Biomedical subjects

E Wang

Publications and source records attributed to E Wang.

At least 181 records · Page 10Linked to original sources

PubMed1998

[Experimental studies on human lung cancer gene-therapy with HSV-TK/GCV system].

OBJECTIVE: Evaluate the clinical potential of HSV-TK/GCV system in gene-therapy of tumors by using this system to treat human lung cancer A549 cells in vitro and in vivo. METHOD: The in vitro sensitivity levels of A549/TK (TK-tranfered A549) cells and wild type A549 cells to GCV were expressed as IC50 which was measured with MTT assay after treating both cells for 72 hrs. In vivo study, The nude mice bearing A549/TK tumor or A549 tumor were used as experimental models. All the animals were divided into 3 groups. Group 1, the animals bearing A549/TK tumor would be treated with GCV. Group 2, The animals bearing A549/TK tumor would be treated with saline. Group 3, The animals bearing A549 tumor would be treated with GCV. When the tumors reached to 200-300 mg the animals would be injected intraperitoneally with GCV solution (100 mg.kg-1.day-1) or equal volume of saline for two weeks. In this period and the following four weeks, the tumor weights were measured and calculated with the experience formula once every three or four days. RESULT: In vitro study showed that the A549/TK cells were apparently killed in a 20 mumol/L GCV solution while the wild type A549 cells grew normally under the same condition. The IC50 of A549/TK cells in GCV solution was 0.5 mumol/L and that of A549 cells 500 mumol/L, showing a 1,000 fold difference (P < 0.01). In vivo experiment GCV had compelled the A549/TK tumors to lead to a regression of 92%, meanwhile the A549 tumors treated with GCV increased 3.9 times in weight in the first seventeen days of experiment. Group 2 tumors A549/TK tumors which were treated with saline, grew as well as group 3 did. There was a significant difference (P < 0.01) between group 1 and other groups. CONCLUSION: GCV could specifically and effectively kill the TK-transfered A549 cells in vitro and in vivo. This result suggested that the HSV-TK/GCV system may have a clinical potential for gene therapy of lung cancer.

Adenocarcinoma↗

PubMed1998

[A study of epithelial cell kinetics of the odontogenic keratocyst].

OBJECTIVE: To study epithelial cell kinetics of the odontogenic keratocyst. METHODS: Proliferating cell nuclear antigen (PCNA) immunohistochemistry in 60 cases and cellular nuclear DNA contents cytometry in 40 cases were used to compare the epithelial cell kinetics of the odontogenic keratocyst, radicular cyst, dentigerous cyst, and ameloblastoma. RESULTS: The epithelial cells in odontogenic keratocyst has the potential of active growth instead of passive expanding. CONCLUSION: The authors suggest that the odontogenic keratocyst should be termed as "odontogenic keratocystic tumor" because is aggressive growth potential.

Cell Division↗

PubMed1998

[Synthesis and anti-influenza virus activities of heteropoly compounds containing rare earth elements].

Tungstoborate and tungstogermanate heteropoly compounds containing rare earth elements with the general formula K15[Ln(BW11O39)2].nH2O and K13[Ln(GeW11O39)2].nH2O, where Ln = La, Ce, Pr, Nd, Sm, have been synthesized and characterized by elemental analysis, IR, 183W NMR spectra. The results of experiments on cytotoxicity and anti-influenza virus activities using cell-cultivation method showed that four compounds among them exhibited good inhibitory effect on influenza virus.

Animals↗

PubMed1997

Calmodulin binds to caldesmon in an antiparallel manner.

