Biomedical subjects

J Guo

Publications and source records attributed to J Guo.

At least 181 records · Page 10Linked to original sources

PubMed2000

[Primary approach on midgastric-transverse band modifying the distribution of food between proximal and distal stomach].

OBJECTIVE: To explore the physiological function of the midgastric-transverse band (MTB) in the modification of intragastric food distribution in digestive period. METHODS: 18 healthy subjects(HS) and 18 patients with functional dyspepsia(FD) participated in this study. After fasting over 8 hours all subjects took 150 ml of milk (777 J) mixed with 150 g Magnesium Sulfate, and laid supinely on 30 degrees angle with horizontal line, X-ray films were taken at 0, 30, 60, and 90 minutes after the meal, respectively. Analyzed parameters included the width of MTB, the total, proximal and distal gastric area (TGA, PGA and DGA), the ratio of proximal and distal stomach during every 30 minutes period, the correlation between MTB and PGA, MTB and DGA. RESULTS: (1) There was significant difference of MTB and DGA in every period postprandially (P < 0.05 or 0.01), by contrast, there were no significant differences of TGA or PGA between HS and FD except at TGA 90 min (P < 0.05). (2) There were close correlation between MTB and PGA at 0 (P < 0.01), 30 (P < 0.01), 60 min (P < 0.01) after the meal in HS, but only at 0 min (P < 0.01) in FD. Also close correlations between MTB and DGA at 60 (P < 0.01) and 90 min (P < 0.01) in HS, but in FD. (3) the ratios of PGA from 0-30 min and 60-90 min in FD significantly decreased respectively, however the other ratios were shown no significant difference between HS and FD during each period. (4) there were close correlations between PGA and MTB at 0, 30, 60 min after the meal in HS, however except 0 min there were no correlations in FD. By contrast, between DGA and MTB there were close correlations at 60, or 90 min in HS, no correlation in FD at any time point. CONCLUSIONS: MTB may play an important role in modifying intragastric food distribution in HS, while the dysfunction of MTB may result in the distal gastric overloading in FD, the mechanism of MTB needs further studies.

Adolescent↗

PubMed2000

[Detection of proteolytic activity of hepatitis C virus NS3-4A protease using enzymelinked immunosorbent assay].

OBJECTIVE: To establish an ELISA method for detecting proteolytic activity of HCV serine protease for screening inhibitors against HCV. METHODS: HCV recombinant plasmid pMAL-c2/NS3-4A was transformed into the E. coli strain K12 TB1. Maltose-binding-protein (MBP)-NS3/NS3-4A fusion protein expression were induced by adding isopropyl-beta-D-thiogalacto-pyranoside (IPTG) and purified by affinity chromatography. The immunological activities of the fusion protein were analyzed by Western blot. A peptide substrate was used to analyze the biological activity of the fusion protein. The hydrolyzed product was treated with sodium iodacetate and labeled with digoxigenin, then adding immunological anti-digoxigenin-alkaline phosphatase conjugate to detect the protease activity by colorimeteric reaction. RESULTS: The purified MBP-NS3 and MBP-NS3-4A proteases were identified as 112,000 u and 116,000 u protein by Western blot. HCV NS3/NS3-4A protease showed substrate cleavage activities by ELISA. Coefficients of variation (CV) of ELISA in a lot and among the lots were 4.16% and 7.52% respectively, the P/N was 3.63 under the best experimental conditions determined by L9 (3(4)) factorial design. The method confirmed that 8.36 mumol/L 1,4-naphthoquinone had 50% inhibitive activity on HCV serine protease. CONCLUSIONS: We have established a simple and rapid ELISA method with stable repeatability for detecting proteolytic activities of HCV NS3-4A protease, which might be used for screening and studying of specific inhibitors of HCV serine protease NS3-4A.

Enzyme-Linked Immunosorbent Assay↗

PubMed2000

Experimental study of homium: YAG laser transmyocardial revascularization in acute ischemic settings with myocardial contrast echocardiography.

