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Biomedical subjects

X Q Liu

Publications and source records attributed to X Q Liu.

At least 19 recordsLinked to original sources
PubMed2005

Genetic and physical mapping of Pi36(t), a novel rice blast resistance gene located on rice chromosome 8.

Blast resistance in the indica cultivar (cv.) Q61 was inherited as a single dominant gene in two F2 populations, F2-1 and F2-2, derived from crosses between the donor cv. and two susceptible japonica cvs. Aichi Asahi and Lijiangxintuanheigu (LTH), respectively. To rapidly determine the chromosomal location of the resistance (R) gene detected in Q61, random amplified polymorphic DNA (RAPD) analysis was performed in the F2-1 population using bulked-segregant analysis (BSA) in combination with recessive-class analysis (RCA). One of the three linked markers identified, BA1126(550), was cloned and sequenced. The R gene locus was roughly mapped on rice chromosome 8 by comparison of the BA1126(550) sequence with rice sequences in the databases (chromosome landing). To confirm this finding, seven known markers, including four sequence-tagged-site (STS) markers and three simple-sequence repeat (SSR) markers flanking BA1126(550) on chromosome 8, were subjected to linkage analysis in the two F2 populations. The locus was mapped to a 5.8 cM interval bounded by RM5647 and RM8018 on the short arm of chromosome 8. This novel R gene is therefore tentatively designated as Pi36(t). For fine mapping of the Pi36(t) locus, five additional markers including one STS marker and four candidate resistance gene (CRG) markers were developed in the target region, based on the genomic sequence of the corresponding region of the reference japonica cv. Nipponbare. The Pi36(t) locus was finally localized to an interval of about 0.6 cM flanked by the markers RM5647 and CRG2, and co-segregated with the markers CRG3 and CRG4. To physically map this locus, the Pi36(t)-linked markers were mapped by electronic hybridization to bacterial artificial chromosome (BAC) or P1 artificial chromosome (PAC) clones of Nipponbare, and a contig map was constructed in silico through Pairwise BLAST analysis. The Pi36(t) locus was physically delimited to an interval of about 17.0 kb, based on the genomic sequence of Nipponbare.

Alleles↗
PubMed2005

Synthesis of magnetic chelator for high-capacity immobilized metal affinity adsorption of protein by cerium initiated graft polymerization.

A novel magnetic chelator with high adsorption capacity of protein by immobilized metal affinity adsorption was prepared by cerium (IV) initiated graft polymerization of tentacle-type polymer chains with iminodiacetic acid (IDA) chelating group on magnetic particles with hydroxyl groups. The micron-sized magnetic poly(vinyl acetate-divinylbenzene) (PVAc-DVB) particles were prepared by a modified suspension polymerization in the presence of oleic acid-coated magnetite nanoparticles and subsequently modified by ester exchange reaction to introduce functional hydroxyl groups. Bovine hemoglobin (BHb) was selected as a model protein to investigate the adsorption capacity of these magnetic particles. The magnetic particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), superconducting quantum interference device (SQUID) magnetometry, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray diffraction (XRD). The results showed that the magnetic particles had an average size of 5 microm and superparamagnetism with saturation magnetization of 20.0 emu/g at room temperature. The protein adsorption indicated that the graft polymerization of tentacle type polymer chains on the magnetic particles could produce magnetic adsorbents with high adsorption capacity (1428.21 mg/g) and low nonspecific adsorption of protein. The magnetic particles with grafted tentacle polymer chains have potential application in large-scale affinity separation of proteins.

Adsorption↗
PubMed2003

Epidemiology and cause of severe acute respiratory syndrome (SARS) in Guangdong, People's Republic of China, in February, 2003.

BACKGROUND: An epidemic of severe acute respiratory syndrome (SARS) has been associated with an outbreak of atypical pneumonia originating in Guangdong Province, People's Republic of China. We aimed to identify the causative agent in the Guangdong outbreak and describe the emergence and spread of the disease within the province. METHODS: We analysed epidemiological information and collected serum and nasopharyngeal aspirates from patients with SARS in Guangdong in mid-February, 2003. We did virus isolation, serological tests, and molecular assays to identify the causative agent. FINDINGS: SARS had been circulating in other cities of Guangdong Province for about 2 months before causing a major outbreak in Guangzhou, the province's capital. A novel coronavirus, SARS coronavirus (CoV), was isolated from specimens from three patients with SARS. Viral antigens were also directly detected in nasopharyngeal aspirates from these patients. 48 of 55 (87%) patients had antibodies to SARS CoV in their convalescent sera. Genetic analysis showed that the SARS CoV isolates from Guangzhou shared the same origin with those in other countries, and had a phylogenetic pathway that matched the spread of SARS to the other parts of the world. INTERPRETATION: SARS CoV is the infectious agent responsible for the epidemic outbreak of SARS in Guangdong. The virus isolated from patients in Guangdong is the prototype of the SARS CoV in other regions and countries.

