Biomedical subjects

L Wei

Publications and source records attributed to L Wei.

At least 145 records · Page 8Linked to original sources

PubMed1999

[Analysis for the auditory brainstem responses of guinea pigs with wavelet transform].

OBJECTIVE: To fine out the advantages of wavelet transform when it is applied in analysis of auditory brainstem responses. METHOD: Thirty of male, albino guinea pigs weighing 300 to 400 g were divided into three groups: 1. normal hearing; 2. conductive hearing loss; 3. sensorineural hearing loss. ABR of the animals was collected and represented with wavelet transform respectively. The signals before and after being transferred was contrasted and dealt with statistics. RESULT: The ABR signals are distorted in wavelet transform scale 2 and background noises are increased in scale 4. The conventional time feature of ABR signals can be conserved and the present of I wave can be increased in wavelet transform scale 3. CONCLUSION: Wavelet transform scale 3 is proper to analyze the ABR signals of guinea pig. Compared with conventional method, it can conserve the ABR signal's time feature and increase the emerged rate of I wave.

Animals↗

PubMed1998

Phosphorylation site independent single R-domain mutations affect CFTR channel activity.

We investigated CFTR channel activity of mature R-domain mutants showing single alterations at sites other than the predicted phosphorylation sites. All mutations were found in cystic fibrosis (CF) patients (H620Q, E822K and E826K). The macroscopic CFTR chloride conductance induced by phosphorylation was significantly enhanced in Xenopus oocytes injected with mRNA of H620Q but reduced in the E822K and E826K mutants compared to wild type CFTR. The anion permeability sequence for all three mutants was the same as that of wild type CFTR. Cell attached single channel studies in COS cells revealed that both open channel probability and/or the number of functional channels were either higher (H620Q) or lower (E822K and E826K) than in wild type CFTR. Single channel conductances were unchanged in all mutants. Our results suggest that additional sites in the R-domain other than phosphorylation sites influence gating of CFTR channels.

Animals↗

PubMed1998

RhoA signaling via serum response factor plays an obligatory role in myogenic differentiation.

Serum response factor (SRF) plays a central role during myogenesis, being required for the expression of striated alpha-actin genes. As shown here, the small GTPase RhoA-dependent activation of SRF results in the expression of muscle-specific genes, thereby promoting myogenic differentiation in myoblast cell lines. Co-expression of activated V14-RhoA and SRF results in an approximately 10-fold activation of the skeletal alpha-actin promoter in replicating myoblasts, while SRFpm1, a dominant negative SRF mutant, blocks RhoA dependent skeletal alpha-actin promoter activity. Serum withdrawal further potentiates RhoA- and SRF-mediated activation of alpha-actin promoter to about 30-fold in differentiated myotubes. In addition, the proximal SRE1 in the skeletal alpha-actin promoter is sufficient to mediate RhoA signaling via SRF. Furthermore, SRFpm1 and to a lesser extent dominant negative N19-RhoA inhibit myoblast fusion, postreplicative myogenic differentiation, and expression of direct SRF targets such as skeletal alpha-actin and indirect targets such as myogenin and alpha-myosin heavy chain. Moreover, RhoA also stimulates the autoregulatable murine SRF gene promoter in myoblasts, and the expression level of SRF is reduced in myoblasts overexpressing N19-RhoA. Our study supports the concept that RhoA signaling via SRF serves as an obligatory muscle differentiation regulatory pathway.

Actins↗

PubMed1998

Characterization of mutations located in exon 18 of the CFTR gene.

In order to get a better insight into the function of amino acid residues located in the second transmembrane domain of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, all exon 18 mutations found in cystic fibrosis (CF) patients were characterized at the protein and at the electrophysiological level. Of the different mutations present in transmembrane helix 12 (M1137V, M1137R, I11139V and deltaM1140), and the intracytoplasmic loop connecting TM12 and NBD2 (D1152H and D1154G), only M1137R interfered with the proper maturation of the protein. Permeability studies performed after injection of the different wild-type and mutant cRNAs in Xenopus laevis oocytes indicated that the mutations did not alter the permeability sequence of the CFTR channels. The whole cell cAMP activated chloride currents, however, were significantly reduced for M1137V, I1139V, D1152H and D1154G and close to zero for deltaM1140, indicating that these mutations interfere with the proper gating of the chloride channels.