OBJECTIVE: To study the mechanism and effects of blood perfusion to the acute ischemic region of myocardium through Ho-YAG laser channels with myocardial contrast echocardiography. METHODS: To produce the model of acute myocardial ischemia, we partially ligated the left anterior decending (LAD) coronary artery of canine hearts between 1st. and 2nd. diagonal branches and then performed transmyocardial revascularization in this region with Ho - YAG laser. Myocardial contrast echocardiography was made with a new generation of ultrasound contrast agent and second harmonic imaging of this region before, after ischemia and after laser revascularization. Pictures were taken with "R" wave trigger skill. RESULTS: Acoustic density determing in the ischemia region (anterior wall) with MCE (myocardial contrast echocardiography) was obviously decreased (5.40 +/- 1.81) after the LAD was ligated,as compared with before (11.69 +/- 1.61, P < 0.01). It was increased remarkably after transmyocardial laser revascularization (TMLR) (11.2 +/- 2.01, P < 0.01) as compared with that when ischemia and approximated to that before ischemia (P > 0.05). There were no differences in acoustic density in the lateral wall (as control) among these comprehensive three periods (P > 0.05). Contrast in the laser region developed one cardiac cycle ahead of that in the non-ischemic normal region. CONCLUSION: Acute ischemic myocardium can be perfused by oxygenated blood from the left ventricle through Ho - YAG laser channels. Evidence of blood perfusion through laser channels during systolic phase was detected, and myocardial contrast ultrasonography using intravenous perfluorocarbon-exposed sonicated dextrose albumin may be regarded as a reliable method in the study of transmyocardial revascularization.

Animals↗

PubMed1999

Dynamin 2 is required for phagocytosis in macrophages.

Cells internalize soluble ligands through endocytosis and large particles through actin-based phagocytosis. The dynamin family of GTPases mediates the scission of endocytic vesicles from the plasma membrane. We report here that dynamin 2, a ubiquitously expressed dynamin isoform, has a role in phagocytosis in macrophages. Dynamin 2 is enriched on early phagosomes, and expression of a dominant-negative mutant of dynamin 2 significantly inhibits particle internalization at the stage of membrane extension around the particle. This arrest in phagocytosis resembles that seen with inhibitors of phosphoinositide 3-kinase (PI3K), and inhibition of PI3K prevents the recruitment of dynamin to the site of particle binding. Although expression of mutant dynamin in macrophages inhibited particle internalization, it had no effect on the production of inflammatory mediators elicited by particle binding.

Animals↗

PubMed1999

T-cell co-stimulation through B7RP-1 and ICOS.

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.

Amino Acid Sequence↗

PubMed1999

Protection against the mortality associated with disease models mediated by TNF and IFN-gamma in mice lacking IFN regulatory factor-1.

Mortality and cytokine production associated with disease models mediated by TNF- and IFN-gamma were studied in mice lacking IFN regulatory factor-1 (IRF-1). IRF-1 knockout (KO) mice showed no mortality after the injection of a dose of LPS lethal in intact control mice (LD95). KO mice showed lower circulating levels of TNF and IFN-gamma than controls. KO mice also showed lower TNF and IFN-gamma mRNA in the spleen or liver than controls. KO mice had smaller spleens than controls, which contained similar percentage but lower absolute count of macrophages and lower percentage and absolute count of NK cells. IRF-1 KO mice survived longer than controls after the coinjection of LPS and galactosamine. IRF-1 KO mice also showed less mortality than controls after the injection of Con A and in a model of cerebral malaria. After the injection of a lethal dose of TNF (LD88), mortality was similar between KO and intact mice. Mortality was also similar after the coinjection of two nonlethal doses of TNF and IFN-gamma, a lethal combination (LD100). This study shows that the lack of IRF-1 protects against the mortality associated with disease models mediated by TNF and IFN-gamma but has no effect on the mortality directly induced by TNF and IFN-gamma. The lack of IRF-1 appears to result in impaired production of TNF and IFN-gamma, reflecting a down-regulation of gene expression in the liver and spleen as well as a reduction in the number of splenic cells.

Animals↗

PubMed1999

Nicardipine-sensitive Na+-mediated single channel currents in guinea-pig sinoatrial node pacemaker cells.

