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Biomedical subjects

P Pan

Publications and source records attributed to P Pan.

At least 19 recordsLinked to original sources
PubMed2001

Dissociation reactions of gaseous ferro-, ferri-, and apo-cytochrome c ions.

Electrochemical reduction of the iron bound in the heme group of cytochrome c is shown to occur in the nano-electrospray capillary if the protein is sprayed from neutral water using a steel wire as the electrical contact. Quadrupole ion trap collisional activation is used to study the dissociation reactions of cytochrome c as a function of the oxidation state of the iron. Oxidized (Fe(III)) cytochrome c dissociates via sequence-specific amide bond cleavage, while the reduced (Fe(II)) form of the protein dissociates almost exclusively by loss of protonated heme. Apo-cytochrome c, from which the heme has been removed either via gas-phase dissociation of the reduced holo-protein or via solution chemistry, dissociates via amide bond cleavage in similar fashion to the oxidized holo-protein.

Apoproteins↗
PubMed2001

Care of patients with chronic mental illness: comparison of home and half-way house care.

Community-based services are being developed as mental health services. The purpose of this study was to examine the effect between home care and half-way house services on patients with schizophrenia. The design was quasi-experimental and used repeated measurements. There were 60 subjects, 37 receiving home care and 23 receiving half-way house care which were affiliated with one general hospital in the south of Taiwan. Of the 60 chronic schizophrenic patients, there were 34 males and 26 females with an average age of 34 years. The Quality of Life Scale was applied to measure each patient four times, at an interval of two months. These follow-up data were analyzed by Generalized Estimating Equation-I (GEE-I) because repeated observations on an individual may be correlated. The result showed that the total QOL in patients receiving home care programs was significantly higher than those receiving half-way house service. The total scores of QOL in patients under half-way house and home care services did not show secular change. The patients under home care program showed a somewhat improvement for a short period of time. However, as time went on, the patients showed no obvious improvement in their life quality. The dimensions of independence and social activity in QOL also showed significantly different between these two groups. The results may provide guides on designing programs and activities for the chronic mental patients. However, the best decision to apply which program for patients need continouous and comprehensive assessment.

Adolescent↗
PubMed2001

[The influential factors on DNA cycle sequencing and data evaluation of practical example].

OBJECTIVE: To study some factors that may influence DNA sequencing by analyzing 2040 sequencing samples retrospectively. METHODS: The effects of DNA templates, primers, cycle sequencing reactions as well as purification methods were comparatively analyzed. RESULTS: 70 percent of sequencing failure is caused by DNA template. Characteristics of data from poor template preparation include top-heavy with a short read length, acceptable signal with some noise peaks (Ns), weak signal, overall noise and flat lines or no signal. The ineffective primers can cause 15.4 percent sequencing failure. Possible explanations include primer mismatches and low Tm value. CONCLUSIONS: The quality of template DNA can have a major impact on the quality of the DNA sequencing. Purification of the extension products is absolutely necessary in DNA sequencing, and isopropanol precipitation is highly recommended for this procedure.

Animals↗
PubMed2000

Determination of the in situ bactericidal activity of an essential oil mouthrinse using a vital stain method.

BACKGROUND: Recent research has indicated that bacteria within a biofilm may undergo changes in susceptibility to antimicrobial agents when compared to planktonic forms. This study was conducted to determine the bactericidal effect of an essential oil-containing mouthrinse (Listerine Antiseptic) on dental plaque bacteria in situ. METHODS: 1-day-old plaque in 17 subjects was sampled at baseline from the buccal surfaces of diagonally contralateral maxillary and mandibular bicuspids and 1st molars. Subjects were then randomly assigned either an essential oil mouthrinse or a sterile saline negative control and rinsed under supervision with 20 ml for 30 s. 30 min later, plaque was sampled from the remaining contralateral posterior teeth. Subjects repeated these procedures with their respective alternate rinse after 1 week. Pooled plaque samples from each subject at each sampling period were stained with a commercially-available fluorescent stain which fluoresces live and dead bacteria green and red, respectively. The stained plaque specimens were analyzed using computerized image analysis. A separate in vitro study was conducted to determine the relationship between the % red stain per sample and bacterial viability. RESULTS: Analysis of vital stained plaque specimens indicated that following rinsing with the essential oil mouthrinse, 78.7% of bacteria were dead compared to 27.9% following rinsing with the negative control (p<0.001). The in vitro findings demonstrated that the % red stain per sample is reflective of actual bacterial kill. CONCLUSIONS: This study confirms the findings of previous in vitro and in vivo studies which demonstrated the essential oil mouthrinse to have significant biocidal activity against oral micro-organisms. These studies all support the primacy of a bactericidal mechanism in producing the plaque and gingivitis reductions observed in numerous clinical trials conducted on the essential oil mouthrinse.

