Biomedical subjects

Tao Pan

Publications and source records attributed to Tao Pan.

At least 37 records · Page 2Linked to original sources

PubMed2005

An aggregation-specific enzyme-linked immunosorbent assay: detection of conformational differences between recombinant PrP protein dimers and PrP(Sc) aggregates.

The conversion of the normal cellular prion protein, PrP(C), into the protease-resistant, scrapie PrP(Sc) aggregate is the cause of prion diseases. We developed a novel enzyme-linked immunosorbent assay (ELISA) that is specific for PrP aggregate by screening 30 anti-PrP monoclonal antibodies (MAbs) for their ability to react with recombinant mouse, ovine, bovine, or human PrP dimers. One MAb that reacts with all four recombinant PrP dimers also reacts with PrP(Sc) aggregates in ME7-, 139A-, or 22L-infected mouse brains. The PrP(Sc) aggregate is proteinase K resistant, has a mass of 2,000 kDa or more, and is present at a time when no protease-resistant PrP is detectable. This simple and sensitive assay provides the basis for the development of a diagnostic test for prion diseases in other species. Finally, the principle of the aggregate-specific ELISA we have developed may be applicable to other diseases caused by abnormal protein aggregation, such as Alzheimer's disease or Parkinson's disease.

Animals↗

PubMed2005

Biochemical fingerprints of prion infection: accumulations of aberrant full-length and N-terminally truncated PrP species are common features in mouse prion disease.

Infection with any one of three strains of mouse scrapie prion (PrPSc), 139A, ME7, or 22L, results in the accumulation of two underglycosylated, full-length PrP species and an N-terminally truncated PrP species that are not detectable in uninfected animals. The levels of the N-terminally truncated PrP species vary depending on PrPSc strain. Furthermore, 22L-infected brains consistently have the highest levels of proteinase K (PK)-resistant PrP species, followed by ME7- and 139A-infected brains. The three strains of PrPSc are equally susceptible to PK and proteases papain and chymotrypsin. Their protease resistance patterns are also similar. In sucrose gradient velocity sedimentation, the aberrant PrP species partition with PrPSc aggregates, indicating that they are physically associated with PrPSc. In ME7-infected animals, one of the underglycosylated, full-length PrP species is detected much earlier than the other, before both the onset of clinical disease and the detection of PK-resistant PrP species. In contrast, the appearance of the N-terminally truncated PrP species coincides with the presence of PK-resistant species and the manifestation of clinical symptoms. Therefore, accumulation of the underglycosylated, full-length PrP species is an early biochemical fingerprint of PrPSc infection. Accumulation of the underglycosylated, full-length PrP species and the aberrant N-terminally truncated PrP species may be important in the pathogenesis of prion disease.

Animals↗

PubMed2005

[The changes of fundamental frequency and formants of vowel in cochlear implant pre-lingual children of different age].

OBJECTIVE: To observe the changes of fundamental frequency and formants of vowel in cochlear implant pre-lingual children of different age and to provide the basis and direction for post-operative rehabilitation. To find the key period of language development from the aspect of phonetics and to illustrate the necessity of early implantation. METHOD: Nineteen pre-lingual cochlear implant children age from 3-13 who use 24 M or 24 Contour implant and Esprint speech processor participate the experiment. Voice analysis software was Vs99 which was explored by Beijing yangchen electronic technology corporation. Fundamental frequency and formants were abstracted from the sustained segment of vowel[a:]. RESULT: No significant difference of fundamental frequency was found between the age 4 group and normative group. Significant difference of fundamental frequency was found between the age 10 group and normative group (P < 0.05). No significant difference of formant 1 was found between the age 4 group and normative group. Significant difference of formant 1 was found between the age 10 group and normative group (P < 0.01). Formant 2 of the age 4 group was higher than the normative group, significantly. No significant difference of formant 2 was found between the age 10 group and normative group. No significant difference of the ratio of formant 1 to 2 was found between the age 4 group and normative group. Significant difference of the ratio of formant 1 to 2 was found between the age 10 group and normative group (P < 0.01). CONCLUSION: The phonation of the children from the age 4 to age 10 was obviously affected by age. This stage was the key stage for language development.

Adolescent↗

PubMed2005

[Voice analysis in pre-lingual cochlear implant adults].

