Biomedical subjects

Y Tang

Publications and source records attributed to Y Tang.

At least 199 records · Page 11Linked to original sources

PubMed1999

Effects of L-tetrahydropalmatine on energy metabolism, endothelin-1 and NO during acute cerebral ischemia-reperfusion of rats.

To investigate the effects of L-tetrahydropalmatine (L-THP) on energy metabolism, endothelin-1 (ET-1) and NO during acute cerebral ischemia-reperfusion of rats, 24 Wistar rats were randomly divided into four groups, with 6 rats in each group: sham-operation group, simple ischemia group, ischemia-reperfusion group and treatment group (L-THP group). Cerebral ATP, lactate, ET-1 and NO levels were measured in all groups. Our results showed that treatment with L-THP could increase cerebral ATP levels, but decrease cerebral lactate, ET-1 and NO concentrations during ischemia-reperfusion in the treatment group. It is concluded that L-THP could improve cerebral energy metabolism and protect the injured brain tissue, the mechanism of which might be related to suppression of overproduction of ET-1 and NO.

Animals↗

PubMed1999

Molecular dynamics simulations of the complex between human U1A protein and hairpin II of U1 small nuclear RNA and of free RNA in solution.

RNA-protein interactions are essential to a wide range of biological processes. In this paper, a 0.6-ns molecular dynamics simulation of the sequence-specific interaction of human U1A protein with hairpin II of U1 snRNA in solution, together with a 1.2-ns simulation of the free RNA hairpin, is reported. Compared to the findings in the x-ray structure of the complex, most of the interactions remained stable. The nucleotide U8, one of the seven conserved nucleotides AUUGCAC in the loop region, was unusually flexible during the simulation, leading to a loss of direct contacts with the protein, in contrast to the situation in the x-ray structure. Instead the sugar-phosphate backbone of nucleotide C15 was found to form several interactions with the protein. Compared to the NMR structure of U1A protein complexed with the 3'-untranslated region of its own pre-mRNA, the protein core kept the same conformation, and in the two RNA molecules the conserved AUUGCAC of the loop and the closest CG base pair were located in very similar positions and orientations, and underwent very similar interactions with the protein. Therefore, a common sequence-specific interaction mechanism was suggested for the two RNA substrates to bind to the U1A protein. Conformational analysis of the RNA hairpin showed that the conformational changes of the RNA primarily occurred in the loop region, which is just involved in the sites of binding to the protein and in agreement with experimental observation. Both the loop and stem of the RNA became more ordered upon binding to the protein. It was also demonstrated that the molecular dynamics method could be successfully used to simulate the dynamical behavior of a large RNA-protein complex in aqueous solution, thus opening a path for the exploration of the complex biological processes involving RNA at a molecular level.

Amino Acid Sequence↗

PubMed1999

An immunochemical focus assay to quantify replication competent and defective viruses involved in murine acquired immunodeficiency syndrome.

Murine acquired immunodeficiency syndrome is a lymphoproliferative disease with a concurrently developing immunodeficiency. The disease is induced after injection of supernatant of a chronically infected cell line that releases a mixture of two replication competent virus classes and a replication incompetent virus species responsible for pathogenicity. An immunochemical detection assay for virus infected foci on cell monolayers has been developed. This assay allows quantification of all three types of virus.

Animals↗

PubMed1999

Oxytocinergic innervation of autonomic nuclei controlling penile erection in the rat.

