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Biomedical subjects

H Zhao

Publications and source records attributed to H Zhao.

At least 55 records · Page 3Linked to original sources
PubMed2002

Luminescence isochron dating: a new approach using different grain sizes.

A new approach to isochron dating is described using different sizes of quartz and K-feldspar grains. The technique can be applied to sites with time-dependent external dose rates. It is assumed that any underestimation of the equivalent dose (De) using K-feldspar is by a factor F, which is independent of grain size (90-350 microm) for a given sample. Calibration of the beta source for different grain sizes is discussed, and then the sample ages are calculated using the differences between quartz and K-feldspar De from grains of similar size. Two aeolian sediment samples from north-eastern China are used to illustrate the application of the new method. It is confirmed that the observed values of De derived using K-feldspar underestimate the expected doses (based on the quartz De) but, nevertheless, these K-feldspar De values correlate linearly with the calculated internal dose rate contribution, supporting the assumption that the underestimation factor F is independent of grain size. The isochron ages are also compared with the results obtained using quartz De and the measured external dose rates.

Alpha Particles↗
PubMed2001

The betam protein, a member of the X,K-ATPase beta-subunits family, is located intracellularly in pig skeletal muscle.

The sequence of the pig cDNA encoding the muscle-specific betam-protein, a member of the X,K-ATPase beta-subunits family, was determined. Two alternatively spliced transcripts encoding polypeptide chains of 355 and 351 residues were identified. The tissue specificity of expression of betam and other X,K-ATPase beta-subunit genes was studied by RT-PCR performed on 24 tissues from newborn pigs. The betam expression was shown to be highly tissue-specific, being detected at the highest level in skeletal muscle, at a lower level in heart, and at much lower level in skin. The betam transcripts are more abundant in the tissues from the newborn than adult. Immunoblotting and deglycosylation shift assay indicated that skeletal muscle membranes of newborn pigs contain betam protein with an electrophoretic mobility and carbohydrate content very similar to that of human betam. Fractionation of membranes from both newborn and adult pig skeletal muscles by isopycnic centrifugation revealed that the majority of the betam protein is concentrated in the sarcoplasmic reticulum-containing fractions. This intracellular location is a unique property that distinguishes the betam protein from other members of the X,K-ATPase beta-subunit family.

Adenosine Triphosphatases↗
PubMed2001

Impaired c-Jun amino terminal kinase activity and T cell differentiation in death receptor 6-deficient mice.

During an immune response naive T helper (Th) cells differentiate into two functionally distinct subsets, Th1 and Th2, based on their cytokine secretion profile and immunomodulatory function. c-Jun amino terminal kinase (JNK) regulates Th cell differentiation by activating a transcriptional program required for cytokine production. We have recently identified a TNFR superfamily death domain-containing molecule, death receptor (DR)6, which potently activates JNK. T cells from DR6-deficient mice are substantially impaired in JNK activation. When DR6(-/-) mice were challenged with protein antigen, their T cells hyperproliferate and display a profound polarization toward a Th2 response whereas Th1 differentiation is not equivalently affected. In addition, DR6(-/)- T cells showed preference toward Th2 differentiation in vitro. The phenotype seen in the DR6(-/)- mice is not due to the apoptotic pathway. Therefore, DR6, working through JNK, rather than apoptosis, functions to attenuate the Th2 response. This is the first demonstration of a role in the activation and differentiation of Th cells by DR6 in particular and DRs in general.

Amino Acid Sequence↗
PubMed2001

Multipoint genetic mapping with trisomy data.