OBJECTIVE: To observe voice characteristic of pre-lingual cochlear implant adults for cochlear implantation and phoniatrics. METHODS: 3s-sustained voice of vowel [ a: ] of 28 pre-lingual cochlear implant adults, 18 pre-lingual deafness adults and 10 adults with normal hearing were analyzed. Specifically, the Voice analyses include fundamental frequency, first formant, second formant, frequency perturbation quotient (FPQ), amplitude perturbation quotient (APQ) and harmonic noise ratio (HNR). The outcomes of 3 groups were compared. RESULTS: The fundamental frequency was lower in cochlear implant group [(175.42+/-25. 31) Hz] than that in deafness group [(210.84+/-54.300) Hz] (P = 0.02). The position of formant of cochlear implant group [F2 = (1264. 64 +/- 152.19) Hz] was more access to normal than that of normal hearing group[ F2 = (1422.44 +/- 232. 37) Hz, P = 0. 02]. FPQ of cochlear implant group (2.09 +/- 1.15) was more access to normal than that of deafness group (5.32+/-4.29, P=0.006). The voice of cochlear implanted and deafness adults were much more different individually. CONCLUSIONS: In the aspect of acoustic characteristic of voice, pre-lingual cochlear implant adults could benefit cochlear implantation finitely. As speech perception of pre-lingual cochlear implant adults was far worse than that of children and post-lingual cochlear implant adults, the general outcome of pre-lingual cochlear implant adults was very limited. Cochlear implant of those candidate should be cautious.

Adolescent↗

PubMed2005

[The usage of the whole palate flap in maxillofacial surgery].

OBJECTIVE: To study the clinical effects, the merits and shortcomings of the hard palate flap in repairing postoperative defects of oral soft tissue. METHODS: The whole-palate flap pedicled with the unilateral greater palatine artery was used to repair 25 cases of oral soft tissue defects. RESULTS: Of the 25 cases, 22 flaps survived completely and 2 flaps survived partially. The postoperative appearance and functions were satisfactory. CONCLUSION: Compared with other flaps, the hard palate flap is easier to harvest and use. It has reliable blood supply and does not harm the patients' appearance and function. It is one of the most desirable methods for repairing the oral soft tissue defect.

Adult↗

PubMed2004

Efficient fluorescence labeling of a large RNA through oligonucleotide hybridization.

We present an efficient method of introducing fluorophore labels at selected locations in a large RNA. The method is based on specific and highly efficient hybridization between a fluorophore-containing DNA oligonucleotide and a modular hairpin loop replacing a functionally unimportant hairpin loop in the RNA. We demonstrate its feasibility using a 255-nucleotide RNA derived from the catalytic domain of RNase P from Bacillus subtilis. Hybridization of the DNA oligonucleotide to the modular hairpin loop minimally perturbs the structure and function of this RNA. This labeling scheme should be applicable in studies of RNA conformational dynamics by ensemble and single molecule fluorescence methods.

Bacillus subtilis↗

PubMed2004

Surface-modified poly(methyl methacrylate) capillary electrophoresis microchips for protein and peptide analysis.

Polymeric materials have emerged as appealing alternatives to conventional inorganic substrates for the fabrication of microscale analytical systems; however, native polymeric surfaces typically require covalent modification to ensure optimum biocompatibility. 2-Bromoisobutyryl bromide was immobilized on poly(methyl methacrylate) (PMMA) substrates activated using an oxygen plasma. Atom-transfer radical polymerization was then performed to graft poly(ethylene glycol) (PEG) on the PMMA surface. PMMA microcapillary electrophoresis (muCE) devices made with the covalently modified surfaces exhibited substantially reduced electroosmotic flow and nonspecific adsorption of proteins on microchannel surfaces. Experiments using fluorescein isothiocyanate-conjugated bovine serum albumin indicated that both column efficiency and migration time reproducibility were 1 order of magnitude better with derivatized compared to untreated PMMA muCE chips. Fast, reproducible, and efficient separations of proteins and peptides were demonstrated using the PEG-grafted PMMA muCE chips. All analyses were completed in less than 60 s, and separation efficiencies as high as 5.2 x10(4) plates for a 3.5-cm-long separation channel were obtained. These results demonstrate the general applicability of surface-grafted PMMA microdevices for a broad range of protein analyses.

Animals↗

PubMed2004

Additional bedtime H2-receptor antagonist for the control of nocturnal gastric acid breakthrough.

