Biomedical subjects

S Zhao

Publications and source records attributed to S Zhao.

At least 145 records · Page 8Linked to original sources

PubMed2000

Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products.

Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mrel1. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.

Ataxia Telangiectasia↗

PubMed2000

Neuronal basic helix-loop-helix proteins (NEX and BETA2/Neuro D) regulate terminal granule cell differentiation in the hippocampus.

The transcription factors neuronal helix-loop-helix protein (NEX)/mammalian atonal homolog 2 (Math-2), BETA2/neuronal determination factor (NeuroD), and NeuroD-related factor (NDRF)/NeuroD2 comprise a family of Drosophila atonal-related basic helix-loop-helix (bHLH) proteins with highly overlapping expression in the developing forebrain. The ability of BETA2/NeuroD and NDRF to convert ectodermal cells into neurons after mRNA injection into Xenopus oocytes suggested a role in specifying neuronal cell fate. However, neuronal bHLH genes are largely transcribed in CNS neurons, which are fully committed. Here we analyze a defect in mice lacking BETA2/NeuroD, and in NEX*BETA2/NeuroD double mutants, demonstrating that bHLH proteins are required in vivo for terminal neuronal differentiation. Most strikingly, presumptive granule cells of the dentate gyrus are generated but fail to mature, lack normal sodium currents, and show little dendritic arborization. Long-term hippocampal slice cultures demonstrate secondary alterations of entorhinal and commissural/associational projections. The primary developmental arrest appears to be restricted to granule cells in which an autoregulatory system involving all three neuronal bHLH genes has failed.

Action Potentials↗

PubMed2000

Cell-surface exposure of phosphatidylserine correlates with the stage of fludarabine-induced apoptosis in chronic lymphocytic leukemia and expression of apoptosis-regulating genes.

BACKGROUND: Programmed cell death (PCD) is characterized by a sequence of tightly regulated events that result in the activation of caspases and in internucleosomal DNA cleavage. Late apoptotic events such as DNA-strand breaks can be assayed by in situ end labeling (ISEL) and DNA measurement (sub G1) using flow cytometry. Phosphatidylserine (PS) redistribution from the inner plasma membrane leaflet to the outer leaflet, an early event in PCD, can be detected by annexin V (AxV) binding to PS. AxV-fluorescein isothiocyanate (FITC) fluorescence intensity is variable and characterizes different cell populations, denoted here as AxV-negative (AxV(neg)), AxV-low-positive (AxV(lo)), and AxV-high-positive (AxV(hi)). METHODS: We investigate the correlation of three methods (ISEL, sub G1 DNA content, and AxV assay) for detecting apoptosis with focus on differences between populations with different levels of PS. We also examined the expression of PCD-regulating Bcl-2 family members in these cell populations by reverse transcription-polymerase chain reaction (RT-PCR). Chronic lymphocytic leukemia (CLL) cells exposed to fludarabine (FAMP) were used as an in vitro model. Cells with different PS/AxV levels were separated using fluorescence-activated cell sorting (FACS). RESULTS: Only purified AxV(hi) cells had high positivity in the ISEL and sub G1 assays (94 +/- 0.6%, 88.6 +/- 6.6%, and 98.6 +/- 0.6%, respectively), indicating that late apoptotic cells are detected equally by all three methods. In the AxV(lo) population, ISEL was positive in 21% +/- 13% and DNA sub G1 in 20% +/- 6.6% of cells, suggesting that AxV identifies early apoptotic cells better than the other assays. Anti-apoptotic Bcl-2 and Bcl-X(L) were upregulated by FAMP when cells entered apoptosis (AxV(lo)), as was pro-apo- ptotic Bcl-X(S), which was undetectable in nonapoptotic AxV(neg) cells. Pro-apoptotic Bax was only expressed in AxV(neg) and AxV(lo) cells. Late apoptotic AxV(hi) cells did not express Bcl-X(S) or Bax. RESULTS: (1) AxV staining is more sensitive than sub G1 or ISEL in detecting early apoptotic cells; (2) only late apoptotic cells are equally detected by all assays; (3) AxV is a valuable tool in the detection and isolation of apoptotic cells at different stages of PCD; and (4) pro-apoptotic Bcl-X(S) and Bax are expressed at early, not late, stages of apoptosis.

Annexin A5↗

PubMed2000

Cloning, characterization and mapping of the human ATP5E gene, identification of pseudogene ATP5EP1, and definition of the ATP5E motif.

