Biomedical subjects

B Gong

Publications and source records attributed to B Gong.

At least 37 records · Page 2Linked to original sources

PubMed1999

Surface composition of silica particles embedded in an Australian bituminous coal.

The composition and structure of the surface layers of a series of silica particles (10-20 microns across), embedded in a bituminous coal from the Whybrow seam, Sydney Basin, Australia, have been characterized in situ using time-of-flight secondary ion mass spectrometry (TOFSIMS), ion imaging, and depth profiling. The silica particles investigated are typically encased in a multilayered shell, the composition of which differs from average composition of both the silica and the bulk coal. The analysis directly demonstrates the presence of a silanol-rich (Si-OH) interfacial layer 3 nm in thickness. This silanol-rich region separates the bulk silica and a complex non-silica layer encasing the particles. The interfacial region also shows significant lithium enrichment (approximately fivefold over bulk) which implies diffusion and precipitation of lithium-containing species during the authigenetic formation of the surface layers of the silica grains. The outer layer encasing the silica particles is 10 nm in thickness and is composed of clays and carbonates, and, in some cases, includes organic material. The elemental constituents of this layer include aluminium, sodium, potassium, magnesium, iron, and lesser amounts of titanium and copper. The variation in the aluminium concentration from the outermost surface to the deeper layers is less than that of other non-silica species. A relatively high amount of calcium is found associated with the silica bulk. Although only non-respirable-sized silica particles are examined in this work, the methods of analysis developed have potential in providing an insight into the surface composition of respirable particles and in further studies of the surface bioavailability of silica species.

Air Pollutants, Occupational↗

PubMed1999

DNA sequence recognition by a novel series of minor groove-binding ligands.

We have used quantitative DNase I and hydroxyl radical footprinting with three DNA fragments to examine the sequence-specific recognition of DNA by five novel minor groove-binding ligands which contain a structural motif in which a para-disubstituted benzene ring is flanked by two meta-disubstituted benzene rings. The compounds are all AT-selective and bind better to (AT)6 than (AT)4 sites. The ligands bind more tightly to AATT and TAAT than TTAA, TATA and ATAT, and avoid sequences containing central TpA steps. Different side groups cause subtle changes to the sequence recognition properties of these ligands.

Adenine↗

PubMed1999

Differential upregulation of p53-responsive genes by genotoxic stress in hematopoietic cells containing wild-type and mutant p53.

Cells respond to genotoxic stress by activation of many genes, including the tumor suppressor p53. p53 activates transcriptionally target genes, such as p21waf1 and gadd45, which can lead to cell cycle arrest, or bax, which can lead to cell death. We examined the response to genotoxic stress in two hematopoietic cell lines that harbor either wild-type (MOLT-4) or a mutant p53 with a codon 161 mutation (U266). We adapted a multiprobe RNase protection assay (RPA) to determine the steady-state RNA levels, and in combination with nuclear runoff assays, transcriptional rates of multiple stress-induced genes. We found a differential activation of growth arrest and cell death-specific p53 target genes in cells with wild-type or mutant p53. Our results show that genotoxic stress can activate the p21waf1 and gadd45 genes in both cell lines. However, the bax gene was not induced in U266 cells. Bax and gadd45 gene induction could be efficiently blocked by pretreating the cells with the antioxidant compound pyrrolidine dithiocarbamate, suggesting that oxidative stress was involved in these responses. Induction of all three genes in MOLT-4 cells was clearly at the transcriptional level, because we detected transcriptional activity by nuclear runoff RPA assays, and transfection with a consensus p53 binding sequence. U266 cells did not activate the same reporter, in spite of the upregulation of p21waf1 and gadd45 RNA levels. However, the p21waf1-reporter constructs containing 0.9 to 2.4 kb of the native p21 promoter were potently activated in U266 cells. These results indicate a differential regulation of p53 target genes in cells containing wild-type or codon 161 mutant p53.

Apoptosis↗

PubMed1999

[Clinical application of expandable metal stent for palliation of malignant biliary obstruction].