Animals↗

PubMed1998

Instability of the amyloidogenic cystatin C variant of hereditary cerebral hemorrhage with amyloidosis, Icelandic type.

A cystatin C variant with L68Q substitution and a truncation of 10 NH2-terminal residues is the major constituent of the amyloid deposited in the cerebral vasculature of patients with the Icelandic form of hereditary cerebral hemorrhage with amyloidosis (HCHWA-I). Variant and wild type cystatin C production, processing, secretion, and clearance were studied in human cell lines stably overexpressing the cystatin C genes. Immunoblot and mass spectrometry analyses demonstrated monomeric cystatin C in cell homogenates and culture media. While cystatin C formed concentration-dependent dimers, the HCHWA-I variant dimerized at lower concentrations than the wild type protein. Amino-terminal sequence analysis revealed that the variant and normal proteins produced and secreted are the full-length cystatin C. Pulse-chase experiments demonstrated similar levels of normal and variant cystatin C production and secretion. However, the secreted variant cystatin C exhibited an increased susceptibility to a serine protease in conditioned media and in human cerebrospinal fluid, explaining its depletion from the cerebrospinal fluid of HCHWA-I patients. Thus, the amino acid substitution may induce unstable cystatin C with intact inhibitory activity and predisposition to self-aggregation and amyloid fibril formation.

Amino Acid Sequence↗

PubMed1998

Synaptic transmission deficits in Caenorhabditis elegans synaptobrevin mutants.

Synaptobrevins are vesicle-associated proteins implicated in neurotransmitter release by both biochemical studies and perturbation experiments that use botulinum toxins. To test these models in vivo, we have isolated and characterized the first synaptobrevin mutants in metazoans and show that neurotransmission is severely disrupted in mutant animals. Mutants lacking snb-1 die just after completing embryogenesis. The dying animals retain some capability for movement, although they are extremely uncoordinated and incapable of feeding. We also have isolated and characterized several hypomorphic snb-1 mutants. Although fully viable, these mutants exhibit a variety of behavioral abnormalities that are consistent with a general defect in the efficacy of synaptic transmission. The viable mutants are resistant to the acetylcholinesterase inhibitor aldicarb, indicating that cholinergic transmission is impaired. Extracellular recordings from pharyngeal muscle also demonstrate severe defects in synaptic transmission in the mutants. The molecular lesions in the hypomorphic alleles reside on the hydrophobic face of a proposed amphipathic-helical region implicated biochemically in interacting with the t-SNAREs syntaxin and SNAP-25. Finally, we demonstrate that double mutants lacking both the v-SNAREs synaptotagmin and snb-1 are phenotypically similar to snb-1 mutants and less severe than syntaxin mutants. Our work demonstrates that synaptobrevin is essential for viability and is required for functional synaptic transmission. However, our analysis also suggests that transmitter release is not completely eliminated by removal of either one or both v-SNAREs.

Animals↗

PubMed1998

Local cerebral blood flow during the first hour following acute ligation of multiple arterioles in rat whisker barrel cortex.

