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Biomedical subjects

J Yuan

Publications and source records attributed to J Yuan.

At least 343 records · Page 19Linked to original sources
PubMed1993

Studies on caproic acid fermentation using immobilized cells.

Five carriers were tested for immobilizing caproic acid bacteria. The batch experiment results showed that the calcium alginate was the best one of the five immobilized materials. The characteristics of immobilized caproic acid bacteria cells were evaluated using a standard batch fermentation procedure. In the laboratory-scale experiments, the alginate beads could be maintained at least for 8 months with the yield of the caproic acid level about 11 mg/ml. Under optimum conditions, a maximum yield of caproic acid about 15 mg/ml could be obtained. The observed productive acid rate and its yield of immobilized cells appeared to be greater than that of the corresponding free cells suspension. The cell number per volume of immobilized cells was about ten times that of free cells.

Alginates↗
PubMed1993

Determination of apolipoprotein E genotypes by single-strand conformational polymorphism.

We used single-strand conformational polymorphism (SSCP) to determine apolipoprotein E (Apo E) genotypes in 47 individuals. A 295-base-pair (bp) DNA fragment coding for amino acid residues 80-178 of the Apo E protein gave distinct patterns for the three alleles. When we used SSCP to determine the Apo E polymorphism of five individuals whose phenotyping results differed from those of genotyping, the SSCP results agreed with the genotyping results obtained by the PCR-based amplification refractory mutation system (ARMS). Because most of the reported rare alleles of the Apo E gene involve mutations of amino acid residues in positions 120-160, our SSCP method is useful for determining rare as well as common alleles.

Apolipoproteins E↗
PubMed1992

Epitope mapping by a method that requires no amino acid sequence information.

A simple, rapid method of epitope mapping has been developed that avoids the often cumbersome requirement of obtaining amino acid sequence information. The protein antigen is digested with various concentrations of carboxypeptidase into a nearly continuous series of polypeptides of different molecular weights, all containing a common N-terminus. The peptides are separated by polyacrylamide gel electrophoresis and then transferred to nitrocellulose paper. After developing the blot with the antibody to be mapped, a nearly continuous stain is observed extending from the position of the intact antigen to the molecular weight of the smallest N-terminal fragment still containing the antibody's epitope. By noting the molecular weight where the stain terminates, the position of the epitope relative to the N-terminus can be determined. Using this methodology, and taking special precautions to inhibit all endoproteinases in the carboxypeptidase preparation, the previously mapped epitopes of six nonoverlapping antibodies to the erythrocyte anion transporter were confirmed.

Amino Acid Sequence↗
PubMed1992

Isolation, characterization, and immunoprecipitation studies of immune complexes from membranes of beta-thalassemic erythrocytes.

beta-Thalassemia, a hemoglobinopathy that results in the precipitation of denatured alpha-globin chains on the membrane, is characterized by erythrocytes with significantly reduced lifespans. We have demonstrated previously that hemoglobin denaturation on the membrane can promote clustering of integral membrane proteins, and that this clustering in turn leads to autologous antibody binding, complement fixation, and rapid removal of the cell by macrophages. To evaluate whether this pathway also occurs in beta-thalassemic cells, we have isolated and characterized the immune complexes from the membranes of these cells. We observe that autologous IgG-containing complexes obtained by either immunoprecipitation or simple centrifugation of nondenaturing detergent extracts of beta-thalassemic cell membranes contain globin, band 3, IgG, and complement as major components. Absorption spectra of these complexes demonstrate that the globin is, indeed, mainly in the form of hemichromes. Immunoblotting studies further show that much of the band 3 protein in the aggregates is covalently cross-linked to a dimeric or tetrameric form, consistent with the preference of the autologous IgG for clustered band 3. Although the insoluble aggregates constitute only approximately 1.6% of the total membrane protein, they still contain 27% of the total IgG and 35% of the total complement C3 on the thalassemic cell surface. Because cell surface IgG and complement component C3 are thought to trigger removal of erythrocytes from circulation, the hemichrome-induced clustering of band 3 may contribute to the beta-thalassemic cell's shortened lifespan.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1992

Glycerophosphorylcholine phosphocholine phosphodiesterase activity in cultured oligodendrocytes, astrocytes, and central nervous tissue of dysmyelinating rodent mutants.