Anti-Infective Agents, Local↗
PubMed2000

Effect of an essential oil-containing antiseptic mouthrinse on induction of platelet aggregation by oral bacteria in vitro.

BACKGROUND: With an increasing body of data suggesting an association between periodontitis and cardiovascular disease, studies have been conducted to elucidate potential mechanisms by which oral bacteria might exert systemic effects. 2 oral bacteria, Streptococcus sanguis and Porphyromonas gingivalis, have been shown to induce platelet aggregation in vitro. This study was conducted to determine the effect of treatment with an essential oil mouthrinse (Listerine Antiseptic) on the platelet-aggregating activity of these organisms. METHOD: Bacteria were grown under standard culture conditions. S. sanguis ATCC strain 10556 was exposed for 3 min to the essential oil mouthrinse at either full strength or a 1:1 dilution, while P. gingivalis FDC strain 381 was exposed to the essential oil mouthrinse at a 1:10 dilution. Positive control cells were treated with Hanks balanced salt solution (HBSS). Aggregation was measured using a recording platelet aggregometer. The assay of each organism in its respective mouthrinse dilution(s) or HBSS was repeated 5 times. RESULTS: In all cases, the HBSS-treated organisms induced platelet aggregation, with mean(+/-S.E.) lag times of 12.30 (+/-1.36) min and 11.36 (+/-0.58) min for P. gingivalis and S. sanguis, respectively. In contrast, treatment with the essential oil mouthrinse completely inhibited the platelet aggregating activity of P. gingivalis and of S. sanguis exposed to the 1:1 mouthrinse dilution in all assays; the aggregating activity of S. sanguis treated with full-strength mouthrinse was completely inhibited in 4 of 5 assays, and inhibited by 75% in the 5th, for a mean inhibition of 95 +/- 1.5%. CONCLUSION: This study provides additional evidence that the essential oil mouthrinse can interfere with bacterial cell surface-associated activities which may have clinical relevance.

Drug Combinations↗
PubMed2000

Forskolin increases the expression of the pancreatic tumor antigen, Nd2, and uptake of Nd2 antibody.

Nd2 antibody recognizes an antigen that is tumor specific in pancreas. It has been used successfully in clinical radioimmunodetection studies to identify exocrine pancreatic tumors. In the present study we show that the uptake of radiolabeled Nd2 antibody by SW1990 pancreatic carcinoma cells was increased by the adenyl cyclase activator, forskolin. Dibutyryl cyclic AMP and forskolin were both effective in increasing the level of Nd2 antigen in SW1990 cells. Immunoprecipitation studies showed that the Nd2 epitope is associated with MUC1 mucin. Forskolin increased Nd2/MUC1 antigen in both a membrane fraction and a high buoyant density mucin-like fraction. Nd2 immunoreactivity was reduced by treatment of mucins with proteases and beta-mercaptoethanol. Immunohistochemical studies showed that periodate catalyzed beta-elimination greatly reduced Nd2 immunoreactivity. These results suggest that the Nd2 epitope is unusual in having characteristics of both a peptide and a carbohydrate, protease and conformation sensitivities and involvement of O-linked oligosaccharides. Nd2 antibody does not react with several known pancreatic cancer antigens. In summary, activation of the cyclic AMP pathway increased cellular uptake of Nd2 antibody and the cellular expression of the tumor-specific, mucin-associated Nd2 antigen. These results suggest a means of improving the effectiveness of monoclonal antibodies in targeting tumor antigens for the diagnosis and treatment of malignancy.

Amino Acid Sequence↗
PubMed1998

[Application of antigen linked with chemicals on nitrate cellulose membrane for dot-enzyme immunoassay].

