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Biomedical subjects

X Yuan

Publications and source records attributed to X Yuan.

At least 109 records · Page 6Linked to original sources
PubMed1998

Which vertebrae should be assessed in diagnosing osteoporosis by plain radiography? Comparative study of radiographic findings and bone mineral density measured by dual energy X-ray absorptiometry.

In 1990, the Ministry of Health and Welfare of Japan advocated a criterion for the diagnosis radiographic bone atrophy in lumbar vertebrae. We carried out a comparative study of this criterion (i.e. , radiographic bone atrophy grading) and bone mineral density measured by posteroanterior and lateral dual energy X-ray absorptiometry. We investigated the second to fourth lumbar vertebrae of 47 postmenopausal women (mean age, 67.2 years; range, 57-82 years), to determine which vertebra would most accurately indicate osteoporosis. A significant difference in bone mineral density (P < 0.01) was found between each grade of radiographic bone atrophy in all of the second, third, and fourth vertebrae examined. The highest correlation (r = 0.714) was found between the radiographic grades and the bone mineral density on lateral dual energy X-ray absorptiometry of the third lumbar vertebrae. Our visual determinations were dependable, radiographic and a examination of the third lumbar vertebra rather than that of other lumbar vertebrae was more helpful for the detection of radiographic bone atrophy. Plain radiographic film can provide a rough estimation of bone atrophy.

Absorptiometry, Photon↗
PubMed1998

Structure of murine enterokinase (enteropeptidase) and expression in small intestine during development.

Enterokinase (enteropeptidase) is expressed only in proximal small intestine, where it initiates digestive enzyme activation by converting trypsinogen into trypsin. To investigate this restricted expression pattern, mouse enterokinase cDNA was cloned, and the distribution of enterokinase mRNA and enzymatic activity were determined in adult mice and during gestation. Analysis of enterokinase sequences showed that a mucinlike domain near the NH2 terminus is composed of repeated approximately 15-amino acid Ser/Thr-rich motifs. By Northern blotting and trypsinogen activation assays, enterokinase mRNA and enzymatic activity were undetectable in stomach, abundant in duodenum, and decreased distally until they were undetectable in midjejunum, ileum, and colon. By in situ mRNA hybridization, enterokinase mRNA was localized to the enterocytes throughout the villus. Expression was not observed in goblet cells, Paneth cells, or Brunner's glands. Enterokinase mRNA and enzymatic activity were not detected in the duodenum of fetal mice but were easily detected in the duodenum on postnatal days 2-6. Both enterokinase mRNA and enzymatic activity decreased to very low levels after day 7 but increased after weaning and reached a high level characteristic of adult life by day 60. Therefore, in mice, duodenal enterocytes are the major type of cells expressing enterokinase, which appears to be regulated at the level of mRNA abundance.

Amino Acid Sequence↗
PubMed1998

Transcription and translation of estrogen receptor-beta in the male reproductive tract of estrogen receptor-alpha knock-out and wild-type mice.

Estrogen receptor-alpha (ERalpha) has been identified in the male reproductive tract, but the role of estrogen in the male has not been well characterized. In vivo mutations in ERalpha genes have demonstrated the necessity for ERalpha-mediated action in male fertility. We asked whether both ERbeta messenger RNA and protein were present in the male reproductive tract of wild-type and ERalpha knock-out (ERalpha KO) mice, and whether ERbeta could compensate for the lack of ERalpha in infertile male ERalpha KO mice. Immunohistochemical localization with both N- and C-terminal anti-ERbeta antibodies demonstrated that ERbeta is present in the Leydig cells of the testes and in the epithelium of both the efferent ductules and the initial segment of the epididymis. RT-PCR amplification was used to confirm ERbeta transcription in these tissues. In conclusion, we observed that ERbeta messenger RNA and protein continue to be expressed in the Leydig cells, elongated spermatids, efferent ductules, and the initial segment of the epididymides of ERalpha KO mice, but the presence of ERbeta is not able to compensate for the absence of ERalpha in male reproductive function.

Animals↗
PubMed1998

A role for glutamate and its receptors in the regulation of oligodendrocyte development in cerebellar tissue slices.

