PubMed Health⌕ Search

Biomedical subjects

Hao Li

Publications and source records attributed to Hao Li.

At least 37 records · Page 2Linked to original sources
PubMed2006

Evolution of alternative transcriptional circuits with identical logic.

Evolution of gene regulation is an important contributor to the variety of life. Here, we analyse the evolution of a combinatorial transcriptional circuit composed of sequence-specific DNA-binding proteins that are conserved among all eukaryotes. This circuit regulates mating in the ascomycete yeast lineage. We first identify a group of mating genes that was transcriptionally regulated by an activator in a fungal ancestor, but is now transcriptionally regulated by a repressor in modern bakers' yeast. Despite this change in regulatory mechanism, the logical output of the overall circuit remains the same. By examining the regulation of mating in modern yeasts that are related to different extents, we deduce specific, sequential changes in both cis- and trans-regulatory elements that constitute the transition from positive to negative regulation. These changes indicate specific mechanisms by which fitness barriers were traversed during the transition.

Amino Acid Sequence↗
PubMed2006

Potential target genes of EMX2 include Odz/Ten-M and other gene families with implications for cortical patterning.

EMX2 and PAX6 are expressed by cortical progenitors and specify area patterning. We used representational difference analysis (RDA) to compare expressed RNAs from wild type and Emx2-/- cortex and identified 41 unique clones. Using secondary screening by in situ hybridization, we selected five genes for further analysis, Cdk4, Cofilin1, Crmp1, ME2, and Odz4, involved in neuronal proliferation, differentiation, migration, and axon guidance. Each exhibits differential expression in wild type cortex. Odz4 is one of four members of a vertebrate gene family homologous to the Drosophila pair-rule patterning gene, Odd Oz (Odz), a transmembrane receptor. We show that Odz genes are expressed in complementary patterns in cortex, as well as in nuclei-specific patterns in thalamus that relates to their area-unique cortical expression. In addition, each of the genes analyzed shows different expression patterns in wild type cortex, Emx2, and Pax6 mutant cortex, consistent with potential roles in area patterning. These findings identify potential targets of EMX2 that might account for its function and the defects in Emx2-/- cortex, and suggest that the Odz family of transmembrane proteins influences cortical area patterning downstream to EMX2 and PAX6.

Animals↗
PubMed2006

Conjugated indole-imidazole derivatives displaying cytotoxicity against multidrug resistant cancer cell lines.

We report herein the SAR studies of a series of indole-imidazole compounds. that demonstrate substantial in vitro anti-proliferative activities against cancer cell lines, including multidrug resistance (MDR) phenotypes. The in vitro cytotoxic effects have been demonstrated across a wide array of tumor types, including hematologic and solid tumor cell lines of various origins (e.g., leukemia, breast, colon, and uterine).

Antineoplastic Agents↗
PubMed2006

Simple, sensitive and rapid LC-MS method for the quantitation of indapamide in human plasma--application to pharmacokinetic studies.

A sensitive and specific method using liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) has been developed and validated for the identification and quantification of indapamide in human plasma. A simple liquid-liquid extraction procedure was followed by injection of the extracts on to a C18 column with gradient elution and detection using a single quadrupole mass spectrometer in selected ion monitoring (SIM) mode. The method was tested using six different plasma batches. Linearity was established for the concentration range 0.5-100.0 ng/ml, with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (RSD%) was lower than 10%, and accuracy ranged from 85 to 115%. The lower limit of quantification was reproducible at 0.2 ng/ml with 0.2 ml plasma. The proposed method enables the unambiguous identification and quantification of indapamide for pre-clinical and clinical studies.

Antihypertensive Agents↗
PubMed2006

A recyclable fluorous (S)-pyrrolidine sulfonamide promoted direct, highly enantioselective Michael addition of ketones and aldehydes to nitroolefins in water.

[reaction: see text] A recycle and reusable fluorous (S)-pyrrolidine sulfonamide organocatalyst has been developed for promoting highly enantio- and diastereoselective Michael addition reactions of ketones and aldehydes with nitroolefins in water. The organocatalyst is conveniently recovered from the reaction mixtures by fluorous solid-phase extraction and can be subsequently reused (up to six cycles) without a significant loss of catalytic activity and stereoselectivity.

Aldehydes↗
PubMed2006

Enantio- and diastereoselective Michael addition reactions of unmodified aldehydes and ketones with nitroolefins catalyzed by a pyrrolidine sulfonamide.

