Biomedical subjects

Lei Chen

Publications and source records attributed to Lei Chen.

At least 163 records · Page 9Linked to original sources

PubMed2003

Requirement of subunit expression for cAMP-mediated regulation of a heart potassium channel.

Beta-adrenergic receptor stimulation increases heart rate and shortens ventricular action-potential duration, the latter effect due in part to a cAMP-dependent increase in the slow outward potassium current (I(Ks)). Mutations in either KCNQ1 or KCNE1, the I(Ks) subunits, are associated with variants (LQT-1 and LQT-5) of the congenital long QT syndrome. We now show that cAMP-mediated functional regulation of KCNQ1/KCNE1 channels, a consequence of cAMP-dependent protein kinase A phosphorylation of the KCNQ1 N terminus, requires coexpression of KCNQ1 with KCNE1, its auxiliary subunit. Further, at least two KCNE1 mutations linked to LQT-5 (D76N and W87R) cause functional disruption of cAMP-mediated KCNQ1/KCNE1-channel regulation despite the response of the substrate protein (KCNQ1) to protein kinase A phosphorylation. Transduction of protein phosphorylation into physiologically necessary channel function represents a previously uncharacterized role for the KCNE1 auxiliary subunit, which can be disrupted in LQT-5.

Amino Acid Sequence↗

PubMed2003

Sonographic staging of the developmental status of mouse embryos in utero.

In mouse developmental studies it is frequently desirable to isolate embryos of a specific age. However, the traditional staging of embryonic development based on postcoital dates often erroneously predicts the embryonic age, resulting in unwarranted sacrifice of the pregnant mother. Here we report a noninvasive way of staging embryonic development in utero. A clinical 14 MHz ultrasound system was employed to assess the morphology and size of developing embryos from embryonic day 7.5 to 18.5. We demonstrate that the developmental age of the mouse embryos can be accurately determined based on the sonographic morphology and size of the embryos. This noninvasive ultrasound application requires no anesthesia of the mice and the entire process of staging can be completed within 5-10 min. Empirically, this approach is applicable to mice of various genetic backgrounds and significantly enhances the efficiency of studying murine embryogenesis.

Animals↗

PubMed2003

A novel matrix protein participating in the nacre framework formation of pearl oyster, Pinctada fucata.

Understanding the molecular composition is of great interest for both nacre formation mechanism and biomineralization in mollusk shell. A cDNA clone encoding an MSI31 relative, termed MSI7 because of its estimated molecular mass of 7.3 kDa, was isolated from the pearl oyster, Pinctada fucata. This novel protein shares similarity with MSI31, a prismatic framework protein of P. fucata. It is peculiar that MSI7 is much shorter in size, harboring only the Gly-rich sequence that has been proposed to be critical for Ca(2+) binding. In situ hybridization result showed that MSI7 mRNA was expressed specifically at the folds and outer epithelia of the mantle, indicating that MSI7 participates in the framework formation of both the nacreous layer and prismatic layer. In vitro experiment on the function of MSI7 suggested that it accelerates the nucleation and precipitation of CaCO(3). Taken together, we have identified a novel matrix protein of the pearl oyster, which may play an important role in determining the texture of nacre.

Amino Acid Sequence↗

PubMed2003

Transformation of tobacco with genes encoding Helianthus tuberosus agglutinin (HTA) confers resistance to peach-potato aphid (Myzus persicae).

The effects of the hta gene encoding Helianthus tuberosus agglutinin (HTA) on an insect in the order Homoptera were investigated. Homologous cDNAs of hta-a, hta-b, hta-c and hta-d with CaMV35S as promoter were introduced into tobacco via Agrobacterium tumefaciens. Southern blot results showed that the exogenous hta gene was inserted into the genome of host plants, and northern blot analysis confirmed that hta was expressed in transgenic plants. A bioassay with peach-potato aphid (Myzus persicae) demonstrated that transgenic plants had deleterious effects on the insect. The average population of aphids fed on transgenic T0 plants during an 11-day assay decreased by 70%, compared controls. In transgenic plants of T1 generation, aphid fecundity inhibitions were 53.0% (hta-b) and 64.6% (hta-c), respectively. The development of aphids was notably retarded. We conclude that hta could be a novel and promising candidate for plant transgenic engineering against homopteran insect pests.

Agglutinins↗

PubMed2003

Isolation and identification of a super strong plant promoter from cotton leaf curl Multan virus.

