Biomedical subjects

X Pan

Publications and source records attributed to X Pan.

At least 37 records · Page 2Linked to original sources

PubMed2001

[The Immunophenotypical features of t (8; 21) (q22; q22) acute myeloid leukemia].

OBJECTIVE: To study the predictive value of immunophenotypical features in t (8; 21) (q22; q22) acute myeloid leukemia (AML). METHODS: Morphological/cytochemical, flow cytometric immunophenotyping, cytogenetic analyses (MIC) and RT-PCR were performed in 294 previously untreated AML. RESULTS: (1) In 294 AML patients, t (8; 21) AML were 21.8% (64); in AML-M(2), t (8; 21) AML were 54.7%; and in t (8; 21) AML, AML-M(2) were 81.3%. (2) Compared with control group, CD(19) and CD(34) expressions were higher, and CD(33) expression was lower (P < 0.001) in t (8; 21) AML. (3) If the cut-off value of CD(19) positive was >or= 20%, CD(19) positive rate was 13.6% (40/294) in AML, and 50% (32/64) and 3.5% (8/230) (P < 0.001) in t (8; 21) AML and control group. (4) CD(19)(+) and/or CD(34)(+) t (8; 21) AML accounted for 90.6% (58/64) of t (8; 21) AML and CD(19)(-)/CD(34)(-) for 9.6% (6/64). CONCLUSION: In t (8; 21) AML, especially M(2)/t (8; 21), CD(19) and CD(34) expressions were high. CD(19) was one of predictive markers of t (8; 21) AML.

Adolescent↗

PubMed2001

[Detection of TT virus DNA and sequence analysis of TTV gene in sera from young children in Nanjing].

OBJECTIVE: To investigate the prevalence of TTV genomes in young children from Nanjing and establish the PCR method for detecting TTV DNA. METHODS: A hemi-nested polymerase chain reaction (PCR) assay was established to detect TTV DNA in 110 young children and two PCR-amplified products were sequenced and the data were analyzed with the computer programs. RESULTS: TTV DNA was detected in 14 out of 110 children, and 222 bp sequences of 2 isolates from the children were analyzed. Compared with representative of published isolates, they have the nucleotide identity of 93.7%-98.6% with TX011. CONCLUSIONS: The infection rate of TTV in children is 12.73%, and 2 isolates from children belong to subgroup G1b. Our results indicates that TTV could be transmitted via other pathway besides hematogenous one, and TTV could be carried by healthy population.

Base Sequence↗

PubMed2001

[Clinical application of Targis veneers].

OBJECTIVE: The aim of this study was to evaluate the Targis material in the form of veneers. METHODS: Nineteen patients treated with 91 Targis veneers were involved in this study, and the clinical evaluation on veneers was conducted at the time of recall. The evaluation parameters included marginal adaptation, marginal discoloration, surface texture and color match. The periodontal status of all teeth with veneers was evaluated by gingival bleeding index and plaque index before and after the treatment. RESULTS: The mean observation period for the veneers was 14.6 months. Four veneers failed due to fracture, three because of debond, one because of discoloration. The cumulative rate of success was 91.2%. There was no significant difference in gingival bleeding index before and after treatment, but the plaque index significantly decreased after the treatment. CONCLUSION: The clinical results of Targis are satisfactory.

Adult↗

PubMed2001

[Clinical studies on sternocleidomastoid myoperiosteal flap for cervical tracheal reconstruction].

OBJECTIVE: To introduce the experience of repairing the defect of cervical trachea wall by using the sternocleidomastoid myoperiosteal flap after the anterior or posterior wall of cervical trachea was invaded by cervical neoplasm. METHOD: Between 1989 to 1998 the sternocleidomastoid myoperiosteal flap was applied in 12 patients with different diseases, among which 3 cases were thyroid carcinoma 5 cases were laryngeal carcinoma, 4 cases were cervical esophageal carcinoma. RESULT: The operation was successful. 12 patients were decannuated and had normal exercise tolerance. The time from reconstruction to decannulation was ranging from 20 days to 6 months. CONCLUSION: The sternocleidomastoid myoperiosteal flap is an ideal transplant for cervical tracheal reconstruction.

