Biomedical subjects

Y Tang

Publications and source records attributed to Y Tang.

At least 379 records · Page 21Linked to original sources

PubMed1994

Comparison of cardiac electrophysiologic effects of experimental hypothyroidism and chronic oral amiodarone administration in dogs.

A comparative study on ventricular electrophysiologic effects of experimental hypothyroidism and chronic oral amiodarone administration was made in canine models, with the application of electrical stimulation and monophasic action potential recording. The results showed similar effects possessed by hypothyroidism and amiodarone, which included prolongations in ventricular repolarization and refractoriness, an increase in ventricular fibrillation threshold, and a decrease in the incidence of reperfusion ventricular fibrillation. The differences were that hypothyroidism primarily lengthened phase 2 repolarization and had no effects on intraventricular conduction time, whereas amiodarone lengthened both phase 2 and phase 3 repolarization and suppressed myocardial conduction velocity.

Amiodarone↗

PubMed1994

[Effects of dingduwan on electric activities of gastrointestinal smooth muscle and effect of gastrointestinal motility].

Dingduwan (DDW) is a Chinese herbal medicine. Method of modified synchronous recording was used to study the electric activities of gastrointestinal (GI) smooth muscle and the effect of GI motility treated by DDW. A dosage of 3.5 g/kg for ingestion in rats markedly increased the average amplitude of GI slow wave, the total amplitude of GI motion, the rate of GI slow wave and intestinal motion (P < 0.05), but it had no significant effects on the frequency of gastroelectric slow wave and gastric motility (P < 0.05). DDW in the dosage of 5.2 g/kg for ingestion markedly promoted the recovery of intestinal intussusception in mice (P > 0.05). The results showed that DDW markedly increased the intestinal electricity and motility more than that of stomach.

Animals↗

PubMed1993

Characterization of two alternatively spliced 5'-untranslated exons of the human CD36 gene in different cell types.

We determined the nucleotide sequence of a 2.6-kb BamHI-EcoRI fragment from the 5'-end of the human gene encoding the cell adhesion receptor, CD36. This region contains the first coding exon, exon 3, as well as two non-coding exons, exons 2a and 2b, from the 5'-flanking region. Also present in the 5'-flanking region are two Alu repeats belonging to the Alu-Sa subfamily. When the determined genomic sequence was compared to a placental cDNA sequence [Oquendo et al., Cell 58 (1989) 95-101] and to a human erythroid leukemia (HEL) cell CD36 cDNA sequence (this report), we found that exons 2a and 2b do not occur within the same mRNA, suggesting that alternative splicing occurs within the 5'-untranslated region (UTR) of human CD36 pre-mRNA. These observations were confirmed by reverse transcriptase-coupled polymerase chain reaction (RT/PCR) assays using RNA from placental tissue, HEL cells and human platelets. Exon 2b encodes two alternative translation initiation codons which may render exon 2b-containing CD36 mRNA untranslatable. To test this hypothesis, we transfected COS-1 cells with an exon 2b-containing CD36 cDNA construct. Using anti-CD36 polyclonal antibody, we were able to detect an immunoreactive protein, consistent in size with the mature protein observed in transfected COS-1 cells. Therefore, exon 2b itself is insufficient to block translation of CD36 mRNA.

Amino Acid Sequence↗

PubMed1993

Refined 1.6 A resolution crystal structure of the complex formed between porcine beta-trypsin and MCTI-A, a trypsin inhibitor of the squash family. Detailed comparison with bovine beta-trypsin and its complex.

The crystal structure of the complex formed by porcine beta-trypsin with the MCTI-A inhibitor (Momordica charantia, Linn. Cucurbitaceae) has been determined at 1.6 A resolution using the molecular replacement method. The sequence of MCTI-A was determined by recognizing the electron density, and shows that MCTI-A is a member of the squash family of trypsin inhibitors. We report the first high-resolution structure of porcine beta-trypsin. Detailed comparisons have been made on the overall structure, solvent structure and active-site geometries between this complex and bovine beta-trypsin and its complexes. On the basis of our results, we discuss the interaction patterns between inhibitor and trypsin. Unlike other complex structures formed by bovine trypsin with inhibitors, no out-of-plane distortion around the inhibitor's scissible peptide was observed. The role of the trypsin catalytic triad is also discussed on the basis of this structure.

