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Biomedical subjects

Y Xu

Publications and source records attributed to Y Xu.

At least 1,009 records · Page 56Linked to original sources
PubMed1995

Transmural bioenergetic responses of normal myocardium to high workstates.

The response of myocardial high-energy and inorganic phosphates (HEP and Pi, respectively) and associated changes in myocardial blood flow, lactate uptake, and O2 consumption (MVo2) rates were examined in an open-chest canine model during progressively increasing workloads achieved by catecholamine infusion. HEP and Pi levels (measured with transmurally localized 31P-nuclear magnetic resonance spectroscopy) were unaffected by moderate increases in the level of energy expenditure but were significantly altered by high workloads, especially in the subepicardium. The MVo2 and HEP data from three different protocols that utilized pharmacological augmentation of blood flow demonstrated that the maximal rate of myocardial energy production during inotropic stimulation was dictated by perfusion limitation. This limitation was more severe in the subepicardial layer at the high workloads despite equivalent or even higher increases in blood flow to this layer, reflecting a preferential enhancement of demand in the outer layer by catecholamines. In contrast, under basal conditions, existence of a marginal perfusion limitation was evident in the inner but not in the outer layer.

Adenosine Triphosphate↗
PubMed1995

Modulation of an inhibitory interneuron in the neural circuitry for the tail withdrawal reflex of Aplysia.

1. Serotonin (5-HT), small cardioactive peptide B (SCPB) and FMRFamide have well-established facilitatory and inhibitory effects on sensory neurons and their connections with motor neurons mediating withdrawal reflexes in Aplysia. Little is known, however, about their effects on interneurons contributing to those reflexes. As a first step, we examined the effects of these three transmitters on the identified inhibitory interneuron RP14 in isolated pleural-pedal ganglia. 2. Bath application of 5-HT hyperpolarized RP14, inhibited its spontaneous activity and decreased its excitability. In addition, 5-HT decreased the amplitude of inhibitory postsynaptic potentials produced by RP14 in tail sensory and motor neurons. 3. In contrast, bath application of SCPB increased spontaneous activity in RP14. Subsequent application of 5-HT to the bath, which still contained SCPB, inhibited RP14. Therefore, the effects of SCPB were essentially opposite to those of 5-HT on this inhibitory interneuron. 4. FMRFamide had little effect on RP14. It did not produce an obvious change in its resting membrane potential and produced only a transient increase in its spontaneous activity. 5. These results suggest that various neuromodulators have differential effects on elements of the neuronal circuit underlying the tail-withdrawal reflex of Aplysia. Differential modulation may determine the overall behavioral manifestations associated with sensitization.

Action Potentials↗
PubMed1995

A new method to localize brain nuclei for surgery in extrapyramidal disease.

A CT localization method to be used with the Leksell stereotactic system was employed to locate the ventral lateral nucleus of the thalamus (VL) and globus pallidus (GP) for treating extrapyramidal disease (EPD). The study comprised 100 normal adults and 70 cases of EPD, and results in both populations were compared. The 70 cases of EPD were studied ventriculography, and 30 normal adults were studied my MRI. Results indicate the accuracy of localization of the primary targets was 94.25% with the CT localization method described herein and 88.9% in the control group. In conclusion, the new CT localization method is a valuable technique to locate brain nuclei and to replace ventriculography with stereotactic surgery in the treatment of EPD patients.

Adolescent↗
PubMed1995

DNA repair is more important than catalase for Salmonella virulence in mice.

Pathogenic microorganisms possess antioxidant defense mechanisms for protection from reactive oxygen metabolites such as hydrogen peroxide (H2O2), which are generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxify reactive oxygen species, and DNA repair systems which repair damage resulting from oxidative stress. To determine the relative importance of these two potentially protective defense mechanisms against oxidative stress encountered by Salmonella during infection of the host, a Salmonella typhimurium double mutant unable to produce either the HPI or HPII catalase was constructed, and compared with an isogenic recA mutant deficient in DNA repair. The recA mutant was hypersusceptible to H2O2 at low cell densities in vitro, while the catalase mutant was more susceptible to high H2O2 concentrations at high cell densities. The catalase mutant was found to be resistant to macrophages and retained full murine virulence, in contrast to the recA mutant which previously was shown to be macrophage-sensitive and attenuated in mice. These observations suggest that Salmonella is subjected to low concentrations of H2O2 while at relatively low cell density during infection, conditions requiring an intact DNA repair system but not functional catalase activity.

Acatalasia↗
PubMed1995

c-KIT expression enhances the leukemogenic potential of 32D cells.

The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells.

Amino Acid Sequence↗
PubMed1995

Dexamethasone regulates somatostatin receptor subtype messenger ribonucleic acid expression in rat pituitary GH4C1 cells.