Adolescent↗

PubMed2001

[Measurement of microvessel density in laryngeal carcinoma and its clinical significance].

OBJECTIVE: To determine the microvessel density (MVD) in laryngeal carcinoma and its clinical significance. METHOD: Thirty-eight tumor specimens were selected from laryngeal cancer patients from January, 1994 to March, 1996. Histological sections of the tumors were stained immunohistochemically for factor VIII. Using light microscopy, we counted microvessels per 400 x field in the most active areas of tumor angiogenesis. RESULT: 1. The tumor blood vessels, composed of only one layer of endothelium were mainly distributed heterogeneously in the interstitial tissue of laryngeal carcinoma with irregular lumen, poorly developed structure. 2. The MVD in the cancer tissues were statistically higher than that in peritumoral tissues (P < 0.01). 3. The MVD in the cancer tissues in group of patients with metastasis to cervical lymphonodes were statistically higher than in group without metastasis (P < 0.01), the MVD in the cancer tissues in group of advanced cases (III, IV stages) were statistically higher than that in group of early cases (I, II stages, P < 0.01). 4. There was no statistically difference in MVD in the cancer tissue between supraglottic and glottic laryngeal carcinoma patients (P > 0.05). 5. There was no statistically difference in MVD in the cancer tissue among the G1, G2 and G3 group (P > 0.05). CONCLUSION: The laryngeal cancer blood vessels have some characteristics that don't appear in normal vessels. It is suggested that tumor angiogenesis can promote tumor growth and metastasis and MVD may be a new prognostic indicator of laryngeal carcinoma.

Adult↗

PubMed2001

[Surgical management of subglottic carcinoma].

OBJECTIVE: To explore the surgical management and evaluate the effect on patients with subglottic cancer. METHODS: Fourteen cases with subglottic carcinoma were treated surgically from 1989 to 1998. There were T1-2N0 lesions in 5 cases, T3N0-2 lesions in 3 cases and T4N0-1 lesions in 6 cases. Eleven cases underwent partial laryngectomy and three cases underwent total laryngectomy. The defects of larynx were reconstructed by using uni-pedicled or bi-pedicled stemohyoid myofascial flap, platysma myocutaneous flap, sternocleidomastoid myoperiosteal flap, thyroid perichondral flap and epiglottis flap accordingly. Unilateral neck dissection was performed on 4 cases and bilateral on one. RESULTS: The function of phonation had been restored in all cases except in 3 patients who underwent total laryngectomy. Seven out eleven(63.6%) were decannulated. The swallowing function was restored in all patients. In all cases the 3 and 5 year survival rates were 78.6%(11/14) and 63.6% (7/11), respectively. CONCLUSIONS: The conservative surgery can be used for the majority of the subglottic carcinoma if the lesions were entirely resected. The proficiency in surgical methods is crucial for the preservation of laryngeal function.

Adult↗

PubMed2001

[Preservative surgery of medial wall pyriform sinus cancer].