In the rat, spinal autonomic neurons controlling penile erection receive descending pathways that modulate their activity. The paraventricular nucleus of the hypothalamus contributes oxytocinergic fibers to the dorsal horn and preganglionic sympathetic and parasympathetic cell columns. We used retrograde tracing techniques with pseudorabies virus combined with immunohistochemistry against oxytocin and radioligand binding detection of oxytocinergic receptors to evidence the oxytocinergic innervation of thoracolumbar and lumbosacral spinal neurons controlling penile erection. Spinal neurons labelled with pseudo-rabies virus transsynaptically transported from the corpus cavernosum were present in the intermediolateral cell column and the dorsal gray commissure of the thoracolumbar and lumbosacral spinal cord. Confocal laser scanning microscopic observation of the same preparations revealed close appositions between oxytocinergic varicosities and pseudorabies virus-infected neurons, suggesting strongly the presence of synaptic contacts. Electron microscopy confirmed this hypothesis. Oxytocin binding sites were present in the superficial layers of the dorsal horn, the dorsal gray commissure and the intermediolateral cell column in both the thoracolumbar and lumbosacral segments. In rats, stimulation of the paraventricular nucleus induces penile erection, but the link between the nucleus and penile innervation remains unknown. Our findings support the hypothesis that oxytocin, released by descending paraventriculo-spinal pathways, activates proerectile spinal neurons.

Animals↗

PubMed1999

Crystal structure of the complex formed between bovine beta-trypsin and MCTI-A, a trypsin inhibitor of squash family, at 1.8-A resolution.

The stoichiometric complex formed between bovine beta-trypsin and Momordica charantia, Linn. Cucurbitaceae trypsin inhibitor A (MCTI-A) was crystallized and its X-ray crystal structure was refined to a final R value of 0.179 using data of 7.0- to 1.8-A resolution. Combination with results on the complex of MCTI-A with porcine trypsin gives the sequence of MCTI-A definitely, of which 13 residues are conserved compared with other squash family trypsin inhibitors. Its spatial structure and the conformation of its primary binding segment from Cys3I (P3) to Glu7I (P3'), which contains a reactive scissile bond Arg5I C-Ile6I N, were found to be very similar to the other squash family proteinase inhibitors.

Amino Acid Sequence↗

PubMed1999

The kinetic origins of the restriction point in the mammalian cell cycle.

A detailed model mechanism for the G1/S transition in the mammalian cell cycle is presented and analysed by computer simulation to investigate whether the kinetic origins of the restriction point (R-point) can be identified. The R-point occurs in mid-to-late G1 phase and marks the transition between mitogen-dependent to mitogen-independent progression of the cell cycle. For purposes of computer simulations, the R-point is defined as the first point in time after mitosis where cutting off mitogen stimulation does not prevent the cell reaching the threshold activity of cyclin-E/cdk2 required for entry into S phase. The key components of the network that generate a dynamic switching behaviour associated with the R-point include a positive feedback loop between cyclin-E/cdk2 and Cdc25A, along with the mutually negative interaction between the cdk inhibitor p27Kip1 and cyclin-E/cdk2. Simulations of the passage through the R-point were carried out and the factors affecting the position of the R-point in G1 are determined. The detailed model also shows various points in the network where the activation of cyclin-E/cdk2 can be initiated with or without the involvement of the retinoblastoma protein.

Animals↗

PubMed1999

Role of nitric oxide and prostaglandins in the potentiating effects of calcitonin gene-related peptide on lipopolysaccharide-induced interleukin-6 release from mouse peritoneal macrophages.

Previous data from our laboratory have shown that calcitonin gene-related peptide (CGRP) has a potentiating effect on lipopolysaccharide-(LPS) induced interleukin-6 (IL-6) release from mouse macrophages. However, the mechanism of this effect was not clear. Since the nitric oxide (NO) and prostaglandins (PGs) induced by LPS might modulate IL-6 release, we examined whether NO and PGs were also involved in the potentiating effect of rat CGRP (rCGRP) on LPS-induced IL-6 release from mouse macrophages. The IL-6 level in the medium was measured by enzyme-linked immunosorbent assay. Accumulation of NO was assessed by measuring the presence of nitrite by the Greiss reaction. PGI2 was assessed by measuring the formation of 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) by radioimmunoassay. The results showed that the potentiating effect of rCGRP (0.1 nm) on LPS-induced IL-6 release was significantly inhibited by either 100 micrometers NG-monomethyl-L-arginine acetate (L-NMMA; an inhibitor of NO synthase) or 10 micrometers indomethacin (an inhibitor of cyclo-oxygenase). The LPS-induced NO and PGI2 production from these cells was increased significantly by rCGRP at 0.01-10 nm in a concentration-dependent manner, which was blocked by L-NMMA and indomethacin. These results suggest that rCGRP enhances the NO production elicited by LPS and subsequently increases the PGs production which is involved in the potentiating effect of rCGRP on LPS-induced IL-6 release from the peritoneal macrophages in the mouse.

