Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 559 records · Page 31Linked to original sources

PubMed1998

AT1 receptor-mediated nuclear translocation of Raf-1 in brain neurons.

Angiotensin II (Ang II) interacts with the neuronal AT1 receptor subtype and initiates a cascade of signaling events involving activation of Ras-Raf-1-MAP kinase. Raf-1-dependent activation of mitogen-activated protein kinase (MAPK) is the key in the chronic norepinephrine neuromodulatory actions of Ang II and is associated with the translocation of MAPK into the nucleus. In view of these observations, this study was designed to determine if Ang II causes cellular redistribution of Raf-1 in neuronal cells. Most of Raf-1 was localized in the cytoplasmic compartment in neurons. Ang II treatment resulted in a time-dependent increase in the translocation of immunoreactive Raf-1 from the cytoplasm into the nucleus. A fourfold increase was observed in 15 min. The nuclear sequestration of Raf-1 was blocked by losartan, an AT1 receptor-specific antagonist, and not by PD123319, an AT2 receptor-specific antagonist. Confocal microscopic analysis of immunofluorescence data confirmed the nuclear translocation and further showed that Raf-1 was exclusively localized into the nucleolus. These observations demonstrate, for the first time, that Ang II stimulates Raf-1 targeting into the neuronal nucleus, and they suggest that this translocation may play a direct role in the transcriptional regulation of Ang II actions.

Angiotensin I↗

PubMed1998

Coupled effects of mass transfer and uptake kinetics on in vivo microdialysis of dopamine.

Voltammetric microelectrodes and microdialysis probes were used simultaneously to monitor extracellular dopamine in rat striatum during electrical stimulation of the medial forebrain bundle. Microelectrodes were placed far away (1 mm) from, immediately adjacent to, and at the outlet of microdialysis probes. In drug-naive rats, electrical stimulation (45 Hz, 25 s) evoked a robust response at microelectrodes far away from the probes, but there was no response at microelectrodes adjacent to and at the outlet of the probes. After nomifensine administration (20 mg/kg i.p.), stimulation evoked robust responses at all three microelectrode placements. These results demonstrate first that evoked release in tissue adjacent to microdialysis probes is suppressed in comparison with evoked release in tissue far away from the probes and second that equilibration of the dopamine concentration in the extracellular fluid adjacent to and far away from the probes is prevented by the high-affinity dopamine transporter. Hence, models of microdialysis, which assume the properties of tissue to be spatially uniform, require modification to account for the distance that separates viable sites of evoked dopamine release from the probe. We introduce new mass transfer resistance parameters that qualitatively explain the observed effects of uptake inhibition on stimulation responses recorded with microdialysis and voltammetry.

Animals↗

PubMed1998

Intragastric intubation: important aspects of the model for administration of ethanol to rat pups during the postnatal period.

One technique for the controlled delivery of ethanol to neonatal rat pups is intragastric intubation. Often, the vehicle used for delivery of ethanol is composed of a nutrient mixture to compensate for decreased suckling or other possible nutritional compromise. This study analyzed the selection of nutrient vehicle, the combination of experimental treatment groups within a litter, and the overall litter size on the growth rate of ethanol-intubated and intubated-control pups, compared with mother-raised control pups. Sprague-Dawley rat pups were raised in litters of 8 or 10, and administered ethanol by intragastric intubation with 20% (v/v) Sustacal or 80% (v/v) Intralipid-II nutrient vehicle. Pups were treated between postnatal days 2 and 10, and body weight was analyzed on day 10. Pups were assigned to a treatment group as either intubated ethanol, intubated control, or nonintubated mother-raised controls. Experimental comparison by statistical analyses was performed to identify the optimal treatment design (mixed treatment groups in a single litter or a single treatment group per litter), the optimal vehicle (Sustacal or Intralipid-II), and the optimal number of pups per litter (8 vs. 10). The analyses demonstrate that the mixing of intubated control, intubated ethanol, and nonintubated mother-raised control treatment groups within a single litter introduced an uncontrolled variable that confounded measurement of ethanol-specific alterations. The sensitivity of treatment groups to inclusion in mixed litters was dependent on the nutrient vehicle and thus nutritional adequacy. Our results suggest that an optimal design was achieved with eight pups per litter. Furthermore, ethanol intubated and intubated control pups grow at a rate identical to parallel litters of eight mother-raised control pups when Intralipid-II is used as nutrient vehicle, and a single treatment group is present in a litter. Optimization of these experimental parameters has provided an excellent neonatal rat model for analysis of specific ethanol effects on brain development during the third trimester.

