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Biomedical subjects

X L Li

Publications and source records attributed to X L Li.

At least 19 recordsLinked to original sources
PubMed2003

Influence of early stages of arbuscular mycorrhiza on uptake of zinc and phosphorus by red clover from a low-phosphorus soil amended with zinc and phosphorus.

In a pot experiment, red clover (Trifolium pratense) was grown in sterilized Zn-amended low available P soil (0, 50 or 400 mg Zn kg(-1)) with or without 100 mg kg(-1) added P and with or without inoculation with the arbuscular mycorrhizal (AM) fungus G. mosseae. When the plants were harvested after 40 days, AM colonization of the roots was still at an early stage, with only 14-38% of total root length colonized on average. AM colonization was highest in low-P soil, and was lowest in soil amended with 400 mg Zn kg(-1). Shoot yields were highest in AM plants with added P, but root yields were unaffected by AM inoculation. Shoot and root yields were higher with 100 mg added P kg(-1) soil, but lower with 400 mg Zn kg(-1) than 50 mg Zn kg(-1) or controls unamended with Zn. Shoot and root P concentrations were seldom higher in AM plants, but shoot P offtakes were higher in AM plants with added P. Concentrations of Zn and Cu were much higher in the roots than in the shoots. Shoot and root Zn and shoot Cu were lower, but root Cu was higher, in AM plants. Soil residual pH after plant growth was higher in AM treatments, and residual total Zn was also higher, indicating lower Zn uptake by AM plants. Soil solution pH was higher in AM treatments, and soil solution Zn was lower in the presence of mycorrhiza. The results are discussed in terms of AM protection of the plants against excessive shoot Zn uptake.

Copper↗
PubMed2003

The role of arbuscular mycorrhiza in zinc uptake by red clover growing in a calcareous soil spiked with various quantities of zinc.

Three pot experiments were conducted to investigate the role of arbuscular mycorrhiza (AM) in Zn uptake by red clover. Plants inoculated with Glomus mosseae and uninoculated controls were grown in a sterile calcareous soil in 'Plexiglas' (Acrylic) containers with two nylon net partitions (30 microm mesh) to separate the central root zone from the two outer hyphal zones. The effects of mycorrhiza on plant growth and Zn uptake changed dramatically with increasing Zn addition level (range 0-1200 mg kg(-1)) in the root zone. With Zn addition levels <300 mg kg(-1), added Zn did not affect plant yield and above the critical level plant yield gradually decreased but was always higher for mycorrhizal than for controls. Below the critical Zn application rate (50 mg kg(-1)), Zn uptake was enhanced while above this level Zn translocation to the shoots decreased. At all Zn addition levels, mycorrhizal colonization increased Zn absorption and accumulation in the roots, and this may help to explain the alleviation of Zn toxicity at high Zn application rates. As expected, AM colonization enhanced P nutrition and hence yield at all added Zn levels studied. Efforts were made to obtain direct evidence for hyphal contribution to Zn uptake by applying both Zn to the hyphal growth zone and additional P to the root zone to avoid the 'growth dilution effect'. The data demonstrate that mycorrhizal hyphae could absorb Zn directly from the soil and then transfer it to the plant roots. The hyphal contribution to Zn uptake by the host plant reached its maximum value at the Zn addition level of 50 mg kg(-1), in which Zn uptake via the extramatrical hyphae comprised 22% of total uptake, thus confirming the critical Zn application level found previously.

Hyphae↗
PubMed2003

Growth and nutrient uptake of arbuscular mycorrhizal maize in different depths of soil overlying coal fly ash.

Application of topsoil over phytotoxic mine wastes is often practised to establish perennial plant communities on minespoil areas. In China, population pressure encourages attempts to remediate such areas by growing arable crop plants, but efforts to establish agricultural crops often fail. We report an outdoor pot experiment that compared the effects of two arbuscular mycorrhizal (AM) fungi, Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe and G. versiforme (Karsten) Berch, on the growth and nutrient uptake of maize (Zea mays L.) grown in different depths of soil layer overlying coal fly ash. Colonization by both AM fungi increased plant growth compared with non-mycorrhizal controls, with G. mosseae giving higher yields of maize than G. versiforme at the same depths of soil. Increasing soil depth led to increased plant yields. Mycorrhizal plants absorbed more nutrients than non-mycorrhizal controls, and translocated less Na to the shoots, perhaps protecting the plants from excessive Na accumulation. These preliminary results indicate that arbuscular mycorrhizas may make a substantial contribution to successful crop establishment in soils overlying areas of coal fly ash.