OBJECTIVE: To study the surgical methods and functional outcome of preservative surgery for medial wall pyriform sinus cancer. METHODS: Seventy-one patients with medial wall pyriform sinus cancer, who were treated surgically between 1985 and 1997, were reviewed. Of the 71 cases, 49 underwent preservative surgery, and 22 total laryngectomy. Preservative surgical procedure was defined as follows: 1. Extent of resection: Supraglottic horizontal partial laryngectomy and resection of medial wall of pyriform sinus were performed in patients without fixation of the true vocal cord, and the section extended to paraglottic space, partial lateral wall of pyriform sinus, preepigottic space, superior-posterior of thyroid cartilage in those with restrained vocal cord motility. Supracricoid hemilaryngopharyngectomy and resection of medical wall and partial lateral wall of pyriform sinus were practiced in those with fixed hemilarynx. Cricoid ring and cervical esophagus were removed partially if the pyriform sinus apex was involved. 2. Reconstruction: Larynx: the remains of epiglottis, perichondrium of thyroid cartilage, the infrahyoid muscular fascia, and the platysmal flap were utilized to restore the defects of larynx. Pyriform sinus: Suturing the remaining pharyngeal mucosa directly to cover the wound if the defect was relatively small. For the large defect produced by extended resections, the pectoralis major myocutaneous flap and deltopectoral flap were used. 3. Surgical treatment of cervical lymphaden: Sixty five out of the 71 cases (91.5%) underwent neck dissection. Of which ipsilateral neck dissection were done in 39 cases, and bilateral neck dissection in 26 cases. 4. All patients received postoperative radiotherapy with doses of 60-75 Gy. RESULTS: In the group of preservative surgery the 3- and 5-year survival rates were 63.4% and 49.6% respectively, whereas those in the total laryngectomy group were 52.4% and 42.4% respectively. Of the 49 cases with preservative surgery, 71.4% (35/49) had all laryngeal functions restored and 28.6% (14/49) partially restored. CONCLUSION: Despite the fact that the medial wall pyriform sinus cancer tends to have laryngeal invasion, preservative surgery can be practiced for the majority of the cases with the lesions entirely removed.

Adult↗

PubMed2000

The roles of mutS, sbcCD and recA in the propagation of TGG repeats in Escherichia coli.

A 24 triplet TGG.CCA repeat array shows length- and orientation-dependent propagation when present in the plasmid pUC18. When TGG(24) is present as template for leading-strand synthesis, plasmid recovery is normal in all strains tested. However, when it acts as template for lagging-strand synthesis, plasmid propagation is seriously compromised. Plasmids carrying deletions in the 5' side of this sequence can be isolated and products carrying 15 TGG triplets do not significantly interfere with plasmid propagation. Mutations in sbcCD, mutS and recA significantly improve the recovery of plasmids with TGG(24) on the lagging-strand template. These findings suggest that TGG(24) can fold into a structure that can interfere with DNA replication in vivo but that TGG(15) cannot. Furthermore, since the presence of the MutS and SbcCD proteins are required for propagation interference, it is likely that stabilisation of mismatched base pairs and secondary structure cleavage are implicated. In contrast, there is no correlation of triplet repeat expansion and deletion instability with predicted DNA folding. These results argue for a dissociation of the factors affecting DNA fragility from those affecting trinucleotide repeat expansion-contraction instability.

Adenosine Triphosphatases↗

PubMed2000

Interaction of H2 with Si(001)-(2 x 1): solution of the barrier puzzle.

The sticking probability of H2 on Si(001) is immeasurably small at room temperature, indicating the presence of a large energy barrier to adsorption. Surprisingly, the final state energy distributions of H2 molecules desorbing from Si(001) show no signs of having traversed such a barrier, in apparent contradiction with microscopic reversibility. Here we report experimental and theoretical evidence resolving this long-standing puzzle. Adsorption and desorption proceeding along two distinct, microscopically reversible pathways can explain all observations.

Journal Article↗

PubMed2000

Microwave-assisted extraction of glycyrrhizic acid from licorice root.

In the present study, a microwave-assisted extraction (MAE) technique has been developed for the extraction of glycyrrhizic acid (GA) from licorice root. Various experimental conditions, such as extraction time, different ethanol and ammonia concentration, liquid/solid ratios, pre-leaching time before MAE and material size for the MAE procedure were investigated to optimize the efficiency of the extraction. Under appropriate MAE conditions, such as extraction times of 4-5min, ethanol concentrations of 50-60% (v/v), ammonia concentrations of 1-2% (v/v) and liquid/solid ratios of 10:1(ml/g), the recovery of GA from licorice root with MAE was equivalent with conventional extraction methods. Those methods include extraction at room temperature (ERT), the traditional Soxhlet extraction, heat reflux extraction and ultrasonic extraction. Due to the considerable savings in time and solvent, MAE was more effective than the conventional methods. This novel method is suitable for fast extraction of GA from licorice root.

