Biomedical subjects

W Sun

Publications and source records attributed to W Sun.

At least 217 records · Page 12Linked to original sources

PubMed1997

[Research on types of Salmonella in some animals in Jilin province].

Some animals were examined for the presence of Salmonella in Jilin province. The rate of Salmonella detection was 537 strains from 846 snakes samples (63.5%); 136 strains from 648 frog samples (20%); 185 strains from 369 pig and chick samples (50%). All isolated Salmonella comprised of two subgenus (SII and SIIIb). Serologically, groups 04, 07, 08, 09, 01, 03, 19, 03, 10, 016, 035, 043, 048, 050, 058 and 061 were identified and the isolates were classified into 13 groups and 24 serotypes. Two of these isolates SII43:enZ15:1, 6 and SIIIb58:Z52:Z are reported for the first time in China.

Animals↗

PubMed1997

[A study on the cytotoxicity of six filling materials in vitro].

This paper deals with the cytotoxicologic analyses on 6 filling materials with morphology of cells, ultraviolet light spectrophotometry and incorporation test using mouse L-929 fibroblasts labelled 3H-TdR. The results showed that the cytotoxicity of Silver amalgam and the Gallium-Silver alloys, which were produced by mixing the conventional dental alloys powder or high copper alloys powder with Gallium, was significantly stronger than that of light curing composites and the Gallium-Silver alloys that were produced by the spherical amalgam alloys powder and Gallium. It suggested that the level of mercury and copper in the alloys can influence their cytotoxic properties.

Animals↗

PubMed1997

[The relation of the changes of SOD and PGE2 in aqueous humor with the transient rise of intraocular pressure after argon laser iridectomy].

OBJECTIVE: To study the mechanism of transient rise of the intraocular pressure (IOP) after argon laser iridectomy (ALI). METHODS: The rabbit changes of IOP, the activity of superoxide dismutase (SOD) and the concentration of prostaglandin E2 (PGE2) in aqueous 15 min, 60 min, 6 hr, 24 hr, 48 hr after ALI, the relationships of these changes with the transient rise of IOP, and the effects of using indomethacin, cortisone, vitamin E and C before ALI on the transient rise of IOP were observed. RESULTS: After ALI, the transient rise of IOP took place within postoperative 6 hr. Following the postoperative transient rise of IOP, the concentration of PGE2 in the aqueous was markedly increased, but the activity of SOD in the aqueous markedly decreased. When indomethacin, cortisone, vitamin E and C were used before ALI, the concentration of PGE2 was not markedly increased, the activity of SOD was not markedly decreased and the postoperative transient rise of IOP did not take place. CONCLUSIONS: The transient rise of IOP after ALI is related to the increase of concentration of PGE2 and the decrease of activity of SOD in the aqueous. Using indomethacin, cortisone, vitamin E and C before ALI can effectively prevent the postoperative transient rise of IOP.

Animals↗

PubMed1997

[Effects of white noise exposure on nonlinearities of outer hair cell].

The technique of microelectrode has been used to record receptor potentials of outer hair cell (OHC) of seven guinea pigs' cochlea basing on the programmable signal processing system. The nonlinearies of input-output function of the receptor potential recorded from OHC are compared before and after with noise exposure. Results indicated that the input-output functions of the receptor potential of OHC reveal linear behavior increased in linearity in low level and turned to be nonlinear when the sound level increased to 50 dB SPL, and significant saturation was seen in 80 dB SPL. After the white noise exposure (100 dB SPL , 10-20 minutes), the phenomenon of nonlinearity disappeared with the amplitude of receptor potential decreased, which suggested that nonlinearity was easy affected by noise exposure. OHC response recruitment has shown after noise exposure. These results together with preceding clinical observation of loudness recruitment, suggest that loudness recruitment occurs at least in part at the hair cell level.

Animals↗

PubMed1997

The chromosomal effect of birchen dust as determined by the micronucleus test.

In a wood processing factory, the measured air concentration of birchen dust was 1.26 +/- 0.41 mg/m3, and the micronucleus frequency of peripheral blood lymphocytes in 83 workers exposed to wood dust was 1.13 +/- 2.83/1000, which was significantly higher (P < 0.01) than that of control group (0.51 +/- 1.41/1000). The number of exposed workers with positive micronucleus test was 9.6%, which was higher than that of control group (4.5%), but the difference was not significant (P > 0.05). The micronucleus test in mice treated with water extracts of unsteamed and unbaked birchen dust showed that the micronucleus frequencies in all treated groups were significantly higher than that of control group (P < 0.01) and there was also a dose response correlation (r = 0.96, P < 0.0005). The results of steamed and baked birchen dust extracts were significantly lower than those of the unsteamed and unbaked ones at the same doses (P < 0.001). This suggests that when the birchen dust is steamed at the temperature of 100 degrees C for 24 h or baked at the temperature of 80 degrees C, its inducing effect in micronucleus test could be lowered.