Biodegradation, Environmental↗
PubMed2002

Improved tolerance of maize plants to salt stress by arbuscular mycorrhiza is related to higher accumulation of soluble sugars in roots.

The effect of colonization with the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe on the growth and physiology of NaCl-stressed maize plants ( Zea mays L. cv. Yedan 13) was examined in the greenhouse. Maize plants were grown in sand with 0 or 100 mM NaCl and at two phosphorus (P) (0.05 and 0.1 mM) levels for 34 days, following 34 days of non-saline pre-treatment. Mycorrhizal plants maintained higher root and shoot dry weights. Concentrations of chlorophyll, P and soluble sugars were higher than in non-mycorrhizal plants under given NaCl and P levels. Sodium concentration in roots or shoots was similar in mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher electrolyte concentrations in roots and lower electrolyte leakage from roots than non-mycorrhizal plants under given NaCl and P levels. Although plants in the low P plus AM fungus treatment and those with high P minus AM fungus had similar P concentrations, the mycorrhizal plants still had higher dry weights, soluble sugars and electrolyte concentrations in roots. Similar relationships were observed regardless of the presence or absence of salt stress. Higher soluble sugars and electrolyte concentrations in mycorrhizal plants suggested a higher osmoregulating capacity of these plants. Alleviation of salt stress of a host plant by AM colonization appears not to be a specific effect. Furthermore, higher requirement for carbohydrates by AM fungi induces higher soluble sugar accumulation in host root tissues, which is independent of improvement in plant P status and enhances resistance to salt-induced osmotic stress in the mycorrhizal plant.

Fungi↗
PubMed2002

Kinase-deficient CMVpp65 triggers a CMVpp65 specific T-cell immune response in HLA-A*0201.Kb transgenic mice after DNA immunization.

CMVpp65, a candidate component of human cytomegalovirus (CMV) vaccines, has phosphokinase (PK) activity that could affect vaccine safety. A mutated form of CMVpp65 substituting asparagine for lysine at the adenosine triphosphate (ATP)-binding site (CMVpp65mII) is kinase-deficient. Using DNA immunizations in a transgenic human leucocyte antigen (HLA)A*0201.Kb mouse model, the mutated CMVpp65 induced cytotoxic T lymphocytes (CTL) immunity similarly to native CMVpp65. Murine CTL lines generated from these immunizations killed human cells either after sensitization with CMVpp65-specific peptides or after infection with either CMV-Towne strain or rvac-pp65. It is proposed that CMVpp65mII be evaluated in candidate vaccines for CMV.

Amino Acid Sequence↗
PubMed2001

Conservative front tracking and level set algorithms.

Hyperbolic conservation laws are foundational for many branches of continuum physics. Discontinuities in the solutions of these partial differential equations are widely recognized as a primary difficulty for numerical simulation, especially for thermal and shear discontinuities and fluid-fluid internal boundaries. We propose numerical algorithms that will (i) track these discontinuities as sharp internal boundaries, (ii) fully conserve the conserved quantities at a discrete level, even at the discontinuities, and (iii) display one order of numerical accuracy higher globally (at the discontinuity) than algorithms in common use. A significant improvement in simulation capabilities is anticipated through use of the proposed algorithms.

Journal Article↗
PubMed2001

Involvement of proteasomes in gene induction by interferon and double-stranded RNA.

Cytokine induced gene expression is mediated through the ligand-dependent activation of the janus kinase (jak)/signal transducer and activator of transcription (STAT) signal transduction pathway. The ubiquitin proteasome pathway functions in the controlled degradation of cellular proteins, and regulates cytokine signal transduction through the degradation of specific signaling components. Interferon (IFN) treatment induces genes that function in ubiquitin conjugation, suggesting a reciprocal regulation of proteasome activity and IFN action; however, a role for the proteasome in IFN-alpha-induced gene expression has not been examined. In this report, we find that proteasome inhibitors markedly reduce the induction of interferon-stimulated-gene 15 (ISG15), ISG43, and STAT1 by IFN-alpha and double-stranded RNA (dsRNA). The reduction in gene expression by proteasome inhibitors was dose-dependent, and was specific for ISGs. Neither STAT1 phosphorylation nor ISGF-3 activation was affected by proteasome inhibition at early times post-IFN treatment. Cycloheximide treatment diminished the effect of proteasome inhibitors on ISG induction, implicating an IFN/dsRNA-induced protein in this activity. These findings demonstrate that a functional proteasome is required for optimal ISG induction, and are consistent with a model in which IFN and dsRNA induce a proteasome-sensitive repressor of ISG expression.