The objectives are to measure the early time-course of the flows of blood, red cells, and plasma in brain tissue destined to infarct following arterial occlusion. The flux of fluorescent red blood cells (fRBCs) through venules and the arteriovenous transit times (AVTT) of fluorescein-labeled plasma albumin were periodically monitored in anesthetized adult Wistar rats before and up to 60 min after permanent ligations of several small branches of the middle cerebral artery. Of note, fRBC is a function of venular erythrocyte flow and volume, whereas AVTT is a function of plasma flow and volume in visible arteriole-capillary-venule units. In another group of anesthetized rats, local cerebral blood flow (ICBF) was measured 1 h after permanent arterial occlusion by [14C]iodoantipyrine (IAP) autoradiography. With this model of focal ischemia, the lesion is highly reproducible and involves part of the whisker barrel cortex. Infarction of this area was observed in 12 of 13 rats. From 10 to 60 min after arterial occlusion, AVTT was nearly four times longer in the ischemic barrel cortex than at the same site before ligations, and fRBC flux was 25%. Neither parameter changed appreciably over this time. After 60 min of ischemia, ICBF on the ipsilateral barrel cortex was 18% of that on the contralateral side and 15% of the sham control value for the same area of the barrel cortex. Since whole blood flow in the ischemic barrel cortex was < 20% of normal at 60 min and AVTT and fRBC flux were essentially constant from 10 to 60 min, the rates of plasma and red cell flows were similarly depressed during the first hour of arteriolar occlusion. In conclusion, such lowering of red cell, plasma, and blood flows produced consistent infarctions in the barrel cortex.

Acute Disease↗

PubMed1998

Genetic variability and characterization of non-structural region 5 of hepatitis C virus genome from Chinese patients.

Sequence variation in the putative non-structural region 5b (NS5b) of hepatitis C virus (HCV) was analyzed in China. Complementary DNA fragments from sera of 49 Chinese patients were amplified by polymerase chain reaction (PCR) and the products were cloned and sequenced. Based on the comparison in NS5b of 33 clones of genotype 1b and 16 clones of genotype 2a, Chinese isolates of HCV belong to the same subtype as HCV-J, and HC-J6 from Japan. There does exist, however, some heterogeneity in the primary structure of the nucleotide acid. Higher homology was found among Chinese isolates than among Chinese isolates and Japanese isolates. Furthermore, among Chinese isolates, we found some conserved nucleotide acid positions different from those of Japanese isolates. Comparison of average homology among the 33 clones of genotype 1b and the 16 clones of genotype 2a indicated that the average homology among genotype 2a was lower than that among genotype 1b. In addition, a deletion of three nucleotide acids and a frame-shift, resulting in the introduction of an in-frame stop codon, were first observed in the NS5b region. These results indicated geographical differences in the distribution of individual HCV isolates, and the existence of a local variant in the same subtype. Our findings also suggested the need for further study on the sequence of genotype 2a, to improve diagnosis and help to advance the development of a vaccine.

Adult↗

PubMed1998

Relationship between interferon therapy and variability in nonstructural gene 5b of hepatitis C virus.

The hepatitis C virus (HCV) quasispecies nature in the hypervariable region (HVR) has been reported and found to relate to the effectiveness of interferon (IFN) treatment. However, the quasispecies nature in the nonstructural (NS) 5b region remains to be addressed. To examine this characterization and relationship with IFN therapy, we sequenced six independent HCV clones from each of eight patients. The eight patients were classified as responders or nonresponders to IFN. In the four responders, we found one to three isolates in each of the six clones. In the nonresponders, the six clones consisted of four, five, six, and six isolates, respectively. Compared the (NS) 5b genes of the isolates obtained from the patients with that of the reported hepatitis C virus HC-C2 or HC-J6 isolate the ratio of nonsynonymous to total substitutions ranged from 17.61% to 30.95% in the responders and from 33.11% to 76.47% in the nonresponders. We also compared posttreatment with pretreatment sequences. The average number of varying amino acids ranged from 5.5 to 9.0 in isolates remaining after IFN treatment and from 4.3 to 5.5 in the isolates that disappeared with IFN treatment. Two changed amino acids (glycine to arginine and valine to isoleucine) (compared with the pretreatment clones) were found in the posttreatment clones of one of the responders and one amino acid change (valine to alanine) was found in another responder. These results suggest that the NS5b quasispecies correlates with IFN treatment effectiveness. These results also implied that the heterogeneity in different hierarchical strata has a common impact on IFN treatment, making infected patients resistant to IFN. Our study also provides evidence that HCV elimination and mutation may occur simultaneously during IFN therapy.