Ligand binding studies have shown that glucocorticoids down-regulate somatostatin receptor (sst) concentration in several endocrine target cells and cell lines including GH4C1 cells. However, it has not been determined whether this decrease in sst number occurred via transcriptional and/or posttranscriptional events. In the present study, we have investigated the effect of dexamethasone (Dex) treatment (1 microM) of GH4C1 cells for up to 48 h on the steady state level of messenger RNA (mRNA) for sst1, sst2, and sst3, the predominant isoforms expressed in this cell line, by solution hybridization-nuclease protection analysis. Exposure of GH4C1 cells to Dex for 2 h increased sst1 mRNA levels 2.5-fold and sst2 1.5-fold compared with controls (Con). Prolonged exposure, however, resulted in a decrease in mRNA levels of sst1 to 50% and sst2 to 30% of Con by 24-48 h. In contrast, sst3 mRNA levels were unchanged at 2 h, decreased to 30% of Con by 6 h, and remained decreased for up to 24 h. Longer exposure resulted in a dramatic increase in expression, reaching 350% of Con by 48 h. The Dex effect on expression of all subtypes was dose dependent, maximal at 10 nM. Steroid hormone regulation of sst mRNA expression in GH4C1 cells proved to be complex. Exposure to Dex for 24 h, as expected, decreased expression of all subtypes. Progesterone, however, increased sst1 mRNA levels, decreased sst3 levels, but was without effect on sst2; treatment with estrogen and testosterone increased expression of all three subtypes. Nuclear run-on assays indicated that the Dex-induced changes in sst1 and sst2 mRNA levels were associated with congruent changes in the transcription rate of sst genes. Thus, glucocorticoids regulate sst expression in GH4C1 cells, at least in part, by controlling the rate of transcription of sst genes.

Animals↗
PubMed1995

Molecular characterization of a chromosome translocation breakpoint t(11;14)(p13;q11) from the cell line KOPT-K1.

Recurrent chromosome translocations involving 11p13 and 14q11 are found in 5-10% of cases of T-ALL. The gene involved in the translocation on chromosome 14 is the T cell antigen receptor alpha or delta. The putative oncogene on chromosome 11 is rhombotin 2 (RBTN2)/translocated in T cell gene 2 (ttg-2), a member of the LIM family of proteins. In this paper we characterize a cell line KOPT-K1 that has a t(11;14)(p13;q11). The breakpoint on chromosome 11 involves an Alu-rich region with the break occurring between two Alu sequences on chromosome 11. In addition, approximately 70 bases from the break on chromosome 11 is a tetranucleotide repeat. Whether either of these structures played a role in the translocation is not known. No heptamer or nonamer sequences, implicated in other rearrangements were found near the breakpoint. The breakpoint on chromosome 11 maps more centromeric than previous translocations of this region. Despite this the RBTN2 gene is highly expressed in KOPT-K1. This cell line will be useful for investigating the role of RBTN2 in leukemogenesis and the mechanism by which the translocation alters the expression of RBTN2.

Base Sequence↗
PubMed1995

[Chemical constituents of Astragalus chinensis L].

Three compounds have been isolated from the seeds of Astragalus chinensis. Their structures were identified on the basis of spectral data (UV, 13CNMR, 1HNMR, IR and MS) as octacosane, daucosterol and kaempferol.

Alkanes↗
PubMed1995

Glutathione-dependent metabolism of trichloroethylene in isolated liver and kidney cells of rats and its role in mitochondrial and cellular toxicity.

Metabolism of trichloroethylene (Tri) by the glutathione (GSH) conjugation pathway was studied in hepatocytes, renal cortical cells, and liver subcellular fractions from male Fischer 344 rats. Toxicity of Tri and some of its GSH- and cytochrome P450-dependent metabolites was then studied in isolated hepatocytes, kidney cells, and liver and kidney mitochondria to assess the relative role of these metabolites in toxicity. Tri metabolism to S-(1,2-dichlorovinyl)glutathione (DCVG), a nephrotoxic metabolite of Tri, was demonstrated in both isolated hepatocytes and kidney cells. This suggests that the first Tri bioactivation step that leads to nephrotoxicity in vivo occurs in both liver and kidney. Rates of DCVG formation in liver microsomes and cytosol were similar, although total activity was greater in cytosol. Only S-(1,2-dichlorovinyl)-L-cysteine (DCVC), but not Tri, DCVG, or the other oxidative metabolites examined (trichloroacetate, dichloroacetate, chloral hydrate, trichloroethanol, or oxalic acid) caused acute hepatotoxicity, whereas only DCVC and DCVG produced acute nephrotoxicity in isolated renal cortical cells. Tri and the metabolites examined, except trichloroacetate and DCVG, caused a loss of function of liver and kidney mitochondria. In liver mitochondria, DCVC produced the largest decrease in mitochondrial respiration, whereas Tri, trichloroethanol, and dichloroacetate were somewhat less toxic and chloral hydrate was the least toxic. In kidney mitochondria, in contrast, Tri, trichloroethanol, dichloroacetate, chloral hydrate, and DCVC caused similar decreases in mitochondrial respiration. These results suggest that, whereas both GSH conjugation and cytochrome P450-dependent metabolism of Tri generate mitochondrial toxicants, only the GSH-derived metabolites were cytotoxic.

Animals↗
PubMed1995

[Therapeutical mechanism of 3,4 dihydroxyacetophenone in treating chronic obstructive pulmonary disease].

