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Biomedical subjects

B Cheng

Publications and source records attributed to B Cheng.

At least 19 recordsLinked to original sources
PubMed2002

SCORPION, a molecular database of scorpion toxins.

Increasing interest in the studies of toxins and the requirements for better structural and functional annotations have created a need for improved data management in the field of toxins. The molecular database, SCORPION, contains more than 200 entries of fully referenced scorpion toxin data including primary sequences, three-dimensional structures, structural and functional annotations of scorpion toxins along with relevant literature references. SCORPION has a set of search tools that allow users to extract data and perform specific queries. These entries have been compiled from public databases and literature, cleaned of errors and enriched with additional structural and functional information. The grouping of scorpion toxins provides a basis for extending and clarifying the existing structural and functional classifications. The bioinformatics modules in SCORPION facilitate analyses aimed at classification of scorpion toxins and identification of sequence patterns associated with specific structural or functional properties of scorpion toxins. The SCORPION database is accessible via the Internet at sdmc.krdl.org.sg:8080/scorpion.

Animals↗
PubMed2002

Herbal medicine and anaesthesia.

Herbal medicines are increasingly used in both western and Chinese societies. This is partly attributed to the alleged limitations of scientific medicine in the cure and control of chronic diseases. Many patients do not disclose that they have used herbs before surgery and hence their physicians remain unaware of the potential herb-drug interactions. With respect to anaesthesia, herbs can cause coagulation disorders, cardiovascular side-effects, water and electrolyte disturbances, endocrine effects, hepatotoxicity, and prolongation of the effects of anaesthetic agents. Anaesthesiologists should obtain a history of herbal medicine use from patients and work out the adverse perioperative herb-drug interactions in advance of the actual operation. If in doubt, the herbal medicine should be stopped for 2 weeks prior to anaesthesia and surgery.

Anesthesia↗
PubMed2001

An experimental and theoretical study of the inhibition of Escherichia coli lac operon gene expression by antigene oligonucleotides.

Previously, we have developed a genetically structured mathematical model to describe the inhibition of Escherichia coli lac operon gene expression by antigene oligos. Our model predicted that antigene oligos targeted to the operator region of the lac operon would have a significant inhibitory effect on beta-galactosidase production. In this investigation, the E. coli lac operon gene expression in the presence of antigene oligos was studied experimentally. A 21-mer oligo, which was designed to form a triplex with the operator, was found to be able to specifically inhibit beta-galactosidase production in a dose-dependent manner. In contrast to the 21-mer triplex-forming oligonucleotide (TFO), several control oligos showed no inhibitory effect. The ineffectiveness of the various control oligos, along with the fact that the 21-mer oligo has no homology sequence with lacZYA, and no mRNA is transcribed from the operator, suggests that the 21-mer oligo inhibits target gene expression by an antigene mechanism. To simulate the kinetics of lac operon gene expression in the presence of antigene oligos, a genetically structured kinetic model, which includes transport of oligo into the cell, growth of bacteria cells, and lac operon gene expression, was developed. Predictions of the kinetic model fit the experimental data quite well after adjustment of the value of the oligonucleotide transport rate constant (9.0 x 10(-)(3) min(-)(1)) and oligo binding affinity constant (1.05 x 10(6) M(-)(1)). Our values for these two adjusted parameters are in the range of reported literature values.

Biological Transport↗
PubMed2001

Ketene reactions with the aminoxyl radical tempo: preparative, kinetic, and theoretical studies.

Tetramethylpiperidinyloxy (TEMPO, TO*) reacts with ketenes RR(1)C=C=O generated by either Wolff rearrangement or by dehydrochlorination of acyl chlorides to give products resulting from addition of one TEMPO radical to the carbonyl carbon and a second to the resulting radical. Reactions of phenylvinylketenes 4b and 4f, phenylalkynylketene 4c, and the dienylketene AcOCMe=CHCH=CHCMe=C=O (11) occur with allylic or propargylic rearrangement. Even quite reactive ketenes were generated as rather long-lived species by photochemical Wolff rearrangement in isooctane solution, characterized by IR and UV, and used for kinetic studies. The rate constants of TEMPO addition to eight different ketenes have been measured and give a qualitative correlation of log k(2)(TEMPO) = 1.10 log k(H(2)O) -3.79 with the rate constants for hydration of the same ketenes. Calculations at the B3LYP/6-311G//B3LYP/6-311G level are used to elucidate the ring opening of substituted cyclobutenones leading to vinylketenes and of 2,4-cyclohexadienone (17) forming 1,3,5-hexatrien-1-one (18).

