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Biomedical subjects

X F Chen

Publications and source records attributed to X F Chen.

At least 19 recordsLinked to original sources
PubMed2006

Effects of topography on simulated net primary productivity at landscape scale.

Local topography significantly affects spatial variations of climatic variables and soil water movement in complex terrain. Therefore, the distribution and productivity of ecosystems are closely linked to topography. Using a coupled terrestrial carbon and hydrological model (BEPS-TerrainLab model), the topographic effects on the net primary productivity (NPP) are analyzed through four modelling experiments for a 5700 km(2) area in Baohe River basin, Shaanxi Province, northwest of China. The model was able to capture 81% of the variability in NPP estimated from tree rings, with a mean relative error of 3.1%. The average NPP in 2003 for the study area was 741 gCm(-2)yr(-1) from a model run including topographic effects on the distributions of climate variables and lateral flow of ground water. Topography has considerable effect on NPP, which peaks near 1350 m above the sea level. An elevation increase of 100 m above this level reduces the average annual NPP by about 25 gCm(-2). The terrain aspect gives rise to a NPP change of 5% for forests located below 1900 m as a result of its influence on incident solar radiation. For the whole study area, a simulation totally excluding topographic effects on the distributions of climatic variables and ground water movement overestimated the average NPP by 5%.

Biomass↗
PubMed2006

Nano-structural bioactive gradient coating fabricated by computer controlled plasma-spraying technology.

The poor mechanical property of hydroxyapatite was the major problem for load bearing and implant coating in clinical applications. To overcome this weakness, a bioactive gradient coating with a special design composition of hydroxyapatite (HA), ZrO2, Ti, bioglass was developed. This 120 microm coating with an upper layer of 30-50 microm porous HA produced by computer controlled plasma spraying which maintained energy level of the plasma which ensure proper melting of powder. The crystal size of the coating was 18.6-26.2 nm. Transformation of t-ZrO2 to m-ZrO2 reduced the thermal stress that weakened the coating and lowered down interfacial strength of the coating and metal substrate. Thermal stress of sprayed coating was 16.4 MPa which was much smaller than the sample without thermal treatment of 67.1 MPa. Interfacial strength between the coating and metal substrate was 53 MPa which is much higher than conventional Hydroxyapatite coating. Based on XRD analysis crystallinity of HA approached 98%. Therefore, high temperature treatment improved long term stability of the coating through improved crystallinity of hydroxyapatite and reduced other impure calcium phosphate phase.

Aluminum Oxide↗
PubMed2001

Two-dimensional coordination polymers of copper(II) with oxalate: lattice water control of structure.

Three oxalate copper(II) complexes, [Cu(bipy)(C(2)O(4))(H(2)O)].2H(2)O (1), [Cu(nphen)(C(2)O(4))(H(2)O)].2H(2)O (2), and [Cu(phen)(C(2)O(4))(H(2)O)].H(2)O (3) (bipy = 2,2'-bipyridine, nphen = 5-nitro-1,10-phenanthroline and phen = 1,10-phenanthroline), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in the triclinic space group P1 with a = 7.2554(10) A, b = 10.5712(14) A, c = 10.8178(15) A, alpha = 62.086(2) degrees, beta = 77.478(3) degrees, gamma = 81.773(3) degrees, and Z = 2. Compound 2 crystallizes in the triclinic space group P1 with a = 9.582(2) A, b = 10.086(2) A, c = 10.592(2) A, alpha = 64.18(3) degrees, beta = 79.47(3) degrees, gamma = 60.06(3) degrees, and Z = 2. Compound 3 crystallizes in the monoclinic space group P2(1)/n with a = 8.4655(7) A, b = 9.7057(8) A, c = 17.4572(14) A; beta = 103.865(2) degrees, and Z = 4. The crystal structures of all complexes consist of neutral [Cu(L)(C(2)O(4))(H(2)O)] (L = bipy, nphen, and phen) units and one or two lattice water molecules in the unit cell. Each copper atom in 1, 2, and 3 involves a five-coordinate CuN(2)O(2)O' environment, with a distorted square-pyramidal structure. In 1 and 2, two lattice water molecules are around each unit of [CuL(C(2)O(4))(H(2)O)] (L = bipy and nphen) and form two-dimensional networks. Only one lattice water molecule is found in the unit cell of 3 and the two-dimensional structure is different from 1 and 2. The extended three-dimensional structure is formed through pi-pi interactions between layers. The influences of hydrogen bonds and the sizes and Lewis basicity of ligands to the structures were discussed.