HCMV-IgG in sera of pregnant women was detected by means of dot-enzyme immunoassay (DEIA), in which antigen was cross-linked on nitrate cellulose membrane through chemical reagent. The results showed better repetition by DEIA, compared with ELISA, and no significant differences were noted between the two methods in the rates of detecting HCMV-IgG in positive, weak positive and negative sera. The rate of agreement was 93.2%. In examining the sera which had been examined by ELISA for three times with the same, results the sensitivity, specificity, index and efficiency of diagnosis by DEIA were 100%, 96.6%, 196.6% and 98.7% respectively. Since this method is convenient, fast, of good repetition, economical and its diagnosis index meets the application criterion, it is more suitable for clinical laboratories.

Cellulose↗
PubMed1998

[Preparation and characterization of monoclonal antibodies against Clonorchis sinensis].

AIM: To develop and identify monoclonal antibody (McAb) against adult Clonorchis sinensis. METHODS: BALB/c mice were immunized with soluble antigen of adult Clonorchis sinensis, the spleen cells of immunized mice were fused with myeloma cell line SP2/0. Then the hybridoma cell lines secreting high titer of McAbs were screened. The Ig subtypes and titer of the McAbs were assayed with ELISA. The antigens recognized by the McAbs were examined with IFAT and identified by immunoblot analysis. The cross reactions between the McAbs and antigens of Schistosoma japonicum, Paragonimus westermani and Cysticercus cellulosae were detected. RESULTS: 5 hybridoma cell lines secreting high titer of McAbs against adult Clonorchis sinensis were established. All five clones of McAbs belonged to IgM subtype. The antigens recognized by the McAbs were located at the intestinal tract wall of adult Clonorchis sinensis. The McAbs had no cross reactions with antigens of Schistosoma japonicum, Paragonimus and Cysticercus cellulosae. CONCLUSION: 5 hybridoma cell lines against adult Clonorchis sinensis secreting high titer of McAbs with high specificity were established.

Animals↗
PubMed1997

Caged cysteine and thiophosphoryl peptides.

Photoreleasable molecules are important in studies of various biological phenomena, especially cell signaling. Here we report a generally applicable approach for 'caging' unprotected cysteine-containing or thiophosphorylated peptides in aqueous solution with 2-nitrobenzyl bromides. Photolysis of the caged peptides was achieved with near UV light with product quantum efficiencies of 0.064-0.62 under conditions that produced no damage to attendant biological macromolecules. Yields of uncaged peptides were 55-70%. Selective reaction of the side-chain of thiophosphoryl serine with 2-nitrobenzyl bromide in the presence of a cysteinyl residue was also demonstrated, establishing a means for functional caging of various signal transduction proteins without prior modification or mutagenesis.

Cysteine↗
PubMed1997

Protein architecture, dynamics and allostery in tryptophan synthase channeling.

The alpha 2 beta 2 form of the tryptophan synthase bienzyme complex catalyses the last two steps in the synthesis of L-tryptophan, consecutive processes that depend on the channeling of the common metabolite, indole, between the sites of the alpha- and beta-subunits through a 25 A-long tunnel. The channeling of indole and the coupling of the activities of the two sites are controlled by allosteric signals derived from covalent transformations at the beta-site that switch the enzyme between an open, low-activity state, to which ligands bind, and a closed, high-activity state, which prevents the escape of indole.

Allosteric Regulation↗
PubMed1997

Immune bioactivity in shellfish toward serum-free cultured human cell lines.

The biologically functional effect of eight kinds of hot-water extracts of shellfish on cultured human cell lines was examined in a serum-free medium model. Meretrix lusoria and Sinonovacula constricta extracts enhanced IgM secretion of both hybridoma HB4C5 and SI102 cells when cultured with the respective extracts. The purified principle exhibited remarked activity in the adsorbed fraction in hydroxyapatite and Concanavalin A columns. The extracts of Corbicula fluminea, Crassostreas gigas, Meretrix lusoria, Anadara granosa, and Sinonovacula constricta enhanced in nitroblue tetrazolium (NBT)-reducing ability of macrophage U-M cells. Meretrix lusoria, Anadara granosa, and Sinonovacula constricta were specifically cytotoxic to both cultures of MCF-7 breast cancer cells and HuH-6KK hepatoblastoma. These findings imply that the extracts of shellfish that were examined exhibited a differential effect on immune cells and tumor cells.

Animals↗
PubMed1996

beta-Site covalent reactions trigger transitions between open and closed conformations of the tryptophan synthase bienzyme complex.