Journal Article↗
PubMed2001

Functional site of bukatoxin, an alpha-type sodium channel neurotoxin from the Chinese scorpion (Buthus martensi Karsch) venom: probable role of the (52)PDKVP(56) loop.

Alpha-toxins from scorpion venoms prolong the action potential of excitable cells by blocking sodium channel inactivation. We have purified bukatoxin, an alpha-toxin from scorpion (Buthus martensi Karsch) venom, to homogeneity. Bukatoxin produced marked relaxant responses in the carbachol-precontracted rat anococcygeus muscle (ACM), which were mediated through the L-arginine-nitric oxide synthase-nitric oxide pathway, consequent to a neuronal release of nitric oxide. Based on the presence of proline residues in the flanking segments of protein-protein interaction sites, we predicted the site between (52)PP(56) to be the potential interaction site of bukatoxin. A homology model of bukatoxin indicated the presence of this site on the surface. Buka11, a synthetic peptide designed based on this predicted site, produced a concentration-dependent nitric oxide-mediated relaxant response in ACM. Using alanine-substituted peptides, we have shown the importance (53)DKV(55) flanked by proline residues in the functional site of bukatoxin.

Amino Acid Motifs↗
PubMed2001

Resistance exercise decreases skeletal muscle tumor necrosis factor alpha in frail elderly humans.

Skeletal muscle protein and function decline with advancing age but the underlying pathophysiology is poorly understood. To test the hypothesis that the catabolic cytokine tumor necrosis factor alpha (TNF-alpha) contributes to this process, we studied the effects of aging and resistance exercise on TNF-alpha expression in human muscle. Using in situ hybridization, TNF-alpha message was localized to myocytes in sections of skeletal muscle from elderly humans. Both TNF-alpha mRNA and protein levels were elevated in skeletal muscle from frail elderly (81+/-1 year) as compared to healthy young (23+/-1 year) men and women. To determine whether resistance exercise affects TNF-alpha expression, frail elderly men and women were randomly assigned to a training group or to a nonexercising control group. Muscle biopsies were performed before and after 3 months. Muscle TNF-alpha mRNA and protein levels decreased in the exercise group but did not change in the control group. Muscle protein synthesis rate in the exercise group was inversely related to levels of TNF-alpha protein. These data suggest that TNF-alpha contributes to age-associated muscle wasting and that resistance exercise may attenuate this process by suppressing skeletal muscle TNF-alpha expression.

Adult↗
PubMed2001

Molecular mechanisms of hepatitis B virus-associated liver cancer.

Hepatitis B infection is associated with an increased risk of hepatocellular carcinoma development. Hepatitis B proteins, such as the hepatitis B x protein, the large hepatitis B surface protein, or truncated middle hepatitis B surface proteins, regulate transcription of many candidate genes for liver carcinogenesis by trans-mechanisms. They also alter mechanisms of apoptosis and interfere with nucleotide excision repair of damaged DNA. Together with an influence on cellular signaling, these mechanisms may favor the cell's clonal expansion.

Antigens, Viral↗
PubMed2001

PGE(2) is essential for gap junction-mediated intercellular communication between osteocyte-like MLO-Y4 cells in response to mechanical strain.

