Biomedical subjects

Heng Liu

Publications and source records attributed to Heng Liu.

10 recordsLinked to original sources

PubMed2006

Peripheral blood pressure changes induced by dobutamine do not alter BOLD signals in the human brain.

In extending the use of functional MRI to neuropharmacology, a primary area of concern is that peripheral blood pressure changes induced by pharmacological agents could independently produce a change in the blood oxygenation level-dependent (BOLD) signal, resulting in difficulties distinguishing or interpreting drug-induced neural activations. In the present study, we utilized intravenous dobutamine, a beta-adrenergic receptor agonist, to increase the mean arterial blood pressure (MABP), while examining the effects of MABP changes on the BOLD signal in cocaine-dependent participants. Dobutamine infusion significantly increased the MABP from 93 +/- 8 mm Hg to 106 +/- 12 mm Hg (P < 0.0005), but did not produce a significant global BOLD signal. Yet, a few voxels in the anterior cingulate showed BOLD signal changes that paralleled the changes in blood pressure (BP). Our observations support the conclusion that following the infusion of psychoactive agents, brain BOLD signals accurately reflect neuronal activity, even in the face of relatively large peripheral cardiovascular effects that transiently increase systemic BP.

Adrenergic beta-Agonists↗

PubMed2005

Perinatal nutritional iron deficiency permanently impairs hippocampus-dependent trace fear conditioning in rats.

Many studies show that iron deficient (ID) children are at risk for poor cognitive development. This suggests that learning and cognitive centers in the brain, such as the hippocampus, may be compromised by developmental ID. The present study used a heart rate trace fear conditioning procedure in rats to show that perinatal nutritional ID impairs hippocampus-dependent learning. This procedure requires rats to associate a conditioned stimulus and a fearful unconditioned stimulus, which are separated by a trace interval. Rats were started on ID or control (CN) diets 10 days prior to birth, and learning was assessed on post natal day (PND)-28. The ID pups were impaired in trace fear coniditioning, but an ID control group was not impaired in a non-trace basic fear conditioning procedure that does not depend on the hippocampus. Another group was switched from ID to CN diet on PND-31, and this group also showed impairments in trace fear conditioning when tested during early adulthood (i.e. PND-63). Separate control tests show that ID may produce skeletal motor deficits. The ID-induced learning impairments in this study, however, were not due to altered motor activity because learning was assessed using non-motor heart rate responses.

Animal Nutritional Physiological Phenomena↗

PubMed2005

[Effect of surface modification on surface energy of lactose and performance of dry powder inhalations].

AIM: To investigate the effects of surface modification of lactose carrier on performance of dry powder inhalations (DPIs). METHODS: Modified lactose surface was prepared using a "particle smoothing" process to obtain smooth carrier surface and low surface energy with the presence of magnesium stearate, colloidal silica dioxide and talc. Inverse gas chromatography (IGC) was used to assess the surface energy of treated lactose, and the in vitro deposition of carrier-based IFNa-2b DPIs was evaluated with twin stage impinger. RESULTS: The flowing property of lactose was greatly improved and the surface energy decreased by the "particle smoothing" process. Decreasing surface energy resulted in greater aspiration fraction of IFNa-2b. CONCLUSION: IGC is a potentially useful tool for rapid formulation design and screening.

Administration, Inhalation↗

PubMed2005

[Antineoplastic effect of valproic acid and trichostatin on HL-60 and K562 cells].

The objective of this study was to investigate antineoplastic effects of valproic acid (VPA) and trichostatin (TSA) on HL-60 and K562 cells in vitro, and the synergic effects of VPA or TSA in combination with ATRA. The inhibitory effects of VPA, TSA and ATRA in various concentrations and different combinations on proliferation of HL-60 and K562 cells were observed by cell growth curves, 50% inhibitory concentration (IC(50)), as well as inhibition of leukemia colony growth at different time points. The characteristics of cell differentiation or apoptosis were analyzed by cytochemical staining, differentiation antigen detection, cell cycle assay and A(NBT)/A(MMT) value determination. The results showed that HL-60 cell had a lower IC(50) of VPA and TSA compared with K562 cells. ATRA could significantly enhance the inhibition of VPA, TSA on clonegenicity of HL-60 cells and inhibition of VPA on clonegenicity of K562 cells. HL-60 cells treated with VPA displayed the phenotype of neutrophilic like cells, and showed the increases of NBT reduction rate and CD11b expression. No evidence for K562 differentiation was found. It is concluded that both VPA and TSA inhibit HL-60 cells growth in vitro. VPA induces differentiation of HL-60 cells to granulocyte. VPA and TSA have a moderate anti-proliferative effect on K562 cells. None of these agents induces K562 cell differentiation.