Adult↗

PubMed1998

Lifelong ethanol consumption and loss of locus coeruleus neurons in AA and ANA rats.

The effects of lifelong ethanol exposure and aging on the morphology of the locus coeruleus (LC) were studied in the AA (Alko, Alcohol) and ANA (Alko, Nonalcohol) rats of both sexes. The ethanol-consuming (EtOH) rats were given 12% (v/v) ethanol as the only drinking fluid from 4 to 22 months of age, whereas the young (3-month-old) and aged (24-month-old) controls had only water available. The total LC neuron numbers were obtained by using the unbiased disector method. In the AA line, as we have previously reported. the EtOH female and male rats displayed a 26-30% loss of LC neurons compared with the controls. In the ANA line, the EtOH females had 30% fewer LC neurons than the controls (EtOH 1579 +/- 377 vs. controls 2264 +/- 269, ANOVA p < 0.01), whereas the EtOH males showed no neuron loss compared to the controls (EtOH 1848 +/- 525 vs. controls 2216 +/- 152, ANOVA NS). However, taking into account (sex by line ANCOVA) the markedly higher ethanol intake of the female rats in both lines, no gender or line differences in the ethanol-induced LC degeneration were detected. Neither was there any difference in LC neuron numbers between the young and old control rats of either line of rats. In conclusion, chronic alcohol consumption, not aging per se, damages the LC neurons in experimental animals.

Acetaldehyde↗

PubMed1998

Characterization of the Lactobacillus helveticus groESL operon.

This study utilized inverse polymerase chain reactions to characterize a 2.7-kb region of the Lactobacillus helveticus LH212 chromosome that included two complete and one truncated open reading frames (ORFs). Protein homology searches showed that the first two ORFs encoded homologs to the universally conserved heat shock proteins GroES and GroEL. Amino acids encoded by the 5' end of the truncated ORF that was downstream of groEL showed good homology to the amino terminal end of the Streptococcus pneumoniae DNA mismatch repair enzyme HexA. Nucleotide sequence analysis identified a putative transcriptional promoter upstream of groES that was comprised of -35 and -10 hexamers flanked upstream and downstream by copies of the conserved Gram-positive heat shock gene regulatory sequence, CIRCE. A large inverted repeat that may function as a rho-independent transcriptional terminator was located between groEL and the third ORF. Northern hybridization of an LH212 groEL gene fragment to RNA isolated from cells that had been heat shocked at 52 degrees C for 0, 5, 10 or 15 min detected a 2.2-kb transcript in each of the cell preparations. Densitometry showed the concentration of this mRNA species was approximately 4-fold higher after heat shock for 5 or 10 min and 3-fold higher after 15 min of heat shock.

Bacterial Proteins↗

PubMed1998

Proteoglycan turnover during development of spontaneous osteoarthrosis in guinea pigs.

OBJECTIVE: The study was performed to clarify the metabolic background of the variations in proteoglycan concentrations, relating to ageing and the spontaneous development of osteoarthrosis in guinea pigs. METHODS: Six-, 9- and 12-month-old Hartley guinea pigs were injected intraperitoneally with Na2(35)SO4. The incorporation and degradation of various proteoglycans were analyzed in different areas of tibial articular cartilage during the development of osteoarthrosis. RESULTS: Proteoglycan synthesis was most active in the uncalcified cartilage of 6-month animals and highest in the medial compartment with its presumably higher load. The breakdown of proteoglycans decreased with age. The onset of osteoarthrosis was associated with decreased synthesis of large and small proteoglycans, while the rate of degradation remained unchanged. CONCLUSION: During onset of osteoarthrosis the synthesis of large proteoglycans gradually becomes insufficient to compensate for the simultaneous degradation. This differs from findings in more rapidly progressing, experimental secondary osteoarthrosis, where a substantial increase in the rate of degradation is more conspicuous.

Aging↗

PubMed1998

The Caenorhabditis elegans unc-64 locus encodes a syntaxin that interacts genetically with synaptobrevin.

