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Hong Zhang

Publications and source records attributed to Hong Zhang.

At least 379 records · Page 21Linked to original sources
PubMed2003

Validation of a novel assay for checkpoint responses: characterization of camptothecin derivatives in Saccharomyces cerevisiae.

The evolutionary conservation of pathways preserving genetic stability supports the use of a lower eukaryote such as the yeast Saccharomyces cerevisiae in screening for novel anti-neoplastic agents. Yeast is already established as a model system to characterize the cellular effects of the topoisomerase inhibitor and anti-cancer agent camptothecin (CPT). Here, we demonstrate that a recently developed two-hybrid based plate assay that visualizes the DNA damage-induced homomeric complex formation of the yeast checkpoint protein Rad17 correctly predicts the biological activity of the tested camptothecin derivatives. The used criteria for biological activity include lethality, cell cycle arrest and Rad53p phosphorylation, an essential signaling event during checkpoint activation. Surprisingly, although responsive to camptothecin and not without influence on drug sensitivity, Rad17p appears to be dispensable for cell cycle arrest and for Rad53p phosphorylation following treatment with camptothecin. Such a role is only uncovered if double-strand break repair is compromised.

Antineoplastic Agents↗
PubMed2003

Driven kinks in the anharmonic Frenkel-Kontorova model.

Multiple and supersonic topological excitations (kinks) driven by an external dc force in the Frenkel-Kontorova model (a chain of atoms subjected to a periodic substrate potential) with the exponential interatomic interaction are studied with the help of numerical simulation. The simulation results are interpreted in terms of dynamics of two limiting cases, the exactly integrable sine-Gordon equation and the Toda chain. The stability of driven kinks and scenarios of their destruction are described for a wide range of model parameters.

Journal Article↗
PubMed2003

Rapid determination of 5-fluorouracil in plasma using capillary electrophoresis.

A rapid, simple and sensitive capillary electrophoresis (CE) method used for the determination of 5-fluorouracil in rabbit plasma is described in the present paper. In this method, samples were simply pretreated by a solvent extraction procedure prior to injection. With a running buffer composed of 30 mM Tris-H(3)PO(4) (pH 7.0) and 5% isopropanol, 5-fluorouracil was easily separated from the external standard alpha-phenethylol as well as other substances existed in the plasma. A linearity of 5-fluorouracil was determined in the range from 0.17 to 42.50 microg/ml with a correlation coefficient of 0.999. A limit of quantitation (LOQ) corresponding to signal-to-noise ratio of 10 was obtained (LOQ=0.08 microg/ml). The method was successfully used for determining the 5-fluorouracil in real plasma samples from rabbits.

Animals↗
PubMed2003

Incidence trends and familial risks in invasive and in situ cutaneous melanoma by sun-exposed body sites.

We studied incidence trends, age-incidence relationships and familial risks in invasive and in situ cutaneous melanoma, based on the Swedish Family-Cancer Database of more than 10 million individuals. Offspring were 0-66 years of age. Cancers were obtained from the Swedish Cancer Registry from years 1961-98. The study was based on 9,771 offspring and 22,888 parents with invasive melanoma and 2,446 offspring and 5,017 parents with in situ melanoma. Incidence rates increased markedly for invasive melanoma in the trunk. For in situ melanoma, trunk and head and neck were affected, and, in addition, legs for women. The maximal incidence was around age 80 years, independent of the type or site in men; in women early onset superficially spreading melanoma shifted the age for maximal incidence to about 60 years. For in situ melanoma, lentigo maligna was the main histogenetic type in the head and neck but in the trunk and legs superficially spreading melanoma was somewhat more common. Standardized incidence ratios (SIR) were calculated for familial risk at exposed and covered sites. The combined familial risks for invasive and in situ melanoma were higher at covered (SIR 3.56 from parents) than sun-exposed (1.92 from parents) sites and they agreed when familiality was defined between parents and offspring or between siblings; the sibling SIRs were 3.90 at covered and 2.53 at exposed sites. The data suggest that the higher melanoma density at exposed sites masks familial effects. Furthermore, sun exposure does not appear to reinforce the familial effect.

Adolescent↗
PubMed2003

[A 3-amino acid deletion of apolipoprotein E found in 3 Chinese lipoprotein glomerulopathy patients].

OBJECTIVE: To analyze the mutation of apolipoprotein E (apoE) gene so as to investigate the pathogenesis of lipoprotein glomerulopathy (LPG). METHODS: Restriction fragment length polymorphism methods was used to analyze the apoE genotypes of three Chinese patients with LPG and 3 of their relatives. Automated DNA sequencing was performed upon their apoE genes. RESULTS: A 9-bp deletion in exon 4 of apoE, resulting in a 3-amino acid deletion (residues 142-144-0) was identified. CONCLUSION: A 3-amino acid deletion of apoE has been discovered which is associated with LPG.