OBJECTIVE: To investigated the long-term result of expandable metallic biliary stent implantation and evaluated preliminarily the factors that might impact the therapeutic effectiveness. METHODS: 134 patients with malignant choledochal stenosis were treated with metallic endo-prosthesis (128 transpapillary endoscopically and 6 transhepatic percutaneously). The follow-up results were compared with those of 97 patients with conventional plastic stents during the same period. RESULTS: The success rate was 95.7%, and the procedure related complications were found in 6.4% of patients. The jaundice was eliminated completely in 85.6% patients. During long-term follow-up, the metal stents were shown patent for a mean duration of 300 days, which was significantly longer than 80 days of polyethylene endoprostheses (P < 0.01). The mean survival was 210 days. From classified data assessment, the stent patency in primary bile duct neoplasm group was almost similar to that in metastatic group, but the median survival of the former was slightly longer than that of the latter. There were flow differences in patancy and survival rates between the hilar obstruction group and the middle and low obstruction group. CONCLUSIONS: The median patancy of expandable metal stents was significantly longer than that of conventional plastic prostheses. To get the highest benefit, however, the indication should be strictly selected.

Adult↗

PubMed1999

[Fluorescence quenching method for the determination of trace zirconium with 5'-nitor-salicylfluorone and hexadecyltrimethylammonium bromide].

A new fluorometric method has been developed for the determination of trace zirconium, based on the fluorescence quenching effect of Zr (IV)-5'-nitro-salicylfluorone (5'-N-SAF)-hexadecyltrimethylammonium bromide (CTMAB). In the H2SO4 medium and in the presence of CTMAB Zr (IV) reacts on 5'-N-SAF to form a 14 orange complex. Its maximum excitation wavelengths are 475 and 505 nm,and the maximum emission wavelength is 525 nm. The linear range is 2.0-80 microg/L, and the detection limit is 2.0 microg/L. The method has been applied to the direct determination of trace Zr (IV) in the aluminium alloy reference sample with satisfactory results.

English Abstract↗

PubMed1998

Induction of PPARgamma1 expression in human THP-1 monocytic leukemia cells by 9-cis-retinoic acid is associated with cellular growth suppression.

9-cis-Retinoic acid (RA) and peroxisome proliferator activated receptor gamma (PPARgamma) regulates cellular growth and differentiation. In THP-1 cells, a human monocytic leukemia cell line, RA markedly induced PPARgamma1 RNA, nuclear PPARgamma1 protein and suppressed cell growth. The PPARgamma ligand, BRL49653 enhanced RA's growth suppression ability. With BRL49653 alone, THP-1 cell growth was only marginally suppressed. Cell cycle analysis revealed the G1 phase cell population was significantly increased when cells were treated with both ligands. RA induced growth suppression did not differentiate the THP-1 cells to macrophages. Phorbol ester (PMA) induced differentiation of cells to macrophage also induced PPARgamma1 expression, however when RA is given either simultaneously or sequentially to these cells, no further increase in expression of the nuclear receptor was observed. Overall, these data suggest RA induction of PPARgamma1 may block cell growth and may have application for the treatment of proliferative diseases.

Alitretinoin↗

PubMed1998

A photoactivated prodrug.

A photolabile derivative (1) of the anticancer drug, 5-fluorodeoxyuridine (2), was designed and synthesized as a model prodrug. Photolysis of 1 with long-wavelength UV light rapidly released 2 in solution. While compound 1 alone is nontoxic to cells, the presence of both 1 and UV irradiation (lambda = 350 nm) resulted in potent inhibition of cell growth.

Antimetabolites, Antineoplastic↗

PubMed1998

Identification of immediate early genes during TPA-induced human myeloblastic leukemia ML-1 cell differentiation.