We describe the molecular cloning and characterization of the unc-64 locus of Caenorhabditis elegans. unc-64 expresses three transcripts, each encoding a molecule with 63-64% identity to human syntaxin 1A, a membrane- anchored protein involved in synaptic vesicle fusion. Interestingly, the alternative forms of syntaxin differ only in their C-terminal hydrophobic membrane anchors. The forms are differentially expressed in neuronal and secretory tissues; genetic evidence suggests that these forms are not functionally equivalent. A complete loss-of-function mutation in unc-64 results in a worm that completes embryogenesis, but arrests development shortly thereafter as a paralyzed L1 larva, presumably as a consequence of neuronal dysfunction. The severity of the neuronal phenotypes of C. elegans syntaxin mutants appears comparable to those of Drosophila syntaxin mutants. However, nematode syntaxin appears not to be required for embryonic development, for secretion of cuticle from the hypodermis, or for the function of muscle, in contrast to Drosophila syntaxin, which appears to be required in all cells. Less severe viable unc-64 mutants exhibit a variety of behavioral defects and show strong resistance to the acetylcholinesterase inhibitor aldicarb. Extracellular physiological recordings from pharyngeal muscle of hypomorphic mutants show alterations in the kinetics of transmitter release. The lesions in the hypomorphic alleles map to the hydrophobic face of the H3 coiled-coil domain of syntaxin, a domain that in vitro mediates physical interactions with similar coiled-coil domains in SNAP-25 and synaptobrevin. Furthermore, the unc-64 syntaxin mutants exhibit allele-specific genetic interactions with mutants carrying lesions in the coiled-coil domain of synaptobrevin, providing in vivo evidence for the significance of these domains in regulating synaptic vesicle fusion.

Amino Acid Sequence↗

PubMed1998

Characterization of 19 disease-associated missense mutations in the regulatory domain of the cystic fibrosis transmembrane conductance regulator.

In order to gain a better insight into the structure and function of the regulatory domain (RD) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, 19 RD missense mutations that had been identified in patients were functionally characterized. Nine of these (I601F, L610S, A613T, D614G, I618T, L619S, H620P, G628R and L633P) resulted in aberrant processing. No or a very small number of functional CFTR proteins will therefore appear at the cell membrane in cells expressing these mutants. These mutations were clustered in the N-terminal part of the RD, suggesting that this subdomain has a folding pattern that is very sensitive to amino acid changes. Mutations that caused no aberrant processing were further characterized at the electrophysiological level. First, they were studied at the whole cell level in Xenopus laevis oocytes. Mutants that induced a whole cell current that was significantly different from wild-type CFTR were subsequently analysed at the single channel level in COS1 cells transiently expressing the different mutant and wild-type proteins. Three mutant chloride channels, G622D, R792G and E822K CFTR, were characterized by significantly lower intrinsic chloride channel activities compared with wild-type CFTR. Two mutations, H620Q and A800G, resulted in increased intrinsic chloride transport activities. Finally, T665S and E826K CFTR had single channel properties not significantly different from wild-type CFTR.

Amino Acid Sequence↗

PubMed1998

Isolated U-fiber involvement in MS: preliminary observations.

We studied the frequency and location of isolated U-fiber involvement in MS and correlated these findings exploratively with physical disability and neuropsychological impairment. Fifty-three MS patients were examined. Three-millimeter-thick, fast spin-echo T2-weighted MR images and spin-echo postgadolinium T1-weighted images were obtained. Computer software that which had been validated previously for quantitation of MS lesions was used to detect lesions on the T2-weighted images. The Expanded Disability Status Scale (EDSS), Ambulation Index (AI), and a battery of neurocognitive tests were performed on each patient. Forty-two arcuate hyperintensities along the U-fiber were detected by the software in 28 patients (53%). Twenty-seven lesions (64.3%) were seen in the frontal lobe, eight (19.0%) in the temporal lobe, three (7.1%) in the parietal lobe, three (7.1%) in the occipital lobe, and one (2.4%) in both frontal and parietal lobes. Four lesions (9.5%) showed gadolinium enhancement. Seventeen lesions (40%) were hypointense on the T1-weighted images. Scores of three of the 11 neuropsychological tests reflecting performance in executive control and memory were significantly different at least at the p = 0.05 level between the eight patients with multiple, isolated U-fiber lesions and the 45 patients without any or with only a single U-fiber lesion. No significant difference was noted for EDSS or AI. Isolated U-fiber involvement is an underappreciated MR finding in MS. Our preliminary hypothesis is that U-fiber lesions may contribute to neuropsychological impairment, although our observation requires confirmation.

