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Biomedical subjects

X H Yang

Publications and source records attributed to X H Yang.

At least 37 records · Page 2Linked to original sources
PubMed1993

Regulation of central muscarinic receptors after cholinesterase inhibition: effect of clonidine.

In rats, the injection of soman (70 micrograms/kg, SC) resulted in a 90% inhibition of the cholinesterase (ChE) activities in three brain regions. The density (Bmax) for muscarinic acetylcholine receptors (mAChRs) following a single injection of soman was significantly reduced at 2 h after injection in the cortex and hindbrain. Bmax values, however, returned to baseline within 24 h. Subacute (repeated injection every 15 min) treatment with a sublethal dose of soman over 2 h also decreased the density of mAChRs. In both cases the density of mAChRs was reduced by about 15% for the cortex and 17% for the hindbrain (the midbrain was also reduced by 18% for subacute injections). Chronic administration (once daily for 7 days) of soman (20 micrograms/kg, SC) produced maximal inhibition of ChE activity but did not significantly downregulate mAChRs. Clonidine pretreatment reversed the soman-induced mAChR downregulation in cortex and hindbrain produced by acute soman administration. Thus, marked reduction in the levels of brain ChE is not the only factor involved in the production of mAChR downregulation to cholinesterase inhibitors.

Animals↗
PubMed1993

Role of Campylobacter jejuni flagella as colonization factors for three-day-old chicks: analysis with flagellar mutants.

Campylobacter jejuni, an important cause of human gastrointestinal infection, is a major food-borne pathogen in the United States and worldwide. Since poultry becomes colonized and/or contaminated during the early stages of production and is a major food-borne source for this organism, we studied the role of C. jejuni flagella on the ability of the bacterium to colonize the chicken gastrointestinal tract. Three-day-old chicks were orally challenged with a motile wild-type strain of C. jejuni IN9 or with flagellar mutants created from IN9 by disrupting the flagellin genes with a kanamycin resistance cassette by using shuttle mutagenesis (A. Labigne-Roussel, P. Courcoux, and L. Tompkins, J. Bacteriol. 170:1704-1708, 1988). One mutant, IN9-N3, lacked flagella and was nonmotile. The other, IN9-N7, produced a truncated flagellum and was partially motile. Three-day-old chicks were orally challenged with different doses of the wild-type strain and the two mutants. At challenge doses ranging from 3.0 x 10(4) to 6.6 x 10(8) CFU per chick, only the fully motile, wild-type strain colonized the chick ceca. Our results show that intact and motile flagella are important colonization factors for C. jejuni in chicks.

Animals↗
PubMed1992

Local immune responses to the Campylobacter flagellin in acute Campylobacter gastrointestinal infection.

Intestinal immunoglobulin A (IgA) anti-campylobacter flagellin antibodies were measured by an enzyme-linked immunosorbent assay in patients with and without campylobacter infections. The level of fecal IgA antiflagellin antibodies was significantly higher in patients than in controls, but only 12 of 29 patients (41.4%) with a campylobacter infection had detectable IgA antibodies against flagellin (optical density, greater than or equal to 0.100). Further testing of fecal IgA antibodies from 10 patients with homologous and heterologous purified flagellins showed strain specificity in 1 patient. Cross-reactivity of fecal IgA antibodies with heterologous flagellins did not correlate with the Lior serotype of the isolate.

Antibodies, Bacterial↗
PubMed1992

[Transurethral microwave radiation for bladder neoplasm].

42 patients with bladder neoplasm were treated effectively by transurethral microwave radiation in our hospital from March, 1990 to October 1991. No serious complication was found after this treatment and its long-term result was better than others. The principle of this method is to use the biological availability of microwave to heat the neoplasm and to evoke the cellular immunity system to kill tumor cells, because tumor cells is more likely to be killed than normal tissue cell by heat. Generally, tumor cells would be killed when the temperature is higher than 42 degrees C. The protection against microwave during the treatment was also discussed.