We tested the hypothesis that the neurotransmitter glutamate would influence glial proliferation and differentiation in a cytoarchitecturally intact system. Postnatal day 6 cerebellar slices were maintained in organotypic culture and treated with glutamate receptor agonists or antagonists. After dissociation, cells were stained with antibodies for different oligodendrocyte developmentally regulated antigens. Treatment of the slices with the glutamate receptor agonists kainate or alpha -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid significantly decreased the percentage of LB1(+), NG2(+) and O4(+) cells, and their bromodeoxyuridine labeling index. The non-N-methyl-D-aspartate glutamate receptor antagonist 6,7-dinitroquinoxaline-2,3-dione increased the percentage and bromodeoxyuridine labeling of LB1(+), NG2(+) and O4(+) cells. In intact slices, RNA levels of the oligodendrocyte gene for 2',3'-cyclic nucleotide 3'-phosphodiesterase were decreased by kainate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and increased by 6,7-dinitroquinoxaline-2,3-dione. The percentage of astrocytes was not modified by kainate, alpha -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid or 6, 7-dinitroquinoxaline-2,3-dione. Treatment with the N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonopentanoic acid did not alter the percentage of O4(+) cells, nor their proliferation. Incubation with the gamma-aminobutyric acid receptor antagonist bicuculline did not modify the percentage of LB1(+), A2B5(+) and O4(+) cells. In purified cerebellar oligodendrocyte progenitor cells, glutamate receptor agonists blocked K+ currents, and inhibited cell proliferation and lineage progression. The K+ channel blocker tetraethylammonium also inhibited oligodendrocyte progenitor cell proliferation. These findings indicate that in rat cerebellar tissue slices: (i) glutamate specifically modulates oligodendrocyte but not astrocyte development through selective activation of alpha -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, and (ii) cell depolarization and blockage of voltage-dependent K+ channels is likely to be the triggering mechanism.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1998

Codon 972 polymorphism of the insulin receptor substrate-1 gene in impaired glucose tolerance and late-onset NIDDM.

OBJECTIVE: To assess the relevance of a Gly-->Arg substitution in codon 972 of the insulin receptor substrate-1 gene in impaired glucose tolerance (IGT) and NIDDM. RESEARCH DESIGN AND METHODS: The genotype of 1,106 Japanese subjects consisting of 310 subjects with NIDDM, 305 subjects with IGT, and 491 normal control subjects was analyzed by an allele-specific assay using polymerase chain reaction and restriction fragment length polymorphism. RESULTS: The frequency of the variant allele was not different between subjects with NIDDM (0.021) and normal control subjects (0.020). However, subjects with IGT showed a significantly higher prevalence of the variant allele (0.041, P = 0.027). We found two homozygous individuals for the variant; both had IGT with mild insulin resistance. The allelic frequency tended to be lower in normal control subjects aged > 50 years than in younger control subjects. Conversely, in the subjects with IGT or NIDDM, the Gly972Arg substitution was more frequently found in subjects aged > 50 years. Furthermore, NIDDM patients with the variant allele had older ages of diagnosis than patients without the variant. CONCLUSIONS: The codon 972 variant may be associated with IGT and a subset of late-onset NIDDM in the elderly Japanese population.

Adult↗
PubMed1998

Effects of acupuncture at fengchi point (GB 20) on cerebral blood flow.

Blood velocity in the vertebral artery and the basilar artery was observed before and after acupuncture at Fengchi point (GB 20) in 97 patients by transcranial Doppler ultrasonic detecting. The results showed that the blood velocity in patients with either high or low blood flow had significant changes after acupuncture (P < 0.001).

Acupuncture Points↗
PubMed1998

A study on visual evoked potential to show the relationship between the eyes and the twelve regular channels.

The visual electrophysiologic method was used to investigate the relationship between the eyes and the 12 regular channels. The values of the latent period and the amplitude of P100 wave were calculated and compared statistically. The results show that: 1) The eyes and the 12 regular channels are closely related, no matter whether the channels are classically associated with the eyes or not, while the control (non-channel)/ point has no such relationship; 2) the degrees of relationship between the eyes and the 12 regular channels vary significantly; and 3) acupuncture at the 12 regular channels induces different effects on the visual evoked potential that the Urinary Bladder Channel presents a facilitation effect whereas all the other channels chiefly show an inhibitory effect.

Adolescent↗
PubMed1998

[A primary study of microanatomy on blood supplement of large and huge pituitary adenoma].

OBJECTIVE: To explore the blood supplement regularity of large and huge pituitary adenomas. MECHODS: Sixteen large and huge pituitary adenomas were removed by microsurgery via transorbitofrontosphenoidal approach. The blood vessels of the tumors coming from surrounding structures were observed, photographed, videotaped and measured during operation. RESULTS: The blood supplement of the pituitary adenoma comes from not only the superior and inferior hypophyseal arteries, but also a lot of new arteries originating from meninges, optic nerves, optic chiasm, and arteries which surround the tumors, such as internal carotid artery, anterior cerebral artery and soon. CONCLUSION: The blood supplement of large and huge pituitary adenomas is increased obviously. The operation results will get much better if this situation is recognized and handled very well.

