathogenesis of colon cancer and several inflammatory diseases. The three principal mitogen-activated protein kinase (MAPK) pathways are the extracellular signal-regulated protein kinase (ERK), the c-Jun N-terminal kinase (JNK) cascade and the p38-MAPK cascade. The present study was undertaken to investigate the putative involvement of the MAPK cascades in PGHS-2 induction. The potential role of ERK in PGHS-2 up-regulation was assessed by using cell lines expressing, both stably and after adenoviral infection, constitutively active forms of its upstream activator MAPK/ERK kinase (MEK1). The possible involvement of JNK and p38-MAPK in positively modulating PGHS-2 transcription was investigated by using adenovirus-mediated transfer of active forms of their respective specific upstream kinases, mitogen-activated protein kinase kinase (MKK) 7 and MKK3/MKK6. ERK activation promoted the induction of PGHS-2 mRNA and protein. Similarly, activation of JNK by Ad-MKK7D and p38-MAPK by Ad-MKK3bE/Ad-MKK6bE resulted in the increased expression of PGHS-2. These results provide evidence that activation of all three of the major mammalian MAPK leads to the induction of PGHS-2 mRNA and protein. Because PGHS-2 is up-regulated by a diverse range of stimuli, both mitogenic and stress-evoking, these results provide evidence that the convergence point of these stimuli could be the activation of one or more MAPK cascade(s).

3T3 Cells↗
PubMed2000

Human glioma cell BT325 expresses a proteinase that converts human plasminogen to kringle 1-5-containing fragments.

Angiostatin, a specific angiogenesis inhibitor, is an internal fragment of plasminogen, and can be generated in many systems mediated by different enzymes in vitro. The mechanism of angiostatin generation in vivo has not been well defined. Here we demonstrated that human glioma cell line BT325 can express an enzyme that can convert purified plasminogen to angiostatin-like fragments with molecular masses of 65, 60, and 58 kDa, respectively. These fragments have an identical N-terminal as KVYLS, which starts from Lys(98) of the plasminogen precusor. According to their molecular mass, the three fragments should comprise kringle domain 1 to kringle domain 5 (kringle 1-5). The proteolytic fragments obtained as above can inhibit the growth of bovine aortic endothelial (BAE) cells specifically. The proteolysis process can be completely inhibited by serine proteinase inhibitors, and partially inhibited by EDTA. The molecular weight of the peptide, which contains an enzymatic activity responsible for the proteolysis, was 13 kD determined by gel filtration and SDS-PAGE. The present data suggest that glioma cell BT325 can produce a novel proteinase to generate kringle 1-5 of plasminogen as an angiogenesis inhibitor.

Amino Acid Sequence↗
PubMed2000

Activation of extracellular signal-regulated kinase 1/2 inhibits type I collagen expression by human skin fibroblasts.

Treatment with the lipid second messenger, ceramide, activates extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun N-terminal kinase, and p38 in human skin fibroblasts and induces their collagenase-1 expression (Reunanen, N., Westermarck, J., Häkkinen, L., Holmström, T. H., Elo, I., Eriksson, J. E., and Kähäri, V.-M. (1998) J. Biol. Chem. 273, 5137-5145). Here we show that C(2)-ceramide inhibits expression of type I and III collagen mRNAs in dermal fibroblasts, suppresses proalpha2(I) collagen promoter activity, and reduces stability of type I collagen mRNAs. The down-regulatory effect of C(2)-ceramide on type I collagen mRNA levels was abrogated by protein kinase C inhibitors H7, staurosporine, and Ro-31-8220 and potently inhibited by a combination of MEK1,2 inhibitor PD98059 and p38 inhibitor SB203580. Activation of ERK1/2 by adenovirus-mediated expression of constitutively active MEK1 resulted in marked down-regulation of type I collagen mRNA levels and production in fibroblasts, whereas activation of p38 by constitutively active MAPK kinase-3b and MAPK kinase-6b slightly up-regulated type I collagen expression. These results identify the ERK1/2 signaling cascade as a potent negative regulatory pathway with respect to type I collagen expression in fibroblasts, suggesting that it mediates inhibition of collagen production in response to mitogenic stimulation and transformation.

3T3 Cells↗
PubMed2000

Characterization of active-site residues of the NIa protease from tobacco vein mottling virus.

Nuclear inclusion a (NIa) protease of tobacco vein mottling virus is responsible for the processing of the viral polyprotein into functional proteins. In order to identify the active-site residues of the TVMV NIa protease, the putative active-site residues, His-46, Asp-81 and Cys-151, were mutated individually to generate H46R, H46A, D81E, D81N, C151S, and C151A, and their mutational effects on the proteolytic activities were examined. Proteolytic activity was completely abolished by the mutations of H46R, H46A, D81N, and C151A, suggesting that the three residues are crucial for catalysis. The mutation of D81E decreased kcat marginally by about 4.7-fold and increased Km by about 8-fold, suggesting that the aspartic acid at position 81 is important for substrate binding but can be substituted by glutamate without any significant decrease in catalysis. The replacement of Cys-151 by Ser to mimic the catalytic triad of chymotrypsin-like serine protease resulted in the drastic decrease in kcat by about 1,260-fold. This result might be due to the difference of the active-site geometry between the NIa protease and chymotrypsin. The protease exhibited a bell-shaped pH-dependent profile with a maximum activity approximately at pH 8.3 and with the abrupt changes at the respective pKa values of approximately 6.6 and 9.2, implying the involvement of a histidine residue in catalysis. Taken together, these results demonstrate that the three residues, His-46, Asp-81, and Cys-151, play a crucial role in catalysis of the TVMV NIa protease.