Animals↗

PubMed1998

A novel serine/threonine protein kinase homologue of Pseudomonas aeruginosa is specifically inducible within the host infection site and is required for full virulence in neutropenic mice.

A genetic locus of Pseudomonas aeruginosa was identified that is highly and specifically inducible during infection of neutropenic mice. This locus, ppkA, encodes a protein that is highly homologous to eukaryote-type serine/threonine protein kinases. A ppkA null mutant strain shows reduced virulence in neutropenic mice compared to the wild type. Overexpression of the PpkA protein greatly inhibited the growth of Escherichia coli or P. aeruginosa. However, a single amino acid change at the catalytic site of the kinase domain eliminated the toxic effect of PpkA on bacterial cells, suggesting that the kinase domain of PpkA is functional within bacterial cells.

Amino Acid Sequence↗

PubMed1998

Id2 promotes apoptosis by a novel mechanism independent of dimerization to basic helix-loop-helix factors.

Members of the helix-loop-helix (HLH) family of Id proteins have demonstrated roles in the regulation of differentiation and cell proliferation. Id proteins inhibit differentiation by HLH-mediated heterodimerization with basic HLH transcription factors. This blocks their sequence-specific binding to DNA and activation of target genes that are often expressed in a tissue-specific manner. Id proteins can also act as positive regulators of cell proliferation. The different mechanisms proposed for Id-mediated promotion of entry into S phase also involve HLH-mediated interactions affecting regulators of the G1/S transition. We have found that Id2 augments apoptosis in both interleukin-3 (IL-3)-dependent 32D.3 myeloid progenitors and U2OS osteosarcoma cells. We could not detect a similar activity for Id3. In contrast to the effects of Id2 on differentiation and cell proliferation, Id2-mediated apoptosis is independent of HLH-mediated dimerization. The ability of Id2 to promote cell death resides in its N-terminal region and is associated with the enhanced expression of a known component of the programmed cell death pathway, the proapoptotic gene BAX.

Animals↗

PubMed1998

GLP-1 action in L6 myotubes is via a receptor different from the pancreatic GLP-1 receptor.

The incretin hormone glucagon-like peptide-1 (GLP-1)-(7-36) amide is best known for its antidiabetogenic actions mediated via a GLP-1 receptor present on pancreatic endocrine cells. To investigate the molecular mechanisms of GLP-1 action in muscle, we used cultured L6 myotubes. In L6 myotubes, GLP-1 enhanced insulin-stimulated glycogen synthesis by 140% while stimulating CO2 production and lactate formation by 150%. In the presence of IBMX, GLP-1 diminished cAMP levels to 83% of IBMX alone. In L6 myotubes transfected with pancreatic GLP-1 receptor, GLP-1 increased cAMP levels and inhibited glycogen synthesis by 60%. An antagonist of pancreatic GLP-1 receptor, exendin-4-(9-39), inhibited GLP-1-mediated glycogen synthesis in GLP-1 receptor-transfected L6 myotubes. However, in parental L6 myotubes, exendin-4-(9-39) and GLP-1-(1-36) amide, an inactive peptide on pancreatic GLP-1 receptor, displaced 125I-labeled GLP-1 binding and stimulated glycogen synthesis by 186 and 130%, respectively. These results suggest that the insulinomimetic effects of GLP-1 in L6 cells are likely to be mediated by a receptor that is different from the GLP-1 receptor found in the pancreas.

1-Methyl-3-isobutylxanthine↗

PubMed1998

Intestinal inflammation reduces expression of DRA, a transporter responsible for congenital chloride diarrhea.