Adult↗
PubMed1991

Two Drosophila receptor-like tyrosine phosphatase genes are expressed in a subset of developing axons and pioneer neurons in the embryonic CNS.

Two Drosophila receptor-like tyrosine phosphatase genes, DPTP99A and DPTP10D, were characterized. Protein products of these genes show distinct expression patterns specific to subsets of developing CNS axons. DPTP99A expression coincides with the onset of axonogenesis and is expressed in several pioneer neurons, including aCC and RP2, which pioneer the intersegmental nerve; its proteins are transiently expressed in the intersegmental and segmental nerves, arguing for a role in the establishment of these nerves. Both genes produce complex sets of transcripts, owing to the alternative utilization of exons and polyadenylation sites. Each gene produces alternative protein forms, which differ in their C-terminal tails. The deduced proteins possess extracellular FN-III repeats and intracellular PTPase domain(s). We discuss the implications of these results and the role of protein tyrosine dephosphorylation in axon outgrowth and guidance.

Amino Acid Sequence↗
PubMed1991

Repertoire diversity of antibody response to bacterial antigens in aged mice. II. Phosphorylcholine-antibody in young and aged mice differ in both VH/VL gene repertoire and in specificity.

Aging of mice is accompanied by both quantitative and qualitative changes in antibody responses to phosphorylcholine (PC), an immunodominant epitope of Streptococcus pneumoniae R36a strain (Pn). In order to study these changes at the molecular level, we generated PC-specific hybridomas from young (3 to 4 mo) and aged (20 to 24 mo) mice of different strains after primary immunization with S. pneumoniae R36a strain. These mAb were tested for Ig VH and VL gene family utilization, idiotopic repertoire, and cross-reactivity with unrelated Ag. Hybridomas from young mice (BALB/c, C57BL/6, and D1.LP) uniformly expressed the VH-S107 and V kappa-22 genes as well as most idiotopes of the T15 family, which were identified with different anti-T15 mAb. In contrast, the PC-reactive mAb from aged mice were quite heterogeneous: only 2 out of 13 utilized VHS107, 1 of 13 used VH7183, and 3 of 13 used VHJ558 gene family. Moreover, none of these mAb used L chain encoded by V kappa 22(0/13), but surprisingly they frequently expressed some of the T15 idiotope. In addition, the PC-binding mAb from aged mice showed broad cross-reactivity with various mouse and foreign proteins, whereas the mAb from young mice did not. These results demonstrate the genetic shift in antibody response of aging mice to PC, which is accompanied by a change in the antibody specificity. Interestingly, the qualitative repertoire change appears to be unrelated to the magnitude of antibody response, for the aged BALB/c mice maintain a very high reactivity to PC.

Aging↗
PubMed1991

Two closely linked Drosophila POU domain genes are expressed in neuroblasts and sensory elements.

We have characterized two Drosophila POU genes designated dPOU-19 and dPOU-28. These genes are transcribed as 3.1- and 2.2-kilobase mRNAs, respectively, which accumulate maximally during the first 12 hr of embryogenesis. The mRNAs encode 601- and 475-amino acid deduced proteins; their POU domains are most related to those of the human OCT1 and OCT2. Both genes give similar nervous system expression patterns and map to an indistinguishable site at 33F on the cytological map. Transcription of the genes is first observed in the cellular blastoderm. In the course of embryonic development, expression is observed in the neuroectoderm, with subsets of neuroblasts in the procephalic and germband central nervous system as well as a subset of peripheral nervous system elements. The expression patterns of the two POU genes suggest a possible functional role for these putative transcription factors in neurogenesis and neurospecification.

Amino Acid Sequence↗
PubMed1991

Enhancement of interleukin 2 production in human and Gibbon T cells after in vitro treatment with lithium.