Trisomy is the most common genetic abnormality in humans and is the leading cause of mental retardation. Although molecular studies that use a large number of highly polymorphic markers have been undertaken to understand the recombination patterns for chromosome abnormalities, there is a lack of multilocus approaches to incorporating crossover interference in the analysis of human trisomy data. In the present article, we develop two statistical methods that simultaneously use all genetic information in trisomy data. The first approach relies on a general relationship between multilocus trisomy probabilities and multilocus ordered-tetrad probabilities. Under the assumption that no more than one chiasma exists in each marker interval, we describe how to use the expectation-maximization algorithm to examine the probability distribution of the recombination events underlying meioses that lead to trisomy. One limitation of the first approach is that the amount of computation increases exponentially with the number of markers. The second approach models the crossover process as a chi(2) model. We describe how to use hidden Markov models to evaluate multilocus trisomy probabilities. Our methods are applicable when both parents are available or when only the nondisjoining parent is available. For both methods, genetic distances among a set of markers can be estimated and the pattern of overall chiasma distribution can be inspected for differences in recombination between meioses exhibiting trisomy and normal meioses. We illustrate the proposed approaches through their application to a set of trisomy 21 data.

Algorithms↗
PubMed2001

Gamma-radiation-induced G2 delay, apoptosis, and p53 response as potential susceptibility markers for lung cancer.

Gamma-radiation results in cell cycle arrest and apoptosis in a wide variety of cells. Cell cycle arrest provides time for the cell to repair damaged DNA before entering the next phase of the cycle. If the damage is severe and cannot be repaired, the cells undergo apoptosis. However, if the damaged cells continue to grow without repair or apoptosis, then carcinogenic transformation may occur. We hypothesized that individuals with inherited disruption in cell cycle control and/or apoptosis and/or DNA repair may be susceptible to lung cancer development. The cells from susceptible individuals would have a shorter G2 period and less apoptosis compared with cells from normal individuals upon exposure to gamma-radiation. To test this hypothesis, the following methods were used: (a) fluorescence-activated cell sorting method was used to measure apoptosis and G2 cell cycle delay; (b) the ELISA method was used to measure p53 protein expression levels in these cell lines; and (c) gamma-radiation-induced chromatid breaks were counted as a marker for DNA damage or repair. Next, gamma-radiation-induced G2 delay and apoptosis were tested in three lymphoblastoid cell lines to determine the dose response effect and optimal time points of gamma-radiation. Finally, these assays were tested in lymphoblastoid cell lines from 30 lung cancer patients and 22 healthy controls. We found a dose-response relationship for gamma-radiation-induced G2 delay and apoptosis. The optimal time points to detect differential G2 delay and apoptotic index were 10 h and 48 h after gamma-radiation, respectively. The mean G2 delay was 22.5% +/- 10.5% for the control cell lines and 14.71% +/- 8.8% for case cell lines (P < 0.01). The mean apoptotic index was 20.4% +/- 11.7% for the controls and 14.3% +/- 7.8% for the cases (P < 0.05). The controls had a significantly higher p53 response ratio and fewer chromatid breaks than the cases. We also found that a p53 increasing ratio was strongly related to cell cycle G2 delay (gamma = 0.413; P = 0.002) and chromatid breaks (gamma =0.384; P = 0.028). Therefore, we concluded that gamma-radiation-induced G2 delay, apoptosis, p53 increasing ratio, and chromatid breaks might potentially be used as susceptibility markers for lung cancer risk. A large epidemiology study is in progress to confirm these findings.

Adult↗
PubMed2001

Elevated substance P levels in HIV-infected men.

The neuropeptide, substance P, is a potent modulator of neuroimmunoregulation. Substance P and its receptor modulate HIV infection. HIV-seropositive men had significantly higher plasma substance P levels compared with uninfected controls, which were associated with decreased CD16 and CD56 natural killer (NK) cell populations. The changes in plasma substance P levels and decreases in NK subsets did not correlate with CD4 cell levels, but a diurnal pattern was suggested for substance P. The balance between substance P expression and functions of immune cells may be important in the immunopathogenesis of HIV infection.

Cohort Studies↗
PubMed2001

Ectopic expression of a Chlamydomonas mt+-specific homeodomain protein in mt- gametes initiates zygote development without gamete fusion.

