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Biomedical subjects

G Bai

Publications and source records attributed to G Bai.

At least 19 recordsLinked to original sources
PubMed2001

Biosurfactant-enhanced solubilization of NAPL mixtures.

Remediation of nonaqueous phase liquids (NAPLs) by conventional pump-and-treat methods (i.e., water flushing) is generally considered to be ineffective due to low water solubilities of NAPLs and to mass-transfer constraints. Chemical flushing techniques, such as surfactant flushing, can greatly improve NAPL remediation primarily by increasing the apparent solubility of NAPL contaminants. NAPLs at hazardous waste sites are often complex mixtures. However, the equilibrium and nonequilibrium mass-transfer characteristics between NAPL mixtures and aqueous surfactant solutions are not well understood. This research investigates the equilibrium solubilization behavior of two- and three-component NAPL mixtures (containing akylbenzenes) in biosurfactant solutions. NAPL solubilization is found to be ideal in water (i.e., obeys Raoult's Law), while solubilization in biosurfactant solutions was observed to be nonideal. Specifically, the relatively hydrophobic compounds in the mixture experienced solubility enhancements that were greater than those predicted by ideal enhanced solubilization theory, while the solubility enhancements for the relatively hydrophilic compounds were less than predicted. The degree of nonideality is shown to be a nonlinear function of the NAPL-phase mole fraction. Empirical relationships based on the NAPL-phase mole fraction and/or micelle-aqueous partition coefficients measured in single-component NAPL systems are developed to estimate values for the multicomponent partition coefficients. Empirical relationships that incorporate both the NAPL-phase mole fraction and single-component partition coefficients yield much improved estimates for the multicomponent partition coefficient.

Benzene Derivatives↗
PubMed2000

Molecular basis of NMDA receptor-coupled ion channel modulation by S-nitrosylation.

Several ion channels are thought to be directly modulated by nitric oxide (NO), but the molecular basis of this regulation is unclear. Here we show that the NMDA receptor (NMDAR)-associated ion channel was modulated not only by exogenous NO but also by endogenous NO. Site-directed mutagenesis identified a critical cysteine residue (Cys 399) on the NR2A subunit whose S-nitrosylation (NO+ transfer) under physiological conditions underlies this modulation. In cell systems expressing NMDARs with mutant NR2A subunits in which this single cysteine was replaced by an alanine, the effect of endogenous NO was lost. Thus endogenous S-nitrosylation can regulate ion channel activity.

Animals↗
PubMed2000

[Study on hepatitis B virus infection status in placentas of hepatitis B surface antigen positive pregnant women during middle and late period of pregnancy].

OBJECTIVE: To investigate Hepatitis B Virus (HBV) infection status in placentas of Hepatitis B Surface Antigen (HBsAg) positive pregnant women during middle and late period of pregnancy. METHODS: One hundred and sixty-seven placentas from HBsAg positive pregnant women were collected, including 158 term placentas and 9 aborted second-trimester placentas. HBsAg and hepatitis B core antibody (HBcAg) in placental cytotypes were detected by immunohistochemistry. RESULTS: Of the 158 term placentas, HBV infection rates in decidual cells (DC), trophoblastic cells (TC), villous mesenchymal cells (VMC) and villous capillary endothelial cells (VCEC) were 66.46% (105/158), 58.23% (92/158), 27.22% (43/158) and 12.66% (20/158), respectively. The HBV infection rates gradually decreased from maternal side to fetal side of placentas. Both HBsAg and HBcAg were mainly located in the cytoplasm of infected cells. The positive cells were mostly in focal distribution. One out of 9 aborted second-trimester placentas was infected. CONCLUSIONS: HBV infection was found in different cells of term placentas. The positive rates for HBsAg and HBcAg in placentas were gradually decreased from maternal side to fetal side. The positive rate was low in aborted second-trimester placentas.

Adult↗
PubMed1999

Treatment of severe electrical burns.

In summary, electrical injury is a typical type of burn injury with a unique mechanism of systemic and local damage. Resuscitation is more complex in critical patients than that of thermal injury. Local management is more difficult, which could be eventually accomplished by sequential procedures of debridement and operation. Although the modern trend of performing early debridement and operation might be promising, traditional experiences are still being used in clinical care. Progress in clinical management has brought about an improvement in therapeutic outcome, resulting in a decrease of amputation rate and reduced disability. Some typical types of electrical injury demand special treatment, which might prove to be effective. Close observation and timely treatment of the injury itself and related complications will be lifesaving in caring for critical electrical injury. Some special therapeutic measures would be indicated and might be fruitful in proving their efficacy. New measures aimed at theoretical problems will be promising if electroporation could be effectively treated.

