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Biomedical subjects

X Sun

Publications and source records attributed to X Sun.

At least 289 records · Page 16Linked to original sources
PubMed1999

[Combined window genyantrum in middle and inferior meatus under sinus endoscopy].

OBJECTIVE: For clearing away process of genyantrum and preventing its recurence. METHOD: 36 patients (40 sinuses) were treated with combined window in middle and inferior nasal meatus under sinus endoscopy. The process was cleared away completely. RESULT: There is no complication after one year following up. The cure rate is 100% and the recurrence rate is 0. CONCLUSION: It shows that the method has the advantage of clearing away the process of genyantrum and preventing recurence.

Adolescent↗
PubMed1999

[Diagnosis and prognosis evaluation of primary non-Hodgkin's lymphoma of the nose].

OBJECTIVE: To Study the diagnosis of primary nasal non-Hodgkin's Lymphoma (NHL) and to find the relationship between its classification, stage and prognosis. METHOD: The data of 10 cases with primary nasal NHL documented pathologically were analysed retrospectively. RESULT: The classification and stage were related to the prognosis significantly. Following up seven cases, 5T-ML with severe systemic symptoms died 4-6 months after diagnosis and treatment. One earlier T-ML is survival till now, and another B-ML was alive for 2.5 years. CONCLUSION: Early diagnosis of NHL of nose based on pathology is very important for treatment and prognosis. Repeat biopsies will be necessary when the diagnosis is suspected. The prognosis of late T-ML is disastrous.

Adolescent↗
PubMed1999

[Diagnosis and treatment of Killian's polyp under nasal endoscope].

OBJECTIVE: To further understand the advantage of examination and operation for killian's polyp under nasal endoscope. METHOD: 22 cases with Killian's polyps were diagnosed and treated under nasal endoscope. RESULT AND CONCLUSION: Before operation, examination under nasal endoscope may clearly find origin of the polyp and foci in maxillary sinus, which plays more important role in differential diagnosis and operation than CT or X-ray test. Operative treatment of Killian's polyp under nasal endoscope can not only eradicate foci but also reserve function of mucosa, but for severe foci in the maxillary sinus, the optimum operation should be Caldwell-Luc antrotomy.

Adolescent↗
PubMed1999

[A clinical and pathological study on cervical lymph node metastasis in the clinical N0 patient with laryngeal carcinoma].

OBJECTIVE: To study the characteristics of the cervical lymph node metastasis in negative nodes (N0) with clinically with laryngeal carcinoma patients and its implication in clinical treatment. METHODS: Forty patients with laryngeal carcinomas of No category were divided randomly into two groups: 13 radical neck dissections (RND) and 27 functional neck dissections (FND) were performed. Lymph nodes were studied histologically. RESULTS: On an average, 34.2 lymph nodes were obtained in one side of neck in RND group, and 27.4 in FND group (t = 0.86, P > 0.05). The metastases rates were 30.8% (4/13) in RND group and 33.3% (9/27) in FND group, and the total metastasis rate was 32.5% (13/40). Twelve of 13 patients (92.3%) who had positive nodes involved only the levels II and III, and 32 of 33 positive nodes (96.9%) were located in the levels II and III. The 3-year survival rates of the two groups were 69.2% (9/13) and 77.8% (21/17), respectively with no statistical difference (chi 2 = 0.3418, P > 0.5). Total 3-year survival rate was 75% (30/40). CONCLUSION: The supraomohyoid (level Io II and III) or lateral neck (level II, III and IV) dissections seem suitable for the treatment laryngeal carcinoma patients with clinically negative neck nodes.

Adult↗
PubMed1999

[Method for the determination of trace Li in serum of cancer patients by tungstate-coated graphite furnace atomic absorption spectrometry].

Using a tungstate coated graphite tube. The sensitivity of Li was significantly increased and trace Li in serum samples was determined by Zeeman graphite AAS with (NH4)2SO4 as a matrix modifier. The effects of different metal ions and biological matrix were eliminated. The characteristic concentration is 5.53 x 10(-3) microg x mL(-/1)%. The recovery is greater than 93.72%. The relative standard deviation is less than 8.93%.