1. The Na+-dependent inward currents underlying slow diastolic depolarization of sinoatrial (SA) node cells were examined. Using a Na+-rich, Ca2+-free pipette solution a novel single channel current was recorded in addition to the conventional Na+ and L-type Ca2+ currents. The current (termed ist, as it reflects the whole-cell sustained inward current, Ist) does not show obvious inactivation during a 700 ms depolarization and is unique in having a smaller amplitude (1.1 +/- 0.18 pA at -60 mV, n = 12) than the Na+ current through conventional Na+ ( approximately 3.3 pA) and Ca2+ channels (9.6 +/- 0.32 pA at -60 mV, n = 8). The mean unitary conductance of ist channels was 13.3 pS. 2. The recording of ist was infrequent, was observed only in spontaneously beating SA node cells, and was facilitated by adding Bay-K 8644 to the pipette solution. Overlapping of ist events was observed and ist was abolished by bath application of nicardipine. 3. In the ensemble average, the activation of ist was evident by depolarization beyond -70 mV, and the dynamic voltage range of activation (-70 to -30 mV) encompassed the extent of the slow diastolic depolarization. The current density of ist was 0.33 pA pF-1 at -60 mV, as estimated from the number of channels per membrane patch, the open probability and the unitary amplitude. 4. Cumulative histograms for both open and closed times were fitted with a sum of two exponential components. The slow time constants decreased with depolarization, while the fast time constants and the fraction of the fast component were voltage independent. The number of bursts per sweep increased with depolarization. The time constant of the first latency histogram was about two orders of magnitude larger than those in cardiac L-type Ca2+ channels and decreased with depolarization. 5. It is suggested that the ist channels might be responsible for the whole-cell Ist.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1999

Structure and alternative splicing of the gene encoding alpha1G, a human brain T calcium channel alpha1 subunit.

The structure of CACNA1G, the gene encoding alpha1G, a human brain T Ca2+ channel alpha1 subunit, was determined by comparison of polymerase chain reaction-amplified brain cDNA and genomic sequences. The gene consists of at least 38 exons, two of them newly-identified, spanning at least 66490 basepairs of chromosome 17q22. Alternative splicing of the RNA occurs at six sites: cassette exons 14, 26, 34 and 35, an internal donor in exon 25 and protein-coding intron 38B. Additionally, the RNA can be polyadenylated at either of two sites. Alternative splicing of CACNA1G RNA may lead to expression of as many as 24 distinct protein products, ranging from 2171 to 2377 amino-acids residues.

Alternative Splicing↗

PubMed1999

[The complete nucleotide sequences of A/Goose/Guangdong/2/96(H5N1) virus RNA segment 1-3 and 5].

OBJECTIVE: To determine the nucleotide and amino acid sequences of PB2, PB1, PA and NP genes and compared them with sequences of A/HK/156/97(H5N1) virus for revealing the relationship between A/Googs/Guangdong/2/96(H5N1) and A/HK/156/97(H5N1) viruses. METHODS: Virion RNA was transcribed into cDNA by reverse transcriptase, cDNA amplified by PCR, the productions of PCR were purified. Afterward, RNA sequence analysis was performed by the dideoxynucleotide chain termination method, using synthetic oligodeoxynucleotide primers. RESULTS: The lengths of A/Goose/Guangdong/2/96(H5N1) virus RNA segment 1-3 and 5 contain 2,341, 2,341, 2,233 and 1,565 nucleotides, respectively. They encode for PB2 (759 amino acids), PB1 (757 amino acids), PA (716 amino acids) and NP (498 amino acids) proteins. The homologies of amino acid sequences of PB2, PB1, PA and NP proteins between A/Goose/Guangdong/2/96 (H5N1) and A/HK/156/97 (H5N1) virus are 96.4%, 97.2%, 97.3% and 97.0%, respectively. CONCLUSION: The lengths of RNA segment 1-3 and 5 of Goose strain are 2,341, 2,341, 2,233 and 1,565 nucleotides, respectively. The nucleotide sequences of these genes are distinguish able from those of Hong Kong virus.

Amino Acid Sequence↗

PubMed1999

Novel neurotrophin-1/B cell-stimulating factor-3: a cytokine of the IL-6 family.

We have identified a cytokine of the IL-6 family and named it novel neurotrophin-1/B cell-stimulating factor-3 (NNT-1/BSF-3). NNT-1/BSF-3 cDNA was cloned from activated Jurkat human T cell lymphoma cells. Its sequence predicts a 225-aa protein with a 27-aa signal peptide, a molecular mass of 22 kDa in mature form, and the highest homology to cardiotrophin-1 and ciliary neurotrophic factor. The gene for NNT-1/BSF-3 is on chromosome 11q13. A murine equivalent to NNT-1/BSF-3 also was identified, which shows 96% homology to human NNT-1/BSF-3. NNT-1/BSF-3 mRNA is found mainly in lymph nodes and spleen. NNT-1/BSF-3 induces tyrosine phosphorylation of glycoprotein 130 (gp130), leukemia inhibitory factor receptor beta, and signal transducer and activator of transcription 3 in the SK-N-MC human neuroblastoma cells. NNT-1/BSF-3 shows activities typical of IL-6 family members. In vitro, it supports the survival of chicken embryo motor and sympathetic neurons. In mice, it induces serum amyloid A, potentiates the induction by IL-1 of corticosterone and IL-6, and causes body weight loss and B cell hyperplasia with serum IgG and IgM increase. NNT-1/BSF-3 is a gp130 activator with B-cell stimulating capability.