Journal Article↗

PubMed2000

Pleiotropic resistance to diverse antimalarials in actinomycin D-resistant Plasmodium falciparum.

The development and spread of multidrug-resistant Plasmodium falciparum are major health concerns. The molecular mechanisms of multidrug resistance, including resistance to many quinoline-based antimalarials, are largely unknown. In this study, we report on the isolation and partial characterization of actinomycin D (actD)-resistant P. falciparum (3D7(R)/actD2.3) from a chloroquine-susceptible strain, 3D7. The stepwise selection of an actD-resistant clone (3D7(R)/actD2.3) led to the isolation and cloning of P. falciparum that grew in the presence of 2 ng/mL of actD. The parental isolate (3D7) did not grow in the presence of a 10-fold lower drug concentration (0.2 ng/mL). The latter estimate of parasite growth was determined by direct counting of parasites in infected red blood cells. Estimates of drug resistance levels to actD, using a [(3)H]hypoxanthine uptake and incorporation method, showed a 3-fold difference in the IC(50) between 3D7 and 3D7(R)/actD2.3. Interestingly, 3D7(R)/actD2.3 P. falciparum parasites were less sensitive to several antimalarials (chloroquine, mefloquine, quinidine, and artemisinin) and to the mitochondrial specific dye Rhodamine 123. Drug transport studies using [(3)H]actD showed that 3D7(R)/actD2.3 accumulated less drug than 3D7. Moreover, the accumulation of [(3)H]actD was energy dependent. To determine if Pfmdr1 expression, previously implicated in drug resistance to certain antimalarials, mediated the resistance phenotype of 3D7(R)/actD2.3, Pfmdr1 levels in 3D7 and 3D7(R)/actD2.3 were compared by Southern and northern blot analyses. Our results revealed no differences in Pfmdr1 copy number or mRNA levels between 3D7 and 3D7(R)/actD2.3. Furthermore, comparison of Pfmdr1 sequences between 3D7 and 3D7(R)/actD2.3 showed no differences. In addition, verapamil, which reverses P-glycoprotein-mediated drug resistance in mammalian cells, did not reverse the resistance of 3D7(R)/actD2.3 to actD or chloroquine. Taken together, the findings of this study demonstrated that in vitro selection of P. falciparum for resistance to actD leads to decreased sensitivity to diverse drugs and that this pleiotropic drug resistance is associated with reduced drug accumulation not mediated by Pfmdr1.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

NMR structure of activated CheY.

The CheY protein is the response regulator in bacterial chemotaxis. Phosphorylation of a conserved aspartyl residue induces structural changes that convert the protein from an inactive to an active state. The short half-life of the aspartyl-phosphate has precluded detailed structural analysis of the active protein. Persistent activation of Escherichia coli CheY was achieved by complexation with beryllofluoride (BeF(3)(-)) and the structure determined by NMR spectroscopy to a backbone r.m.s.d. of 0.58(+/-0.08) A. Formation of a hydrogen bond between the Thr87 OH group and an active site acceptor, presumably Asp57.BeF(3)(-), stabilizes a coupled rearrangement of highly conserved residues, Thr87 and Tyr106, along with displacement of beta4 and H4, to yield the active state. The coupled rearrangement may be a more general mechanism for activation of receiver domains.

Amino Acid Sequence↗

PubMed2000

Inhibition of xanthine oxidase by liquiritigenin and isoliquiritigenin isolated from Sinofranchetia chinensis.

