Search PubMed⌕ Search

Biomedical subjects

L Shi

Publications and source records attributed to L Shi.

At least 181 records · Page 10Linked to original sources
PubMed1998

Characteristics and composition of peanut oil prepared by an aqueous extraction method.

Peanut is one of the crops being tested for NASA's Advanced Life Support (ALS) program for future long-duration human space missions. The ALS program is developing an integrated system for biomass (food, oxygen) production and resource recycling. Oil will be used mainly for cooking and its availability is important for food preparation. Peanut seeds contain 40-50% oil and hence are considered an excellent source of oil. In the ALS environment, a simple, compact, and energy-efficient system is needed. The feasibility of such a method, peanut oil preparation by water extraction, was investigated. The results indicated the important processing conditions to be: a peanut particle size of 0.02 cm or less, a pH of 4, simmering for 20 min plus churning at 65 degrees C for a few hours, and a centrifugation at 6000 x gn to separate the oil. The oil recovery yield was about 80%. The saponification value, specific gravity, refractive index, and viscosity were similar to that of commercial peanut oil except the color was lighter for the water-extracted oil. Gas and thin-layer chromatographic analyses showed that fatty acid and lipid profiles were similar to the commercial peanut oil. The only difference observed was that the oil prepared by the aqueous method had lower linoleic and higher oleic acids than the commercial peanut oil. The oil prepared by this aqueous method appeared to be of high quality.

Arachis↗
PubMed1998

[RP-HPLC determination of water-soluble active constituents and oleanolic acid in the fruits of Ligustrum lucidum Ait. collected from various areas].

The contents of p-hydroxyphenethyl-beta-D-glucoside, specnuezhenide and oleanolic acid in the fruits of Ligustrum lucidum collected from various areas in China were determined by reverse phase high performance liquid chromatography. The results could be used to evaluate the quality of the crude drug more comprehensively.

Chromatography, High Pressure Liquid↗
PubMed1998

[Parapharyngeal space neoplasms].

OBJECTIVE: To study parapharyngeal space (PPS) neoplasms which are rarely seen clinically. METHODS: A retrospective review was made of 59 patients with PPS neoplasm operated on from 1986 to July, 1997 in our institution. RESULTS: Neurogenic tumors were the most common neoplasms, which constituted about 60 percent in the primary parapharyngeal space neoplasms. High-resolution computed tomography or magnetic resonance imaging was essential for diagnosis and presurgical planning. The transcervical approach was the preferred procedure for 75% benign parapharyngeal tumors. Middle mandibulotomy was used in 3 cases, including 2 small tumors confined to the superior aspect of the PPS and 1 carotid body tumor which extended to the skull base. Lateral skull base approach was utilized for 1 schwannoma originating in the jugular foramen with extension into the PPS. CONCLUSIONS: We believe that transoral approach can be used for small tumors and transparotid approach may be especially indicated for removal of deep lobe parotid tumors with extension to the PPS. Middle mandibulotomy is a safe and efficacious approach for the removal of special PPS neoplasms.

Adenoma, Pleomorphic↗
PubMed1998

[The determination of ligustilide in Ligusticum chuanxiong Hort. by supercritical fluid extraction].

In this study, a systematic method was used to optimize the supercritical fluid extraction (SFE) of ligustilide in Ligusticum chuanxiong Hort. Overall five variables (pressure, temperature, static extracting time, modifier concentration and CO2 dynamic extracting volume) were considered. To reduce the loss of volatile substance, a solid-liquid trap was developed for SFE collection. Comparisons were made on the solvent trap for SFE. The extracts were analyzed by high performance liquid chromatography (HPLC) with ultraviolet absorbance detection. The recoveries of 99.34% (RSD 1.70%) and 92.11% (RSD 5.72%) were achieved for solid-liquid trap and solvent trap, respectively. SFE conditions: temperature 40 degrees C, pressure 27.6 MPa, static extraction 3 min, dynamic extraction 7 ml and 0.1 ml CHCl3 as modifier. HPLC conditions: The HPLC column (3.9 mm x 150 mm) was packed with Nova-Pak C18(4 microns). Naphthalene was used as internal standard. The mobile phase was methanol--10% isopropyl alcohol solution (53:47 v/v). The detection wavelength was 280 nm and the flow rate was 0.8 ml.min-1.