Adenoma↗
PubMed1998

[Clinical and experimental study on the Houpu Mahuang oral liquid in treating bronchial asthma].

OBJECTIVE: To probe into the curative effect and mechanism of action of the Houpu Mahuang oral liquid (HPMH) in treating bronchial asthma. METHODS: The pulmonary function and level of serum IgE of the patients were determined before and after HPMH treatment. The anti-allergic reaction and relieving spasm effect of HPMH in animal were also observed. RESULTS: HPMH is not only effective in improving clinical symptoms and pulmonary function (P < 0.05), so as to lower the abnormal raising of IgE (P < 0.01), but also has a notable inhibitory effect for passive allergic reaction of rat's skin, it can relieve spasm. CONCLUSIONS: HPMH is effective in relieving spasm, antiallergic reaction, it can improve the symptoms of bronchial asthma.

Adult↗
PubMed1997

Bovine proenteropeptidase is activated by trypsin, and the specificity of enteropeptidase depends on the heavy chain.

Enteropeptidase, also known as enterokinase, initiates the activation of pancreatic hydrolases by cleaving and activating trypsinogen. Enteropeptidase is synthesized as a single-chain protein, whereas purified enteropeptidase contains a approximately 47-kDa serine protease domain (light chain) and a disulfide-linked approximately 120-kDa heavy chain. The heavy chain contains an amino-terminal membrane-spanning segment and several repeated structural motifs of unknown function. To study the role of heavy chain motifs in substrate recognition, secreted variants of recombinant bovine proenteropeptidase were constructed by replacing the transmembrane domain with a signal peptide. Secreted variants containing both the heavy chain (minus the transmembrane domain) and the catalytic light chain (pro-HL-BEK (where BEK is bovine enteropeptidase)) or only the catalytic domain (pro-L-BEK) were expressed in baby hamster kidney cells and purified. Single-chain pro-HL-BEK and pro-L-BEK were zymogens with extremely low catalytic activity, and both were activated readily by trypsin cleavage. Trypsinogen was activated efficiently by purified enteropeptidase from bovine intestine (Km = 5.6 microM and kcat = 4.0 s-1) and by HL-BEK (Km = 5.6 microM and kcat = 2.2 s-1), but not by L-BEK (Km = 133 microM and kcat = 0.1 s-1); HL-BEK cleaved trypsinogen at pH 5.6 with 520-fold greater catalytic efficiency than did L-BEK. Qualitatively similar results were obtained at pH 8.4. In contrast to this striking difference in trypsinogen recognition, the small synthetic substrate Gly-Asp-Asp-Asp-Asp-Lys-beta-naphthylamide was cleaved with similar kinetic parameters by both HL-BEK (Km = 0.27 mM and kcat = 0.07 s-1) and L-BEK (Km = 0.60 mM and kcat = 0.06 s-1). The presence of the heavy chain also influenced the rate of reaction with protease inhibitors. Bovine pancreatic trypsin inhibitor preferred HL-BEK (initial Ki = 99 nM and final Ki* = 1.8 nM) over L-BEK (Ki = 698 nM and Ki* = 6.2 nM). Soybean trypsin inhibitor exhibited a reciprocal pattern, inhibiting L-BEK (Ki* = 1.6 nM), but not HL-BEK. These kinetic data indicate that the enteropeptidase heavy chain has little influence on the recognition of small peptides, but strongly influences macromolecular substrate recognition and inhibitor specificity.

Animals↗
PubMed1997

Solution structure of the transforming growth factor beta-binding protein-like module, a domain associated with matrix fibrils.

Here we describe the high resolution nuclear magnetic resonance (NMR) structure of a transforming growth factor beta (TGF-beta)-binding protein-like (TB) domain, which comes from human fibrillin-1, the protein defective in the Marfan syndrome (MFS). This domain is found in fibrillins and latent TGF-beta-binding proteins (LTBPs) which are localized to fibrillar structures in the extracellular matrix. The TB domain manifests a novel fold which is globular and comprises six antiparallel beta-strands and two alpha-helices. An unusual cysteine triplet conserved in the sequences of TB domains is localized to the hydrophobic core, at the C-terminus of an alpha-helix. The structure is stabilized by four disulfide bonds which pair in a 1-3, 2-6, 4-7, 5-8 pattern, two of which are solvent exposed. Analyses of MFS-causing mutations and the fibrillin-1 cell-binding RGD site provide the first clues to the surface specificity of TB domain interactions. Modelling of a homologous TB domain from LTBP-1 (residues 1018-1080) suggests that hydrophobic contacts may play a role in its interaction with the TGF-beta1 latency-associated peptide.

