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Biomedical subjects

L Ji

Publications and source records attributed to L Ji.

At least 91 records · Page 5Linked to original sources
PubMed1995

Induction of apoptotic DNA fragmentation and cell death by natural ceramide.

We have found that a solvent mixture of ethanol and dodecane was able to disperse natural ceramide (Cer) into aqueous solution. In U937 cells, addition of natural Cer to medium caused a characteristic pattern of DNA fragmentation, which is indistinguishable from that caused by TNF alpha. The effective concentration of Cer is as low as 25 nM. The present study provides direct evidence that natural Cer functions as a second messenger mediating TNF alpha-induced DNA fragmentation. The use of this solvent to deliver hydrophobic natural Cer to cells will contribute to the elucidation of the biological function of Cer.

Apoptosis↗
PubMed1995

The hydrolysis of cell surface glycosphingolipids by endoglycoceramidase reduces epidermal growth factor receptor phosphorylation in A431 cells.

This paper presents a new method to evaluate the biological significance of glycosphingolipids (GSLs) using a GSL-specific enzyme, endoglycoceramidase (EGCase), by which GSL-sugar chains are removed from the cell surface of living cells. In this report, the effects of EGCase on epidermal growth factor (EGF)-dependent tyrosine-specific EGF receptor (EGFR) phosphorylation of A431 cells are described. After treatment of A431 cells with EGCase II (20 mU/ml) in the presence of the activator for 12 h, all acidic GSLs tested were reduced to approximately 70% of control, but no hydrolysis occurred on Gal alpha 1,4Gal beta 1,4Glc beta 1,1Cer (Gb3Cer) and GalNAc beta 1,3Gal alpha 1,4Gal beta 1,4Glc beta 1,1Cer (Gb4Cer). In plasma membrane fractions of A431 cells, the reduction of gangliosides by EGCase II was found to be much faster than that of intact cells and reached 54.8% reduction of total gangliosides after 2 h incubation with the enzyme. EGF-dependent phosphorylation of EGFR of A431 cells was inhibited by the reduction of cell surface GSLs by EGCase when either intact A431 cells or their plasma membrane fractions were used, while EGF binding to their receptors was not changed. Neither hydrolysis of cell surface GSLs nor reduction of EGFR phosphorylation occurred when A431 cells were incubated with the activator or EGCase alone. The exogenous addition of ceramides or sphingosines, and treatment of cell membranes with sphingomyelinase, had no effect on the EGFR phosphorylation of purified membrane fractions, while the inhibitory effect of EGCase II on EGFR phosphorylation was restored by the addition of GM3-sugar chains, but not by lactose or sialic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1995

Trinucleotide repeats at the rad locus. Allele distributions in NIDDM and mapping to a 3-cM region on chromosome 16q.

A 10-allele polymorphism was identified in rad (ras associated with diabetes), a gene that is overexpressed in non-insulin-dependent diabetes mellitus (NIDDM) muscle. The polymorphism, designated RAD1, consists of a variable number of trinucleotide repeats (GTT and ATT) located in the poly(A) region of an intronic Alu sequence. Based on the number of GTT and ATT repetitions, the alleles can be grouped into four classes (I-IV). RAD1 allele frequencies were determined in 210 NIDDM patients and 133 nondiabetic control subjects, all Caucasians. One allele (number 8, class III) accounted for > 80% of the chromosomes in both groups. However, an excess of minor alleles, all belonging to class I, II, or IV, was observed among NIDDM chromosomes (P < 0.025), suggesting a possible association between RAD1 and NIDDM predisposition. To promote further studies to test the hypothesis that genetic variability at the rad locus contributes to NIDDM, we mapped rad on the human genome. Using the fluorescence in situ chromosomal hybridization technique, rad was unequivocally assigned to chromosomal band 16q22. In families that were informative for RAD1, the rad locus was mapped within a 3-cM region defined by the markers D16S265, D16S186, and D16S397 (logarithm of odds scores = 10.08, 10.9, and 10.84 at recombination fractions of 0.024, 0.001, and 0.03, respectively). The high degree of heterozygosity of these markers will allow large-scale family studies to be performed to test the presence of linkage between rad and NIDDM.