The methanol extract of the stem of Sinofranchetia inhibited the activity of xanthine oxidase in vitro. Bioassay-guided purification led to the isolation ofliquiritigenin and isoliquiritigenin as the main xanthine oxidase inhibitors. This inhibition of enzyme activity was found to be dose dependent, with an IC50 value of approximately 49.3 microM for liquiritigenin and 55.8 microM for isoliquiritigenin. Lineweaver-Burk transformation of the inhibition data indicated that the inhibition was of a mixed type for both liquiritigenin and isoliquiritigenin. For liquiritigenin, the Ki and K(I) were determined to be 14.0 microM and 151.6 microM, respectively. For isoliquiritigenin, the Ki and K(I) were determined to be 17.4 microM and 81.9 microM, respectively. These results suggest that these natural products could be used to treat conditions where the inhibition of xanthine oxidase is warranted.

Animals↗

PubMed2000

Refractive Error Study in Children: results from Shunyi District, China.

PURPOSE: To assess the prevalence of refractive errors and vision impairment in school-age children in Shunyi District, northeast of Beijing, the Peoples Republic of China. METHODS: Random selection of village-based clusters was used to identify a sample of children 5 to 15 years of age. Resident registration books were used to enumerate eligible children in the selected villages and identify their current school. Ophthalmic examinations were conducted in 132 schools on children from 29 clusters during May 1988 to July 1998, including visual acuity measurements, cycloplegic retinoscopy, cycloplegic autorefraction, ocular motility evaluation, and examination of the external eye, anterior segment, media, and fundus. Independent replicate measurements of all children with reduced vision and a sample of those with normal vision were done for quality assurance monitoring in three schools. RESULTS: A total of 6,134 children from 4,338 households were enumerated, and 5,884 children (95.9%) were examined. The prevalence of uncorrected, presenting, and best visual acuity 0.5 (20/40) or worse in at least one eye was 12.8%, 10.9%, and 1.8%, respectively; 0.4% had best visual acuity 0.5 or worse in both eyes. Refractive error was the cause in 89.5% of the 1,236 eyes with reduced vision, amblyopia in 5%, other causes in 1.5%, with unexplained causes in the remaining 4%. Myopia -0.5 diopter or less in either eye was essentially absent in 5-year-old children, but increased to 36.7% in males and 55.0% in females by age 15. Over this same age range, hyperopia 2 diopters or greater decreased from 8.8% in males and 19.6% in females to less than 2% in both. Females had a significantly higher risk of both myopia and hyperopia. CONCLUSIONS: Reduced vision because of myopia is an important public health problem in school-age children in Shunyi District. More than 9% of children could benefit from prescription glasses. Further studies are needed to determine whether the upward trend in the prevalence of myopia continues far beyond age 15 and whether the development of myopia is changing for more recent birth cohorts.

Adolescent↗

PubMed2000

Signal transduction cascades regulating pseudohyphal differentiation of Saccharomyces cerevisiae.

In response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous pseudohyphal growth. At least two signaling pathways regulate filamentation. One involves components of the MAP kinase cascade that also regulates mating of haploid cells. The second involves a nutrient-sensing G-protein-coupled receptor that signals via an unusual G(alpha) protein, cAMP and protein kinase A. Recent studies reveal crosstalk between these pathways during pseudohyphal growth. Related MAP kinase and cAMP pathways regulate filamentation and virulence of human and plant fungal pathogens, and represent novel targets for antifungal drug design.

Cyclic AMP-Dependent Protein Kinases↗

PubMed2000

Members of the Sp transcription factor family regulate rat calmodulin gene expression.

