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Biomedical subjects

Q Jiang

Publications and source records attributed to Q Jiang.

At least 127 records · Page 7Linked to original sources
PubMed1997

cDNA cloning and pattern of expression of an adult, female-specific chymotrypsin from Aedes aegypti midgut.

A cDNA for a midgut chymotrypsin, induced by a blood meal, has been cloned and sequenced from the mosquito Aedes aegypti. The 938 base sequence codes for a 268 amino acid protein, which contains an 18-residue signal peptide and a seven-residue activation peptide. The deduced amino acid sequence contains several features typical of chymotrypsin proteases, including the catalytic triad of serine proteases and the residues that determine the chymotrypsin substrate specificity pocket. The chymotrypsin mRNA, absent in larvae, pupae, males and newly emerged females, reaches detectable levels within 24 h post-emergence and attains a maximum level 3-7 days after emergence. Translation of the chymotrypsin mRNA is induced by feeding a protein meal, and there is a dramatic increase in midgut chymotrypsin enzymatic activity after feeding. Chymotrypsin activity remained high during protein digestion, but chymotrypsin protein levels and enzymatic activity were almost undetectable once digestion was completed, 48 h after feeding.

Aedes↗
PubMed1997

Intraphagosomal chlorination dynamics and yields determined using unique fluorescent bacterial mimics.

Fluorescein was covalently attached through a cystamine linker group to carboxy-derivatized polyacrylamide microspheres to generate phagocytosable particles containing fluorescent reporter groups. A unique feature of these beads is that the dye was recoverable in near-quantitative yield from intracellular environments by thiol reduction of the cystamine disulfide bond. Fluorescence microscopy indicated that individual neutrophils could bind as many as approximately 20 serum-opsonized beads, although no appreciable cellular association was observed for unopsonized beads. By using methyl viologen to quench external fluorescence, it was demonstrated that 70-90% of the neutrophil-associated fluorescein on opsonized beads was inaccessible to the medium. The particle-bound fluorescein underwent near-stoichiometric conversion to chlorinated derivatives when reacted with HOCl or the cell-free myeloperoxidase (MPO)-H2O2-Cl- system; products were identified by HPLC separation and electrospray ionization mass spectrometry of the recovered dye. Fluorescence changes accompanying phagocytosis were consistent with chlorination of the dye; fluorescence spectrometric and chemical trapping measurements indicated that intraphagosomal chlorination was far more extensive than extracellular chlorination. Yields of recovered chlorofluoresceins determined by HPLC indicated that sufficient HOCl had been produced intracellularly to kill entrapped bacteria. Fluorescein chlorination coincided approximately with phagocytosis and stimulated uptake of O2 by the cells. Demonstration that HOCl is produced within phagosomes in sufficient concentrations to kill bacteria on a time scale associated with death constitutes strong evidence in support of a primary role for HOCl in the microbicidal action of neutrophils.

Blood Bactericidal Activity↗
PubMed1997

The milk-ejection reflex in the peri-partum rat: effects of oestradiol and progesterone on basal milk-ejection frequency and the facilitatory response to central oxytocin.

Experiments were undertaken to examine the effects of ovarian steroids on the functional characteristics of the milk-ejection reflex during late pregnancy. Basal milk-ejection frequency and response to i.c.v. oxytocin (OT) were compared in different experimental groups, using intramammary pressure recordings obtained in suckling tests under urethane anaesthesia. Ovariectomy (OVX) on day 20 of pregnancy significantly (P < 0.05) increased milk-ejection frequency on day 22, compared with sham-OVXed animals. I.c.v. injection of 2.2 ng OT during suckling had no consistent effect on milk ejection in either of these groups. Pretreatment with oestradiol (5 micrograms per day, s.c.) or progesterone (5 mg per day, s.c.) both resulted in a fall in milk-ejection frequency compared to oil-treated OVXed controls. However, whereas oestradiol-treated OVXed rats showed a facilitatory response to i.c.v. OT, with a significant (P < 0.05) increase in milk-ejection frequency in the 20 min period after injection, progesterone-treated OVXed rats showed only a delayed decrease in milk-ejection frequency (significant at P < 0.05 between 20-40 min after injection). Oil-treated OVXed rats showed no significant response to i.c.v. OT at any stage. Electrophysiological recordings from supraoptic OT neurones confirmed that bursting activity was increased by i.c.v. injection of OT in oestradiol-treated, but not progesterone-treated rats. Further experiments with hysterectomized ovariectomized rats indicated that the difference in response to i.c.v. OT in oestradiol- vs progesterone-treated rats was not related to changes in the timing of birth induced steroid treatments. These findings demonstrate the ability of ovarian steroids to alter the characteristics of the milk-ejection reflex in the peri-partum rat. In particular, the rise in oestradiol and fall in progestesterone near term, may contribute to programming of the facilitary response to central OT in preparation for lactation.