China↗
PubMed2003

Molecular genetic analysis of glycogen storage disease type Ia in 26 Chinese patients.

Sequence analysis of 26 patients from Mainland China with glycogen storage disease type Ia revealed a high frequency of two mutations in the glucose-6-phosphatase gene. These mutations, 727G>T and R83H, were also found to be in linkage disequilibrium with a polymorphism at position 1176. These findings have implications for carrier detection and prenatal diagnosis of this disease in the Chinese population.

Asian People↗
PubMed2001

Apolipoprotein E fragments present in Alzheimer's disease brains induce neurofibrillary tangle-like intracellular inclusions in neurons.

Human apolipoprotein (apo) E4, a major risk factor for Alzheimer's disease (AD), occurs in amyloid plaques and neurofibrillary tangles (NFTs) in AD brains; however, its role in the pathogenesis of these lesions is unclear. Here we demonstrate that carboxyl-terminal-truncated forms of apoE, which occur in AD brains and cultured neurons, induce intracellular NFT-like inclusions in neurons. These cytosolic inclusions were composed of phosphorylated tau, phosphorylated neurofilaments of high molecular weight, and truncated apoE. Truncated apoE4, especially apoE4(Delta 272--299), induced inclusions in up to 75% of transfected neuronal cells, but not in transfected nonneuronal cells. ApoE4 was more susceptible to truncation than apoE3 and resulted in much greater intracellular inclusion formation. These results suggest that apoE4 preferentially undergoes intracellular processing, creating a bioactive fragment that interacts with cytoskeletal components and induces NFT-like inclusions containing phosphorylated tau and phosphorylated neurofilaments of high molecular weight in neurons.

Aged↗
PubMed2001

Aggregates and gel network structure of globin hydrolysates.

A gel with excellent functional properties was prepared successfully using the hydrolysates of globin. In the present study, the structures of intermediate aggregates and gel network were observed directly with an electronic microscope. It was shown clearly that the intermediate aggregates were in a thin rod shape with a length of 130--140 nm, which was in good accordance with the results of the light scattering obtained in a previous study. The diameter of intermediate aggregates was 4--5 nm. Each unit of the intermediate aggregate was composed of beta-chain and peptide beta-1 in a ratio of 1:1. Its molecular weight was 26922 Da, and it had a diameter of 4.1 nm. The thin rod-shaped aggregates were formed with units through the hydrophobic interaction. The length of intermediate aggregate was >30--33 times the diameter. Furthermore, the cross-linked structure formed by peptide alpha-1 and the thin rod-shaped aggregates was also confirmed by the photography of the electronic microscope. These results supported the model proposed in previous papers as proper to depict exactly the formation and structure of the gel network of globin hydrolysates.

Amino Acids↗
PubMed2001

Neoadjuvant chemotherapy in inoperable, locally advanced, and inflammatory breast carcinoma: a pilot study of MTT assay in vitro and outcome analysis of 10 patients.

Patients with inoperable, locally advanced, and inflammatory breast carcinoma (LAIBC), whether with supraclavicular lymph nodes (SLN) or not (stage IIIB and IV), usually carry an overall poor prognosis. The current treatment for these patients is by means of combined modality, including preoperative chemotherapy. This strategy has led to a substantial improvement in clinical response, making some patients operable, and even making breast conservative surgery possible. However, the long-term results still are not promising. The aim of this pilot study was to determine the efficacy of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro in directing chemotherapy (including preoperative adjuvant chemotherapy and postoperative adjuvant chemotherapy) for these patients. Between June 1994 and March 1997, 10 patients with inoperable LAIBC, whether with SLN or not, were enrolled. During the period of the combined therapy modalities, the neoadjuvant chemotherapy was adopted for three cycles according to the results of chemosensitivity in vitro by MTT assay. Then a modified radical or radical mastectomy was performed, which was followed by radiotherapy and further postoperative adjuvant chemotherapy with the same regimen as that of neoadjuvant chemotherapy. All patients had been followed up from the beginning of neoadjuvant chemotherapy to the end of October 1999. Two patients had clinical complete response (CRs), with one having pathologic CR in both breast tumor and axillary lymph node, and the other having pathologic CR in axillary lymph node. The other eight patients had partial response. By the time of analysis, six patients had been dead of relapse or progression. Among the four patients who were still alive, one had local relapse, one had distant metastatic disease, and the other two had no evident disease. By retrieving from MEDLINE before 1999, the authors learned that this is the first pilot study of neoadjuvant chemotherapy for inoperable LAIBC using MTT assay to predict the chemosensitivity in vitro. Compared with conventional chemotherapy, the clinical response and long-term results seem to be more encouraging.

