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Biomedical subjects

P Xu

Publications and source records attributed to P Xu.

At least 145 records · Page 8Linked to original sources

Generation of reovirus core-like particles in cells infected with hybrid vaccinia viruses that express genome segments L1, L2, L3, and S2.

When mouse L fibroblasts are infected with various combinations of recombinant vaccinia viruses possessing thymidine kinase (TK) genes with inserted reovirus genes that encode core components, particles are formed that closely resemble reovirus cores. In cells infected with vaccinia viruses that express reovirus proteins lambda 1 and sigma 2, particles are formed that are very similar to reovirus core shells; if, in addition, the cells are also infected with vaccinia virus that expresses protein lambda 2, particles are formed that also possess the characteristic icosahedrally located projections/spikes that are present on reovirus cores. If, in either case, the cells are also infected with vaccinia virus that expresses the reovirus RNA polymerase, protein lambda 3, the resultant particles are morphologically identical with those formed in its absence, but also contain protein lambda 3.

Animals↗

Post-transcriptional control of cell type-specific gene expression in bundle sheath and mesophyll chloroplasts of Amaranthus hypochondriacus.

Plants that utilize the highly efficient C4 photosynthetic pathway possess two types of specialized leaf cells, the mesophyll and bundle sheath. In mature leaves of amaranth, a dicotyledonous C4 plant, ribulose 1,5-bisphosphate carboxylase (Rubisco) is localized specifically to the chloroplasts of bundle sheath cells, and is not present in the chloroplasts of mesophyll cells. The cell type-specific expression of the chloroplast-encoded Rubisco large subunit (rbcL) gene, and other representative chloroplastic genes, was investigated by using separated bundle sheath and mesophyll chloroplasts prepared from mature amaranth leaves. One-dimensional SDS-polyacrylamide gel electrophoresis revealed several differences in the polypeptide compositions of the two chloroplast types. Western analysis demonstrated that, as in the intact leaves, the Rubisco LSU polypeptide was present only in chloroplast preparations from bundle sheath cells. Pyruvate orthophosphate dikinase (PPdK), a nuclear-encoded chloroplastic enzyme, was found only in the mesophyll chloroplast preparations. rbcL mRNA was present only in the bundle sheath chloroplast preparations, whereas transcripts for the chloroplast-encoded psbA, psaA-B, and rpl2 genes were present in both chloroplast types. Although the rbcL message accumulated only in bundle sheath chloroplasts, run-on transcription analysis indicated that the rbcL gene was transcribed in both bundle sheath and mesophyll chloroplast preparations. Therefore, differential rbcL gene expression in the isolated C4 chloroplasts is regulated, at least in part, at the post-transcriptional level. Possibly this control is mediated by differential processing or stabilization of the rbcL transcript.

Chloroplasts↗

urbs1, a gene regulating siderophore biosynthesis in Ustilago maydis, encodes a protein similar to the erythroid transcription factor GATA-1.

Ustilago maydis secretes ferrichrome-type siderophores, ferric-ion-binding compounds, in response to iron starvation. TA2701, a non-enterobactin-producing, non-ferrichrome-utilizing mutant of Salmonella typhimurium LT-2, was employed as a biological indicator in a novel screening method to isolate three N-methyl-N'-nitro-N-nitrosoguanidine-induced U. maydis mutants defective in the regulation of ferrichrome-type siderophore biosynthesis. These mutants displayed a constitutive phenotype; they produced siderophores in the presence of iron concentrations that would typically repress siderophore synthesis in wild-type strains. A 4.8-kb fragment of U. maydis genomic DNA capable of restoring normal regulation of siderophore biosynthesis in the constitutive mutants was identified. This segment of DNA contains an intronless open reading frame that specifies a protein of 950 amino acids containing two finger motifs similar to those found in the erythroid transcription factor GATA-1. Disruption of this open reading frame in a wild-type strain gave rise to cells that produced siderophores constitutively. Genetic studies indicated that the disruption mutation was allelic to the chemically induced mutations, confirming that the structural gene for a regulator rather than a suppressor gene had been cloned. Northern (RNA) analysis of the gene revealed a 4.2-kb transcript that is expressed constitutively at low levels in wild-type cells. The data support the hypothesis that this gene, which we designate urbs1 (Ustilago regulator of biosynthesis of siderophores), acts directly or indirectly to repress biosynthesis of siderophores in U. maydis.