Chiral (S)-pyrrolidine trifluoromethanesulfonamide has been shown to serve as an effective catalyst for direct Michael addition reactions of aldehydes and ketones with nitroolefins. A wide range of aldehydes and ketones as Michael donors and nitroolefins as acceptors participate in the process, which proceeds with high levels of enantioselectivity (up to 99 % ee) and diastereoselectivity (up to 50:1 d.r.). The methodology has been employed successfully in an efficient synthesis of the potent H(3) agonist Sch 50917. In addition, a practical three-step procedure for the preparation of (S)-pyrrolidine trifluoromethanesulfonamide has been developed. The high levels of stereochemical control attending Michael addition reactions catalyzed by this pyrrolidine sulfonamide, have been investigated by using ab initio and density functional methods. Transition state structures for the rate-limiting C--C bond-forming step, corresponding to re- and si-face addition to the reactive conformation of the key enamine intermediates have been calculated. Analysis of these structures indicates that hydrogen bonding plays an important role in catalysis and that the energy barrier for si-face attack in reactions of aldehydes to form 2R,3S products is lower than that for the re-face attack leading to 2S,3R products. In contrast, the energy barrier for re-face addition is lower than that for si-face addition in reactions of ketones. The computational results, which are in good agreement with the experimental observations, are discussed in the context of the stereochemical course of these Michael addition reactions.

Journal Article↗
PubMed2006

Identification of gene expression patterns using planned linear contrasts.

BACKGROUND: In gene networks, the timing of significant changes in the expression level of each gene may be the most critical information in time course expression profiles. With the same timing of the initial change, genes which share similar patterns of expression for any number of sampling intervals from the beginning should be considered co-expressed at certain level(s) in the gene networks. In addition, multiple testing problems are complicated in experiments with multi-level treatments when thousands of genes are involved. RESULTS: To address these issues, we first performed an ANOVA F test to identify significantly regulated genes. The Benjamini and Hochberg (BH) procedure of controlling false discovery rate (FDR) at 5% was applied to the P values of the F test. We then categorized the genes with a significant F test into 4 classes based on the timing of their initial responses by sequentially testing a complete set of orthogonal contrasts, the reverse Helmert series. For genes within each class, specific sequences of contrasts were performed to characterize their general 'fluctuation' shapes of expression along the subsequent sampling time points. To be consistent with the BH procedure, each contrast was examined using a stepwise Studentized Maximum Modulus test to control the gene based maximum family-wise error rate (MFWER) at the level of alphanew determined by the BH procedure. We demonstrated our method on the analysis of microarray data from murine olfactory sensory epithelia at five different time points after target ablation. CONCLUSION: In this manuscript, we used planned linear contrasts to analyze time-course microarray experiments. This analysis allowed us to characterize gene expression patterns based on the temporal order in the data, the timing of a gene's initial response, and the general shapes of gene expression patterns along the subsequent sampling time points. Our method is particularly suitable for analysis of microarray experiments in which it is often difficult to take sufficiently frequent measurements and/or the sampling intervals are non-uniform.

Algorithms↗
PubMed2006

Highly designable phenotypes and mutational buffers emerge from a systematic mapping between network topology and dynamic output.

Deciphering the design principles for regulatory networks is fundamental to an understanding of biological systems. We have explored the mapping from the space of network topologies to the space of dynamical phenotypes for small networks. Using exhaustive enumeration of a simple model of three- and four-node networks, we demonstrate that certain dynamical phenotypes can be generated by an atypically broad spectrum of network topologies. Such dynamical outputs are highly designable, much like certain protein structures can be designed by an unusually broad spectrum of sequences. The network topologies that encode a highly designable dynamical phenotype possess two classes of connections: a fully conserved core of dedicated connections that encodes the stable dynamical phenotype and a partially conserved set of variable connections that controls the transient dynamical flow. By comparing the topologies and dynamics of the three- and four-node network ensembles, we observe a large number of instances of the phenomenon of "mutational buffering," whereby addition of a fourth node suppresses phenotypic variation amongst a set of three-node networks.

Biophysical Phenomena↗
PubMed2006

Functional roles of p12, the fourth subunit of human DNA polymerase delta.

Mammalian DNA polymerase delta (pol delta), a key enzyme of chromosomal DNA replication, consists of four subunits as follows: the catalytic subunit; p125, which is tightly associated with the p50 subunit; p68, a proliferating cell nuclear antigen (PCNA)-binding protein; and a fourth subunit, p12. In this study, the functional roles of the p12 subunit of pol delta were studied. The inter-subunit interactions of the p12 subunit were determined by yeast two-hybrid assays and by pulldown assays. These assays revealed that p12 interacts with p125 as well as p50. This dual interaction of p12 suggests that it may serve to stabilize the p125-p50 interaction. p12 was shown to be a novel PCNA-binding protein. This was confirmed by identification of a PCNA-binding motif at its N terminus by binding assays and by site-directed mutagenesis. The activities and reaction products of recombinant pol delta containing a p12 mutant defective in PCNA binding, as well as purified recombinant pol delta and its subassemblies, were analyzed. Our results indicate that p12 contributes to PCNA-dependent pol delta activity, i.e. the p12-PCNA interaction is functional. Our data indicate that both p12 and p68 are required for optimal pol delta activity. This supports the hypothesis that the interaction between pol delta and PCNA is a divalent one that involves p12 and p68. We propose a model in which pol delta interacts with PCNA via at least two of its subunits, and one in which p12 could play a role in stabilizing the overall pol delta-PCNA complex as well as pol delta itself.