4-Butyrolactone↗
PubMed1998

[Determination of Y, Ce, Ba and Cu in Y(1-x) Ce(x),Ba(2)Cu(3)O(y), using x-ray fluorescence fundamental parameter method].

The determination of Y, Ce, Ba and Cu in a series of Y(1-x)Ce(x)Ba(2)Cu(3)O(y) samples has been performed using X-ray fluorescence fundamental parameter method. The composition is given in atomic percentage. The results agree well with those obtained by ICP. It is shown that this method is appropriate for the determination of compositions of the high temperature superconductors. In addition, the influence of oxygen on analytical elements has been discussed in this paper. The fraction of the matrix total mass absorption that is associated with oxygen for each analytical line can not be larger than 3.44%. The determined composition of the samples show different from their nominal composition,which may affect the properties of high temperature superconductor.

English Abstract↗
PubMed1998

Universal cytochrome b primers facilitate intraspecific studies in molluscan taxa.

We describe the construction of amplification primers designed to target a portion of the mitochondrial cytochrome b locus in a variety of molluscan taxa. Combinations of two sets of primers successfully amplified cytochrome b from several species of gastropods, bivalves, and cephalopods. Sequence analysis of these amplified products revealed nucleotide diversity in small samples within several of these taxa. We discuss the utility of these primer sets for studies of intraspecific phylogeny in mollusks and potentially other invertebrates.

Amino Acid Sequence↗
PubMed1997

The E1B 19K/Bcl-2-binding protein Nip3 is a dimeric mitochondrial protein that activates apoptosis.

Nip3 (nineteen kD interacting protein-3) is an E1B 19K and Bcl-2 binding protein of unknown function. Nip3 is detected as both a 60- and 30-kD protein in vivo and in vitro and exhibits strong homologous interaction in a yeast two-hybrid system indicating that it can homodimerize. Nip3 is expressed in mitochondria and a mutant (Nip3(163)) lacking the putative transmembrane domain and COOH terminus does not dimerize or localize to mitochondria. Transient transfection of epitope-tagged Nip3 in Rat-1 fibroblasts and MCF-7 breast carcinoma induces apoptosis within 12 h while cells transfected with the Nip3(163) mutant have a normal phenotype, suggesting that mitochondrial localization is necessary for induction of cell death. Nip3 overexpression increases the sensitivity to apoptosis induced by granzyme B and topoisomerase I and II inhibitors. After transfection, both Nip3 and Nip3(163) protein levels decrease steadily over 48 h indicating that the protein is rapidly degraded and this occurs in the absence of cell death. Bcl-2 overexpression initially delays the onset of apoptosis induced by Nip3 but the resistance is completely overcome in longer periods of incubation. Nip3 protein levels are much higher and persist longer in Bcl-2 expressing cells. In conclusion, Nip3 is an apoptosis-inducing dimeric mitochondrial protein that can overcome Bcl-2 suppression.

Adenovirus E1B Proteins↗
PubMed1997

Interneuron migration from basal forebrain to neocortex: dependence on Dlx genes.

Although previous analyses indicate that neocortical neurons originate from the cortical proliferative zone, evidence suggests that a subpopulation of neocortical interneurons originates within the subcortical telencephalon. For example, gamma-aminobutyric acid (GABA)-expressing cells migrate in vitro from the subcortical telencephalon into the neocortex. The number of GABA-expressing cells in neocortical slices is reduced by separating the neocortex from the subcortical telencephalon. Finally, mice lacking the homeodomain proteins DLX-1 and DLX-2 show no detectable cell migration from the subcortical telencephalon to the neocortex and also have few GABA-expressing cells in the neocortex.

Animals↗
PubMed1997

Borna disease virus P-protein is phosphorylated by protein kinase Cepsilon and casein kinase II.