Animals↗

PubMed1993

Effects of immunization with the p12 proteins of LP-BM5 defective and ecotropic viruses on development of MAIDS.

Among murine leukemia viruses (MuLV) present in the LP-BM5 virus mixture, the agent etiologic for an acquired immunodeficiency syndrome (MAIDS) is replication defective, containing only a single open reading frame which includes all of gag. The Gag polyprotein encoded by the defective virus, termed BM5def, differs most in p12 from that of nonpathogenic ecotropic virus (BM5eco). As one approach to examining the role of p12 in disease, the ecotropic and defective virus forms of the protein, synthesized in bacteria, were used to immunize three strains of mice differing in their sensitivity to MAIDS. In each strain, both proteins elicited substantial antibody responses that were cross-reactive with either p12 and recognized the proteins as part of intact viral Gag polyproteins. Immunization with either p12 before infection with LP-BM5 viruses had no effect on the sensitivity or resistance of mice to MAIDS or on the extent of helper virus spread. The variant p12 of BM5def, when presented on its own, is thus not a crucial antigenic determinant of disease. Alternative mechanisms by which BM5def may contribute to MAIDS are discussed.

Amino Acid Sequence↗

PubMed1993

No alpha-lactalbumin-like activity detected in a low molecular mass protein fraction of rat epididymal extract.

The same low M(r) protein fraction of epididymal luminal fluid as that studied previously by Hamilton in 1981 was assayed for alpha-lactalbumin (alpha-lac) activity with bovine milk galactosyltransferase (GalTase) as the enzyme source and bovine serum albumin (BSA) to make the total protein concentrations of all the samples in each assay constant. No alpha-lac activity could be detected in this fraction. When glucose was used as an acceptor, radioactivity passing through the ion exchange column used to retain the remaining UDP-galactose did increase with the amount of the proteins of the low M(r) fraction, but this increase was observed not only for samples with an acceptor but also for samples without. The increased radioactive product co-migrated in high-voltage electrophoresis with galactose, not lactose. When GlcNAc was used as an acceptor, the situation was the same, and the increased radioactive product co-migrated with galactose, not LacNAc. No inhibition of bovine milk GalTase activity by the low M(r) proteins was observed. Addition of protein, either BSA or the low M(r) fraction of epididymal luminal fluid, to assay medium that contained no proteins other than GalTase enhanced the GalTase activity both in forming lactose in the presence of glucose and also LacNAc in the presence of GlcNAc. It appears that the earlier reports of alpha-lac-like activity in epididymal fluids and extracts may have been due to the presence of enzymes liberating free galactose from UDP-galactose and/or a stimulatory non-specific effect of the protein in the solutions on the lactose synthesis activity of the GalTase.

Animals↗

PubMed1993

Phlebotomine sandflies of Kenya (Diptera: Psychodidae). I. The validity of Phlebotomus (Larroussius) elgonensis Ngoka, Madel and Mutinga.

Sandflies collected in Kitum cave on the Kenyan side of Mount Elgon were identified as Phlebotomus (Larroussius) elgonensis Ngoka, Madel and Mutinga, a species synonymized with P. (L.) aculeatus Lewis, Minter and Ashford, by D. J. Lewis. A comparison of the flies from Kitum cave with P. aculeatus from Lake Elmentaita, Kenya, shows marked differences in the lengths of: (a) the spermathecal ducts of the female; (b) the style, coxite, genital pump and aedeagus of the male; and (c) the palpal segments of both sexes. Other notable differences are in the shape of the base of the spermathecal ducts; the position of spines on, and the shape of, the tip of the aedeagus; and the appearance of the pharyngeal armatures of both sexes. Phlebotomus elgonensis is redescribed and it is concluded that it is sufficiently different from P. aculeatus to deserve recognition as a valid species.

Animals↗

PubMed1993

Primer extension preamplification for detection of multiple genetic loci from single human blastomeres.