The tryptophan synthase bienzyme complex (alpha2beta2) from Salmonella tryphimurium catalyzes the final steps in the biosynthesis of L-Trp. To investigate the roles played by conformational change in tryptopthan synthase catalysis, the fluorophore 8-anilino-1-naphthalensulfonate (ANS) is used to identify conformational states. The binding of ANS to the alpha2beta2 bienzyme complex is accompanied by a dramatic enhancement of ANS fluorescence and a shift of the emission maximum from 520 to 482 nm. The ANS binding isotherm is biphasic and consists of a class of moderately high-affinity, noninteracting sites with a stoichiometry of 1 site/alpha beta dimeric unit (Kd' = 62 + or - 15 micrometer) and a much weaker set of non-specific interactions with K'd>1mM. Our findings show that the affinity of the enzyme for ANS is strongly decreased (> 10-fold) by interactions at two loci 30 angstroms apart: (i) the binding of the alpha-site ligands, 3-indole-D-glycerol 3'-phosphate or alpha-glycerol phosphate (GP) or (ii) reaction at the beta-subunit to form either the alpha-aminoacrylate Schiff base, E(A-A), or quinonoid species, E(Q). In contrast, formation of the L-Ser and L-Trp external aldimines E(Aex1) and E(Aex2) at the beta-site causes a 2-3 fold decrease in the affinity of the enzyme for ANS. The combination of E(A-A)or E(Q) with GP brings about almost complete displacement of ANS, indicating that these interactions drive a conformation change in alphabeta subunit pairs which prevents the binding of ANS. These results are consistent with a model which postulates that alphabeta subunit pairs undergo ligand-mediated transitions between open and closed conformations during the catalytic cycle. Consistent with the kinetic data showing that binding of alpha-site ligands increases the affinity of the beta site for L-Ser and that formation of E(A-A) activates the alpha reaction [Brzović, P. S., Ngo, K., & Dunn, M. F. (1992) Biochemistry 31, 3831-3839], while mutations in alpha subunit loops 2 and 6 prevent the ligand- mediated transition to a closed structure [Brzović, P.S., Hyde, C.C., Miles, E.W., & Dunn, M.F. (1993) Biochemistry 32, 10404-10413], we conclude that reciprocal ligand-mediated allosteric interactions between the heterologous subunits promote conformational transitions between open and closed structures in alphabeta subunit pairs which function to coordinate catalytic activities and facilitate the channeling of indole between the two catalytic sites.

Anilino Naphthalenesulfonates↗
PubMed1994

Modulation of the activity of mitochondrial aspartate aminotransferase H352C by the redox state of the engineered interdomain disulfide bond.

Molecular modeling suggested that the large and small domain of mitochondrial aspartate aminotransferase might be linked by an engineered disulfide bond that could be expected to interfere with ligand-induced and syncatalytic changes in conformation and thus to assist in the elucidation of their significance for the catalytic mechanism. His-352, which is situated in the small domain close to Cys-166 of the large domain, was replaced with a cysteine residue by oligonucleotide-directed mutagenesis. Aspartate aminotransferase H352C, that had not been exposed to reducing conditions, in part contained a disulfide bond between Cys-166 and Cys-352. Exposure to a reducing agent cleaved the crosslink completely and produced an enzyme derivative with 8% of the activity of the wild type enzyme. Cu2+-mediated autoxidation resulted in complete formation of the disulfide bond and a decrease in enzymic activity to 2%. Independently of the redox state of the disulfide bond, the H352C substitution seems to shift the equilibrium from the open toward the closed conformation of the enzyme. This change in conformation was accompanied by an increase in the binding affinity for both the amino and oxo acid substrate by one order of magnitude. Apparently, 1-2 kcal/mol of the binding energy of the substrates are no longer diverted to shift the conformational equilibrium toward the closed conformation. The kcat/Km values were unchanged or even increased in the reduced form of the mutant enzyme and only slightly decreased in its oxidized form. Both the disulfide-independent decrease in enzymic activity, as observed in reduced aspartate aminotransferase H352C and also in two other mutant enzymes (C166H/H352C and H352Q), and the redox-dependent modulation of activity indicate that unhindered domain movements are essential for full catalytic competence of aspartate aminotransferase.

Animals↗