Adenocarcinoma↗
PubMed2001

Application of selective implantation in Al0.5Ga0.5As/In0.25Ga0.75As/GaAs pseudomorphic single quantum wire structures.

A pseudomorphic Al0.5Ga0.5As/In0.25Ga0.75As/GaAs asymmetric quantum wire (QWR) structure was grown on GaAs V-grooved substrate by low pressure metal organic vapor phase epitaxy. The formation of crescent shaped QWRs at the bottom of the V-grooves was confirmed by both transmission electron microscopy and photoluminescence (PL) spectra. The temperature dependence of PL spectra demonstrated a fast decrease of the sidewall quantum well PL intensity with increasing temperature, which originates from relaxation of carriers from well to wire region. The self-aligned dual implantation technique was successfully used to selectively disable the adjacent quantum structures. Decrease of the PL intensity of QWR at 8 K was observed after selective implantation, which resulted from a decreased number of carriers relaxed from adjacent quantum structures.

Aluminum↗
PubMed2001

[Clinical study on analgesic mechanism of bitongxiao in treating neck pain due to cervical spondylitis].

OBJECTIVE: To study the analgesic mechanism of Bitongxiao (BTX, a Chinese herbal decoction) in treating neck pain due to cervical spondylitis (CS). METHODS: BTX and Jingfukang (JFK) granule were used to treat the treated and the control group separately in 102 CS cases. Plasma leucine enkephalin (LEK), substance P (SP) and prostaglandin E2 (PGE2) before and after treatment were assayed by radioimmunoassay (RIA). RESULTS: Twelve patients in the treated group were clinically cured, 36 markedly effectively, 3 effectively and 1 ineffectively, while in the control group they were 5, 33, 14 and 0 cases respectively. The cured and marked effective rate in the treated group was 92.3%, while that in the control group 72.0%. After treatment the pain score (VAS) of both groups were significantly reduced, but the reduction was higher in the treated group than that in the control. Before treatment, plasma LEK in all patients was abnormally low, but after treatment, it raised obviously more in the treated group than that in the control (P < 0.05). Plasma SP of both groups were obviously elevated, and PGE2 revealed unaltered after treatment. CONCLUSION: BTX has strong, fast-acting and long-lasting analgesic effect with no side-effects, it could elevate the lowered plasma LEK level in cervical spondylitis patients and increase plasma SP level. The analgesic mechanism of BTX might be associated with its effect on LEK, SP or other endorphins, directly acting on the pain modulation system.

Adult↗
PubMed2001

[A retrospective analysis of 8 cases with primary central nervous system lymphoma].

OBJECTIVE: To make an inquiry into clinical features, treatment, and prognosis of primary central nervous system lymphoma (PCNSL). METHOD: A retrospective analysis was carried out in a group of 8 patients confirmed diagnostic PCNSL by clinical findings and pathological examination. RESULTS: The common clinical manifestation of PCNSL consisted of increased intracranial pressure, seizures, focal neurologic deficits. Studies of cerebrospinal fluid revealed protein elevation in the most patients. Neuroradiological examinations with CT and MRI both showed solitary or multiple lesion located cerebral hemisphere, periventricular, basal ganglia, corpus callosum. Pathological examination showed B-cell malignant lymphoma. CONCLUSION: The patients with PCNSL usually did not show characteristic clinical manifestations or findings in imaging scanning. The brain biopsy pathological examination might be the only reliable method to confirm the diagnosis of the disease.

Adult↗
PubMed2000

Protein trans-splicing and cyclization by a naturally split intein from the dnaE gene of Synechocystis species PCC6803.