Two of the five tryptophan residues (W659 and W692) in chicken gizzard smooth muscle caldesmon (CaD) are located within the calmodulin (CaM) binding sites in the C-terminal region of the molecule. When these Trp residues are replaced with Gly in either recombinant fragments or synthetic peptides of CaD, the affinity for CaM is decreased by at least 10-fold, suggesting that both of these residues are important for the interaction of CaD with CaM. To gain information about the topography of the CaM-CaD complex, we have carried out fluorescence titrations of CaM with Tb3+ as a substitute for Ca2+ in the presence of wild-type or mutated CaD variants. By exciting Trp residues of CaD fragments or peptides while monitoring the enhanced luminescence of CaM-bound Tb3+ ions via resonance energy transfer, we were able to estimate the relative proximity between the bound metal ions in the two domains of CaM and the Trp residues of CaD. Our results suggest that in the CaM-CaD complex the metal-binding sites III and IV in the C-terminal domain of CaM are very close to W659 of CaD; the N-terminal domain of CaM appears associated with the region of CaD in the vicinity of W692, although sites I and II are relatively far away from this Trp residue. These findings are consistent with a model in which CaM binds to CaD in an antiparallel manner. Such a binding mode, however, may be flexible enough to accommodate alternative spatial arrangements when the preferred binding sites are either altered or rendered unavailable.

Amino Acid Sequence↗

PubMed1997

Posttranscriptional regulation of protein expression in human epithelial carcinoma cells by adenine-uridine-rich elements in the 3'-untranslated region of tumor necrosis factor-alpha messenger RNA.

Eukaryotic mRNAs contain 3'-untranslated regions (UTR) that are involved in posttranscriptional control of gene expression. AU-rich octanucleotide repeats, UUAUUUAU, present in the 3'-UTR of mature lymphokine and other cytokine transcripts, have been implicated in the regulation of mRNA stability and translational efficiency. For example, previous evidence suggests that the AU-rich element (ARE) present in the 3'-UTR of murine tumor necrosis factor-alpha (TNF-alpha) can affect the posttranscriptional regulation of murine TNF-alpha gene expression in hematopoietic cells. Although cytokines are produced in epithelial cells, little is known about the regulation of TNF-alpha and other cytokine gene expression by 3'-UTR elements in human malignant epithelial cells. To better understand the function of the 3'-UTR of the human TNF-alpha gene in the regulation of TNF-alpha protein production in human epithelial cancer cells, a series of luciferase reporter constructs with portions of the 3'-UTR of human TNF-alpha was transfected into human breast carcinoma cell lines ZR-75-1 and ZR-75-1R (which overexpresses TNF-alpha). The 3'-UTR of TNF-alpha markedly suppressed luciferase activity in both cell lines, and the suppression of activity was reversed by deletion of the AU-rich sequences. This suppression was quantitative, with six repeats causing more inhibition than two repeats. Increased levels of luciferase activity were observed 3 h after TNF-alpha stimulation in ZR-75-1 cells transfected by constructs containing AU-rich repeats. In addition, cytoplasmic extracts from both cell lines were assayed for factors that bind to the 3'-UTR of human TNF-alpha mRNA. RNA-protein binding activities were found in both cell lines. Competition studies showed that these proteins specifically bound to AU-rich repeats present in the 3'-UTR of TNF-alpha. No binding activity was observed when the AU-rich repeats were deleted. TNF-alpha exposure markedly increased activity of several RNA-binding proteins, especially a novel Mr 50,000-55,000 RNA-binding protein. The binding activity in untreated ZR-75-1R was higher than that in untreated ZR-75-1 cells, suggesting that the level of RNA-protein binding correlates with the expression level of TNF-alpha in human epithelial cancer cells and that the RNA-binding proteins may control expression of TNF-alpha in ZR-75-1 cells. We conclude that the AU-rich repeats in the 3'-UTR of human TNF-alpha mRNA may regulate gene expression in human epithelial cancer cells by binding to AU sequence-specific proteins, including a previously undescribed Mr 50,000-55,000 protein not observed in hematopoietic cells.

Animals↗

PubMed1997

Characterization of ceramide synthesis. A dihydroceramide desaturase introduces the 4,5-trans-double bond of sphingosine at the level of dihydroceramide.