We have previously demonstrated that insulin positively regulates transcription of the rat calmodulin (CaM) I gene and that both basal and insulin stimulation of this gene are critically dependent on Sp1. Furthermore, a 392 bp CaM promoter was stimulated by insulin equal to the full promoter but lost activity with deletion of any of the three Sp1 sites (Solomon SS, Palazzolo MR, Takahashi T, Raghow R. Endocrinology 1997;138:5052-5054). Herein we document that Sp1 preferentially binds to the upstream sites Sp1(2) and Sp1(3) but not Sp1(1). Furthermore, gel-mobility super-shift assays demonstrate that both Sp1 and Sp3 protein are found in these complexes. When pPac-Spl, pPac-Sp3, pPac-USp3, and pPac-Sp4 were cotransfected with rCaM 1-392 promoter into Drosophila SL2 cells and challenged with 10,000 microU/mL insulin, we discovered that (1) Sp1 enhanced both basal and insulin-stimulated CaM I gene expression; (2) USp3, a "long" form of the Sp3 molecule, had a stimulatory effect on CaM I gene expression; (3) Sp1 or USp3 is involved in mediating insulin-stimulation of the CaM I gene in SL2 cells; and (4) Sp3, a "short" form of the Sp3 molecule, and Sp4 inhibited Spl-stimulated and insulin-stimulated Sp1-mediated CaM I gene expression. Together these data corroborate and extend our previous observations on Sp1 and elucidate that other members of the Sp family of transcription factors may also be involved in regulating the activity of the CaM promoter.

Animals↗

PubMed2000

Non-iterative methods incorporating a priori source distribution and data information for suppression of image noise and artefacts in 3D SPECT.

Non-iterative methods have been developed for image reconstruction in 3D SPECT with uniform attenuation and distance-dependent spatial resolution. It was observed that these methods can, in general, be susceptible to data noise and other errors, yielding conspicuous image artefacts. In this work, we developed and evaluated a regularized inverse-filtering approach for effective suppression of noise and artefacts in 3D SPECT images without significantly compromising image resolution. The proposed approach allows the incorporation of a priori random image field and data information and can thus robustly control the degree of suppression of noise and artefacts in 3D SPECT images. Using computer simulations, we evaluated and compared quantitatively images reconstructed from data sets of various noise levels by the use of the proposed methods and the existing non-iterative methods. These numerical results clearly demonstrated that the proposed regularized inverse-filtering approach can effectively suppress image noise and artefacts that plague the existing non-iterative methods, thus yielding quantitatively more accurate 3D SPECT images. The proposed regularized inverse-filtering approach can also be generalized to other imaging modalities.

Algorithms↗

PubMed2000

Nucleus-vacuole junctions in Saccharomyces cerevisiae are formed through the direct interaction of Vac8p with Nvj1p.

Vac8p is a vacuolar membrane protein that is required for efficient vacuole inheritance and fusion, cytosol-to-vacuole targeting, and sporulation. By analogy to other armadillo domain proteins, including beta-catenin and importin alpha, we hypothesize that Vac8p docks various factors at the vacuole membrane. Two-hybrid and copurfication assays demonstrated that Vac8p does form complexes with multiple binding partners, including Apg13p, Vab2p, and Nvj1p. Here we describe the surprising role of Vac8p-Nvj1p complexes in the formation of nucleus-vacuole (NV) junctions. Nvj1p is an integral membrane protein of the nuclear envelope and interacts with Vac8p in the cytosol through its C-terminal 40-60 amino acids (aa). Nvj1p green fluorescent protein (GFP) concentrated in small patches or rafts at sites of close contact between the nucleus and one or more vacuoles. Previously, we showed that Vac8p-GFP concentrated in intervacuole rafts, where is it likely to facilitate vacuole-vacuole fusion, and in "orphan" rafts at the edges of vacuole clusters. Orphan rafts of Vac8p red-sifted GFP (YFP) colocalize at sites of NV junctions with Nvj1p blue-sifted GFP (CFP). GFP-tagged nuclear pore complexes (NPCs) were excluded from NV junctions. In vac8-Delta cells, Nvj1p-GFP generally failed to concentrate into rafts and, instead, encircled the nucleus. NV junctions were absent in both nvj1-Delta and vac8-Delta cells. Overexpression of Nvj1p caused the profound proliferation of NV junctions. We conclude that Vac8p and Nvj1p are necessary components of a novel interorganelle junction apparatus.

Cell Fractionation↗