We have observed, in our previous studies, that fluid flow increases gap junction-mediated intercellular coupling and the expression of a gap junction protein, connexin 43, in osteocyte-like MLO-Y4 cells. Interestingly, this stimulation is further enhanced during the poststress period, indicating that a released factor(s) is likely to be involved. Here, we report that the conditioned medium obtained from the fluid flow-treated MLO-Y4 cells increased the number of functional gap junctions and connexin 43 protein. These changes are similar to those observed in MLO-Y4 cells directly exposed to fluid flow. Fluid flow was found to induce PGE(2) release and increase cyclooxygenase 2 expression. Treatment of the cells with PGE(2) had the same effect as fluid flow, suggesting that PGE(2) could be responsible for these autocrine effects. When PGE(2) was depleted from the fluid flow-conditioned medium, the stimulatory effect on gap junctions was partially, but significantly, decreased. Addition of the cyclooxygenase inhibitor, indomethacin, partially blocked the stimulatory effects of mechanical strain on gap junctions. Taken together, these studies suggest that the stimulatory effect of fluid flow on gap junctions is mediated, in part, by the release of PGE(2). Hence, PGE(2) is an essential mediator between mechanical strain and gap junctions in osteocyte-like cells.

Animals↗
PubMed2001

Expression of functional gap junctions and regulation by fluid flow in osteocyte-like MLO-Y4 cells.

Osteocytes are thought to be mechanosensory cells that respond to mechanical stress by sending signals to other bone cells to initiate bone remodeling. An osteocyte-like cell line MLO-Y4 provides a model system to examine whether gap junctions participate in the regulation of osteocyte function and signaling by mechanical stress. In this study, we show that MLO-Y4 cells are coupled and that gap junction channels mediate this coupling. Biochemical analyses show that connexin 43 (Cx43) is a major gap junction protein expressed in MLO-Y4 cells and approximately 5% of Cx43 protein is phosphorylated. MLO-Y4 cells were exposed to mechanical stress using a parallel plate flow chamber to model bone fluid flow shear stress. Fluid flow increased significantly the length of the dendritic processes, a morphological characteristic of osteocytes. A redistribution of the gap junction protein, Cx43 also was observed from a location circling the nucleus to punctate spots in the cytoplasm and in the dendritic processes. "Scrape-loading" dye transfer analyses showed that fluid flow increased intercellular coupling and increased the number of cells coupled immediately after fluid flow treatment, in direct proportion to shear stress magnitude. Although intercellular coupling continued to increase, stimulation of Cx43 protein expression during the poststress period was found to be biphasic. Cx43 protein was elevated 30 minutes after application of stress but decreased at 24 h poststress. Pulsating fluid flow had a similar stimulatory effect as steady fluid flow on gap junctions. However, this stimulatory effect in osteocyte-like cells was not observed in osteoblast-like 2T3 cells. Together, these results show that fluid flow has stimulatory effects on osteocyte-like MLO-Y4 cells with early effects on cellular morphology, opening of gap junctions, and redistribution of Cx43 protein and delayed effects on Cx43 protein expression. The high expression of Cx43 and its location in the cytoplasm also suggest that Cx43 may have unknown functions in addition to forming gap junctions. These studies indicate that gap junctions may serve as channels for signals generated by osteocytes in response to mechanical loading.

Blotting, Western↗
PubMed2001

Selective suppression of renal Na+/H+ exchanger isoform-3 by prolonged stimulation of rats with adrenocorticotropic hormone.

Prolonged stimulation with adrenocorticotropic hormone (ACTH) causes hypertension and increases Na+ intake and urine output in humans and animals. However, its biochemical basis remains to be established. Since renal Na+/H+ exchanger isoforms (NHE) and the sodium pump play an important role in this condition, their levels were examined in rats stimulated with ACTH. Male Wistar rats received daily sc injection of ACTH (30 microg/100 g of body wt) for 4 d. Half of the ACTH-stressed rats were kept for four additional days without injection of ACTH (poststimulation). In a third group, the animals were treated with dexamethasone (50 microg/100 g of body wt) daily for 4 d. A fourth group consisted of unstressed control animals. Levels of NHE proteins were measured by Western blot analysis. Sodium pump activity was assessed by the level of ouabain-sensitive K-stimulated p-nitrophenylphosphatase activity (PNP) in the renal cortex. ACTH caused a selective decrease in NHE-3, but not of NHE-1 or alpha-actin levels. Interestingly, this ACTH-induced change was not duplicated in the animals treated with dexamethasone. Immunofluorescence data demonstrated that NHE-3 is located in the renal proximal tubules. PNP activity, on the contrary, was increased in both the ACTH-stimulated and dexamethasone-treated animals. More important, these changes in NHE-3 and PNP activity returned to the control level poststimulation. In conclusion, while PNP upregulation may be mediated by adrenocortical glucocorticoid, a role for glucocorticoids in the suppression of NHE-3 is less clear. These changes might impair renal tubular Na+ reabsorption and hence increase Na+ and water excretion in ACTH stimulation, thus acting as a counterbalance to normalize blood pressure in ACTH-stimulated animals.