The molecular mechanisms that activate expression of zygote genes after fertilization are obscure. In animals, receptor-ligand interactions during sperm-egg membrane fusion as well as delivery of putative regulatory molecules by the sperm into the egg cytoplasm are proposed to activate zygote development and subsequent transcription of zygote genes. The mechanisms of activation of zygote development in higher plants also are mysterious, in part because of the difficulty of isolating female gametes of higher plants. In the unicellular, biflagellated green alga Chlamydomonas, the early steps in zygote development are much more accessible to investigation. Within minutes after mating type plus (mt+) and mating type minus (mt-) gametes fuse, expression of several zygote-specific transcripts is induced independently of protein synthesis. Here, we show that ectopic expression in mt- gametes of an mt+ gamete-specific, homeodomain protein, GSP1, induces a zygote-like phenotype and activates expression of zygote genes. One of the genes, zsp2, expressed in these "haploid zygotes" encodes a zygote cell surface adhesion molecule that promotes formation of multicellular aggregates. In total, expression of six out of seven zygote genes examined was induced by ectopic expression of GSP1. Our experiments show that in addition to contributing their genomes to the zygote cytoplasm, gametes also deliver proteins that can activate gene transcription.

Animals↗
PubMed2001

The human decatenation checkpoint.

Chromatid catenation is actively monitored in human cells, with progression from G(2) to mitosis being inhibited when chromatids are insufficiently decatenated. Mitotic delay was quantified in normal and checkpoint-deficient human cells during treatment with ICRF-193, a topoisomerase II catalytic inhibitor that prevents chromatid decatenation without producing topoisomerase-associated DNA strand breaks. Ataxia telangiectasia (A-T) cells, defective in DNA damage checkpoints, showed normal mitotic delay when treated with ICRF-193. The mitotic delay in response to ICRF-193 was ablated in human fibroblasts expressing an ataxia telangiectasia mutated- and rad3-related (ATR) kinase-inactive ATR allele (ATR(ki)). BRCA1-mutant HCC1937 cells also displayed a defect in ICRF-193-induced mitotic delay, which was corrected by expression of wild-type BRCA1. Phosphorylations of hCds1 or Chk1 and inhibition of Cdk1 kinase activity, which are elements of checkpoints associated with DNA damage or replication, did not occur during ICRF-193-induced mitotic delay. Over-expression of cyclin B1 containing a dominant nuclear localization signal, and inhibition of Crm1-mediated nuclear export, reversed ICRF-193-induced mitotic delay. In combination, these results imply that ATR and BRCA1 enforce the decatenation G(2) checkpoint, which may act to exclude cyclin B1/Cdk1 complexes from the nucleus. Moreover, induction of ATR(ki) produced a 10-fold increase in chromosomal aberrations, further emphasizing the vital role for ATR in genetic stability.

Ataxia Telangiectasia↗
PubMed2001

Doxorubicin-induced apoptosis is associated with increased transcription of endothelial nitric-oxide synthase. Effect of antiapoptotic antioxidants and calcium.

The clinical efficacy of the antitumor antibiotic drug doxorubicin (DOX) is severely limited by its dose-limiting cardiotoxicity in cancer patients. DOX-induced generation of reactive oxygen species was proposed to be a major mechanism of its cardiotoxicity. Previously, we showed that DOX undergoes a reductive activation at the reductase domain of endothelial nitric-oxide synthase (eNOS) forming the semiquinone and superoxide (Vásquez-Vivar, J., Martasek, P., Hogg, N., Masters, B. S. S., Pritchard, K. A., Jr., and Kalyanaraman, B. (1997) Biochemistry 36, 11293-11297). In this report, we provide evidence for DOX-induced increase in eNOS transcription and protein expression in bovine aortic endothelial cells (BAEC). We propose that DOX-induced hydrogen peroxide formation is responsible for the increased transcription of eNOS. BAEC treated with antisense eNOS oligonucleotide inhibits DOX-induced endothelial apoptosis. Treatment with antioxidants restored the levels of antiapoptotic proteins (Hsp70 and Bcl-2) in DOX-treated BAEC. DOX-induced intracellular oxidative stress, as measured by oxidation of dichlorodihydrofluorescein diacetate to dichlorofluorescein and hydroethidium to ethidium, was inhibited by antisense eNOS oligonucleotide and antioxidant treatment. Furthermore, antiapoptotic antioxidants (e.g. FeTBAP, ebselen, and alpha-phenyl-tert-butyl nitrone) inhibited DOX-induced eNOS transcription. We conclude that DOX-induced apoptosis is linked to the redox activation of DOX by eNOS.

