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Biomedical subjects

F Wang

Publications and source records attributed to F Wang.

At least 415 records · Page 23Linked to original sources
PubMed1997

A case study on radon remedial measures in a family dwelling.

Field testing and computer modeling were used to study substructure ventilation, as a measure of controlling indoor radon in a house with a cellar. This is a common type of single family dwellings in areas of North England where radon is a problem. Testing carried out in the occupied house found that natural ventilation was not sufficient and both extract and supply ventilation were effective. Extract ventilation produced larger concentration reduction than supply at small air change rates. The house was also modeled by using a computer multi-zone air and pollutant movement simulation package. The simulated results were in good agreement with those measured for a wide range of conditions.

Air Pollution, Indoor↗
PubMed1997

Chronic nicotine treatment up-regulates alpha3 and alpha7 acetylcholine receptor subtypes expressed by the human neuroblastoma cell line SH-SY5Y.

Chronic exposure to nicotine has been reported to increase the number of nicotinic acetylcholine receptors (AChRs) in brain. The mechanism of up-regulation for the alpha4beta2 AChR subtype, which accounts for the majority of high affinity nicotine binding in mammalian brain, has previously been shown to involve a decrease in the rate of alpha4beta2 AChR turnover. Here, we report an investigation of the extent and mechanism of nicotine-induced up-regulation of alpha3 AChRs and alpha7 AChR subtypes expressed in the human neuroblastoma cell line SH-SY5Y. Up-regulation of human alpha3 AChRs and alpha7 AChRs, unlike alpha4beta2 AChRs, requires much higher nicotine concentrations than are encountered in smokers; the extent of increase of surface AChRs is much less; and the mechanisms of up-regulation are different than with alpha4beta2 AChRs. The mechanisms of up-regulation may be different for alpha3 AChRs or alpha7 AChRs. Chronic treatment with nicotine or carbamylcholine, but not d-tubocurarine, mecamylamine, or dihydro-beta-erythroidine, induced a 500-600% increase in the number of alpha3 AChRs but only a 30% increase in alpha7 AChRs. Chronic nicotine treatment did not increase affinity for nicotine or increase the amount of RNA for alpha3 or alpha7 subunits. The effect of nicotine on up-regulation of alpha7 AChRs was partially blocked by either d-tubocurarine or mecamylamine. The effect of nicotine treatment on the number of alpha3 AChRs was only slightly blocked by the antagonists d-tubocurarine, mecamylamine, or dihydro-beta-erythroidine at concentrations that efficiently block alpha3 AChR function. Most of the nicotine-induced increase in alpha3 AChRs was found to be intracellular. The alpha3 AChRs, which accumulate intracellularly, were shown to have been previously exposed on the cell surface by their susceptibility to antigenic modulation. The data suggest that chronic exposure to nicotine may induce a conformation of cell surface alpha3 AChRs that at least in this cell line are consequently internalized but not immediately destroyed.

Endocytosis↗
PubMed1997

Production of poly(3-hydroxybutyrate) by fed-batch culture of filamentation-suppressed recombinant Escherichia coli.

Recombinant Escherichia coli XL1-Blue harboring a high-copy-number plasmid containing the Alcaligenes eutrophus polyhydroxyalkanoate synthesis genes could efficiently synthesize poly(3-hydroxybutyrate) (PHB) in a complex medium containing yeast extract and tryptone but not in a defined medium. One of the reasons for the reduced PHB production in a defined medium was thought to be severe filamentation of cells in this medium. By overexpressing an essential cell division protein, FtsZ, in recombinant E. coli producing PHB, filamentation could be suppressed and PHB could be efficiently produced in a defined medium. A high PHB concentration of 149 g/liter, with high productivity of 3.4 g of PHB/liter/h, could be obtained by the pH-stat fed-batch culture of the filamentation-suppressed recombinant E. coli in a defined medium. It was also found that insufficient oxygen supply at a dissolved oxygen concentration (DOC) of 1 to 3% of air saturation during active PHB synthesis phase did not negatively affect PHB production. By growing cells to the concentration of 110 g/liter and then controlling the DOC in the range of 1 to 3% of air saturation, a PHB concentration of 157 g/liter and PHB productivity of 3.2 g of PHB/liter/h were obtained. For the scale-up studies, fed-batch culture was carried out in a 50-liter stirred tank fermentor, in which the DOC decreased to zero when cell concentration reached 50 g/liter. However, a relatively high PHB concentration of 101 g/liter and PHB productivity of 2.8 g of PHB/liter/h could still be obtained, which demonstrated the possibility of industrial production of PHB in a defined medium by employing the filamentation-suppressed recombinant E. coli.