A new technology called primer extension preamplification (PEP), which has been applied to single spermatozoa, increases the amount of polymerase chain reaction (PCR) templates by amplifying DNA of the whole genome. The current investigation was aimed at applying PEP to single human blastomeres. Two blastomeres with nuclei from arrested embryos were selected for this study. Using three different PEP protocols (experiments I, II and III), DNA from single blastomeres was amplified using 15-base oligonucleotide random primers. The efficiency of the procedure was determined by further amplifications of aliquots of the PEP products with two specific sequences. Three aliquots from each PEP product were used as PCR templates for the human X chromosome (X) or the exon 10 of the cystic fibrosis gene (CF). PCR amplified products were analysed by gel electrophoresis. In experiment I, when X primers were used, positive signals were detected in all 10 embryos (100%), 90.0% (18/20) of the blastomeres, and in 80.0% (96/120) of the replicates. When CF primers were amplified, all embryos (100%, 10/10), 90.9% (18/20) of the blastomeres and 78.3% (47/60) of the replicates were positive. In experiment II, efficiency was significantly reduced when total time for the procedure was minimized from 8 h to 5 h and 45 min. Although the time was further reduced to 4 h and 40 min in experiment III, the efficiency remained the same as in experiment I when the volume of PEP was reduced from 60 microliters (experiments I and II) to 40 microliters. One out of 132 control replicates (0.8%) was contaminated.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastomeres↗

PubMed1993

Defining topological equivalences in protein structures by means of a dynamic programming algorithm.

An automatic algorithm for defining topological equivalences in protein structures is presented. The algorithm is based on a dynamic programming technique and self-consistent scoring method. We have used it to align pairs of similar protein structures of several protein families and to identify recurrent structural domains in aspartic proteinase 2APR. Its ability to find suboptimal paths permits a thorough comparison of proteins at each level in the hierarchy of the protein structure: secondary structure, super-secondary structure, domain and entire globular structure. The algorithm has been extended to the structure alignment of ribonucleic acid and can be extended to the structure alignment of any linear polymer.

Algorithms↗

PubMed1993

The Cdk-associated protein Cks1 functions both in G1 and G2 in Saccharomyces cerevisiae.

The CKS1 gene of Saccharomyces cerevisiae encodes a small essential protein shown to interact genetically and physically with the Cdc28 protein kinase. To investigate the specific functions of the CKS1 gene product, conditional temperature-sensitive mutant alleles were generated. The mutations were found to impair the ability of cells to undergo both the G1/S-phase and G2/M-phase transitions of the cell cycle, as well as the ability to bud. Mutants were not defective, however, in their ability to activate Cdc28 kinase as assayed in vitro on the substrate histone H1. It is likely, therefore, that Cks1 mediates a more specialized function of the Cdc28 kinase such as its ability to form specific multimeric complexes or to localize properly in cellular compartments.

Adaptor Proteins, Signal Transducing↗

PubMed1993

Retrovirus-induced lymphoproliferation as a model for developing diagnostic criteria for malignant lymphoma in mice.

Several methods for evaluating lymphoproliferative lesions in mice were compared. The model systems included spontaneous lymphomas arising in CWD mice and NFS mice congenic for ecotropic murine leukemia virus (MuLV) induction loci and a series of transplants in mice with severe combined immunodeficiency disease mutation of cells derived from mice infected with LP-BM5 MuLV. Primary lymphomas and donor tissues and transplants were examined using histopathology, flow cytometry, and Southern blot analysis of DNA for rearrangements of immunoglobulin and T-cell receptor genes and for viral integrations. The use of flow cytometric analysis, to establish cell lineage and define population size, and DNA analysis, for cell lineage and clonality determination, allowed the identification of malignant lymphoproliferations. Histologic evaluation did not define clonal populations of particular lineage but did provide other indications of malignancy such as invasiveness and presence of a dominant morphologic cell type. Thus, the precision of diagnosis of mouse lymphomas can be considerably enhanced by augmenting histopathologic examination with antigenic and molecular characterizations that can define malignant populations.