The activity of the C1 and the V1 gene promoter of cotton leaf curl Multan virus (CLCuMV) was investigated in transgenic plants with the gus gene as a reporter gene. Quantitative GUS activity analysis of the transgenic plant leaves showed the average activity of the CLCuMV C1 gene promoter was 3- to 5-fold higher than that of the CaMV 35S promoter, with maximal expression being 10-fold higher. CLCuMV V1 gene promoter activity was only about 1/10th that of the CaMV 35S promoter in the absence of trans-activator C2. Histochemical GUS staining of the transgenic plants indicated that the CLCuMV C1 gene promoter was active in leaves, stems, roots and almost all reproductive organs. Functional analysis of promoter 5'-deletion series indicated that promoter activity of a 257 nucleotide fragment (-257 to the transcription initiation site) and a 241 nucleotide fragment (-241 to the transcription initiation site) were 5-fold and 2-fold stronger than that of the full-length CLCuMV C1 promoter respectively. These results demonstrate that the CLCuMV C1 promoter is a super-strong near-constitutive promoter in plants and has great application potential for plant genetic engineering studies.

Base Sequence↗

PubMed2003

Spiral growth and cell wall properties of the gibberellin-treated first internodes in the seedlings of a wheat cultivar tolerant to deep-sowing conditions.

The Hong Mang Mai wheat cultivar is tolerant to deep-sowing conditions because it has an elongated first internode that is sensitive to gibberellin (GA3). The cells in the GA-treated first internodes were approximately 4.2 mm long, twice as long as the untreated Hong Mang Mai first internode cells. The elongation of the first internode of Hong Mang Mai, particularly when treated with GA3, was accompanied by remarkable spiral growth. In contrast, the first internodes of the GA-insensitive cultivar Norin 10 did not exhibit GA3-induced elongation or spiral growth. The walls of the first internode cells of GA3-treated Hong Mang Mai seedlings showed increased extensibility and higher (1-->3), (1-->4)-beta-d-glucanase activity, autolysis and glucan contents than the cell walls of untreated Hong Mang Mai first internodes. The changes in the cell wall extensibility due to GA3 treatment correlated strongly with the GA3-induced changes in cell wall glucan content, autolysis, and glucanase activity. GA3-treated Hong Mang Mai seedlings showed elevated expression of Glucanase EI gene in the first internode compared to GA3-treated Norin 10. Thus, GA aids first internode elongation in Hong Mang Mai by enhancing glucan turnover and thus increasing cell wall loosening. The spiral growth of the first internode also helps the plant elongate against soil resistance, thereby promoting the deep-sowing tolerance of this cultivar.

Journal Article↗

PubMed2003

Improved forage digestibility of tall fescue (Festuca arundinacea) by transgenic down-regulation of cinnamyl alcohol dehydrogenase.

Lignification of cell walls during plant development has been identified as the major factor limiting forage digestibility and concomitantly animal productivity. cDNA sequences encoding a key lignin biosynthetic enzyme, cinnamyl alcohol dehydrogenase (CAD), were cloned from the widely grown monocotyledonous forage species tall fescue (Festuca arundinacea Schreb.). Recombinant tall fescue CAD expressed in E. coli exhibited the highest V(max)/K(m) values when coniferaldehyde and sinapaldehyde were used as substrates. Transgenic tall fescue plants carrying either sense or antisense CAD gene constructs were obtained by microprojectile bombardment of single genotype-derived embryogenic suspension cells. Severely reduced levels of mRNA transcripts and significantly reduced CAD enzymatic activities were found in two transgenic plants carrying sense and antisense CAD transgenes, respectively. These CAD down-regulated transgenic lines had significantly decreased lignin content and altered ratios of syringyl (S) to guaiacyl (G), G to p-hydroxyphenyl (H) and S to H units. No significant changes in cellulose, hemicellulose, neutral sugar composition, p-coumaric acid and ferulic acid levels were observed in the transgenic plants. Increases of in vitro dry matter digestibility of 7.2-9.5% were achieved in the CAD down-regulated lines, thus providing a novel germplasm to be used for the development of grass cultivars with improved forage quality.

Journal Article↗

PubMed2003

Evidence for impaired axonal regeneration in PMP22 duplication: studies in nerve xenografts.

