Biomedical subjects

L Zheng

Publications and source records attributed to L Zheng.

At least 163 records · Page 9Linked to original sources

PubMed1999

Espin contains an additional actin-binding site in its N terminus and is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization junctional plaque.

The espins are actin-binding and -bundling proteins localized to parallel actin bundles. The 837-amino-acid "espin" of Sertoli cell-spermatid junctions (ectoplasmic specializations) and the 253-amino-acid "small espin" of brush border microvilli are splice isoforms that share a C-terminal 116-amino-acid actin-bundling module but contain different N termini. To investigate the roles of espin and its extended N terminus, we examined the actin-binding and -bundling properties of espin constructs and the stoichiometry and developmental accumulation of espin within the ectoplasmic specialization. An espin construct bound to F-actin with an approximately threefold higher affinity (K(d) = approximately 70 nM) than small espin and was approximately 2.5 times more efficient at forming bundles. The increased affinity appeared to be due to an additional actin-binding site in the N terminus of espin. This additional actin-binding site bound to F-actin with a K(d) of approximately 1 microM, decorated actin stress fiber-like structures in transfected cells, and was mapped to a peptide between the two proline-rich peptides in the N terminus of espin. Espin was detected at approximately 4-5 x 10(6) copies per ectoplasmic specialization, or approximately 1 espin per 20 actin monomers and accumulated there coincident with the formation of parallel actin bundles during spermiogenesis. These results suggest that espin is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization.

Actins↗

PubMed1999

Synthesis and decomposition of transient-evoked otoacoustic emissions based on an active auditory model.

In this paper, transient-evoked otoacoustic emissions (TEOAE's) are synthesized by an active auditory model, and decomposed by continuous wavelet transform (CWT) to study the frequency-latency relationship and the generation of TEOAE signals. The controlled voltage sources that relate to the mobile mechanism of the outer hair cells (OHC's) are proposed to serve as the generation sources of TEOAE signals. The state-variable method is adopted to calculate the auditory model. The mother wavelet used in CWT is selected on basis of the model. The results of this study show that the simulated TEOAE signal is similar to the clinically detected ones not only in the time-domain waveform, but also in the frequency-latency relationship. It seems to be clear that the generation of TEOAE signals is related to the same active mechanism as the cochlear sharp frequency selectivity.

Adult↗

PubMed1999

WdChs4p, a homolog of chitin synthase 3 in Saccharomyces cerevisiae, alone cannot support growth of Wangiella (Exophiala) dermatitidis at the temperature of infection.

By using improved transformation methods for Wangiella dermatitidis, and a cloned fragment of its chitin synthase 4 structural gene (WdCHS4) as a marking sequence, the full-length gene was rescued from the genome of this human pathogenic fungus. The encoded chitin synthase product (WdChs4p) showed high homology with Chs3p of Saccharomyces cerevisiae and other class IV chitin synthases, and Northern blotting showed that WdCHS4 was expressed at constitutive levels under all conditions tested. Reduced chitin content, abnormal yeast clumpiness and budding kinetics, and increased melanin secretion resulted from the disruption of WdCHS4 suggesting that WdChs4p influences cell wall structure, cellular reproduction, and melanin deposition, respectively. However, no significant loss of virulence was detected when the wdchs4Delta strain was tested in an acute mouse model. Using a wdchs1Delta wdchs2Delta wdchs3Delta triple mutant of W. dermatitidis, which grew poorly but adequately at 25 degrees C, we assayed WdChs4p activity in the absence of activities contributed by its three other WdChs proteins. Maximal activity required trypsin activation, suggesting a zymogenic nature. The activity also had a pH optimum of 7.5, was most stimulated by Mg(2+), and was more inhibited by polyoxin D than by nikkomycin Z. Although the WdChs4p activity had a broad temperature optimum between 30 to 45 degrees C in vitro, this activity alone did not support the growth of the wdchs1Delta wdchs2Delta wdchs3Delta triple mutant at 37 degrees C, a temperature commensurate with infection.