A naturally occurring split intein from the dnaE gene of Synechocystis sp. PCC6803 (Ssp DnaE intein) has been shown to mediate efficient in vivo and in vitro trans-splicing in a foreign protein context. A cis-splicing Ssp DnaE intein construct displayed splicing activity similar to the trans-splicing form, which suggests that the N- and C-terminal intein fragments have a high affinity interaction. An in vitro trans-splicing system was developed that used a bacterially expressed N-terminal fragment of the Ssp DnaE intein and either a bacterially expressed or chemically synthesized intein C-terminal fragment. Unlike artificially split inteins, the Ssp DnaE intein fragments could be reconstituted in vitro under native conditions to mediate splicing as well as peptide bond cleavage. This property allowed the development of an on-column trans-splicing system that permitted the facile separation of reactants and products. Furthermore, the trans-splicing activity of the Ssp DnaE intein was successfully applied to the cyclization of proteins in vivo. Also, the isolation of the unspliced precursor on chitin resin allowed the cyclization reaction to proceed in vitro. The Ssp DnaE intein thus represents a potentially important protein for in vivo and in vitro protein manipulation.

Base Sequence↗
PubMed2000

Epidemiological and nutritional research on prevention of cardiovascular disease in China.

Anthropological evidence suggests that regional differences in eating practices may be characterized by sub-ethnicity. Hakka is one sub-ethnicity who still retain a unique way of life in China. A field survey on diet and health among the Hakka people was undertaken in 1994. Approximately 200 participants were interviewed for their medical history, life-style and food habits. Blood pressure, body mass index, blood sample, 24 h urine and electrocardiogram were collected. The food samples taken from one tenth of the participants were analyzed for the ingredients in their daily meals. From this survey the prevalence of hypertension in Hakka was approximately 10 %. The sodium/potassium ratio was lower than that in Guangzhou and comparable with that in Okinawa, the island of longevity in Japan. For men, taurine level was found to be close to that in Mediterranean countries, where there is low mortality from cardiovascular diseases. For women, the taurine level was even higher, approximating that of Japanese women, who show the greatest longevity and lowest cardiac mortality worldwide. Less obesity was found in Hakka people than that in the US, Canada or Japan. These findings suggest that the following are the major reasons for these positive findings: the Hakka people maintain traditional food habits and maintain active awareness of their health; the major foods are rice, fish, vegetables and fruits; wide use of soybeans; extensive consumption of visceral organs which have rich source of trace elements. These eating practices and nutritional patterns may be beneficial factors for preventing atherosclerosis and hypertension.

Adult↗
PubMed2000

Crystallization and preliminary X-ray analyses of insect neurotoxins with analgesic effect from the scorpion Buthus martensii Karsch.

Three insect neurotoxins from the scorpion Buthus martensii Karsch, named BmK I1, BmK I4 and BmK I6, have been purified and crystallized. BmK I1 and BmK I4 show strong toxicity to insects, while BmK I6 is relatively weaker. They all exhibit an evident analgesic effect on mice; this is a novel biological function for scorpion insect toxins. Their crystals diffract to at least 3.5 (BmK I1), 2.8 (BmK I4), 2.8 (BmK I6 crystal form I) and 2.2 A (of BmK I6 crystal form II) resolution on an ordinary X-ray source. Crystals of BmK I1 belong to space group P6, with unit-cell parameters a = b = 66.2, c = 176.7 A. BmK I4 crystallized in the tetragonal space group I4, with unit-cell parameters a = b = 134.5, c = 60.6 A. BmK I6 has been crystallized in two forms: form I belongs to space group C2, with unit-cell parameters a = 46.5, b = 85.2, c = 32.6 A, beta = 110.5 degrees; form II belongs to space group R3, with the hexagonal unit-cell parameters a = b = 44.5, c = 164.7 A.

Amino Acid Sequence↗
PubMed2000

Protein-splicing intein: Genetic mobility, origin, and evolution.

Intein is the protein equivalent of intron and has been discovered in increasing numbers of organisms and host proteins. A self-splicing intein catalyzes its own removal from the host protein through a posttranslational process of protein splicing. A mobile intein displays a site-specific endonuclease activity that confers genetic mobility to the intein through intein homing. Recent findings of intein structure and the mechanism of protein splicing illuminated how inteins work and yielded clues regarding intein's origin, spread, and evolution. Inteins can evolve into new structures and new functions, such as split inteins that do trans-splicing. The structural basis of intein function needs to be identified for a full understanding of the origin and evolution of this marvelous genetic element.

DNA-Directed DNA Polymerase↗
PubMed2000

[Induction of polyploid in the Pacific abalone by caffeine-heat shock treatments].