BACKGROUND: Nocturnal gastric acid breakthrough(NAB) is defined as intragastric pH<4 for more than one continuous hour overnight. Adding H2-receptor antagonists (H2RAs)at bedtime to high-dose proton pump inhibitors is likely to enhance nocturnal gastric pH control and decrease nocturnal gastric acid breakthrough. OBJECTIVES: To assess the effectiveness of additional bedtime H2-receptor antagonists in suppressing nocturnal gastric acid breakthrough and the incidence of adverse effects. SEARCH STRATEGY: We identified eligible trials by searching The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2003), MEDLINE (1966-July 2003), EMBASE (1980-July 2003) and CINAHL (1982-July 2003). We re-ran the search on CENTRAL (The Cochrane Library Issue 2, 2004), and in MEDLINE, EMBASE and CINAHL in June 2004. SELECTION CRITERIA: All randomized controlled trials evaluating H2-receptor antagonists for the control of nocturnal gastric acid breakthrough were eligible for inclusion. DATA COLLECTION AND ANALYSIS: We extracted data and recorded relevant information onto specially developed forms. One reviewer extracted data and a second reviewer checked data extraction. We have also double-checked data entry into RevMan. For binary outcomes, we expressed the impact of the intervention as relative risks, together with 95% confidence intervals. For scale-based outcomes, we used means and standard deviations to summarise the values in each group, provided the scale permitted sufficient values. We had intended to analyse such outcomes for the presence of skew, but the studies included were too limited to permit this. MAIN RESULTS: Two randomized crossover studies including 32 participants met the inclusion criteria. Because the design, dosage and duration of the treatment were different between the studies, it was not possible to conduct meta-analysis. There is no consistent conclusion between the two included studies in evaluating H2RAs for the control of NAB. REVIEWERS' CONCLUSIONS: We can conclude no implications for practice at this stage. Appropriately designed, large-scale randomized controlled trials with long-term follow-up are needed to determine the effects of additional bedtime H2RAs in suppressing nocturnal gastric acid breakthrough.

Drug Administration Schedule↗

PubMed2004

Basis for structural diversity in homologous RNAs.

Large RNA molecules, such as ribozymes, fold with well-defined tertiary structures that are important for their activity. There are many instances of ribozymes with identical function but differences in their secondary structures, suggesting alternative tertiary folds. Here, we report a crystal structure of the 161-nucleotide specificity domain of an A-type ribonuclease P that differs in secondary and tertiary structure from the specificity domain of a B-type molecule. Despite the differences, the cores of the domains have similar three-dimensional structure. Remarkably, the similar geometry of the cores is stabilized by a different set of interactions involving distinct auxiliary elements.

Base Sequence↗

PubMed2004

Minute gastric carcinoid tumor with regional lymph node metastasis: a case report and review of literature.

We have encountered an unusual case of gastric carcinoid tumor. Gastroscopic examination of this 32-year-old male patient showed a smooth protrusion at the greater curvature of the gastric body with a central depression, identified by subsequent biopsy as carcinoma. The patient had a normal serum gastrin level and was negative for anti-parietal cell antibody. Histological examination of the resected gastric tissues showed that the tumor was a carcinoid, 0.3 cm x 0.3 cm in size with only one regional lymph node metastasis. We reviewed the pathogenesis, clinical presentation, diagnosis and treatment of gastric carcinoids and raise the possibility of being a lymph vessel-related metastasis even for a minute carcinoid tumor. Sentinel lymph node biopsy is recommended for surgery of minute carcinoid tumors.

Adult↗

PubMed2004

Exploring the regulation of tRNA distribution on the genomic scale.

Though up to 20% of the total RNA in bacterial cells is tRNA, the regulation of tRNA distribution on the genomic level remains unclear. tRNA distribution is governed by four processes: transcription, processing of precursor tRNA, degradation of precursor tRNA and degradation of mature tRNA. To elucidate the relationship between these processes in the regulation of tRNA production, the relative tRNA distribution was measured using a microarray specifically designed for tRNA. We developed a procedure that selectively labels 3'-CCA-containing RNAs with the fluorophores Cy3 or Cy5. The labeled tRNAs were then hybridized to microarrays printed with complementary DNA probes. The regulation of tRNA distribution in Bacillus subtilis was explored for a wild-type strain and a mutant strain with significantly decreased levels of RNase P, the enzyme required for the 5' maturation of all tRNA. The strains were either grown under a variety of conditions at doubling times ranging from 0.1 to 2.2 doublings per hour to investigate growth-related changes in the tRNA abundance or treated with the transcriptional inhibitor rifampicin to analyze mature tRNA degradation. Our results confirm that transcription and processing contribute significantly to the distribution of the 35 tRNA species in B.subtilis, and suggest a role for the degradation of precursor tRNA. Mature tRNA degradation occurs with little specificity for individual tRNA species and on the hour time-scale, indicating that degradation of mature tRNA plays only a minor role in the regulation of tRNA distribution. Aside from transcription, the final tRNA distribution appears to be derived from a balance between processing and precursor degradation activities.