A cDNA encoding the epsilon subunit of human ATP synthase, ATP5E, was isolated from heart, skeletal muscle and spleen cDNA libraries respectively. Its genome structure was characterized as comprising three exons and two introns within a stretch of 5 kb, according to the genomic sequence AL109840. The gene was mapped to human chromosome 20q13.3 between marker D20S173 and 20qter using the radiation hybrid GB4 panel. Northern blot analysis showed that the ATP5E gene was expressed as a single 0.6 kb transcript in all 16 human tissues tested, with a high level present in heart and skeletal muscle. A new conserved motif composed of 24 residues, termed the ATP5E motif [W(R/K)X(5)YX(2)(Y/F)X(3)(C/A)X(4)RX(3)K], was defined on the basis of sequences of ATP synthase epsilon subunits from ten different organisms. In addition, a pseudogene ATP5EP1 was also identified on the basis of genomic sequence AC004066, localized on human chromosome 4q25. By analysing these results combined with the Southern blot patterns of human DNA hybridized with bovine ATP5E cDNA reported previously [Vinas, Powell, Runswick, Iacobazzi and Walker (1990) Biochem. J. 265, 321-326], we provide evidence of yet further homologous sequences (either gene or pseudogene) of ATP5E, in addition to ATP5E and ATP5EP1 in the human genome.

Amino Acid Sequence↗

PubMed2000

The influence of ATP on the binding of aromatic amino acids to the ligand response domain of the tyrosine repressor of Haemophilus influenzae.

The binding of aromatic amino acids to the ligand response domain of the tyrosine repressor (TyrR) protein (TyrR(lrd)) of Haemophilus influenzae was investigated using circular dichroism and fluorescence spectroscopy. The induced secondary structural changes were unique for each aromatic amino acid and were further influenced by the presence or absence of ATP. Tyrosine was found to have the highest affinity for TyrR(lrd) in the absence of ATP, whereas the affinity for ATP itself increased in the presence of tyrosine. Binding of tyrosine is therefore the conformational trigger for the activation of TyrR whereas ATP is regarded as a conformational co-activator.

Adenosine Triphosphate↗

PubMed2000

Human BAC ends quality assessment and sequence analyses.

End sequences from bacterial artificial chromosomes (BACs) provide highly specific sequence markers in large-scale sequencing projects. To date, we have generated >300,000 end sequences from >186,000 human BAC clones with an average read length of >460 bp for a total of 141 Mb covering approximately 4.7% of the genome. Over 60% of the clones have BAC end sequences (BESs) from both ends representing more than fivefold coverage of the human genome by the paired-end clones. Our quality assessments and sequence analyses indicate that BESs from human BAC libraries developed at The California Institute of Technology (CalTech) and Roswell Park Cancer Institute have similar properties. The analyses have highlighted differences in insert size for different segments of the CalTech library. Problems with the fidelity of tracking of sequence data back to physical clones have been observed in some subsets of the overall BES dataset. The annotation results of BESs for the contents of available genomic sequences, sequence tagged sites, expressed sequence tags, protein encoding regions, and repeats indicate that this resource will be valuable in many areas of genome research.

Chromosome Mapping↗

PubMed2000

Characterization, chromosomal assignment, and tissue expression of a novel human gene belonging to the ARF GAP family.

We have identified and characterized a novel human ADP-ribosylation factor GTPase-activating protein (ARFGAP1) gene that is related to other members of the ARF GAP family. The full-length cDNA for human ARFGAP1 was cloned following the identification of an EST obtained by large-scale cDNA library sequencing through a Blast search of public databases. Structurally, ARFGAP1 encodes a polypeptide of 516 amino acids, which contained a typical GATA-1-type zinc finger motif (CXXCX(16)CXXC) with the four cysteine residues that are highly conserved among other members of the ARF GAP family. The conserved ARF GAP domain may emphasize the biological importance of this gene. The ARFGAP1 gene, which contained 16 exons ranging from 0.5 to 9.3 kb, was mapped to human chromosome 22q13.2-q13.3 using radiation hybridization and in silico analyses. ARFGAP1 is strongly expressed in endocrine glands and testis. Interestingly, the expression of ARFGAP1 in testis is about sixfold higher than that in ovary, indicating a possible role of ARFGAP1 in the physiological function of sperm. Expression of ARFGAP1 in four human fetal tissues and seven cancer cell lines was also detected.

ADP-Ribosylation Factors↗

PubMed2000

Congenital absence of permanent teeth in a six-generation Chinese kindred.