Adult↗

PubMed1997

[Prognosis and prognostic factor analysis epithelial ovarian cancer].

OBJECTIVE: To investigate the prognosis change and prognostic factors of advanced epithelial ovarian cancer in recent over twenty years. METHODS: One hundred and fourty patients with advanced epithelial ovarian cancer were analyzed. They were divided into two groups based on their operation time. 56 patients operated before Jan. 1980 were included in the first group, and the other 84 patients in the second group. Kaplan-Meier survival curves of the two groups were calculated, and Cox model was used to evaluate the prognostic factors of the disease at univariate and multivariate levels using SPSS and SURVCALC software. RESULTS: There was no pathological difference in between the two groups, but the patients in the second group received more aggressive chemotherapy. The overall 1-, 2-, and 5-year survival rates were 61.2%, 32.1%, and 8.5%, respectively. In the first group they were 42.3%, 29.6% and 4.5% respectively and in the second group 69.3%, 36.2%, and 11.2% respectively. The prognosis of the patients in the second group was better than that in the first group, P < 0.05. Univariate analysis revealed that stage, grade, residual tumor size and chemotherapy were significant predictors of patients' outcome. COX regression analysis identified that they were all independent prognostic factors. The patients with advanced, low grade, residual tumor (> 2 cm) had poor prognosis. The prognosis of the patients who received equal or more than four, especially six cycles combined chemotherapy was improved. CONCLUSION: The prognosis of the patients with advanced ovarian cancer has improved in recent over 10 years, higher optimal cytoreductive rate and equal or more than six cycles combined chemotherapy are important measures for the better prognosis of advanced ovarian cancer.

Adenocarcinoma, Mucinous↗

PubMed1997

[The clinical and pathological characteristics of epithelial ovarian carcinoma in patients with age under 40].

OBJECTIVE: To investigate the clinical and pathological characteristics of epithelial ovarian carcinoma in patients with age under 40. METHODS: From Jan 1978 to Dec 1992, 54 cases with epithelial ovarian carcinoma under 40 years old were admitted to our hospital and enrolled in the study group, another 54 patients suffered from the same disease with age over 40 in the same period were served as control. Comparison analysis for clinical and pathologic data of 2 groups was performed using SPSS and SURVALC statistics software. RESULTS: Main complaint because of either pelvic mass or abdominal mass found by chance was more common in study group (46.3%) than that in control group (27.8%). whereas because of symptoms was less common in study group (53.7%) than in control group (72.2%). Other parameters such as early stage (I and II) rate (61.1%), unilateral tumor rate (68.5%), average maximum diameter of tumor (13.6 cm), highly differentiated rate (50%) and the possibility for tumor reductive surgery were higher in study group than in control group. The difference of histological pattern and chemotherapy between 2 groups was not significant. Single variate analysis showed that the prognosis was better in study group. The 2-year and 5-year survival rates were 69.8% and 50.2% respectively. No recurrence was found in the 8 patients in whom the contralateral healthy ovary remained. However multiple variate analysis indicated that age was not a prognostic factor. CONCLUSION: Epithelial ovarian carcinoma was prone to be lower degree malignancy in patients under 40 years therefore the prognosis of them was better. It might be resonable to have healthy ovary left in some select cases.

Adolescent↗

PubMed1997

[Determination of complements in serum and middle ear effusion of the patients with secretory otitis media].

Complements in serum and middle ear effusion were determined in 20 patients with secretory otitis media, and compared with those in the normal controls. The C5 and C1-INH in serum of the patients were significantly higher. On the contrary, C9 and B factor (Bf) were significantly lower, and the circulatory immunocomplex was also higher. In patients with secretory otitis media, the middle ear effusion levels of C3, C4 and C5 were significantly lower, and Bf and immunocomplex were significantly higher than those in serum. The results suggest that the ability of complements in clearing immunocomplex is low. Therefore, the immunocomplex may deposit in the mucosa of the middle ear. Thus the permeability of capillary will be increased, and the middle ear effusion occurs.

Adolescent↗

PubMed1996

Escherichia coli OxyR protein represses the unmethylated bacteriophage Mu mom operon without blocking binding of the transcriptional activator C.