Hemodynamic parameters were measured by ballon tipped catheter in 11 patients with COPD and plasma levels of endothelin1 (ET1), cAMP and cGMP were detected by radioimmunoassay. The results indicated that 3,4-dihydroxyacetophenone (DHAP) gives with an i.v. dose of 640mg could reduce (1) 15% of mean pulmonary arterial pressure, 39% of pulmonary vascular resistance and 21% of systemic vascular resistance; (2) but not effect on systemic arterial pressure and blood gas analysis; (3) decrease the plasma ET1 as well as cGMP level (P < 0.01, P < 0.05 respectively). The authors think that the decrease of pulmonary arterial pressure in COPD patients may be related to the lowering of plasma ET1 level and the change of the cAMP to cGMP ratio.

Acetophenones↗
PubMed1995

[Relation of bulging disc and herniated disc].

Fifteen lumbar bulging discs from 23 cadavers were examined by CT and histological technique, and 386 degenerating lesions in lumbar discs were studied if it has any relationship with degenerative diseases of intervertebral discs. Histologically, trasverse, concentric or/and radial tears were found in some anulus fibrosus of bulging discs. Clinically, the coexistence of bulging and hernia was noticed in a lesioned disc, we named it as "bulging and herniated disc", and the relation of which with bulging disc and herniated disc was discussed. This finding will change a well-known opinion that hernia would not occur in a bulging disc. Here bulging and herniated disc would reasonably be considered as one of degeneerative diseases of intervertebral discs.

Adolescent↗
PubMed1995

Long-term results after meniscectomy in 60 patients.

The long-term results of total meniscectomy in 60 patients were reviewed. The patients were followed up to 10 to 33 years. 58.3% of the patients had excellent or good results. Statistical analysis showed that the late results were related to the time of follow-up and not associated with the duration of disease before operation. Radiological degeneration of the knee was seen in 35 patients (87.5%), whereas no relationship of the degeneration to the clinical results was found. It is indicated that the menisci are so important in biomechanics that total meniscectomy should be avoided as far as possible.

Adolescent↗
PubMed1995

[A study on preparation and characteristics of monoclonal antibody against laryngeal carcinoma].

The monoclonal antibody (McAb) to laryngeal squamous carcinoma was prepared by using the technique of B lymph cell hybridomas. After screening, 4 strains of hybridomas which can secrete McAb were obtained and the McAbs in ascites were all collected. Its specificity and biological characteristics were also studied. The results showed that the McAbs can combine with the antigens of standard laryngeal cancer cell strain; the antibody titre were higher than 1: 1280; the McAbs can specifically detect the laryngeal cancer antigen in carcinoma tissues; the McAbs were of high purity and the molecular weight was 100-20kd; the cellular chromosomes of the monoclonal hybridomas were all polyploid.

Animals↗
PubMed1995

Cruciate paralysis caused by injury of the upper cervical spine.

Cruciate paralysis is an uncommon injury to the cervicomedullary junction. Five patients with injuries of the upper cervical spine and the clinical manifestation of cruciate paralysis are presented. This injury pattern is characterized by bilateral upper extremity paralysis, with minimal or no lower extremity involvement. The neuroanatomic basis and the diagnosis of this clinical entity are discussed, and the related reports in the literature are reviewed.

Adult↗
PubMed1995

[Antidepressant active constituents in the roots of Morinda officinalis How].

Five compounds having antidepressant activities have been isolated from the roots of Morinda officinalis, a Chinese traditional Yang-tonic drug. These compounds were identified as succinic acid (1), nystose (2), 1F-fructofuranosylnystose (3), inulin-type hexasaccharide (4) and heptasaccharide (5) by chemical and spectroscopic methods. All of the compounds are isolated from the species of genus Morinda for the first time.

Animals↗
PubMed1995

The effect of posterior element resection on the stress distribution in the lumbar spine.

A three-dimensional finite element model of the lumbar motion segment was used to predict the stress distribution in lumbar spine with posterior element resection. It was shown that the stress level in all parts of the lumbar spine was elevated although the stress distribution remained unchanged. The authors concluded that the posterior element resection in lumbar surgery should be avoided as much as possible.

Biomechanical Phenomena↗
PubMed1995

[Effects of m-nifedipine on dihydropyridine binding sites in the cell membranes of kidney and lung from left ventricular hypertrophied elderly rats].

Effects of m-nifedipine (m-Nif) on the affinity and density of dihydropyridine (DHP) binding sites in the cell membranes of kidney and lung were investigated using the LVH (left ventricular hypertrophy) induced by Goldblatt (2k-1c) renovascular hypertension in elderly rats. m-Nif markedly reduced blood pressure, left ventricular weight, and decreased the density (Bmax) of DHP binding sites in the cell membranes of kidney and lung from 699 +/- 112, 759 +/- 35 fmol.mg-1 protein to 482 +/- 29, 381 +/- 33 fmol.mg-1 protein. No difference was observed between groups in dissociation constant (KD) values of DHP binding sites. The results suggest that m-Nif could markedly decrease DHP binding sites in the membranes of kidney and lung from cardiac hypertrophied elderly rats.

Animals↗