Biomedical subjects

X Wei

Publications and source records attributed to X Wei.

At least 19 recordsLinked to original sources

PubMed2000

White matter abnormalities in mobility-impaired older persons.

OBJECTIVE: To investigate the relationship between white matter abnormalities and impairment of gait and balance in older persons. METHODS: Quantitative MRI was used to evaluate the brain tissue compartments of 28 older individuals separated into normal and impaired groups on the basis of mobility performance testing using the Short Physical Performance Battery. In addition, individuals were tested on six indices of gait and balance. For imaging data, segmentation of intracranial volume into four tissue classes was performed using template-driven segmentation, in which signal-intensity-based statistical tissue classification is refined using a digital brain atlas as anatomic template. RESULTS: Both decreased white matter volume, which was age-related, and increased white matter signal abnormalities, which were not age-related, were observed in the mobility-impaired group compared with the control subjects. The average volume of white matter signal abnormalities for impaired individuals was nearly double that of control subjects. CONCLUSIONS: This cross-sectional study suggests that decreased white matter volume is age-related, whereas increased white matter signal abnormalities are most likely to occur as a result of disease. Both of these changes are independently associated with impaired mobility in older persons and therefore likely to be additive factors of motor disability.

Aged↗

PubMed2000

Study on DNA strand breaks induced by sodium nitroprusside, a nitric oxide donor, in vivo and in vitro.

Nitric oxide (NO) as well as its donors has been shown to generate mutation and DNA damage in in vitro assays. The objective of this study was to identify that DNA single-strand breaks (SSBs) could be elicited by NO, not only in vitro but also in vivo. The alkaline single-cell gel electrophoresis (SCGE) was performed to examine the DNA damage in g12 cells and the cells isolated from the organs of mice exposed to sodium nitroprusside (SNP). A modified method, in which neither collagenase nor trypsin was necessary, was used to prepare the single-cell suspension isolated from organs of mice. Results showed that the exposure of g12 cells to 0.13-0.5 micromol/ml SNP with S9 for 1 h induced a concentration-dependent increase in DNA SSBs in g12 cells. The significant increase in DNA migration and comet frequency has appeared in the cells isolated from the spleen, thymus, and peritoneal macrophages of mice after injecting i.p. SNP in the dosage range of 0.67-6.0 mg/kg b.wt for 1 h. However, no obvious increase in DNA strand breaks was observed in the cells isolated from the liver, kidney, lung, brain and heart obtained from the same treated mice. These results suggested that DNA SSBs could be induced by NO in some cells both in vivo and in vitro. There were organ differences in sensitivity in the mice exposed to NO. Spleen, thymus, and macrophages might be the important targets of NO.

Akathisia, Drug-Induced↗

PubMed2000

Activated macrophages direct apoptosis and suppress mitosis of mesangial cells.

During inflammation in the glomerulus, the complement of resident myofibroblast-like mesangial cells is regulated by mitosis and apoptosis, but the cellular mechanisms controlling the size of mesangial cell populations have remained obscure. Prompted by studies of development, we sought evidence that macrophages regulate mesangial cell number. Rat bone marrow-derived macrophages primed with IFN-gamma then further activated in coculture with LPS or TNF-alpha elicited a 10-fold induction of rat mesangial cell apoptosis and complete suppression of mitosis, effects inhibitable by the NO synthase inhibitors L-monomethyl arginine and L-N(6)-(1-iminoethyl) lysine dihydrochloride. Complete dependence upon macrophage-derived NO was observed in comparable experiments employing activated bone marrow macrophages from wild-type and NO synthase 2(-/-) mice. Nevertheless, when mesangial cells were primed with IFN-gamma plus TNF-alpha, increased induction by activated macrophages of mesangial apoptosis exhibited a NO-independent element. The use of gld/gld macrophages excluded a role for Fas ligand in this residual kill, despite increased expression of Fas and increased susceptibility to soluble Fas ligand exhibited by cytokine-primed mesangial cells. Finally, activated macrophages isolated from the glomeruli of rats with nephrotoxic nephritis also induced apoptosis and suppressed mitosis in mesangial cells by an L-monomethyl arginine-inhibitable mechanism. These data demonstrate that activated macrophages, via the release of NO and other mediators, regulate mesangial cell populations in vitro and may therefore control the mesangial cell complement at inflamed sites.