Animals↗

PubMed1993

[Experimental and clinical study on cryptosporidiasis. III. Ultrastructural observation on Cryptosporidium in immunosuppressed mice].

The ultrastructure of Cryptosporidium parvum, which parasitized on the surface of the intestine of the immunosuppressed mice, was studied by transmission electron microscopy. The parasite was enveloped by the parasitophorous vacuole developed from the host epithelial cell. An electron dense band was found at the attachment site between the Cryptosporidium and the host cell. At the attachment site, the cytoplasma membrane of Cryptosporidium appeared in the form of many membranous folds, and contacted closely with the plasma membrane of the epithelial cell. Rhoptry-like structure and small electron dense granules were found in the merozoite, but their effects on the development of Cryptosporidium are still unknown (Figs. 1-5).

Animals↗

PubMed1993

Molecular epidemiologic study of an outbreak of Salmonella typhimurium infection at a newborn nursery.

Plasmid analysis, restriction endonuclease analysis, antimicrobial susceptibility testing, biotyping, phage typing and outer membrane protein electrophoresis were used to study an outbreak of Salmonella typhimurium infection at a newborn nursery. Seven out of the 12 neonates had positive blood cultures for S. typhimurium, and 2 of them died of severe sepsis. Thirty epidemic strains of S. typhimurium belonging to phage type 12 had the same plasmid profiles (98.0, 6.7 and 3.8 Kb) and identical restriction digest patterns (23.0, 20.4, 15.0, 9.6, 8.2, 7.4, 5.8, 4.3, 3.8, 2.0 and 1.8 Kb) which were different from those of the 2 non-epidemic strains. Laboratory data suggested that the source of the infection was the index patient's mother who had a slight diarrhea; the mode of transmission was most likely due to the transfer of organisms from infant to infant by the contaminated hands of nurses during milk feeding.

Amikacin↗

PubMed1993

[The applicability of a new stable fluorescence reagent CGE (N) for TLC measurements and spectrofluorimetry].

A new stable fluorescent reagent, CGE (N), was designed and synthesized in our laboratory. This paper presents the results of using it to detect a compound having aminogroup. Glycine as an example was derived by using CGE (N), the best condition of derivatisation reaction was pH8, T 50 +/- 1 degree C, and time 3-5 h. Spread agent was CHCl3: CH3OH:CH3COOC2H5: iceHAc (1:3:5:1). Rf of glycine-CGE (N) was 0.45, of which fluorescent spectrum Em was 356nm (at Ex = 277nm). The correlation coefficient between the fluorescent scanning area and quantity was over 0.99, the linear relation retained for 24 h, the detection limit 0.24 microgram, and the linear range 0.24-19.2 micrograms. The data revealed that stability, sensitivity and reproducibility were good. These indicate that CGE(N) is a fine fluorescent reagent for compounds having primary amino-group and this method is reliable.

Chromatography, Thin Layer↗

PubMed1993

Structure of the channel catfish (Ictalurus punctatus) growth hormone gene and its evolutionary implications.

A DNA fragment of 1.6 kilo base pairs (kb), encoding part of the channel catfish (Ictalurus punctatus) growth hormone (GH) gene, was generated by the polymerase chain reaction (PCR) using 2 degenerate synthetic oligonucleotides (30 and 33 mer) derived from the N- and C-terminal amino acid sequences of the catfish GH polypeptide as amplification primers and with catfish genomic DNA as a template. This DNA fragment was used as a probe for the isolation of a catfish GH gene from a genomic library constructed in a lambda phage cloning vector, lambda Dash II. Three positive clones were isolated, and their complete nucleotide sequences were determined. Nucleotide sequences from clones 1 and 3 were identical, whereas clone 2 had 2 base substitutions. The gene spans approximately 3 kb and is comprised of 5 exons and 4 introns. The initiation codon, the termination codon, and the canonical polyadenylation sequence were identified. The amino acid sequence deduced from the predicted coding region of the gene is in agreement with that of the native GH polypeptide sequence. A sequence (TATAAAA) matching the TATA box consensus sequence was located at nucleotide positions -30 to -23. Furthermore, 2 sequences corresponding to the mammalian Pit-1/GHF-1 binding sites (consensus sequence TT[AA]TATNCAT) were identified in the 5' flanking region starting at positions -113 and -134. Another sequence (GTACCAGTGA) conserved among the GH genes of the channel catfish and other known animal species was also identified at position -220. The biological functions of this sequence remain to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1993

[Induction of micronucleus by organophosphorus pesticides both in vivo and in vitro].