Borna disease virus (BDV) is a newly classified nonsegmented negative-strand RNA virus (order of Mononegavirales) that persistently infects specific brain regions and circuits of warm-blooded animals to cause behavioral disturbances. Viruses within the order of Mononegavirales have phosphoproteins that typically serve as transcription factors and are modulated in functional activity through phosphorylation. To identify the kinases involved in BDV phosphoprotein (BDV-P) phosphorylation, in vitro phosphorylation assays were performed using recombinant phosphoprotein produced in Escherichia coli as substrate and cytoplasmic extracts from a rat glioma cell line (C6) or rat brain extracts as sources of kinase activity. These experiments revealed that BDV-P was phosphorylated predominantly by protein kinase C (PKC) and to a lesser extent by casein kinase II. Partial purification of the PKC from rat brain extract suggested that the BDV-P phosphorylating kinase is PKCepsilon. A role for PKC phosphorylation in vivo was confirmed by using the PKC-specific inhibitor GF109203X. Furthermore, peptide mapping studies indicated that BDV-P is phosphorylated at the same sites in vitro as it is in vivo. Mutational analysis identified Ser26 and Ser28 as sites for PKC phosphorylation and Ser70 and Ser86 as sites for casein kinase II phosphorylation. The anatomic distribution of PKCepsilon in the central nervous system may have implications for BDV neurotropism and pathogenesis.

Animals↗
PubMed1997

Activation of caspase-2 in apoptosis.

Members of the CED-3/interleukin-1beta-converting enzyme (ICE) protease (caspase) family are synthesized as proforms, which are proteolytically cleaved and activated during apoptosis. We report here that caspase-2 (ICH-1/NEDD-2), a member of the ICE family, is activated during apoptosis by another ICE member, a caspase-3 (CPP32)-like protease(s). When cells are induced to undergo apoptosis, endogenous caspase-2 is first cleaved into three fragments of 32-33 kDa and 14 kDa, which are then further processed into 18- and 12-kDa active subunits. Up to 50 microM N-acetyl-Asp-Glu-Val-Asp-aldehyde (DEVD-CHO), a caspase-3-preferred peptide inhibitor, inhibits caspase-2 activation and DNA fragmentation in vivo, but does not prevent loss of mitochondrial function, while higher concentrations of DEVD-CHO (>50 microM) inhibit both. In comparison, although the activity of caspase-3 is very sensitive to the inhibition of DEVD-CHO (<50 nM), inhibition of caspase-3 activation as marked by processing of the proform requires more than 100 microM DEVD-CHO. Our results suggest that the first cleavage of caspase-2 is accomplished by a caspase-3-like activity, and other ICE-like proteases less sensitive to DEVD-CHO may be responsible for activation of caspase-3 and loss of mitochondrial function.

Apoptosis↗
PubMed1997

Monoclonal antibodies specific to the acute lymphoblastic leukemia t(1;19)-associated E2A/pbx1 chimeric protein: characterization and diagnostic utility.

Nonrandom chromosomal abnormalities are found in most human malignancies, particularly leukemias and lymphomas. A characteristic t(1;19) (q23;p13.3) chromosomal translocation is detected in 5% of childhood acute lymphoblastic leukemia (ALL) cases. This translocation results in the formation of a fusion gene, which leads to the expression of an oncogenic E2A/pbx1 protein. Breakpoints in the E2A gene almost invariably occur within a single intron, and the identical portion of PBX1 is joined consistently to exon 13 of E2A in fusion mRNA. In this article, we report the development of monoclonal antibodies against E2A/pbx1 fusion protein using a specific peptide that corresponds to the junction region of the protein. The obtained antibodies recognize specifically the chimeric E2A/pbx1 fusion protein and lack cross-reactivities with E2A and pbx1. Immunohistochemical staining and flow cytometric studies show that these antibodies can distinguish t(1;19)-positive from t(1;19)-negative leukemic cells. These results indicate that the obtained E2A/pbx1-specific monoclonal antibodies might prove to be valuable diagnostic reagents and important tools for elucidating the mechanisms involved in oncogenesis and progression of t(1;19)-positive childhood ALL.

Amino Acid Sequence↗
PubMed1997

Granzyme B (GraB) autonomously crosses the cell membrane and perforin initiates apoptosis and GraB nuclear localization.