Analysis of Variance↗

PubMed1999

The genital atrium as a good taxonomic character to distinguish between species of phlebotomine sandflies (Diptera: Psychodidae) from Venezuela.

The shape and size of the genital atria of 17 phlebotomine sandflies from Venezuela were examined. The atria were found to express constant characters among individuals of the same species and to be sufficiently different between species to allow taxonomic separation. The spines on the genital armature are described and the characters that can be used to classify individual specimens to species level identified. It is suggested that these characters can be of use on specimens where the spermathecae have been lost or where cryptic species are concerned. Dissection procedures to display the atrium are given.

Animals↗

PubMed1999

A stop-codon mutation in the human mtDNA cytochrome c oxidase I gene disrupts the functional structure of complex IV.

We have identified a novel stop-codon mutation in the mtDNA of a young woman with a multisystem mitochondrial disorder. Histochemical analysis of a muscle-biopsy sample showed virtually absent cytochrome c oxidase (COX) stain, and biochemical studies confirmed an isolated reduction of COX activity. Sequence analysis of the mitochondrial-encoded COX-subunit genes identified a heteroplasmic G-->A transition at nucleotide position 6930 in the gene for subunit I (COX I). The mutation changes a glycine codon to a stop codon, resulting in a predicted loss of the last 170 amino acids (33%) of the polypeptide. The mutation was present in the patient's muscle, myoblasts, and blood and was not detected in normal or disease controls. It was not detected in mtDNA from leukocytes of the patient's mother, sister, and four maternal aunts. We studied the genetic, biochemical, and morphological characteristics of transmitochondrial cybrid cell lines, obtained by fusing of platelets from the patient with human cells lacking endogenous mtDNA (rho0 cells). There was a direct relationship between the proportion of mutant mtDNA and the biochemical defect. We also observed that the threshold for the phenotypic expression of this mutation was lower than that reported in mutations involving tRNA genes. We suggest that the G6930A mutation causes a disruption in the assembly of the respiratory-chain complex IV.

Adult↗

PubMed1999

Effects of environmental estrogens on tumor necrosis factor alpha-mediated apoptosis in MCF-7 cells.

Environmental estrogens represent a class of compounds which have been shown to mimic the effects or activity of the naturally occurring ovarian hormone 17beta-estradiol. Given the role of 17beta-estradiol in cell survival in a number of systems, we wished to determine if environmental estrogens protect MCF-7 cells from apoptosis. Here we demonstrate that the organochlorine pesticides o, p' DDT and alachlor, like 17beta-estradiol, have the ability to suppress tumor necrosis factor alpha (TNF)-induced apoptosis in estrogen receptor (ER)-positive MCF-7 breast carcinoma cells. These compounds, however, did not affect TNF-induced apoptosis of the ER-negative MDA-MB-231 cell line. The ability of these compounds to suppress apoptosis in MCF-7 cells was correlated with an ER-dependent increase in Bcl-2 expression. Taken together these results demonstrate that estrogenic organochlorine pesticides like o, p' DDT and alachlor may partially mimic the primary endogenous estrogen, 17beta-estradiol, and function to suppress apoptosis in ER-responsive cells.

Apoptosis↗

PubMed1999

Novel alternatively spliced isoforms of the neurofibromatosis type 2 tumor suppressor are targeted to the nucleus and cytoplasmic granules.

