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Biomedical subjects

X Dong

Publications and source records attributed to X Dong.

210 records · Page 12Linked to original sources
PubMed1990

[Relation of capsaicin-sensitive neurones to the effect of electro-acupuncture analgesia].

In this experiment, the rats treated with capsaicin (50 mg/kg) s. c. on day 2 of liqe were used 12 weeks after injection. The levels of substance P(SP) in sciatic nerves and dorsal spinal cords were measured with radioimmunoassay to evaluate the extent of C-afferent fibers damaged by capsaicin. The results as follows: (1) the levels of SP in the sciatic nerve and the dorsal spinal cord are decreased by 69% and by 62% respectively, indicating the degeneration of the primary C-afferent fibers is very massive; (2) the average of basal tail-flick latency (immersing in 50 degrees C water) is prolonged 105% as compared with the control; (3) after electro-acupuncture, the average of tail-flick latency of the capsaicin treated rats is increased by 81%, while that of the vehicle treated rats increased by 54%. These data suggest that C-afferent fibers substantially mediate the transmission of noxious thermal stimuli, but is unnecessary for the transmission of acupuncture message to induce analgesia.

Acupuncture Analgesia↗
PubMed1989

Synthesis of disaccharide fragments of dermatan sulfate.

Condensation of crystalline methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, provided 54% of methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-alpha-L-idopyranosyluronate)-beta-D-galactopyranoside . The use of methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl trichloroacetimidate)uronate as glycosyl donor, in the presence of trimethylsilyl triflate, improved the yield to 68%. Regioselective opening of the benzylidene group with sodium cyanoborohydride followed successively by O-sulfation with the sulfur trioxide-trimethylamine complex, saponification, catalytic hydrogenolysis and selective N-acetylation gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(alpha-L-idopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside. Condensation of methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-D-glucopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, gave methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosyluronate)-beta-D-galactopryano side in 85% yield. The sequence already described then gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(beta-D-glucopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside.

Carbohydrate Sequence↗
PubMed1985

Analysis of the individual regulatory components of the IncFII plasmid replication control system.

Replication of the IncFII plasmid NR1 is controlled by regulating the amount of synthesis of the repA1 initiator protein at both the transcriptional and translational levels. We have examined mutations which have altered each of these levels of regulation, resulting in different plasmid copy numbers. The genes which encode each of the individual wild-type or mutant regulatory components from the replication control region of NR1 have been cloned independently into pBR322 vectors, and their effects in trans, either individually or in various combinations, on plasmid incompatibility, stability, copy number, and repA1 gene expression have been defined.

Adenosine Triphosphatases↗
PubMed1985

Regulation of transcription of the repA1 gene in the replication control region of IncFII plasmid NR1 by gene dosage of the repA2 transcription repressor protein.

Transcription of the repA1 gene of the IncFII plasmid NR1 is initiated at two promoters in the replication control region. Transcription from the upstream promoter is constitutive at a low level, whereas transcription from the downstream promoter is regulated. The 5' end of the constitutively synthesized transcript also encodes the transcription repressor protein for the regulated downstream promoter. Therefore, the level of the repressor protein in the cell is gene dosage dependent. Using both lac gene fusions and quantitative hybridization methods, we have determined the in vivo relationship between the rate of transcription from the regulated promoter and the repressor protein concentration as a function of gene dosage. At the wild-type copy number of NR1, transcription from the regulated promoter is 96% repressed, but substantial derepression occurs when the copy number falls below the normal value. At or above the normal plasmid copy number, the basal level of repA1 mRNA is provided by transcription from the constitutive upstream promoter.

Adenosine Triphosphatases↗
PubMed1984

IncFII plasmid incompatibility product and its target are both RNA transcripts.

The region of DNA coding for incompatibility (inc) and copy number control (cop) of the IncFII plasmid NR1 is transcribed in both the rightward and leftward directions. The rightward transcripts serve as mRNA for the repA1 protein, which is required for replication. A small, 91-base leftward transcript is synthesized from the opposite DNA strand and is complementary to a portion of the rightward mRNA near its 5' end. A 262-base-pair Sau3A restriction fragment that encodes the small leftward transcript, but does not include the rightward transcription promoters, was cloned into the vector pBR322 or pUC8. The same fragment was cloned from an Inc- mutant of NR1 that does not make the small leftward transcript. Transcription through the cloned fragments in these derivatives was under control of the tetracycline resistance gene in pBR322 or the lac promoter-operator in pUC8. In one orientation of the inserted DNA, a hybrid transcript containing rightward NR1 RNA sequences was synthesized. In the other orientation, a hybrid transcript containing leftward NR1 RNA sequences was synthesized. These plasmids were used to vary the intracellular levels of the rightward or leftward NR1 RNA transcripts and to test their effects in trans on various coresident derivatives of NR1. An excess of rightward NR1 RNA in trans stimulated expression of the essential repA1 gene and caused an increase in the copy number of a coresident NR1 plasmid. An excess of leftward NR1 RNA in trans inhibited the expression of the repA1 gene and lowered the coresident NR1 copy number, thereby causing incompatibility. A pBR322 derivative with no transcription through the cloned NR1 DNA had no effect in trans. These results suggest that the small leftward transcript is the incompatibility inhibitor of NR1 and that its target is the complementary portion of the rightward mRNA.