Alcaligenes↗
PubMed1997

Poly(3-Hydroxybutyrate) Production with High Productivity and High Polymer Content by a Fed-Batch Culture of Alcaligenes latus under Nitrogen Limitation.

Alcaligenes latus has been known to produce poly(3-hydroxybutyrate) (PHB) in a growth-associated manner even under nutrient-sufficient conditions. However, the PHB content obtained by fed-batch culture was always low, at ca. 50%, which makes the recovery process inefficient. In this study, the effect of applying nitrogen limitation on the production of PHB by A. latus was examined. In flask and batch cultures, the PHB synthesis rate could be increased considerably by applying nitrogen limitation. The PHB content could be increased to 87% by applying nitrogen limitation in batch culture, which was considerably higher than that typically obtainable (50%) under nitrogen-sufficient conditions. In fed-batch culture, cells were first cultured by the DO-stat feeding strategy without applying nitrogen limitation. Nitrogen limitation was applied at a cell concentration of 76 g (dry cell weight)/liter, and the sucrose concentration was maintained within 5 to 20 g/liter. After 8 h of nitrogen limitation, the cell concentration, PHB concentration, and PHB content reached 111.7 g (dry cell weight)/liter, 98.7 g/liter, and 88%, respectively, resulting in a productivity of 4.94 g of PHB/liter/h. The highest PHB productivity, 5.13 g/liter/h, was obtained after 16 h.

Journal Article↗
PubMed1997

Modulation of CFTR chloride channels by calyculin A and genistein.

Modulation of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel by calyculin A and genistein was studied in Hi-5 insect cells infected with baculovirus containing the wild-type CFTR cDNA. In cell-attached patches, CFTR channel activity was not observed until stimulated by forskolin in 90% of the cells, suggesting a low level of basal adenosine 3',5'-cyclic monophosphate activity. Calyculin A, a specific inhibitor of phosphatases 1 and 2A, increased forskolin-induced CFTR activity by 17.2-fold. CFTR channel currents did not deactivate completely after forskolin was withdrawn in the continued presence of calyculin A. Genistein enhanced forskolin-induced CFTR activity by 44.9-fold but could neither activate the CFTR by itself nor prevent complete deactivation on removal of forskolin. Genistein together with calyculin A could adequately prevent deactivation of CFTR currents. Noise analysis of the macroscopic CFTR currents revealed significant differences in the mean current-variance-relationship and the corner frequency of the noise spectra between currents activated by forskolin plus genistein and those activated by forskolin plus calyculin A. Furthermore, genistein enhanced CFTR activity induced by saturating concentrations of forskolin and calyculin A. Our results suggest that genistein and calyculin A modulate the CFTR by different mechanisms and that genistein might inhibit calyculin A-insensitive dephosphorylation of the CFTR.

3T3 Cells↗
PubMed1997

Genistein potentiates wild-type and delta F508-CFTR channel activity.

Effects of genistein on wild-type (wt) and delta F508-cystic fibrosis transmembrane conductance regulator (CFTR) were studied in NIH/3T3 cells stably transfected with wt or mutant CFTR cDNA. As measured by I- efflux, half-maximal concentration of agonist (K1/2) for forskolin-dependent activation was greater for delta F508-CFTR than wt-CFTR. Genistein decreased the K1/2 for both forms of the channel and increased the maximal activity of delta F508-CFTR by 3.7-fold. In cell-attached patches, 10 microM forskolin induced minimal delta F508-CFTR activity with characteristic prolonged closed times (estimated time constant, > 30 s). Genistein increased the forskolin-induced macroscopic currents of wt-CFTR and delta F508-CFTR by 3- and 19-fold, respectively. Variance analysis suggested that in the presence of forskolin and genistein the open probabilities (Po) of wt- and delta F508-CFTR were identical. In single-channel studies, at maximal adenosine 3',5'-cyclic monophosphate (cAMP) stimulation, genistein increased the Po of wt-CFTR by prolonging the open time, but, at submaximal cAMP stimulation, the Po was increased by prolonging the open time and shortening the closed time. In excised patches with CFTR channels preactivated in the cell-attached mode, genistein increased ATP-dependent wt- and delta F508-CFTR current about twofold by prolonging the open time. Our results thus suggest that phosphorylation-dependent activation of delta F508-CFTR is defective and that genistein corrects this defect at least in part by binding to the CFTR protein.