Animals↗

PubMed2004

Fabrication of calcium fluoride capillary electrophoresis microdevices for on-chip infrared detection.

In this paper, we demonstrate microfluidic capillary electrophoresis (CE) devices made in CaF2 , for optical detection in a broad spectral range. We have designed methods for micromachining and enclosing capillaries in CaF2. The utility of these microdevices has been shown through CE analysis of fluorescently labeled amino acids. We have also performed infrared spectroscopy for analyte identification in microfluidic CaF2 channels. These CaF2 microdevices open the door to microchip separations with optical detection in the ultraviolet, visible, and infrared spectral regions.

Calcium Fluoride↗

PubMed2004

Single-molecule studies highlight conformational heterogeneity in the early folding steps of a large ribozyme.

The equilibrium folding of the catalytic domain of Bacillus subtilis RNase P RNA is investigated by single-molecule fluorescence resonance energy transfer (FRET). Previous ensemble studies of this 255-nucleotide ribozyme described the equilibrium folding with two transitions, U-to-I(eq)-to-N, and focused on the I(eq)-to-N transition. The present study focuses on the U-to-I(eq) transition. Comparative ensemble measurements of the ribozyme construct labeled with fluorescein at the 5' end and Cy3 at the 3' end show that modifications required for labeling do not interfere with folding and help to define the Mg(2+) concentration range for the U-to-I(eq) transition. Histogram analysis of the Mg(2+)-dependent single-molecule FRET efficiency reveals two previously undetermined folding intermediates. The single-molecule FRET trajectories exhibit non-two-state and nonergodic behaviors at intermediate Mg(2+) concentrations on the time scale of seconds. The trajectories at intermediate Mg(2+) concentrations are classified into five classes based on three FRET levels and their dynamics of interconversion within the measured time range. This heterogeneity, together with the observation of "nonsudden jump" FRET transitions, indicates that the early folding steps of this ribozyme involve a series of intermediates with different degrees of kinetic isolation and that folding occurs under kinetic control and involves many "local" conformational switches. A free energy contour is constructed to illustrate the complex folding surface.

Circular Dichroism↗

PubMed2004

Prion protein is ubiquitinated after developing protease resistance in the brains of scrapie-infected mice.

Although the key event in the pathology of prion diseases is thought to be the conversion of cellular prion protein (PrP(C)) to the protease-resistant scrapie species termed PrP(Sc), the factors that contribute to neurodegeneration in scrapie-infected animals are poorly understood. One probable determinant could be when the accumulation of PrP(Sc) in infected brain overwhelms the ubiquitin-proteasome system and triggers the degenerative cascade. In the present study, it was found that in mouse brains infected with the ME7 scrapie strain, the level of ubiquitin protein conjugates increased significantly at approximately 144 days post-infection (pi) when clinical signs first become apparent. This elevation correlated with the detection of protease-resistant PrP(Sc) and a decline in two endopeptidase activities associated with proteasome function. However, ubiquitination of PrP was only detected at the terminal stage, 3 weeks after the development of clinical symptoms (approximately 165 days pi). These results suggest that ubiquitination of PrP is a late event phenomenon and this conjugation occurs after the formation of protease-resistant PrP(Sc). Whether this post-translational modification and the impairment of proteasome function are pivotal events in the pathogenesis of prion diseases remains to be determined.

Animals↗

PubMed2004

Lymphatic mapping and sentinel node biopsy in gastric cancer.

BACKGROUND: To determine the feasibility and significance of lymphatic mapping and sentinel lymph node biopsy (SLNB) in patients with gastric cancer. METHODS: From August 1999 to January 2002, 27 gastric cancer patients underwent lymphatic mapping and sentinel lymph node biopsy using isosulfan blue dye. RESULTS: The success rate of SLNB was 96.3% (26 of 27). Accuracy, sensitivity, and specificity were 100%. There were no false negatives. In 26 successful cases, 8 patients had positive sentinel lymph nodes and 18 had negative sentinel nodes. Of 8 patients with positive sentinel nodes, 6 had positive sentinel nodes only at N1 lymph node station, 1 only at N2 station, and 1 had positive sentinel nodes at both N1 and N2 stations. Of 18 patients with negative sentinel lymph nodes, 9 patients had sentinel nodes only at N1, 3 only at N2, 5 at both N1 and N2, and 1 at both N1 and N3. There were no cases in which sentinel lymph nodes were the only sites of metastases. CONCLUSIONS: Sentinel lymph node biopsy using isosulfan blue dye in gastric cancer is a feasible procedure with high sensitivity and accuracy. Sentinel lymph nodes demonstrate the varied lymphatic drainage. If the sentinel nodes at N2 are positive, it will guide surgeons to do a more extended lymph node dissection in early stage gastric cancer.