Granzyme B (GraB) induces apoptosis in the presence of perforin. Perforin polymerizes in the cell membrane to form a nonspecific ion pore, but it is not known where GraB acts to initiate the events that ultimately lead to apoptosis. It has been hypothesized that GraB enters the target cell through a perforin channel and then initiates apoptosis by cleaving and activating members of the ICE/Ced-3 family of cell death proteases. To determine if GraB can enter the cell, we treated YAC-1 or HeLa cells with FITC-labeled GraB and measured intracellular fluorescence with a high sensitivity CCD camera and image analyzer. GraB was internalized and found diffusely dispersed in the cell cytoplasm within 10 min. Uptake was inhibited at low temperature (4 degrees C) and by pretreatment with metabolic inhibitors, NaF and DNP, or cytochalasin B, a drug that both blocks microfilament formation, and FITC-GraB remained on the cell membrane localized in patches. With the simultaneous addition of perforin and FITC-GraB, no significant increase in cytoplasmic fluorescence was observed over that found in cells treated only with FITC-GraB. However, FITC-GraB was now detected in the nucleus of apoptotic cells labeling apoptotic bodies and localized areas within and along the nuclear membrane. The ability of GraB to enter cells in the absence of perforin was reexamined using anti-GraB antibody immunogold staining of ultrathin cryosections of cells incubated with GraB. Within 15 min, gold particles were detected both on the plasma membrane and in the cytoplasm of cells with some gold staining adjacent to the nuclear envelope but not in the nucleus. Cells internalizing GraB in the absence of perforin appeared morphologically normal by Hoechst staining and electron microscopy. GraB directly microinjected into the cytoplasm of B16 melanoma cells induced transient plasma membrane blebbing and nuclear coarsening but the cells did not become frankly apoptotic unless perforin was added. We conclude that GraB can enter cells autonomously but that perforin initiates the apoptotic process and the entry of GraB into the nucleus.

Animals↗
PubMed1997

pp1-cyano2, a protein serine/threonine phosphatase 1 gene from the cyanobacterium Microcystis aeruginosa UTEX 2063.

Polymerase chain reaction (PCR) products similar to protein serine/threonine family I phosphatase genes were identified in five strains of cyanobacteria from three species. The gene for one of these protein phosphatase PCR products, pp1-cyano2 from Microcystis aeruginosa UTEX 2063, was cloned and sequenced. The deduced protein sequence PP1-cyano2 contains 264 amino acid residues ( approximately 30.3 kDa). In its N-terminal region, PP1-cyano2 had a GDXXHG(X)nGDXXDRG(X)nGNHE (nP23) sequence that is well-conserved in all protein serine/threonine family I phosphatases. Of 19 amino acid residues important for either metal binding, structure of the active site, or catalysis in eukaryotic PP1, 18 were present in PP1-cyano2. Reverse-transcription-PCR results showed that pp1-cyano2 was expressed under laboratory culture conditions.

Amino Acid Sequence↗
PubMed1997

A monoclonal antibody shows discrete cellular and subcellular localizations of mGluR1 alpha metabotropic glutamate receptors.

The metabotropic glutamate receptor, mGluR1 alpha, is postsynaptic in excitatory synapses in many populations of neurons and mediates long-term responses. The present study defines the distribution of this receptor using a new, highly specific monoclonal antibody to mGluR1 alpha. Overall distribution of immunostaining was similar to that described previously with polyclonal antibodies, including prominent staining in the olfactory bulb, interneurons of the CA1 hippocampus stratum oriens/alveus, globus pallidus, thalamus, Purkinje cells and in cells of the outer dorsal cochlear nucleus and with little or low staining in principal cells of the cerebral cortex and hippocampus. Interestingly, the well-known association of mGluR1 alpha receptors with neocortical interneurons was even more prevalent than previously noted with polyclonal antibodies. Ultrastructural studies in the hippocampus and cerebellum showed dense immunoperoxidase staining in postsynaptic membranes and densities and in perisynaptic and extrasynaptic membranes, as well as substantial cytoplasmic staining associated with organelles, especially the endoplasmic reticulum.

Animals↗
PubMed1997

Developmental expression of a DNA repair gene in Arabidopsis.