Humans↗
PubMed1998

Observations of the north polar region of Mars from the Mars orbiter laser altimeter.

Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

Carbon Dioxide↗
PubMed1998

The hrp23 protein in the balbiani ring pre-mRNP particles is released just before or at the binding of the particles to the nuclear pore complex.

Balbiani ring (BR) pre-mRNP particles reside in the nuclei of salivary glands of the dipteran Chironomus tentans and carry the message for giant-sized salivary proteins. In the present study, we identify and characterize a new protein component in the BR ribonucleoprotein (RNP) particles, designated hrp23. The protein with a molecular mass of 20 kD has a single RNA-binding domain and a glycine-arginine-serine-rich auxiliary domain. As shown by immunoelectron microscopy, the hrp23 protein is added to the BR transcript concomitant with transcription, is still present in the BR particles in the nucleoplasm, but is absent from the BR particles that are bound to the nuclear pore complex or are translocating through the central channel of the complex. Thus, hrp23 is released just before or at the binding of the particles to the nuclear pore complex. It is noted that hrp23 behaves differently from two other BR RNP proteins earlier studied: hrp36 and hrp45. These proteins both reach the nuclear pore complex, and hrp36 even accompanies the RNA into the cytoplasm. It is concluded that each BR RNA-binding protein seems to have a specific flow pattern, probably related to the particular role of the protein in gene expression.

Amino Acid Sequence↗
PubMed1998

A mutated human homologue to yeast Upf1 protein has a dominant-negative effect on the decay of nonsense-containing mRNAs in mammalian cells.

All eukaryotic cells analyzed have developed mechanisms to eliminate the production of mRNAs that prematurely terminate translation. The mechanisms are thought to exist to protect cells from the deleterious effects of in-frame nonsense codons that are generated by routine inefficiencies and inaccuracies in RNA metabolism such as pre-mRNA splicing. Depending on the particular mRNA and how it is produced, nonsense codons can mediate a reduction in mRNA abundance either (i) before its release from an association with nuclei into the cytoplasm, presumably but not certainly while the mRNA is being exported to the cytoplasm and translated by cytoplasmic ribosomes, or (ii) in the cytoplasm. Here, we provide evidence for a factor that functions to eliminate the production of nonsense-containing RNAs in mammalian cells. The factor, variously referred to as Rent1 (regulator of nonsense transcripts) or HUPF1 (human Upf1 protein), was identified by isolating cDNA for a human homologue to Saccharomyces cerevisiae Upf1p, which is a group I RNA helicase that functions in the nonsense-mediated decay of mRNA in yeast. Using monkey COS cells and human HeLa cells, we demonstrate that expression of human Upf1 protein harboring an arginine-to-cysteine mutation at residue 844 within the RNA helicase domain acts in a dominant-negative fashion to abrogate the decay of nonsense-containing mRNA that takes place (i) in association with nuclei or (ii) in the cytoplasm. These findings provide evidence that nonsense-mediated mRNA decay is related mechanistically in yeast and in mammalian cells, regardless of the cellular site of decay.

Animals↗
PubMed1998

Direct association of presenilin-1 with beta-catenin.

Families bearing mutations in the presenilin-1 (PSI) gene develop Alzheimer's disease (AD). However, the mechanism through which PS1 causes AD is unclear. The co-immunoprecipitation with PS1 in transfected COS-7 cells indicates that PSI directly interacts with endogenous beta-catenin, and the interaction requires residues 322450 of PSI and 445-676 of beta-catenin. Both proteins are co-localized in the endoplasmic reticulum. Over-expression of PS1 reduces the level of cytoplasmic beta-catenin, and inhibits beta-catenin-T cell factor-regulated transcription. These results indicate that PSI plays a role as inhibitor of the beta-catenin signal, which may be connected with the AD dysfunction.