The pathogenesis of diarrhea in intestinal inflammatory states is a multifactorial process involving the effects of inflammatory mediators on epithelial transport function. The effect of colonic inflammation on the gene expression of DRA (downregulated in adenoma), a chloride-sulfate anion transporter that is mutated in patients with congenital chloridorrhea, was examined in vivo as well as in an intestinal epithelial cell line. DRA mRNA expression was diminished five- to sevenfold in the HLA-B27/beta2m transgenic rat compared with control. In situ hybridization showed that DRA, which is normally expressed in the upper crypt and surface epithelium of the colon, was dramatically reduced in the surface epithelium of the HLA-B27/beta2m transgenic rat, the interleukin-10 (IL-10) knockout mouse with spontaneous colitis, and in patients with ulcerative colitis. Immunohistochemistry demonstrated that mRNA expression of DRA reflected that of protein expression in vivo. IL-1beta reduced DRA mRNA expression in vitro by inhibiting gene transcription. The loss of transport function in the surface epithelium of the colon by attenuation of transporter gene expression, perhaps inhibited at the level of gene transcription by proinflammatory cytokines, may play a role in the pathogenesis of diarrhea in colitis.

Animals↗

PubMed1998

Attenuation of ANG II actions by adenovirus delivery of AT1 receptor antisense in neurons and SMC.

Both central and peripheral renin-angiotensin systems (RAS) are important in the development and establishment of hypertension. Thus, introducing genes relevant to RAS into neuronal and vascular smooth muscle (VSM) cells, two major targets for angiotensin (ANG) II action, is a prerequisite in considering a gene therapy approach for the control of ANG-dependent hypertension. In this study, we explored the use of adenoviral (Ad) vector to transfer AT1 receptor antisense cDNA (AT1R-AS) into neuronal and VSM cells with the anticipation of attenuation of ANG II-mediated cellular actions. Incubation of neurons and VSM cells with viral particles containing AT1R-AS (Ad-AT1R-AS) resulted in a robust expression of AT1R-AS in a majority (approximately 80%) of the cells. The expression was persistent for at least 28 days and was associated with decreases in the immunoreactive AT1 receptor protein and the maximal binding for AT1 receptor in a time- and dose-dependent manner in both cell types. ANG II stimulation of [3H]thymidine incorporation in VSM cells and norepinephrine transporter gene expression in neuronal cells were attenuated by Ad-AT1R-AS infection. Uninfected cells or cells infected with adenovirus particles containing a mutant AT1 receptor sense cDNA showed no effects on either AT1 receptor or on attenuation of ANG II's cellular affects. These observations show, for the first time, that adenovirus can be used to deliver AT1 receptor mutant sense and antisense cDNAs into two major ANG II target tissues. This consequently influences AT1 receptor-mediated cellular actions of ANG II.

1-Sarcosine-8-Isoleucine Angiotensin II↗

PubMed1998

pHi and pHo at different depths in perfused myocardium measured by confocal fluorescence microscopy.

Confocal microscopy and the H+-sensitive fluorophore carboxyseminaphthorhodafluor-1 (SNARF-1) were used to measure either intracellular pH (pHi) or extracellular pH (pHo) in isolated, arterially perfused rabbit papillary muscles. Single-excitation, dual-emission fluorescent images of the endocardial surface and underlying myocardium to a depth of 300 micron were simultaneously recorded from perfused cylindrical muscles suspended in a controlled atmosphere oriented oblique to the focal plane. Contraction was inhibited by the addition of butanedione monoxime. In separate muscles, pHo was measured during continuous perfusion of SNARF-1 free acid. pHi measurements were made after the muscle was loaded with SNARF-1/AM and the extracellular space was cleared of residual fluorophore. Initial experiments demonstrated the uniformity of ratiometric measurements as a function of pH, image depth, and fluorophore concentration, thereby establishing the potential feasibility of this method for quantitative intramural pH measurements. In subsequent experiments, the method was validated in isolated, arterially perfused rabbit papillary muscle during normal arterial perfusion and as pHi and pHo were altered by applying CO2 externally, exchanging HEPES and bicarbonate buffers, and changing pHi with NH4Cl washout. We conclude that in situ confocal fluorescent microscopy can measure pHi and pHo changes at the endocardial surface and deeper endocardial layers in arterially perfused ventricular myocardium. This method has the potential to study pHi regulation in perfused myocardium at boundaries where diffusion of gases, metabolites, and peptides are expected to modify processes that regulate pHi.