Animals↗

PubMed2000

Tandem Intermolecular - Intramolecular Carbolithiation: A Versatile Method for Synthesis of Cyclopentanes.

Polysubstituted cyclopentanes from readily available starting materials? A versatile anionic [3+2] approach is offered by the reaction of difunctional organolithium reagents 1 with alkenes 2 in a tandem intermolecular - intramolecular carbolithiation (see scheme). This convergent sequence is especially attractive as, not only are the precursors readily available, but the products provide valuable synthetic building blocks.

Journal Article↗

PubMed1999

Differential display and cloning of the hippocampal gene mRNas in senescence accelerated mouse.

Identification of genes that are specifically expressed in the hippocampus of senescence accelerated mouse (SAM) is important for understanding the molecular basis of the pathological changes in the brain and of the deterioration of learning and memory in SAM-prone/8 (SAMP8), a substrain of SAM. The differential display technique was applied to compare mRNAs expression between SAMP8 and SAM-resistance 1 (SAMR1), another substrain of SAM. Complementary DNA fragments corresponding to several apparently differentially expressed mRNAs were recovered and sequenced. Six differentially expressed cDNA bands were identified. Sequence analyses demonstrated that W4 and W5 cDNA fragments corresponded to unknown genes. W1 and W6 showed 66.1 and 62.3% homology to rat GTP-exchange protein (eIF-2B) and rat phospholipase D, respectively, while W2 and W3 showed 89.2 and 90.8% homology to human bullous pemphigoid antigen and human glucogen debranching enzyme isoform 1/2/3/4/6, respectively. The results suggested that these genes are closely related to the malfunction of the brain in SAM.

Aging↗

PubMed1999

Maturation-dependent durability of spontaneous cartilage repair in rabbit knee joint.

The spontaneous healing of osteochondral defects in the knee joints of immature rabbits within the first 12 weeks after surgery showed a faster filling and earlier tissue specialization than in adult animals. The purpose of the present study was to investigate whether the better short-term quality of spontaneous repairs in immature animals lasted over a period of 48 weeks. A full-thickness osteochondral defect was created on the medial femoral condyle in both knees of 10 young, 10 adolescent, and 10 adult rabbits. Equal numbers of animals were evaluated after 24 and 48 weeks. At both time intervals, bonding to adjacent cartilage and proteoglycan content of the matrix were better in the repairs of young than in adult animals. Repairs in the former had cellularity similar to the adjacent cartilage and were composed of 90% hyaline-like cartilage, which did not decrease with time. In contrast, repairs in older animals formed less hyaline-like cartilage and had a lower cellularity than the adjacent cartilage. However, the surface of the repaired tissue was similarly disrupted in all age groups, and the mechanical properties remained inferior to adjacent or normal cartilage. Repairs in older animals showed signs of degeneration with time. The initial better repair quality in a young, growing animal remained up to 48 weeks when the animal had already reached maturity, indicating that successful initial promotion of cartilage repair may even lead to better results in the long term. However, it has to be pointed out that the morphologically good repairs with hyaline-like cartilage appearance, normal cellularity, and durability of up to 48 weeks were unable to reestablish and maintain a cartilage-like mechanical function.

Age Factors↗

PubMed1999

Increased protein phosphorylation of cytoplasmic dynein results in impaired motor function.

Inhibition of serine/threonine protein phosphatases in rat hepatocytes by okadaic acid and microcystin increased the phosphorylation of several components of the cytoplasmic dynein complex. UV light/vanadate cleavage and Western blot analysis revealed that two of these components with molecular masses of approx. 400 kDa and 74 kDa were dynein heavy- and intermediate-chains respectively. This increased phosphorylation resulted in inhibition of dynein ATPase activity, and reduced motor-dependent avidity of endosomal/lysosomal membranes for microtubules.

Animals↗

PubMed1999

Three-dimensional visualization of transcription sites and their association with splicing factor-rich nuclear speckles.