Accidents, Occupational↗
PubMed1999

Proteasome-dependent cyst formation and stage-specific ubiquitin mRNA accumulation in Entamoeba invadens.

Proteases play an important role in the pathogenic mechanisms and differentiation events of protozoan parasites; the proteasome/ubiquitin system is essential for maintaining the differentiation state of many cell types. A single input of the specific inhibitor of proteasomes, lactacystin, prevented encystation of the protozoan parasite Entameoba invadens, whereas a cysteine protease inhibitor, E64, only delayed encystation. The ameba target of lactacystin was purified and it displayed the features typical of eukaryotic 20S proteasome complexes. In addition, transcripts encoding ubiquitin were detectable in trophozoites stage cells, disappeared immediately following transfer of amoebae to encystation induction medium, and reappeared at the same time during encystation as other encystation-specific transcripts. These results demonstrate that proteasome function is required during the conversion of the disease-causing trophozoite into the infectious cyst stage of Entamoeba parasites, and that ubiquitin transcript levels undergo an unusual decrease during the early stages of this differentiation process.

Acetylcysteine↗
PubMed1999

Immunocytochemical localization of histamine in enterochromaffin-like (ECL) cells in rat oxyntic mucosa: a transmission electron microscopy study using monoclonal antibodies and conventional glutaraldehyde-based fixation.

Histamine (HA), contained in the enterochromaffin-like (ECL) cells of the gastric mucosa in animals, plays an important role in gastric acid secretion, although methods for its exact morphological localization are still lacking. We used a pre-embedding indirect immunoperoxidase approach to define the fine structural localization of HA in rat oxyntic mucosa that was fixed with a glutaraldehyde-based fixative and HA monoclonal antibodies (MAbs AHA-1 and 2). Transmission electron microscopy showed that the peroxidase endproduct not only was concentrated in the cores of cytoplasmic granules but also was distributed to a high degree in the cytoplasm peripheral to the granules of the ECL cells. These results suggest that in ECL cells HA is enzymatically synthesized in the cytoplasm, then is transported and stored in the cores of the granules before its release from the basal lamina. The present HA immunoelectron microscopic method with MAbs would be applicable more generally to the ultrastructural identification of HA-containing cells.

Animals↗
PubMed1998

Synergistic activation of the N-methyl-D-aspartate receptor subunit 1 promoter by myocyte enhancer factor 2C and Sp1.

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptor plays important roles in neuronal development, plasticity, and cell death. NMDA receptor subunit 1 (NR1) is an essential subunit of the NMDA receptor and is developmentally expressed in postnatal neurons of the central nervous system. Here we identify on the NR1 promoter a binding site for myocyte enhancer factor 2C (MEF2C), a developmentally expressed neuron/muscle transcription factor found in cerebrocortical neurons, and study its regulation of the NR1 gene. Co-expression of MEF2C and Sp1 cDNAs in primary neurons or cell lines synergistically activates the NR1 promoter. Disruption of the MEF2 site or the MEF2C DNA binding domain moderately reduces this synergism. Mutation of the Sp1 sites or the activation domains of Sp1 protein strongly reduces the synergism. Results of yeast two-hybrid and co-immunoprecipitation experiments reveal a physical interaction between MEF2C and Sp1 proteins. The MEF2C DNA binding domain is sufficient for this interaction. Dominant-negative MEF2C interferes with expression of NR1 mRNA in neuronally differentiated P19 cells. Growth factors, including epidermal growth factor and basic fibroblast growth factor, can up-regulate NR1 promoter activity in stably transfected PC12 cells, even in the absence of the MEF2 site, but the Sp1 sites are necessary for this growth factor regulation, suggesting that Sp1 sites may mediate these effects.

Binding Sites↗
PubMed1998

Single-stranded DNA-binding proteins and neuron-restrictive silencer factor participate in cell-specific transcriptional control of the NMDAR1 gene.