Transcription of the bacteriophage Mu mom operon requires transactivation by the phage-encoded C protein. DNase I footprinting showed that in the absence of C, Escherichia coli RNA polymerase E(sigma)70 (RNAP) binds to the mom promoter (Pmom) region at a site, P2 (from -64 to -11 with respect to the transcription start site), on the top (non-transcribed) strand. This is slightly upstream from, but overlapping P1 (-49 to +16), the functional binding site for rightward transcription. Host DNA-[N6-adenine] methyltransferase (Dam) methylation of three GATCs immediately upstream of the C binding site is required to prevent binding of the E.coli OxyR protein, which represses mom transcription in dam- strains. OxyR, known to induce DNA bending, is normally in a reduced conformation in vivo, but is converted to an oxidized state under standard in vitro conditions. Using DNase I footprinting, we provide evidence supporting the proposal that the oxidized and reduced forms of OxyR interact differently with their target DNA sequences in vitro. A mutant form, OxyR-C199S, was shown to be able to repress mom expression in vivo in a dam- host. In vitro DNase I footprinting showed that OxyR-C199S protected Pmom from -104 to -46 on the top strand and produced a protection pattern characteristic of reduced wild-type OxyR. Prebinding of OxyR-C199S completely blocked RNAP binding to P2 (in the absence of C), whereas it only slightly decreased binding of C to its target site (-55 to -28, as defined by DNase I footprinting). In contrast, OxyR-C199S strongly inhibited C-activated recruitment of RNAP to P1. These results indicate that OxyR repression is mediated subsequent to binding by C. Mutations have been isolated that relieve the dependence on C activation and have the same transcription start site as the C-activated wild-type promoter. One such mutant, tin7, has a single base change at -14, which changes a T6 run to T3GT2. OxyR-C199S partially inhibited RNAP binding to the tin7 promoter in vitro, even though the OxyR and RNAP-P1 binding sites probably do not overlap, and in vivo expression of tin7 was reduced 5- to 10-fold in dam- cells. These results suggest that OxyR can repress tin7.

Bacterial Proteins↗

PubMed1996

Site-directed mutagenesis of glycine 99 to alanine in L-lactate monooxygenase from Mycobacterium smegmatis.

L-Lactate monooxygenase (LMO) from Mycobacterium smegmatis was mutated at glycine 99 to alanine, and the properties of the resulting mutant (referred to as G99A) were studied. Mutant G99A of LMO was designed to test the postulate that the smaller glycine residue in the vicinity of the alpha-carbon methyl group of lactate in wild-type LMO has less steric hindrance, leading to the retention and oxidative decarboxylation of pyruvate in the active site, a unique property of LMO in contrast to other members of the FMN-dependent oxidase/dehydrogenase family. G99A has been shown to be readily reduced by L-lactate at a rate similar to that of the wild-type enzyme. The binding of pyruvate to reduced G99A is 4-fold weaker than that to the wild-type enzyme. A dramatic change of this mutation is that G99A has a much lower oxygen reactivity than the wild-type enzyme. Pyruvate-bound reduced G99A reacts with O2 at a rate approximately 10(5)-fold slower than the wild-type enzyme, and free reduced G99A reacts with O2 at a rate approximately 100-fold slower than the wild-type enzyme. Due to the very low oxygen reactivity of the pyruvate-bound reduced enzyme, G99A has been shown to catalyze the oxidation of L-lactate to pyruvate and hydrogen peroxide instead of acetate, carbon dioxide, and water, the normal decarboxylation products of pyruvate and hydrogen peroxide. Thus, the mutation alters the enzyme from its L-lactate monooxygenase activity to L-lactate oxidase activity. However, compared with L-lactate oxidase, G99A has a much lower reactivity toward oxygen. Our results also reveal that the small steric change around N-5 of the flavin causes a profound change in the electronic distribution in the catalytic cavity of the enzyme and imply that electrostatic interactions in the active site provide an important factor for control of O2 reactivity.

Alanine↗

PubMed1996

AML-2 is a potential target for transcriptional regulation by the t(8;21) and t(12;21) fusion proteins in acute leukemia.