Transcription sites are detected by labeling nascent transcripts with BrUTP in permeabilized 3T3 mouse fibroblasts followed by laser scanning confocal microscopy. Inhibition and enzyme digestion studies confirm that the labeled sites are from RNA transcripts and that RNA polymerase I (RP I) and II (RP II) are responsible for nucleolar and extranucleolar transcription, respectively. An average of 2,000 sites are detected per nucleus with over 90% in the extranucleolar compartment where they are arranged in clusters and three-dimensional networklike arrays. The number of transcription sites, their three-dimensional organization and arrangement into functional zones (Wei et al. 1998) is strikingly maintained after extraction for nuclear matrix. Significant levels of total RP II mediated transcription sites (45%) were associated with splicing factor-rich nuclear speckles even though the speckles occupied <10% of the total extranucleolar space. Moreover, the vast majority of nuclear speckles (>90%) had moderate to high levels of associated transcription activity. Transcription sites were found along the periphery as well as inside the speckles themselves. These spatial relations were confirmed in optical sections through individual speckles and after in vivo labeling of nascent transcripts. Our results demonstrate that nuclear speckles and their surrounding regions are major sites of RP II-mediated transcription in the cell nucleus, and support the view that both speckle- and nonspeckle-associated regions of the nucleus contain sites for the coordination of transcription and splicing processes.

3T3 Cells↗

PubMed1999

Assessment of effectiveness of Vaxigrip.

In order to assess the effectiveness of Vaxigrip in 1996-1997, we chose 1356 people in the Chinese Army, who had not recently had influenza and who were divided into an injection group and a control group. The injection group consisted of 80 children aged 3-6 years, 363 adults aged 18-59 years and 235 people over 60 years of age. The control group consisted of 88 children aged 3-6, 372 adults aged 18-59 and 218 people over 60. They were observed from the 21st day to the 6th month after Vaxigrip administration. Each person was requested to report having a body temperature over 38.5 degrees C, headache, myalgia or arthalgia, cough, pharyngodynia or nasal obstruction. Fever due to other causes was not included in the influenza symptoms. We counted the symptoms of influenza and common cold only once during the observation period. Our final finding was that the incidence rates of the influenza and common cold symptoms were reduced by 84.8% in children, 74.0% in adults and 68.6% in elderly people. In comparison with the control group, the incidence rate of influenza-like symptoms was reduced by 71.1% in the injection group, and the incidence rate of common cold symptoms in the injection group was lower than that in the control group. There was no large difference by age. The incidence rate of symptoms of upper respiratory tract infection in the injection group was 47.5% lower than that in the control group. Our findings are basically the same as those in other countries.

Adolescent↗

PubMed1999

Mapping the sensitivity of T cells with an optical trap: polarity and minimal number of receptors for Ca(2+) signaling.

Contact with antigen-presenting cells (APCs) initiates an activation cascade within T lymphocytes, including a rise in cytosolic calcium, lymphokine production, and cell division. Although T cell-APC physical contact is required for an immune response, little is known about the patterns of cellular interactions and their relation to activation. Calcium imaging combined with an optical trap enabled the T cell contact requirements and polarity to be investigated at the single-cell level. APCs or anti-CD3 mAb-coated beads were trapped with a laser and placed at different locations along the T cell, which has a polarized appearance defined by the shape and direction of crawling. T cells were 3-fold more sensitive to APC contact made at the leading edge of the T cell than with contact made at the tail. Anti-CD3 mAb-coated 6-micrometer beads induced calcium signaling with approximately 10-fold higher frequency and approximately 4-fold shorter latency on contact with the leading edge of the T cell than on contact with the trailing edge. Alterations in antibody density (2 to 500 per micrometer(2)) and bead size (1 to 6 micrometer in diameter) were used to determine the spatial requirements and the minimal number of receptors which must be engaged to transmit a positive signal. T cell response percentage, latency, and calcium-signaling pattern (transient vs. sustained or oscillatory) depended on antibody density on the bead. The presence of approximately 170 anti-CD3 mAb within the contact area elicited a detectable T cell calcium response. We propose here that engagement of no more than 340 T cell receptors (approximately 1% of the total on the cell) is sufficient to initiate Ca(2+) signaling. The minimal contact area was approximately 3 micrometer(2).