Amino Acid Sequence↗
PubMed1997

Comparative gene mapping of the human and mouse TEP1 genes, which encode one protein component of telomerases.

The chromosomal locations of the human TEP1 (telomerase protein component 1) and mouse Tep1 genes, which were originally named TLP1 (telomerase protein 1) or TP1 (telomerase-associated protein 1), were determined by direct R-banding FISH and a molecular linkage analysis with interspecific backcross mice. The human TEP1 and mouse Tep1 genes were mapped by FISH to human chromosome 14q11.2 and to the C2D1 band of mouse chromosome 14, respectively. By means of genetic linkage mapping, the mouse gene was further localized as being 2.7 cM distal to D14Mit18 and D14Mit134 and 2.0 cM proximal to D14Mit5 on mouse chromosome 14, where conserved linkage homology with human chromosome 14q11-q12 has been identified.

Animals↗
PubMed1997

Purification, biochemical characterization and protein-DNA interactions of the I-CreI endonuclease produced in Escherichia coli.

I- CreI is a member of the LAGLI-DADG family of homing nucleases; however, unlike most members of this family it contains only a single copy of this signature motif. I- CreI was over-expressed in Escherichia coli, and a simple purification protocol developed that gave reasonably pure protein in high yield. Size-exclusion chromatography and chemical cross-linking indicated that the protein is a dimer in solution. DNA cleavage by I- CreI was absolutely dependent on Mg2+(or Mn2+), and was inhibited by monovalent cations. I- CreI displayed a surprisingly high temperature optimum (>50 degrees C), with full activity occurring even at 70 degrees C. Interestingly, SDS was needed for efficient release of the cleavage products from the protein, indicating formation of very stable DNA-protein complexes. In contrast to these robust characteristics, purified I- CreI was unstable; however, it could be stabilized by the addition of either target or non-target DNA. Mobility shift assays revealed that I- CreI binds to DNA in the absence of Mg2+. Hydroxyl radical footprinting showed that I- CreI strongly protected the backbone of a continuous stretch of at least 12 nt on each strand that were shifted, relative to each other, by 2 bp in the 3'direction. Methylation protection and interference analyses were also performed, and together with the hydroxyl radical footprinting, indicate that I- CreI binds in both the major and minor grooves of its target DNA.

Base Sequence↗
PubMed1997

Expression, purification and kinetic characterization of wild-type human ornithine transcarbamylase and a recurrent mutant that produces 'late onset' hyperammonaemia.

Ornithine Transcarbamylase Deficiency, an X-linked disorder, is the most common cause of inherited urea cycle disorders. Approx. 90 mutations that produce reduced levels of ornithine transcarbamylase (OTCase) activity have been identified in patients [Tuchman (1993) Hum. Mutat. 2, 174-178; Tuchman and Plante (1995) Hum. Mutat. 5, 293-295]. A model of the three-dimensional structure of OTCase, developed on the basis of its homology to the catalytic subunit of Escherichia coli aspartate transcarbamylase (ATCase) [Tuchman, Morizono, Reish, Yuan and Allewell (1995) J. Med. Genet. 32, 680-688], and in good agreement with the crystal structure of Pseudomonas aeruginosa OTCase [Villeret, Tricot, Stalon and Dideberg (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 10762-10766], indicates that many mutations that produce severe clinical symptoms are at the active site or buried in the interior of the protein. However, one of the few recurrent mutations, R277W, an alteration that produces a milder phenotype of ornithine transcarbamylase deficiency, is located in the model in a loop remote from the active site that is analogous to a similar loop (the 240's loop, a flexible loop of the catalytic chain of Escherichia coli aspartate transcarbamylase, comprised of residues 230-250) of ATCase. Human wild-type OTCase and the R277W mutant have been cloned and overexpressed in E. coli and a rapid and efficient purification method utilizing the bisubstrate analogue, Ndelta-(phosphonacetyl)-L-ornithine, has been developed and used to purify both proteins. Gel chromatography indicates both are trimeric. The pH dependence of the kinetic parameters of the wild-type enzyme is similar to that of E. coli OTCase [Kuo, Herzberg and Lipscomb (1985) Biochemistry 24, 4754-4761], suggesting that its catalytic mechanism is similar, although its maximal activity is approx. 10-fold less. Compared with the wild-type, the R277W mutant has nearly 70-fold lower affinity for L-ornithine, shows no substrate inhibition, and its thermal stability is reduced by 5 degrees C. Its reduced affinity for L-ornithine, which in turn results in lower activity at physiological concentrations of ornithine, as well as its reduced stability, may contribute to the clinical effects that it produces.