Amino Acid Sequence↗

PubMed1999

Hec1p, an evolutionarily conserved coiled-coil protein, modulates chromosome segregation through interaction with SMC proteins.

hsHec1p, a Homo sapiens coiled-coil-enriched protein, plays an important role in M-phase progression in mammalian cells. A Saccharomyces cerevisiae protein, identical to Tid3p/Ndc80p and here designated scHec1p, has similarities in structure and biological function to hsHec1p. Budding yeast cells deleted in the scHEC1/NDC80 allele are not viable, but this lethal phenotype can be rescued by hsHEC1 under control of the endogenous scHEC1 promoter. At the nonpermissive temperature, significant mitotic delay, chromosomal missegregation, and decreased viability were observed in yeast cells with temperature-sensitive (ts) alleles of hsHEC1. In the hshec1-113 ts mutant, we found a single-point mutation changing Trp395 to a stop codon, which resulted in the expression of a C-terminally truncated 45-kDa protein. The binding of this mutated protein, hshec1-113p, to five identified hsHec1p-associated proteins was unchanged, while its binding to human SMC1 protein and yeast Smc1p was ts. Hec1p also interacts with Smc2p, and the binding of the mutated hshec1-113p to Smc2p was not ts. Overexpression of either hsHEC1 or scHEC1 suppressed the lethal phenotype of smc1-2 and smc2-6 at nonpermissive temperatures, suggesting that the interactions between Hec1p and Smc1p and -2p are biologically significant. These results suggest that Hec1 proteins play a critical role in modulating chromosomal segregation, in part, through their interactions with SMC proteins.

Alleles↗

PubMed1999

Mature T lymphocyte apoptosis--immune regulation in a dynamic and unpredictable antigenic environment.

Apoptosis of mature T lymphocytes preserves peripheral homeostasis and tolerance by countering the profound changes in the number and types of T cells stimulated by diverse antigens. T cell apoptosis occurs in at least two major forms: antigen-driven and lymphokine withdrawal. These forms of death are controlled in response to local levels of IL-2 and antigen in a feedback mechanism termed propriocidal regulation. Active antigen-driven death is mediated by the expression of death cytokines such as FasL and TNF. These death cytokines engage specific receptors that assemble caspase-activating protein complexes. These signaling complexes tightly regulate cell death but are vulnerable to inherited defects. Passive lymphokine withdrawal death may result from the cytoplasmic activation of caspases that is regulated by mitochondria and the Bcl-2 protein. The human disease, Autoimmune Lymphoproliferative Syndrome (ALPS) is due to dominant-interfering mutations in the Fas/APO-1/CD95 receptor and other components of the death pathway. The study of ALPS patients reveals the necessity of apoptosis for preventing autoimmunity and allows the genetic investigation of apoptosis in humans. Immunological, cellular, and molecular evidence indicates that throughout the life of a T cell, apoptosis may be evoked in excessive, harmful, or useless clonotypes to preserve a healthy and balanced immune system.

Animals↗

PubMed1999

Pentoxifylline inhibits TNF-alpha production from human alveolar macrophages.

Tumor necrosis factor-alpha (TNF-alpha) is an important proinflammatory cytokine. Recently, pentoxifylline (POF) has been shown to suppress the synthesis of TNF-alpha from lipopolysaccharide (LPS)-stimulated human monocytes in cell cultures and in vivo. The aim of this study was to investigate whether POF-induced suppression of TNF-alpha secretion affects peripheral blood monocytes (PBM) and alveolar macrophages (AM) equally, and whether POF is able to suppress the spontaneous TNF-alpha production from AM in pulmonary sarcoidosis in vitro. In seven patients without interstitial lung disease we studied the effect of POF on LPS-stimulated PBM and AM cultured for 24 h. In six patients with sarcoidosis we investigated the effect of POF on the enhanced spontaneous TNF-alpha production by AM in vitro. POF induced a dose-dependent suppression of the LPS-stimulated TNF-alpha production which was not different for PBM and AM, respectively. In sarcoidosis, POF inhibited the spontaneous TNF-alpha production of AM at 0.1 mM by 91% and at 1 mM by 98%. In conclusion, POF inhibits LPS-induced TNF-alpha production from PBM and AM to a similar extent and can also inhibit the exaggerated spontaneous TNF-alpha production from AM in sarcoidosis in vitro. This may be the basis for further clinical trials to evaluate POF as an immunotherapeutic agent in sarcoidosis.