The effect of trace elements lithium, selenium, and zinc on interleukin 2 (IL-2) production by peripheral blood mononuclear cells (PBMC), MLA144, and Jurkat cell lines has been studied. Lithium markedly enhanced IL-2 production by MLA144 and PBMC, but not by Jurkat. Selenium could only enhance IL-2 production by MLA144, whereas in none of these three systems was IL-2 production altered by zinc. The enhancing effect of lithium on IL-2 production showed some differences from that of tetradecanoylphorbol acetate (TPA) in the following aspects: (i) TPA could reverse the inhibitory effect of anti-CD2 monoclonal antibody on IL-2 production, whereas lithium could not; and (ii) lithium was unable to synergistically induce IL-2 production with anti-CD3 monoclonal antibody as TPA did. The effect of lithium on IL-2 production was in the early phase of lymphocyte activation. The addition of cholera toxin or theophylline to phytohemagglutinin-stimulated PBMC culture suppressed IL-2 production. However, IL-2 production could be restored by lithium. There was a corresponding increase in cAMP in cholera toxin or theophylline-treated PBMC, which could be reversed by lithium. Therefore, lithium restores IL-2 production via a decrease in cAMP.

Animals↗
PubMed1990

Infection of adult Syrian hamsters with flagellar variants of Campylobacter jejuni.

Two variants of Campylobacter jejuni IN1 differing in the expression of flagella, IN1 (Fla+ Mot+, wild type) and IN1-NM (Fla- Mot-), were tested for their ability to establish infection in adult hamsters. Animals were challenged intracecally with 2 X 10(9) to 5 X 10(10) CFU and monitored for evidence of infection. None of the challenged animals developed illness. There was a significant difference, however, in the ability of IN1 to infect hamsters (35 of 43) compared with that of IN1-NM (1 of 42) (P less than 0.01). Additionally, eight animals challenged with IN1-NM excreted only the campylobacters of Fla+ phenotype, which were shown to be identical with the parental Fla+ Mot+ type. Both groups of animals developed serum immunoglobulin G antibodies to outer membrane proteins of IN1 as measured by an enzyme-linked immunosorbent assay; however, only animals that excreted Fla+ organisms developed antiflagellin antibodies. In vitro reversibility from Fla+ to Fla- occurred with a frequency of 9.2 X 10(-6) per cell per generation; however, reversion from Fla- to Fla+ could not be detected in vitro. Further characterization of IN1-NM showed that it produced a cytoplasmic 62K flagellin subunit protein, but this protein lacked six epitopes detected in IN1 and also differed in its two-dimensional gel electrophoresis pattern. The results of these studies support the concept that an intact flagellum is necessary for intestinal infection with C. jejuni and that this model may be useful for studying the immune response to C. jejuni.

Animals↗
PubMed1990

[Protective effect of the antioxidants selenium, vitamin E, and superoxide dismutase on cultured human endothelial cells (ECs) injured by lipid peroxidation].

Lipid peroxidation was induced in cultured human ECs with cumene hydroxide and the protective effect of antioxidants (selenium, vitamin E and SOD) on endothelial cell injury by lipid peroxidation was investigated. The results showed that after administration of antioxidants (Se, Vit E and SOD), concentration of LPO in ECs induced by cumene hydroperoxide was reduced markedly while 6-Keto-PGF1 alpha content in the medium was increased and cell injury was alleviated. These results indicate that through the protective effect on ECs against lipid peroxidation, antioxidants (Se, Vit E and SOD) might play an important role in retarding the process of atherogenesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Antinociceptive effect of spinal cholinergic stimulation: interaction with substance P.