Amino Acid Sequence↗

[Morphological study on acupuncture in interfering experimental cerebral infarction in rats. II. Change of ischemic area in cerebral interior].

Occluding unilateral middle cerebral artery (MCAO) of rat, the ischemic volume within cerebrum shown by nitroblue tetrazolium (N-BT) histochemistry method and effect of acupuncture were observed dynamically. 18 hs after MCAO, the ischemic area began to extend from cerebral cortex into subcortical area. 36 hs after MCAO, there was a large ischemic area in cortical and subcortical area, whose volume occupied 20.7 percent of the whole. Whereas the ischemic area in the cortex disappeared in the acupuncture group, the ischemic volume reduced to 6.3 percent of the whole. The experiment pointed out that the acupuncture is an effective therapeutic procedure for cerebral infarction.

Acupuncture Therapy↗

[Morphological study on acupuncture in interfering experimental cerebral infarction in rat. I. Compensation of cerebral PIA mater artery in cerebral surface].

Occluding unilateral middle cerebral artery (MCAo) of rat, the compensatory blood vessels (CBV) within ischemic area in cerebral surface shown by cerebral perfusion and effect of acupuncture were observed dynamically. Perfusing immediately after MCAo, there was no any blood vessel in the ischemic area. In acupuncture group, the CBV had extended a lot from anastomotic network of cerebral pia mater (ACA-MCA, PCA-MCA) located in marginal zone of ischemic area 3 hs after MCAo. 6.24 and 48 hs after MCAo, the CBV increased much more than control group (non-acupuncture) P < 0.01. The experiment pointed out that there existed a serious vasospasm in the MCA system in initial stage of MCAo, which led up to decompensation in the ischemic area. The acupuncture can remit the vasospasm, and reverse the deteriorated process in early.

Acupuncture Therapy↗

Increased lipoprotein (a) as an independent risk factor for cardiovascular and cerebrovascular diseases.

We quantified serum lipoprotein(a) [Lp(a)] in 1266 healthy persons and established the reference value of Lp(a) in groups of age and sex. The Lp(a) in myocardial infarction (MI) survivors, stroke and primary hypertension patients were determined in comparison with that of age-matched normal controls. Moreover, cholesterol, triglyceride, HDL-cholesterol, apo Al and apo B were measured. The Lp(a) concentrations were not correlated with other lipids in normal controls and patients. Our results suggest that increased Lp(a) is an independent risk factor for MI and stroke patients. The total detective rate of abnormal lipids in MI and stroke patients was as high as 50% and 53.8% (Lp(a) excluded) as well as 65.7% and 64.9% (Lp(a) included) respectively.

Adolescent↗

[Determination of glycyrrhizin in glycyrrhiza and it's preparations by ion-pair HPLC].

Glycyrrhizin is the main component of glycyrrhiza. In this article an Ion-pair high performance liquid chromatography (HPLC) method is described for the determination of glycyrrhizin in two kinds of glycyrrhiza from different origins and twelve kinds of Chinese traditional patent medicine containing glycyrrhiza. A reversed phase system was used, including an ODS column with water and methanol (36:64) as the mobile phase which contained 5mmol/L tetra-n-butyl ammonium hydroxide and was adjusted to pH 6.0 by phosphoric acid. The column temperature was 35 degrees C; the detection was performed at 254 nm. Under this condition glycyrrhizin could be separated from other components. The limit of detection was 13ng, and the average recovery was 99.85%. During the experiments, we studied the concentration of counter-ion, the mixing ratio of methanol to water, the pH of the mobile phase and column temperature and their effect on the capacity factor of compound and resolution. We also studied the method of pre-treatment for the samples. The determination method is simple and accurate.

Chromatography, High Pressure Liquid↗

Evolution and differential expression of the (1-->3)-beta-glucan endohydrolase-encoding gene family in barley, Hordeum vulgare.