Alleles↗
PubMed1994

Fully automatic chromosome segmentation.

This paper is concerned with automatic segmentation of high resolution digitized metaphases. This includes automatic detection and rejection of interphase nuclei, stain debris, and other "noise"; automatic detection and segmentation of touching and overlapping chromosome clusters; and automatic rejection of cells which are evaluated as being incomplete, or incorrectly segmented, or where the cell is otherwise unsuitable for further analysis. In this paper, a rule-based approach is described which treats the cell as a whole rather than as a series of individual chromosomes or clusters. The rules adapt classification and segmentation parameters for each cell. Initially, different sets of parameters are chosen according to the staining method of the cells, and the goal of the segmentation. A chromosome number predictor is used to guide the adaptation of the parameters and to estimate the performance. The adaptation is iterative, and the self-adjustment will stop when either a satisfactory result is achieved or if the cell is rejected. The method was implemented on both a Sun workstation and a Cytoscan, a commercial machine for chromosome analysis. Seven hundred and thirteen cells from real data have been tested. A success rate of 90-95% has been achieved. The procedure has been implemented in an automatic aberration scoring system for routine use.

Chromosome Aberrations↗
PubMed1994

Automatic fluorescence metaphase finder speeds translocation scoring in FISH painted chromosomes.

A fluorescence metaphase finder was constructed with commercially available hardware and a standard Unix workstation. Its accuracy was measured in terms of the number of false positive and false negative detected metaphases on a variety of different slide preparations. The metaphase finder was used in a translocation scoring experiment in which metaphase preparations of human peripheral blood lymphocytes were hybridized with whole chromosome probes to chromosomes #1, #2, and #4. The automatic finder presented metaphases to the cytogeneticist, centered in the eyepieces at x63. The cytogeneticist's scores of analyzable metaphases and of painted chromosomes involved in rearrangements were recorded. The time for the analysis was recorded and compared to the time to analyze a similar number of cells in a purely visual experiment in which the cytogeneticist scanned for cells and analyzed them, both at x63. The results showed that, neglecting the machine time spent scanning unattended, the amount of time required for the analysis was reduced by a factor of three. Furthermore, in this experiment the metaphase finder found more scorable metaphases than the cytogeneticist found by visual scanning. Machine-assisted scoring had additional, less quantifiable, benefits; notably that digital images of metaphases sometimes assisted the analysis of chromosome rearrangements, that cells could be revisited easily, and that the analysis was much less fatiguing.

Cytogenetics↗
PubMed1994

Cloning and sequence analysis of a cDNA encoding ferric leghemoglobin reductase from soybean nodules.

A cDNA encoding soybean (Glycine max [L.] Merr) ferric leghemoglobin reductase (FLbR), an enzyme that is postulated to play an important role in maintaining leghemoglobin in its functional ferrous state, has been cloned and characterized. A group of highly degenerate oligonucleotides deduced from the N-terminal amino acid sequence of FLbR was used to prime the polymerase chain reaction (PCR) on soybean nodule mRNA and cDNA. A full-length clone of FLbR cDNA was isolated by screening a lambda gt11 soybean nodule cDNA library using the specific PCR-amplified FLbR cDNA fragment as a probe. The cDNA contained about 1.8 kb and had a coding sequence for 523 amino acids with a predicted molecular mass of 55,729 D, which included a putative 30-residue signal peptide and a 493-residue mature protein. Computer-aided analysis of the deduced FLbR amino acid sequence showed considerable homology (varied from 20-50% with enzymes and species) to dihydrolipoamide dehydrogenase (EC 1.8.1.4), glutathione reductase (EC 1.6.4.2), mercuric reductase (EC 1.16.1.1), and trypanothione reductase (EC 1.6.4.8) in a superfamily of pyridine nucleotide-disulfide oxidoreductases from various organisms. Northern blot analysis using FLbR cDNA as a probe showed that the FLbR gene was expressed in soybean nodules, leaves, roots, and stems, with a greater level of expression in nodules and leaves than in roots and stems. Southern blot analysis of the genomic DNA showed the presence of two homologous FLbR genes in the soybean genome.