Adolescent↗
PubMed2003

Induction of ASABF (Ascaris suum antibacterial factor)-type antimicrobial peptides by bacterial injection: novel members of ASABF in the nematode Ascaris suum.

Recently, invertebrate models have been widely used for the study of innate immunity. Nematodes are novel potential candidates because of the experimental advantages of Caenorhabditis elegans. However, whether nematodes have active immune responses is still ambiguous. Previously, we reported ASABF (Ascaris suum antibacterial factor)-type antimicrobial peptides in the parasitic nematode Ascaris suum and the genetic model nematode C. elegans. Further screening of a cDNA library and an expressed-sequence-tag database search detected five novel members of ASABF (ASABF-beta, -gamma, -delta, - epsilon and -zeta) in A. suum. The transcripts for ASABF-alpha, -beta, -gamma, and -delta clearly increased in the body wall, and also in the intestine for ASABF-delta, 4 h after injection of heat-killed bacteria into the pseudocoelom (body cavity), suggesting that these peptides are inducible in the acute phase of immune response. These results also suggest that the nematodes can recognize bacteria in the pseudocoelomic fluid and evoke an active immune response.

Amino Acid Sequence↗
PubMed2003

AtCHIP, a U-box-containing E3 ubiquitin ligase, plays a critical role in temperature stress tolerance in Arabidopsis.

The Arabidopsis gene AtCHIP encodes a protein with three tetratricopeptide repeats and a U-box domain, which is structurally similar to the animal CHIP proteins, a new class of E3 ubiquitin ligases. Like animal CHIP proteins, AtCHIP has E3 ubiquitin ligase activity in vitro. AtCHIP is a single-copy gene, and its transcript is up-regulated by several stress conditions such as low and high temperatures. However, increased AtCHIP expression alone was not correlated with increased stress tolerance; in fact, overexpression of AtCHIP in Arabidopsis rendered plants more sensitive to both low- and high-temperature treatments. Higher electrolyte leakage was observed in leaves of AtCHIP overexpression plants after chilling temperature treatment, suggesting that membrane function is likely impaired in these plants under such a condition. These results indicate that AtCHIP plays an important role in plant cellular metabolism under temperature stress conditions.

Acclimatization↗
PubMed2003

[Collectrin, a kidney-specific novel gene, is over-expressed in the hypertrophic phase in 5/6 nephrectomized rat kidney].

OBJECTIVE: To investigate the expression of the novel gene, collectrin, in the remnant kidney of the 5/6 nephrectomized rat. METHODS: Thirty-four rats were randomly assigned to three groups: sham-operation group (CON, n = 10), 5/6 nephrectomy group (NX, n = 12), NX + enalapril group (ACEI, since one day before the 5/6 nephrectomy 10 mg x kg(-1) x d(-1) enalapril was administered). Two weeks, 8 weeks, and 15 weeks after the above-mentioned treatments, 1/3 of the rats in different group were killed and their kidneys were taken out. Immunohistochemical staining was used to detect the expression of collectrin. The collectrin mRNA expression in the kidneys was detected by RT-PCR, and collectrin protein expression was observed by Western blot assay. RESULTS: In the kidneys of the CON group rats, the expression of collectrin was progressively decreased over time (2 W vs 16 W, 1.69 +/- 0.09 vs 1.21 +/- 0.09, P < 0.05; 8 W vs 16 W, 1.38 +/- 0.04 vs 1.21 +/- 0.09, P < 0.05). However, collectrin was over-expressed in the remnant renal tissues compared with in the kidneys of control rats (NX vs CON, 2 W 2.33 +/- 0.07 vs 1.69 +/- 0.09, P < 0.05; 8 W 1.85 +/- 0.20 vs 1.38 +/- 0.04, P < 0.05; 16 W 1.47 +/- 0.17 vs 1.21 +/- 0.09, P < 0.05); In NX group, collectrin expression was obviously increased 2 weeks after the operation, then decreased along with the progression of renal failure (2 W vs 8 W, 2.33 +/- 0.07 vs 1.85 +/- 0.20, P < 0.05; 2W vs 16 W, 2.33 +/- 0.07 vs 1.47 +/- 0.17, P < 0.05; 8 W vs 16 W, 1.85 +/- 0.20 vs 1.47 +/- 0.17, P < 0.05). In ACEI treated group, collectrin expression was decreased along with the amelioration of renal lesions. The expression of collectrin mRNA was consistent with the expression of collectrin protein. CONCLUSION: The expression of collectrin is progressively decreased with aging in normal rat kidney. In 5/6 nephrectomized kidney the expression of collectrin is related with the renal proliferation and hypertrophy.