Adult↗

PubMed1999

Effect of moist vs. dry bonding to normal vs. caries-affected dentin with Scotchbond Multi-Purpose Plus.

Recent research in dentin bonding demonstrated the superiority of moist bonding over dry bonding on normal dentin, but it is unclear if this technique is also superior in bonding to caries-affected dentin. The purpose of this study was to evaluate the SEM appearance and bond strength of Scotchbond Multi-Purpose Plus (SMPP) to normal vs. caries-affected dentin bonded under moist vs. dry conditions, with and without polyalkenoic acid in the primer. Extracted carious human third molars were ground down by means of 600-grit SiC paper until the carious dentin no longer stained with caries detector solution. The flat surfaces were then primed, bonded, and built up with resin composite. After soaking in water for 1 day, the teeth were serially sectioned vertically into 5 or 6 slabs 0.7 mm thick. The bonded caries-affected areas were isolated by means of an ultrafine diamond bur to create an hourglass configuration with a cross-sectional area of 0.9 mm2. Bonded normal dentin was isolated the same way. Each specimen was attached to a Bencor device and tested in tension to failure. SMPP bonds to dry, normal dentin were only half as strong (21+/-10 MPa, x +/- SD) as those made to moist, normal dentin (42+/-9 MPa, p<0.01). There was no significant difference between bonds made to normal vs. caries-affected dentin by means of the moist technique (42+/-9 vs. 48+/-4 MPa, respectively). Removal of the polyalkenoic acid from the primer lowered (p<0.05) the bond strength of SMPP to caries-affected dentin (38+/-8 MPa). The benefits of moist bonding extend to caries-affected dentin. The polyalkenoic acid in the SMPP primer contributes to the high bond strength that can be achieved to caries-affected dentin.

Analysis of Variance↗

PubMed1999

Helicobacter pylori and upper gastrointestinal symptoms in bronchiectasis.

The recently reported increase in seroprevalence of Helicobacter pylori, the causative pathogen in peptic ulceration, in bronchiectasis is unexplained. Therefore, the association of antibodies directed against cytotoxin-associated gene A(CagA), whose expression indicates virulence of H. pylori, and upper gastrointestinal symptoms in patients with stable bronchiectasis and healthy volunteers evaluated. One hundred patients (mean +/- SD age 55.1+/-16.7 yrs) and 94 healthy asymptomatic subjects (54.6+/-7.6 yrs) underwent clinical and physiological assessment and serum levels of anti-H. pylori CagA were determined using standard clinical and enzyme-linked immunosorbent assay techniques. Samples were positive for anti-H. pylori CagA in 11.7% of controls and 24% of bronchiectatic subjects (p = 0.03). There was, however, no association between serum H. pylori CagA immunoglobulin G level and forced expiratory volume in one second (FEV1), forced vital capacity (FVC), sputum volume, respiratory symptoms or upper respiratory gastrointestinal symptoms (p>0.05). Patients who suffered from acid regurgitation or upper abdominal distension had significantly lower FEV1 and FVC (as a percentage of the predicted value) compared to their counterparts. The results of anticytotoxin-associated gene A measurements in this study contrasted with the previous finding that anti-Helicobacter pylori immunoglobulin G correlated with sputum volume. These findings, therefore, suggest that Helicobacter pylori, should it have a pathogenic role in bronchiectasis, could act via noncytotoxin-associated gene A-mediated mechanisms, and, in this context, gastro-oesophageal reflux might be of importance in bronchiectasis.

Adult↗

PubMed1999

Isolated tetrasomy 8 in minimally differentiated acute myeloid leukemia (AML-M0).