Whether axonal regeneration in Charcot-Marie-Tooth (CMT) neuropathies is impaired has not been addressed in detail. Our studies in nude mice harboring xenografts from patients with different primary Schwann cell (SC) genetic defects suggested an intimate association between the onset of myelination and impairment in the growth capacity of nude mice axons engulfed by the mutant SCs. To assess the effects of peripheral myelin protein 22 (PMP22) gene duplication on the regeneration process, we conducted morphometric studies to generate temporal growth profiles of myelinated axons within the xenografts obtained from CMT1A patients and from healthy controls. Axon size distribution histograms in controls at different time intervals revealed that size differentiation of myelinated fibers within the grafts is established as early as 2 weeks, and that the temporal pattern of myelination of different sized axons has striking similarities to myelination during development. In PMP22 duplication grafts, the onset of myelination is delayed and the regeneration capacity of all fiber sizes is impaired. This defect, however, is most pronounced for the large diameter axons. In addition, significant large fiber loss occurred after 12 weeks with a concomitant new cycle of regeneration of small size axons. These studies show that the PMP22 duplication in SCs have profound effects on the regeneration process, which might be a contributing factor to preferential distal axonal loss.

Adult↗

PubMed2003

Lower respiratory infections in children.

Lower respiratory infections (LRIs) continue to threaten the health of children worldwide and are exacerbated by global environmental problems such as air pollution [1]. In the developing world where nutrition remains poor and access to healthcare is scarce, LRIs are the most common cause of illness and death in children. Outcomes of LRI illness are far better in developed countries, but the overall morbidity of LRI is still high and may exceed that of other age groups [2]. The environmental "health" of our planet remains an issue closely linked to the health of children--particularly in terms of LRI disease. It is also clear that further progress in preventing, diagnosing, and treating LRI disease will have a significant impact on the health of children. The recent literature details both progress and clinical dilemmas of LRI-related illnesses in children. Lower respiratory infection disease is considered to include the following entities: acute lower respiratory infections, pneumonia, atypical pneumonia, bronchitis, and bronchiolitis. This update will review current reports on the evaluation of children with LRIs, bacterial and viral LRIs, and sequelae of LRIs.

Adolescent↗

PubMed2003

Preservation of caspase-3 subunits from degradation contributes to apoptosis evoked by lactacystin: any single lysine or lysine pair of the small subunit is sufficient for ubiquitination.

Procaspase-3 (p32) is processed by upstream caspases to p12 and p20 subunits, which heterodimerize. Concomitant with formation of the active heterotetramer, p20 is autoprocessed to p17. Treatment of HL-60 cells with lactacystin, a selective inhibitor of the proteasome, exponentially increased caspase-3-like hydrolytic activity and induced apoptosis but had little or no effect on the activity of upstream caspase-8, caspase-9, or granzyme B. Lactacystin treatment decreased the p32 zymogen and evoked the accumulation of the p17 and p12 subunits. Treatment of transfected human retinoblast 911 cells with a proteasome inhibitor evoked the accumulation of epitope-tagged p12, p17, and p20 but had no effect on p32 zymogen. This result suggests that caspase-3 subunits, in contrast to the zymogen, are unstable because of degradation by the ubiquitin-proteasome system. Ubiquitin conjugates of p12 and p17 accumulated in cells that were cotransfected with p12 and a caspase inactive mutant of p17. Substitution of arginine for all eight lysines of p12 almost abolished its ubiquitination. Any single lysine or lysine pair was sufficient for p12 ubiquitination. Lactacystin treatment of HL-60 cells induced proteolytic processing of the X-linked inhibitor of apoptosis (XIAP) and decreased full-length XIAP, which is known to have ubiquitin-protein ligase activity for active caspase-3. These findings indicate that caspase-3 subunits can be degraded by the ubiquitin-proteasome system and suggest that lactacystin induces apoptosis in part by disabling the ubiquitin-protein ligase function of XIAP and by stabilizing active caspase-3 subunits.

Acetylcysteine↗

PubMed2003

Endoscopic patterns of gastric mucosa and its clinicopathological significance.