We cloned novel splice variants Mer150, Mer151 and Mer162 of the neurofibromatosis 2 (NF2) tumor suppressor, which demonstrate a tissue-specific and development-specific expression pattern. Isoform Mer150 is created by cryptic splicing from exon 8 to 14 and represents an N-terminal truncation of 259 residues. Mer151 is characterized by in-frame splicing out of several exons and a modified C-terminus due to a frameshift in exons 13+14 and premature termination. Mer162 represents a head-to-tail isoform resulting from in-frame skipping of exons 5-16. As a common feature, the alpha-helical domain and a variable proportion of the ERM homology domain are spliced out in these isoforms. To investigate differences in subcellular localization, we expressed epitope-tagged cDNA constructs of the wild-type NF2 as well as of the three alternatively spliced transcripts in NIH 3T3 cells by nuclear microinjection or lipid-mediated transfection. Subcellular localization of Mer151 in filopodia and ruffling membranes was similar to the wild-type NF2. Mer151, however, was targeted to the nucleus, which was not observed for wild-type NF2, Mer150 or Mer162. A putative nuclear localization signal created by alternative splicing was identified in Mer151. In contrast to Mer151, Mer150 and Mer162 were not found in regions of the plasma membrane, but localized to a granular intracellular compartment. The results suggest that the recently described actin-binding domain in exon 10, but not the presence or absence of exons 2+3, is relevant for subcellular targeting. Although the NF2 protein is known as a cytoskeletal linker, additional functions in a cytoplasmic compartment and in the nucleus may exist.

3T3 Cells↗

PubMed1999

Role of genotypic analysis of the thymidine kinase gene of herpes simplex virus for determination of neurovirulence and resistance to acyclovir.

Mutations in the thymidine kinase (TK) gene of herpes simplex virus (HSV) have been associated with resistance to acyclovir (ACY) and possible recognition of neurotropic strains. We sequenced a 335-bp segment of the TK gene to determine the frequency of mutations in HSV strains recovered from dermal, genital, and cerebrospinal fluid (CSF) specimens (n = 200; 102 HSV type 1 [HSV-1] 98 HSV-2 strains). Four polymorphic sites were detected in HSV-1 strains; C513T, A528G, C575T, and C672T. Among the polymorphisms, only C575T resulted in a change of amino acid sequence (residue 192, Ala-->Val). For HSV-2 strains, only one polymorphism (G420T) which resulted in an amino acid substitution (residue 139, Leu-->Phe) was detected. Phenotypic determination of resistance to ACY by a plaque reduction assay of 48 HSV isolates was not correlated with the sequence results of 11 strains in that 7 of these with genotypic polymorphisms were susceptible to the drug in vitro. In addition, of 32 ACY-resistant HSV strains, 28 (87.5%) had no polymorphisms detected in the 335-bp amplicon of the TK gene. There was no statistical difference in the frequency of polymorphisms according to the source of the specimens. We conclude that the detection of nucleic acid polymorphisms in a previously implicated 335-bp segment of the TK gene cannot be interpreted as indicative of either ACY resistance or neurotropism of HSV strains from dermal, genital, and CSF sources.

Acyclovir↗

PubMed1999

Cellular motor protein KIF-4 associates with retroviral Gag.

Previously we demonstrated that murine retroviral Gag proteins associate with a cellular motor protein, KIF-4. Using the yeast two-hybrid assay, we also found an association of KIF-4 with Gag proteins of Mason-Pfizer monkey virus (MPMV), simian immunodeficiency virus (SIV), and human immunodeficiency virus type 1 (HIV-1). Studies performed with mammalian cell systems confirmed that the HIV-1 Gag protein associates with KIF-4. Soluble cytoplasmic proteins from cells infected with recombinant vaccinia virus expressing the entire Gag-Pol precursor protein of HIV-1 or transfected with HIV-1 molecular clone pNL4-3 were fractionated by sucrose gradient centrifugation and further separated by size-exclusion and anion-exchange chromatographies. KIF-4 and HIV-1 Gag cofractionated in both chromatographic separations. Immunoprecipitation assays have also verified the KIF-4-Gag association. KIF-4 binds mainly to the Gag precursor (Pr55 Gag) and a matrix-capsid processing intermediate (Pr42) but not to other processed Gag products. The binding of Gag is mediated by a domain of KIF-4 proximal to the C terminus. These results, and our previous studies, raise the possibility that KIF-4 may play an important role in retrovirus Gag protein transport.