Human myeloblastic ML-1 can be induced to differentiate into monocytes/macrophages by 12-0-tetradecanoylphorbol-13-acetate (TPA). In order to understand the molecular mechanism regulating ML-1 cell differentiation, we focused on the characterization of immediate early genes activated by TPA using the mRNA differentiation display polymerase chain reaction (DD-PCR) and Northern analyses. A modified procedure, the reverse dot slot, was developed to confirm upregulated genes during the early stages of TPA-induced ML-1 cell differentiation. DNA sequencing analyses of 10 subcloned cDNA fragments, selected on the basis of the outcome of the reverse dot slot procedure, revealed that eight were derived from distinct genes. Among these clones, one was a novel gene (G07-5), another (A02-1) was highly homologous to the sequence of a fetal brain cDNA fragment, and the remaining six corresponded to jun-D, rantes, ssat, CD 14, ferritin heavy chain (fhc) and transposons Tn10-like transcript, respectively. Although these genes were all upregulated by TPA, the peak time of mRNA expression varied. jun-D, ssat and A02-1 expressions were superinduced in the presence of cycloheximide, which indicates that they belong to the immediate early gene family. On the other hand, TPA-induced rantes expression was not superinduced by cycloheximide, suggesting a protein synthesis-dependent process. As there are no previous reports of expression of these genes in TPA-induced ML-1 cells, little or no information is available concerning their function in mediating myeloblastic cell differentiation. Thus, this study illuminates new avenues of research for elucidating the function of genes regulating terminal differentiation of myeloid progenitors. 1998 Elsevier Science B.V.

Cell Differentiation↗

PubMed1998

Apoptosis, redifferentiation and arresting proliferation simultaneously triggered by oxidative stress in human hepatoma cells.

The effects of oxidative stress (ascorbic acid-ferrous system) on the proliferation, differentiation and apoptosis of the human hepatoma cell SMMC-7721 were studied. Oxidative stress significantly inhibited cell proliferation and induced morphological differentiation. Whatever the indices related with cell malignancy, such as alpha-fetoprotein and c-glutamyltranspeptidase or the index related with cell differentiation, such as tyrosine-alpha-ketoglutarate transaminase, all inclined evidently to normalization. The tumour's clonogenic potential decreased significantly. Moreover, together with differentiation, the phenomenon of apoptosis was found by the appearance of apoptotic bodies, detached cells, and apoptotic morphological feature. Although, their DNA was not degraded into oligonucleosomal fragmentation, the DNA was cut into larger fragments (about 21.2 kbp) of a size associated with chromatin loops. These findings indicated that oxidative stress can induce both differentiation and apoptosis simultaneously in tumour cells. All the results showed that oxidative stress may initiate the tumour cells reverse transformation. The possible mechanism of the differentiation and apoptosis induced by oxidative stress may be related to the lipid peroxidation of cell membrane.

Apoptosis↗

PubMed1998

Ionizing radiation stimulates mitochondrial gene expression and activity.

Radiation-induced gene expression was examined in cells of a radioresistant human glioblastoma cell line, T98G, using RNA fingerprinting by arbitrary primer polymerase chain reaction. Three of the differentially induced transcripts were cloned and identified as the mitochondrially encoded cytochrome c oxidase (MTCO) subunits 1 and 2, and NADH dehydrogenase subunit 4. The levels of all three mRNAs were increased 1 h after irradiation, with elevated expression persisting for at least 24 h. Similar to radiation, other oxidants lead to induction of MTCO1, an effect which could be prevented by the antioxidant pyrrolidine dithiocarbamate. These results indicate that the increase in mitochondrial gene expression is mediated by oxidative stress. Mitochondria could be a target of signaling by ionizing radiation and oxidants since it is known to be at the site of cellular oxidative stress. The proteins encoded by MTCO1 and other mitochondrial mRNAs characterized are part of the mitochondrial respiratory chain which produces adenosine triphosphate through the process of oxidative phosphorylation. Adenosine triphosphate levels and the mitochondrial membrane potential were found to be increased significantly after irradiation, while mitochondrial mass and mitochondrial DNA levels were unaffected. These data demonstrate the specificity of changes in mitochondrial activity and gene expression after irradiation.

Adenosine Triphosphate↗

PubMed1997

New DNA minor-groove binding molecules with high sequence-selectivities and binding affinities.

