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Biomedical subjects

J Gao

Publications and source records attributed to J Gao.

At least 145 records · Page 8Linked to original sources
PubMed2000

A combined QM/MM study of the nucleophilic addition reaction of methanethiolate and N-methylacetamide.

A combined quantum mechanical (QM) and molecular mechanical (MM) method was used to study the nucleophilic addition reaction of methanethiolate to N-methylacetamide (NMA) in the gas phase and aqueous solution. At the B3LYP/aug-cc-pVDZ//HF/6-31 + G(d) level, the ion-dipole complex was found to be the global minimum on the potential energy surface in the gas phase with a binding energy of 21.2 kcal/mol. The complex has a C-S distance of 4.33 A, and no stabilized tetrahedral intermediate was located. The computed potential of mean force in water shows that solvent effects stabilize the reactants over the tetrahedral adduct by 36.5 kcal/mol, and that the tetrahedral intermediate does not exist for the present reaction in water. The present study provides an initial step for modeling the cysteine protease hydrolysis reactions in enzymes.

Acetamides↗
PubMed2000

Uptake and phytotransformation of organophosphorus pesticides by axenically cultivated aquatic plants.

The uptake and phytotransformation of organophosphorus (OP) pesticides (malathion, demeton-S-methyl, and crufomate) was investigated in vitro using the axenically aquatic cultivated plants parrot feather (Myriophyllum aquaticum), duckweed (Spirodela oligorrhiza L.), and elodea (Elodea canadensis). The decay profile of these OP pesticides from the aqueous medium adhered to first-order kinetics. However, extent of decay and rate constants depended on both the physicochemical properties of the OP compounds and the nature of the plant species. Malathion and demeton-S-methyl exhibited similar transformation patterns in all three plants: 29-48 and 83-95% phytotransformation, respectively, when calculated by mass recovery balance during an 8-day incubation. No significant disappearance and phytotransformation of crufomate occurred in elodea over 14 days, whereas 17-24% degraded in the other plants over the same incubation period. Using enzyme extracts derived from duckweed, 15-25% of the three pesticides were transformed within 24 h of incubation, which provided evidence for the degradation of the OP compounds by an organophosphorus hydrolase (EC 3.1.8.1) or multiple enzyme systems. The results of this study showed that selected aquatic plants have the potential to accumulate and to metabolize OP compounds; it also provided knowledge for potential use in phytoremediation processes.

Biotransformation↗
PubMed2000

Uptake and phytotransformation of o,p'-DDT and p,p'-DDT by axenically cultivated aquatic plants.

The uptake and phytotransformation of o,p'-DDT and p,p'-DDT were investigated in vitro using three axenically cultivated aquatic plants: parrot feather (Myriophyllum aquaticum), duckweed (Spirodela oligorrhiza), and elodea (Elodea canadensis). The decay profile of DDT from the aqueous culture medium followed first-order kinetics for all three plants. During the 6-day incubation period, almost all of the DDT was removed from the medium, and most of it accumulated in or was transformed by these plants. Duckweed demonstrated the greatest potential to transform both DDT isomers; 50-66% was degraded or bound in a nonextractable manner with the plant material after the 6-day incubation. Therefore, duckweed also incorporated less extractable DDT (32-49%) after 6 days than did the other plants. The capacity for phytotransformation/binding by elodea is between that of duckweed and parrot feather; approximately 31-48% of the spiked DDT was degraded or bound to the elodea plant material. o,p'-DDD and p,p'-DDD are the major metabolites in these plants; small amounts of p,p'-DDE were also found in duckweed (7.9%) and elodea (4.6%) after 6 days. Apparently, reduction of the aliphatic chlorine atoms of DDT is the major pathway for this transformation. This study, which provides new information on plant biochemistry as related to pollutant accumulation and phytotransformation, should advance the development of phytoremediation processes.

Biotransformation↗
PubMed2000

Involvement of capsaicin-sensitive sensory neurons in stress-induced gastroduodenal mucosal injury in rats.

The pathogenesis of stress-induced gastroduodenal mucosal injury is complex and incompletely understood. The aim of this investigation was to examine the involvement of gastric and duodenal capsaicin-sensitive neurons in mucosal damage associated with water-restraint stress (WRS) in rats. Following WRS, gastroduodenal mucosal injury was quantitated by macroscopic and microscopic methods. Calcitonin gene-related peptide (CGRP) content was measured by radioimmunoassay. WRS-induced mucosal erosive injury in the stomach and duodenum (40.9 +/- 4.2 and 5.1 +/- 0.6 mm2, respectively) was reduced significantly (by 88% and 67%, respectively) by acute intragastric capsaicin administration prior to WRS. In contrast, sensory denervation by chronic capsaicin significantly increased the area of gastric injury and duodenal damage. WRS alone caused a significant reduction (by 52% and -35%, respectively) in gastric and duodenal CGRP content, which was prevented by acute capsaicin treatment. The data suggest that gastric and duodenal sensory neurons and CGRP are involved in the pathogenesis of stress-induced mucosal injury to the stomach and duodenum.