AIM: To explore the correlation of magnifying endoscopic patterns and histopathology, Helicobacter pylori (H pylori) infection of the gastric mucosa. METHODS: Gastric mucosal patterns in 140 patients with chronic gastritis were studied using Olympus GIF-Q240Z magnifying endoscope. Histopathological examination, rapid urease test and Warrthin-Starry staining were taken with biopsy samples from the magnified sites of stomach. The magnifying endoscopic patterns were compared with histopathological results and H pylori detection. RESULTS: The pit patterns of gastric mucosa were classified as types A (round spot), B (short rod), C (branched), D (reticular) and E (villus). The detection rate of chronic atrophic gastritis (CAG) by magnifying endoscopy was 94.3% (33/35), which was significantly higher than that by routine endoscopy (22.9%, 8/35) (P<0.01). The pit patterns of 31 cases of intestinal metaplasia (IM) appeared as type E in 18 cases (58.1%), type D in 8 cases (25.8%) and type C in 5 cases (16.1%). Fourteen out of 18 patients (77.8%) with complete type (type I) of IM appeared as type E of pit patterns, whereas only 4 of 13 (30.8%) patients with incomplete type (types II and III) of IM appeared as type E (P<0.05). Collecting venules in the anterior of lower part of gastric corpus were subgrouped into types R (regular), I (irregular) and D (disappeared). H pylori infection was found in 12.2%(9/74), 60%(9/15) and 84.3%(43/51) cases in these types respectively. H pylori infection rate in type R was significantly lower than that in other two types (P<0.01). CONCLUSION: Magnifying endoscopy may have an obvious value in diagnosing chronic atrophic gastritis, intestinal metaplasia and H pylori infection.

Adolescent↗

PubMed2003

[Primary research of repairing large articular cartilage defect by tissue-engineering cartilage in rabbits].

OBJECTIVE: To investigate the feasibility of repairing the whole layer defects of tibial plateau by implanting tissue-engineering cartilage. METHODS: The chondrocytes of 2-week-old rabbits were cultured and transferred to the 3rd generation, and mixed with human placenta collagen-sponge. The whole layer defects of tibial plateau in adult rabbits were repaired by the tissue-engineering cartilage in the experimental group; the defects were left un-repaired in control group. The repair results of defects were observed after 4, 12 and 24 weeks. RESULTS: In experimental group, no obvious new cartilage formation was seen 4 weeks after operation; some new cartilage formation was found after 12 weeks. Histological observation showed that chondrocytes had irregular edge, honeycombing structure and that cartilage cavities formed around the chondrocytes. After 24 weeks, obvious new cartilage formation was found with smooth surface, and linked with the tissues around it, but the defect was not repaired completely; histological results showed that cartilage cavities formed and that cartilage matrix was stained positively for toluidine blue. In control group, the defect was not repaired. CONCLUSION: The tissue-engineering cartilage can repair the defects of the whole layer cartilage of tibial plateau in rabbits, it is feasible to repair the whole layer cartilage defects of tibial plateau by this method.

Animals↗

PubMed2003

[Repair of articular cartilage defect with homogeneous chondrocytes combined with pluronic].

OBJECTIVE: To investigate the possibility of repairing the cartilage cartilage defect with homogeneous chondrocytes combined with Pluronic. METHODS: Homogeneous cartilage chondrocytes of adult New Zealand rabbits were harvested and cultured in vitro, which were marked by 3H-TdR and mixed with Pluronic. The medial or lateral condyle defects were made (phi 4 mm, extending down to the calcified zone) in 20 rabbits. In the experimental group, the right defects were repaired by homogeneous chondrocytes combined with Pluronic; in the control group, the left defects were repaired by Pluronic only or were left un-repaired. The animals were sacrificed in the 4th, 8th and 16th weeks after operation respectively. The repair results were observed and the cell source of repair tissue was distinguished. RESULTS: In the experimental group, the cartilage defects were repaired by the cartilage-like tissue after 8 weeks of operation; the defects were completely filled with mature cartilage tissue, which integrated smoothly with articular cartilage 16 weeks later. In the control group, only a small amount fibrous tissues were seen on the surface of defects. Autoradiographic assessment showed that the repair cells came from the implants, but not from self-chondrocytes. CONCLUSION: It is a good way to repair articular cartilage defects with homograft of tissue engineering cartilage. It is a convenient method to mark with 3H-TdR to discriminate the resource of the repair cells.

Animals↗

PubMed2003

[Spatial orientation interaction mechanism between chondroitin sulfate and azure A].

The spatial orientation interaction mechanism of chondroitin sulfate (CS) and azure A (AA) was studied by spectrometry. The maximum binding number (N = 151) and the binding equilibrium constant (K = 5. 24 x 10(4)) were obtained. The molecular binding model of the interaction between AA and CS was established. The influence of the molar ratio of AA/CS, ethanol, hydroxypropyl-beta-cyclodextrin, triton X-100 and NaCl on the spectra of AA-CS complex was investigated. We conclude that the color change of complex depends on not only the electrostatic interaction between AA and CS but also the density of AA binding on CS. And the formation of the absorption peak at 550 nm and the color change of complex result mainly from the hydrophobic interaction between AA and AA binding on CS.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2003

[Study on quantitative assay of chondroitin sulfate with a spectrophotometric method of azure A].