Animals↗

PubMed1999

Signals from the Ras, Rac, and Rho GTPases converge on the Pak protein kinase in Rat-1 fibroblasts.

Ras plays a key role in regulating cellular proliferation, differentiation, and transformation. Raf is the major effector of Ras in the Ras > Raf > Mek > extracellular signal-activated kinase (ERK) cascade. A second effector is phosphoinositide 3-OH kinase (PI 3-kinase), which, in turn, activates the small G protein Rac. Rac also has multiple effectors, one of which is the serine threonine kinase Pak (p65(Pak)). Here we show that Ras, but not Raf, activates Pak1 in cotransfection assays of Rat-1 cells but not NIH 3T3 cells. We tested agents that activate or block specific components downstream of Ras and demonstrate a Ras > PI 3-kinase > Rac/Cdc42 > Pak signal. Although these studies suggest that the signal from Ras through PI 3-kinase is sufficient to activate Pak, additional studies suggested that other effectors contribute to Pak activation. RasV12S35 and RasV12G37, two effector mutant proteins which fail to activate PI 3-kinase, did not activate Pak when tested alone but activated Pak when they were cotransfected. Similarly, RacV12H40, an effector mutant that does not bind Pak, and Rho both cooperated with Raf to activate Pak. A dominant negative Rho mutant also inhibited Ras activation of Pak. All combinations of Rac/Raf and Ras/Raf and Rho/Raf effector mutants that transform cells cooperatively stimulated ERK. Cooperation was Pak dependent, since all combinations were inhibited by kinase-deficient Pak mutants in both transformation assays and ERK activation assays. These data suggest that other Ras effectors can collaborate with PI 3-kinase and with each other to activate Pak. Furthermore, the strong correlation between Pak activation and cooperative transformation suggests that Pak activation is necessary, although not sufficient, for cooperative transformation of Rat-1 fibroblasts by Ras, Rac, and Rho.

3T3 Cells↗

PubMed1999

Optimal protocol for injection of contrast material at MR angiography: study of healthy volunteers.

Forty healthy volunteers, matched for age and body weight, underwent abdominal magnetic resonance angiography with gadopentetate dimeglumine administered by using a power injector. Injection rates were 0.3, 1.0, 2.0, or 3.0 mL/sec. Contrast material doses were 0.1 (single dose) or 0.2 (double dose) mmol/kg. Increased contrast enhancement in the aorta and minimum arteriovenous overlap can be achieved with high flow rate and double-dose injection.

Adult↗

PubMed1999

Detection of hepatocellular carcinoma arising in cirrhotic livers: comparison of gadolinium- and ferumoxides-enhanced MR imaging.

OBJECTIVE: We prospectively compared the detectability of hepatocellular carcinoma (HCC) arising in cirrhotic livers using dynamic gadolinium-enhanced fast low-angle shot (FLASH), ferumoxides-enhanced T2-weighted turbo spin-echo, and ferumoxides-enhanced T2*-weighted FLASH MR imaging. SUBJECTS AND METHODS: Fifty-three patients with HCC (32 men and 21 women) who were 33-86 years old (mean, 63 years old) were enrolled in a prospective MR study to assess hepatic lesions using both gadopentetate dimeglumine and ferumoxides. Dynamic gadolinium-enhanced imaging was obtained before and 30, 60, and 180 sec after rapid bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Ferumoxides-enhanced T2-weighted turbo spin-echo imaging and ferumoxides-enhanced T2*-weighted FLASH imaging were performed between 30 min and 2 hr after i.v. infusion of ferumoxides (10 micromol/kg). Images were analyzed qualitatively and quantitatively. A receiver operating characteristic curve study was performed to compare the diagnostic value of gadolinium-enhanced imaging with that of ferumoxides-enhanced imaging for the detection of HCC. RESULTS: Quantitative analysis revealed a significantly higher percentage of signal-intensity loss and higher liver-lesion contrast-to-noise ratio on ferumoxides-enhanced T2*-weighted FLASH imaging than on ferumoxides-enhanced T2-weighted turbo spin-echo imaging. The percentage of signal-intensity loss and liver-lesion contrast-to-noise ratio on ferumoxides-enhanced images was significantly higher in patients with mild liver cirrhosis (Child's class A) than in patients with severe liver cirrhosis (Child's class C). Qualitative analysis showed that dynamic gadolinium-enhanced images revealed significantly higher lesion conspicuity than did ferumoxides-enhanced T2-weighted turbo spin-echo images. According to receiver operating characteristic analysis, dynamic gadolinium-enhanced FLASH imaging achieved the highest sensitivity, and ferumoxides-enhanced T2*-weighted FLASH imaging was the second most sensitive. We found that ferumoxides-enhanced turbo spin-echo imaging was the least valuable technique for revealing HCC lesions. Gadolinium-enhanced imaging revealed more HCC lesions than did ferumoxides-enhanced imaging, particularly for lesions smaller than 2 cm in diameter. CONCLUSION: Ferumoxides-enhanced imaging revealed fewer findings, such as lesion conspicuity of HCCs arising in cirrhotic livers, than did gadolinium-enhanced FLASH imaging.