Animals↗
PubMed2001

Search for the decay upsilon(1S) --> gammaeta(').

We report on a search for the radiative decay Upsilon(1S)-->gammaeta(') in 61.3 pb(-1) of data taken with the CLEO II detector at the Cornell Electron Storage Ring. Three decay chains were investigated, all involving eta(')-->pi(+)pi(-)eta, followed by eta-->gammagamma, eta-->pi(0)pi(0)pi(0), or eta-->pi(+)pi(-)pi(0). We find no candidate events in any of the three cases and set a combined upper limit of 1.6x10(-5) at 90% C.L., significantly smaller than the previous limit. We compare our result to other radiative Upsilon decays, to radiative J/psi decays, and to theoretical predictions.

Journal Article↗
PubMed2001

Genomic-scale measurement of mRNA turnover and the mechanisms of action of the anti-cancer drug flavopiridol.

BACKGROUND: Flavopiridol, a flavonoid currently in cancer clinical trials, inhibits cyclin-dependent kinases (CDKs) by competitively blocking their ATP-binding pocket. However, the mechanism of action of flavopiridol as an anti-cancer agent has not been fully elucidated. RESULTS: Using DNA microarrays, we found that flavopiridol inhibited gene expression broadly, in contrast to two other CDK inhibitors, roscovitine and 9-nitropaullone. The gene expression profile of flavopiridol closely resembled the profiles of two transcription inhibitors, actinomycin D and 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DRB), suggesting that flavopiridol inhibits transcription globally. We were therefore able to use flavopiridol to measure mRNA turnover rates comprehensively and we found that different functional classes of genes had distinct distributions of mRNA turnover rates. In particular, genes encoding apoptosis regulators frequently had very short half-lives, as did several genes encoding key cell-cycle regulators. Strikingly, genes that were transcriptionally inducible were disproportionately represented in the class of genes with rapid mRNA turnover. CONCLUSIONS: The present genomic-scale measurement of mRNA turnover uncovered a regulatory logic that links gene function with mRNA half-life. The observation that transcriptionally inducible genes often have short mRNA half-lives demonstrates that cells have a coordinated strategy to rapidly modulate the mRNA levels of these genes. In addition, the present results suggest that flavopiridol may be more effective against types of cancer that are highly dependent on genes with unstable mRNAs.

Antineoplastic Agents↗
PubMed2001

The docking of kinesins, KIF5B and KIF5C, to Ran-binding protein 2 (RanBP2) is mediated via a novel RanBP2 domain.

The Ran-binding protein 2 (RanBP2) is a vertebrate mosaic protein composed of four interspersed RanGTPase binding domains (RBDs), a variable and species-specific zinc finger cluster domain, leucine-rich, cyclophilin, and cyclophilin-like (CLD) domains. Functional mapping of RanBP2 showed that the domains, zinc finger and CLD, between RBD1 and RBD2, and RBD3 and RBD4, respectively, associate specifically with the nuclear export receptor, CRM1/exportin-1, and components of the 19 S regulatory particle of the 26 S proteasome. Now, we report the mapping of a novel RanBP2 domain located between RBD2 and RBD3, which is also conserved in the partially duplicated isoform RanBP2L1. Yet, this domain leads to the neuronal association of only RanBP2 with two kinesin microtubule-based motor proteins, KIF5B and KIF5C. These kinesins associate directly in vitro and in vivo with RanBP2. Moreover, the kinesin light chain and RanGTPase are part of this RanBP2 macroassembly complex. These data provide evidence of a specific docking site in RanBP2 for KIF5B and KIF5C. A model emerges whereby RanBP2 acts as a selective signal integrator of nuclear and cytoplasmic trafficking pathways in neurons.