AML-1B is targeted directly and indirectly in multiple chromosomal translocations in myeloid and B-cells. The AML-1/ETO and TEL/AML-1 fusion proteins, created by the t(8;21) and t(12;21) respectively, disrupt AML-1B-dependent transcription. Recently, two human members of the runt homology domain family of transcription factors have been identified, AML-2 and AML-3, which also regulate transcription through enhancer core motifs. If multiple factors regulate transcription through the same site, a dominant interfering protein may be required to promote leukemogenesis, rather than the inactivation of both AML1 alleles. To determine which AML family proteins are active in hematopoietic cells, we developed antisera specific to each family member for use in gel mobility shift assays. We have found that AML-1B is the major DNA binding activity in T-cell lines, while both AML-1B and AML-2 are expressed in myeloid and B-cell lines. AML-1B represents most of the active protein in the mouse thymus, whereas AML-1 and AML-2 are equally expressed in the mouse spleen. AML-3 is expressed at very low levels in a single myeloid cell line, 32D.3, and is the only core binding activity present in Buffalo rat liver cells. We demonstrate that AML-2-dependent transactivation mediated by enhancer core motifs is inhibited by the AML-1/ETO and TEL/AML-1 fusion proteins. This indicates that the t(8;21) and t(12;21) fusion proteins inhibit transcriptional activation by the AML-1 transcription factor family, and in so doing contributes to leukemogenesis.

Acute Disease↗

PubMed1996

Localization of sympathetic and parasympathetic neurons innervating pancreas and spleen in the cat.

The localization of sympathetic and parasympathetic neurons innervating the pancreas and spleen was studied in the cat utilizing retrograde transport of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Injection of WGA-HRP into the pancreas resulted in retrograde labeling in the whole of the solar plexus, while injection of WGA-HRP into the spleen also resulted in heavy labeling in the celiac ganglia bilaterally. Only a few labeled neurons were distributed in the superior mesenteric ganglion. With respect to parasympathetic innervation, HRP-labeled pancreatic and splenic neurons were found throughout the rostrocaudal extent of the dorsal motor nucleus of the vagus nerve (DMV) bilaterally. Although pancreatic neurons in the DMV were mainly observed in limits rostral to the obex, splenic neurons were centered at the level of the obex.

Animals↗

PubMed1996

Differential expression of D-type G1 cyclins during mouse development and liver regeneration in vivo.

D-type G1 cyclins are the primary cell cycle regulators of G1/S transition in eukaryotic cells, and are differentially expressed in a variety of cell lines in vitro. Little is known, however, about the expression patterns of D-type G1 cyclins in normal mouse in vivo. Thus, in the present study, tissue-specific expressions of cyclin D1 and D3 genes were examined in several tissues derived from adult male mice, and stage-specific expression of cyclin genes was studied in brain, liver, and kidney of developing mice from embryonic day 13 to postnatal day 11. Cell cycle-dependent expression of cyclins was also examined in regenerating livers following partial hepatectomy. Our results indicate that (1) cyclins D1 and D3 are expressed in a tissue-specific manner, with cyclin D1 being highly expressed in kidney and D3 in thymus; (2) cyclin D3 mRNA is abundantly expressed in young proliferating tissues and is gradually reduced during development, whereas cyclin D1 mRNA fluctuates during development; and (3) compensatory regeneration of liver induces cyclin D1 gene expression 12 hr after partial hepatectomy, and cyclin D3 gene expression from 36 to 42 hr (at the time of G1/S transition). In conclusion, this study indicates that cyclin D1 and D3 genes are differentially expressed in vivo in a tissue-specific, developmental stage-dependent, and cell cycle-dependent manner.

Animals↗

PubMed1996

Cloning and sequence analysis of a Marek's disease virus origin binding protein (OBP) reveals strict conservation of structural motifs among OBPs of divergent alphaherpesviruses.

Marek's disease virus (MDV) is a highly cell-associated avian herpesvirus. In its natural host, MDV induces Marek's disease (MD), a lethal condition characterized by malignant lymphoma of T cells. Although symptoms of MD may be prevented by vaccination, no practical pharmacological method of control has been widely accepted. Viral replication represents a point at which pharmacological control of herpesvirus infection may be most successful. However, this requires detailed knowledge of viral replication proteins. Studies in HSV-1 DNA replication implicate the UL9 protein as a key initiator of replication. For example, binding of UL9 to HSV-1 origins is a prerequisite for assembly of additional replication proteins. In this study, a protein, whose apparent molecular size is similar to that of HSV-1 UL9, was identified in extracts of MDV infected cells by western blot analysis with anti-HSV-1 UL9 antibody. A putative MDV UL9 gene was subsequently identified through sequencing of MDV genome fragments (BamHI G and C). Extended DNA sequence analysis revealed an open reading frame (ORF) which could encode a protein homologous to HSV-1 UL9. The MDV UL9 ORF encodes 841 amino acids, producing a sequence 49% identical to HSV-1 UL9 and 46% identical to VZV gene 51 product (VZV UL9). MDV UL9 shares numerous structural motifs with HSV-1 and VZV UL9 proteins, including six conserved N-terminal helicase motifs, an N-terminal leucine zipper motif, a C-terminal pseudo-leucine zipper sequence, and a putative helix-turn-helix structure.