Animals↗

PubMed1999

Alzheimer's disease-related gene expression in the brain of senescence accelerated mouse.

The levels of Alzheimer's disease (AD)-related genes, including beta-amyloid precursor protein(APP), presenilin-1 (PS-1), PS-2, apoE, tau, c-fos, neural cell adhesion molecular 180 (NCAM-180), TGF-beta 1, IL-1 alpha/beta, IL-6, TNF-alpha/beta, alpha-2-Macroglobulin (alpha 2M), class II major histocompatibility antigen la (MHCII la), bcl-2 alpha, glucocorticoid receptor-alpha (GR alpha) and mineralocorticoid receptor (MR) mRNAs were determined by reverse transcription polymerase chain reaction (RT-PCR) in the hippocampus and cerebral cortex of senescence accelerated mouse (SAM). The levels of TGF-beta 1, IL-1 alpha, TNF-beta, c-fos, NCAM-180, PS-1 and APP mRNAs were normally expressed in SAMP8 compared with age-matched other subline that is resistant (SAMR1). The levels of apoE, GR alpha and MR mRNAs in the hippocampus of SAMP8, especially GR alpha, were evidently lower than those in the hippocampus of SAMR1. While bcl-2 alpha, PS-2 and tau mRNA levels of SAMP8 were significantly higher than those of SAMR1. Inflammatory cytokines (IL-1 beta, IL-6, TNF-alpha), alpha 2M and MHCII la antigen mRNAs were not detected in the brain of SAM. The differences of gene expression in the cerebral cortex were less evident than in the hippocampus. The results indicated that some genes abnormally expressed in the AD brain were also found in the brain of SAMP8, which may contribute to its age-related deterioration of learning and memory. Our results also suggested that functional and pathological changes which occurred in the brain of SAMP8 possessed some different aspects in comparison with the AD in consideration of the differences in gene expression.

Aging↗

PubMed1999

13-cis-Retinoic acid alters neural crest cells expressing Krox-20 and Pax-2 in macaque embryos.

This study investigates hindbrain and associated neural crest (NCC), otocyst, and pharyngeal arch development in monkey embryos following teratogenic exposure to 13-cis-retinoic acid (cRA). cRA was orally administered (5 mg/kg) to pregnant long-tailed macaques (Macaca fascicularis) between gestational days (GD) 12 and 27. Embryos were surgically collected at desired stages during treatment, analyzed for external morphological changes, and processed for immunohistochemistry. Two transiently expressed nuclear proteins, Krox-20 and Pax-2, were used as markers for the target cellular and anatomical structures. Rhombomere (r) expression patterns of Pax-2 (r4/r6) and Krox-20 (r3/r5) were maintained after cRA treatment, but r4 and r5 were substantially reduced in size. In untreated embryos, Krox-20 immunoreactive NCC derived from r5 migrated caudally around the developing otocyst to contribute to the third pharyngeal arch mesenchyme. In cRA-treated embryos, a subpopulation of NCC rostral to the otocyst also showed Krox-20 immunoreactivity, but there was a substantial reduction in Krox-20 post-otic NCC. Pax-2 immunoreactive NCC migrating from r4 to the second pharyngeal arch were substantially reduced in numbers in treated embryos. Alteration in the otic anlage included delayed invagination, abnormal relationship with the adjacent hindbrain epithelium, and altered expression boundaries for Pax-2. cRA-associated changes in the pharyngeal arch region due to cRA included truncation of the distal portion of the first arch and reduction in the size of the second arch. These alterations in hindbrain, neural crest, otic anlage, and pharyngeal arch morphogenesis could contribute to some of the craniofacial malformations in the macaque fetus associated with exposure to cRA.

Animals↗

PubMed1999

High-efficiency transfer of cystic fibrosis transmembrane conductance regulator cDNA into cystic fibrosis airway cells in culture using lactosylated polylysine as a vector.