New DNA minor-groove binding molecules with high binding affinities and sequence-selectivities are described. The effects of structural changes in ligands with a three-ring backbone on their DNA-binding properties have been studied. Of a pool of eight potential ligands, two showed binding affinities and sequence-selectivities rivaling distamycin. The two best ligands share a common structural motif that involves a para-di-substituted benzene ring flanked by two meta-di-substituted benzene rings.

Animals↗

PubMed1997

[The evaluation of endoscopic biliary drainage for 288 patients with malignant hilar obstruction].

Hilar tumors are extremely difficult to manage with a considerably lower resection rate. We performed endoscopic biliary drainage for 288 patients with hilar tumors (Klatskin tumor 184, gallbladder carcinoma 23, HCC 47 and other metastases 34) in the past 3 years. 162 patients underwent endoscopic nasobiliary drainage, 80 plastic biliary stenting, and 46 expandable metal stent implantation. 4 patients were given double stents insertion simultaneously, 43.1% of patients received good drainage with the total effective rate of 67.0%, but postprocedure cholangitis took place in 13.8% of patients within one month and 3 died of cholangitis and sepsis. In the long-term follow-up patients without surgical treatment, the median sruvival was 5.3 months. The outcome was closely related to Bismuth types, and jaundice could be relieved if more than about 40% of the liver was drained. The double stents for the left and right intrahepatic duct in the meantime could enlarge drainage area and improve the theraputic effectiveness. To get highest benefit, the 3 endoscopic biliary drainage methods should be choosen properly and exchanged flexibly. We conclude that endoscopic biliary drainage is a safe and useful management for the hilar tumor and should be the treatment of choice for palliating jaundice in the inoperable patients.

Adolescent↗

PubMed1996

Structure-based design of parasitic protease inhibitors.

To streamline the preclinical phase of pharmaceutical development, we have explored the utility of structural data on the molecular target and synergy between computational and medicinal chemistry. We have concentrated on parasitic infectious diseases with a particular emphasis on the development of specific noncovalent inhibitors of proteases that play a key role in the parasites' life cycles. Frequently, the structure of the enzyme target of pharmaceutical interest is not available. In this setting we have modeled the structure of the relevant enzyme by virtue of its sequence similarity with proteins of known structure. For example, we have constructed a homology-based model of falcipain, the trophozoite cysteine protease, and used the computational ligand identification algorithm DOCK to identify in compuo enzyme inhibitors including oxalic bis(2-hydroxy-1-naphthyl-methylene)hydrazide (1) [Ring, C. S.; Sun, E.; McKerow, J. H.; Lee, G.; Rosenthal, P. J., Kuntz, I. D.; Cohen, F. E., Proc. Natl Acad. Sci. U.S.A. 1993, 90, 3583]. Compound 1 inhibits falcipain (IC50 6 microM) and the organism in vitro as judged by hypoxanthine uptake (IC50 7 microM). Following this lead, to date, we have identified potent bis arylacylhydrazides (IC50 150 nM) and chalcones (IC50 200 nM) that are active against both chloroquine-sensitive and chloroquine-resistant strains of malaria. In a second example, cruzain, the crystallographically determined structure of a papain-like cysteine protease, resolved to 2.35 A, was available. Aided by DOCK, we have identified a family of bis-arylacylhydrazides that are potent inhibitors of cruzain (IC50 600 microM). These compounds represent useful leads for pharmaceutical development over strict enzyme inhibition criteria in a structure-based design program.

Aldehydes↗

PubMed1996

[Effect of Chinese herbal medicine of tonifying kidney on M-cholinergic receptor and acetylcholinesterase activity in dementia mimetic mice].

Dementia mimetic mouse model was formed with aluminum chloride solution in order to study the effect of Chinese herbal medicine of tonifying Kidney (TK) on the M-cholinergic receptor (Rt) and the acetylcholinesterase (AchE) activity in the model's cerebral cortex. Results showed that the M-cholinergic receptor Rt lowered and the AchE increased in the model evidently as compared with the healthy young mice. The TK could markedly reduce the increased AchE and elevate the lowered M-cholinergic receptor Rt in cerebral cortex of the dementia mimetic mice, it also could improve the memory. These results suggest that TK is effective in preventing the degeneration of cerebral function and presenile dementia.