The levels of GPC phosphocholine phosphodiesterase, pNP phosphocholine phosphodiesterase, CNPase, and UDP galactose: ceramide galactosyltransferase activities were estimated with pure cultures of oligodendrocytes and astrocytes; mixed primary glial cells cultures; C-6 cells; and CNS tissue of the dysmyelinating md rat, the jimpy mouse, and the quaking mouse. The highest activity of GPC and pNP phosphocholine phosphodiesterases as with CNPase and C gal T was found in the pure cultured oligodendrocytes. C-6 cells had very low or undetectable activities for these two phosphodiesterases but possessed very high CNPase activity. The activity of GPC phosphocholine phosphodiesterase was significantly decreased in the CNS tissue of the md rat and the jimpy and the quaking mouse. Similar reductions were observed for the pNP phosphocholine phosphodiesterase, CNPase, and C gal T activities. The selective cellular enrichment in oligodendrocytes of the GPC phosphocholine phosphodiesterase activity and decreases of its activity in three dysmyelinating mutants in the same ratio as for CNPase and C gal T suggest that GPC phosphocholine phosphodiesterase is a myelin marker enzyme and it may reflect the quantity of myelin and oligodendrocyte present.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

Effect of gemfibrozil on composition of lipoproteins and distribution of LDL subspecies.

We studied the effect of gemfibrozil on the compositions of VLDL, LDL and distribution of LDL subspecies in type II hyperlipidemic patients. Gemfibrozil significantly lowered serum triglyceride levels in this group of patients who had normal to moderately elevated triglyceride prior to therapy. Gemfibrozil also changed the composition of VLDL by lowering its free cholesterol, cholesterol ester and raising the protein content. In contrast, no measurable changes in LDL chemical composition were found following gemfibrozil therapy. Changes in LDL, however, can be detected using ultracentrifugal and electrophoretic methods. Peak densities of LDL were lowered and LDL subspecies shifted to larger, slower-moving bands on gradient gel electrophoresis in patients receiving gemfibrozil treatment. These results suggest that gemfibrozil treatment resulted in qualitative changes in both VLDL and LDL even in patients with moderately elevated baseline serum triglyceride levels.

Adult↗
PubMed1992

Application of molecular encapsulation for toxicology studies: comparative toxicity of p-Chloro-alpha, alpha, alpha-trifluorotoluene in alpha-cyclodextrin vehicle versus corn oil vehicle in male and female Fischer 344 rats and B6C3F1 mice.

The application of alpha-cyclodextrin (alpha-CD) as an alternative vehicle for water insoluble and volatile chemicals was investigated in toxicity studies of p-chloro-alpha, alpha, alpha-trifluorotoluene (CTFT). Groups of F344 rats and B6C3F1 mice of each sex were administered CTFT (97% pure) by gavage in either corn oil or alpha-CD aqueous formulations daily for 14 consecutive days. The dose levels used were 10 (mice only), 50, 400, and 1000 mg/kg for corn oil vehicle and 10, 50, and 400 mg/kg (maximum achievable dose at gavage volume of 5 ml/kg) for alpha-CD vehicle. With both vehicles CTFT and alpha 2u-globulin were found to accumulate in the male rat kidney after 14 days of exposure and a dose-related toxic nephropathy was observed at dose of 50 mg/kg or higher. The hepatocellular hypertrophy and cytoplasmic vacuolation of the adrenal cortex which appeared in dosed male and female rats were also found to be independent of vehicle. Clinical pathology findings suggested a mild anemia and cholestasis in rats. With both vehicles no tissue bioaccumulation of CTFT was found in male or female mice. Vehicle-independent hepatocellular hypertrophy and cholestasis were also observed in mice at doses of 400 and 1000 mg/kg. In conclusion, the alpha-CD vehicle does not affect the toxic responses of CTFT in both sexes of both species. The results of the studies suggest that alpha-CD may be an appropriate alternative vehicle for toxicity studies.

Alpha-Globulins↗
PubMed1992

Predicting outcome for patients with node negative breast cancer: a comparative study of the value of flow cytometry and cell image analysis for determination of DNA ploidy.

This study was aimed at determining whether tumour DNA content measured by cell image analysis could provide additional prognostic information when compared to that provided by flow cytometry. Sections cut from paraffin blocks of tumours from 101 patients with node negative breast cancer were analysed by both methods and the results related to other prognostic variables and to patient relapse and overall survival. DNA ploidy measured by flow cytometry classified 46 tumours as diploid and 55 as aneuploid, whereas by cell image analysis 30 were diploid and 71 aneuploid (P less than 0.002). There were 20 tumours with discrepancies between the two methods; 18 of these were tumours with only one peak in flow analysis, but determined to be aneuploid with image analysis. DNA content as measured by both methods was significant for predicting relapse and survival by log-rank test, as were tumour histological grade, c-erbB-2 expression and tumour size. Multivariate analysis showed DNA ploidy measured by flow cytometry to be the only variable of independent significance (P less than 0.02) for both relapse and overall survival. Compared with cell image analysis, flow cytometry demonstrated a significantly higher proportion of diploid tumours, which may be related to differences in the internal standards applied to each method. We suggest that cell image analysis techniques can provide more sensitive information on the DNA content of tumour cells by direct measurement of nuclear DNA density of both normal lymphocytes and tumour cells in the same section. However, although image analysis appears to be more sensitive than flow cytometry in detecting DNA aneuploidy, the image technique appears to lack the specificity of flow cytometry in correlation with clinical outcome.