Exposure to alkylating agents results in the formation of a wide variety of DNA damage products. One of these, 3-methyladenine (3-mAde), is lethal if left unrepaired. The 3-methyladenine glycosylase (aMAG) gene of Arabidopsis thaliana is required for base excision repair of this lesion, and probably shares the ability of other 3-mAde glycosylases to recognize and excise a broad spectrum of damaged bases. Given the fact that DNA damage products can act as blocks to both DNA and RNA synthesis, one would expect that this protein should be expressed to some degree in all living cells. Using a DIG-labeled aMAG antisense RNA as a probe, we have investigated the developmental and tissue-specific expression of this repair gene. We found that the gene is preferentially expressed in meristematic tissue, the developing embryo and endosperm, and organ primordia. This pattern of expression is consistent with a requirement for expression in rapidly dividing tissues. However, high levels of expression were also observed in growing leaves, a tissue that is undergoing a relatively low rate of cell division. This result suggests that 3-mAde glycosylase is required not only for DNA replication, but also for cell growth.

Arabidopsis↗
PubMed1997

The STR120 satellite DNA of soybean: organization, evolution and chromosomal specificity.

A highly repeated DNA sequence family, STR120, with tandemly arranged repetitive units (monomers) of approximately 120bp, has been identified in soybean [Glycine max (L.) Merr.]. Five related clones showing tandem repeats of a 120-bp-long monomer were isolated from a soybean genomic library. Results of Southern blotting experiments using three of the clones as probes onto genomic DNA digested with different restriction enzymes were in agreement with a tandem arrangement of these sequences in the genome. A total of 12 monomers were sequenced, showing considerable sequence heterogeneity. A consensus sequence of 126 bp was obtained that exhibits an average similarity of 81% to the sequenced units. In three of the clones identified, neighbouring units are significantly more similar to each other than to units from different clones; in the remaining two clones, however, similarity between the two units observed is low (70%), while the overall similarity between the two clones is high (95%). This indicates that in these cases the repetitive unit may be the dimer rather than the monomer. Based on the presence of direct repeats within each monomer, we suggest that the 120-bp monomer may itself have evolved by duplication of an ancestral 60-bp unit. The STR120 family distribution is limited to annual soybeans and is not found, at least at high-copy number, in related perennial soybeans or other members of the tribe Phaseolae. Fluorescence in situ hybridization (FISH) to metaphase chromosomes using four of the clones as probes shows that the number of chromosomal locations differs depending on the stringency conditions and goes from two to eight when the stringency is progressively lowered. The estimated copy number for one of the clones is from 5000 to 10000, but this may just represent a lower boundary for the whole family in consideration of the high sequence divergence observed within the family. FISH and sequence analysis therefore indicate that different subfamilies as well as higher-order repeat units are present in the STR120 family, very much like those in primate alpha satellite DNA, and that some of the subfamilies seem to exhibit divergence on a chromosomal basis.

Base Sequence↗
PubMed1997

B chromosome behavior in maize pollen as determined by a molecular probe.

The B chromosomes of maize typically undergo nondisjunction during the second microspore division (generative cell division). When the microspore nucleus contains only one B chromosome, two kinds of sperm result, one with two B chromosomes and one with no B chromosomes. The sperm with the B chromosomes preferentially fertilizes the egg cell. Previous studies of these phenomena have been limited to genetic analysis and chromosome spreads. In this study we show that a B chromosome-specific probe can be used with fluorescence in situ hybridization (FISH) analysis to detect the presence, location, and frequency of B chromosomes in intact interphase nuclei within mature pollen of maize. Using genetic line TB-10L18, our results indicate that nondisjunction of the B centromere occurs at an average frequency of 56.6%, based on four plants and 1306 pollen grains analyzed. This is consistent with the results of genetic studies using the same B-A translocation. In addition, our results suggest that B chromosome nondisjunction can occur during the first microspore division. Spatial distribution of the B chromosome-specific probe appears to be largely confined to one tip of the sperm nucleus, and a DNA fragment found outside the pollen nuclei often hybridizes to the B chromosome-specific probe.

Biotinylation↗