3T3 Cells↗
PubMed1997

Systemic lupus erythematosus in Malaysia: a study of 539 patients and comparison of prevalence and disease expression in different racial and gender groups.

The aims of this study were to examine the clinical and laboratory features of Malaysian patients with systemic lupus erythematosus (SLE) and to identify any difference in disease expression between the different genders and among the three major ethnic groups of Malaysia. Retrospective analysis of all patients with SLE admitted to and followed-up at University Hospital Kuala Lumpur from 1974-90 was undertaken. Ethnic Chinese had the highest prevalence of SLE compared to other ethnic groups. There was a high incidence of renal disease, 74% of patient had significant proteinuria and half of these had associated nephrotic syndrome. Indian patients had significantly less incidence of skin manifestation compared to other racial groups. No difference in disease expression was detected between the ethnic Chinese and Indians and between the male and female patients. The overall 5 y and 10 y survival rates were 82% and 70% respectively. Indian patients had the poorest survival rates. Survival rates are similar among the Chinese and Malay patients. Our findings are in broad agreement with those previously reported.

Adolescent↗
PubMed1997

Estrogenic activity of a dieldrin/toxaphene mixture in the mouse uterus, MCF-7 human breast cancer cells, and yeast-based estrogen receptor assays: no apparent synergism.

The estrogenic activity of dieldrin, toxaphene, and an equimolar mixture of both compounds (dieldrin/toxaphene) was investigated in the 21-day-old B6C3F1 mouse uterus, MCF-7 human breast cancer cells, and in yeast-based reporter gene assays. Treatment of the animals with 17beta-estradiol (E2) (0.0053 kg/day x3) resulted in a 3.1-, 4.8-, and 7.8-fold increase in uterine wet weight, peroxidase activity, and progesterone receptor binding, respectively. In contrast, treatment with 2.5, 15 and 60 micromol/kg (x3) doses of toxaphene, dieldrin, or dieldrin/toxaphene (equimolar) did not significantly induce a dose-dependent increase in any of the E2-induced responses. The organochlorine pesticides alone and the binary mixture did not bind to the mouse uterine estrogen receptor (ER) in a competitive binding assay using [3H]E2 as the radioligand. In parallel studies, estrogenic activities were determined in MCF-7 cells by using a cell proliferation assay and by determining induction of chloramphenicol acetyl transferase (CAT) activity in MCF-7 cells transiently transfected with plasmids containing estrogen-responsive 5'-promoter regions from the rat creatine kinase B and human cathepsin D genes. E2 caused a 24-fold increase in CAT activity in MCF-7 cells transiently transfected with creatine kinase B and a 3.8-fold increase in cells transiently transfected with the human cathepsin D construct. Treatment of MCF-7 cells with dieldrin, toxaphene, or an equimolar mixture of dieldrin plus toxaphene (10(-8)-10(-5) M) did not significantly induce cell proliferation or CAT activity in the transient transfection experiment with both plasmids. The relative competitive binding of the organochlorine pesticides was determined by incubating MCF-7 cells with 10(-9) M [3H]E2 in the presence or absence of 2 x 10(-7) M unlabeled E2 (to determine nonspecific binding), toxaphene (10(-5) M), dieldrin (10(-5) M), and equimolar concentrations of the dieldrin plus toxaphene mixture (10(-5) M). The binding observed for [3H]E2 in the whole cell extracts was displaced by unlabeled E2, whereas the organochlorine pesticides and binary mixture exhibited minimal to nondetectable competitive binding activity. E2 caused a 5000-fold induction of beta-galactosidase (beta-gal) activity in yeast transformed with the human ER and a double estrogen responsive element upstream of the beta-gal reporter gene. Treatment with 10(-6)-10(-4) M chlordane, dieldrin, toxaphene, or an equimolar mixture of dieldrin/toxaphene did not induce activity, whereas 10(-4) M endosulfan caused a 2000-fold increase in beta-gal activity. Diethylstilbestrol caused a 20-fold increase in activity in yeast transformed with the mouse ER and a single estrogen responsive element upstream of the beta-gal reporter gene. Dieldrin, chlordane, toxaphene, and endosulfan induced a 1.5- to 4-fold increase in activity at a concentration of 2.5 x 10(-5) M. Synergistic transactivation was not observed for any equimolar binary mixture of the pesticides at concentrations of either 2.5 x 10(-5) M or 2.5 x 10(-4) M. The results of this study demonstrate that for several estrogen-responsive assays in the mouse uterus, MCF-7 human breast cancer cells, and yeast-based reporter gene assays, the activities of both dieldrin and toxaphene were minimal, and no synergistic interactions were observed with a binary mixture of the two compounds.