Activation of central muscarinic receptors results in an antinociceptive response in experimental animals. Employing intrathecal (i.t.) injection and radiant heat applied to a rat's tail as the experimental paradigm, a spinally-mediated antinociceptive response was obtained following injection of cholinergic agonists. Since "cholinergic' analgesia is mediated independently of the opiate system, the possibility was considered that this response was mediated through inhibition of the local release of substance P. Rats were prepared with indwelling i.t. catheters which terminated in the L2-L3 region of the spinal cord. I.t. injection of carbachol (0.05-5 micrograms) or neostigmine (1-10 micrograms), but not nicotine (0.5-10 micrograms) produced dose-related increases in tail flick latencies. Pretreatment with i.t. injection of atropine or hemicholinium-3 significantly inhibited the antinociceptive response to neostigmine. Spinal substance P levels were measured 30 min following 0.5 micrograms carbachol. Levels in the dorsal horn were reduced by 30% compared with saline controls. Levels in the ventral horn were unchanged by carbachol. These results support the role of endogenous spinal acetylcholine in pain modification and suggest an interaction with substance P neurons of the dorsal spinal cord.

Acetylcholine↗
PubMed1989

Human antibody response to Campylobacter jejuni flagellin protein and a synthetic N-terminal flagellin peptide.

We measured isotype-specific human antibodies directed against Campylobacter jejuni native flagellin and a synthetic peptide derived from the N-terminal amino acid sequence of the protein by using a microdilution enzyme-linked immunosorbent assay (ELISA). Serum samples from patients with gastrointestinal infection caused by C. jejuni (n = 20) and control samples (number from normal subjects = 20; number from patients with diarrhea other than campylobacter = 20) were tested in this assay. Serum specimens from patients with campylobacter infection showed statistically significant higher isotype-specific antiflagellin antibody titers than control samples did. Detection of immunoglobulin G (IgG) antibodies was less specific (70%) than detection of either IgA or IgM antibodies in infected patients (95%). The sensitivity of testing for any of the isotypes ranged from 64 to 100% in acute-phase serum specimens and 85 to 95% in convalescent-phase serum specimens. An ELISA with an N-terminal synthetic peptide derived from the flagellin protein as antigen was not sensitive (60%) for detecting campylobacter infection but was very specific (97.5%). In conclusion, detection of serum IgA or IgM against C. jejuni flagellin may be a useful marker of infection. Although the N-terminal synthetic peptide was antigenic in a few patients with infection and showed good specificity in the ELISA, additional amino acid sequences with better sensitivity for detecting infection need to be identified.

Amino Acid Sequence↗
PubMed1989

[Effects of the preparation of xiao long ling on experimental prostatic hyperplasia in mice].

The results of the experiments indicate that the prostatic hyperplasia caused by Testosteroni Propionatis in mice, cotton oil-induced local swollen ears of mice and the proliferation of granuloma produced by subcutaneous implantation of cotton pill in rats are inhibited significantly by the preparation of Xiao Long Ling. Xiao Long Ling depresses the increase of vascular permeability induced by a variety of inflammatory media such as histamine, 5-HT and PGE. Xiao Long Ling is found capable of inhibiting the platelet aggregation induced by ADP as well as depolymerizing the aggregated platelets.

Animals↗
PubMed1988

Protonmotive Q cycle pathway of electron transfer and energy transduction in the three-subunit ubiquinol-cytochrome c oxidoreductase complex of Paracoccus denitrificans.