Animals↗
PubMed2000

Cloning, tissue expression pattern and genomic organization of latexin, a human homologue of rat carboxypeptidase A inhibitor.

Latexin, a carboxypeptidase A inhibitor, is expressed in a cell type-specific manner in both central and peripheral nervous systems in the rat. It is used as a molecular marker for the regional specification of the neocortex. In this study, a cDNA was isolated from a human fetal brain cDNA library. The cDNA (LXN) contains an open reading frame encoding 222 amino acids. The comparison between the deduced amino acid sequences of LXN and latexins of rat and mouse revealed high sequence identity (84.2 and 84.7%, respectively). Northern blot analysis showed that LXN was expressed as a transcript of 1.3 kb in 15 out of 16 tissues examined, except in peripheral blood leukocyte. The expression levels were high in heart, prostate, ovary, kidney, pancreas, and colon, moderate or low in other tissues including brain. It is noteworthy that the tissue distribution of human LXN differs greatly to that of its homologue in the model animal, rat latexin. In addition, the LXN gene contains at least 6 exons and spans 5.9 kb according to the genomic sequence of the clone RP11-79M21 and the gap sequence cloned in this paper. LXN was assigned to 3q25-q26.2 according to the position of the marker SHGC-35682 found adjacent to LXN gene.

Amino Acid Sequence↗
PubMed2000

Identification of androgen, estrogen and progesterone receptor mRNAs in the eye.

PURPOSE: Previous research has demonstrated that sex steroids exert a significant influence on the structure and function of numerous ocular tissues. To begin to explore the underlying basis of this hormone action, we examined whether various anterior and posterior tissues of the eye contain androgen, estrogen and progesterone receptor mRNAs. METHODS: Tissue samples were obtained from adult male and female rats, rabbits and humans, processed for the isolation of total RNA and analyzed by RT-PCR, agarose gel electrophoresis and Southern blot hybridization. All PCR amplifications included positive and negative controls. RESULTS: Our findings showed that androgen, estrogen and/or progesterone receptor mRNAs are present in the lacrimal gland, lacrimal gland acinar epithelial cells, meibomian gland, lid, palpebral and bulbar conjunctivae, cornea, iris/ciliary body, lens, retina/uvea, retina/choroid and retinal pigment epithelial cells of rats, rabbits or humans. CONCLUSIONS: Our findings demonstrate that sex steroid receptor mRNAs exist in a variety of ocular tissues and suggest that these sites may represent target organs for androgens, estrogens and/or progestins.

Animals↗
PubMed2000

Sustained delivery and expression of DNA encapsulated in polymeric nanoparticles.

Sustained release polymeric gene delivery systems offer increased resistance to nuclease degradation, increased amounts of plasmid DNA (pDNA) uptake, and the possibility of control in dosing and sustained duration of pDNA administration. Furthermore, such a system lacks the inherent problems associated with viral vectors. Biodegradable and biocompatible poly(DL-lactide-co-glycolide) polymer was used to enacapsulate pDNA (alkaline phosphatase, AP, a reporter gene) in submicron size particles. Gene expression mediated by the nanoparticles (NP) was evaluated in vitro and in vivo in comparison to cationic-liposome delivery. Nano size range (600 nm) pDNA-loaded in poly(DL-lactide-co-glycolide) polymer particles with high encapsulation efficiency (70%) were formulated, exhibiting sustained release of pDNA of over a month. The entrapped plasmid maintained its structural and functional integrity. In vitro transfection by pDNA-NP resulted in significantly higher expression levels in comparison to naked pDNA. Furthermore, AP levels increased when the transfection time was extended, indicating sustained activity of pDNA. However, gene expression was significantly lower in comparison with standard liposomal transfection. Seven days after i.m. injections in rats, naked pDNA and pDNA-NP were found to be significantly more potent (1-2 orders of magnitude) than liposomal pDNA. Plasmid DNA-NP treatment exhibited increased AP expression after 7 and 28 days indicating sustained activity of the NP.

3T3 Cells↗
PubMed2000

Microcirculation impedance analysis in cat lung.