Amino Acid Sequence↗
PubMed1994

NF-kappa B sites function as positive regulators of expression of the translocated c-myc allele in Burkitt's lymphoma.

An in vivo footprint over a potential NF-kappa B site in the first exon of the c-myc gene has been identified on the translocated allele in the Ramos Burkitt's lymphoma cell line. The potential NF-kappa B site in the 5' flanking sequence of c-myc was found to be occupied on the translocated allele in the Raji Burkitt's cell line. Electrophoretic mobility shift assays with each of these sequences demonstrated complexes with mobilities identical to those of the NF-kappa B site from the kappa light-chain gene. A supershift was obtained with anti-p50 antibody with the exon site. The upstream-site shift complex disappeared with the addition of anti-p50 antibody. Binding of NF-kappa B proteins to the c-myc exon and upstream sites was demonstrated by induction of binding upon differentiation of pre-B 70Z/3 cells to B cells. UV cross-linking experiments revealed that a protein with a molecular mass of 50 kDa bound to the exon and upstream sites. Transfection experiments with Raji cells demonstrated that both sites functioned as positive regulatory regions, with a drop in activity level when either site was mutated. Access to these sites is blocked in the silent normal c-myc allele in Burkitt's lymphoma cells, while Rel family proteins bind to these sites in the translocated allele. We conclude that the two NF-kappa B sites function as positive regulatory regions for the translocated c-myc gene in Burkitt's lymphoma.

B-Lymphocytes↗
PubMed1994

[Estimation of age from epiphyseal union degrees of the sternal end of the clavicle].

The sternal ends of right clavicles of Japanese aged 13-31 years (n = 54) autopsied during 1982-1992 were observed for determining degree of epiphyseal union to establish a criterion for age estimation. As the degree of union 5 stages (McKern and Stewart, 1957) were applied to samples: Stage 0; without any union between the trunk and the epiphyseal cap, stage 1; between stage 0 and stage 2, stage 2; half united, stage 3; between stage 2 and stage 4, and stage 4; completely united. As results, in females union appears to proceed faster than in males. There were cases in which union reached stage 4 in younger ages. As a criterion for age estimation it is proposed at present that in both sex, when union is in stage 0, age is certainly estimated to be less than 22 years old and in stage 4, more than 19 years old. Comparing the present data with the investigation about American males by McKern and Stewart (1957), in Japanese males union proceeds more fast than them. The authors realized that the correct criteria should be used in age estimation on a sample belonging to the same race and to the times. The clavicles in skeletal remains tend to be preserved outdoors and are suitable for estimating age from adolescence to about 30 years old. Therefore the present criterion would be very useful in districts such as Hokkaido where skeletal remains are commonly found.

Adolescent↗
PubMed1993

ABO blood grouping on dental tissue.

Twenty-five permanent teeth, including eight carious ones whose pulp cavities had been exposed, were used for this research 3-5 weeks after extraction. Phosphate-buffered saline (PBS, at pH 7.2) was employed to extract ABO blood group substance from tooth powder. ABO grouping was performed on blood-stained compresses from the extraction wound (as controls), tooth fragment, tooth powder, and cotton fibers immersed in PBS extract by absorption-elution (AE) technique and on the PBS extracts by the two-dimensional absorption-inhibition (2-D AI) technique. It was found that blood grouping in PBS extracts by 2-D AI yielded reliable results: no false positive results, and a high rate of correct grouping, (24/25), while blood grouping on other dental materials, such as tooth fragments, tooth powders, immersed fibers, by AE gave an unacceptable rate of false positive/negative results.