Our previous studies revealed that a proximal region of the N-methyl-D-aspartate receptor 1 (NMDAR1) promoter is important for cell-type-specific expression. We have now explored the contributions of several regulatory elements to this specificity. Deletion of the neuron-restrictive silencer element partially relieved the suppression of promoter activity in C6 glioma and HeLa cells. An overlapping G(C/G)G/tandem Sp1-containing region crucial for both basal and nerve growth factor (NGF)-regulated promoter activity specifically bound nuclear proteins on its purine-rich sense strand. A faster migrating complex, single-stranded binding protein complex 1 (SBPC1), was highly enriched in HeLa cells, whereas a slower migrating complex, SBPC2, was enriched in PC12 cells. A high ratio of 2/1 complex correlated with a high level of promoter activity. NGF treatment of PC12 cells reduced SBPC1 but increased SBPC2. Competition experiments showed that the SBPC1 binding required a dG4 sequence and the SBPC2 needed a core of TG3A plus a 5'-flanking sequence. Single-stranded DNA encompassing TG3A and/or dG4 specifically suppressed cotransfected NMDAR1 promoter activity. UV cross-linking studies indicated that a 31.5-kDa protein mainly formed SBPC1, whereas SBPC2 contained several larger proteins. Our results suggest that neuron-restrictive silencer factor and single-stranded DNA-binding proteins may both play a role in cell-type specificity of the NMDAR1 gene, and the latter may also be involved in basal and NGF-regulated activity.

Animals↗
PubMed1998

Immunoelectron microscopic study for polyamines.

The polyamines (PAs) are ubiquitous polycationic metabolites in eukaryotic and prokaryotic cells and are believed to be intimately involved in the regulation of DNA, RNA, and protein biosynthesis, the exact function of which remains unclear, mainly because of a lack of knowledge of PA subcellular localization. In this study, using immunoelectron microscopy, we have demonstrated that PAs are predominantly located on free and attached ribosomes of the rough endoplasmic reticulum in the neurons of the lateral reticular nucleus of rat medulla oblongata. The nuclei, axons, and nerve endings were devoid of PA. This suggests that PAs are one of the components of biologically active ribosomes, being closely involved in the translation processes of protein biosynthesis.

Animals↗
PubMed1998

Enzyme immunoassay for a characteristic protein in the animal crude drug lumbricus.

A new method was developed to measure the content of a Lumbricus component in a traditional Chinese medicine (TCM). An antiserum specific to Lumbricus was elicited in a rabbit following immunization with a suspension of Lumbricus fragments. A characteristic antigen protein, 70 kDa, was found in Lumbricus and was purified almost to singleness using a column chromatography series of gel filtration and DEAE-Sepharose. A selected antibody enzyme immunoassay (SAEIA) was developed using the antiserum and the purified 70 kDa protein as a solid-phase antigen. The SAEIA was specific to Lumbricus species, and showed no cross-reaction with any crude drugs other than Lumbricus. This SAEIA detected 70 kDa protein in the amount of 10 ng/ml with excellent reproducibility (coefficient of variation=3.0%) and an EC50 of 0.24 microg/ml. Using this assay, Lumbricus levels were easily determined in a Lumbricus-based TCM Kazecoll, but not in the control Kazecoll (Kakkonto) prepared without Lumbricus. The SAEIA for 70 kDa protein was simple, accurate, reproducible and may provide a general analytical method for the quality control of Lumbricus-based TCMs.

Animals↗
PubMed1997

Polyamine-like immunoreactivity in rat neurons.

The localization of polyamine (PA) pools in motor, sensory, and autonomic neurons and in the nerve cells of the hypothalamo-hypophysial system of rats was examined by immunocytochemical method using the monoclonal antibody ASPM-29 specific to spermine (Spm) and spermidine (Spd) fixed in situ. Strong PA immunoreactivity was found in the cytoplasm and dendrites of the large perikaryon of motor neurons in the anterior spinal column, in the Purkinje cells of the cerebellum, in the pyramidal cells of the cerebrum, in the nerve cells of the paraventricular and supraoptic nuclei in the hypothalamus, and in the nerve cells of the spinal and autonomic ganglions. No PA immunoreactivity was seen in the nucleus and nerve terminals of the neurons. The PA immunoreactivities in the motor and sensory neurons were characterized by clustered masses and blocks of immunoreactive cells. Irrespective of location, small and medium-sized neurons were weakly PA-positive. The glia cells, some stellite cells, and Schwann cells were almost completely PA-negative. These results may suggest that in neurons PAs are not transported axonally, but are located in conjunction with Nissl bodies (the rough endoplasmic reticulum), specified as sites for protein synthesis within cells.