Animals↗
PubMed1997

Classical and molecular genetics of the model legume Lotus japonicus.

The model legume Lotus japonicus was demonstrated to be amenable to classical and molecular genetic analysis, providing the basis for the genetic dissection of the plant processes underlying nodulation and nitrogen fixation. We have developed an efficient method for the sexual hybridization of L. japonicus and obtained F1 progeny derived from a cross of L. japonicus B-129-S9 Gifu x B-581 Funakura. Over half of the cross-pollinations resulted in fertile hybrid seed, which were confirmed morphologically and by single arbitrary primer DNA amplification polymorphisms using the DAF technique. Molecular and morphological markers segregated in true Mendelian fashion in a F2 population of 100 plants. Several DAF loci were linked using the MAPMAKER software to create the first molecular linkage groups of this model legume. The mapping population was advanced to generate a set of immortal recombinant inbred lines (F6; RILs), useful for sharing plant material fixed genetically at most genomic regions. Morphological loci for waved stem shape (Ssh), dark leaf color (Lco), and short flowering period (Fpe) were inherited as single dominant Mendelian loci. DAF markers were dominant and were detected between Gifu and Funakura at about one per primer, suggesting that the parents are closely related. One polymorphism (270G generated by single octomer primer 8.6m) was linked to a morphological locus controlling leaf coloration. The results demonstrate that (i) Lotus japonicus is amenable to diploid genetic analysis, (ii) morphological and molecular markers segregate in true diploid fashion, (iii) molecular polymorphisms can be obtained at a reasonable frequency between the related Gifu and Funakura lines, and iv) the possibility exists for map-based cloning, marker assisted selection and mapping of symbiotic mutations through a genetic and molecular map.

Base Sequence↗
PubMed1997

A new rat model of thrombotic focal cerebral ischemia.

We developed a fibrin-rich thrombotic focal cerebral ischemic model with reproducible and predictable infarct volume in rats. In male Wistar rats (n = 77), a thrombus was induced at the origin of the middle cerebral artery (MCA) by injection of thrombin via an intraluminal catheter placed in the intracranial segment of the internal carotid artery (ICA). Thrombus induction and consequent ischemic cell damage were examined by histopathological analysis and neurological deficit scoring, and by measuring changes in cerebral blood flow (CBF) using laser-Doppler flowmetery (LDF), perfusion-weighted imaging (PWI), and by diffusion weighted imaging (DWI). Histopathology revealed that a fibrin-rich thrombus localized to the origin of the right MCA. Regional cerebral blood flow (rCBF) in the right parietal cortex was reduced by 34-58% of preinjection levels after injection of thrombin in rats administered 30 U of thrombin (n = 10). Magnetic resonance imaging (MRI) showed a reduction in CBF and a hyperintensity DWI encompassing the territory supplied by the right MCA. The infarct volume in rats administered 80 U of thrombin was 31.29 +/- 12.9% of the contralateral hemisphere at 24 h (n = 13), and 34.7 +/- 16.4% of the contralateral hemisphere at 168 h (n = 6). Rats administered 30 U of thrombin exhibited a hemispheric infarct volume of 34.0 +/- 14.5% (n = 9) at 24 h and 29.7 +/- 13.9% (n = 8) at 168 h. In addition, thrombotic rats (n = 3) treated with recombinant tissue plasminogen activator (rt-PA) (10 mg/kg) 2 h after thrombosis showed that CBF rapidly returned towards preischemic values as measured by PWI. This model of thrombotic ischemia is relevant to thromboembolic stroke in humans and may be useful in documenting the safety and efficacy of thrombolytic intervention as well as for investigating therapies complementary to antithrombotic therapy.

