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Biomedical subjects

T Gu

Publications and source records attributed to T Gu.

At least 19 recordsLinked to original sources
PubMed2001

Synthesis and electronic properties of covalent assemblies of oligophenylenevinylene units arising from a calix.

Assemblies of four oligophenylenevinylene moieties arising from a calix[4]arene core, i.e., calix[4]oligophenylenevinylenes, have been prepared by Heck-type cross-coupling reactions of styrene derivatives with a tetraiodinated cone-calix[4]arene precursor. Photophysical studies in solution have revealed that there are electronic ground state interactions between the covalently bonded OPV moieties. The absorption spectra of the calix[4]oligophenylenevinylenes are significantly different from those obtained by summing the spectra of four model units and their emission is red-shifted when compared to the corresponding model compounds. Electrochemical studies have shown that the redox processes of the four OPV subunits do not take place at the same potentials indicating also a strong electronic interaction among them in the calix[4]oligophenylenevinylenes.

Journal Article↗
PubMed2001

Antihypertension and anti-cardiovascular remodeling by phenylalanine in spontaneously hypertensive rats: effectiveness and mechanisms.

OBJECTIVE: To investigate mechanisms of anti-hypertension and anti-cardiovascular remodeling by phenylalanine (phe) in spontaneously hypertensive rats (SHRs). METHODS: The comparison of blood pressure (BP) increment with the ages and cardiovascular changes of SHRs was made between the 3% phe-intervented group (SHR-phe) and the control SHRs group. Detection of the structural changes with the VIDAS digital vedio-frequency processing technique and light and electron microscopy were made. The cell growth and proliferation of cultured smooth muscle cells (CSMCs) of the thoracic aortas or myocardial fibroblasts were evaluated by measuring the 3H-thymidine counts per minute (cpm) incorporated into the new synthesized desoxyribonucleic acid (DNA) and determining the cell number with the crystal violet stain technique. The Ca2+ influx was measured in counts/min of 45CaCl2 after incubating it with 5 different concentrations of phenylalanine and the intracellular [Ca2+]i by Fura-II/Am indicator. The total messenger ribonucleic acid (mRNA) of the myocardium was extracted and Northern blot analysis was performed with the probe collagen alpha 2 (I) cDNA. The tyrosine hydroxylase (TH) activity was measured by high-performance liquid chromatography (HPLC) with electrochemical detector after having reacted with its substrate tyrosine and other reagents. The catecholamine contents in brain homogenat were detected by HPLC method. The comparison of pharmacokinetics of phenylalanine among SHR-phe, SHRs and control Wistar Kyoto (WKY) rats was made after intravenous injection of 3H-L-phe (1 ml/kg) by PK-GRAPH Program for kinetic calculation. The 3H-L-phe uptake by CSMCs after incubating for definite intervals was also detected and compared. RESULTS: Phenylalanine could prevent the increase of BP with ages and the heart weight (heart/body weight index). The aortic media thickness and the collagen content in the myocardium were decreased significantly in SHR-phe. Whereas the dearranged cardiovascular structure was much improved. The mechanisms might be direct and specific inhibition of the DNA synthesis and proliferation of cardiovascular cells which may be related to the inhibition of collagen alpha 2(I) cDNA, c-fos and c-myc expression. Other mechanisms may include decrease of intracellular [Ca2+]i and an inhibition of central sympathetic activity due to the results of higher TH activity in the caudate nucleus and higher adrenaline content in the posterior hypothalamus. Besides, partial recovery of phenylalanine metabolic aberrants existed in SHRs seems to be another possibility for its effectiveness. CONCLUSIONS: Phenylalanine intervention could exert a definite anti-hypertension and anti-cardiovascular remodeling effects on SHRs like seen in human essential hypertension. Its mechanisms might be related to direct inhibition of growth in the cardiovascular cells, decrease of central sympathetic activity, the reverse of the exhibited phenylalanine metabolic aberrants in SHRs, and a decrement of intracellular [Ca2+]i.

Animals↗
PubMed2001

Inherited disturbances of phenylalanine metabolic kinetics in essential hypertension.