Alzheimer Disease↗
PubMed1998

Suppression of antigen-specific T cell proliferation by measles virus infection: role of a soluble factor in suppression.

Measles virus infection causes a profound immunosuppression. The basis for this immunosuppression is not known. This immunosuppression could be due to virus acting directly on lymphoid cells, the production of an immunosuppressive viral product, or a lymphoid product. We have developed an antigen-specific T cell system to study measles virus-T-cell interactions. We demonstrate that as few as five infectious viral particles added to 1000 T cells results in profound inhibition of antigen-specific T cell proliferation. Supernates taken from measles virus-infected T cells suppress the proliferation of uninfected T cells. Measles-virus-infected HeLa or Vero cells do not produce the factor. The antiproliferative effects of the supernates cannot be attributed to infectious virus, IL-10 or TGF-beta. The soluble factor appears to be larger than 100 kDa, yet retains antiproliferative activity following trypsin digestion with a size less than 10 kDa. Loss of activity is seen following heat treatment at 56 degrees C. The factor is lymphoid cell specific and exhibits cytokine-like behavior yet appears not to be a known cytokine. This soluble factor may be responsible for the overt clinical immunosuppression seen in man and a previously undescribed cytokine induced by measles virus infection of human lymphocytes.

Animals↗
PubMed1998

Structural homologies with ATP- and folate-binding enzymes in the crystal structure of folylpolyglutamate synthetase.

Folylpolyglutamate synthetase, which is responsible for the addition of a polyglutamate tail to folate and folate derivatives, is an ATP-dependent enzyme isolated from eukaryotic and bacterial sources, where it plays a key role in the retention of the intracellular folate pool. Here, we report the 2.4-A resolution crystal structure of the MgATP complex of the enzyme from Lactobacillus casei. The structural analysis reveals that folylpolyglutamate synthetase is a modular protein consisting of two domains, one with a typical mononucleotide-binding fold and the other strikingly similar to the folate-binding enzyme dihydrofolate reductase. We have located the active site of the enzyme in a large interdomain cleft adjacent to an ATP-binding P-loop motif. Opposite this site, in the C domain, a cavity likely to be the folate binding site has been identified, and inspection of this cavity and the surrounding protein structure suggests that the glutamate tail of the substrate may project into the active site. A further feature of the structure is a well defined Omega loop, which contributes both to the active site and to interdomain interactions. The determination of the structure of this enzyme represents the first step toward the elucidation of the molecular mechanism of polyglutamylation of folates and antifolates.

Adenosine Triphosphate↗
PubMed1998

alpha-Adrenergic effects on Na+-K+ pump current in guinea-pig ventricular myocytes.

1. The whole-cell patch clamp was employed to study Na+-K+ pump current (Ip) in acutely isolated myocytes. alpha-Adrenergic receptors were activated with noradrenaline (NA) after blocking beta-adrenergic receptors with propranolol. Ip was measured as the current blocked by strophanthidin (Str). 2. Activation of alpha-receptors by NA increased Ip in a concentration-dependent manner. The K0.5 depended on intracellular calcium ([Ca2+]i), however maximal stimulation did not. At 15 nM [Ca2+]i the K0.5 was 219 nM NA whereas at 1.4 microM [Ca2+]i it was 3 nM. 3. The voltage dependence of Ip was not shifted by NA at either high or low [Ca2+]i. At each voltage, maximal stimulation of Ip was 14-15 %. 4. Staurosporine (St), an inhibitor of protein kinase C (PKC), eliminated the alpha-receptor-mediated stimulation of Ip at either high or low[Ca2+]i. 5. The stimulation of Ip was independent of changes in intracellular sodium or external potassium concentrations, and did not reflect a change in affinity for Str. 6. Phenylephrine, methoxamine and metaraminol, three selective alpha1-adrenergic agonists, stimulate Ip in a similar manner to NA. Stimulation of Ip by NA was eliminated by prazosin, an alpha1-antagonist, but was unaffected by yohimbine, an alpha2-antagonist. 7. We conclude noradrenaline activates ventricular alpha1-receptors, which are specifically coupled via PKC to increase Na+-K+ pump current. The sensitivity of the coupling is [Ca2+]i dependent, however the maximal increase in pump current is [Ca2+]i and voltage independent.