A total of 22 organophosphorus pesticides (OPPs), including 8 ethyl-, 9 methyl-, and 5 other OPPs, were tested for mutagenicity in micronucleus assay system both in 615 mouse marrow cells in vivo with multi-intraperitoneal administrations and in cultured Chinese hamster lung (CHL) cells in vitro; and structure-mutagenicity relationship of OPPs was analyzed. Among the OPPs tested in vivo, 5 ethyl-(diazinon, chlorpyrifos, disulfoton, ethion, and parathion), and only 1 methyl-(dimethoate) were found mutagenic, while the other OPPs were negative. Six ethyl- (azinphos ethyl, chlorpyrifos, ethion, parathion, phosaione, and quinaphos), 8 methyl- (azinophos methyl, chlorpyrifos methyl, dichlorvos, dimethoate, fenitrothion, malathion, parathion methyl, and trimethyl phosphate), and 2 other OPPs (EII and MIA), however, induced micronucleus in CHL cells in vitro. The results indicated that most of the ethyl-OPPs tested showed the ability to induce micronucleus both in vivo and in vitro, and that most of the methyl-OPPs were positive only in vitro. The mechanism for the adversity of mutagenic activity in micronucleus assay in vivo and in vitro produced by different kinds of OPPs was also discussed.

Animals↗

PubMed1993

Syncope in nasopharyngeal carcinoma: report of three cases and review of the literature.

Syncope is an uncommon symptom in patients with nasopharyngeal carcinoma (NPC). Here we report three cases of NPC with syncope. One had bilateral neck masses, invasion of the skull base, and lower cranial nerve palsies. The other two presented with neck mass only. Repeated episodes of syncope were initially controlled by intravenous atropine followed by radiotherapy and/or chemotherapy. The large primary tumor with parapharyngeal space extension and neck lymph node involvement, the invasion of the skull base and the presence of lower cranial nerve palsies are the three important risk factors for developing syncope. This is probably mainly due to the mass compression of the carotid sinus or the glossopharyngeal nerve invasion. We therefore classified these 3 cases into carotid sinus syncope type, glossopharyngeal neuralgia type and parapharyngeal space lesions type. The prognosis is poor for cases of NPC with syncope because most patients have advanced or recurrent disease, however, atropine and radiotherapy with or without chemotherapy are effective for the symptomatic treatment of syncope from locally advanced NPC.

Adult↗

PubMed1992

Chiral separation of nipecotic acid amides.

1-Decyl-3-(N,N-diethylcarbamoyl)piperidine (1) and alpha,alpha'-bis[3-(N-benzyl-N-methylcarbamoyl)piperidinol]-p-xyle ne (2) represent mono-N-substituted and bis-N-substituted carbamoylpiperidines, or nipecotic acid amides, respectively. Initially, several attempts were made to resolve these compounds using beta-cyclodextrin, cellulose carbamate and Pirkle-type columns. However, the interactions of the stereoisomers of the two compounds with these stationary phases did not differ enough to permit satisfactory separations. Baseline resolution was achieved using an alpha 1-acid glycoprotein (AGP) chiral column. The mobile phase was phosphate buffer (pH 7.0). Tetrabutylammonium (TBA) was used as the cationic modifier and ethanol as the uncharged modifier. Circular dichroism was used to identify the enantiomers. Compound 1 was resolved into positive and negative enantiomers and 2 into positive and negative enantiomers and a meso diastereomer. The influence of pH, buffer ionic strength, cationic and uncharged modifier concentrations on retention, chiral selectivity and resolution were evaluated. Based on the results, it is suggested that both ionic and hydrophobic interactions may be responsible for retention and resolution.

Buffers↗