We report on rare, heritable, permanent tooth agenesis in a large Chinese kindred. The congenital absence of permanent teeth except the first and second accessory teeth was observed in 52 individuals through six successive generations in the kindred comprising 328 members. Clinical assessments were carried out, and inheritance mode and spousal influence of the anomaly on their offspring were analyzed. Consequently, the anomaly was transmitted in an autosomal dominant fashion with incomplete penetrance (P = 0.88), and no significant clinical manifestations other than the oligodontia were found. A geographical or environmental effect on the affected individuals was obviously eliminated, because any who are related to the kindred but live under the same conditions are fully healthy. The disorder we describe, therefore, differs from any previously reported oligodontia/anodontia syndromes. The oligodontia ranged from a few teeth to the whole set of teeth, and usually occurred at a period from age 7 or 8 years, the time when primary teeth are normally replaced by permanent teeth, to the forties. Roentgenography of the affected persons indicated that only the first and/or second accessory teeth with tooth buds developed as permanent teeth. In fact, the diphyodontic germination sometimes occurred in the oral cavity of the affected individuals.

China↗

PubMed2000

Composite Au/TiO(2) Nanoparticles: Synthesis, Characterization, and Assembly by Using Potentiostatic Technique.

Composite Au/TiO(2) nanoparticles were synthesized using TiO(2) nanoparticles as nuclei. The particles were characterized by UV-vis spectroscopy, zeta potential, EDS, and TEM. The mean diameter of the particles is about 23.6 nm, and the position of the surface plasma absorption band peak is at 533 nm, with a red shift of 15 nm compared with that of Au sol. The zeta potential is +31.3 mV. Monolayers of composite Au/TiO(2) nanoparticles were obtained using the potentiostatic technique. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Human BAC ends.

The Human BAC Ends database includes all non-redundant human BAC end sequences (BESs) generated by The Institute for Genomic Research (TIGR), the University of Washington (UW) and California Institute of Technology (CalTech). It incorporates the available BAC mapping data from different genome centers and the annotation results of each end sequence for the contents of repeats, ESTs and STS markers. For each BAC end the database integrates the sequence, the phred quality scores, the map and the annotation, and provides links to sites of the library information, the reports of GenBank, dbGSS and GDB, and other relevant data. The database is freely accessible via the web and supports sequence or clone searches and anonymous FTP. The relevant sites and resources are described at http://www.tigr.org/ tdb/humgen/bac_end_search/bac_end_intro.html

Chromosome Mapping↗

PubMed2000

Model for avulsion injury in the rat brachial plexus using passive acceleration.

We have developed an experimental model for brachial plexus injuries in the rat that closely simulates the characteristics of human injury. This model produces avulsion injuries in a noninvasive manner. A prototype apparatus was designed that allowed a force to be transmitted to a restrained limb by passive acceleration. Reproducible results were obtained in 32 rats. A significant correlation was found between the test weight and the number of roots avulsed (r = 0.92; P < 0.05). The amount of force also correlated to the pattern of avulsion injury: a 230-g weight produced either C6 (54%), C7 (15%), or C6 and C7 (31%) avulsions; a 330-g weight produced C6 (18%), C7 (9%), or C6 and C7 (73%) avulsions; a 530-g weight produced C5 through C8 (75%) or C6 through T1 (25%) avulsions. This model of brachial plexus injury may be useful to further our understanding of the cellular response to this incapacitating injury and to develop therapeutic strategies with behavioral correlates.

Acceleration↗

PubMed2000

Characterization of chicken antisera raised against Aspergillus spp. by enzyme linked immunosorbent assay.

Enzyme linked immunosorbent assays of three Aspergillus species have been developed. Laying hens were immunized with the exoantigens from Asp. flavus, Asp. ochreaus and Asp. versicolor. All test chickens except for one produced antisera raised against the exoantigens. The antisera production process and ELISA titer were analysed. Fourteen days after the first injection, the antisera began to produce largely, on the 35th day reached to the peak, and maintained a stable level until the 42nd day. The maximum ELISA titer of the antisera to the exoantigens from Asp. flavus, Asp. ochreaus and Asp. versicolor was 1:8,000, 1:10,000 and 1:10,000, respectively. The cross-reactivities of antisera were determined with seventeen species of Aspergillus, ten species of fungi from other genera and the buffer-extracts of grain. The antisera did not cross-react with the exoantigens from other genera and the buffer-extracts of grain. The antiserum to exoantigen from Asp. ochreaus was species-specific, whereas the antisera against Asp. flavus and Asp. versicolor tended to cross-react with other Aspergillus species to varying degrees. The results suggest that exoantigens immunoassays can be developed to indentify and detect Aspergillus genus in grains.

Animals↗

PubMed2000

Preference for nonsteroidal antiinflammatory drugs over acetaminophen by rheumatic disease patients: a survey of 1,799 patients with osteoarthritis, rheumatoid arthritis, and fibromyalgia.

