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Biomedical subjects

Y Guo

Publications and source records attributed to Y Guo.

At least 91 records · Page 5Linked to original sources
PubMed2001

Polypeptide growth factors and phorbol ester induce progressive ankylosis (ank) gene expression in murine and human fibroblasts.

Polypeptide growth factors promote cellular proliferation by binding to specific plasma membrane-anchored receptors. This interaction triggers the phosphorylation of signal transducing molecules and the transcriptional activation of numerous genes. We have used a differential display approach to identify fibroblast growth factor (FGF)-1-inducible genes in murine NIH 3T3 fibroblasts. Here we report that one of these genes encodes ank, a type IIIa transmembrane protein reported to function in cells as an inorganic pyrophosphate transporter. FGF-1 induction of ank mRNA expression is first detectable at 2 h after growth factor addition and is dependent on de novo RNA and protein synthesis. Ank gene expression is also upregulated after treating quiescent fibroblasts with several other mitogenic agents (e.g., calf serum or platelet-derived growth factor-BB) or the tumor promoter phorbol 12-myristate 13-acetate. Furthermore, in comparison to parental NIH 3T3 cells, oncogene-transformed NIH 3T3 cells constitutively express elevated levels of ank mRNA. FGF-1 also increases ank gene expression in non-immortalized human embryonic lung fibroblasts. Finally, the murine and human ank genes are expressed in vivo in a tissue-specific manner, with highest levels of mRNA expression found in brain, heart, and skeletal muscle. These results indicate that ank is a growth factor-regulated delayed-early response gene in mammalian cells, and we propose that increased ank expression during cell cycle progression may be necessary to maintain proper intracellular pyrophosphate levels during conditions of high cellular metabolic activity.

3T3 Cells↗
PubMed2001

Expression and localization of protein inhibitor of neuronal nitric oxide synthase in Duchenne muscular dystrophy.

In skeletal muscle fibers, nitric oxide is synthesized by neuronal nitric oxide synthase (nNOS), which normally associates with the dystrophin complex in close proximity to the sarcolemma. Many reports have documented that very low levels of nNOS protein exist in muscle fibers of Duchenne muscular dystrophy (DMD) patients. In this study we investigated the functional significance of PIN (protein inhibitor of nNOS) in targeting of nNOS to the sarcolemma and the association between nNOS and the dystrophin complex in normal and dystrophic muscle fibers. Northern blotting for PIN mRNA in normal mouse muscles and muscles of mdx mice (an animal model of DMD) revealed a significant rise in PIN mRNA in dystrophic muscles compared with normal muscles. Immunohistochemical analysis showed that, in normal mouse muscle fibers, PIN expression was localized at the sarcolemma, peripheral nuclei, and the sarcoplasm. By comparison, PIN protein in muscles from mdx mice was more concentrated around the sarcolemma and central nuclei. The presence of PIN protein expression in muscles from mdx mice was evident despite the significant reduction in nNOS and dystrophin protein expressions in these fibers. In muscle sections of DMD patients, the absence of nNOS protein expression was accompanied by maintained PIN expression. Prominent PIN expression was also detectable in macrophages infiltrating dystrophic muscle fibers both in mdx mice and DMD patients. These results suggest that PIN expression in muscles from mdx mice and DMD patients is controlled by factors different from those involved in the regulation of nNOS and dystrophin. Moreover, our results indicate that PIN is not an integral component of the dystrophin complex inside skeletal muscle fibers.

Animals↗
PubMed2001

Targeted deletion of the A3 adenosine receptor confers resistance to myocardial ischemic injury and does not prevent early preconditioning.