Adult↗
PubMed1992

The Caenorhabditis elegans cell death gene ced-4 encodes a novel protein and is expressed during the period of extensive programmed cell death.

Mutations in the gene ced-4 block almost all of the programmed cell deaths that normally occur during Caenorhabditis elegans development. We have cloned the ced-4 gene using a ced-4 mutation caused by the insertion of the transposon Tc4. When microinjected into a ced-4 animal, a 4.4 kb DNA fragment derived from the wild-type strain and corresponding to the region of the Tc4 insertion in the mutant ced-4(n1416) rescues the Ced-4 mutant phenotype. The ced-4 gene encodes a 2.2 kb RNA transcript. This mRNA is expressed primarily during embryogenesis, when most programmed cell deaths occur. The Ced-4 protein, as deduced from cDNA and genomic DNA clones, is 549 amino acids in length. Two regions of the putative Ced-4 protein product show some similarity to known calcium-binding domains.

Amino Acid Sequence↗
PubMed1992

[The study of rapid calculation on clearance creatinine rate in normal and epidemic hemorrhagic fever].

Height, weigh, urine volume/24 hours, serum creatinine (Scr) and urine creatinine were measured in 207 normal people and 232 patients with EHF. The clearance Creatinine rate (Ccr) was calculated by 24 hour urine volume method (therapy measure method) and Cockcroft's method (formulation method). The clearance creatinine rates between the two methods compared were significantly positive correlation, but the average values of Ccr in different stages in EHF were significantly different (P < 0.01). The result indicated that Cockcroft's Formulation was not fit for HFRS. According to the difference of Ccr in each stages of EHF, the adjustment values (ad) were presented and used to correct Cockcroft's formulation, thus, the adjusted Cockcroft's formulation could be obtained: Ccr = (140-ad-Age) x W/72 x Scr. In this paper, the Ccr of the adjusted method was compared with that of therapy measure method, the average values calculated by two methods were not different (P > 0.05). The result of 14 EHF Clinic practice demonstrated that between adjustment and practice measured methods were not significantly different. It shows that adjustment method is practical and available and can be used easily by clinic doctors in basic hospital.

Adolescent↗
PubMed1992

Prolonged D2 antidopaminergic activity of alkylating and nonalkylating derivatives of spiperone in rat brain.

Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and characterized chemically and pharmacologically. They included the N-methyl, N-phenethyl (NPS), and N-p-aminophenethyl (NAPS) derivatives, as well as the alkylating isothiocyanato (NIPS), bromacetamido, and ethylfumaramido p-substituted N-phenethylspiperones. These compounds showed high lipophilicity (log P up to 6.0 with NIPS), as well as very high in vitro D2 affinity (Ki = 35-280 pM) and D2 versus D1 selectivity (540-9000-fold) in radioreceptor assays with corpus striatum of rat brain. Of the alkylating series, NIPS showed the highest D2 affinity (57 pM) and D2 versus D1 selectivity (2040-fold) and so was selected for further evaluation. NPS, NAPS, and NIPS showed little or no affinity for 34 non-DA binding sites defined by radioligand assays for monoamine, amino acid, and peptide neurotransmitters, ion channels, peptide growth factors, and transmission mediators but did show low alpha 2 and moderate alpha 1 and 5-hydroxytryptamine (5-HT2) affinity with rat forebrain tissue in vitro; NIPS showed a marked gain in D2 versus 5-HT2 selectivity, compared with spiperone (1520- versus 26-fold). Systemic injections of NIPS induced marked decreases in rat striatal D2 binding sites 24 hr later, with little effect on D1, 5-HT2, or alpha 1 sites; NIPS and NAPS lowered apparent Bmax values at D2 receptors with little change in ligand affinity, ex vivo as well as in vitro. NPS, NAPS, and NIPS all induced dose-dependent lowering of D2 binding ex vivo (ID50 = 1-9 mumol/kg, intraperitoneally) and blocked the behavioral effects of the DA agonist apomorphine (0.9 mumol/kg) potently (ID50 = 0.3-0.5 mumol/kg) at 24 hr. Recovery from these anti-DA actions required about 1 week after equimolar (15 mumol/kg) and similarly effective doses of NPS and NAPS, as well as NIPS. Thus, highly selective and avidly bound lipophilic D2 affinity ligands with similarly avid in vitro and prolonged in vivo anti-DA activities can be derived from N-phenethylspiperones with or without an alkylating moiety present. Such affinity ligands may represent useful additions to previously used, generally less selective, D2 affinity ligands.