Amino Acid Sequence↗

PubMed1999

Structure and alternative splicing of the gene encoding alpha1I, a human brain T calcium channel alpha1 subunit.

The structure of CACNA1I, the gene encoding alpha1I, a human brain T Ca2+ channel alpha1 subunit, was determined by comparison of polymerase chain reaction-amplified brain cDNA and genomic sequences. The gene consists of at least 36 exons spanning at least 115,168 basepairs of chromosome 22q12.3-13.2. The predicted protein has 2016 amino acids and 28 potential phosphorylation sites. Alternative splicing of the gene occurs at two sites: cassette exon 9 and an alternative acceptor in exon 33. Molecular diversity generated by alternative splicing and post-translational modification of this and other members of the T alpha1 subunit gene family may account for the observed heterogeneity of T currents in central neurons.

Alternative Splicing↗

PubMed1999

On the structure of endogenous ouabain.

The ouabain-like sodium pump inhibitor in mammals (so-called "endogenous ouabain") has been considered a subtle structural isomer of ouabain. Its structural investigation, however, has long been hindered by the paucity of sample material. Our recent purification of endogenous ouabain (3 micrograms) from bovine hypothalamus allowed the measurement of its 1H-NMR. The obtained spectrum as well as reexamination of past microscale structural studies on endogenous ouabain led us to identify the purified material as ouabain in an unusual manner. It turned out that the structural analysis had been complicated by a facile ouabain-borate complexation in borosilicate glassware. In retrospect, it is not surprising that the polyhydroxylated ouabain molecule serves as a polydentate ligand to inorganic species. In its physiological environment, ouabain may exist as some unknown complex. The chemical species giving rise to the reported biological activities of hypothalamic inhibitory factor preparations remain to be clarified.

Animals↗

PubMed1999

[Free-radical theory and the antisenescence effect of fruits and vegetables].

Oxidative damage resulting from free radical is a major cause of ageing and chronic degenerative disease. Epidemiological studies show that frequent consumption of fruit and yellow or green leafy vegetables may prevent many kinds of chronic degenerative diseases associated with the increasing of age. These may be related with the anti-oxidative ingredients in fruit and vegetables. Nevertheless, trials using anti-oxidative nutrient, such as vitamin C, E and beta-carotene supplements, did not get the expected result so far. Thus, it is necessary to strengthen the research on the potential effective anti-oxidative ingredients in fruit and vegetables. On the other hand, the study on the effect of fruit and vegetables on life span and improving life quality are also needed.

Aging↗

PubMed1999

Cyclin T1 domains involved in complex formation with Tat and TAR RNA are critical for tat-activation.

Tat activates transcription from the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) by increasing the processivity of RNA polymerase II. Recently, it has been demonstrated that the cellular kinase CDK9 and its binding partner cyclin T1 are involved in regulating transcriptional elongation and tat-activation. Cyclin T1, CDK9 and Tat bind as a complex to elements in TAR RNA that are required for tat-activation. Here, we used cyclin T1 mutants to define domains in this protein that bind to both CDK9 and Tat and are involved in stimulating tat-activation. The region of cyclin T1 extending from amino acid residues 1 to 263 is necessary for complex formation with Tat bound to TAR RNA and for stimulation of tat-activation in murine cells that are normally poorly responsive to the actions of Tat. In contrast, a smaller region of cyclin T1 was required to bind to CDK9 and stimulate its kinase activity. Recombinant cyclin T1 and CDK9 stimulated both basal and tat-induced in vitro transcriptional elongation from the HIV-1 LTR. The effects of Tat on transcriptional elongation may be mediated by its ability to increase CDK9 phosphorylation of the RNA polymerase II C-terminal domain. These results demonstrate that cyclin T1 interactions with Tat and TAR RNA are critical for activation of HIV-1 gene expression.

Cyclin T↗

PubMed1999

Role of the human and murine cyclin T proteins in regulating HIV-1 tat-activation.