Adenocarcinoma↗

PubMed2004

A study of the lengthening and contractility of the surgical margins in digestive tract cancer.

BACKGROUND: The lengthening and the contractility of the digestive tract were studied. METHODS: The stretched length of specimens was measured under pull weights of 500 g and 1000 g; the contracted length was measured in natural status and in 10% formalin fixation in vitro. The lengthening or contractility rate was calculated as the length difference divided by the natural length in vivo. RESULTS: The esophagus lengthened 16.5% at 500 g and 30.5% at 1,000 g, stomach 15% and 22.6%, small intestine 66.4% and 120%, large intestine 36% and 56%. In natural status in vitro, the esophagus contracted 44.5%, stomach 13.6%, small intestine 11.4%, and large intestine 15.6%; they continued to contract 12 to 24 hours after formalin fixation. CONCLUSIONS: The lengthening and contractility of the digestive tract should be considered in evaluating the resection margin at surgery. The length of different conditions can be converted by the formula: Y = alphaX.

Adult↗

PubMed2004

Epitope scanning reveals gain and loss of strain specific antibody binding epitopes associated with the conversion of normal cellular prion to scrapie prion.

We used anti-prion (PrP) monoclonal antibodies (Mabs) in different combinations to scan changes in the availability of antibody binding epitopes--using an epitope scanning assay--in brain homogenates from normal mice, and from mice infected with either ME7 or 139 A strains of infectious scrapie prion (PrPSc). In ME7-infected brains, the epitope detected by the Mab pair 8B4/8H4 is reduced, while the epitope detected by the Mab pair 8F9/11G5 is increased. Mab 8F9/11G5 detect a conformational epitope on PrPSc because the rise in Mab 8F9/11G5 binding is sensitive to a denaturing agent but resistant to proteinase K (PK). While the increase in Mab 8F9/11G5 binding correlates with the presence of PK-resistant PrP and clinical signs of infection, the reduction in Mab 8B4/8H4 binding is detected earlier. Fractionation of the ME7-infected brain homogenate in sucrose gradient revealed that the PrPSc species detected by the epitope scanning assay are heterogeneous in size, with a molecular mass of approximately > or = 2000-kDa. We also investigated whether these findings were applicable to two other strains of PrPSc, namely 87 V and 22 L. We found that the decrease in Mab 8B4/8H4 binding detected in ME7-infected brains was also detected in 87 V-infected brains but not in 22 L-infected brains. In contrast, the increase in Mab 8F9/11G5 binding detected in ME7- and 139 A-infected brains was also detected in 22 L-infected brains but not in 87 V-infected brains. Therefore, each prion strain has its unique conformation, and we can monitor the conversion of normal cellular prion (PrPC) to PrPSc based on the changes in the antibody binding patterns. The epitope can be decreased or increased, linear or conformational, detected late or early during infection, in a strain specific manner.

Alanine↗

PubMed2004

Interaction of the Bacillus subtilis RNase P with the 30S ribosomal subunit.

Ribonuclease P (RNase P) is a ribozyme required for the 5' maturation of all tRNA. RNase P and the ribosome are the only known ribozymes conserved in all organisms. We set out to determine whether this ribonucleoprotein enzyme interacts with other cellular components, which may imply other functions for this conserved ribozyme. Incubation of the Bacillus subtilis RNase P holoenzyme with fractionated B. subtilis cellular extracts and purified ribosomal subunits results in the formation of a gel-shifted complex with the 30S ribosomal subunit at a binding affinity of approximately 40 nM in 0.1 M NH(4)Cl and 10 mM MgCl(2). The complex does not form with the RNase P RNA alone and is disrupted by a mRNA mimic polyuridine, but is stable in the presence of high concentrations of mature tRNA. Endogenous RNase P can also be detected in the 30S ribosomal fraction. Cleavage of a pre-tRNA substrate by the RNase P holoenzyme remains the same in the presence of the 30S ribosome, but the cleavage of an artificial non-tRNA substrate is inhibited eightfold. Hydroxyl radical protection and chemical modification identify several protected residues located in a highly conserved region in the RNase P RNA. A single mutation within this region significantly reduces binding, providing strong support on the specificity of the RNase P-30S ribosome complex. Our results also suggest that the dimeric form of the RNase P is primarily involved in 30S ribosome binding. We discuss several models on a potential function of the RNase P-30S ribosome complex.

Bacillus subtilis↗