Ceramide (N-acylsphingosine) biosynthesis has been proposed to involve introduction of the 4,5-trans-double bond of sphingosine after synthesis of dihydroceramide (i.e. N-acylsphinganine). For the first time, the in vitro conversion of dihydroceramide to ceramide has been demonstrated using rat liver microsomes and N-[1-14C]octanoyl-D-erythro-sphinganine (st-H2Cer) and either NADH or NADPH as co-substrate; the apparent Km values for st-H2Cer and NADH were 340 and 120 microM, respectively. Molecular oxygen is required for enzymatic activity, and cyanide, divalent copper, as well as antibodies raised against cytochrome b5 are inhibitory, which suggests that this enzyme should be named dihydroceramide desaturase based on these similarities with the mechanism of delta9-desaturase (stearoyl-CoA desaturase). Factors that influenced the activity of dihydroceramide desaturase include the alkyl chain length of the sphingoid base (in the order C18 > C12 > C8) and fatty acid (C8 > C18); the stereochemistry of the sphingoid base (D-erythro- > L-threo-dihydroceramides); the nature of the headgroup, with the highest activity with dihydroceramide, but some (approximately 20%) activity with dihydroglucosylceramide, however); and the ability to utilize alternative reductants (ascorbic acid could substitute for a reduced pyridine nucleotide, but was inhibitory at higher concentrations). Dihydroceramide desaturase was inhibited by dithiothreitol, which suggests that it might be possible to alter ceramide synthesis by varying the thiol status of hepatocytes. Consistent with this hypothesis, when rat hepatocytes were cultured in varying concentrations of N-acetylcysteine (5 and 10 mM), there was a decrease in the relative incorporation of [14C]serine into [14C]ceramide. These studies have conclusively established the pathway of ceramide synthesis via desaturation of dihydroceramide and have uncovered several properties of this reaction that warrant further consideration for their relevance to both sphingolipid metabolism and signaling.

Animals↗

PubMed1997

The rate of mitochondrial mutagenesis is faster in mice than humans.

We have investigated mitochondrial DNA (mtDNA) mutagenesis in the laboratory mouse. Using a nested PCR method for quantification, the absolute frequency, tissue distribution and rate of increase of mitochondrial deletion mutations was determined. Multiple deletions arise in brain, cardiac muscle and kidney tissues: deletions occur most frequently at regions of directly repeated mtDNA homology. Deletion frequencies rose by 2.5 x 10(5), 6300- and 4000-fold in heart, brain and kidney, respectively, between young and old mice. The rates of mtDNA mutation accumulation in mouse and human hearts are modeled well by exponential equations, with r-values of 0.96 and 0.97, and mutations rose much faster in mouse than human mtDNA per unit time. Thus, maintenance of the human mitochondrial genome is much better than that of mice, consistent with the higher rate and final extent of total DNA repair in humans than mice, that has been observed by others and consistent with the predictions of the disposable soma model of aging. A comparison of mtDNA mutagenesis from cardiocytes vs. whole heart tissue was undertaken. Deletion mutations were observed to be 100-fold lower in DNA prepared from isolated cardiocytes than from whole heart homogenates, consistent with a model of uneven mtDNA mutation accumulation.

Adolescent↗

PubMed1997

Evidence against formation of A23187 dimers and oligomers in solution: photo-induced degradation of Ionophore A23187.

Ionophore A23187 has been proposed to form Ca(2+)- conducting channels that arise from dimers and oligomers of the compound (e.g., Balasubramanian, S. V., and Easwaran, K. R. K. (1989) Biochem. Biophys. Res. Commun. 158, 891-897). To investigate this possibility, the solution behavior of A23187 in chloroform, n-hexane, ethanol, 80% methanol-water, and palmitoyloleoylphosphatidyl choline (POPC) vesicles was investigated using UV-VIS, circular dichroism (CD), and 1H NMR techniques. The concentration dependence of the UV-VIS and CD spectra obtained in freshly prepared chloroform solutions indicates that neutral A23187 (HA) exists as a monomer for ionophore concentrations in the range of 50-1000 microM. The cause of time- and concentration-dependent spectral alterations which gave rise to the dimer/channel hypothesis was also investigated. For solutions of 50-1000 microM A23187 in chloroform, n-hexane, and ethanol stored in the dark, no spectral changes were observed for periods of 2 months. However, solutions in these solvents did show time-dependent spectral changes when exposed to light. In 80% methanol-water or phospholipid vesicles, similar spectral changes were observed, even when the solutions were protected from light. Application of TLC and MS methods indicate that the time-dependent spectral changes reflect degradation of A23187, not dimer or oligomer formation. The degradative processes proceed with half-lives ranging from approximately 75 to > 400 h, and are influenced by several factors, including solvent, exposure to light, ionophore concentration, pH, and the presence of metal ions, EDTA, dissolved oxygen, and a radical inhibitor. The kinetics of Ca2+ transport into Quin-2-loaded POPC vesicles by authentic A23187 give no evidence of a channel mechanism, even following a previous and lengthy coincubation of the ionophore with the vesicles.