We used mice with genetic disruption of the A3 adenosine receptor (AR) gene (A3AR(-/-)mice) to assess the in vivo role of the A3AR in modulating myocardial ischemia/reperfusion injury and preconditioning (PC). Surprisingly, infarct size induced by 30 min of coronary artery occlusion and 24 h of reperfusion was 35% smaller in A3AR(-/-)compared to wild-type mice (A3AR(+/+)). The reduction in infarct size was not the result of differences in heart rate, body temperature or increased cardiac expression of A1ARs. However, neutrophil infiltration within infarcted regions was less in A3AR(-/-)mice. Furthermore, ischemic PC induced by either a single episode (one 5 min occlusion) or multiple episodes (six 4 min occlusions) of ischemia produced equivalent reductions in infarct size in A3AR(-/-)and A3AR(+/+)mice. These results indicate that, in the mouse, (i) A3ARs play an injurious role during acute myocardial ischemia/reperfusion injury, possibly by exacerbating the inflammatory response, and (ii) A3ARs are not necessary for the development of the early phase of ischemic PC.

Animals↗
PubMed2001

Near-Infrared Spectrum of the A(2)Pi(i)-X(2)Sigma(+) (2,0) Band of CN Studied by Concentration Modulation Laser Spectroscopy.

The rotational structure of (2,0) vibrational band of A(2)Pi(i)-X(2)Sigma(+) transition of CN has been studied by concentration-modulation laser spectroscopy using a Ti:sapphire laser. The CN radical was produced in the ac glow discharge of acetonitrile with helium as the carrier gas. All 12 branches including four new branches have been observed and measured with an absolute accuracy of 0.007 cm(-1) in the region 12 450-12 750 cm(-1). Analysis of the spectra has led to improved molecular parameters of the A(2)Pi(i) (v' = 2) state. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

Sensitivity of unanesthetized chinchilla auditory system to noise burst onset, and the effects of carboplatin.

The gross near-field responses of the auditory nerve and inferior colliculus to noise burst stimuli were recorded through intracranially implanted electrodes in six unanesthetized chinchillas. Responses were studied as a function of stimulus plateau amplitude and rise time, both before and after a systemic dose of 75 mg/kg of carboplatin. Both recording sites showed sensitivity to stimulus level and rise time. Increases in stimulus level and decreases in stimulus rise time each produced increases in the response magnitude, and decreases in response latency. When the stimuli were re-specified as rate of pressure change at sound onset (Pa/s), the amplitude and latency of responses at each site were found to be a direct function of rate of sound pressure change. These data provide the first confirmation in unanesthetized animals of previous single unit observations in barbiturate-anesthetized cats. Carboplatin treatment resulted in a 20-80% loss of inner hair cells, a modest threshold elevation, and a 50-75% reduction in peak response amplitudes. The general patterns of sensitivity to stimulus level and rise time were not markedly affected by carboplatin, nor was the fashion in which response parameters (amplitude and latency) were ruled by rate of pressure change at sound onset.

Acoustic Stimulation↗
PubMed2001

Composition and functional characterization of yeast 66S ribosome assembly intermediates.

The pathway and complete collection of factors that orchestrate ribosome assembly are not clear. To address these problems, we affinity purified yeast preribosomal particles containing the nucleolar protein Nop7p and developed means to separate their components. Nop7p is associated primarily with 66S preribosomes containing either 27SB or 25.5S plus 7S pre-rRNAs. Copurifying proteins identified by mass spectrometry include ribosomal proteins, nonribosomal proteins previously implicated in 60S ribosome biogenesis, and proteins not known to be involved in ribosome production. Analysis of strains mutant for eight of these proteins not previously implicated in ribosome biogenesis showed that they do participate in this pathway. These results demonstrate that proteomic approaches in concert with genetic tools provide powerful means to purify and characterize ribosome assembly intermediates.

Cell Fractionation↗
PubMed2001

Modulation of abscisic acid signal transduction and biosynthesis by an Sm-like protein in Arabidopsis.