Adult↗

PubMed1998

Correlation of volumetric magnetization transfer imaging with clinical data in MS.

We examined the relations between quantitative volumetric estimates of cerebral lesion load based on magnetization transfer imaging (MTI), clinical data, and measures of neuropsychological function in 44 patients with clinically diagnosed MS. In this population we assessed the correlation between several volumetric MTI measures, measures of neurologic function (Kurtzke Expanded Disability Status Scale and Ambulation Index), and disease duration using Spearman's correlation coefficient. Patients were classified on the basis of neuropsychological test performance as severely impaired, moderately impaired, and normal. We assessed differences between these groups with respect to MTI results using the Kruskal-Wallis test. MTI measures corrected for brain volume were found to correlate with disease duration (p < 0.01) and showed suggestive correlations with measures of neurologic impairment (p < 0.05). Individual neuropsychological tests correlated with MTI measures corrected and not corrected for brain volume (p < 0.001). An MTI measure not corrected for brain volume differed (p < 0.05) between severely impaired, moderately impaired, and normal patients. These preliminary results suggest that volumetric MTI analysis provides new measures that reflect more accurately the global lesion load in the brain of MS patients, and they may serve as a method to study the natural course of the disease and as an outcome measure to evaluate the effect of drugs.

Adult↗

PubMed1998

Mechanical load and primary guinea pig osteoarthrosis.

Hartley guinea pigs spontaneously develop knee osteoarthrosis. The reproducible course, the changes first appearing at the central medial condyle and then progressing peripherally and laterally, makes this animal a suitable model for intervention studies. We studied the effect of load, and randomized 9-month-old male animals into 4 groups: immediate killing, mid-femoral 30 degrees-valgus osteotomy, sham operation or below-knee amputation. After 3 months, the proximal tibia was step-sectioned and examined stereologically by light microscopy. Local load-redistribution from the medial to the lateral condyle (osteotomy) reduced cartilage fibrillation by 22% medially and increased it 27% laterally. Subchondral bone thickness decreased by 36% in the medial condyle. In contrast, general load-redistribution (amputation) did not affect the progress of fibrillation, despite pronounced bone atrophy. Cartilage thickness, however, did not change; calcified cartilage thickness remained remarkably constant, and it was always higher on the lateral side. Therefore tide-mark advancement does not appear to be an important mechanism in early guinea pig osteoarthrosis. Thus, when the natural course of guinea pig osteoarthrosis is interfered with surgically, in the early phase, changes in bone are more conspicuous than those in cartilage, which further indicates that mechanical load and stiffness gradients are important pathogenetic mechanisms.

Amputation, Surgical↗

PubMed1998

[Relationship between the expression level of alpha-MHC gene and cardiac contractility during heart failure].

To investigate the molecular basis of the decrease in myocardial contractility during heart failure, an animan model of heart failure was set up by means of deoxycorticosterone-acetate impregnated silicone rubber implants in wistar rats. Cardiac contractility in normal and heart failure rats was examined, and gene expression of its myocardial contractile protein, alpha-MHC, was quantitatively analyzed at gene transcription level by using RNA slot blot hybridization. The results showed that the cardiac contractility and the alpha-MHC mRNA levels in heart failure rats were all lower than those in the normal. Statistical analysis showed a positive correlation between the cardiac contractility and the gene expression of alpha-MHC (r = 0.4143, n = 43, P < 0.05). The above results indicate that gene expression level of alpha-MHC is one of the key factors determining cardiac contractility.

Animals↗