Calcimycin↗

PubMed1997

Surface Deformation and Lower Crustal Flow in Eastern Tibet

Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.

Journal Article↗

PubMed1997

Up-regulated P21CIP1 expression is part of the regulation quantitatively controlling serum deprivation-induced apoptosis.

Among the many genes which have been suggested to be required by the molecular mechanism dictating apoptotic death, some have been shown to function as pacemakers to pave the way for cells either to liver or to die. Previously we have shown that immediate early gene expression associated with the G1 phase of cell cycle traverse are candidates for this function. Here we report that well-known key regulator for halting cell cycling at the G1/S border, the p21 protein known as WAF1, Cip1, Pic1, or Sdi1, is also involved in the execution of cells' suicidal death. p21 up-regulation is seen in quiescent mouse 3T3 fibroblasts stimulated to die by serum deprivation, at both message and protein levels, evidenced by increased protein presence in its targeted functional site, the nucleus. In addition, we show that this up-regulation of p21 is functionally related to the operational efficiency of the apoptotic process, in that when cells are stably transfected with an antisense construct to repress the endogenous p21-protein level, death is delayed. Quantitative protection from apoptosis with antisense p21 transfection is relatively proportional to the repressed level of this protein in the cells. Taken together, our results suggest that the apoptotic-dependent additional increase of p21 beyond the base level, seen in serum-deprived quiescent cells, may be involved in the molecular events precipitating a rapid program of cell demise, and that repression of this increase may obstruct the operation of this program and postpone the eventual death.

Animals↗

PubMed1997

Sphingolipids--the enigmatic lipid class: biochemistry, physiology, and pathophysiology.

The "sphingosin" backbone of sphingolipids was so named by J. L. W. Thudichum in 1884 for its enigmatic ("Sphinx-like") properties. Although still an elusive class of lipids, research on the involvement of sphingolipids in the signal transduction pathways that mediate cell growth, differentiation, multiple cell functions, and cell death has been rapidly expanding our understanding of these compounds. In addition to the newly discovered role of ceramide as an intracellular second messenger for tumor necrosis factor-alpha, IL-1beta, and other cytokines, sphingosine, sphingosine-1-phosphate, and other sphingolipid metabolites have recently been demonstrated to modulate cellular calcium homeostasis and cell proliferation. Perturbation of sphingolipid metabolism using synthetic and naturally occurring inhibitors of key enzymes of the biosynthetic pathways is aiding the characterization of these processes; for examples, inhibition of cerebroside synthase has indicated a role for ceramide in cellular stress responses including heat shock, and inhibition of ceramide synthase (by fumonisins) has revealed the role of disruption of sphingolipid metabolism in several animal diseases. Fumonisins are currently the focus of a FDA long-term tumor study. This review summarizes recent research on (i) the role of sphingolipids as important components of the diet, (ii) the role of sphingoid base metabolites and the ceramide cycle in expression of genes regulating cell growth, differentiation, and apoptosis, (iii) the use of cerebroside synthase inhibitors as tools for understanding the role of sphingolipids as mediators of cell cycle progression, renal disease, and stress responses, and (iv) the involvement of disrupted sphingolipid metabolism in animal disease and cellular deregulation associated with exposure to inhibitors of ceramide synthase and serine palmitoyltransferase, key enzymes in de novo sphingolipid biosynthesis. These findings illustrate how an understanding of the function of sphingolipids can help solve questions in toxicology and this is undoubtedly only the beginning of this story.

Amidohydrolases↗

PubMed1997

Managed care does not lower costs but may result in poorer outcomes for patients with gestational diabetes.