Adult↗

PubMed1999

Improvement in insulin resistance and the restoration of reduced phosphodiesterase 3B gene expression by pioglitazone in adipose tissue of obese diabetic KKAy mice.

Phosphodiesterase (PDE) 3B is a key enzyme in the mediation of the antilipolytic action of insulin in adipocytes, and activation of this molecule results in a reduced output of free fatty acids (FFAs). An elevation of serum FFAs is known to cause insulin resistance in skeletal muscle and liver, which could be the primary cause of type 2 diabetes. To elucidate whether PDE3B is involved in this disease, we examined the PDE3B gene expression in epididymal fat tissues of obese insulin-resistant diabetic KKAy mice. We also examined the effect of an insulin-sensitizing drug, pioglitazone, on this gene expression. In adipose tissue of KKAy mice, PDE3B mRNA and its corresponding protein were reduced to 48 and 43% of those in C57BL/6J control mice. Basal and insulin-stimulated membrane-bound PDE activities were also decreased to 50 and 36% of those in the controls, respectively. Pioglitazone increased both PDE3B mRNA and protein levels by 1.8-fold of those in untreated KKAy mice. Basal and insulin-induced membrane-bound PDE activities were also increased by 1.6- and 2.0-fold, respectively. Pioglitazone reduced the elevated levels of serum insulin, glucose, FFAs, and triglyceride in KKAy mice. Thus, the reduced PDE3B gene expression in adipose tissues could be the primary event in the development of insulin resistance in KKAy mice, which was improved by pioglitazone possibly because of the restoration of the reduced PDE3B gene expression.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Effects of coenzyme Q10 on myocardial protection during cardiac valve replacement and scavenging free radical activity in vitro.

BACKGROUND: To evaluate the effects of CoQ10 on myocardial protection in patients undergoing cardiac valve replacement and direct scavenging free radicals activity in vitro. METHODS: Twenty-four patients were randomly divided into two groups. Twelve patients in the CoQ10 group received intravenous and intracoronary CoQ10-treated "round the operative period". Twelve patients in the control group received no CoQ10-treatment. MEASURES: Plasma malondialdehyde (MDA) concentration, erythrocyte superoxide dismutase (SOD) activity, and serum cardiac isoenzyme of creatine kinase (CK-MB) were measured in the perioperative and postoperative period. The effects of CoQ10 direct scavenging free radicals were determined with electron spin resonance (ESR) and spin-trapping techniques by an in vitro study. RESULTS: Plasma MDA concentration and serum CK-MB levels in the CoQ10 group were significantly lower than those in the control group. Erythrocyte SOD activity in the CoQ10 group was significantly higher than that in the control group. CoQ10 showed an obvious hydroxyl radical scavenging activity, but it could not scavenge superoxide anion radicals. CONCLUSIONS: These findings demonstrated that the use of intravenous and intracoronary CoQ10-treatment may play a more beneficial protective role during cardiac valve replacement through its antioxidant properties and membrane stabilization, as well as through its ability to scavenge hydroxyl radicals directly.

Adult↗