Animals↗
PubMed2001

[Effects of di-zhen granules on catecholamine transmitter and gonadotropin of clamacteric rats with deficiency of yin brings about the interior heat-syndrome].

Fifteen-month-old Sprague-Dawley rats were given with some kinds of hot property of herb to produce model of Deficiency of yin brings about the interior heat-syndrome. The weight, water drinking volume, and body temperature of model rats were observed at the process of producing model and the treatment of di-zhen granules. Hypothalamic NE, DA and plasma NE, E concentration were determined by high-performance liquid chromatography, and serum E2, FSH, LH levels were determined by radioimmunoassay. The results were that after having been given the hot property of herbs for 2 weeks, the model rats increased water drinking volume and body temperature, which is similar to the appearance of patients with Deficiency of yin brings about the interior heat syndrome, and after having been treated with di-zhen granules, the water drinking volume and temperature of model rats decreased significantly (P < 0.01). The hypothalamic NE, DA, plasma NE, E, and the serum FSH, LH of the group treated with di-zhen granules were significantly lower than that of the model group and the normal group(P < 0.01). The results show that our model mentioned above possesses some characteristic features of the human climacteric syndrome which exhibits Deficiency of yin brings about the interior heat-syndrome. Di-zhen granules may regulate the function of GnRH neurons and other neurotic nucleus in hypothalamus, and then rectify the endocrine disorders of climacteric.

Animals↗
PubMed2001

Observation of all-metal aromatic molecules.

Aromaticity is a concept invented to account for the unusual stability of an important class of organic molecules: the aromatic compounds. Here we report experimental and theoretical evidence of aromaticity in all-metal systems. A series of bimetallic clusters with chemical composition MAl4- (M = Li, Na, or Cu), was created and studied with photoelectron spectroscopy and ab initio calculations. All the MAl4- species possess a pyramidal structure containing an M+ cation interacting with a square Al4(2-) unit. Ab initio studies indicate that Al4(2-) exhibits characteristics of aromaticity with two delocalized pi electrons (thus following the 4n + 2 electron counting rule) and a square planar structure and maintains its structural and electronic features in all the MAl4- complexes. These findings expand the aromaticity concept into the arena of all-metal species.

Journal Article↗
PubMed2001

2-buten-4-olide, an endogenous feeding suppressant, improves spatial performance through brain acidic fibroblast growth factor in mice.

Endogenous sugar acid 2-buten-4-olide, a satiety substance, has been shown to increase the blood glucose, norepinephrine, and glucocorticoid concentrations that are known to modulate learning and memory processes. The glucose-induced release of acidic fibroblast growth factor facilitated the hippocampus-dependent memory function. In the present study, we investigated the effect of 2-buten-4-olide on the spatial performance of male DDY mice undergoing the water maze task. The intraperitoneal injection of 2-buten-4-olide (5 mg/kg) facilitated the spatial performance, which was indicated by a reduction in the escape latency in which the mouse finds and climbs the goal platform in comparison to the vehicle-injected control mice. In the probe test after removing the platform, the 2-buten-4-olide-treated mice stayed a longer time in the quadrant where the platform was originally located and crossed more frequently at the platform location than did the control mice. The pretreatment of acidic fibroblast growth factor antibody injected into the lateral ventricle eliminated the effect of 2-buten-4-olide both during the training sessions and during the probe test. Therefore, 2-buten-4-olide was found to improve the spatial performance, and this effect is mediated, at least in part, by acidic fibroblast growth factor.

4-Butyrolactone↗
PubMed2001

Do domain interactions of glycosyl hydrolases from Clostridium thermocellum contribute to protein thermostability?