OBJECTIVE: Because there is controversy regarding the efficacy of acetaminophen in rheumatic diseases and because apparently safer nonsteroidal antiinflammatory drugs (NSAIDs) are being produced, we surveyed rheumatic disease patients about their preferences for these agents to determine the degree to which one type of therapeutic agent is preferred over the other. METHODS: In 1998, we surveyed by mailed questionnaire 1,799 patients with osteoarthritis (OA), rheumatoid arthritis, or fibromyalgia who were participating in a long-term outcome study. Patients who had taken acetaminophen rated the effectiveness of acetaminophen, compared its effectiveness with that of NSAIDs, and then rated their overall satisfaction with acetaminophen compared with NSAIDs when both effectiveness and side effects were considered. RESULTS: Two-thirds of study participants had taken acetaminophen. About 37% of patients who had taken acetaminophen found it to be moderately or very effective and about 63% indicated that it was not effective or was only slightly effective. One-fourth of the patients found acetaminophen and NSAIDs to be equally effective, but >60% found acetaminophen to be much less effective or somewhat less effective. About 12% preferred acetaminophen to NSAIDs. When both effectiveness and side effects were considered together, 25% of the patients had no preference, 60% preferred NSAIDs, and 14% preferred acetaminophen. CONCLUSION: There was a considerable and statistically significant preference for NSAIDs compared with acetaminophen among the 3 groups of rheumatic disease patients. Although this preference decreased slightly with age and was less pronounced in OA patients, the preference was noted among all categories of patients and was not altered by disease severity. If safety and cost are not issues, there would hardly ever be a reason to recommend acetaminophen over NSAIDs, since patients generally preferred NSAIDs and fewer than 14% preferred acetaminophen. If safety and costs are issues, then the recommendation of the American College Rheumatology that acetaminophen be tried first seems correct, since 38.2% found acetaminophen to be as effective or more effective than NSAIDs.

Acetaminophen↗

PubMed2000

Deuterium nuclear spin-lattice relaxation times and quadrupolar coupling constants in isotopically labeled saccharides.

(13)C and (2)H spin-lattice relaxation times have been determined by inversion recovery in a range of site-specific (13)C- and (2)H-labeled saccharides under identical solution conditions, and the data were used to calculate deuterium nuclear quadrupolar coupling constants ((2)H NQCC) at specific sites within cyclic and acyclic forms in solution. (13)C T(1) values ranged from approximately 0.6 to 8.2 s, and (2)H T(1) values ranged from approximately 79 to 450 ms, depending on molecular structure (0.4 M sugar in 5 mM EDTA (disodium salt) in (2)H(2)O-depleted H(2)O, pH 4. 8, 30 degrees C). In addition to providing new information on (13)C and (2)H relaxation behavior of saccharides in solution, the resulting (2)H1 NQCC values reveal a dependency on anomeric configuration within aldopyranose rings, whereas (2)H NQCC values at other ring sites appear less sensitive to configuration at C1. In contrast, (2)H NQCC values at both anomeric and nonanomeric sites within aldofuranose rings appear to be influenced by anomeric configuration. These experimental observations were confirmed by density functional theory (DFT) calculations of (2)H NQCC values in model aldopyranosyl and aldofuranosyl rings.

Deuterium↗

PubMed2000

Assessment of a new quantitative ultrasound calcaneus measurement: precision and discrimination of hip fractures in elderly women compared with dual X-ray absorptiometry.

The incidence of osteoporotic hip fracture increases in postmenopausal women with low hip bone mineral density (BMD). Dual X-ray absorptiometry (DXA) is the most commonly used technique for the assessment of bone status and provides good measurement precision. However, DXA affords little information about bone architecture. Quantitative ultrasound (QUS) systems have been developed to evaluate bone status for assessment of fracture risk. Our study was designed to assess a new QUS system from Hologic, the Sahara; to compare it with a previous model, the Walker-Sonix UBA 575+; and to investigate whether it is able to discriminate between women with and without fracture. Using both ultrasound devices, the measurements were performed at the heels of 33 postmenopausal women who had recently sustained hip fracture. A control group of 35 age-matched postmenopausal women was recruited for comparison. The total, neck and trochanter femoral BMD values were assessed using DXA for both groups. QUS and DXA measurements were significantly lower in fractured patients (p < 0.005) than in the control group. The short-term, mid-term and standardized short-term precisions were used to evaluate the reproducibility of the two QUS systems. The Sahara showed a better standardized coefficient of variation for broadband ultrasound attenuation (BUA) than did the UBA 575+ (p < 0.001). The correlation of BUA and speed of sound (SOS) between the two QUS devices was highly significant, with an r value of 0.92 for BUA and 0.91 for SOS. However, the correlation between DXA and ultrasound parameters ranged from 0.28 to 0.44. We found that ultrasound measurements at the heel were significant discriminators of hip fractures with odds ratios (OR) ranging from 2.7 to 3.2. Even after adjusting the logistic regressions for total, neck or trochanter femoral BMD, QUS variables were still significant independent discriminators of hip fracture. The areas under the ROC curves of each ultrasound parameter ranged from 0.75 to 0.78, and compared very well with femoral neck BMD (p > 0.05). In conclusion, our study indicated that the calcaneal QUS variables, as measured by the Sahara system can discriminate hip fracture patients equally as well as hip DXA.