An analysis of pulsatile microcirculation in cat lung, with special attention to the pulmonary microvascular impedance, is presented. A theoretical calculation is made on the basis of a complete set of experimental data on the morphology and elasticity of cat's pulmonary capillary sheets. The transfer matrix of the pulmonary microvascular impedance is obtained. The input impedance at the capillary entrance and exit are determined. The input impedance at the pulmonary arterial trunk is compared under various physiological conditions. It is shown that although the impact of pulmonary microcirculation on the relationship between the steady mean flow and pressure in the pulmonary arteries and veins is decisively large, the influence of the alveolar microcirculation on the input impedance at the pulmonary arterial trunk is small.

Animals↗
PubMed2000

PKCepsilon modulates NF-kappaB and AP-1 via mitogen-activated protein kinases in adult rabbit cardiomyocytes.

We have previously shown that protein kinase C (PKC)-epsilon, nuclear factor (NF)-kappaB, and mitogen-activated protein kinases (MAPKs) are essential signaling elements in ischemic preconditioning. In the present study, we examined whether activation of PKCepsilon affects the activation of NF-kappaB in cardiac myocytes and whether MAPKs are mediators of this signaling event. Activation of PKCepsilon (+108% above control) in adult rabbit cardiomyocytes to a degree that has been previously shown to protect myocytes against hypoxic injury increased the DNA-binding activity of NF-kappaB (+164%) and activator protein (AP)-1 (+127%) but not that of Elk-1. Activation of PKCeta did not have an effect on these transcription factors. Activation of PKCepsilon also enhanced the phosphorylation activities of the p44/p42 MAPKs and the p54/p46 c-Jun NH(2)-terminal kinases (JNKs). PKCepsilon-induced activation of NF-kappaB and AP-1 was completely abolished by inhibition of the p44/p42 MAPK pathway with PD98059 and by inhibition of the p54/p46 JNK pathway with a dominant negative mutant of MAPK kinase-4, indicating that both signaling pathways are necessary. Taken together, these data identify NF-kappaB and AP-1 as downstream targets of PKCepsilon, thereby establishing a molecular link between activation of PKCepsilon and activation of NF-kappaB and AP-1 in cardiomyocytes. The results further demonstrate that both the p44/p42 MAPK and the p54/p46 JNK signaling pathways are essential mediators of this event.

Animals↗
PubMed2000

Ligand-activated progesterone receptor isoform hPR-A is a stronger transactivator than hPR-B for the expression of IGFBP-1 (insulin-like growth factor binding protein-1) in human endometrial stromal cells.

In human endometrium, the levels of progesterone receptor (PR) isoforms hPR-A and hPR-B are differentially regulated during the reproductive cycle. Progesterone significantly increases the content of hPR-A, the predominant isoform in decidualized stromal cells (1). The purpose of this study was to determine the capacity of hPR-A and hPR-B to transactivate the progestin-dependent target gene in human endometrial stromal cells. We examined the effect of cotransfection of hPR-A or hPR-B on the expression of the human insulin-like growth factor binding protein-1 (IGFBP-1) in endometrial stromal cells. The primary culture of human endometrial stromal cells was transfected with the hPR-A or hPR-B expression vector and the IGFBP-1 promoter construct p275CAT, which contains two functional progesterone response elements (PRE1 and PRE2) in decidualized stromal cells. Medroxyprogesterone acetate (MPA) increased the promoter activities ranging from 1.2- to 27-fold in cells cotransfected with hPR-A or hPR-B in eight endometrial specimens. The promoter activity increased by the hPR-A was significantly higher than hPR-B (15 +/- 8 vs. 4 +/- 2, mean +/- SD; n = 8, P < 0.005). Site-specific mutation showed that the induced activity by hPR-A was mediated through the PRE1 and PRE2 sites. Addition of hPR-B reduced the effect of hPR-A. The high transactivation capacity of hPR-A was also activated by other ligands, progesterone, Org 2058, and norethindrone. These observations indicate that hPR-A is a stronger transactivator than hPR-B for the IGFBP-1 promoter in endometrial stromal cells. Previous studies have shown the progestin-dependent production of IGFBP-1 correlates with its mRNA levels and transcription rate. Thus, we have determined the effect of hPR-A and hPR-B on the production of IGFBP-1 in stromal cells treated with MPA. The production rate in cells uniformly infected with AdPRA (recombinant Ad5-directed PR expression system) was significantly higher (P < 0.001) than the rate in uninfected cells and in cells infected with AdPRB or AdCMV (the Ad5 viral expression vector). This result, in concert with the promoter analysis, provides evidence that hPR-A is a strong inducer for the chromosomal IGFBP-1 gene in endometrial stromal cells.