OBJECTIVE: To clarify whether the disturbances in metabolic kinetics of the essential aminoacid, phenylalanine (phe), are implicated in the genetic pathogenesis of essential hypertension (EH). METHODS: 1. L-(2, 3D3)-leucine, L-(2, 3D3)-isoleucine, L-15N-lysine, L-(2, 3D3)-valine and L-(2, 3D3)-phe were used for simultaneously studying comparative metabolic kinetics using stable isotope tracer methods with a GC-MS system. Study groups were the offspring with both parents suffering EH (n = 10, FH+), 2 or more than 2 parents and grand-parents with EH and stroke (n = 12, FS+) and those without genetic predisposition of EH and stroke (n = 12, F) groups. 2. By comparing the radioactive counts of [3H]-phe, and their weight transformation in blood after 1.5 Ci/kg i.v. administration at defined intervals and in tissues obtained after being sacrified among spontaneously hypertensive rats (SHR), 2 kidney-1 clip hypertensive rats (2K1C) and their normotensive controls (WKY). 3. The time transport and concentration transport of [3H]-L-phe in cpm between the cultured vascular smooth muscle cell of 5th generation in SHR and WKY were compared. RESULTS: A single and unique disturbance of metabolic kinetics in phe were found in FH+, FS+ and SHR. The plasma pool or apparent volume of distribution was enlarged, and the turnover rate constants between plasma and cell tended to show a decrease. The pharmacokinetics of phe in 2K1C was not changed. Only phe content in heart and aorta, the vital organs for predicting BP, were higher in SHR than in WKY tissues studied. Both the time and concentration transport were higher in SHR, e.g., an increment in the net-uptake of L-phe by vascular tissue. CONCLUSION: A unique aberrant of metabolic kinetics of phe might be implicated in the inherited pathogenesis of EH and stroke both from clinical and animal studies.

Adult↗
PubMed2000

[Electric maze test in rats after prenatal methylmercury exposure].

To study the changes of rat's learning and memory ability in maze test after prenatal methylmercury exposure, methylmercury in doses of 0, 0.01, 0.05 and 2.00 mg/(kg.d) were fed to pregnant rats at the 6th-9th day after conception. We adopted a Y-shaped electric maze to detect learning and memory ability of the rat offspring. Double blind was used in the experiment. The results showed that the error times and arrival time of all exposure groups were more, and active avoidance ratio of all exposure groups was less than that of control group. The differences were significant(P < 0.05 or P < 0.01). There was no difference between male and female rats. It is concluded that methylmercury could affect the growth and development of central nerve system. The learning and memory ability of rat offspring was greatly damaged.

Animals↗
PubMed1999

[Cardiac metal foreign body: analysis of 21 cases].

OBJECTIVE: To improve early diagnosis and clinical treatment of metal foreign body in the heart. METHODS: In 21 patients, case history, clinical manifestation, chest X-ray film, and echocardiograph were reviewed. 20 patients received operation: emergency exploration (13) and elective operation (7). Four patients were subjected to cardiopulmonary bypass. The other one was not operated on because of absence of symptoms and small foreign body. Foreign bodies mostly bullets, were usually located in the right ventricle. Ventricular fibrillation occurred in 3 patients during operation, two of them were resuscitated. RESULTS: 20 patients but one recovered, a mortality rate of 5%. CONCLUSIONS: Early diagnosis, rapid management, and localization of foreign body are essential to the selection of treatment.

Adolescent↗
PubMed1998

Modified van der Waals Equation for the Prediction of Multicomponent Isotherms.

A modified two-dimensional van der Waals equation model was proposed for the prediction of multicomponent gas-solid adsorption isotherms from corresponding single-component adsorption equilibrium data. The model was used to predict adsorption isotherms of CO-CO2 mixtures and CO2-N2 mixtures on Cu(I)-NaY zeolite. Experimental adsorption equilibrium data of the two systems were compared with results calculated from the model and three other models in the literature: the ideal adsorbed solution model, the vacancy solution theory of adsorption using the Flory-Huggins activity coefficient equation, and the two-dimensional van der Waals equation. The results indicated that the modified van der Waals equation predicted the experimental results better than the three other models for the two systems studied, especially for the CO-CO2 system, which involved chemical reaction during adsorption and exhibited azeotropic behavior. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Binding of an arm repeat protein to the kinase domain of the S-locus receptor kinase.

Screening of a yeast two-hybrid library for proteins that interact with the kinase domain of an S-locus receptor kinase (SRK) resulted in the isolation of a plant protein called ARC1 (Arm Repeat Containing). This interaction was mediated by the C-terminal region of ARC1 in which five arm repeat units were identified. Using the yeast two-hybrid system and in vitro binding assays, ARC1 was found to interact specifically with the kinase domains from SRK-910 and SRK-A14 but failed to interact with kinase domains from two different Arabidopsis receptor-like kinases. In addition, treatment with a protein phosphatase or the use of a kinase-inactive mutant reduced or abolished the binding of ARC1 to the SRK-910 kinase domain, indicating that the interaction was phosphorylation dependent. Lastly, RNA blot analysis revealed that the expression of ARC1 is restricted to the stigma, the site of the self-incompatibility response.