Journal Article↗
PubMed1998

Instability at the k2 Mdh1-n y20 chromosomal region in soybean.

Ten mutants have been reported at the k2 (tan saddle seed coat) Mdh1-n (mitochondrial malate dehydrogenase 1 null) y20 (yellow foliage) chromosomal region in soybean [Glycine max (L.) Merr.]. The precise genetic mechanism(s) responsible for generating these mutants is (are) not known. The objective of this study was to determine whether chromosomal instability exists at this region. We introduced the w4-m and Y18-m mutable systems into the three independent sources of tan saddle seed coat mutants, T239 (k2), T261 (k2 Mdh1-n), and L67-3483 (k2). A total of 12 bright yellow mutants were isolated with tan saddle seed coat, malate dehydrogenase 1 null phenotypes. Of these, 11 were found in 11 F2 mutant families out of a total of 977 derived by crossing T239 (k2), T261 (k2 Mdh1-n), and L67-3483 (k2) with six lines suspected to contain active transposable elements. One was found in the F3 generation derived from the cross A1937 x T239 (k2). Of the 11 F2 mutant families, 10 (out of a total of 381 F2 families) were associated with the T239 (k2) genetic background, and one out of 323 was associated with the T261 (k2 Mdh1-n) genetic background. But no mutation events were found among the 273 families with the L67-3483 (k2) genetic background. Allelism and inheritance studies indicated that these 12 bright yellow mutants were new mutants in the k2 Mdh1-n y20 chromosomal region. Thus, on introducing the w4-m and Y18-m mutable systems into T239 (k2) and T261 (k2 Mdh1-n) genetic backgrounds, chromosomal instability was induced in this region. In addition, 21 greenish yellow mutants were identified in the total of 977 F2 families. All 21 greenish yellow mutants were associated with the T239 (k2) genetic background. The mutations for greenish yellow foliage affected foliage color only at the seedling stage. Cosegregation of the tan saddle seed coat character with greenish yellow foliage were observed for these 21 greenish yellow mutants, suggesting that the greenish yellow phenotype may be due to a pleiotropic effect of the k2 allele in T239 or to chromosomal rearrangements at or near the k2 allele in T239. Finally, we believe that the genetic mechanism responsible for this high frequency of instability at the k2 Mdh1-n y20 chromosomal region involves receptor element activities present at this chromosomal region, which may contain complex chromosomal rearrangements in T239 and T261.

Chromosome Breakage↗
PubMed1998

[Effect of AVP(4-8) administration on Ca2+/CaM-dependent protein kinase II autophosphorylation in rat brain].

The extent increase of Ca2+/CaM-dependent protein kinase II (CaMK II) autophosphorylation in various brain regions of rat reached a maximum value, one hour after s.c. administration of AVP(4-8). The increase in the cortex amounted to 192% of the control (P < 0.001), while in the hippocampus only 40% (P < 0.05). The autophosphorylation of CaMK II was dependent on both Ca2+ and CaM. Western blotting with anti-CaMK II alpha monoclonal antibody showed that the content of CaMK II alpha in cortex did not show detectable change in 1 h as compared to the control group. ZDC(C)PR, an antagonist of AVP(4-8), markedly blocked the effect of AVP(4-8), suggesting that AVP (4-8) stimulated CaMK II autophosphorylation is mediated through its receptor.

Animals↗
PubMed1996

Novel endogenous protein kinase C substrate proteins, neutrinins, in brain synaptic membranes of maturing rat.

A new family of membrane phosphoproteins designated as P9, P12, P15, P16, and P20 with corresponding apparent molecular weights of 9K, 12K, 15K, 16K, and 20K was characterized from rat brain by using in vitro exogenous or endogenous phosphorylation and autoradiography. As the phosphorylation was selectively inhibited by the protein kinase C (PKC) inhibitor PKC19-31 or Ca(2+)-chelating reagents and again stimulated by the PKC activator phorbol 12, 13-dibutyrate, these proteins are thought to be the natural PKC substrates. Because P12, P15, P16, and P20 were neutral proteins (pl 7.0) and specifically distributed in neuronal membranes, the new family of membrane-associated PKC substrate proteins was referred to as neutrinins. Neutrinins were widely distributed in rat brain, being especially plentiful in the spinal cord, medulla oblongata, cerebellum, and midbrain, relatively scanty in the cerebral cortex, but lacking in cytosol of brain areas and cell membrane preparations of peripheral tissues. The expression of the developmental changes of neutrinins has been monitored by the in vitro exogenous phosphorylation approach, i.e., adding purified PKC to a deactivated synaptosomal plasma membrane system. Levels of all the neutrinin proteins in rat cerebral cortex, as represented by P12, P15, and P16, showed an ontogenetic increase from the early postnatal days to the adult. This appears to be correlated with the commencement of synaptogenesis.