Tetrasomy 8 as a sole anomaly in hematological disorders is relatively rare. To the best of our knowledge, only 19 such cases have been described in the literature to date. Of them, acute myeloid leukemia (AML) in 13 (M1, one; M2, three; M4, one; M5, eight), acute lymphoblastic leukemia(ALL) in one, myelodysplastic syndrome(MDS) in 3, polycythemia vera(PV) and myelofibrosis(MF), one case each. Their median survival was 20 weeks. Here, we report the first case of a 29-year-old man with minimally differentiated AML (AML-M0) displaying a tetrasomy 8 clone. Immunophenotyping showed positivity with CD33, CD34 and intracellular MPO, but all lymphoid markers tested were negative. Conventional cytogenetics of bone marrow cells showed 84.9% of metaphases with tetrasomy 8 in addition to 15.1% with normal diploidy. However, Fluorescence in situ hybridization(FISH) using a centromeric probe specific for chromosome 8 revealed trisomy 8 in 14.2% of interphase nuclei besides tetrasomy 8 in 82.4%. The patient died four weeks after diagnosis without therapy. In conclusion, these findings suggest that tetrasomy 8 is associated with a heterogeneous group of myeloid disorders and heralds a bad prognosis. It may be a consequence of clonal evolution of trisomy 8.

Acute Disease↗

PubMed1999

[Using the method of two-color fluorescence in situ hybridization to detect aneuploidy of human sperms].

OBJECTIVE: To develop the method of two-color fluorescence in situ hybridization (FISH) assay and use it for detecting the aneuploidy frequency of human sperm chromosome. METHODS: Sperm sample was washed three times and the slides were prepared. The sperm heads were decondensed with dithiothreitol (DTT) and lithium diiodosalicylate (LIS). Then, the sperm nuclei were hybridized with biotin labeled alpha satellite X chromosome DNA probe (DXZ1) and digoxigenin labeled alpha satellite Y chromosome DNA probe (DYZ3). The hybridization signals were detected with CY3-Streptavidin, goat antistrepavidin for biotin labeled probe and with mouse antidigoxigenin, rabbit antimouse-FITC for digoxigenin labeled probe. RESULTS: Under the Nikon fluorescence microscope, the hybridization signals in the sperm heads were clearly visible. The sperm with one red hybridization signal was X chromosome sperm (X sperm), and the sperm with one green hybridization signal in the sperm head was Y chromosome sperm (Y sperm). In the case of two hybridization signals in one sperm head, the sperm should be a numerical abnormal one. By using two color FISH with one euchromosome probe and one sex chromosome probe, the sperm with same color of two hybridization signals in one sperm head could be identified as aneuploidy sperm or diploid sperm. CONCLUSION: The two color FISH assay may be used to detect the aneuploidy frequency of human sperms that were exposed to mutagents and environmental potential aneuoploidogenic agents.

Aneuploidy↗

PubMed1999

Cloning and use of the WdURA5 gene as a hisG cassette selection marker for potentially disrupting multiple genes in Wangiella dermatitidis.

A genomic clone encoding the Wangiella dermatitidis orotidine monophosphate pyrophosphorylase gene (WdURA5) was isolated by screening a subgenomic plasmid DNA library of this phaeohyphomycotic agent using a PCR amplification product of the gene as a probe. When plasmid DNA containing the cloned WdURA5 gene was introduced by electroporation into a wdura5 auxotrophic recipient strain derived previously by selection with 5-fluoroorotic acid (5-FOA), an apparent gene repair event occurred at high frequency without any evidence of integration of the plasmid DNA. Therefore, the hygromycin B resistance gene (the hph gene) was used as a dominant selective marker for the disruption of WdURA5 to generate a new, more stable, wdura5 auxotrophic strain. Transformation of this strain was then achieved with high efficiency and high frequency by site-specific integration using WdURA5 as a selective marker. To initiate attempts to use this marker repeatedly for multiple chitin synthase (WdCHS) gene disruptions in single strains of W. dermatitidis, a hisG_WdURA5_hisG cassette was constructed and used to disrupt WdCHS2. The WdURA5 gene in the disruptant was then successfully recycled under selection for resistance to 5-FOA.

Amino Acid Sequence↗

PubMed1999

Analysis of phosphorescence decay in heterogeneous systems: consequences of finite excitation flash duration.