Adult↗
PubMed2000

Three new phenylethanoid glycosides from Caryopteris incana and their antioxidative activity.

Three new phenylethanoid glycosides, incanoside C, incanoside D and incanoside E were isolated together with one known glycoside, beta-D-fructofuranosyl-alpha-D-(6-O-[E]-sinapoyl) glucopyranoside from the whole plant of Caryopteris incana (THUNB.) Miq. On the basis of chemical and spectral analyses, the structures of the new compounds were elucidated to be 1-O-(3,4-dihydroxyphenyl)ethyl-O-beta-D-glucopyranosyl(1-->2)-alpha-L- rhamnopyranosyl(1-->3)-4-O-feruloyl-beta-D-glucopyranoside (incanoside C), 1-O-(3-hydroxy-4-methoxyphenyl)ethyl-O-beta-D-glucopyranosyl(1-->2)-alph a-L- rhamnopyranosyl(1-->3)-4-O-feruloyl-beta-D-glucopyranoside (incanoside D) and 1-O-(3methoxy-4-hydroxyphenyl)ethyl-O-beta-D-glucopyranosyl(1-->2) -alpha-L- rhamnopyranosyl(l-->3)-4-O-feruloyl-beta-D-glucopyranoside (incanoside E). The three new phenylethanoid glycosides exhibited radical scavenging activities against DPPH radical and inhibitory activities against the oxidation of linoleic acid.

Antioxidants↗
PubMed2000

Human parainfluenza virus type 3 upregulates ICAM-1 (CD54) expression in a cytokine-independent manner.

Human parainfluenza virus type 3 (HPIV3) causes bronchiolitis, pneumonia, and croup in newborns and infants. Several studies have implicated intercellular adhesion molecule-1 (ICAM-1) in inflammation during infection by viruses. In this study, we investigated the potential for HPIV3 to induce ICAM-1 in HT1080 cells. FACS analysis showed that HPIV3 strongly induced ICAM-1 expression in these cells. The ICAM-1 induction was significantly reduced when the virions were UV inactivated prior to infection, indicating that ICAM-1 induction was mostly viral replication dependent. Culture supernatant of HPIV3-infected cells induced ICAM-1 at an extremely low level, indicating that virus-induced cytokines played only a minor role in the induction process. Consistent with this, potent inducers of ICAM-1 such as IFN-gamma, TGF-beta, and TNF-alpha were absent in the culture supernatant, but a significant amount of IFN type 1 was present. By using U2A cells, which are defective in IFN type I signaling, we confirmed that ICAM-1 induction by HPIV3 occurred in a JAK/STAT signaling-independent manner. These data strongly indicate that HPIV3 induces ICAM-1 directly by viral antigens in a cytokine-independent manner; this induction may play a role in the inflammation during HPIV3 infection.

Animals↗
PubMed2000

Increased detectability of alpha brain glutamate/glutamine in neonatal hypoxic-ischemic encephalopathy.

BACKGROUND AND PURPOSE: Proton MR spectroscopy (MRS) detectability of brain glutamate/glutamine (Glx) is increased in hypoxic-ischemic insults and is implicated in the neuronal injury and death that follows. Our aim was to correlate the proton MRS detectability of alpha-CH protons of Glx (alpha-Glx) with the Sarnat stage of neonatal hypoxic-ischemic encephalopathy (HIE). METHODS: Initial and follow-up proton MRS studies at 1.9 T were performed in 28 neonates aged 1 to 7 days (seven healthy control subjects and 21 with HIE: 10 mild, nine moderate, and two severe) and in 12 neonates aged 13 to 17 days (12 with HIE: eight mild, three moderate, and one severe), respectively. Both point-resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) sequences were used. The spectral volume of interest was in the basal ganglia, thalami, and adjoining regions. The detectability of alpha-Glx was assessed by two different parameters: the detection rate of the alpha-Glx peak and the peak-area ratio of alpha-Glx to creatine and phosphocreatine. RESULTS: On both the initial and follow-up PRESS studies, all the neonates with moderate and severe HIE showed an alpha-Glx peak, compared with one healthy control subject in the initial study and one neonate with mild HIE in both the studies. They also demonstrated a significantly higher peak-area ratio of alpha-Glx/(creatine and phosphocreatine) on both the initial and follow-up studies. The peak-area ratios in neonates with HIE positively correlated with the Sarnat stage of HIE on both the initial and follow-up studies. Neonates with moderate and severe HIE also showed a consistently higher alpha-Glx peak on both the initial and follow-up studies with the STEAM sequence. CONCLUSION: Proton MRS detectability of alpha-Glx is increased in moderate and severe HIE and correlates with the Sarnat stage of HIE.