Human cyclin T1 markedly stimulates tat-activation in rodent cells which are normally poorly responsive to the effects of Tat. This result suggests that there are likely to be critical differences in the murine and human cyclin T1 proteins. Here, we analyzed the role of the murine and human cyclin T1 proteins in addition to the human cyclin T2a and T2b proteins on regulating tat-activation. Only the human cyclin T1 protein efficiently formed a complex with Tat bound to TAR RNA. This difference in function was due to the presence of a cysteine residue in human cyclin T1 at position 261 rather than a tyrosine or asparagine residue which are found in the murine cyclin T1 protein and the human cyclin T2a and T2b proteins, respectively. A mouse cyclin T1 protein containing a substitution of tyrosine residue 261 with a cysteine residue, was able to interact with Tat and stimulate tat-transactivation in rodent cells. Likewise, substitution of a cysteine residue for an asparagine residue at position 260 of the cyclin T2a and T2b proteins also resulted in their ability to interact with Tat and stimulate tat-activation in rodent cells. The data indicate that a specific residue in the cyclin T proteins is required for their in vitro interaction with Tat and their ability to stimulate in vivo tat-activation.

Animals↗

PubMed1999

[The antioxidant activity of wild jujubi, crataegus and grape in vitro].

Two oxidative damaging systems, Fe(2+)-Cys and tert-butyl hydroperoxide, were used to induce the production of malondialdehyde (MDA) in rat liver microsome and erythrocytes. The inhibition rate of wild jujubi, crataegus and grape juice at the concentration of 2.5-3.3 mg/ml to Fe(2+)-Cys system on the production of MDA were 46.2%, 98.3% and 99.1% respectively. The inhibition rate of jujubi (8.3 mg/ml), crataegus (13.9 mg/ml) and grape (55.6 mg/ml) to tert-butyl hydroperoxide were 38.7%, 38.7% and 58.5% respectively. The capability of scavenging O2.- and .OH was measured by ESR technique. It was found that the capability of these juices to eliminate O2.- and .OH generated by the xanthine/xanthine oxidase system and H2O2-FeSO4 system was strong. The elimination rate of jujubi (50 mg/ml), crataegus (50 mg/ml) and grape (134 mg/ml) to O2.- were 84.0%, 85.8% and 74.7% respectively and the rate to .OH were 96.7%, 97.8% and 86.3% respectively. The results indicated that these three fruits bear antioxidant activity.

Animals↗

PubMed1999

[Preheating decrease the sensitivity of K562 cell to chemotherapeutic drugs].

Hyperthermia is a powerful tool for enhancing the effect of many chemical drugs on killing cells, but too many times of hyperthermia could decrease the effect and increase the ability of tumor cell against chemical drugs. Heat stress protein 70(HSP70) mRNA of K562 cell was analyzed by RT-PCR, and the chemosensitivity of K562 cell was tested by MTT method before and after heat-exposure. The results showed that HSP70 mRNA increased greatly after K562 cells exposed to 40 degrees C for 30 min and then it went to the top after 120 min heat-exposure. The sensitivity of K562 cell to adriamycin (ADM) and cyclophosphamide (CTX) in a usual dosage (1/250 of one dosage in clinical use) was in middle degree before exposed to heat, and the sensitivity dramatically went down after K562 cell being heat-stressed. The sensitivity of heat-stressed tumor cells to chemotherapeutic drugs was decreased, which may come from the increased expression of stress proteins in cells.

Antineoplastic Agents↗

PubMed1999

Gender related differences in ATP-dependent transport of dinitrophenyl-glutathione conjugate across murine canalicular liver plasma membrane.

The present study reports gender related differences in ATP-dependent transport of dinitrophenyl-glutathione (GSH) conjugate (DNP-SG), a model GSH xenobiotic conjugate, across murine canalicular liver plasma membrane (cLPM). ATP-dependent transport of DNP-SG across female A/J mouse cLPM was mediated by two components, a high-affinity and a low-affinity component, with corresponding Km of 18 microM (Vmax 0.02 nmol/min.mg) and 500 microM (Vmax 0.23 nmol/min.mg), respectively. On the other hand, only one component for the ATP-dependent transport of DNP-SG was observed in male mouse cLPM (K(m) 130 microM; Vmax 0.18 nmol/min.mg). Moreover, the rate of ATP-dependent transport of DNP-SG was markedly higher in the cLPM fraction of male mouse compared with that of the female. Presence of two transport components in female mouse cLPM, but only one system in the cLPM fraction of male mouse, was confirmed by measuring DNP-SG mediated stimulation of ATP hydrolysis (DNP-SG ATPase activity). To the best of our knowledge, the present study is the first report on gender related differences in ATP-dependent murine canalicular transport of GSH conjugates.

Adenosine Triphosphate↗