Animals↗
PubMed1997

Corrected identity of isolates of Helicobacter pylori reference strain NCTC11637.

BACKGROUND: The reference strains NCTC11637 and NCTC11638 were among the very first Helicobacters ever cultured and have been distributed through national reference culture collections to researchers throughout the world. Because H. pylori is an extremely diverse species, such reference strains are invaluable as universal standards, provided that they are identified correctly. MATERIALS AND METHODS: H. pylori strains (previously called "NCTC11637") from three different sources and NCTC11638 were fingerprinted by the arbitrarily primed polymerase chain reaction (PCR) (also known as random amplified polymorphic DNA, or RAPD) method and further were characterized by NotI digestion and pulsed field gel electrophoresis of total genomic DNA (NotI-PFGE) and by restriction of PCR-amplified ureCD and flaA gene segments. RESULTS: RAPD tests of two "NCTC11637" strains from different sources (CCUG17874, UA1178) indicated that they were closely related or identical to NCTC11638. Given the diversity of H. pylori strains and the high sensitivity of the RAPD method, close matches in RAPD patterns from independent clinical isolates are not expected. In contrast, the version of "NCTC11637" from the American Type Culture Collection (ATCC43504) did not match NCTC11638 in RAPD fingerprint. Concordant results were obtained by NotI-PFGE and by restriction of PCR amplified gene segments. CONCLUSIONS: Two unrelated versions of the reference (type) H. pylori strain NCTC11637 are in general circulation and are distinguished easily by DNA fingerprinting. One matches another reference strain, NCTC11638, whereas the other is distinct from it, as expected of independent clinical isolates. Knowing which "NCTC11637" reference strain one has could be important, especially because H. pylori strains probably are diverse in phenotypic traits that are important for colonization or disease.

Bacterial Typing Techniques↗
PubMed1997

A mutational analysis of residues essential for ligand recognition at the human P2Y1 receptor.

We conducted a mutational analysis of residues potentially involved in the adenine nucleotide binding pocket of the human P2Y1 receptor. Mutated receptors were expressed in COS-7 cells with an epitope tag that permitted confirmation of expression in the plasma membrane, and agonist-promoted inositol phosphate accumulation was assessed as a measure of receptor activity. Residues in transmembrane helical domains (TMs) 3, 5, 6, and 7 predicted by molecular modeling to be involved in ligand recognition were replaced with alanine and, in some cases, by other amino acids. The potent P2Y1 receptor agonist 2-methylthio-ATP (2-MeSATP) had no activity in cells expressing the R128A, R310A, and S314A mutant receptors, and a markedly reduced potency of 2-MeSATP was observed with the K280A and Q307A mutants. These results suggest that residues on the exofacial side of TM3 and TM7 are critical determinants of the ATP binding pocket. In contrast, there was no change in the potency or maximal effect of 2-MeSATP with the S317A mutant receptor. Alanine replacement of F131, H132, Y136, F226, or H277 resulted in mutant receptors that exhibited a 7-18-fold reduction in potency compared with that observed with the wild-type receptor. These residues thus seem to subserve a less important modulatory role in ligand binding to the P2Y1 receptor. Because changes in the potency of 2-methylthio-ADP and 2-(hexylthio)-AMP paralleled the changes in potency of 2-MeSATP at these mutant receptors, the beta- and gamma-phosphates of the adenine nucleotides seem to be less important than the alpha-phosphate in ligand/P2Y1 receptor interactions. However, T221A and T222A mutant receptors exhibited much larger reductions in triphosphate (89- and 33-fold versus wild-type receptors, respectively) than in diphosphate or monophosphate potency. This result may be indicative of a greater role of these TM5 residues in gamma-phosphate recognition. Taken together, the results suggest that the adenosine and alpha-phosphate moieties of ATP bind to critical residues in TM3 and TM7 on the exofacial side of the human P2Y1 receptor.

Adenosine Monophosphate↗
PubMed1997

[Unrelated peripheral blood stem cell transplantation for a patient with acute myeloid leukemia].