The phytohormone abscisic acid (ABA) regulates plant growth and development as well as stress tolerance. The Arabidopsis sad1 (supersensitive to ABA and drought) mutation increases plant sensitivity to drought stress and ABA in seed germination, root growth, and the expression of some stress-responsive genes. sad1 plants are also defective in the positive feedback regulation of ABA biosynthesis genes by ABA and are impaired in drought stress induction of ABA biosynthesis. SAD1 encodes a polypeptide similar to multifunctional Sm-like snRNP proteins that are required for mRNA splicing, export, and degradation. These results suggest a critical role for mRNA metabolism in the control of ABA signaling as well as in the regulation of ABA homeostasis.

Abscisic Acid↗
PubMed2001

The cytotoxic effect of E1B 55-kDa mutant adenovirus on human hepatocellular carcinoma cell lines.

It has been suggested the E1B 55 kDa mutant adenovirus dl1520 can selectively kill p53-deficient human tumor cells. In this study, we examined the cytotoxic effect of dl1520 on nine human hepatocellular carcinoma (HCC) cell lines with different p53 genetic and functional status. The results showed that HCC cell lines with deleted or mutant p53 gene and reduced p53 transcriptional activities were more susceptible to dl1520-induced cytolysis. Hep3B (p53-null) and HepG2 (p53-wt) cells were arrested at G2/M phase when cytolysis occurred. Cyclin-dependent kinase inhibitor (CDKI) p21(Waf-1/Cip-1) was downregulated 24 hours after dl1520 infection in HepG2 cells and increased when cytolysis occurred. No p21 expression was detected in Hep3B cells. DNA fragmentation was found in both Hep3B and HepG2 cells after dl1520 infection. Bax expression increased in dl1520-infected HepG2 cells but not in Hep3B cells. Notably, three Bax-like proteins, molecular mass around 40 to 80 kDa, accumulated 48 hours after adenovirus infection in Hep3B cells but not in HepG2 cells. These results suggest that the susceptibility of HCC cells to dl1520-induced cytolysis is related to both p53 genotype and functional status, and is mediated by both cell cycle disturbance and apoptosis.

Adenoviridae↗
PubMed2001

Activation of extracellular signal-regulated kinases potentiates hemin toxicity in astrocyte cultures.

Hemin is present in intracranial hematomas in high micromolar concentrations and is a potent, lipophilic oxidant. Growing evidence suggests that heme-mediated injury may contribute to the pathogenesis of CNS hemorrhage. Extracellular signal-regulated kinases (ERKs) are activated by oxidants in some cell types, and may alter cellular vulnerability to oxidative stress. In this study, the effect of hemin on ERK activation was investigated in cultured murine cortical astrocytes, and the consequence of this activation on cell viability was quantified. Hemin was rapidly taken up by astrocytes, and generated reactive oxygen species (ROS) within 30 min. Increased immunoreactivity of dually phosphorylated ERK1/2 was observed in hemin-treated cultures at 30-120 min, without change in total ERK. Surprisingly, ERK activation was not attenuated by concomitant treatment with antioxidants (U74500A or 1,10-phenanthroline) at concentrations that blocked ROS generation. Cell death commenced after 2 h of hemin exposure and was reduced by antioxidants and by the caspase inhibitor Z-VAD-FMK. Cytotoxicity was also attenuated by MEK inhibition with PD98059 or U0126 at concentrations that were sufficient to prevent ERK activation. Whereas the effect of Z-VAD-FMK on cell survival was transient, the effect of MEK inhibitors was long-lasting. MEK inhibitors had no effect on cellular hemin uptake or subsequent ROS generation. The present results suggest that hemin activates ERK in astrocytes via a mechanism that is independent of ROS generation. This activation sensitizes astrocytes to hemin-mediated oxidative injury.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Molecular characterization of functional domains in the protein kinase SOS2 that is required for plant salt tolerance.