Binding Sites↗
PubMed2006

Direct interaction of p21 with p50, the small subunit of human DNA polymerase delta.

Using a yeast two-hybrid screening technique and the p50 subunit of human DNA polymerase delta (pol delta) as a bait, p21 was found to interact with the p50 subunit of pol delta. A direct interaction between p21 and p50 was confirmed by using ELISA and pull-down assays with purified proteins. The interaction sites between p50 and p21 were mapped by pull down assays with GST deletion mutants. Residues 127-193 constitute the primary interaction region on p50 to which p21 binds, while p50 binds to the C-terminal 26 residues of p21. A histone kinase activity was associated with the highly purified calf thymus pol delta and addition of purified recombinant p21 inhibited the kinase activity in a dose dependent manner. p50 is phosphorylated in vivo and can be phosphorylated by CDK2/cyclinA in vitro. In vivo evidence of p21 association with p50 was obtained by coimmunoprecipitation using MCF7 cells. It was also shown that the association of p21 with p50 and other components of the pol delta complex increased in MCF7 cells treated with adriamycin. Our results suggested that p50 might target or anchor p21 to pol delta complex upon certain DNA damage such as adriamycin treatment.

Cyclin-Dependent Kinase 2↗
PubMed2006

[Relationship between myocyte proliferation and cardiac function in adult rats with heart failure].

OBJECTIVE: To confirm whether there is myocytes proliferation in the adult rat with heart failure or not, and to investigate the relationship between myocyte proliferation and heart function. METHODS: Descending anterior branch of left coronary artery was ligated in 20 adult male SD rats so as to establish an heart failure models. Eight rats were used as controls. Hemodynamic parameters, blood pressure (BP), left ventricle end systolic pressure (LVESP), left ventricle end diastolic pressure (LVEDP), +LVdp/dt(max), and -LVdp/dt(max), were measured 30 days after the coronary occlusion. Based on the results of heart function examination, the heart infarct rats were divided into 2 subgroups: cardiac functional compensation subgroup (8 rats), and cardiac functional decompensation subgroup (6 rats). Then the rats were killed and their hearts were taken out and stained with propidium iodide (PI) and antibody to alpha-sarcomeric actin. Immunohistochemistry was used to detect the proliferation cell nuclear antigen (PCNA). Confocal microscopy was used to observe the mitotic image. Light microscopy was used to observe the PCNA positive rate in the myocardium. RESULTS: (1) Mitotic images of myocytes could be identified by confocal microscopy in the left ventricle of all rats. (2) PCNA expression was detected in the nuclei of both infarct and normal hearts. The PCNA positive rate of the cardiac functional compensation subgroup was 7.2% +/- 1.4%, significantly higher than that of the control group (2.2% +/- 0.8%, P = 0.648). However, the PCNA positive rate of the cardiac functional decompensation subgroup was 3.0% +/- 1.3%, not significantly different from that of the control group (P = 0.648). (3) The correlation coefficient between PCNA-positivity of cardiomyocytes and +LVdp/dt(max) in the infarct rats were 0.80 (P < 0.01) and the correlation coefficient between PCNA-positivity of cardiomyocytes and -LVdp/dt(max) was -0.76 (P = 0.01). CONCLUSION: (1) There is myocyte proliferation in the adult rat heart. (2) Myocyte proliferation is positively correlated with heart systolic function, and negatively correlated with heart diastolic function in chronic heart failure.

Actins↗
PubMed2006

Liquid chromatographic/mass spectrometry assay of triptolide in dog plasma and its application to pharmacokinetic study.

A rapid and sensitive method for the determination of triptolide in dog plasma was developed and validated, using high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI/MS). Sample preparation consisted of liquid-liquid extraction with ethyl acetate from dog plasma. The analytes and internal standard prednisolone were well separated on a Zorbax Extend-C18 analytical column. Detection was performed on a triple quadrupole mass spectrometer using selected-ion monitoring (SIM) mode on the deprotonated ions [M-H]- at m/z 359. Calibration curves were linear over the concentration range of 0.5-200 ng/mL of triptolide with the intra- and inter-day precision (the relative standard deviation values) were being less than 7%. Triptolide was stable under different conditions. The intra-day and inter-day accuracy were 99.3-105.2% and 101.3-107.0%, respectively. The lower limit of quantification was 0.5 ng/mL. The method was successfully applied to a pharmacokinetic study after an intragastric administration (i.g.) of triptolide to dogs with a dose of 0.05 mg/kg. The results confirm that the assay is suitable for the pharmacokinetic study of triptolide.