Cellulolytic and hemicellulolytic enzymes usually have a domain composition. The mutual influence of a cellulose-binding domain and a catalytic domain was investigated with cellobiohydrolase CelK and xylanase XynZ from Clostridium thermocellum. CelK is composed of an N-terminal family IV cellulose-binding domain (CBDIV(CelK)), a family 9 glycosyl hydrolase domain (Gh9(CelK)) and a dockerin domain (DD). CelK without the DD, (CBDIV-Gh9)(CelK) and CBDIV(CelK) bound cellulose. The thermostability of (CBDIV-Gh9)(CelK) was significantly higher than that of CBDIV(CelK) and Gh9(CelK). The temperature optima of (CBDIV-Gh9)(CelK) and Gh9(CelK) were 65 and 45 degrees C, respectively. XynZ consists of an N-terminal feruloyl esterase domain (FAE(XynZ)), a linker (L), a family VI CBD (CBDVI(XynZ)), a DD and a xylanase domain. FAE(XynZ) and (FAE-L-CBDVI)(XynZ), used in the present study did not bind cellulose, but both were highly thermostable. Replacement of CBDVI(XynZ) with CBDIV(CelK) resulted in chimeras with feruloyl esterase activity and the ability to bind cellulose. CBDIV(CelK)-FAE(XynZ) bound cellulose with parameters similar to that of (CBDIV-Gh9)(CelK). (FAE-L)(XynZ)-CBDIV(CelK) and FAE(XynZ)-CBDIV(CelK) had lower relative affinities and binding capacities than those of (CBDIV-Gh9)(CelK). The three chimeras were much less thermostable than FAE(XynZ) and (FAE-L-CBDVI)(XynZ). The results indicate that domains of glycosyl hydrolases are not randomly combined and that domain interactions affect properties of these domain-structured enzymes.

Amino Acid Sequence↗
PubMed2001

Noncatalytic docking domains of cellulosomes of anaerobic fungi.

A method is presented for the specific isolation of genes encoding cellulosome components from anaerobic fungi. The catalytic components of the cellulosome of anaerobic fungi typically contain, besides the catalytic domain, mostly two copies of a 40-amino-acid cysteine-rich, noncatalytic docking domain (NCDD) interspaced by short linkers. Degenerate primers were designed to anneal to the highly conserved region within the NCDDs of the monocentric fungus Piromyces sp. strain E2 and the polycentric fungus Orpinomyces sp. strain PC-2. Through PCR using cDNA from Orpinomyces sp. and genomic DNA from Piromyces sp. as templates, respectively, 9 and 19 PCR products were isolated encoding novel NCDD linker sequences. Screening of an Orpinomyces sp. cDNA library with four of these PCR products resulted in the isolation of new genes encoding cellulosome components. An alignment of the partial NCDD sequence information obtained and an alignment of database-accessible NCDD sequences, focusing on the number and position of cysteine residues, indicated the presence of three structural subfamilies within fungal NCDDs. Furthermore, evidence is presented that the NCDDs in CelC from the polycentric fungus Orpinomyces sp. strain PC-2 specifically recognize four proteins in a cellulosome preparation, indicating the presence of multiple scaffoldins.

Amino Acid Sequence↗
PubMed2001

Properties and mutation analysis of the CelK cellulose-binding domain from the Clostridium thermocellum cellulosome.

The family IV cellulose-binding domain of Clostridium thermocellum CelK (CBD(CelK)) was expressed in Escherichia coli and purified. It binds to acid-swollen cellulose (ASC) and bacterial microcrystalline cellulose (BMCC) with capacities of 16.03 and 3.95 micromol/g of cellulose and relative affinities (K(r)) of 2.33 and 9.87 liters/g, respectively. The CBD(CelK) is the first representative of family IV CBDs to exhibit an affinity for BMCC. The CBD(CelK) also binds to the soluble polysaccharides lichenin, glucomannan, and barley beta-glucan, which are substrates for CelK. It does not bind to xylan, galactomannan, and carboxymethyl cellulose. The CBD(CelK) contains 1 mol of calcium per mol. The CBD(CelK) has three thiol groups and one disulfide, reduction of which results in total loss of cellulose-binding ability. To reveal amino acid residues important for biological function of the domain and to investigate the role of calcium in the CBD(CelK) four highly conserved aromatic residues (Trp(56), Trp(94), Tyr(111), and Tyr(136)) and Asp(192) were mutated into alanines, giving the mutants W56A, W94A, Y111A, Y136A, and D192A. In addition 14 N-terminal amino acids were deleted, giving the CBD-N(CelK). The CBD-N(CelK) and D192A retained binding parameters close to that of the intact CBD(CelK), W56A and W94A totally lost the ability to bind to cellulose, Y136A bound to both ASC and BMCC but with significantly reduced binding capacity and K(r) and Y111A bound weakly to ASC and did not bind to BMCC. Mutations of the aromatic residues in the CBD(CelK) led to structural changes revealed by studying solubility, circular-dichroism spectra, dimer formation, and aggregation. Calcium content was drastically decreased in D192A. The results suggest that Asp192 is in the calcium-binding site of the CBD(CelK) and that calcium does not affect binding to cellulose. The 14 amino acids from the N terminus of the CBD(CelK) are not important for binding. Tyr136, corresponding to Cellulomonas fimi CenC CBD(N1) Y85, located near the binding cleft, might be involved in the formation of the binding surface, while Y111, W56A, and W94A are essential for the binding process by keeping the CBD(CelK) correctly folded.