The SOS3 (for SALT OVERLY SENSITIVE3) calcium binding protein and SOS2 protein kinase are required for sodium and potassium ion homeostasis and salt tolerance in Arabidopsis. We have shown previously that SOS3 interacts with and activates the SOS2 protein kinase. We report here the identification of a SOS3 binding motif in SOS2 that also serves as the kinase autoinhibitory domain. Yeast two-hybrid assays as well as in vitro binding assays revealed a 21-amino acid motif in the regulatory domain of SOS2 that is necessary and sufficient for interaction with SOS3. Database searches revealed a large family of SOS2-like protein kinases containing such a SOS3 binding motif. Using a yeast two-hybrid system, we show that these SOS2-like kinases interact with members of the SOS3 family of calcium binding proteins. Two-hybrid assays also revealed interaction between the N-terminal kinase domain and the C-terminal regulatory domain within SOS2, suggesting that the regulatory domain may inhibit kinase activity by blocking substrate access to the catalytic site. Removal of the regulatory domain of SOS2, including the SOS3 binding motif, resulted in constitutive activation of the protein kinase, indicating that the SOS3 binding motif can serve as a kinase autoinhibitory domain. Constitutively active SOS2 that is SOS3 independent also was produced by changing Thr(168) to Asp in the activation loop of the SOS2 kinase domain. Combining the Thr(168)-to-Asp mutation with the autoinhibitory domain deletion created a superactive SOS2 kinase. These results provide insights into regulation of the kinase activities of SOS2 and the SOS2 family of protein kinases.

Adaptation, Physiological↗
PubMed2001

Connexin expression by alveolar epithelial cells is regulated by extracellular matrix.

Extracellular matrix (ECM) proteins promote attachment, spreading, and differentiation of cultured alveolar type II epithelial cells. The present studies address the hypothesis that the ECM also regulates expression and function of gap junction proteins, connexins, in this cell population. Expression of cellular fibronectin and connexin (Cx) 43 increase in parallel during early type II cell culture as Cx26 expression declines. Gap junction intercellular communication is established over the same interval. Cells plated on a preformed, type II cell-derived, fibronectin-rich ECM demonstrate accelerated formation of gap junction plaques and elevated gap junction intercellular communication. These effects are blocked by antibodies against fibronectin, which cause redistribution of Cx43 protein from the plasma membrane to the cytoplasm. Conversely, cells cultured on a laminin-rich ECM, Matrigel, express low levels of Cx43 but high levels of Cx26, reflecting both transcriptional and translational regulation. Cx26 and Cx43 thus demonstrate reciprocal regulation by ECM constituents.

Animals↗
PubMed2001

An electrochemical quartz crystal impedance study on the rising of an aqueous solution meniscus for a partially immersed gold electrode during the electrochemical reduction of oxygen.

An electrochemical quartz crystal impedance system (EQCIS) was used to study the resonance behavior of an AT-cut 9-MHz piezoelectric quartz crystal (PQC) with its Au electrode partially immersed in KCl, Na2SO4 and NaClO4 aqueous solutions, respectively. An in situ determination of the immersed area and the height of the electrode was achieved by simultaneous measurements of the PQC electroacoustic admittance and the electrochemical impedance. The rising of the solution meniscus for a gold electrode partially immersed in aqueous solutions was found at oxygen reduction potentials and evaluated versus the electrolyte, electrolyte concentration, solution pH and oxygen concentration. The solution meniscus rising was explained based on a lowering of the contact-angle hysteresis and a continued collection of the water product at the solid-gas-solution interface during oxygen reduction.

Journal Article↗
PubMed2001

t(8;21;8)(p23;q22;q22): a new variant form of t(8;21) translocation in acute myeloblastic leukemia with maturation.