Animals↗
PubMed2003

Does microwaving enhance the Golgi methods? A quantitative analysis of disparate staining patterns in the cerebral cortex.

As a family of techniques, the Golgi methods have long been used for studying the morphology and structure of the central nervous system. Due to their capricious nature, many modifications have been employed to improve the reliability and quality of the technique, including the recent addition of microwave energy. In the present study, we evaluated the effectiveness of adding microwave energy to two Golgi methods: the Golgi-Cox method and the rapid Golgi method. These methods were selected for their widespread use in animal research and human postmortem studies. Control tissue was compared to tissue exposed to microwave energy for varying lengths of time during the chromating step of both methods. As assessed by stereological cell counts and qualitative observation, the addition of microwave energy improved the quality of the impregnations and the number of labeled profiles in both methods up to a specific limit of exposure. Surprisingly, increases in the number of profiles were often the result of increased non-neuronal staining at the expense of neuronal staining. This result appears to be due to the fact that different classes of labeled profiles displayed distinct staining time courses.

Animals↗
PubMed2003

Mouse Spam1 (PH-20) is a multifunctional protein: evidence for its expression in the female reproductive tract.

Sperm adhesion molecule 1 (Spam1) is a widely conserved sperm surface protein with multiple roles in mammalian fertilization. Although the gene for this protein has been thought to be testis specific based on Northern blot analysis, there is evidence for nontesticular expression when transcripts are analyzed by more sensitive techniques. In the present investigation, results of a reverse transcription polymerase chain reaction assay, an RNase-protection assay (RPA), and an in situ transcript hybridization assay revealed that the murine Spam1 gene is transcribed in the female genital tract. RPA revealed that Spam1 transcripts are synthesized in a region-dependent manner, with the oviduct having lower transcript levels than the uterus and vagina. The transcripts levels were 3- to 10-fold lower in the female genital tract than in the testis. In situ transcript hybridization assay revealed RNA in the luminal epithelium in all three regions of the genital tract and in the uterine myometrium and the oviductal mesothelium. Western blot analysis and immunohistochemistry demonstrated that the protein concentration is 1.5- to 3-fold lower in female tissues than in sperm, and localization is similar to that of the transcripts. The protein has hyaluronidase activity at neutral pH, which is unique for sperm hyaluronidase, but not at acidic pH. In the uterus, Spam1 expression fluctuated during the estrous cycle. Its localization suggests that in addition to functioning as a secretory protein, it may be involved in hyaluronic acid metabolism or turnover in the female genital tract. Our results provide further evidence that Spam1 is a multifunctional protein and that it is less restricted in its expression than previously reported.

Animals↗
PubMed2003

Structure of the YibK methyltransferase from Haemophilus influenzae (HI0766): a cofactor bound at a site formed by a knot.

The crystal structures of YibK from Haemophilus influenzae (HI0766) have been determined with and without bound cofactor product S-adenosylhomocysteine (AdoHcy) at 1.7 and 2.0 A resolution, respectively. The molecule adopts an alpha/beta fold, with a topology that differs from that of the classical methyltransferases. Most notably, HI0766 contains a striking knot that forms the binding crevice for the cofactor. The knot formation is correlated with an alternative arrangement of the secondary structure units compared with the classical methyltransferases. Two loop regions undergo conformational changes upon AdoHcy binding. In contrast to the extended conformation of the cofactor seen in the classical methyltransferase structures, AdoHcy binds to HI0766 in a bent conformation. HI0766 and its close sequence relatives are all shorter versions of the more remotely related rRNA/tRNA methyltransferases of the spoU sequence family. We propose that the spoU sequence family contains the same core domain for cofactor binding as HI0766 but has an additional domain for substrate binding. The substrate-binding domain is absent in HI0766 sequence family and may be provided by another Haemophilus influenzae partner protein, which is yet to be identified.

Amino Acid Sequence↗
PubMed2003

Senescence-specific gene expression fingerprints reveal cell-type-dependent physical clustering of up-regulated chromosomal loci.

Replicative senescence is the state of irreversible proliferative arrest that occurs as a concomitant of progressive telomere shortening. By using cDNA microarrays and the gabriel system of computer programs to apply domain-specific and procedural knowledge for data analysis, we investigated global changes in gene transcription occurring during replicative senescence in human fibroblasts and mammary epithelial cells (HMECs). Here we report the identification of transcriptional "fingerprints" unique to senescence, the finding that gene expression perturbations during senescence differ greatly in fibroblasts and HMECs, and the discovery that despite the disparate nature of the chromosomal loci affected by senescence in fibroblasts and HMECs, the up-regulated loci in both types of cells show physical clustering. This clustering, which contrasts with the random distribution of genes down-regulated during senescence or up-regulated during reversible proliferative arrest (i.e., quiescence), supports the view that replicative senescence is associated with alteration of chromatin structure.