Animals↗
PubMed2006

Intramedullary spinal tuberculoma: report of three cases.

BACKGROUND: Intramedullary spinal tuberculoma is a rare form of central nervous system tuberculosis. This article describes the successful management of intramedullary spinal tuberculoma in 3 patients who received treatment between 2000 and 2003. CASE DESCRIPTION: The character of 3 cases was analyzed retrospectively, including clinical manifestation and magnetic resonance imaging findings. All masses were excised totally under microscope. Histopathologic examination revealed tuberculoma. Postoperatively, all patients received a 6 to 9 month course of ATT. The outcome was favorable. CONCLUSIONS: The intramedullary spinal tuberculoma must be considered in the differential diagnosis of the spinal cord compression in patients with a history of tuberculosis. When confronted with a progressing neurologic deficit and poor response to ATT, surgical intervention should be considered. The optimal treatment is a combination of microsurgical resection and ATT.

Adult↗
PubMed2006

[Major constituent proteins in donkey hide and their interaction].

OBJECTIVE: To analyze the constituent proteins in donkey hide, the key ingredient for Ejiao, an important traditional Chinese medicine for the blood-related conditions, in hope to eventually decipher the biochemical mechanism behind Ejiao's prominent medicinal efficacy. METHOD: Two methods were employed to extract proteins in donkey skin. One used TriPure isolation reagent to extract the total proteins in donkey skin. Another used 1% sodium dodecyl sulfate (SDS) to heat the sample at 100 degrees C overnight. And then sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and capillary HPLC were used to analyze the component of proteins. RESULT: There are not only collagen alpha1 (I) and collagen alpha2 (I), but also serum albumin in donkey skin. The content is over 25% in total proteins with the method of TriPure isolation reagent. The content of donkey serum albumin is up to 20% with the method of 1% SDS heating. And two bands, molecular weight are nearly 200 kDa,were found on 7.5% SDS-PAGE. Extracted these proteins to analyze with capillary HPLC, they were found to be the complex products of collagen and serum albumin of donkey. CONCLUSION: Donkey serum albumin is a main protein component in the hide, which is a clue to expose is the effect of Ejiao on blood.

Animals↗
PubMed2006

[In vitro preservation of laryngeal allograft for larynx transplantation].

BACKGROUND & OBJECTIVE: As a complex organ, laryngeal allograft cannot endure more than 3 hours during preservative time in vitro. This study was to explore the best preservation method and time limit of laryngeal allograft. METHODS: During transplantation experiment of the larynx, HCA solution and UW's solution was used to perfuse laryngeal allograft on original position separately. The sequential morphologic changes of the allograft after cold preservation were observed to compare the effects of the 2 solutions. RESULTS: After preservation in HCA solution for 20 h, ultrastructure changes, including mitochondrial edema or collapse and chromatin agglutination, appeared in mucosa, capillary and intrinsic laryngeal muscle cells of the laryngeal allograft; nuclear pyknosis was observed after 22 h and followed by apoptosis. While ischemic and necrosis changes of the laryngeal allograft appeared after preservation in UW's solution for 24 h. CONCLUSIONS: UW's solution can preserve laryngeal allograft for 24 h in vitro, and has better effect than HCA solution.

Adenosine↗
PubMed2006

[Pathological character and treatment of epithelial-myoepithelial carcinoma of salivary gland].

OBJECTIVE: To review and evaluate pathologic features and treatment of epithelial-myoepithelial. METHODS: Retrospectively reviewed 14 cases' pathological and clinical materials of epithelial-myoepithelial carcinoma of salivary gland. Eight cases origine from parotid gland, 2 cases from hard palate, 3 cases from submandibular gland and 1 case from nasal cavity. Three cases were performed induction chemotherapy preoperation. One case had palliative radiotherapy. Thirteen cases were performed radical surgery and 6 cases had radiotherapy postoperation. RESULTS: Tumor arisen mostly from parotid gland and neck lymph node metastasis rate was 14.28% (2/14). The survival rate was calculated with Kaplan-Meier method. The overall 3-, 5- and 10-year survival rate were 67.20%, 45.49% and 17.06%. Its histological characteristics were inner layer composed by adenoid cells and outer layer composed by myoepithelial cells. Immunohistochemical exam show cytokeratin, S-100 and actin reaction positive. CONCLUSIONS: Epithelial-myoepithelial carcinoma easily develops recurrence. It is sensitivity to radiotherapy and chemotherapy to some extent. It is suitable to adopt surgical treatment as primary modality combined with other therapies.

Adult↗