Acidosis↗

PubMed1998

MAP kinase-independent signaling in angiotensin II regulation of neuromodulation in SHR neurons.

Angiotensin II (Ang II), via its interaction with the angiotensin type 1 (AT1) receptor subtype, causes enhanced stimulation of norepinephrine (NE) neuromodulation. This involves increased transcription of NE transporter, tyrosine hydroxylase, and dopamine ss-hydroxylase genes in Wistar-Kyoto rat (WKY) brain neurons. AT1 receptor-mediated regulation of certain signaling events (such as activation of the Ras-Raf-1-mitogen activated protein (MAP) kinase signaling pathway, nuclear translocation of transcription factors such as Fos and Jun, and the interactions of these factors with AP-1 binding sites) is involved in this NE neuromodulation (Lu et al. J Cell Biol. 1996;135:1609-1617). The aim of this study was to compare the signal transduction mechanism of Ang II regulation of NE neuromodulation in WKY and spontaneously hypertensive rat (SHR) brain neurons, in view of the fact that AT1 receptor expression and Ang II stimulation of NE neuromodulation are higher in SHR neurons compared with WKY neurons. Despite this hyperactivity, Ang II stimulation of Ras, Raf-1, and MAP kinase activities was comparable between the neurons from WKY and SHR. Similarly, central injections of Ang II caused a comparable stimulation of MAP kinase in the hypothalamic and brain stem areas of adult WKY and SHR. Inhibition of MAP kinase by either an MAP kinase kinase inhibitor (PD98059) or an MAP kinase antisense oligonucleotide completely attenuated the stimulatory effects of Ang II on [3H]-NE uptake, NE transporter mRNA, and tyrosine hydroxylase mRNA levels in WKY neurons. These treatments resulted in only 43% to 50% inhibition of [3H]-NE uptake and NE transporter and tyrosine hydroxylase mRNAs in SHR neurons. Thus, Ang II stimulation of NE neuromodulation was completely blocked by MAP kinase inhibition in WKY neurons and only partially blocked in the SHR neurons. These observations suggest the presence of an additional signal transduction pathway involved in NE neuromodulation in SHR neurons that is independent of the MAP kinase pathway.

Angiotensin II↗

PubMed1998

The fibular incisure of the tibia on CT scan: a cadaver study.

Twenty cadaver lower limbs were used for CT assessment of the fibular incisure of the tibia. The length of the syndesmotic facet is shorter in the anterior (11.20 +/- 1.90 mm) than in the posterior (14.89 +/- 2.72 mm) (P < 0.001). The angle between anterior and posterior facets is 135.18 +/- 9.27 degrees. The depth of the fibular incisure of the tibia is 4.29 +/- 1.26 mm. The vertical distance of tibiofibular overlapping is 7.81 +/- 1.93 mm. The distance between anterior margin of the tibia and anterior margin of the fibula is 17.40 +/- 3.61 mm. The distance between the medial fibular border and the lateral border of the posterior tibia is 2.01 +/- 0.49 mm. The syndesmotic notch could be divided into two groups: significant concave surface and shallow concave surface. The position of the fibula in the incisural notch may depend on the depth of the fibular incisure of the tibia during traumatic forces applied on the syndesmosis. CT can display the tibial tubercles and clearly demonstrates the fibular incisure of the tibia and the interior of the tibiofibular space.

Aged↗

PubMed1998

Angiotensin II-induced nuclear targeting of the angiotensin type 1 (AT1) receptor in brain neurons.