4-Nitrophenylphosphatase↗
PubMed2001

Mechanical stimulation of gap junctions in bone osteocytes is mediated by prostaglandin E2.

Gap junction-mediated intercellular communications are thought to transduce the effects of mechanical strain from osteocytes to cells on the bone surface to initiate remodeling. To determine whether gap junctions may co-ordinate the effects of mechanical loading, osteocyte-like MLO-Y4 cells were exposed to fluid flow-imposed shear stress. After exposure of MLO-Y4 to fluid flow, intercellular coupling increased in direct proportion to shear stress level. Interestingly, this stimulation is further enhanced during the post-stress period, indicating that released factor(s) is likely to be involved. The conditioned medium obtained from the fluid flow treated MLO-Y4 cells induced an increase in the number of functional gap junctions and Cx43 protein when added to non-sheer-stressed cells. Fluid flow was found to induce prostaglandin F2 (PGE2) release and increase cyclooxygenase 2 (COX-2) expression. When PGE2 was depleted from the fluid flow conditioned medium, the stimulatory effect on gap junctions was significantly decreased. Addition of the COX inhibitor indomethacin partially blocked the stimulatory effects of mechanical strain on gap junctions. Together, these studies suggest that the stimulatory effect of fluid flow on gap junctions is mediated in part by de novo synthesis and release of PGE2. Gap junctions may serve as channels for the signals generated by osteocytes in response to mechanical loading.

Animals↗
PubMed2001

Growth inhibition of interleukin-2 receptor gene-transduced peripheral blood lymphocytes on human ovarian cancer cells.

OBJECTIVE: To investigate the growth inhibition of interleukin-2 receptor (IL-2R) gene-transduced peripheral blood lymphocytes (PBLs) on human ovarian cancer cells. METHODS: Interleukin-2 (IL-2) and IL-2R genes were transfected into human ovarian cancer cell line 3AO and PBLs, respectively, using the same Fugene vector. Twenty-four hours later transfected and nontransfected PBLs were cocultured with transfected and nontransfected 3AO for 48 hours. cytotoxicity of PBLs on 3AO was detected by the MTT assay. RESULTS: The morphology of IL-2-transduced 3AO and IL-2R-transduced PBLs remained unchanged. 3AO cells could be transfected with the IL-2 gene and expressed IL-2 mRNA, and PBLs could be transfected with the IL-2R gene and expressed IL-2R mRNA. IL-2 transduced 3AO cells enhanced their response to the cytotoxicity of PBLs. Furthermore, growth inhibition of PBLs to 3AO cells increased significantly when the IL-2R was transfected into PBLs and when the IL-2 gene was transfected into 3AO cells and the two were combined. CONCLUSIONS: IL-2R gene transduced PBLs are able to enhance their cytotoxicity on IL-2 gene transduced ovarian cancer cells. This method may be a new way to investigate IL-2 gene therapy for ovarian cancer.

Cell Count↗
PubMed2001

[Study on diarrhea disease and Escherichia coli strains harboring HPI pathogenicity island of Yersinia enterolitica in Shandong province].

OBJECTIVE: It was found that some E. coli strains previously identified as entero SLTs-producing and invasive E. coli (ESIEC), harboring HPI pathogenicity island of Yersinia enterolitica. This research was designed to reveal prevalence, susceptible group and clinical features it caused. METHODS: All of the diarrhea patients were from the out-patient units of four hospitals in Shandong province from June to November of 1997. Stool specimen were collected before administration of antibiotics for isolation of enteric bacterial pathogen. Clinical symptoms were recorded at the same time. RESULTS: A total number of 449 enteric pathogenic bacteria strains were detected among stool samples from 671 patients, with isolation rates of Shigella species and diarrheagenic E. coli 25.48% and 15.05% respectively. When irp-2 and ipaB gene fragments were used as DNA probes, 42 of 176 un-identifiable strains were found irp-2(+) and ipaB(-), which were identified as HPI-harboring E. coli. Typical symptoms of the diarrhea caused by HPI-harboring E. coli were described as mild, including abdominal pain, shiver and vapidity. Temperature of the patients was usually normal. Over 6 times of bowel movements per day was frequently observed, of which most were unformed stools with mucous. CONCLUSION: HIP-harboring E. coli was an important diarrheagenic pathogen identified from 671 patients with diarrhea. Shigella was found to be the majority strain.