OBJECTIVE: To carry out unrelated donor peripheral blood stem cell transplantation for treatment of hematological malignancies, and to observe the persistent hematopoietic reconstitution and transplantation related complications. METHODS: A 11-year-old boy with acute myeloid leukemia, who was in second CR, received peripheral blood stem cell transplantation from a unrelated healthy adult donor. The conditioning regimen consisted of FTBI (8Gy), cyclophosphamide (120 mg/kg) and Vp16 (30 mg/kg). The patient received 8. 3 x 10(8) mononuclear cells/kg, 1.079 x 10(8) CD34+ cells/kg and 1. 09 x 10(6) CFU-GM/kg. CsA and MTX were given for prophylaxis of aGVHD. RESULTS: Engraftment with allogeneic peripheral blood stem cells was rapid, ANC reached 1. 30 x 10(9)/L on day 10 post-transplantation, DNA D1S80 showed engraftment on day 23, and the blood type(AB) changed into the donor's (A) on day 120. The patient developed mild aGVHD (I degrees) on day 11 and mild cGVHD on day 143, which were controlled by methylprednisolone and prednisone, respectively. Ten months after transplantation, the patient's blood counts were normal. CONCLUSION: Unrelated donor peripheral blood stem cell can maintain persistent hematopoiesis.

Adult↗
PubMed1996

Strain differences in adrenal CYP2D16 expression in guinea pigs. Relationship to xenobiotic metabolism.

Experiments were done to determine the mechanisms responsible for differences in adrenal microsomal xenobiotic metabolism between Strain 13 and English Short-Hair (ESH) guinea pigs. The rates of adrenal xenobiotic metabolism (bufuralol 1'-hydroxylase, benzo[a]pyrene hydroxylase, benzphetamine N-demethylase) were 2-3 times greater in microsomes from the Strain 13 animals. In both strains, xenobiotic-metabolizing activities were far greater in the inner zone (zona reticularis) than in the outer zones (zona fasciculata and zona glomerulosa) of the adrenal cortex. Northern blot analyses of total adrenal RNA with a CYP2D16 cDNA as the probe revealed significantly greater amounts of CYP2D16 mRNA in the Strain 13 guinea pigs. In addition, SDS-PAGE and Western blotting of adrenal microsomes demonstrated higher concentrations of CYP2D16 protein in Strain 13 than in ESH animals. Expression of CYP2D16 was predominantly in the inner zone of the adrenal, coinciding with the major site of xenobiotic metabolism. The results demonstrated higher levels of expression of CYP2D16 in adrenal glands from Strain 13 than from ESH guinea pigs, which may account for the strain differences in adrenal xenobiotic metabolism. Strain 13 guinea pigs should serve as a good experimental model for further studies on the regulation of adrenal CYP2D16.

Adrenal Glands↗
PubMed1996

High-performance liquid chromatographic determination of midazolam in rat brain.

A high-performance liquid chromatography method for the determination of midazolam in rat brain is described. Midazolam and the internal standard halazepam were extracted with toluene and analyzed isocratically on a reversed-phase column with a mobile phase consisting of methanol, acetonitrile and potassium phosphate buffer. Detection was monitored by ultraviolet absorption at 240 nm. The standard curves were linear over the range of 25-350 ng midazolam per 50 mg brain tissue. The day-to-day coefficient of variation ranged from 1.7 to 6.9%. The limit of quantification was 80 ng/g brain tissue. The method is rapid, simple and reproducible for brain analysis.

Animals↗
PubMed1996

Site-directed mutagenesis of the human adenosine A2A receptor. Critical involvement of Glu13 in agonist recognition.

A glutamic acid residue in the first transmembrane domain of the human adenosine A2A receptor was mutated to glutamine. Radioligand binding studies on COS-7 cell membranes expressing either the wild-type or the mutant receptor revealed that the affinity of the prototypic agonist CGS21680 (2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine ) for the mutant receptor was 15-fold lower than for the wild-type receptor. This was confirmed in functional studies with intact cells. The EC50 values of CGS21680 for the stimulation of cAMP production differed in a similar way. Antagonists of various chemical structure were equally effective on both mutant and wild-type receptors, thus the mutation selectively diminishes agonist affinity. We propose an indirect perturbation of the binding site, perhaps through a proton transfer mechanism as suggested by molecular modelling.