Ubiquinol-cytochrome c oxidoreductase (cytochrome bc1) complex from Paracoccus denitrificans consists of only three polypeptide subunits (Yang, X., and Trumpower, B. L. (1986) J. Biol. Chem. 261, 12282-12289), whereas the analogous complexes of eukaryotic mitochondria consist of nine or more polypeptides (Schagger, H., Link, T. A., Engel, W. D., and von Jagow, G. (1986) Methods Enzymol. 126, 224-237). Using the purified three-subunit Paracoccus complex we have tested whether this simple cytochrome bc1 complex has the same electron transfer pathway and proton translocation activity as the bc1 complexes of mitochondria. Under presteady state conditions, the effects of inhibitors on reduction of cytochromes b and c1 by quinol and oxidant-induced reduction of cytochrome b indicate a cyclic electron transfer pathway and two routes of cytochrome b reduction in the three-subunit Paracoccus cytochrome bc1 complex. A novel method was developed to incorporate the cytochrome bc1 complex into liposomes with the detergent dodecyl maltoside. The enzyme reconstituted into liposomes translocated protons with an H+/2e value of 3.9. Carbonyl cyanide m-chlorophenylhydrazone eliminated proton translocation, while permitting the scalar release of protons from quinol, and thus reduced the H+/2e ratio to 2. These values agree with the predicted stoichiometries for proton translocation by a protonmotive Q cycle pathway. No inhibition of proton translocation by N',N'-dicyclohexylcarbodiimide was detected when the Paracoccus cytochrome bc1 complex was incubated with N',N'-dicyclohexylcarbodiimide before or after reconstitution into liposomes. Electron transfer in the three-subunit complex thus appears to occur by a protonmotive Q cycle pathway identical to that in mitochondrial cytochrome bc1 complexes. Only three polypeptides, cytochromes b, c1, and the Rieske iron-sulfur protein, are required for respiration and energy transduction in the cytochrome bc1 complex. The function of the supernumerary polypeptides in mitochondrial bc1 complexes is thus unclear.

Anions↗
PubMed1987

Identification of a stable ubisemiquinone and characterization of the effects of ubiquinone oxidation-reduction status on the Rieske iron-sulfur protein in the three-subunit ubiquinol-cytochrome c oxidoreductase complex of Paracoccus denitrificans.

The ubiquinol-cytochrome c oxidoreductase (cytochrome bc1) complex from Paracoccus denitrificans exhibits a thermodynamically stable ubisemiquinone radical detectable by EPR spectroscopy. The radical is centered at g = 2.004, is sensitive to antimycin, and has a midpoint potential at pH 8.5 of +42 mV. These properties are very similar to those of the stable ubisemiquinone (Qi) previously characterized in the cytochrome bc1 complexes of mitochondria. The micro-environment of the Rieske iron-sulfur cluster in the Paracoccus cytochrome bc1 complex changes in parallel with the redox state of the ubiquinone pool. This change is manifested as shifts in the gx, gy, and gz values of the iron-sulfur cluster EPR signal from 1.80, 1.89, and 2.02 to 1.76, 1.90, and 2.03, respectively, as ubiquinone is reduced to ubiquinol. The spectral shift is accompanied by a broadening of the signal and follows a two electron reduction curve, with a midpoint potential at pH 8.5 of +30 mV. A hydroxy analogue of ubiquinone, UHDBT, which inhibits respiration in the cytochrome bc1 complex, shifts the gx, gy, and gz values of the iron-sulfur cluster EPR signal to 1.78, 1.89, and 2.03, respectively, and raises the midpoint potential of the iron-sulfur cluster at pH 7.5 from +265 to +320 mV. These changes in the micro-environment of the Paracoccus Rieske iron-sulfur cluster are like those elicited in mitochondria. These results indicate that the cytochrome bc1 complex of P. denitrificans has a binding site for ubisemiquinone and that this site confers properties on the bound ubisemiquinone similar to those in mitochondria. In addition, the line shape of the Rieske iron-sulfur cluster changes in response to the oxidation-reduction status of ubiquinone, and the midpoint of the iron-sulfur cluster increases in the presence of a hydroxyquinone analogue of ubiquinone. The latter results are also similar to those observed in the mitochondrial cytochrome bc1 complex. However, unlike the mitochondrial complexes, which contain eight to 11 polypeptides and are thought to contain distinct quinone binding proteins, the Paracoccus cytochrome bc1 complex contains only three polypeptide subunits, cytochromes b, c1, and iron-sulfur protein. The ubisemiquinone binding site and the site at which ubiquinone and/or ubiquinol bind to affect the Rieske iron-sulfur cluster in Paracoccus thus exist in the absence of any distinct quinone binding proteins and must be composed of domains contributed by the cytochromes and/or iron-sulfur protein.

Coenzymes↗