Adrenergic alpha-Agonists↗
PubMed1998

Identification of a blue photoluminescent composite material from a combinatorial library

A quaternary combinatorial masking strategy was used in conjunction with photolithography to generate compositionally diverse thin-film phosphor libraries containing 1024 different compositions on substrates 2.5 centimeters square. A parallel imaging system and scanning spectrophotometer were used to identify and characterize compositions in the library with interesting luminescent behavior. Optimal compositions were identified with the use of gradient libraries, in which the stoichiometry of a material was varied continuously. This process led to the identification of an efficient blue photoluminescent composite material, Gd3Ga5O12/SiO2. Experimental evidence suggests that luminescence in this material may arise from interfacial effects between SiO2 and Gd3Ga5O12.

Journal Article↗
PubMed1998

Sunlight-induced basal cell carcinoma tumor cells and ultraviolet-B-irradiated psoriatic plaques express Fas ligand (CD95L).

The skin is constantly exposed to sunlight and frequently develops sun-induced skin cancers such as basal cell carcinoma (BCC). These epidermal-derived tumors escape local immune surveillance and infiltrate the dermis, requiring surgical removal. We report here that in contrast to keratinocytes in normal skin (n = 4), BCC tumor cells (n = 6) strongly and diffusely express Fas ligand (CD95L), but not Fas antigen (CD95). This CD95L expression in vivo by BCC tumor cells is associated with peritumoral T lymphocytes that are undergoing apoptosis. Moreover, CD95L can be induced on normal cultured keratinocytes after exposure to ultraviolet-B light (UV-B) irradiation. This induction of CD95L was confirmed at the mRNA and protein levels using multipassaged human keratinocytes and a keratinocyte cell line. Keratinocytes induced to express CD95L acquired the functional capacity to kill a CD95-positive lymphocyte cell line. Whereas hyperplastic keratinocytes in untreated psoriatic plaques do not express CD95L on their plasma membrane, after UV-B treatment there is strong and diffuse keratinocyte CD95L expression that coincided in a temporal fashion with depletion of intraepidermal T cells in all five patients studied. Our data suggest a novel molecular pathway by which UV light can contribute to the ability of a skin cancer to escape from immune attack by cytotoxic T lymphocytes, and a previously unrecognized therapeutic mechanism of action for UV-B light in psoriasis via keratinocyte CD95L expression. Such immunological events involving CD95L provide new insight and opportunity for novel treatment approaches not only for cutaneous neoplasms but also for various T cell-mediated dermatoses such as psoriasis.

Adult↗
PubMed1998

Cerebral hypoperfusion and hypometabolism with altered striatal signal intensity in chorea-acanthocytosis: a combined PET and MRI study.

We studied cerebral perfusion and oxygen metabolism in three patients with chorea-acanthocytosis using positron-emission tomography and oxygen-15 labeled O2 and CO2. High-field magnetic resonance imaging also was performed. Regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) were significantly reduced in the caudate and putamen when compared with seven control subjects. Mild but significant reductions of rCBF (lower than the normal control values -2 SD) were found in the bilateral frontal, left temporal and parietal, and bilateral thalamic areas; rCMRO2 was reduced in the bilateral frontal and left temporal areas. Magnetic resonance imaging showed increased signal intensity accompanied by scattered bright spots in the caudate head and putamen on T2-weighted images; decreased signal intensity was shown at these sites on T1-weighted images. These findings were not observed in 10 neurologically normal volunteers and are rare in the common hyperkinetic form of Huntington's disease. Reduced cerebral perfusion and oxygen metabolism seem to be related to the intellectual and personality changes that occur in chorea-acanthocytosis. Combined positron-emission tomography and magnetic resonance imaging studies may improve diagnostic accuracy in patients with chorea-acanthocytosis and related disorders.

Acanthocytes↗