The (1-->3)-beta-D-glucan glucanohydrolases [(1-->3)-GGH; EC 3.2.1.39] of barley (Hordeum vulgare L., cv Clipper) are encoded by a small gene family. Amino acid sequences deduced from cDNA and genomic clones for six members of the family exhibit overall positional identities ranging from 44% to 78%. Specific DNA and oligodeoxyribonucleotide (oligo) probes have been used to demonstrate that the (1-->3)-GGH-encoding genes are differentially transcribed in young roots, young leaves and the aleurone of germinated grain. The high degree of sequence homology, coupled with characteristic patterns of codon usage and insertion of a single intron at a highly conserved position in the signal peptide region, indicate that the genes have shared a common evolutionary history. Similar structural features in genes encoding barley (1-->3,1-->4)-beta-glucan 4-glucanohydrolases [(1-->3,1-->4)-GGH; EC 3.2.1.73] further indicate that the (1-->3)-GGHs and (1-->3,1-->4)-GGHs are derived from a single 'super' gene family, in which genes encoding enzymes with related yet quite distinct substrate specificities have evolved, with an associated specialization of function. The (1-->3,1-->4)-GGHs mediate in plant cell wall metabolism through their ability to hydrolyse the (1-->3,1-->4)-beta-glucans that are the major constituents in barley walls, while the (1-->3)-GGHs, which are unable to degrade the plant (1-->3,1-->4)-beta-glucans, can hydrolyse the (1-->3)- and (1-->3,1-->6)-beta-glucans of fungal cell walls.

Amino Acid Sequence↗

Purification, characterization and gene structure of (1-->3)-beta-glucanase isoenzyme GIII from barley (Hordeum vulgare).

A new member of the barley (1-->3)-beta-glucan glucanohydrolase family of enzymes has been purified from extracts of germinated grain and young seedlings by fractional precipitation with ammonium sulphate, ion-exchange chromatography, chromatofocussing and gel-filtration chromatography. The enzyme, which has been designated (1-->3)-beta-glucanase isoenzyme GIII, is a basic protein with an apparent molecular mass of 32 000 Da. Oligosaccharide products released by the enzyme during hydrolysis of the (1-->3)-beta-glucan, laminarin, indicate that the enzyme is an endohydrolase. A 2349-bp fragment of barley genomic DNA has been isolated and identified as the gene encoding the (1-->3)-beta-glucanase isoenzyme GIII. The open reading frame encoding the isoenzyme is interrupted by a single intron of 180 bp that splits a codon in the putative signal-peptide region. Northern-blot analyses with gene-specific probes indicate that the (1-->3)-beta-glucanase isoenzyme GIII mRNA accumulates in developing leaves; no mRNA transcripts were detected in the aleurone or scutellum of germinated grain, or in mature vegetative tissues. Although plant (1-->3)-beta-glucanases are generally classified as 'pathogenesis-related' proteins, the physiological function of the barley (1-->3)-beta-glucanase isoenzyme GIII is unclear.

Amino Acid Sequence↗

Recent advances in methodology for analysis of phytate and inositol phosphates in foods.

This review summarises the methods available for the analysis of phytate and structurally related molecules, i.e., inositol polyphosphates. Phytate has been determined by colorimetry, low pressure ion exchange column chromatography, phosphorus-31 fourier transform nuclear magnetic resonance spectroscopy (31P FT NMR), near-infrared reflectance spectroscopy and high performance liquid chromatography (HPLC). Among these techniques anion exchange column chromatography and HPLC were shown to be best suited for separation of inositol phosphates. Since inositol phosphates do not have a characteristic absorption spectrum, their detection in HPLC analysis is limited to methods employing monitoring of refractive index, post column reaction products, conductivity or indirect detection although other detection methods may be feasible. As refractive index detection under isocratic eluent conditions is relatively easy to manipulate, anion-exchange HPLC methods using a low capacity column or ion-pair HPLC methods are recommended for the analysis of inositol phosphates in nutritional studies.

Chromatography↗

Delayed-focus pulses for magnetic resonance imaging: an evolutionary approach.

An evolutionary algorithm has been used to design a family of shaped radiofrequency pulses giving uniform absorption-mode excitation across a predetermined frequency band. By allowing a free precession interval before signal acquisition, time is left for field gradients to be switched and for undesirable transients to decay.

Electromagnetic Phenomena↗

[Synthesis of hexamethyl propylamine oxime and comparative study of its diastereoisomers].