Aging↗
PubMed1994

[Biological characteristics of Ligusticum chuanxiong Hort].

Observational studies were conducted on the biological characteristics of Ligusticum chuanxiong, such as suitable growth environment, growing period, growth of stems, leaves and rhizomes, yield structure, etc. The specific regularities of each growth period were also studied.

Plants, Medicinal↗
PubMed1994

Clinical significance of elevated serum soluble interleukin-2 receptor in gastric cancer.

This is China's pilot study in the assessment of the diagnostic value of serum soluble IL-2 receptor (sIL-2R) in gastric cancer. We measured its level by ELISA method in 45 patients with gastric cancer (without metastasis: 32; with metastasis: 5; recurrence: 8) 27 gastric ulcer, 27 superficial gastritis and 44 healthy controls. The mean-serum sIL-2R levels were significantly elevated in cancer patients, those with metastasis showed even higher levels than those without metastasis. These results suggested that sIL-2R can be used as a marker of host biological response in gastric cancer patients as well as a tumor marker for the diagnosis of the disease.

Adult↗
PubMed1993

ZNC(C)PR affects developmental changes of P46 phosphorylation in rat hippocampus.

Protein phosphorylation has been suggested to be correlated with brain development and with the molecular mechanism of behavioral effects of neuropeptides. The present study reports in vitro endogenous phosphorylation of P46, a membrane-associated protein that is changed during development of the rat hippocampus. This study indicated that the degree of endogenous phosphorylation may be correlated with the establishment of synaptic connections. Interestingly, P46 was proved to be identical to a well-known growth-associated protein B-50/GAP-43 in its identical apparent molecular weight, isoelectric point, phosphorylation dependence, and the cross immunoreaction of monoclonal anti-B-50/GAP-43 antibody and P46. Moreover, neonatal administration of neuropeptide ZNC(C)PR could facilitate the developmental progress of P46 endogenous phosphorylation. It is suggested that the changes in P46 phosphorylation could be involved in the cellular mechanism of ZNC(C)PR behavioral effects on learning.

Animals↗
PubMed1993

Potentiation of synaptic transmission by neuropeptide AVP4-8 (ZNC(C)PR) in rat hippocampal slices.

The effect of AVP4-8 on synaptic transmission in rat hippocampal slices was studied using both extracellular and intracellular recording. AVP4-8 induced a long-lasting potentiation effect on the evoked EPSP and enhanced LTP in pyramidal neurones. The lowest effective concentration of AVP4-8 was 1 x 10(-12) M, three to four orders of magnitude lower than that of AVP. These findings support the concept that AVP4-8 is a new memory-enhancing peptide and should be written as ZNC(C)PR. The results show that the potentiation effect of ZNC(C)PR is mainly due to a presynaptic mechanism of action.

Animals↗
PubMed1993

[3,4-Diaminopyridine-evoked norepinephrine release and B-50 (GAP-43) phosphorylation].

3,4-Diaminopyridine (3,4-DAP 100 mumol.L-1) evoked [3H]norepinephrine ([3H]NE) release in rat hippocampal slices preincubated with [3H]NE and superfused with medium with or without Ca2+. Phorbolester 4 beta-phorbol 12, 13, dibutyrate 1 mumol.L-1) enhanced and polymyxin B (100 mumol.L-1) inhibited the release of [3H]NE under both conditions. The neuron-specific protein B-50 is a major presynaptic substrate of protein kinase C and involved in exocytosis. Using in situ protein phosphorylation analyzed by SDS-PAGE and autoradiography, we observed that B-50 phosphorylation was significantly decreased by 3,4-DAP in the presence of extracellular Ca2+ and completely inhibited by removal of extracellular Ca2+. It was suggested that B-50 phosphorylation was not involved in 3,4-DAP-evoked [3H]NE release.

4-Aminopyridine↗
PubMed1992

Saponins from stem bark of Petersianthus macrocarpus.