Acetylcholinesterase↗

PubMed1995

In vitro antimalarial activity of chalcones and their derivatives.

A series of chalcones and their derivatives have been synthesized and identified as novel potential antimalarials using both molecular modeling and in vitro testing against the intact parasite. A large number of chalcones and their derivatives were prepared using one-step Claisen-Schmidt condensations of aldehydes with methyl ketones. These condensates were screened in vitro against both chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum and shown to be active at concentrations in the nanomolar range. The most active chalcone derivative, 1-(2,5-dichlorophenyl)-3-(4-quinolinyl)-2-propen-1-one (7), had an IC50 value of 200 nM against both a chloroquine-resistant strain (W2) and a chloroquine-sensitive strain (D6). The resistance indexes for all compounds were substantially lower than for chloroquine, suggesting that this series will be active against chloroquine-resistant malaria. Structure-activity relationships (SAR) of the chalcones in the context of a homology-based model structure of the malaria trophozoite cysteine protease, the most likely target enzyme, are presented.

Animals↗

PubMed1995

[Clinical application of endoscopic injection of medication for stopping gastric bleeding].

The authors studied 40 patients with bleeding from peptic ulcer or gastric carcinoma, and evaluated the therapeutic effects of endoscopic injection of absolute alcohol and Bathroxobin. Among them, 20 patients were given absolute alcohol and the remaining 20 Bathroxobin (Reptilase). Absolute alcohol was injected submucosally at 4-6 pinpoints around the bleeding site (0.1-0.2ml/dose, total dose 0.5-1.2ml); Bathroxobin was injected similarly (1 kU/dose, total dose 0.5-1.0kU). Treatment failed in one patient receiving alcohol because of spouting artery bleeding and surgery was resorted to finally. The other 39 patients had successful stopping of the bleeding in one time. The effective rate is 97.5 percent (39/40) and the rate of re-bleeding is low. It is thus shown that endoscopic submucosal injection of absolute alcohol and Bathroxobin for stopping gastric bleeding is safe, simple and effective. However, more experience is needed in this respect.

Adult↗

PubMed1994

[Influence of acupuncture at zusanli point on function of 5-HT and M receptor in rat's brain and spleen].

5-HT and muscarine (M) receptors total binding capacities (Rt) in different brain areas and spleen were determined using receptor radioligand binding assay (RLBA) after needling zusanli of rats. And the rats without needling and needling Taichong point were used as control. These results showed that 5-HT and M receptors Rt were decreased obviously than control group in rat's cerebral cortex, hippocampus, striatum, spinal cord and spleen when needling zusanli can produce obvious acupuncture analgesia. 5-HT Rt in brain stem and medulla oblongata was obviously decreased and not changed in thalamus. M receptor Rt value was not changed clearly in brain stem and medulla oblongata as well, but it was obviously decreased in thalamus. These results showed that effects of acupoints on Various meridians are different, thus the results of acupuncture at Zusanli are distinct from taichong.

Acupuncture Points↗

PubMed1992

[Iterative estimation of variance components for a mixed model with a numerator relationship matrix: apply to compute K of variance ratio in BLUP and genetic parameters].

An iterative procedure is presented for the estimation of variance components in the mixed model with a numerator relationship matrix from non-balanced data. This method has been shown to be feasible if only designing matrix for fixed effects of the mixed model and Henderson method 3 hypothetic condition of the fixed effect to compute correctly the reduction in sum of squares, we would obtain more precise estimation of variance components, furthermore, the sizes of the initial value K could not affect to last result of the iterative solution. This is because in the iterative process may adjust automatically by designing matrix. Also, the variance components could apply not only to compute variance ratio in BLUP, but also to estimate genetic parameters.

Animals↗