This is a report on the synthesis of hexamethyl-propylene-amine oxime (HM-PAO), a new agent for regional cerebral blood flow (gamma CBF) imaging, the separation of its diastereoisomers (dl- and meso-HM-PAO), and a comparative study of three forms of Tc- 99m labelled HM-PAO (dl-, meso- and mixture-) in chromatography, mice biodistribution and rabbit imaging. The results showed that the Rf value of Tc-99m-dl-HM-PAO (0.8-1.0) on silica G thin layer chromatography with MEK as solvent was different from that of Tc-99m-meso-HM-PAO (0.6-0.8), and that the retention of dl- isomer in the brain was higher and more static than those of meso-and mixture HM-PAO but identical with Ceretec, a dl-HM-PAO kit manufactured by Amersham Inc., England. The primary clinical applications for gamma CBF SPECT imaging demonstrated a satisfactory result.

Animals↗

[Lipoprotein (alpha) as a risk factor for myocardial infarction].

Serum lipoprotein (alpha) [Lp(alpha)]was determined in 105 cases of myocardial infarction survivors (MIS). Lp(alpha) level in MIS was much more elevated as compared with that in healthy subjects and in a hypertension group. Lp(alpha) had no relation with apolipoprotein B and AI, cholesterol, triglyceride and high density lipoprotein cholesterol. It may be a significant and independent risk factor for coronary heart disease.

Aged↗

[Studies on synthesis and anticonvulsant activity of 3-GABA derivatives of 6-(substituted-phenyl) pyridazines].

In recent years considerable emphasis has been placed on the hypothesis that enhancement of GABA transmission could be beneficial in some types of epilepsy. The alpha-(aryl)-4-morpholineacetonitrile obtained by the interaction of aryl aldehydes, morpholine and potassium cyanide, have been used to synthesize 3-(aroyl)-propionic acids and esters by 1,4-additions to acrylonitrile or acrylic ester. 3-(Aroyl) propionic acids reacting with hydrazine can yield 6-aryl-4,5-dihydro-3(2H) pyridazinones which are dehydrogenated by bromine (via bromination dehydrobromination) to give 6-aryl-3(2H) pyridazinones. The latter compounds were converted into 3-(N-GABA)-6-(substitutedphenyl) pyridazines and 3-(N-butyryllactamyl)-6-(substitutedphenyl) pyridazines by the chlorination (by means of phosphorus oxychloride) and then reaction with GABA. By this method seventeen 3-GABA derivatives of 6-(substituted-phenyl)pyridazines were synthesized. The anticonvulsant activity (MES) of these compounds were also tested. 3-(N-GABA)-6-(2',4'-dichloro)phenylpyridazine; potent anticonvulsant (ED50 = 21.05 mg/kg).

Animals↗

[Studies on synthesis, anticonvulsant activity and the structure--activity relationships of 6-(substituted phenyl)-3 (2H) pyridazinones].

In searching for effective anticonvulsant agent fourteen 6-(substituted-phenyl)-4,5-dihydro-3 (2H) pyridazinones and fifteen 6-(substitutedphenyl)-3 (2H) pyridazinones have been synthesized and screened in mice for their ability to antagonize maximal electroshock seizure (MES). The ED50 values showed that 6-(2',4'-dichlorophenyl)-3 (2H) pyridazinone was the most potent anticonvulsant in these compounds. The structure--activity relationships in these two series were examined. We came to the conclusion that the higher is the hydrophobic parameter pi of the substituent on phenyl ring, the more potent anticonvulsant is the compound. And also, only the compounds with an electronwithdrawing substituent on the phenyl ring exhibited appreciable anticonvulsant activity.

Animals↗

Enhanced skin permeability for transdermal drug delivery: physiopathological and physicochemical considerations.

To deliver drugs through the skin for systemic medication, the skin permeability needs enhancing by either modifying the drug molecules, or applying skin permeation enhancers to reduce the barrier property of the skin. Traditionally, the enhancement of skin permeability is considered as the result from the improvement of the lipophilicity of drugs and the partition of drugs into the skin, or from the direct actions of skin permeation enhancers on the chemical structure and/or composition of lipids and proteins in the stratum corneum. However, on the other hand, the skin also responds to drugs and/or skin permeation enhancers physiopathologically via its inflammatory and immune reaction. The physiopathological responses of the skin can also induce the changes in the chemical structure and composition of lipids and proteins in the skin. Therefore, the possible role of physiopathological responses of the skin in the enhanced skin permeability should be concerned.

Administration, Cutaneous↗