Alphaherpesvirinae↗

PubMed1996

A single tryptophan on M2 of glutamate receptor channels confers high permeability to divalent cations.

Ionotropic glutamate receptors (iGluRs) of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate subtype display lower permeability to Ca2+ than the N-methyl-D-aspartate (NMDA) subtype. The well-documented N/Q/R site on the M2 transmembrane segment (M2) is an important determinant of the distinct Ca2+ permeability exhibited by members of the non-NMDA receptor subfamily. This site, however, does not completely account for the different permeation properties displayed by non-NMDA and NMDA receptors, suggesting the involvement of other molecular determinants. We have identified additional molecular elements on M2 of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate receptor GluR1 that specify its permeation properties. Higher permeability to divalent over monovalent cations is conferred on GluR1 by a tryptophan at position 577, whereas blockade by external divalent cations is imparted by an asparagine at position 582. Hence, the permeation properties of ionotropic glutamate receptors appear to be primarily specified by two distinct determinants on M2, the well-known N/Q/R site and the newly identified L/W site. These findings substantiate the notion that M2 is a structural component of the pore lining.

Amino Acid Sequence↗

PubMed1996

Small-angle x-ray scattering from lipid bilayers is well described by modified Caillé theory but not by paracrystalline theory.

X-ray scattering data at high instrumental resolution are reported for multilamellar vesicles of L alpha phase lipid bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine at 50 degrees C under varying osmotic pressure. The data are fitted to two theories that account for noncrystalline disorder, paracrystalline theory (PT) and modified Caillé theory (MCT). The MCT provides good fits to the data, much better than the PT fits. The particularly important characteristic of MCT is the long power law tails in the scattering. PT fits (as well as ordinary integration with no attempt to account for the noncrystalline disorder) increasingly underestimate this scattering intensity as the order h increases, thereby underestimating the form factors used to obtain electron density profiles.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

X-ray structure determination of fully hydrated L alpha phase dipalmitoylphosphatidylcholine bilayers.

Bilayer form factors obtained from x-ray scattering data taken with high instrumental resolution are reported for multilamellar vesicles of L alpha phase lipid bilayers of dipalmitoylphosphatidylcholine at 50 degrees C under varying osmotic pressure. Artifacts in the magnitudes of the form factors due to liquid crystalline fluctuations have been eliminated by using modified Caillé theory. The Caillé fluctuation parameter eta 1 increases systematically with increasing lamellar D spacing and this explains why some higher order peaks are unobservable for the larger D spacings. The corrected form factors fall on one smooth continuous transform F(q); this shows that the bilayer does not change shape as D decreases from 67.2 A (fully hydrated) to 60.9 A. The distance between headgroup peaks is obtained from Fourier reconstruction of samples with four orders of diffraction and from electron density models that use 38 independent form factors. By combining these results with previous gel phase results, area AF per lipid molecule and other structural quantities are obtained for the fluid L alpha phase. Comparison with results that we derived from previous neutron diffraction data is excellent, and we conclude from diffraction studies that AF = 62.9 +/- 1.3 A2, which is in excellent agreement with a previous estimate from NMR data.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

Interaction of Escherichia coli primase with a phage G4ori(c)-E. coli SSB complex.

We earlier reported that Escherichia coli single-stranded DNA-binding protein (SSB) bound in a fixed position to the stem-loop structure of the origin of complementary DNA strand synthesis in phage G4 (G4ori(c)), leaving stem-loop I and the adjacent 5' CTG 3', the primer RNA initiation site, as an SSB-free region (W. Sun and G. N. Godson, J. Biol. Chem. 268:8026-8039, 1993). Using a small 278-nucleotide (nt) G4ori(c) single-stranded DNA fragment that supported primer RNA synthesis, we now demonstrate by gel shift that E. coli primase can stably interact with the SSB-G4ori(c) complex. This stable interaction requires Mg2+ for specificity. At 8 mM Mg2+, primase binds to an SSB-coated 278-nt G4ori(c) fragment but not to an SSB-coated control 285-nt LacZ ss-DNA fragment. In the absence of Mg2+, primase binds to both SSB-coated fragments and gives a gel shift. T4 gene 32 protein cannot substitute for E. coli SSB in this reaction. Stable interaction of primase with naked G4ori(c). single-stranded DNA was not observed. DNase I and micrococcal nuclease footprinting, of both 5' and 3' 32P-labeled DNA, demonstrated that primase interacts with two regions of G4ori(c): one covering stem-loop I and the 3' sequence flanking stem-loop I which contains the pRNA initiation site and another located on the 5' sequence flanking stem-loop III.

Base Sequence↗