Cyclic AMP↗
PubMed1996

Mechanism of carbon dioxide-catalyzed oxidation of tyrosine by peroxynitrite.

Peroxynitrite ion (ONO2-) reacted rapidly with CO2 to form a short-lived intermediate provisionally identified as the ONO2CO2- adduct. This adduct was more reactive in tyrosine oxidation than ONO2- itself and produced 3-nitrotyrosine and 3,3'-dityrosine as the major oxidation products. With tyrosine in excess, the rate of 3-nitrotyrosine formation was independent of the tyrosine concentration and was determined by the rate of formation of the ONO2CO2- adduct. The overall yield of oxidation products was also independent of the concentration of tyrosine and medium acidity; approximately 19% of the added ONO2- was converted to products under all reaction conditions. However, the 3-nitrotyrosine/3,3'-dityrosine product ratio depended upon the pH, tyrosine concentration, and absolute reaction rate. These data are in quantitative agreement with a reaction mechanism in which the one-electron oxidation of tyrosine by ONO2CO2- generates tyrosyl and NO2 radicals as intermediary species, but are inconsistent with mechanisms that invoke direct electrophilic attack on the tyrosine aromatic ring by the adduct. Based upon its reactivity characteristics, ONO2CO2- has a lifetime shorter than 3 ms and a redox potential in excess of 1 V, and oxidizes tyrosine with a bimolecular rate constant greater than 2 x 10(5) M-1 s-1. In comparison, in CO2-free solutions, oxidation of tyrosine by peroxynitrite was much slower and gave significantly lower yields (approximately 8%) of the same products. When tyrosine was the limiting reactant, 3,5-dinitrotyrosine was found among the reaction products of the CO2-catalyzed reaction, but this compound was not detected in the uncatalyzed reaction.

Carbon Dioxide↗
PubMed1996

Variability of gene order in different Helicobacter pylori strains contributes to genome diversity.

Considerable genomic microdiversity has been reported previously among Helicobacter pylori isolates. We have constructed genome maps of four unrelated H. pylori strains (NCTC11637, NCTC11639, UA802 and UA861) using pulsed-field gel electrophoresis (PFGE) with NotI and NruI, hybridization with extracted PFGE DNA fragments and probing with 17 gene probes. These strains of H. pylori were compared with a fifth unrelated H. pylori strain NCTC11638 mapped previously. Considerable diversity in gene arrangement was evident among the five H. pylori maps, and no consistent gene clustering was found. The association of only four genes, katA (catalase gene), vacA (vacuolating cytotoxin gene), hpaA (a putative adhesin gene), and pfr (bacterial ferritin gene) were generally conserved within approximately the same 25% of the genome; however, the order of these genes also varied. Our study demonstrates that macrodiversity, i.e. variability in gene order, in addition to microdiversity, is a characteristic of the H. pylori genome.

Chromosome Mapping↗
PubMed1996

Conservation and diversity of the Helicobacter pylori copper-transporting ATPase gene (copA) sequence among Helicobacter species and Campylobacter species detected by PCR and RFLP.

BACKGROUND: Helicobacter pylori is a causative pathogen of such human stomach diseases as chronic type B gastritis, ulcer, and possibly gastric carcinoma. As a cofactor in various redox enzymes and an essential trace metal required for the synthesis of metalloproteins, copper might play a role in the pathogenesis of H. pylori. A gene, copA, associated with copper transport, has been isolated from H. pylori UA802. In this study, conservation and diversity of this gene were analyzed among some Helicobacter and Campylobacter species. MATERIALS AND METHODS: Twenty-one clinical isolates and strains of helicobacters and campylobacters were used in this study. Methods including polymerase chain reaction (PCR) amplification, restriction fragment-length polymorphisms (RFLPs), and hybridization were employed to carry out this work. RESULTS: The copA gene was highly conserved in all the H. pylori isolates tested (Helicobacter nemestrinae and Helicobacter felis but not in Helicobacter mustelae and the Campylobacter species), whereas the sequence downstream of the copA appears to diverge among H. pylori isolates. In addition, two restriction patterns of the PCR-amplified copA fragments from seven H. pylori isolates and H. nemestrinae were identified, and the RFLP of H. nemestrinae was identical to that of one of the H. pylori isolate group. CONCLUSIONS: The adenosine triposphatase-derived copper-transporting mechanism is employed by various H. pylori strains, H. nemestrinae, H. felis, and perhaps by other Helicobacter species. The nucleotide mutations have risen in the copA gene. It appears that there is a genetic relatedness of the copA gene to H. pylori and H. nemestrinae.