Base Sequence↗
PubMedDate not supplied

Time of symptom onset of eight common medical emergencies.

Specific time periods of the day may be associated with different frequencies of symptom onset in different diseases. The purpose of the current study was to examine times of symptom onset in eight commonly encountered emergent conditions--cerebral infarction, cerebral hemorrhage, transient ischemic attacks, cardiac dysrhythmias, angina pectoris, acute myocardial infarction, gastrointestinal bleeding, and acute asthma. Data from 4554 cases were retrospectively reviewed. Symptom onset frequency curve diagrams were derived, illustrating peak hours of symptom presentation for each of the eight emergent conditions. Hormonal and metabolic factors that may be related to diurnal variations in symptom onset of the eight diseases are briefly discussed.

Acute Disease↗
PubMedDate not supplied

Neoglycoproteins with the synthetic complex biantennary nonasaccharide or its alpha 2,3/alpha 2,6-sialylated derivatives: their preparation, assessment of their ligand properties for purified lectins, for tumor cells in vitro, and in tissue sections, and their biodistribution in tumor-bearing mice.

Neoglycoproteins were prepared with chemoenzymatically synthesized complex biantennary N-glycan derivatives the nonreducing ends of which bear typical sequences found in glycoproteins. A chemically obtained biantennary heptasaccharide-azide was reduced and acylated with a 6-aminohexanoyl spacer. Elongation of the deprotected heptasaccharide using glycosyltransferases yielded a biantennary nonasaccharide with terminal galactose residues and two undecasaccharides terminating with alpha 2,6- or alpha 2,3-linked sialic acid. The free amino group of the spacer of these oligosaccharides was converted into an isothiocyanate. Its subsequent coupling to bovine serum albumin gave neoglycoproteins with a yield of 2.4-3.6 glycan chains per carrier molecule. This versatile synthetic pathway allows employment of a wide variety of complex-type glycans, which can be introduced to various test systems in vitro and in vivo to evaluate potential biomedical applications. Solid-phase assays with biotinylated sugar receptors revealed discriminatory binding properties of the three neoglycoproteins, especially for the mistletoe lectin. This direct assay system is preferable to the measurement of inhibitory capacities with respect to model ligands. Ligand type- and cell type-dependent quantitative differences in the binding properties of the probes were detected by FACScan analyses with a panel of tumor cell lines and by monitoring of staining in tissue sections for small cell and non-small-cell lung cancer and mesotheliomas. Biodistribution of iodinated neoglycoproteins in mice gave a prolonged presence of the sialylated probes in serum. Relative to the nonasaccharide, the uptake, especially of the iodinated neoglycoprotein with alpha 2,3-sialylated ligand chains, was clearly elevated in mice for kidneys and Ehrlich tumors. On the basis of the documented feasibility of these applications, it is concluded that the further elaboration of glycan chain variants by the described synthetic approach in combination with the given test panel is warranted to evaluate the potential of complex glycan chain-carrying neoglycoproteins for diagnostic and therapeutic purposes.

Animals↗
PubMedDate not supplied

Solid-phase synthesis of a combinatorial array of 1,3-bis(acylamino)-2-butanones, inhibitors of the cysteine proteases cathepsins K and L.

To more rapidly prepare members of the 1,3-bis(acylamino)-2-butanone class of cysteine protease inhibitors, a solid-phase synthesis was developed. 1-Azido-3-amino-2,2-dimethoxybutane (4), which has the two amino groups differentiated and the ketone protected as a a ketal, served as a surrogate for the 1,3-diamino-2-butanone core. Amine (4) was coupled to the BAL-resin-linked carboxylic acids derived from alpha-amino acid esters. Evaluation of a small combinatorial array by measuring inhibition constants (Ki,appS) against cathepsins K, L, and B provided some structure-activity relationship trends with respect to selectivity and potency. Novel, potent inhibitors of cathepsins K and L were identified.

Butanones↗
PubMedDate not supplied

The epidemiology of organophosphate poisoning in urban Zimbabwe from 1995 to 2000.