Polyploid of Pacific abalone, Haliotis discus hannai Ino, was induced by blocking Polar body I with caffeine-heat shock treatments. Fertilized eggs were treated with caffeine concentrations at: 2.5 mmol/L, 5 mmol/L and 10 mmol/L; heat shock temperatures at 24 degrees C, 26 degrees C, 28 degrees C, lasting for 10 min to 30 min, total 5 periods of time, beginning at 10 min post-fertilization. Both fertilizing and incubating at 21 degrees C sea water. The results of studies showed that the effective procedure for inducing triploid appeared to be 5 mmol/L and 10 mmol/L Caffeine concentration, heat shock temperature 26 degrees C, duration 10 min to 15 min, all beginning at 10 min after insemination. The percentage of triploid was 64.6%-77.8%, Comprehensive efficiency index of polyploid induction was 0.57-0.61. Under the condition of 5 mmol/L caffeine concentration and the temperature 26 degrees C for 30 min duration at 10 min post-fertilization, 2.8%-3.6% tetraploid embryos could be produced.

Animals↗
PubMed2000

Enzyme kinetics and inhibition of nimodipine metabolism in human liver microsomes.

AIM: To study the enzyme kinetics of nimodipine (NDP) metabolism and the effects of selective cytochrome P-450 (CYP-450) inhibitors on the metabolism of NDP in human liver microsomes in vitro. METHODS: Microsomes from six individual human liver specimens were used to perform enzyme kinetic studies and the kinetic parameters were estimated by Eadie-Hofstee equation. Various selective CYP-450 inhibitors were used to investigate their effects on the metabolism of NDP and the principal CYP-450 isoform involved in dehydrogenation of dihydropyridine ring of NDP in human liver microsomes. RESULTS: There was an important intersubject variability in NDP metabolism in human liver microsomes. For NDP dehydrogenase activity, the Km value was (36 +/- 11) mumol and the Vm value was (17 +/- 7) mumol.g-1.min-1. The dehydrogenation of dihydropyridine ring of NDP was competitively inhibited by ketoconazole (Ket) and troleandomycin (TAO), and the Ki values for Ket and TAO were 0.59 and 122.2 mumol, respectively. Phenacetin (Pnt), quinidine (Qui), diethyldithiocarbamate (DDC), sulfaphenazole (Sul), and tranylcypromine (Tra) had a little or no inhibitory effects on the dehydrogenation of NDP. CONCLUSION: The intersubject variability of NDP pharmacokinetics was attributed to the metabolic polymorphism of NDP in liver. Cytochrome P-4503A (CYP3A) is involved in the dehydrogenation of dihydropyridine ring of NDP.

Calcium Channel Blockers↗
PubMed1999

Crystal structures of two alpha-like scorpion toxins: non-proline cis peptide bonds and implications for new binding site selectivity on the sodium channel.

The crystal structures of two group III alpha-like toxins from the scorpion Buthus martensii Karsch, BmK M1 and BmK M4, were determined at 1.7 A and 1.3 A resolution and refined to R factors of 0.169 and 0.166, respectively. The first high-resolution structures of the alpha-like scorpion toxin show some striking features compared with structures of the "classical" alpha-toxin. Firstly, a non-proline cis peptide bond between residues 9 and 10 unusually occurs in the five-member reverse turn 8-12. Secondly, the cis peptide 9-10 mediates the spatial relationship between the turn 8-12 and the C-terminal stretch 58-64 through a pair of main-chain hydrogen bonds between residues 10 and 64 to form a unique tertiary arrangement which features the special orientation of the terminal residues 62-64. Finally, in consequence of the peculiar orientation of the C-terminal residues, the functional groups of Arg58, which are crucial for the toxin-receptor interaction, are exposed and accessible in BmK M1 and M4 rather than buried as in the classical alpha-toxins. Sequence alignment and characteristics analysis suggested that the above structural features observed in BmK M1 and M4 occur in all group III alpha-like toxins. Recently, some group III alpha-like toxins were demonstrated to occupy a receptor site different from the classical alpha-toxin. Therefore, the distinct structural features of BmK M1 and M4 presented here may provide the structural basis for the newly recognized toxin-receptor binding site selectivity. Besides, the non-proline cis peptide bonds found in these two structures play a role in the formation of the structural characteristics and in keeping accurate positions of the functionally crucial residues. This manifested a way to achieve high levels of molecular specificity and atomic precision through the strained backbone geometry.

Amino Acid Sequence↗