Amino Acid Sequence↗
PubMed2000

The effector loop and prenylation site of R-Ras are involved in the regulation of integrin function.

The closely related small GTP-binding proteins H-Ras and R-Ras have opposing effects on the regulation of integrin cell adhesion receptors. To gain insight into the properties of R-Ras with respect to the regulation of integrin function and interactions with downstream effectors we performed an analysis of R-Ras variants containing mutations in the effector binding domain and C-terminal prenylation site. We found that the activation of the downstream effector PI 3-kinase was sensitive to mutations in the effector binding domain, as was the binding to the effectors, Ral-GDS, Raf-1 and the novel effector Nore1. Furthermore, specific mutations in the effector binding loop and C-terminal prenylation motif impaired the ability of R-Ras to regulate integrin function in CHO cells. However, the ability of the R-Ras effector loop mutants to bind, and activate known effectors did not correlate with their ability to regulate integrin function. Thus, the known R-Ras effectors are not critical for regulating integrin activation, at least in CHO cells. Consequently, these studies provide insight into the structural basis of the interactions between R-Ras and its candidate effectors and suggest the existence of novel mechanisms through which this GTPase could regulate cell adhesion.

Amino Acid Sequence↗
PubMed2000

Formulation and in vivo evaluation of omeprazole buccal adhesive tablet.

For the development of omeprazole buccal adhesive tablets, we studied the release and bioavailability of omeprazole delivered by buccal adhesive tablets composed of sodium alginate, hydroxypropylmethylcellulose (HPMC), magnesium oxide and croscarmellose sodium. Croscarmellose sodium enhanced the release of omeprazole from the tablets. The analysis of the release mechanism showed that croscarmellose sodium changed the release profile of omeprazole from first- to zero-order release kinetics by forming porous channels in the tablet matrix. However, it decreased the bioadhesive forces and stability of omeprazole tablets in human saliva. The tablet is composed of omeprazole-sodium alginate-HPMC-magnesium oxide-croscarmellose sodium (20:24:6:50:10 mg). It may be attached to the human cheek without collapse and it enhanced the stability of omeprazole in human saliva for at least 4 h, giving a fast release of omeprazole. The plasma concentration of omeprazole in hamsters increased to reach a maximum of 370 ng/ml at 45 min after buccal administration and remained at the high level of 146-366 ng/ml for 6 h. The buccal bioavailability of omeprazole in hamsters was 13.7+/-3.2%. These results demonstrate that the omeprazole buccal adhesive tablet would be useful to deliver omeprazole which degrades very rapidly in acidic aqueous medium and undergoes hepatic first-pass metabolism after oral administration.

Adhesiveness↗
PubMed2000

European Task Force on Lymphoma project on lymphocyte predominance Hodgkin disease: histologic and immunohistologic analysis of submitted cases reveals 2 types of Hodgkin disease with a nodular growth pattern and abundant lymphocytes.

Paraffin blocks and clinical data from 521 patients with lymphocyte predominance Hodgkin disease (LPHD) diagnosed between 1970 and 1994 were collected from 16 European and United States oncological centers to establish the pathologic and clinical characteristics of a large patient cohort, to determine how frequent T-cell-rich large B-cell lymphoma (TCRLBCL) is among LPHD, and to find differential diagnostic criteria distinguishing between the 2 lymphoma categories. For this purpose, conventionally and immunohistologically stained sections were reviewed by a panel of hematopathologists. The diagnosis of LPHD was confirmed in only 219 of the 388 assessable cases (56.5%). This low confirmation rate was due mainly to the presence of a new variant of classical Hodgkin disease (CHD), which resembled, in terms of nodular growth and lymphocyte-richness, nodular LPHD and, in terms of the immunophenotype of the tumor cells, CHD and was designated nodular lymphocyte-rich CHD (NLRCHD). The nodules of LRCHD consisted-as in nodular LPHD-predominantly of B cells but differed from those present in LPHD in that they represented expanded mantle zones with atrophic germinal centers. Clinically, patients with LPHD and NLRCHD showed similar disease characteristics at presentation but differed in the frequency of multiple relapses and prognosis after relapse. Patients with LPHD and NLRCHD clearly differed from patients with CHD with nodular sclerosis or mixed cellularity, as they presented with an earlier disease stage and infrequent mediastinal involvement. As 97% of the LPHD cases showed a complete or partial nodular growth pattern, their differentiation from TCRLBCL was a rare problem in the present series. (Blood. 2000;96:1889-1899)

Adolescent↗
PubMed2000

First-principles study of Li-intercalated carbon nanotube ropes

We studied Li-intercalated carbon nanotube ropes by first-principles methods. Results show charge transfer between Li and C and small structural deformation due to intercalation. Both the interior of the nanotube and the interstitial space are susceptible for intercalation. The Li intercalation potential of a single-walled nanotube rope is comparable to that of graphite and almost independent of the Li density up to around LiC2, as observed in recent experiments. This density is significantly higher than that of Li-intercalated graphite, making the nanorope a promising candidate for the anode material in battery applications.

Journal Article↗