Analysis of phosphorescence lifetimes using the Stern-Volmer equation is a reliable means of determining quencher concentration for a uniform sample. Methods of analysis for heterogeneous systems are based on the assumption that the excitation is produced by a momentary flash. This condition is an idealization because a real flash has a finite duration and a complex time profile. In the case of a heterogeneous quencher concentration, an excitation flash produces different initial intensities and different times of peak intensity from compartments having different concentrations of quencher. We formulated a model to explore the effects of flash duration on the shape of the emission curve obtained from systems in which the heterogeneity is continuous. We developed mathematical models that can be used to recover fitting parameters of continuous distributions of reciprocal lifetimes approximated as rectangular or Gaussian distributions, or an arbitrary histogram. We also formulated a procedure to convert the distribution of reciprocal lifetimes into a volume distribution of quencher concentration. We found that (1) the Stern-Volmer ratio of phosphorescence intensities cannot be employed for interpretation of pulse phosphorometric data in terms of a volume distribution of quencher; (2) shortening the flash duration decreases the difference of initial intensities between compartments having high and low quencher concentration; (3) the parameters of the volume distribution of quencher concentration can be recovered correctly only after taking account of the difference in initial intensities; and (4) calibration of the initial intensities for a given fitting delay and flash function is necessary.

Kinetics↗

PubMed1999

Interferon-beta inhibits activated leukocyte migration through human brain microvascular endothelial cell monolayer.

Perivascular leukocyte infiltration into the central nervous system is characteristic of multiple sclerosis (MS) pathology. Interferon-beta (IFN-beta) has shown efficacy in the treatment of patients with MS, but the relevant mechanisms remain incompletely understood. In this study the effects of IFN-beta on leukocyte transendothelial migration were investigated using cells relevant to MS pathogenesis, namely human brain microvascular endothelial cells (HB-MVEC). Activated, but not resting leukocytes exhibited a high transendothelial migration capacity. HB-MVEC prestimulated with tumor necrosis factor (TNF) and IFN-gamma significantly promoted leukocyte transendothelial migration. IFN-beta inhibited the activated leukocyte transendothelial migration on TNF/IFN-gamma-activated HB-MVEC in a dose-dependent manner. A matrix metalloproteinase (MMP) inhibitor and monoclonal antibodies to lymphocyte function antigen-1 (LFA-1) or intercellular adhesion molecule-1 (ICAM-1), but not to very late antigen-4 or to vascular cell adhesion molecule-1 significantly inhibited the transendothelial migration of stimulated leukocytes, suggesting that this phenomenon involves the LFA-1/ICAM-1 interaction and MMP. However IFN-beta did not interfere with the binding of leukocytes to HB-MVEC unless IFN-beta was preincubated with leukocytes or added to HB-MVEC at the time of stimulation. Furthermore IFN-beta did not modulate the expression of adhesion molecules on either stimulated leukocytes or activated HB-MVEC, but partially reduced TNF and interleukin-1 production from stimulated leukocytes during coculture with HB-MVEC. Interestingly, in the presence of IFN-beta, a significant down-regulation of MMP-9 release from stimulated leukocytes was found, especially for the activated form of MMP-9. These results indicate that inhibition of leukocyte transendothelial migration is an important mechanism accounting for the beneficial effects of IFN-beta in the treatment MS patients.

Brain↗

PubMed1999

Study on pottical type, palmar and plantar digital formulae, hand clasping, arm folding, handedness, leg folding and stride type in the Daur population, China.

The pottical type, palmar and plantar digital formulae, hand clasping, arm folding, handedness, leg folding and stride type have been investigated on a sample of 143 male and 160 female students of the Daur population of Molidawa Banner, Inner Mongolia. The results of this study are the following: 1. the frequency of the hyperextensive pottical type is 49.17%, the relative length of index over annularis 12.21%, right hand clasping 45.87%, right arm folding 49.50%, right handedness 94.39%, right leg folding 72.28% and right stride type 44.88%, 2. pottical type, hand clasping, handedness, leg folding and stride type do not show significant sex differences, 3. there are some relations between hand clasping and arm folding as well as between arm folding and stride type, 4. compared with other population groups, the Daur population shows a low frequency of right hand clasping, a moderate frequency of right arm folding and a low frequency of left handedness.

Adolescent↗

PubMed1999

Genetic basis of encapsulation response in Anopheles gambiae.