The objective of this study was to examine current organophosphate usage in Zimbabwe. A cross-sectional descriptive study was done to determine the trends in admissions for organophosphate poisonings in an urban Zimbabwe hospital from 1995 to 2000. Variables such as sex, age, season, geographic area, and intent were examined. In 183,569 records, 599 cases of organophosphate poisoning were found. Organophosphate poisonings increased by 320% over the six years. The male and female admissions' rates were similar (48% vs 52%); 82% of the patients were less than 31 years old. Suicide was the predominant reason for poisoning (74%). Of admissions of children under the age of 10, 62% were due to accidental ingestion. Mortality from organophosphate poisonings was 8.3% over the six years. Organophosphate poisoning is increasing rapidly. In the background of this alarming trend is the physical, mental, and social state of a Zimbabwean society wrought with hardships.

Admitting Department, Hospital↗
PubMedDate not supplied

Natural antipig xenoantibody is absent in neonatal human serum.

BACKGROUND: Discordant xenotransplantation represents an attractive alternative to allotransplantation in light of the current shortage of donor organs suitable for heart allotransplantation. Unfortunately, discordant xenotransplantation is still limited by hyperacute rejection, a process thought to be mediated by natural antixenodonor antibodies. On the basis of our previous findings that cytotoxic natural xenoantibodies are immunoglobulin M in nature and that natural immunoglobulin M xenoantibodies are barely detectable in neonatal baboon serum, we postulated that immunoglobulin M xenoantibodies may be absent from newborn human serum. METHODS: Neonatal human sera were obtained from the cord blood of normal term infants and pooled. Pooled adult human sera were used as a control. A whole cell enzyme-linked immunosorbent assay and a complement-mediated cytotoxicity assay were performed to determine the binding and cytotoxicity of these xenoantibodies to pig aortic endothelial cells and pig lymphocytes. RESULTS: Neonatal human sera did not show binding of immunoglobulin M xenoantibodies to pig aortic endothelial cells or lymphocytes. However, low level binding of immunoglobulin G xenoantibodies was detected to pig endothelial cells and lymphocytes. In contrast, adult human sera showed significant binding of both natural immunoglobulin M and G xenoantibodies to pig aortic endothelial cells and lymphocytes. In addition, adult human immunoglobulin M xenoantibodies bound with similar avidity to both cultured adult and neonatal pig aortic endothelial cells. Although neonatal human sera were not cytotoxic to target cells, adult sera were cytotoxic to both pig aortic endothelial cells and pig lymphocytes. Our findings indicate that neonatal human sera lack natural antipig immunoglobulin M xenoantibodies, and therefore, neonatal human serum is not cytotoxic to pig endothelial cells or lymphocytes. Like adult pig endothelial cells, neonatal pig endothelial cells may also express similar membrane xenoantigens recognized by natural immunoglobulin M xenoantibodies. CONCLUSIONS: The absence of cytotoxic natural immunoglobulin M xenoantibodies in the neonate suggests that discordant xenotransplantation may be feasible in the neonate.

Adult↗
PubMedDate not supplied

Are matrix-immobilized neoglycoproteins, plant and human lectins and carbohydrate--binding antibodies from human serum mediators of adhesion in vitro for carcinoma and lymphosarcoma cells?

Mediation of cell adhesion by defined molecules can be studied by their immobilization onto a nitrocellulose matrix and incubation with cells. In order to infer the capacity of deliberately selected protein-carbohydrate interactions to establish sugar-inhibitable cell adhesion, a panel of immobilized neoglycoproteins was employed for the murine lymphosarcoma lines RAW-117 with low (P) and high (H10) metastatic capacity, a human mammary carcinoma line (DU4475) and three human colon carcinoma lines (C205, SW480, SW620). Exhibiting an otherwise rather similar behavior relative to the line with low metastatic potential, the murine line RAW117-H10 bound strongly to the matrix with carboxyl group-bearing N-acetylneuraminic acid and glucuronic acid as well as rhamnose. Whereas the analysis of carbohydrate-mediated adhesion yielded comparable results for the three colon carcinoma lines, a markedly reduced number of adherent cells was counted for matrix-attached alpha- and beta-galactosyl, alpha-mannosyl and alpha-glucosyl moieties in the case of the mammary carcinoma line, raising evidence for cell lineage-dependent alterations of this property. From the carbohydrate-binding proteins, the plant lectin, concanavalin A and Viscum album agglutinin almost invariably served well as cell adhesion molecules. Appropriate cell surface sugar receptors, probed with neoglycoproteins, and glycoconjugates, probed with lectins, thus can contribute to adhesion in this model system. The immobilized human beta-galactoside-binding lectin (Mr 14kDa) caused adhesion of the murine lines and one colon carcinoma line (SW480). Neither C-reactive protein under conditions that induce its activity as lectin nor serum amyloid P component nor a lactose-binding immunoglobulin G fraction from human serum were reactive. However, cell adhesion to the alpha-galactoside-binding immunoglobulin G fraction of human serum was seen with the murine line of low metastatic capacity and the mammary carcinoma line. Cells of this line adhered also to the mannan-binding protein from human serum, supporting the view for its potential role in host defence against aberrantly glycosylated tumor cells.

Adenocarcinoma↗