Angiotensin II (Ang II) interaction with the neuronal AT1 receptor results in a chronic stimulation of neuromodulation that involves the expression of norepinephrine transporter (NET) and tyrosine hydroxylase (TH). In view of this unique property and the presence of putative nuclear localization signal (NLS) consensus sequence in the AT1 receptor, this study was conducted to investigate the hypothesis that Ang II would induce nuclear sequestration of this G protein-coupled receptor and that the sequestration may have implications on Ang II-induced expression of NET and TH genes. Incubation of neuronal cultures with Ang II caused a time- and dose-dependent increase in the levels of AT1 receptor immunoreactivity in the nucleus. A 6.7-fold increase was observed with 100 nM Ang II, in 15 min, that was blocked by losartan, an AT1 receptor-specific antagonist. Ang II-induced nuclear sequestration was specific for AT1 receptor, because Ang II failed to produce a similar effect on neuronal AT2 receptors. The presence of the putative NLS sequence in the cytoplasmic tail of the AT1 receptor seems to be the key in nuclear targeting because: 1) nuclear targeting was attenuated by a peptide of the AT1 receptor that contained the putative NLS sequence; and 2) Ang II failed to cause nuclear translocation of the AT2 receptor, which does not contain the putative NLS. Ang II also caused a time- and dose-dependent stimulation of P62 phosphorylation, a glycoprotein of the nuclear pore complex. A 6-fold stimulation of phosphorylation was observed with 100 nM Ang II, in 15 min, that was completely blocked by losartan and not by PD123,319, an AT2 receptor specific antagonist. Preloading of neurons with p62-pep (a peptide containing consenses of mitogen-activated protein kinase in p62) resulted in a loss of Ang II-induced p62 phosphorylation and stimulation of NET and TH messenger RNA levels. In conclusion, these data demonstrate that Ang II induces nuclear sequestration of AT1 receptor involving NLS in the AT1 receptor and p62 of the nuclear pore complex in brain neurons. A possible role of such a nuclear targeting of the AT1 receptor on chronic neuromodulatory actions of Ang II has been discussed.

Amino Acid Sequence↗

PubMed1998

[Studies on effects of yttrium chloride and praseodymium chloride on frequency of micronucleus in human blood lymphocytes].

OBJECTIVE: To explore genotoxicity of rare-earth elements, yttrium and praseodymium. METHODS: Effects of yttrium chloride and praseodymium chloride on human lymphocytes cultured in vitro were studied by micronucleus test. RESULTS: Frequency of micronucleus in human blood lymphocytes increased significantly by treatment with yttrium chloride and praseodymium chloride, and it increased with the concentration of the both agents, to a certain range. CONCLUSION: It suggests that rare-earth elements yttrium and praseodymium have certain genotoxicity.

Cells, Cultured↗

PubMed1998

[Effects of aluminum on neurobehavioral function and metabolism of monoamine neurotransmitter].

OBJECTIVE: To evaluate the effects of occupational exposure to aluminum on neurobahavioral function and metabolism of monoamine neurotransmitter. METHODS: Thirty-three workers exposed to aluminum and 40 controls were studied. Air aluminum concentrations in workplace environment were detected with an atomic absorption spectrophotometer, homovanillic acid (HVA) and vanilylmandellic acid (VMA) in urine and aluminum in serum and urine were detected with high perfolmance liquid chromatography. Neurobehavioral function was tested with Neurobehavioral Core Test Battery recommended by WHO. RESULTS: Geometric time-weighted average of aluminum in workplace environment was 0.95 mg/m3, ranging from 0.31 to 4.12 mg/m3, and urine aluminum levels in workers exposed to aluminum averaged 12.25 micrograms/L, significantly higher than that in controls (5.78 micrograms/L). There was no significant difference in serum aluminum between the exposed and controls. Both urine VMA and HVA levels were higher in the workers exposed to aluminum, and urine VMA level in the exposed was significantly higher than that in controls. There was significant difference in neurobehavioral test, including Santa Ana, digit symbol and Benton tests between the exposed and control workers. CONCLUSION: It suggests that occupational exposure to low level of aluminum can affect the neurobehavioral function and metabolism of monoamine neurotransmitter.

Adult↗

PubMed1998

Experimental model of renovascular hypertension.

OBJECTIVE: To establish a model of renovascular hypertension. METHODS: A 4/0 resorbable chromic catgut ligature was used to ligate subtotally the renal arteries of 18 dogs, forming experimental renovascular hypertension steadily. Blood pressure, plasma renin activity, the ultrastructural changes of juxtaglomerular apparatus and renal artery wall were studied after the constriction. RESULTS: It was reasonable that renal blood flow measured with an electromagnetic flowmeter was reduced by 30% after the constriction. The pathological changes of the induced renal artery stenosis were similar to those of fibromuscular dysphasia. CONCLUSION: The findings provide valuable evidence for the treatment of renovascular hypertension.