Absorptiometry, Photon↗

PubMed2000

The impact of overall treatment time on outcomes in radiation therapy for non-small cell lung cancer.

PURPOSE: A retrospective study was carried out to evaluate the impact of overall treatment time (OTT) on the results of radiation therapy for non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: From Jan. 1990 to Dec. 1996, 256 patients with stages I-IIIb NSCLC entered this analysis. All patients received definitive radiotherapy. Biologically effective dose (BED) was used to standardize the irradiation effects. The correlation between OTT and local progression-free survival was analyzed by linear-regression and Cox proportional hazard models. The prognostic variables for survival and distant metastasis were also briefly studied. RESULTS: OTT had been shortened in 64 patients because of an accelerated hyperfractioned irradiation, while OTT was prolonged i n 114 patients due to interruptions of irradiation courses. The main ca uses of interruption were machine breakdown or delayed preparations of c errobend block for boost fields (55%), holidays (11%) and treatment toxi city and side effects (34%). Patients tre ated with prolonged OTT (> 45 days) had significant poorer local progression-free survival than whom with OTT of </=45 days, 1, 3 and 5 year actuarial local progression-free survivals being 49, 17 and 15% for the former, and 74, 35 and 25% for the latter, respectively (P<0.001). BED-T that contained the factor of OTT correlated directly to local controls, which implied that BED-T represented radiobiological effects accurately, in other words, OTT had played a role in determining the radiobiological effects. Linear-regression on 103 cases treated with BED of 80-85 Gy(10) showed that 3 year local progression-free survival decreased by 9% per week with prolongation of OTT, or vice versa it increased by 9% per week with shortening OTT in an OTT range of 30-76 days. Cox multivariate analyses confirmed that OTT was an independent prognostic factor for local controls. CONCLUSION: OTT may have played an important role in determining local controls in radiotherapy for NSCLC. One should always keep in mind to make the OTT as short as possible, provided the patients can tolerate it, and to reduce irradiation interruptions for whatever reasons to a minimum.

Adult↗

PubMed2000

Genomic typing of Escherichia coli O157:H7 by semi-automated fluorescent AFLP analysis.

Escherichia coli serotype O157:H7 isolates were analyzed using a relatively new DNA fingerprinting method, amplified fragment length polymorphism (AFLP). Total genomic DNA was digested with two restriction endonucleases (EcoRI and MseI), and compatible oligonucleotide adapters were ligated to the ends of the resulting DNA fragments. Subsets of fragments from the total pool of cleaved DNA were then amplified by the polymerase chain reaction (PCR) using selective primers that extended beyond the adapter and restriction site sequences. One of the primers from each set was labeled with a fluorescent dye, which enabled amplified fragments to be detected and sized automatically on an automated DNA sequencer. Three AFLP primer sets generated a total of thirty-seven unique genotypes among the 48 E. coli O157:H7 isolates tested. Prior fingerprinting analysis of large restriction fragments from these same isolates by pulsed-field gel electrophoresis (PFGE) resulted in only 21 unique DNA profiles. Also, AFLP fingerprinting was successful for one DNA sample that was not typable by PFGE, presumably because of template degradation. AFLP analysis, therefore, provided greater genetic resolution and was less sensitive to DNA quality than PFGE. Consequently, this DNA typing technology should be very useful for genetic subtyping of bacterial pathogens in epidemiologic studies.

Animals↗

PubMed2000

Cernuosides A and B, two sucrase inhibitors from Pulsatilla cernua.

Two oleanane-type oligoglycosides, cernuosides A (1) and B (2), were isolated from the roots of Pulsatilla cernua (Ranunculaceae). Structure elucidation was accomplished by 1D and 2D NMR (DQF-COSY, TOCSY, HMQC, HMBC, and ROESY) methods, FABMS, and hydrolysis. Both compounds showed moderate activity against sucrase.

Animals↗