China↗
PubMed2001

[Surgical treatment of great vessel injuries of thoracic outlet].

OBJECTIVE: To summarize the experience in surgical treatment of great vessel injury of the thoracic outlet. METHODS: Thirty-two cases (24 men and 8 women aged 2-48 years) treated by surgery were collected during the period of 1970-1998. Sharp injury, blunt injury or decelerated injury was the causes. The vessels of injury included the common carotid artery, subclavian artery and accompanying veins. Emergency suture or repair of the artery with polyester patch was performed in 15 patients, aneurysmectomy in 6, resection of vessels with end-to-end anastomosis in 5, Gore-Tex vessel reconstruction in 2, and transplantation of the great saphenous vein in 3. RESULTS: Twenty-four patients (75%) were cared and 7 (21.8%) died. CONCLUSIONS: In the early period, patients with great vessel injury of the thoracic outlet died from acute bleeding, cerebral ischemia or combined multiple injuries, in the later period, however, false aneurysm develop. The operation is appropriate to the recondition of damaged cut, the effect of evolution in false aneurysm is approving. For large damaged cut or for bigger vessel injuries, the repair with polyester patch, Gore-Tex of blood vessel reconstruction or the transplantation of the great saphenous vein must be used.

Adolescent↗
PubMed2001

[The role of Fos protein in modulation of dental pain in central nerve system].

OBJECTIVE: The aims of this study were to reveal the relationship between Fos protein expression, the transcription of preproenkephalin (PENK) mRNA, and the change of enkephalin (ENK) level initiated by experimental dental pain, and to understand the central modulation mechanism of dental pain. METHODS: The techniques of Immunohistochemistry in situ hybridization and radioimmunoassay were applied respectively to detect the expression of Fos, the transcription of PENK mRNA, and the change of ENK level in the experimental nucleus of the spinal tract of the trigeminal nerve, caudal part (sp5c) of rats. RESULTS: It was found that Fos protein expression was in a time-dependent manner. Fos appeared half hour after the pain stimulation, and its peak occurred two hours after the pain stimulation, but disappeared slowly four hours later. The transcription of PENK mRNA was seen two hours after the pain stimulation, its peak appeared four hours later and it disappeared eight hours later. The level of ENK increased significantly (P < 0.01) in the caudal part of the spinal tract of the trigeminal nerve four hours after pain stimulation. CONCLUSION: Fos protein may take a part in the central modulation of dental pain by initiating PENK mRNA transcription which led to the increment of ENK.

Animals↗
PubMed2001

The preliminary clinical observation of array multifocal intraocular lens implantation.

PURPOSE: To evaluate the clinical effects of implantation of Array multifocal intraocular lenses. METHODS: Thirty-one cases (37 eyes) of cataract patients, including 15 males (19 eyes) and 16 females (18 eyes), were involved in this study. All patients underwent standard phacoemulsification with Array multifocal intraocular lens implantation. The complications during operation, postoperative distant visual acuity, near visual acuity, corneal curvature and visual symptoms were observed. RESULTS: The mean value of best postoperative visual acuity was recorded as follows: uncorrected distant visual acuity was 0.8, the best-corrected distant visual acuity was 0.9, uncorrected near visual acuity was 0.5, near visual acuity with distant-corrected was 0.6, the best-corrected near visual acuity was 0.9. The astigmatism of cornea was less than 1.5 D pre-operatively and post-operatively. One patient complained of glare. CONCLUSION: Array multifocal intraocular lens can provide good distant and near visual acuity. With observation of more cases and follow-up of longer time, we can draw a further conclusion.

Aged↗