OBJECTIVE: Our purpose was to compare the costs of prenatal care and subsequent maternal and neonatal outcomes in patients with gestational diabetes cared for in an inner-city university hospital house staff clinic versus an inner-city managed care organization. STUDY DESIGN: A retrospective cohort study was conducted. The groups consisted of 115 patients with gestational diabetes who were cared for in a house staff clinic and a demographically similar group of 85 patients cared for in a neighborhood managed care organization. The groups were examined regarding baseline demographics, intensity of prenatal care, maternal and neonatal outcomes, and total cost of the provision of care. RESULTS: There was no difference between groups in the total cost of maternal-infant care. A larger percentage of patients in the house staff group saw the physician frequently. In contrast, patients cared for in the managed care organization underwent more tests of fetal well-being. There was a greater rate of neonatal macrosomia in the managed care organization group compared with the house staff group. CONCLUSIONS: Managed care does not decrease the cost of caring for patients with gestational diabetes but does lead to a greater rate of neonatal macrosomia, which may reflect poorer glucose control.

Adult↗

PubMed1997

Scanning tunnelling microscopy observation of cytochrome-c denaturation induced by bromopyrogal red on highly oriented pyrolytic graphite.

The denaturation of cytochrome-c (cyt-c) induced by bromopyrogal red (BPR) was studied by scanning tunnelling microscopy (STM) on the electrochemically pretreated highly oriented pyrolytic graphite (HOPG) surface. STM images reveal that denatured cyt-c molecules exist in variable states including aggregates, globular compact, partially unfolded and combined with BPR molecule. The apparently low image contrast of denatured cyt-c observed in this experiment comparing to that of native cyt-c molecules, and the relative low image contrast of the unfolded part comparing with the compact globular part, are ascribed to the unfavourable tunnelling paths for the conformational variations of denatured cyt-c molecules.

Animals↗

PubMed1997

Acute lymphoblastic leukaemia in childhood: cell proliferation without rest.

The percentage of non-cycling blast cells in children with untreated acute lymphoblastic leukaemia (ALL) was investigated by staining smears for statin, a nuclear protein specifically present in non-growing resting cells. Results were compared with purified normal CD34-positive progenitors. A low fraction of ALL and CD34-positive cells expressed statin (2.9 +/- 3.8% and 2.8 +/- 3.1%, respectively), the growth fraction assessed by staining for the nucleolar antigen p120 was 94% in both ALL and CD34-positive cell samples. From this analysis it can be concluded that the compartment of non-replicating cells in ALL as well as in normal CD34-positive precursor cells collected from peripheral blood is very small and that most cells are cycling.

Cell Division↗

PubMed1997

Importance of sphingolipids and inhibitors of sphingolipid metabolism as components of animal diets.

Sphingolipids are highly bioactive compounds that participate in the regulation of cell growth, differentiation, diverse cell functions, and apoptosis. They are present in both plant and animal foods in appreciable amounts, but little is known about their nutritional significance. Recent studies have shown that feeding sphingomyelin to female CF1 mice treated with a colon carcinogen (1,2-dimethylhydrazine) reduced the number of aberrant colonic crypt foci; longer-term feeding also affected the appearance of colonic adenocarcinomas. Therefore, dietary sphingolipids should be considered in studies of the relationships between diet and cancer. Sphingolipids have also surfaced as important factors in understanding the mechanism of action of a recently discovered family of mycotoxins, termed fumonisins. Fumonisins are produced by fungi commonly found on maize and a few related foods, and their consumption can result in equine leukoencephalomalacia, porcine pulmonary edema and a number of other diseases of veterinary animals and, perhaps, humans. A cellular target of fumonisins is the enzyme ceramide synthase, and disruption of sphingolipid metabolism by fumonisins has been established by studies with both cells in culture and animals that have consumed these toxic mycotoxins. These findings underscore the ways in which sphingolipids and agents that affect sphingolipid utilization should be given consideration in selecting animal diets for nutritional and toxicological studies.

Animal Feed↗

PubMed1997

Effect of sedative and hypnotic doses of propofol on the EEG activity of patients with or without a history of seizure disorders.