To find more efficient vectors for the transfer of CFTR cDNA, lactosylated polylysine was explored for transfer into airway epithelial cells in primary culture. The efficacy and high efficiency of transfection were shown by several criteria: expression of both mRNA and protein for CFTR and the functional correction of the Cl- channel activity. Using specific combinations of agents to enhance the transfection, an efficiency of 90% was obtained as detected by in situ hybridization with digoxigenin-labeled probes generated against exon 14 of CFTR. The highest efficiency was observed by adding E5CA peptide (10 microg) and 5% glycerol to the transfection mixture. The degree of transfection could be controlled by the enhancing agents, thus modulating the efficiency of transfection. The highest level of transfection efficiency is equivalent to that reported for viral vectors. None of the agents or their combinations in the concentrations used were cytotoxic to the primary cells. Antibody pAb3145 was used to detect the expression of the CFTR protein in the cells. When an N-terminal GFP-CFTR fusion gene was used to transfect the CF cells a functional correction of the CFTR Cl- channel was detected by patch-clamp electrophysiology. The high efficiency of CFTR gene transfer with lactosylated polylysine leads to the conclusion that lactosylated polylysine is a promising vector to transfer the CFTR gene into human airway cells in culture.

Base Sequence↗

PubMed1999

Pathogenesis of retinoic acid-induced ear malformations in primate model.

13-cis retinoic acid (RA) is a causative agent for human/monkey retinoic acid embryopathy (RAE), in which the most common type of malformation is microtia or anotia. In the present study, malformed ears of monkey fetuses exposed to RA during early embryogenesis were analyzed and revealed a subtype of defects., i.e., apparent duplication of the external/middle ear. A part of the posterior auricle appeared to be ectopically formed in the anterior auricular region or in the region posterior to the auricle. Additionally, there was duplication of the zygomatic arch, malleus, and incus. In order to characterize possible pathogenetic events underlying these malformations, embryos at selected stages were collected after dosing dams with RA at 5 mg/kg/day during gestational days 12-27. Cellular retinoic acid binding protein I whole-mount immunostaining showed that RA induced specific alterations in the migration of cranial neural crest cells (NCC). NCC en route to the second pharyngeal arch were bifurcated, and some of these NCC migrated abnormally into the first and/or third arches, which may underlie external ear duplication. Scanning electron microscopy and neurofilament immunostaining provided evidence that there was partial duplication of trigeminal nerve/ganglion following RA insult. The duplication of NCC neuronal derivatives in the first pharyngeal arch is consistent with duplication of NCC mesenchymal components (zygomatic arch, malleus, and incus). Therefore, RA-induced alterations in cranial NCC migration patterns are likely to be a pathogenetic event underlying ear malformations (including duplication) of RAE in monkeys.

Animals↗

PubMed1999

Tn5-induced and spontaneous switching of Sinorhizobium meliloti to faster-swarming behavior.

Tn5 mutants of Sinorhizobium meliloti RMB7201 which swarmed 1.5 to 2. 5 times faster than the parental strain in semisolid agar, moist sand, and viscous liquid were identified. These faster-swarming (FS) mutants outgrew the wild type 30- to 40-fold within 2 days in mixed swarm colonies. The FS mutants survived and grew as well as or better than the wild type under all of the circumstances tested, except in a soil matrix subjected to air drying. Exopolysaccharide (EPS) synthesis was reduced in each of the FS mutants when they were grown on defined succinate-nitrate medium, but the extent of reduction was different for each. It appears that FS behavior likely results from a modest, general derepression of motility involving an increased proportion of motile and flagellated cells and an increased average number of flagella per cell and increased average flagellar length. Spontaneous FS variants of RMB7201 were obtained at a frequency of about 1 per 10,000 to 20,000 cells by either enrichment from the periphery of swarm colonies or screening of colonies for reduced EPS synthesis on succinate-nitrate plates. The spontaneous FS variants and Tn5 FS mutants were symbiotically effective and competitive in alfalfa nodulation. Reversion of FS variants to wild-type behavior was sporadic, indicating that reversion is affected by unidentified environmental factors. Based on phenotypic and molecular differences between individual FS variants and mutants, it appears that there may be multiple genetic configurations that result in FS behavior in RMB7201. The facile isolation of spontaneous FS variants of Escherichia coli and Pseudomonas aeruginosa indicates that switching to FS behavior may be fairly common among bacterial species. The substantial growth advantage of FS mutants and variants wherever nutrient gradients exist suggests that switching to FS forms may be an important behavioral adaptation in natural environments.