ABO Blood-Group System↗
PubMed1992

Surfactant-induced sealing of electropermeabilized skeletal muscle membranes in vivo.

Victims of major electrical trauma frequently suffer extensive skeletal muscle and nerve damage, which is postulated to be principally mediated by electroporation and/or thermally driven cell membrane permeabilization. We have investigated the efficacy of two blood-compatible chemical surfactants for sealing electroporated muscle membranes. In studies using cultured skeletal muscle cells, poloxamer 188 (P188; an 8.4-kDa nonionic surfactant) blocks, and neutral dextran (10.1 kDa) substantially retards, carboxyfluorescein release from electropermeabilized cell membranes. To test whether P188 administered intravenously could have the same therapeutic effect in vivo, the rat biceps femoris muscle flap attached by its arteriovenous pedicle was electropermeabilized until its electrical resistivity dropped to 50% of the initial value. P188 (460 mg/kg) administered intravenously 20 min postshock restored the resistivity to 77% of the initial value. When P188 was administered intravenously 5 min before shock, a dose-dependent impedance recovery rate was observed. Neither neutral dextran (460 mg/kg) nor sterile saline was effective. Histopathologic studies indicated that postshock poloxamer administration reduced tissue inflammation and damage in comparison with dextran-treated or control tissues. Electrophysiologic evidence of membrane damage was not observed in flaps of animals pretreated with poloxamer. These results suggest that it may be possible to seal in vivo tissue membranes injured by electrical, thermal, or other membrane-damaging forces.

Animals↗
PubMed1992

Involvement of Molecular Oxygen in the Enzyme-Catalyzed NADH Oxidation and Ferric Leghemoglobin Reduction.

Ferric leghemoglobin reductase (FLbR) from soybean (Glycine max [L.] Merr) nodules catalyzed oxidation of NADH, reduction of ferric leghemoglobin (Lb(+3)), and reduction of dichloroindophenol (diaphorase activity). None of these reactions was detectable when O(2) was removed from the reaction system, but all were restored upon readdition of O(2). In the absence of exogenous electron carriers and in the presence of O(2) and excess NADH, FLbR catalyzed NADH oxidation with the generation of H(2)O(2) functioning as an NADH oxidase. The possible involvement of peroxide-like intermediates in the FLbR-catalyzed reactions was analyzed by measuring the effects of peroxidase and catalase on FLbR activities; both enzymes at low concentrations (about 2 mug/mL) stimulated the FLbR-catalyzed NADH oxidation and Lb(+3) reduction. The formation of H(2)O(2) during the FLbR-catalyzed NADH oxidation was confirmed using a sensitive assay based on the fluorescence emitted by dichlorofluorescin upon reaction with H(2)O(2). The stoichiometry ratios between the FLbR-catalyzed NADH oxidation and Lb(+3) reduction were not constant but changed with time and with concentrations of NADH and O(2) in the reaction solution, indicating that the reactions were not directly coupled and electrons from NADH oxidation were transferred to Lb(+3) by reaction intermediates. A study of the affinity of FLbR for O(2) showed that the enzyme required at least micromolar levels of dissolved O(2) for optimal activities. A mechanism for the FLbR-catalyzed reactions is proposed by analogy with related oxidoreductase systems.

Journal Article↗
PubMed1992

[Chemical studies on essential oils from 6 Artemisia species].

The constituents of the essential oils obtained from the leaves of Artemisia argyi, A. argyi cv.qiai, A. lavandulaefolia, A. mongolica, A. princeps and A. argyi var. gracilis were analysed by GC-MS. 96 compounds including alpha-thujene, 1,8-cineole, camphor and artemisia alcohol, etc. were identified. Their percentages in the oils were given.

Drugs, Chinese Herbal↗