Amino Acid Sequence↗
PubMed1998

A new marker for mosaic analysis in Caenorhabditis elegans indicates a fusion between hyp6 and hyp7, two major components of the hypodermis.

A fusion of the sur-5 protein to the green fluorescent protein containing a nuclear localization signal is demonstrated as a marker for genetic mosaic analysis in the nematode Caenorhabditis elegans. Because of an extensive accumulation of bright fluorescence in many nuclei, normal growth plates, each containing hundreds of worms, can be rapidly screened with a dissecting microscope for rare mosaic individuals. As the marker can also be used to detect transgenic worms, the construction of strains for mosaic analyses can be minimized. In the course of examining rare mosaic animals, an unexpected pattern of fluorescence was noticed for hyp6, a syncytial component of the hypodermis, which indicated that the marker may serve as a means of assessing cellular fusions during development. Immunofluorescent staining of adherens junctions confirmed a postembryonic fusion of hyp6 with hyp7, the major syncytium of the hypodermis.

Animals↗
PubMed1998

Caenorhabditis elegans SUR-5, a novel but conserved protein, negatively regulates LET-60 Ras activity during vulval induction.

The let-60 ras gene acts in a signal transduction pathway to control vulval differentiation in Caenorhabditis elegans. By screening suppressors of a dominant negative let-60 ras allele, we isolated three loss-of-function mutations in the sur-5 gene which appear to act as negative regulators of let-60 ras during vulval induction. sur-5 mutations do not cause an obvious mutant phenotype of their own, and they appear to specifically suppress only one of the two groups of let-60 ras dominant negative mutations, suggesting that the gene may be involved in a specific aspect of Ras activation. Consistent with its negative function, overexpressing sur-5 from an extragenic array partially suppresses the Multivulva phenotype of an activated let-60 ras mutation and causes synergistic phenotypes with a lin-45 raf mutation. We have cloned sur-5 and shown that it encodes a novel protein. We have also identified a potential mammalian SUR-5 homolog that is about 35% identical to the worm protein. SUR-5 also has some sequence similarity to acetyl coenzyme A synthetases and is predicted to contain ATP/GTP and AMP binding sites. Our results suggest that sur-5 gene function may be conserved through evolution.

Amino Acid Sequence↗
PubMed1997

[The effect of different way of using FGF on wound healing].

To investigate the best way of using fibroblast growth factor (FGF) in wound healing, the following experiments were performed. Twelve Wistar rats were chosen. Four 1.5 cm x 1.5 cm middle-thick skin wounds were made in the back of each rat, 2 in each side, and labelled as number 1 to 4. Number 1 wound of each rat was used as control, only PBS was applied to the wound, 50 microliters per time, twice a day from the first day to 11th day. Number 2 wound was sustained medication group, 50 microliters 4 micrograms/ml FGF was applied twice a day from the first day to 11th day; Number 3 wound was early medication group, 50 microliters 8 micrograms/ml FGF was applied twice a day from the first day to 5th day; Number 4 wound was late medication group, 50 microliters 8 micrograms/ml FGF was added twice a day from the 5th day to 11th day. By day 4, 8, 12 and 16, the area of wounds were measured, and the healing time of each wound was recorded. The elastic fiber, collagen fiber and DNA content were measured by immunohistological method. The result showed that the elastic fiber, collagen fiber and DNA content in the groups of FGF used were more than those in the control group. The healing time of the control group was 14.4 days while that of the early meduation group was 13.4 days, late medation group was 13.5 days and sustained medication group was 12.2 days. It was suggested that FGF could accelerate the wound healing, and sustained use of FGF was the best way of giving the drug.

Animals↗
PubMed1996

Two members of the thioredoxin-h family interact with the kinase domain of a Brassica S locus receptor kinase.

To determine potential targets of the S locus receptor kinase (SRK) during the Brassica self-incompatibility response, a yeast two-hybrid library was screened with the SRK-910 protein kinase domain. Two thioredoxin-h-like clones, THL-1 and THL-2, were found to interact specifically with the SRK-910 protein kinase domain and not to interact with the protein kinase domains from the Arabidopsis receptor-like protein kinases (RLK) RLK4 and RLK5. The interaction between THL-1 and the SRK-910 protein kinase domain was confirmed using coimmunoprecipitation experiments with fusion proteins produced in Escherichia coli. THL-1 has thioredoxin activity based on an insulin reduction assay, and THL-1 is weakly phosphorylated by the SRK-910 protein kinase domain. THL-1 and THL-2 are both expressed in a variety of tissues but show some differences in steady state mRNA levels, with THL-2 being preferentially expressed in floral tissues. This indicates a more general biological function for these thioredoxins in addition to a potential role as effector molecules in the self-incompatibility signal cascade.