The complex variants of t(8;21) involving chromosomes 8 and 21 as well as a variable chromosome account for 1.1-5% of acute myeloid leukemia (AML) patients. This paper reports a case of AML-M2 with t(8;21;8) translocation for the first time. The patient was a female, aged 47 years. Her myelogram was compatible with AML-M2. Chromosome study using R-banding technique revealed a karyotype 46, XX, t(8;8)(p23;q22). Dual-color FISH assay with two probes P1 164(green signal) and YAC 225B8 (red signal) both of which closely located on the 8q showed that one yellow signal consisting of a green signal and a red signal and one red signal appeared on the long and the short arm of the same der(8) chromosome, respectively, further confirming this translocation occurred between both homologous chromosomes 8. RT-PCR analysis detected the AML1/ETO fusion transcript in our patient, thus indicating that this chromosomal aberration was, in fact, a complex three-way rearrangement t(8;21;8)(p23;q22;q22). In conclusion, combining conventional karyotype, FISH or RT-PCR analyses is a rational strategy for identification of the complex variants of t(8;21) translocation.

Bone Marrow Cells↗
PubMed2001

Extremophilic orgainisms as and unexplored source fo antifungal compounds.

Extracts of the biomasses and fermentation broths of 217 extremophilic microorganisms isolated from a number of locales were screened for antifungal activity using whole-cell and mechanism-based in vitro assays. Importantly, eleven broth extracts had activity against several Candida species and Aspergillus fumigatus in whole-cell in vitro assays. One broth specifically inhibited (1,3)beta-glucan synthase activity and four specifically inhibited ketol-isomerase activity, suggesting a mode of action of the antifungal compound(s) present in these extracts. The extract from one thermophile, a novel species of Pseudomonas, was fractionated, an active compound purified and its structure determined. The compound was identified as pyochelin, a previously identified iron-binding compound with heretofore undescribed antifungal activity. To our knowledge, this is the first report demonstrating that extremophiles synthesize compounds that have antifungal activity.

Antifungal Agents↗
PubMed2001

Genetic mutations of precore region of hepatitis B virus in hepatitis B e antigen-negative patients with fulminant hepatitis B and translation of precore variants in vitro.

OBJECTIVE: To detect mutations in precore region of hepatitis B virus of HBeAg negative- patients with fulminant hepatitis and to determine the effect of T1862 mutants on synthesis of precursor of hepatitis B e antigen. METHODS: The entire precore and core region were amplified from sera of nine HBeAg negative-patients with fulminant hepatitis B by polymerase chain reaction (PCR). PCR products were cloned into plasmid pUC18, and sequencing for analysis of precore mutations. Precore and core sequence of T1862 variant were also cloned into expression plasmid pGEMT for in vitro transcription and translation study on synthesis and procession of e antigen. RESULTS: Three variants, A1896, A1899 and T1862, whose nucleotide mutation led to amino acids substitutions, were detected in patients with fulminant hepatitis. T1862 variant didn't effect the synthesis of precursor of e antigen. Also there was no variant detected in precore region of hepatitis B virus in two patients. CONCLUSIONS: The causes for negative of e antigen in fulminant hepatitis patients may be partially explained by precore mutation of A1896 and T1862, and the latter variant may effect the process of precursor of e antigen, rather than the synthesis of precursor protein.

Base Sequence↗
PubMed2001

[Effect of five kinds of vegetable seed oil on serum lipid and lipid peroxidation in rats].

The effects of vegetable seed oil on hyperlipidemia induced by high lipid diet in rats. Male adult Wistar rats were fed on the test diet containing 94% high lipid diet and 6% lard pinon seed oil, perilla seed oil, blackcurrent seed oil, borage seed oil and evening primrose seed oil respectively for 3 weeks. The results showed that the vale of trilyceride(TG), total cholesterol(TC), low density lipoprotein cholesterol (LDL-C), LDL-C/HDL-C(high density lipoprotein cholesterol) ratio increased and the vale of HDL-C/TC ratio and lecithin-cholesterol acyltransferase(LCAT) activity decreased in the groups with vegetable seed oil were less than that of the control group. The results suggested that all the five kinds of vegetable seed oil had the effect of regulating lipid metabolism of hyperlipidemia rats to some extent. Pinon seed oil and borage seed oil may be well suited for the prevention of atherosclerosis.

Animals↗