Animals↗

PubMed1998

An experimental study on rat model of parkinsonism by gene therapy.

OBJECTIVE: To induce significant improvement of motor abnormalities and striatal dopamine (DA) levels in rat model of Parkinson's disease (PD), by intracerebral grafting of the genetically modified muscle cells expressing tyrosine hydroxylase (TH). METHODS: Primary myoblasts and myotubes from the rat were prepared by cell culture and a plasmid, pCMVTH, containing TH gene and a promoter of cytomegalovirus (CMV) was constructed by DNA recombination technique. The primary muscle cells were transfected with newly constructed pCMVTH DNA vector, by using lipofection. These genetically modified muscle cells were grafted into the caudate- putamen of 6-OHDA-lesioned rats, representing PD models. Before and after grafting, the rotational behaviour and the striatal levels of DA and its metabolities were tested at different postoperative survival times. In addition, the immunocytochemistry for showing TH activity was done both in vitro and in vivo. RESULTS: The newly constrcuted plasmid, pCMVTH was proved to contain TH gene and have correct direction of insertion. The cultured primary myoblasts and myotubes lipofected with pCMVTH were immunocytochemically shown to express TH activity in vitro. After grafting, these TH-expressing muscle cells showed to have a long-term survival cells in vivo and induced a marked decrease in abnormal locomotion and a increase in striatal DA levels for PD rat model. CONCLUSIONS: In experimental gene therapy for PD, the pCMVTH is a useful vector for carrying TH gene. The lipofection is a practical technique for transferring a target gene into eukaryotes and primary cultured muscle cells should be a good vehicle for DNA transfer and intracerebral grafting.

Animals↗

PubMed1998

Mixed connective tissue disease: a disease entity?

OBJECTIVE: To explicate whether mixed connective tissue disease (MCTD) is a distinct disease and evaluate the reliability of three different diagnostic criteria proposed by Sharp, Alarcon-Segovia and Kasukawa respectively. METHODS: Clinical follow-up of 50 MCTD patients lasted 2-8 years (80% > 5 years). HLA-A, -B as well as -DR typing was performed by complemently dependent cytotocity assay. Autoantibody profile was detected by counterimmune electrophoresis (CIE). RESULTS: Thirteen (26.0%) of the 50 MCTD patients subsequently developed other connective tissue disease (OCTD), including 7 systemic lupus erythematosis (SLE), and 6 progressive systemic scleroderma (PSS). Among 23 of the MCTD patients fulfilling Sharp's criteria, 1 (4.3%) developed PSS, but among 23 of the patients fulfilling Kasukawa's, not Sharp's, 7 (30.4%) developed OCTD and among 27 of the patients fulfilling Alarcon-Segovia's, not Sharp's, 12 (44.4%) developed OCTD. In the frequencies of DR4 and DR5, there were significant differences between patients fulfilling Sharp's (60.9%, 56.5%) and controls (24.3%, P < 0.005, RR = 4.7 and 21.4%, P < 0.005, RR = 4.6%), but there were no significant differences between the patients not fulfilling Sharp's and normal control (P > 0.05). CONCLUSIONS: MCTD is a distict rheumatic disease. Sharp's criteria is the most reliable for diagnosis of MCTD.

Adolescent↗

PubMed1998

[Preliminary study on Chlamydia pneumoniae pneumonia].

In order to know the incidence of Chlamydia pneumoniae (strain TWAR) pneumonia and its clinical features, 93 patients with pneumonia and 93 matched patients with non-respiratory diseases were studied. TWAR antibodies (IgG and IgM) were detected by microimmunofluorescence (MIF) test. The results showed that 19.4% (18 cases) patients with pneumonia were TWAR pneumonia, in which 10 cases accompanied by bacteria infection and 7 cases being simple TWAR pneumonia. There were no significant differences in clinical features between TWAR pneumonia and non-TWAR pneumonia, except dry and moist rales. These data showed that the occurrence percentage of TWAR pneumonia in patients with lung cancer was higher than that in patients with the other respiratory diseases. This study suggests that there are TWAR pneumonia in China.

Adolescent↗