Animals↗
PubMed1997

Nerve growth factor up-regulates the N-methyl-D-aspartate receptor subunit 1 promoter in PC12 cells.

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptor plays important roles in synaptic plasticity, the induction of long term potentiation, and excitotoxicity. Mechanisms governing the regulation of expression of its subunit genes remain largely unknown. The promoter of the essential subunit of the NMDA receptor heteromer, NMDAR1, contains DNA binding elements recognized by the nerve growth factor-inducible/early growth reaction factor (NGFI/Egr) family of transcription factors that are rapidly induced by neurotrophins, such as nerve growth factor (NGF). This study examined the effect of NGF on the activity of the N-methyl-D-aspartate receptor subunit 1 (NMDAR1) promoter/luciferase reporter constructs in PC12 cells, which contain the high affinity TrkA receptor for NGF and the low affinity p75(NTR) receptor for neurotrophins. NGF up-regulated the activity of the NMDAR1 promoter by 3-4-fold in a time- and dose-dependent manner. 5' deletional analysis of the promoter indicated that the responsive element(s) resides in the proximal region containing GSG and Sp1 sites. Mutational analysis of these sites revealed that both were important for NGF regulation. Transient expression of Egr-1 increased activity of the wild type promoter but failed to increase activity of a GSG mutant promoter. Other neurotrophins did not activate the promoter, while K-252a inhibited the action of NGF. These results suggest that the NGF effect is mediated by the high affinity NGF receptor, Trk A and that neurotrophin binding to the low affinity neurotrophin receptor, p75(NTR), alone does not affect the promoter activity. Our results suggest that NGF is able to up-regulate the activity of the NMDAR1 promoter and may play a role in controlling the expression levels of NMDA receptors.

Animals↗
PubMed1997

Isolation and characterization of phenoloxidase from egg masses of the gastropod mollusc, Biomphalaria glabrata.

Previous studies have shown that phenoloxidase activity is present in the albumen gland and egg masses of Biomphalaria glabrata, and its potential role in egg formation in this snail has been proposed. In the present study, a phenoloxidase enzyme has been isolated from the supernatant of egg mass homogenates using a combination of hydrophobic interaction chromatography and gel filtration high-performance liquid chromatography (GF-HPLC). The isolated phenoloxidase eluted as a single peak of activity upon GF-HPLC (representing a 132-fold purification) and subsequently was detected as a single band with an estimated molecular mass of 35 kDa by SDS-PAGE analysis. Phenylthiourea-inhibitable mono- and diphenoloxidase activities were demonstrated for the isolated enzyme suggesting that both enzyme activities are associated with a single, tyrosinase-type molecule.

Ammonium Sulfate↗
PubMed1997

Development and application of a sandwich enzyme immunoassay for Glycyrrhizae Radix protein (GRP) using monoclonal antibodies.

We have developed mouse monoclonal antibodies (anti-GRP mAb-1-5, all IgG1 sub-isotype mAbs) against Glycyrrhizae Radix protein (GRP), which was recently determined to be a marker protein of Glycyrrhizae Radix (GR). Among these, anti-GRP mAb-1 and 2 were found to recognize different epitopes on the GRP molecule, as demonstrated by ELISA analysis, and were used for the development of a sandwich enzyme immunoassay (SEIA) for GRP in traditional Chinese medicines (TCMs). The SEIA was based on the principle of binding an analyte to anti-GRP mAb2 coated on polystyrene microtiter wells, followed by immunoreaction with biotinylated anti-GRP mAb1 and horseradish peroxidase-streptavidin. The SEIA was specific to GRP in GRs, and showed no cross-reaction with any Leguminosae crude drugs other than GRs. This SEIA detected GRP with excellent reproducibility (coefficient of variation=5.9%), an EC50 of 11.5 ng/well and a detection limit of 0.1 ng/well. The present SEIA was about 10-times more sensitive in detecting GRP than the selected antibody enzyme immunoassay (SAEIA) for GRP previously developed using an antiserum to GR itself. Also, the SEIA has such a low assay background that it allowed us to detect a low concentration of GRP in Kyuki-tyoketsu-in-daiichi-kagen (KTIDK), a TCM consisting of only 2.7% GR. The GRP SEIA was simple, accurate, reproducible and may provide a general analytical method for the quality control of GR-based TCMs.