Animals↗
PubMed1997

The caudal homeobox protein cdx-2/3 activates endogenous proglucagon gene expression in InR1-G9 islet cells.

The proglucagon gene is expressed in a highly cell-specific manner in islet and enteroendocrine cells. DNA sequences within the proximal proglucagon G1 promoter region bind the homeobox protein cdx-2/3, and cdx-2/3 activates the proglucagon promoter in fibroblasts. We show here that cdx-2/3 activates the proglucagon promoter in both islet (InR1-G9) and enteroendocrine (STC-1 and GLUTag) cell lines. Furthermore, transfected cdx-2/3 increased the levels of endogenous proglucagon mRNA transcripts in both transient and stable transfections of InR1-G9 islet cells. The cdx-2/3-dependent induction of endogenous proglucagon mRNA transcripts in stable islet lines was associated with a corresponding increase in the transcriptional activity of proglucagon promoter-luciferase plasmids. An amino-terminally truncated cdx-2/3 derivative containing the homeodomain and carboxy-terminal region of the molecule inhibited both the cdx-2/3 activation of the proglucagon promoter and the induction of endogenous proglucagon mRNA transcripts. These observations demonstrate that cdx-2/3, acting through the proximal G1 element, is a major transcriptional determinant of cell-specific proglucagon gene expression in pancreatic islet cells.

Animals↗
PubMed1997

Racial variations in treatment for glaucoma and cataract among Medicare recipients.

PURPOSE: To identify the location of barriers to treatment for glaucoma and cataract among African-American Medicare beneficiaries. METHODS: We examined the receipt of eye care in general and care for glaucoma and cataract in particular among black and white Medicare beneficiaries using 1991 Medicare physician claims data. Racial differences in treatment for glaucoma and cataract were examined both for the Medicare population as a whole and for identified eye care users. The results were compared to the expected value of black-white difference based on population prevalence data for each specific condition. RESULTS: Thirty percent of black beneficiaries and 45% of white Medicare beneficiaries used eye care services in 1991. After adjusting for the expected difference in prevalence, black beneficiaries were half as likely to be surgically treated for glaucoma compared to white beneficiaries, and 80% as likely for cataract. When the analysis was restricted to those using eye care services, blacks continued to have lower than expected rates of treatment for glaucoma (observed RR = 3.2, 95% confidence interval = 3.1-3.4 vs an expected RR of 4.3, 95% confidence interval = 3.5-5.4), but a higher rate of treatment for cataract (RR = 1.2, 95% confidence interval = 1.2-1.3). Among those with physician-diagnosed glaucoma and cataract, blacks were more likely to undergo surgical treatment for these conditions than whites (RR = 1.5 for glaucoma, 95% confidence interval = 1.4-1.5; RR = 1.2 for cataract, 95% confidence interval = 1.2-1.3). CONCLUSION: Barriers to treatment for glaucoma and cataract among black Medicare beneficiaries involve primarily limitations in access to the eye care system. The undertreatment for glaucoma among black beneficiaries was reduced, but not eliminated, after removing the effect of unequal access to the eye care system.

Black or African American↗
PubMed1997

[The role of adenosine in the early stage of anoxia of hippocampal slices and its mechanisms].

The role of adenosine in reversible inhibition of synaptic function during the early stage of anoxia and its mechanisms were investigated with extracellular recording technique in rat hippocampal slices. The results showed that acute anoxia led to the reversible inhibition of synaptic function, which is similar to the response to addition of high concentration of exogenous adenosine. The reversible inhibition could be suppressed by adenosine A1 receptor antagonist CPT and potassium channel blocker 4-AP, whereas TEA and ATP-sensitive potassium channel blocker glipzide had no effect. These results suggest that during the early stage of anoxia, the enhanced release of endogenous adenosine can inhibit the synaptic transmission by activating 4-AP-sensitive potassium channels via A1 receptors and thus play a role in protenction against anoxic injury. ATP-sensitive potassium channels may not be involved in the mechanisms of adenosine action.