Brain↗
PubMed2000

Health insurance and hospitalisation in urban China: bending to the wind of change.

The transformation from a planned economy to a market-oriented one in China has had profound impact on access to health care for a vast majority of the Chinese population. This article used the data from the national household health surveys conducted in 1993 and 1998 to show that the coverage of health insurance declined significantly from 54% to 39% among the urban population over the period, while rate of hospital admission came down from 45 inpatients per 1,000 people in 1992 to 30 inpatients per 1,000 people in 1997. It concludes that the declined coverage of health insurance and the rapid rise of medical care costs were the major factors affecting the access of the Chinese population to hospital care services.

China↗
PubMed2000

[Effect of flooding stress on transpiration of poplar I-69/55].

The rates of transpiration(Tr) and photosynthesis(Pn) of poplar I-69/55 trees were measured under flooding stress. Flooding stress caused Pn and Tr decreasing, while in the period of measurement, Pn almost didn't change. The longer the period of flooding stress was, the more the Tr and stomatal conductance (Gs) decreased. Undre no stress, Pn and Tr of test trees displayed daily double-peak curves and seasonal variations, with the maximum in summer. Water use efficiency also displayed seasonal variation, with the maximum in autumn. Under no stress, Tr obviously changed with tree ages, with the order of 1 year-old > 3 year-old > 7 year-old. The rate of Tr/Pn in spring, summer and autumn was higher than that of other deciduous broad-leaved trees in the same region, especially in summer. The high Tr/Pn ratio means a high water consumption, which is beneficial to water loss of poplar I-69/55. In shoal sites, the temperature of leaf surface in summer and autumn is the most important factor that affects the transpiration rate of poplar I-69/55, suggesting that decreasing the temperature of leaf suface is beneficial to increase the transpiration rate. During the two days after flooding, the temperature of leaf surface is still the important factor that affects transpiration rate.

Disasters↗
PubMed2000

[Therapeutic effect of 5-fluorocytosine on cytosine deaminase gene transduced Wilms' tumor xenograft in nude mice].

OBJECTIVE: To study the effect of 5-fluorocytosine (5-FC) as prodrug in the treatment of Wilms' tumor xenografts transduced with cytosine deaminase (CD) gene. METHODS: An in vivo model of a poorly differentiated Wilms' tumor transplanted in nude mice was established. Expression adenoviral-vector of CD gene (Ad/CMV-CD) or lac gene (Ad/CMV-lac) was transduced to the tumor xenografts by intratumoral injections. Expression of the transduced genes were confirmed by RT-PCR. Mice with Wilms' tumor xenograft were treated with 5-FC (500 mg.kg-1.d-1 x 10 d). Tumor growth was monitored. RESULTS: The growth of tumor xenografts transduced with lac gene grew as quick as the untransduced ones. In contrast, the growth of the tumor xenografts transduced with CD gene was significantly inhibited as compared to untransduced and lac gene transduced xenografts. The average rate of inhibition was 65% according to the tumor weight at 8 wk. Cell necrosis was observed in the CD gene transduced tumors. CONCLUSION: Intratumoral cytosine deaminase gene transduction followed by systemic 5-fluorocytosine is effective in the treatment of Wilms' tumor.

Animals↗
PubMed2000

[Low-molecular-weight heparin for preventing deep-vein thrombosis after total joint arthroplasty].

OBJECTIVE: To evaluate the efficacy and safety of low-molecular-weight heparin (LMWH) in preventing deep-vein thrombosis (DVT) after total hip and knee replacement (THR, TKR). METHODS: From November 1997 to March 1999, we performed total joint replacement for 47 control patients (34 knees, 28 hips) and for 31 patients (19 knees, 17 hips) who had been given low-molecular-weight heparin for preventing deep-vein thrombosis. All patients received venography of the operated limbs after operation. RESULTS: DVT occurred in 19.4% of the LMWH patients (26.3% in TKR, 11.8% in THR) and the reduction was significant (P < 0.05) compared to the control group (48.4%, 55.9%, 39.3% respectively). The incidence of proximal DVT was also reduced significantly (P < 0.05) from 19.4% of the control group to 2.8% of the LMWH group. CONCLUSION: Low-molecular-weight heparin can significantly reduce the incidence of deep-vein thrombosis after total joint replacement.

Arthroplasty, Replacement, Hip↗