Amino Acid Sequence↗
PubMed1995

Regulation of sialyltransferase activities by phosphorylation and dephosphorylation.

The composition of tissue gangliosides is thought to result mainly from the active regulation and selective expression of specific enzymes responsible for their metabolism. In the last few years, we have purified several rat brain sialyltransferases to homogeneity; the availability of these highly purified enzymes enabled us to investigate their regulation and expression at the molecular level. Thus, we studied the regulation of sialyltransferase activities, in particular, CMP-NeuAc:GM1 and CMP-NeuAc:LacCer sialyltransferases by a phosphorylation/dephosphorylation mechanism. Protein kinase C was added to a standard enzyme assay mixture containing [gamma-32P]ATP, and the activity of the enzyme was measured after various incubation times. We found that treatment of several sialyltransferases by protein kinase C decreased their activities in a time-dependent manner. Analyses of 32P-labeled amino acids revealed that the major phosphorylation site of CMP-NeuAc:GM1 alpha 2-->3 sialyltransferase (ST-IV) was serine and that for CMP-NeuAc:LacCer alpha 2-->3 sialyltransferase (ST-I) was primarily threonine. Partial recovery of the enzyme activity could be achieved by treatment of the phosphorylated sialyltransferases with rat brain protein phosphatase. We conclude that the activities of sialyltransferases can be modulated by protein kinase C and protein phosphatase and this may represent a potential regulatory mechanism for ganglioside biosynthesis.

Adenosine Triphosphate↗
PubMed1995

Effects of growth hormone antagonists on 3T3-F442A preadipocyte differentiation.

We have previously shown that a bovine (b) GH antagonist, bGH-M8, which possesses three amino acid substitutions in its third alpha-helix, inhibits mouse 3T3-F442A preadipocyte differentiation. In the current studies, we used the bGH and human (h) GH analogs with single amino acid substitution, bGH-G119R and hGH-G120R, for determining their biological activity using the preadipocyte differentiation assay. Short-term and long-term GH-inducible events were studied during adipose differentiation, including late marker gene expression (adipocyte protein 2), immediate early gene induction (c-fos), and tyrosine phosphorylation of intracellular proteins. The results demonstrated that these GH analogs not only failed to induce these three events, but also antagonized GH induction of c-fos expression and phosphorylation of proteins of apparent molecular mass of 95 kDa. Our present study agrees with the notion that GH must bind to the GH receptor via site one and with a second GH receptor molecule (or with some yet unidentified 'second target') through GH binding site two. This interaction is important for subsequent GH-dependent biological events.

Adipocytes↗
PubMed1994

[Changes in erythrocyte fluidity, fragility and deformability and serum lipid peroxide content in early burn period].

We have observed RBC membrane fluidity, serum lipid peroxide, RBC deformability and fragility in 10 burn patients on PBD 2.3-5 and 6-10. The results showed that there was a reduction of RBC membrane fluidity and, on the contrary, there was an elevation in the contents of serum lipid peroxide and RBC deformability and fragility (All P < 0.01). We consider that damage of RBC membrane by free radicals may be one of the reasons of the above changes, and anti-free radical drugs may be beneficial in protecting RBC structure and functions and blood circulation.

Adult↗
PubMed1993

Purification and characterization of CMP-N-acetylneuraminic acid:lactosylceramide (alpha 2-3) sialyltransferase (GM3-synthase) from rat brain.

CMP-N-acetylneuraminic acid:lactosylceramide (alpha 2-3) sialyltransferase (GM3-synthase) was purified to homogeneity from a Triton CF-54 extract of young rat brain. The enzyme was separated by affinity chromatography on CDP-Sepharose column and resolved by linear NaCl gradient elution from the same adsorbent. Final purification of GM3-synthase was achieved by chromatography on a "lactosylceramide acid"-Sepharose column and specific elution with lactosylceramide. The enzyme activity was highest at pH 6.5 and required the presence of Triton CF-54 (0.15%) and Mn2+ (10 mM) for its full activity. The product of the reaction catalyzed by the enzyme was identified as GM3 based on its mobility on thin layer chromatographic plates using two different solvent systems. Comparison with several glycolipid substrates showed high specificity of GM3-synthase for lactosylceramide. The apparent Km value for lactosylceramide and CMP-N-acetylneuraminic acid were 80 and 210 microM, respectively. The apparent molecular mass of the enzyme determined on SDS-polyacrylamide gel electrophoresis was 76 kDa.

Animals↗