Adenosine↗
PubMed1997

[Role of Na+/Ca2+ exchange blocker in rat hippocampal injury during anoxia].

Effects of Na+/Ca2+ exchange blocker, Benzamil, on rat hippocampal slices and on cultured hippocampal neuronal [Ca2+]i (intracellular free Ca2+ concentration) during anoxia were investigated by means of microelectrode recording technique and laser scanning confocal microscope respectively. The results showed that the PV sustained time of hippocampal slices pretreated with Benzamil (50 mumol) after anoxia was markedly longer than that of control, suggesting that inhibition of Na+/Ca2+ exchange can delay the irreversible injury to hippocampal cells. Moreover, by using a confocal microscope we found that acute anoxia induced a rapid increase of [Ca2+]i in hippocampal neurons and this could be significantly attenuated by 20 mumol Benzamil. All these results indicate that Na+/Ca2+ exchanger is involved in the anoxic injury to rat hippocampus and it may be one of the major ways leading to the anoxia-induced [Ca2+]i increase of hippocampal neurons.

Amiloride↗
PubMed1997

[Anoxia-induced c-fos expression of cultured rat hippocampal neurons and effect of recombinant human interleukin-1 beta].

Effects of recombinant human interleukin-1 beta (rhIL-1 beta) on the c-fos expression of cultured rat hippocampal neurons in vitro induced by anoxia were studied by using an immunohistochemical method. The results showed that the percentage and the mean optical density of the Fos-positive neuronal nuclei in cultured hippocampal neurons increased markedly as anoxia prolonged, while those in hippocampal neurons pretreated with rhIL-1 beta were significantly lower than those of control. The results indicate that anoxia can induce c-fos expression of cultured rat hippocampal neurons in vitro and this can be inhibited by rhIL-1 beta, suggesting that rhIL-1 beta may protect neurons from damage in a certain degree during anoxia.

Animals↗
PubMed1997

[Bicuculline stimulates the release of adrenocorticotropin (ACTH) from rat anterior pituitary quarters].

The effect of gama-aminobutyric acid (GABA) on release of adrenocorticotropin (ACTH) from anterior pituitary quarters of male SD rats adrenalectomized for 96 hrs was investigated using the perfusion technique in vitro. Application of bicuculline (10(-6)mol/L), a specific GABA-A antagonist, resulted in a significant release of ACTH from perfused anterior pituitary quarters. But the same concentration of bicuculline had no effect on the release of ACTH from dispersed anterior cells of ADX rats in vitro. Taken together, these results suggest that GABA may play an important inhibitory role on ACTH secretion from pituitary in adrenalectomized rats.

Adrenalectomy↗
PubMed1997

[Effect of dietary VE on the contents of salivary acid and MDA in RBC membrane].

Vitamin E can protect membrane from the damage of lipid peroxidation, Salivary acid is the residual of carbohydrate on the membrane. To evaluate the effect of dietary VE on salivary acid, the contents of MDA and salivary acid of erythrocyte (RBC) membrane of rats were measured. The rats were fed with different amounts of dietary VE and stayed at different temperatures. The results revealed that the content of salivary acid of RBC membrane reduced markly (P < 0.01) and the content of MDA of RBC membrane was stable (P > 0.05) after the rats were exposed to cold for 10 days. High dietary VE intake increased the content of salivary acid of RBC membrane (P < 0.01). There was no correlation between the content of salivary acid and MDA of RBC membrane. It suggested that dietary VE could raise the content of salivary acid in RBC membrane, but it can not be explained by the reduction of LPO.

Animals↗
PubMed1997

[The use of microwave for immunohistochemical technology in forensic pathology].

A microwave oven (MWO) of National brand was applied for Labeled Streptavidin Biotin immunohistochemical staining (LSAB method) on autopsy materials of 20 cases to detect 10 kinds of antigen of heart and brain: The keys to manipulate MWO as follows: (1) Recovery of antigen: submerge sections in 0.01M citrate buffer (pH 6.0), turn MWO to the position of DEF (210W) for 10 min, reaching temperature 92 degrees C-98 degrees C. (2) add normal serum, first antibody, second biotinylated antibody and streptavidin complex, then turn MWO to the position of LOW (70W) for 5 min, reaching temperature 20 degrees C-37 degrees C. Other steps were the same as the standards. Results showed: MWO can recover the destroyed or covered antigen, improve positive staining degree, reduce background's stain and shorten staining time.

Antigens↗