Two bioactive saponins were isolated from the stem bark of Petersianthus macrocarpus. Their structures were elucidated by chemical degradations and by a combination of 2D NMR techniques and by Californium plasma desorption mass spectrometry. They are 3-O-([beta-D-galactopyranosyl (1-->2)][beta-D-galactopyranosyl (1-->3)]- beta-D-glucuronopyranosyl)-21-O-[3-(3-tigloyloxynilic acid)-4-tigloyloxy- alpha-L-arabinopyranosyl] barringtogenol C and 3-O-([beta-D-galactopyranosyl (1-->2)][beta-D-galactopyranosyl (1-->3)]-beta-D-glucuronopyranosyl)-28-O-alpha-L-rhamnopyranosyl barringtogenol C-21-O-benzoate. The absolute configuration of nilic acid was determined by partial synthesis. 3,3'-Dimethoxy ellagic acid and 3,3'-dimethoxy-4-O-beta-D- glucopyranosyl ellagic acid were also isolated.

Carbohydrate Sequence↗
PubMed1991

Pharmacological properties of galenical preparation. XV. Pharmacokinetics study of evocarpine and its metabolite in rats.

It is known that when methanol extract of Evodia fruit is orally administered, 5-(1,4-dihydro-1-methyl-4-oxo-2-quinolin-2-yl) pentanoic acid (EVCA) is excreated as a matabolite in rat urine. In this study, we separated Evodia fruit extract into major alkaloids administered each alkaloid individually to male Wistar rats. Consequently, it was demonstrated that the original substance of the metabolite are evocarpine and its analogues, dihydroevocarpine and 1-methyl-2-undecenyl-4(1H)-quinolone. Investigation of a blood sample after oral administration of evocarpine by high performance liquid chromatography confirmed that the substance was absorbed without alteration. Pharmacokinetics of evocarpine after intravenous injection was expressed in a one-compartment model, showing a linear elimination of plasma evocarpine up to a dosage of 75 mg/kg. Total plasma clearance (CL), volume of distribution (Vd), and half-life (T1/2) of evocarpine were 60 ml/min.kg, 3.21/kg and 0.6 h-1, respectively. Metabolic ratio of evocarpine into EVCA after intravenous injection was 15.4%, and absorption ratio of the unaltered compound calculated from the levels of AUC after oral administration and intravenous injection was 4.7%. In this paper, it is shown that evocarpine is absorbed amount 100% when it is administered orally.

Animals↗
PubMed1990

[Study on antifreeze protein in fishes. II. The cloning of antifreeze protein gene cDNA of Pseudopleuronectes yokohamae and its expression in E. coli].

Pseudopleuronectes yokohamae, existing in the Yellow Sea of China, contains antifreeze peptide (AFP). This protein could depress the serum freezing point. On the basis of purification and characterization of this protein, we synthesized a segment of Oligo-nucleotides of antifreeze protein gene as a primer and hybridized with the mRNA of Pseudopleuronectes yokohamae. The cDNA of antifreeze protein gene has specifically been reversely transcribed. This segment has been cloned onto pUC19 with Ecor I linker method. After confirmation of the insert segment of the cDNA of antifreeze protein gene, the zymogram was detected and the sequence of the nucleotides was determined. This recombinated clone was transformed into E. coli JM83 and expressed well.

Amino Acid Sequence↗
PubMed1989

[NK cell activity in patients with kidney insufficiency].

Natural killer cell (NKC) plays an important role in anti-cancer, anti-virus and the regulation of immune reaction in human body. NK cell activities from the peripheral blood were determined with 51Cr release method from the human erythroleukemia cell line K562 in 61 patients, who were selected in the light of the standard of deficiency syndrome in TCM with insufficiency of the Kidney in which 12 kinds of diseases in western medicine were included, and 60 healthy subjects as control group. The patients with insufficiency of the Kidney showed significantly decrease in NK cell activity compared to the control group (25.29 +/- 10.20 vs 56.27 +/- 16.72, P less than 0.001). NK cell activities in 20 out of 60 patients, with deficiency of Kidney-Yang, were lower than 21 with deficiency or Kidney-Yin (19.38 +/- 7.44 vs 26.60 +/- 8.95, P less than 0.01) and 20 with deficiency of Kidney-Qi (19.38 +/- 7.44 vs 29.38 +/- 11.30, P less than 0.01), respectively, while there was no difference between the deficiency of Kidney-Qi (P greater than 0.05). The authors also found that NK cell activities of healthy subjects were strongly inhibited by plasma from 43 out of 61 patients. These results suggested that decreased NK cell activity is one of the common characters in patients with insufficiency of the Kidney in TCM and there are some inhibitory substances against NK cell activity in plasma of ones. The fact that NK cell activity of patients with deficiency of Kidney-Yang was the lowest among three kinds patients with insufficiency of the Kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