Adenosine Triphosphatases↗
PubMed1996

Differential effects of adrenocorticotropin in vivo on cytochromes P4502D16 and P450c17 in the guinea pig adrenal cortex.

Studies were performed to compare the effects of ACTH treatment in vivo on cytochromes P4502D16 and P450c17 in the guinea pig adrenal cortex. In untreated animals, CYP2D16 protein and messenger RNA (mRNA) expression as well as xenobiotic-metabolizing activities (bufuralol 1'-hydroxylase, benzphetamine N-demethylase, and benzo(a)pyrene hydroxylase) were far greater in the inner (zona reticularis) than the outer (zona fasciculata plus zona glomerulosa) zones of the cortex. ACTH treatment for 3 or 7 days significantly decreased the rates of xenobiotic metabolism in both the inner and outer adrenal zones. Western and Northern blot analyses revealed that adrenal CYP2D16 protein and mRNA concentrations were significantly decreased by ACTH. In contrast to its inhibitory effects on CYP2D16, ACTH treatment increased steroid 17 alpha-hydroxylase activity in the adrenal inner zone, but did not affect outer zone activity. Microsomal CYP17 protein concentrations were not affected by ACTH despite increases in CYP17 mRNA levels in both zones. The results indicate that ACTH causes down-regulation of adrenal CYP2D16, probably at the transcriptional level. Thus, modulation of CYP2D16 by ACTH is opposite that for the steroidogenic P450 isozymes, suggesting unique regulatory mechanisms. In addition, the data suggest that posttranscriptional mechanisms contribute to ACTH regulation of 17 alpha-hydroxylase activity in the guinea pig adrenal cortex.

Adrenal Cortex↗
PubMed1996

Influence of human factors on performance of Chinese speech recognition systems.

Human factors affecting the performance of the speaker dependent isolated Chinese speech recognition system (SRS) were studied. The results showed that the training mode and dialect factors had significant influence upon recognition accuracy; speaker's psychological factor, cooperativeness and educational background had certain influence, while factors such as sex, age, and profession of the speaker had less influence on recognition performance. With the results taken into consideration, ways for improving performance of the speech recognition systems were explored from the point of view of man-machine integration.

Adolescent↗
PubMed1996

Characterization of multilocus lesions in human cells exposed to X radiation and radon.

Human TK6 lymphoblasts were exposed to X radiation or radon, and thymidine kinase negative (TK-/-) mutants were selected, isolated and harvested for analysis of structural changes in the TK gene. A large majority (82%) of the radon-induced mutants, 74% of the X-radiation-induced mutants and 45% of the spontaneous mutants lost the entire active TK allele. To analyze these mutants further we measured the loss of heterozygosity at several loci neighboring the TK locus on chromosome 17q. A greater proportion (61%) of the radon-induced mutants than X-radiation-induced or spontaneous mutants harbored the smaller lesions involving the TK allele alone or extending from the TK locus to one or both of the closest neighboring sequences tested. Further, 21% of the X-radiation-induced mutants but only 5% of the radon-induced mutants lost heterozygosity at the col1A1 locus, 31 Mb from the TK gene. These results are in agreement with a recent analysis of radon- and X-radiation-induced lesions inactivating the HPRT gene of TK6 cells, in which we reported that a lower percentage of radon- than X-radiation-induced mutants showed lesions extending to markers 800 kb or more from the HPRT gene on the X chromosome (Bao et al., Mutat. Res. 326, 1-13, 1995). In the present study, we observed that the percentage of slowly growing and very slowly growing TK-/- mutants was greater after treatment with radon than after treatment with X radiation, regardless of the type of lesion present. It is possible, therefore, that the radon-induced lesions are complex and/or less easily repaired, leading to slow growth in a large proportion of the surviving mutant cells.

B-Lymphocytes↗