Alkylating Agents↗
PubMed1992

[The research and analysis on the fused primary teeth regarding to the permantent dental dentition-10 years follow up]

36 cases with unilateral mandibular fused primary teeth have been followed up and analysed for 10 years.The result showed that the fused primary teeth obviously affect the secondary permanent teeth and permanent dental dentition.In this series,there was one secondary permanent tooth lost in all of 19 cases.The secondary permanent tooth was also fused tooth in 3 cases.The length of permanent dental dentition and the width of dentition in front of the second cuspids in the cases with one secondary permanent tooth lost were extremely shorter than that in the cases with secondary permanent teeth.In addition,the mandibular dental dentitions were towards the fused teeth side.Comparing to the synonymic teeth,the mesial and distal steps and the height of secondary permanent teeth of fused primary teeth were no difference from normal side.

Journal Article↗
PubMed1991

Clustering of integral membrane proteins of the human erythrocyte membrane stimulates autologous IgG binding, complement deposition, and phagocytosis.

Damaged or old erythrocytes are cleared rapidly from circulation. Because several common biochemical lesions can induce the clustering of integral membrane proteins, we have proposed that formation of microscopic protein aggregates in the membrane might constitute a cell surface marker that promotes removal of the defective/senescent cells. We demonstrate here that treatments that cluster integral membrane proteins in erythrocytes (1 mM ZnCl2, 1 mM acridine orange, and 0.35 microM melittin) induce autologous IgG binding, complement fixation, and phagocytosis by human monocytes in vitro. Removal of the clustering agents prior to incubation in autologous serum or cross-linking of cell surface proteins before addition of clustering agents prohibited the above response, while cross-linking after treatment with the clustering agents preserved the response even if the clustering agents were later removed. Furthermore, subsequent reversal of the chemical cross-link maintaining the clustered distribution also reversed the induction of IgG binding, complement deposition, and phagocytosis. Finally, by deleting or inactivating different steps in the phagocytosis pathway, the chronology of steps was shown to be: (i) integral protein clustering, (ii) IgG binding, (iii) complement deposition, and (iv) phagocytosis.

Acridine Orange↗
PubMed1991

Isolation and partial characterization of antibody- and globin-enriched complexes from membranes of dense human erythrocytes.

In previous studies we have described a process whereby an erythrocyte in biochemical distress can initiate its own removal by macrophages of the reticuloendothelial system. This process involves the clustering of the integral membrane protein band 3 by denatured haemoglobin and the subsequent recognition of the exofacial poles of clustered band 3 and associated proteins by autologous antibodies. To determine whether this clearance pathway might mediate normal cell turnover, the fraction of normal erythrocytes containing the 0.5% densest cells, which are known to be destined for immediate removal, was isolated and characterized biochemically. This densest fraction was found to contain 6 times more membrane-bound globin (haemichromes) and 10 times more surface-bound autologous IgG than the other fractions containing cells of lower density. To determine whether the autologous IgG was physically associated with the haemichrome-stabilized membrane protein clusters, a procedure was developed for isolation and characterization of the microscopic aggregates. The isolated aggregates were found to contain a disulphide-cross-linked mixture of several membrane proteins, predominantly haemichromes, spectrin and band 3. Although the aggregates constituted only 0.09% of the total membrane protein, they still contained approximately 55% of the total cell-surface IgG. Since in control studies anti-(blood group A) antibodies, which are distributed randomly over the surface of type A cells, could not be recovered in the aggregate, we conclude that the autologous cell-surface IgGs were physically associated with the membrane protein clusters when they were co-isolated with them in our procedure. Thus the 640-fold enrichment of autologous IgG in the aggregates compared with regions of the membrane devoid of tightly clustered protein suggests that sites of integral protein clustering either are non-specifically sticky to IgG or are viewed as foreign or 'non-self' by the immune system and aggressively opsonized with IgG.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1991

Binding of lamin A to polynucleosomes.

Morphological observations suggest a close association between heterochromatin and the nuclear lamina. To investigate the molecular aspects of this association, we have established a simple sedimentation assay employing purified lamin proteins, or their 125I-labeled derivatives, and polynucleosomal particles isolated from avian erythrocytes. We report here that purified, unlabeled lamin A and 125I-lamin A, but not 125I-lamin B or 125I-bovine serum albumin, bind to polynucleosomes in a saturable and specific fashion. The specific binding of 125I-lamin A is of high affinity (Kd = approximately 1 x 10(-9) M) and is distinctly temperature-dependent. This interaction is not affected by exogenous polyionic agents such as polylysine and DNA, but it can be abolished by protease digestion of the polynucleosomes. These data suggest that nuclear lamin A maintains a direct association with a proteinaceous constituent of interphase chromatin.

Adenosine Triphosphate↗