Ammonia↗
PubMed1997

Association between Ala54Thr substitution of the fatty acid-binding protein 2 gene with insulin resistance and intra-abdominal fat thickness in Japanese men.

Alanine to threonine substitution at codon 54 of the fatty acid-binding protein 2 (FABP2) gene was recently shown to be associated with insulin resistance in Pima Indians. It has been hypothesized that the mutation may result in enhanced intestinal up-take of fatty acids, and thereby an impairment of insulin action. We analysed the association of the Ala54Thr substitution with insulin sensitivity and abdominal fat thickness in 395 Japanese men aged 50.5 +/- 8.8 years (mean +/- SD) with a body mass index of 24.4 +/- 3.0 kg/m2. The frequency of the Thr54 allele was 0.34. Although the polymorphism was not significantly associated with diabetes or impaired glucose tolerance, subjects homozygous for the Thr54 allele had higher basal insulin levels. Analysis by homeostasis model assessment showed an association between the amino acid substitution and greater insulin resistance, and slightly higher beta-cell function. Oral glucose tolerance tests performed in 392 subjects without fasting hyperglycaemia showed higher 2-h insulin concentrations in individuals homozygous for the Thr54 allele when compared with heterozygotes or homozygotes for the Ala54 allele. No significant association was obtained between the polymorphism of the FABP2 gene and body mass index. However, ultrasound measurements of abdominal fat thickness revealed a greater accumulation of intra-abdominal fat in subjects homozygous for the Thr54 allele, whereas subcutaneous fat thickness was not associated with the polymorphism. These observations suggest that the Ala54Thr substitution in the FABP2 gene is associated with insulin resistance in Japanese men, and that visceral fat accumulation might be involved in the impaired insulin action associated with the substitution.

Abdomen↗
PubMed1997

Physical mapping and structural analysis of new gene families RT1.S and Rps2r in the grc region of the rat major histocompatibility complex.

Five new genes were identified in the growth and reproduction complex (grc) region: RT1.S1, RT1.S2, Rps2r1, Rps2r2, and Rps2r3. The class Ib RT1.S1 and RT1.S2 genes have five distinct exons (1, 4, 5, 6, 7) similar to other class I major histocompatibility complex genes but the conventional exons 2 and 3 are absent. The genes are 97% similar, have CAAT and TATA boxes much upstream of the conventional position, obey the GT/AG rule in their exon-intron boundaries, and are transcribed at a low level in thymus and testis but not in the liver and spleen. The region between exon 1 and exon 4 was analyzed by obtaining transcripts by reverse transcription-polymerase chain reaction (RT-PCR) amplification which revealed the presence of four alternatively spliced mRNA transcripts of RT1.S1: 1) S1-1 (clones 14 and 16) has no exon between exons 1 and 4; 2) S1-2 (clones 7 and 8) has an exon of 45 nucleotides that can translate into 15 amino acids; 3) S1-3 (clone 5) has an exon of 42 nucleotides with a stop codon; and 4) S1-4 (clone 10) has two exons of 42 and 38 nucleotides, respectively, with stop codons. Only one RT1.S2 mRNA transcript was obtained, and it has an exon of 45 nucleotides between exon 1 and exon 4 which can form a peptide identical to the S1-2 isoform for that region. The 45 nucleotide exon between exon 1 and exon 4 was unique for RT1.S1 and RT1.S2 and only matched a sequence in the RT1.O intron region (nucleotides 2905 - 2949). The three ribosomal-protein-S2-related (Rps2r) genes are 94% - 98% similar; they are related to the genes encoding ribosomal protein S2 of the black rat and the LLRep3 genes of the mouse and the human and to the genes encoding Saccharomyces cerevisiae S4, Escherichia coli S5, and other members of prokaryote S5 family. The Rps2r1 gene is located just outside of the grc region. The Rps2r2 and Rps2r3 genes are in the grc and have multiple stop codons in their genomic sequences. The Rps2r1 mRNA transcript was identified by RT-PCR in the thymus and testis but not in the liver and spleen.

Amino Acid Sequence↗