Propofol is alleged to possess both pro- and anticonvulsant properties, leading to controversy regarding its use in patients with a history of seizures. Since propofol is administered for both sedation and hypnosis, it is important to understand the effects of low (0.5-1.0 mg/kg) and high (2-2.5 mg/kg) doses of propofol on the electroencephalogram (EEG). In this study, the hemodynamic and EEG effects of cumulative doses of propofol from 0.5 to 2.5 mg/kg i.v. were studied in 30 neurosurgical patients with or without a history of seizure disorders. While continuously recording from scalp EEG electrodes (F3, F4, C3, C4, P3, P4, O1, and O2), propofol 0.5 mg/kg was infused intravenously over 20 s. The same dose of propofol was reinjected four times at 2-min intervals, until a total dose of 2.5 mg/kg had been administered. The number and average amplitude of the EEG waves were counted and measured manually, respectively, from 80 to 90 s after beginning the injection of each dose of propofol. After lower propofol doses (0.5-1 mg/kg), the number of beta-waves increased, while alpha- and theta-waves decreased significantly in all patients. However, with larger doses of propofol (total dose of 2-2.5 mg/kg), the number of beta-waves decreased and delta-waves appeared. The amplitudes of all EEG waves increased and were maintained at a higher level after administration of propofol. Spike (or sharp) waves appeared in 33% of the control patients and in 40% of the epileptic group after propofol 0.5 mg/kg and in 73% of the control and 67% of the epileptic patients after the 1.5-mg/kg dose. In the majority of patients, the spike waves disappeared when additional doses of propofol were administered. One patient in the epileptic group had an EEG-recorded and clinical grand mal seizure after propofol 1 mg/kg, but the seizure disappeared after an additional 0.5-mg/kg bolus dose was administered. The propofol-induced EEG changes appeared initially at the frontal and central EEG electrodes and subsequently at the other EEG electrodes. Overall, there were no significant differences in the spectrum of EEG changes between the two patient populations. It is concluded that propofol produces similar dose-dependent effects on EEG activity in patients with or without a history of seizure disorders. While induction of anesthesia with higher doses of propofol (> 1.5 mg/kg) in neurosurgical patients with well controlled seizure disorder is safe, smaller sedative doses should be administered with caution to epileptic patients.

Adult↗

PubMed1997

Genetic variation among strains of wild-type yellow fever virus from Senegal.

We have examined and compared at the molecular level three strains of wild-type yellow fever (YF) virus isolated from Senegal in 1927, 1953 and 1965, termed French viscerotropic virus, Rendu and Dak1279 respectively. Over the structural protein genes, Rendu differed from the other two strains by 8% at the nucleotide level. Rendu also differed antigenically, possessing a 'vaccine'-specific envelope (E) protein epitope (i.e. an epitope previously shown to be found on 17D and French neurotropic vaccine viruses only and not wild-type strains of YF virus). Consequently, we propose that at least two distinct genotypes of wild-type YF virus have been present in Senegal. Since Rendu virus was isolated from a fatal case of YF, it would indicate that the vaccine-specific epitope on the E protein is not associated with attenuation of the viscerotropism of wild-type YF virus.

Genotype↗

PubMed1997

The uterine myometrium is a target for increased levels of activin A during pregnancy.

Activin A is a dimeric protein hormone that regulates numerous cellular functions. A clear physiological role for this molecule in pregnancy is suggested by previous studies in the human, wherein activin A rises dramatically as women approach parturition. To determine whether the rodent is a suitable animal model for further studies of activin action during pregnancy, the serum concentration of activin A was measured in pregnant rats. Activin A was detected in the serum of pregnant rats, beginning on day 12, and the serum concentration rose progressively through gestation (22-fold) and dramatically (140-fold) in labor. The potential target tissues for circulating activin were then identified in two ways. First, iodinated activin was injected into pregnant rats, and the tissues targeted by labeled ligand were identified in vivo. A tissue targeted by activin A in the pregnant rat was the uterine myometrium. To determine the ligand specificity of the uterine myometrial cells, the uteri of pregnant rats were collected and analyzed by in situ ligand binding. 125I-activin A binding was specific for the uterus myometrium, and the ligand binding was competed by unlabeled activin A but not by inhibin A. This result suggests that the receptor in this tissue compartment is an activin-specific receptor. The production of abundant activin A and the ability of exogenous ligand to target the myometrium of the uterus provides a pathway by which activin could regulate uterine function during pregnancy.

Activins↗