Animals↗
PubMed2001

Involvement of the MAP kinase pathways in induction of GADD45 following UV radiation.

The p53-regulated stress-inducible gene GADD45 has been shown to participate in cellular response to DNA damage, including cell cycle checkpoint, apoptosis, and DNA repair. However, the regulation of GADD45 expression is complex and may involve both p53-dependent and -independent pathways. Recent findings have demonstrated that the p53-independent induction of GADD45 is mainly regulated by the transcription factors Oct-1 and NF-YA, which directly bind to their consensus motifs located at the GADD45 promoter region. Here, we report that mitogen-activated protein (MAP) kinases are involved in the induction of the GADD45 promoter after DNA damage. Inhibition of JNK1 and ERK kinase activities either by expression of the dominant negative mutant JNK1 or by treatment with a selective chemical inhibitor of ERK (PD098059) substantially abrogates the UV induction of the GADD45 promoter. In contrast, a p38 kinase inhibitor (SB203580) has little effect on GADD45 induction by UV. In addition, the GADD45 promoter is strongly activated following expression of JNK1; Raf-1, which is an upstream activator of the ERK pathway; or MEK1, an upstream activator of both the ERK and the JNK pathways. Activation of the GADD45 promoter by MAP kinases does not require normal p53 function. Interestingly, the MAP kinase-regulatory effect appears to be mediated via OCT-1 and CAAT motifs since disruption of these sites abrogates activation of the GADD45 promoter by MAP kinases. Therefore, these findings indicate that the MAP kinase pathways are involved in the regulation of the p53-independent induction of the GADD45 promoter, probably via interaction with transcription factors that directly bind to OCT-1 and CAAT motifs.

Amino Acid Motifs↗
PubMed2001

Synthesis and biochemical applications of a solid cyclic nitrone spin trap: a relatively superior trap for detecting superoxide anions and glutathiyl radicals.

A novel cyclic nitrone spin trap, 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide (BMPO) as a pure white solid has been synthesized for the first time. BMPO offers several advantages over the existing spin traps in the detection and characterization of thiyl radicals, hydroxyl radicals, and superoxide anions in biological systems. The corresponding BMPO adducts exhibit distinct and characteristic electron spin resonance (ESR) spectral patterns. Unlike the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-derived superoxide adduct, the BMPO superoxide adduct does not non-enzymatically decompose to the BMPO hydroxyl adduct. This feature is clearly perceived as a definite advantage of BMPO in its biological applications. In addition, the ESR spectrum of the BMPO glutathionyl adduct (BMPO/*SG) does not fully overlap with the spectrum of its hydroxyl adduct. This spectral feature is again distinctly different from that of DMPO because the ESR spectral lines of DMPO glutathionyl and hydroxyl radical adducts largely overlap. Finally, the ESR spectra of BMPO-derived adducts exhibit a much higher signal-to-noise ratio in biological systems. These favorable chemical and spectroscopic features make BMPO ideal for the detection of superoxide anions, hydroxyl and thiyl radicals in biochemical oxidation and reduction.

Cyclic N-Oxides↗
PubMed2001

Utilization of a peptide lead for the discovery of a novel PTP1B-binding motif.