The phenomenon of encapsulation of invading organisms is widespread in insects. Co-evolution has produced an intricate balance between the immune responses of the host and immune-suppressive (or immune-evading) properties of the parasite. Genome-wide genetic mapping revealed different loci in Anopheline mosquitoes were involved in melanotic encapsulation of different malaria parasites. Certain isolates of human malaria parasites can still suppress or avoid the immune response from refractory mosquitoes. Similar interactions with parasitoids were observed in Drosophila melanogaster. Species-specific encapsulation locus was identified for two parasitoids, respectively, and virulent strain of parasitoid can suppress the immune system of an otherwise resistant fruitfly. It is believed that the encapsulation loci in both mosquitoes and fruitfly may encode gene products that function at the early stages of parasite/parasitoid recognition or immediate signaling events. Future research on membrane receptor molecules and their roles in insect immunity will yield interesting insights into mosquito-parasite interactions.

Animals↗

PubMed1999

[The complications of excimer laser in-situ keratomileusis for myopia].

OBJECTIVE: To analyze the complications of excimer laser in-situ keratomileusis (LASIK) for myopia, investigate the causes and discuss the prevention of these complications. METHODS: The SCMD microkeratome and Schwind Keratom F excimer laser were used to correct myopia on 1,265 eyes in 662 cases. The eyes were divided into 3 groups: A: -10.00 D, 252 eyes. All of them were followed up for a period of 12 months. RESULTS: Intraoperative corneal disk completely detached: 6 eyes (0.5%); corneal disk incomplete sectioned: 3 eyes (0.2%); corneal epithelial disk: 2 eyes (0.2%); corneal interface minute foreign metal bodies: 11 eyes (0.9%); postoperative steroid intraocular hypertension: 21 eyes (1.7%); macular hemorrhage: 2 eyes (0.2%). At postoperative 3 months, there was refractive regression > 1.00 D in 0.0%, 3.1% and 7.9% respectively in the 3 groups; the increase in astigmatism > 1.00 D, 0.4%, 2.8% and 4.4% respectively. CONCLUSION: LASIK is a safe effective method for correcting myopia. Yet attention should be paid on the complications during and after operation. With the improvement in operative technique and better designed procedure, these complications can be decreased and the preoperative correctness in estimation of the postoperative results and the postoperative accuracy in the correction of myopia can be elevated.

Adolescent↗

PubMed1999

[The role of the leukocytes in pathogenesis of secondary brain injury].

The levels of leukocyte count, neutrophil number, leukocyte adhesiveness, leukocyte releasing oxygen-free radical (O2.-) after phagocytosing bacteria and serum lipid peroxide MDA were determined in the peripheral blood of 40 patients with acute head injury within 48 hours and 22 normal adults. These levels of patients were significantly higher than those of the controls (P < 0.05), and increased with the severity of craniocerebral injury elevation. The leukocyte count and neutrophil number of those patients who died were significantly higher than these of those survived patients (P < 0.05). It suggested that leukocytes aggravated the secondary brain injury after craniocerebral injury by increasing of leukocyte adhesiveness, and generating and releasing oxygen-free radical, and measurement of leukocyte count and neutrophil number in the peripheral blood could evaluate the prognosis of the patient with craniocerebral injury.

Adolescent↗

PubMed1999

[Determination of serum proteins by high performance capillary zone electrophoresis].

The separation method of serum proteins was established with an untreared 50 microns i.d. x 47 cm (40 cm to detector) capillary and detection of absorbance at 200 nm. Analysis was performed by pressure injectction 17.23 kPa.s and by applying 23 kV in the constant voltage mode. Serum samples were diluted 40-folds with assay buffer (12.5 mmol/L sodium borate, 1 mmol/L calcium lactate, 0.7 mmol/L magnesium sulfate, 1 mmol/L EDTA were mixed). A normal control serum protein was separated into 6 fractions. In pregnant serum, the alpha 0 was an additionally unknown fraction. Comparison of capillary electrophoresis with conventional cellulose acetate electrophoresis for analysis of serum proteins from normal control, pregnant women multiple myeloma and tonic rachitis patients indicates that capillary clectrophoresis is a new technique for the analysis of serum proteins because of its high efficiency, on-line data processing and automation. Capillary electrophoresis is the reliable technique for clinical diagnosis of serum protein abnormalities.

Albumins↗