Animals↗
PubMed1997

A general enzyme immunoassay for the licorice root component contained in traditional Chinese medicines.

The development and application of a new enzyme immunoassay for general assay of the Glycyrrhizae radix (GR) component in Chinese traditional medicines is described. Three commercial GR-based medicines, Tohoku kanzo (GRTK), Seihoku Kanzo (GRSEK) and Sinkyo kanzo (GRSK) were used as GR specimens. Anti-GRSK serum was elicited from rabbits immunized with GRSK fragments. The presence of common proteins as specific antigens of GR was first established by Western blot analysis of extracts of GRSK, GRSEK or GRTK using anti-GRSK. The specific antigens were applied to develop an ELISA for the assay of GR extract. Anti-GRSK was put in competition with a sample or standard GR extract and immobilized GRSK components in microtiter plate wells. The proportion of antibody binding to the solid-phase GRSK component was detected using an enzyme-labeled second antibody. The ELISA method was specific to GRSK extract and showed low sensitivity for the assay of GRTK extract. The technique of selected antibody enzyme immunoassay (SAEIA) was applied to develop a sensitive general assay method. Solid-phase GRTK extract, rather than immobilized GRSK extract, was used in the SAEIA. The SAEIA possessed the same quantitative working range of between 1 and 100 micrograms/ml for the assay of each extract of GRTK, GRSK and GRSEK. The SAEIA was successful in the detection and quantitative measurement of GR component contents in Chinese traditional medicines.

Animals↗
PubMed1997

Application of a licorice root specific protein to a general method for the assay of licorice root components in traditional Chinese medicines.

A new fuzzy immunoassay method generally applied to ten Glycyrrhizae Radix (GR) preparations of four different botanical origins was studied. Four kinds of antisera were elicited in rabbits immunized with GRs of different botanical origins. The presence of the characteristic GR protein (GRP) was shown using Western blot analyses and selected antibody enzyme immunoassay (SAEIA) methods. A GRP was isolated from one of the GR specimens which was selected using SAEIA methods. The isolated GRP was heated to reduce its binding activity to an anti-GR serum. A new fuzzy SAEIA method generally applicable for assay of the extract of the ten GR specimens was developed using heat-treated GRP as the solid-phase antigen. The fuzzy SAEIA method was successfully applied for the detection and quantitative analysis of the GR component contained in traditional Chinese medicines.

Animals↗
PubMed1997

Phenoloxidase activity in the reproductive system of Biomphalaria glabrata: role in egg production and effect of schistosome infection.

Infection by larval trematodes often causes a cessation of egg production in its molluscan intermediate host and is referred to as parasitic castration. Because phenoloxidase (PO) has been shown to be involved in egg formation in other invertebrate species, we investigated the role of PO in normal egg production in the snail, Biomphalaria glabrata, and the effects of Schistosoma mansoni infection on the PO pathway in this snail. Our data showed that PO activity in the albumen gland (AG) is initially expressed when snails reach a size of approximately 8 mm in shell diameter and continues to increase as snails grow, indicating a developmental link between snail size and AG PO expression. Egglaying was also shown to be coincidental with the onset of PO expression in the AG, thereby supporting a direct association between PO activity and egg production. In addition, exposure of snails to diethyldithiocarbamate (DDC), a PO inhibitor, affected normal in vivo egg production, as evidenced by a significant decrease in the numbers of eggs laid in DDC-treated groups compared to nontreated groups. Normal resumption of egg-laying activity in treated snails following withdrawal of the drug indicated that inhibition was reversible. Taken together, the results of our developmental and DDC-exposure studies provide strong support for a crucial role of PO in normal egg production in this animal. Finally, AG PO activities of infected and uninfected control snails were measured over the course of S. mansoni infection. Our results showed that both total and specific enzyme activities in the AG of infected snails were significantly decreased at 28 and 33 days postinfection (PI) when compared to those of control snails. Results of subsequent experiments assessing the effects of larval infection on L-tyrosine (PO substrate) levels in AG and ovotestis revealed a significant increase in the levels of this compound in both organs over the course of infection. It is concluded that AG PO activity is functionally linked to egg formation in normal snails and that a strong association exists between parasite-mediated decrease in AG PO activity and parasitic castration. However, from the data presented, a direct causal relationship linking infection, decreased PO, and castration has yet to be established.

Animals↗