Examination of the PTP1B inhibitory potency of an extensive series of phosphotyrosyl (pTyr) mimetics (Xxx) expressed in the EGFr-derived hexapeptide platform Ac-Asp-Ala-Asp-Xxx-Leu-amide previously led to the finding of high inhibitory potency when Xxx = 4-(phosphonodifluoromethyl)phenylalanyl (F2Pmp) (K(i) = 0.2 microM) and when Xxx = 3-carboxy-4-carboxymethyloxyphenylalanyl (K(i) = 3.6 microM). In the first instance, further work led from the F2Pmp-containing peptide to monomeric inhibitor, 6-(phosphonodifluoromethyl)-2-naphthoic acid (K(i) = 22 microM), and to the pseudo-dipeptide mimetic, N-[6-(phosphonodifluoromethyl)-2-naphthoyl]-glutamic acid (K(i) = 12 microM). In the current study, a similar approach was applied to the 3-carboxy-4-carboxymethyloxyphenylalanyl-containing peptide, which led to the preparation of monomeric 5-carboxy-6-carboxymethyloxy-2-naphthoic acid (K(i) = 900 microM). However, contrary to expectations based on the aforementioned F2Pmp work, incorporation of this putative pTyr mimetic into the pseudo-dipeptide, N-[5-carboxy-6-carboxymethyloxy-2-naphthoyl]-glutamic acid, resulted in a substantial loss of binding affinity. A reevaluation of binding orientation for 5-carboxy-6-carboxymethyloxy-2-naphthoic acid was therefore undertaken, which indicated a 180 degrees reversal of the binding orientation within the PTP1B catalytic site. In the new orientation, the naphthyl 2-carboxyl group, and not the o-carboxy carboxymethyloxy groups, mimics a phosphoryl group. Indeed, when 5-carboxy-2-naphthoic acid itself was examined at neutral pH for inhibitory potency, it was found to have K(i) = 31 +/- 7 microM, which is lower than parent 5-carboxy-6-carboxymethyloxy-2-naphthoic acid. In this fashion, 5-carboxy-2-naphthoic acid (or more appropriately, 6-carboxy-1-naphthoic acid) has been identified as a novel PTP1B binding motif.

Catalytic Domain↗
PubMed2001

Clinical markers of early disease in persons near onset of Huntington's disease.

OBJECTIVE: There is increasing evidence that neuron loss precedes the phenotypic expression of Huntington's disease (HD). As genes for late-onset neurodegenerative diseases are identified, the need for accurate assessment of phenoconversion (i.e., the transition from health to the disease phenotype) will be important. METHODS: Prospective longitudinal evaluation using the Unified Huntington's Disease Rating Scale (UHDRS) was conducted by Huntington Study Group members from 36 sites. There were 260 persons considered "at risk" for HD who initially did not have manifest disease and had at least one subsequent evaluation. Repeat UHDRS data, obtained an average of 2 years later, showed that 70 persons were given a diagnosis of definite HD based on the quantified neurologic examination. RESULTS: Baseline cognitive performances were consistently worse for the at-risk group who demonstrated conversion to a definitive diagnosis compared with those who did not. Longitudinal change scores showed that the at-risk group who did not demonstrate manifest disease during the follow-up study period demonstrated improvements in all cognitive tests, whereas performances in the at-risk group demonstrating conversion to disease during the study declined across cognitive domains. CONCLUSIONS: Neuropsychological measures show impairment 2 years before the development of more manifest motor disease. Findings suggest that these brief cognitive measures administered over time may capture early striatal neural loss in HD.

Adult↗
PubMed2001

Downregulation of small GTPase Rab7 impairs osteoclast polarization and bone resorption.

During skeletal growth and remodeling the mineralized bone matrix is resorbed by osteoclasts through the constant secretion of protons and proteases to the bone surface. This relies on the formation of specialized plasma membrane domains, the sealing zone and the ruffled border, and vectorial transportation of intracellular vesicles in bone-resorbing osteoclasts. Here we show that Rab7, a small GTPase that is associated with late endosomes, is highly expressed and is predominantly localized at the ruffled border in bone-resorbing osteoclasts. The decreased expression of Rab7 in cultured osteoclasts by antisense oligodeoxynucleotides disrupted the polarization of the osteoclasts and the targeting of vesicles to the ruffled border. These impairments caused a significant inhibition of bone resorption in vitro. The results indicate that the late endocytotic pathway is involved in the osteoclast polarization and bone resorption and underscore the importance of Rab7 in osteoclast function.

Actins↗