A simple, accurate and rapid spectrophotmeric method was proposed for the determination of chondroitin sulfate. The method was based on the absorbances of AA-CS complex at 625 nm being in proportion to the chondroitin sulfate concentrations. The linear range was 0-30 micrograms.mL-1 (R = 0.999), and the recovery range was 97.4%-103.8%. The quantities of chondroitin sulfate in different sample were determined in this way.

Azure Stains↗

PubMed2003

[Effect of immunological orchitis on sperm specific enzyme and fertility].

OBJECTIVE: To investigate the effect of immunological orchitis on spermatic specific enzyme and fertility. METHODS: Experimental allergic orchitis (EAO) model of guinea pigs was duplicated. The histological and morphological changes of spermatic acrosomal protease and hyaluronidase, lactate dehydrogenase, sperm in epididymis and testes were observed by means of enzyme kinetical spectrophotometry and gelatin fixation of substrate thin membrane. RESULTS: The activity of acrosomal protease, hyaluronidase and spermatic cytoplasmic lactic dehydrogenase in the epididymis acrosomal enzyme system became low, and so did the quality of sperm in epididymis. Remarkable morphological changes of spermatogenic cells developed in the convoluted seminiferous tubules. CONCLUSIONS: EAO remarkably affects the fertility of male guinea pigs. The orchis and epididymal sperms might be the sites of action.

Acrosin↗

PubMed2003

Prediction of abdominal visceral obesity from body mass index, waist circumference and waist-hip ratio in Chinese adults: receiver operating characteristic curves analysis.

OBJECTIVE: To evaluate the sensitivity and specificity of body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) measurements in diagnosing abdominal visceral obesity. METHODS: BMI, WC, and WHR were assessed in 690 Chinese adults (305 men and 385 women) and compared with magnetic resonance imaging (MRI) measurements of abdominal visceral adipose tissue (VA). Receiver operating characteristic (ROC) curves were generated and used to determine the threshold point for each anthropometric parameter. RESULTS: 1) MRI showed that 61.7% of overweight/obese individuals (BMI > or = 25 kg/m2) and 14.2% of normal weight (BMI < 25 kg/m2) individuals had abdominal visceral obesity (VA > or = 100 cm2). 2) VA was positively correlated with each anthropometric variable, of which WC showed the highest correlation (r = 0.73-0.77, P < 0.001). 3) The best cut-off points for assessing abdominal visceral obesity were as followed: BMI of 26 kg/m2, WC of 90 cm, and WHR of 0.93, with WC being the most sensitive and specific factor. 4) Among subjects with BMI > or = 28 kg/m2 or WC > or = 95 cm, 95% of men and 90% of women appeared to have abdominal visceral obesity. CONCLUSION: Measurements of BMI, WC, and WHR can be used in the prediction of abdominal visceral obesity, of which WC was the one with better accuracy.

Abdomen↗

PubMed2002

The mechanosensory protein MEC-6 is a subunit of the C. elegans touch-cell degenerin channel.

Mechanosensory transduction in touch receptor neurons is believed to be mediated by DEG/ENaC (degenerin/epithelial Na+ channel) proteins in nematodes and mammals. In the nematode Caenorhabditis elegans, gain-of-function mutations in the degenerin genes mec-4 and mec-10 (denoted mec-4(d) and mec-10(d), respectively) cause degeneration of the touch cells. This phenotype is completely suppressed by mutation in a third gene, mec-6 (refs 3, 4), that is needed for touch sensitivity. This last gene is also required for the function of other degenerins. Here we show that mec-6 encodes a single-pass membrane-spanning protein with limited similarity to paraoxonases, which are implicated in human coronary heart disease. This gene is expressed in muscle cells and in many neurons, including the six touch receptor neurons. MEC-6 increases amiloride-sensitive Na+ currents produced by MEC-4(d)/MEC-10(d) by approximately 30-fold, and functions synergistically with MEC-2 (a stomatin-like protein that regulates MEC-4(d)/MEC-10(d) channel activity) to increase the currents by 200-fold. MEC-6 physically interacts with all three channel proteins. In vivo, MEC-6 co-localizes with MEC-4, and is required for punctate MEC-4 expression along touch-neuron processes. We propose that MEC-6 is a part of the degenerin channel complex that may mediate mechanotransduction in touch cells.

Animals↗