Breast↗
PubMed2003

Structural characterization of a human cytosolic NMN/NaMN adenylyltransferase and implication in human NAD biosynthesis.

Pyridine dinucleotides (NAD and NADP) are ubiquitous cofactors involved in hundreds of redox reactions essential for the energy transduction and metabolism in all living cells. In addition, NAD also serves as a substrate for ADP-ribosylation of a number of nuclear proteins, for silent information regulator 2 (Sir2)-like histone deacetylase that is involved in gene silencing regulation, and for cyclic ADP ribose (cADPR)-dependent Ca(2+) signaling. Pyridine nucleotide adenylyltransferase (PNAT) is an indispensable central enzyme in the NAD biosynthesis pathways catalyzing the condensation of pyridine mononucleotide (NMN or NaMN) with the AMP moiety of ATP to form NAD (or NaAD). Here we report the identification and structural characterization of a novel human PNAT (hsPNAT-3) that is located in the cytoplasm and mitochondria. Its subcellular localization and tissue distribution are distinct from the previously identified human nuclear PNAT-1 and PNAT-2. Detailed structural analysis of PNAT-3 in its apo form and in complex with its substrate(s) or product revealed the catalytic mechanism of the enzyme. The characterization of the cytosolic human PNAT-3 provided compelling evidence that the final steps of NAD biosynthesis pathways may exist in mammalian cytoplasm and mitochondria, potentially contributing to their NAD/NADP pool.

Cell Line↗
PubMed2003

Analytical approach to the drift of the tips of spiral waves in the complex Ginzburg-Landau equation.

In this paper, we investigate the motion of spiral waves in the complex Ginzburg-Landau equation (CGLE) analytically and numerically. We find that the tip of the spiral wave drifts primarily in the direction of the electric field and there is a smaller component of the drift that is perpendicular to the field when a uniform field is applied to the system. The velocity of the tip is uniform and its component along the electric field is equal to the strength of the field. When the CGLE system is driven by white noise, a diffusion law for the vortex core of the spiral wave is derived at long time explicitly. The diffusion constant is found to be D=T/C(2), in which T is the noise strength and C is the core asymptotic factor of the spiral wave. When the external force is a simple oscillation we find that the tip of the spiral wave drifts if the frequency of the external force is the same as that of the system. Our analytical results are verified using numerical simulations.

Journal Article↗
PubMed2003

G-protein-coupled receptor signaling in Syk-deficient neutrophils and mast cells.

The Syk tyrosine kinase is essential for immunoreceptor and multiple integrin functions as well as being implicated in signaling from G-protein-coupled receptors (GPCR) in cell lines, transfection systems, and pharmacologic studies. In contrast, using Syk-deficient primary cells, we show here that Syk does not play a major functional role in chemoattractant/chemokine signaling in neutrophils and mast cells. syk(-/-) neutrophils showed normal respiratory burst and degranulation in response to the bacterial peptide formyl-Met-Leu-Phe (fMLP). The migration of neutrophils toward fMLP was similarly not affected by the syk(-/-) mutation. fMLP initiated normal Ca(2+)-signal, activation of the extracellular signal-related kinase (ERK) and p38 mitogen-activated protein (MAP) kinase cascades, and polymerization of cellular actin in the absence of Syk. syk(-/-) and wild-type neutrophils also responded similarly to LTB(4), C5a, and the chemokines macrophage inflammatory protein-1 (MIP-1)alpha or MIP-2, both in functional assays and in intracellular signaling mechanisms. Furthermore, bone marrow-derived syk(-/-) mast cells showed normal activation of the Akt, ERK, and p38 MAP kinase pathways when stimulated by the GPCR ligand adenosine. We conclude that, in contrast to previous reports, Syk does not play a major role in GPCR signaling.

Animals↗
PubMed2003

Checkpoint arrest signaling in response to UV damage is independent of nucleotide excision repair in Saccharomyces cerevisiae.

The recognition of DNA double-stranded breaks or single-stranded DNA gaps as a precondition for cell cycle checkpoint arrest has been well established. However, how bulky base damage such as UV-induced pyrimidine dimers elicits a checkpoint response has remained elusive. Nucleotide excision repair represents the main pathway for UV dimer removal that results in strand interruptions. However, we demonstrate here that Rad53p hyperphosphorylation, an early event of checkpoint signaling in Saccharomyces cerevisiae, is independent of nucleotide excision repair (NER), even if replication as a source of secondary DNA damage is excluded. Thus, our data hint at primary base damage or at UV damage (primary or secondary) that does not need to be processed by NER as the relevant substrate of damage-sensing checkpoint proteins.

Cell Cycle↗