Amino Acid Sequence↗
PubMed2001

Role for p53 in gene induction by double-stranded RNA.

Cross talk between p53 and interferon-regulated pathways is implicated in the induction of gene expression by biologic and genotoxic stresses. We demonstrate that the interferon-stimulated gene ISG15 is induced by p53 and that p53 is required for optimal gene induction by double-stranded RNA (dsRNA), but not interferon. Interestingly, virus induces ISG15 in the absence of p53, suggesting that virus and dsRNA employ distinct signaling pathways.

Animals↗
PubMed2001

Relationship between phenotypes of cell-function differentiation and pathobiological behavior of gastric carcinomas.

AIM: To reveal the correlation between the functional differentiation phenotypes of gastric carcinoma cells and the invasion and metastasis by a new way of cell-function classification. METHODS: Surgically resected specimens of 361 gastric carcinomas(GC) were investigated with enzyme-, mucin-, and tumor-related marker immunohistochemistry. According to the direction of cell-function differentiation, stomach carcinomas were divided into five functionally differentiated types. RESULTS: (1) Absorptive function differentiation type (AFDT): there were 82 (22.7%) patients including 76 (92.7%) aged 45 years. Sixty-nine (84.1%) cases belonged to the intestinal type. Thirty-eight (46.3%) expressed CD44v6 and 9 (13.6%) of 66 male patients developed liver metastasis. The 5-year survival rate of patients in this group (58.5%) was higher than those with the other types (P<0.01). (2) Mucin secreting function differentiation type (MSFDT): 54 (15%) cases. Fifty-three (98.1%) tumors had penetrated the serosa, 12 (22.2%) expressed ER and 22 (40.7%) expressed CD44v6. The postoperative 5-year survival rate was 28.6%. (3) Absorptive and mucin-producing function differentiation type (AMPFDT): there were 180 (49.9%) cases, including 31 (17.2%) aged younger than 45 years. The tumor was more common in women (62, 34.4%,) and expressed more frequently estrogen receptors (ER) (129, 81.7%) than other types (P<0.01). Ovary metastasis was found in 12 (19.4%) out of 62 female subjects. The patients with this type GC had the lowest 5-year survival rate (24.7%) among all types. (4) Specific function differentiation type (SFDT): 13 (3.6%) cases. Nine (69.2%) tumors of this type derived from APUD system, the other 4 (30.7%) were of different histological differentiation. Sixty per cent of the patients survived at least five years. (5) Non-function differentiation type (NFDT): 32 (8.9%) cases. Nineteen (59.4%) cases had lymph node metastases but no one with liver or ovary metastasis. The 5-year survival rate was 28.1%. CONCLUSION: This new cell-function classification of GC is helpful in indicating the characteristics of invasion and metastasis of GC with different cell-function differentiation phenotypes. Further study is needed to disclose the correlation between the cell-functional differentiation phenotypes and the relevant genotypes and the biological behavior of gastric carcinoma.

Biomarkers, Tumor↗
PubMed2001

Tibetan population data on the multiplex short tandem repeat loci--D16S539, D7S820, and D13S317.

The multiplex amplification system of three tetrameric short tandem repeats loci (D16S539, D7S820, and D13S317) have been analysed extensively in various populations for forensic application. Population genetic studies were carried out for these three loci in a population sample of 129 unrelated Tibetan individuals by using a multiplex polymerase chain reaction (PCR) followed by 4% polyacrylamide gel electrophoresis (PAGE) and silver staining. All loci were in accordance with the Hardy-Weinberg expectations. The observed heterozygosities of three loci-D16S539, D7S820, and D13S317 were 73.3%, 81.4% and 80.6%, respectively. The polymorphism information contents (PIC) were 0.84, 0.80 and 0.83, respectively. Comparing with Han population, there was no statistically significant difference except for D16S539 locus.

Chromosome Mapping↗
PubMed2001

[Differential expression of genes in the pigeon forebrain after removal of the left retina].

Suppression subtractive hybridization (SSH) was used to analyze differential expression of genes in the pigeon forebrain after the left retina of the pigeon was removed at hatching. Four genes out of the 14 identified clones produced positive hybridization signals as shown by reverse Northern blot. Sequencing results showed that the length of PFB/SSH-8 is 226 bp, of which 138 bp produced a homology of 85% with human CaMI; the length of PFB/SSH-15 is 252 bp, showing low homology with nexin I alpha; no matched homological information was found in the remaining 2 clones.

Animals↗