Blotting, Southern↗

PubMed1999

Inhibition of human liver cytochrome P-450 1A2 by the class IB antiarrhythmics mexiletine, lidocaine, and tocainide.

Mexiletine, lidocaine, and tocainide are class IB antiarrhythmic drugs that are used for the treatment of ventricular arrhythmias and are known to inhibit drug metabolism. The objectives of this study were to characterize the inhibitory effects of mexiletine, lidocaine, and tocainide on cytochrome P-450 1A2 (CYP1A2) activity in human liver microsomes and to evaluate their relative inhibitory potencies by using a molecular model of this P-450 isozyme. The inhibitory effect of mexiletine, lidocaine, and tocainide on cytochrome CYP1A2 in human liver microsomes was examined with methoxyresorufin O-demethylase activity as an index of the catalytic activity of this P-450 isozyme. The kinetic inhibition types and Ki values were determined by Lineweaver-Burk plots and Dixon plots, respectively. Molecular modeling was used to assess the interaction of these agents with the CYP1A2 active site. Methoxyresorufin O-demethylase activity was inhibited 67 +/- 8%, 20 +/- 5%, and 7 +/- 4% by 2 mM mexiletine, lidocaine, and tocainide, respectively. Mexiletine and lidocaine exhibited competitive inhibition with Ki values of 0.28 +/- 0.12 mM and 1.54 +/- 0.74 mM, respectively, whereas the inhibition type of tocainide could not be determined because of its weak potency. A charge interaction between mexiletine and the Asp313 side chain in the CYP1A2 active site was found, and varying degrees of hydrogen bond formation between these three compounds and the CYP1A2 active site were observed. The in vitro inhibitory potencies in human liver microsomes (mexiletine > lidocaine > tocainide) are consistent with the structural interactions found in a molecular model of the active site of CYP1A2.

Anti-Arrhythmia Agents↗

PubMed1998

Segregation of transcription and replication sites into higher order domains.

Microscopy shows that individual sites of DNA replication and transcription of mammalian nuclei segregate into sets of roughly 22 and 16 higher order domains, respectively. Each domain set displayed a distinct network-like appearance, including regions of individual domains and interdigitation of domains between the two networks. These data support a dynamic mosaic model for the higher order arrangement of genomic function inside the cell nuclei.

3T3 Cells↗

PubMed1998

Characterization of the human dihydropyrimidine dehydrogenase gene.

Dihydropyrimidine dehydrogenase (DPD) catabolizes endogenous pyrimidines and pyrimidine-based antimetabolite drugs. A deficiency in human DPD is associated with congenital thymine-uraciluria in pediatric patients and severe 5-fluorouracil toxicity in cancer patients. The dihydropyrimidine dehydrogenase gene (DPYD) was isolated, and its physical map and exon-intron organization were determined by analysis of P1, PAC, BAC, and YAC clones. The DPYD gene was found to contain 23 exons ranging in size from 69 bp (exon 15) to 961 bp (exon 23). A physical map derived from a YAC clone indicated that DPYD is at least 950 kb in length with 3 kb of coding sequence and an average intron size of about 43 kb. The previously reported 5' donor splice site mutation present in pediatric thymine-uraciluria and cancer patients can now be assigned to exon 14. All 23 exons were sequenced from a series of human DNA samples, and three point mutations were identified in three racial groups as G1601A (exon 13, Ser534Asn), A1627G (exon 13, Ile543Val), and G2194A (exon 18, Val732Ile). These studies, which have established that the DPYD gene is unusually large, lay a framework for uncovering new mutations that are responsible for thymine-uraciluria and toxicity to fluoropyrimidine drugs.

Alleles↗