Antineoplastic Agents↗

PubMed2004

Retinoid X receptor alpha (RXRalpha) helix 12 plays an inhibitory role in the recruitment of the p160 co-activators by unliganded RXRalpha/retinoic acid receptor alpha heterodimers.

Retinoid X receptor (RXR)/retinoic acid receptor (RAR) heterodimers control gene expression through recruitment of co-repressors or co-activators, depending on their hormone binding status. We show that the helix 12 of RXRalpha and RARalpha is critical for recruitment of the co-regulators and transcriptional regulation by RXRalpha, RARalpha, and RXRalpha/RARalpha. LG268, an RXR-specific agonist, was able to promote co-activator association with the heterodimers, but was unable to dissociate co-repressors. Reconstitution experiments in yeast demonstrated that LG268 was capable of activating transcription by RXRalpha/RARalpha through recruitment of the co-activator. We hypothesize that the inability to release co-repressors from RXRalpha/RARalpha is responsible for the inability of LG268 to activate RXRalpha/RARalpha heterodimers in mammalian cells. Deletion of RARalpha helix 12 (RXRalpha/RARalpha Delta403) abolished both hormone-dependent dissociation from co-repressors and hormone-dependent association with co-activators. Deletion of RXRalpha helix 12 (RXRalpha Delta443/RARalpha) resulted in a higher binding affinity for co-repressors. Unexpectedly, RXRalpha Delta443/RARalpha also gained hormone-independent co-activator binding activity. Moreover, LG268 became an antagonist to RXRalpha Delta443/RARalpha heterodimers. These data suggest that the helix 12 of RXRalpha plays an inhibitory role in the recruitment of co-activators by unliganded RXRalpha/RARalpha.

Amino Acid Sequence↗

PubMed2004

Moiré interferogram phase extraction: a ridge detection algorithm for continuous wavelet transforms.

We present a procedure using continuous wavelet transforms (CWTs) to extract the phase information from moiré interferograms. The relationship between precise ridge detection of the two-dimensional CWT magnitude map and accurate phase extraction is detailed. A cost function is introduced for the adaptive selection of the ridge, and a computationally inexpensive implementation of the cost function ridge detection algorithm is explored with dynamic programming optimization. The results of the proposed ridge detection algorithm on actual interferograms are illustrated. Moreover, the resulting extracted phase is demonstrated to be smooth and accurate. As a result, the sensitivity of the moiré interferometry method is improved to obtain a pixel-by-pixel in-plane strain distribution map.

Journal Article↗

PubMed2004

[Cloning and expression of the endo-beta-glucanase III cDNA gene from Trichoderma viride AS3.3711].

To study the construction of yeast bioengineering strain which can degrade cellulosic waste, an endo-beta-glucanase III (EG III) cDNA gene of Trichoderma viride AS3.3711 was isolated with RT-PCR protocol. After sequencing it was constructed on S. cerevisiae induceable expression vector pYES2. A L9 (3(4)) orthogonal design was used to optimize yeast sonication assistant transformation. The expression of EG III gene was induced by 2% beta-D-glactose, the transcription and expression of it was detected by Northern blotting and Congo Red method respectively. The endo-beta-glucanase activity was assayed as CMCase activity with CMC-Na as a substrate. The results show that the ORF of EG III was 1254 bp, encoding 418 aa, deducing molecular weight 44.1 x 10(3), group 5 (sonication treat time 60 s, incubate 40 min, SS-DNA 150 microg, heat shock 5 min) was the optimum one of the orthogonal experiment, and EG III transformants can produced clear hydrolysis halos on the Congo-Red-CMC plate. The measure of the enzyme activity show that the expression product can be expressed in active forms and secreted to the medium. The enzyme activity was approached the highest level (0.041 U/mL) when the culture time was 60 h. The optimized enzyme reaction temperature was 50 degrees C and the optimized pH was 5.8.

Cloning, Molecular↗

PubMed2003

A fluorescent carbazole derivative: high sensitivity for quadruplex DNA.

We have synthesized a novel molecule, 3,6-bis(1-methyl-4-vinylpyridium)carbazole diiodide (BMVC), for recognizing specific quadruplex structures, particularly the quadruplex of human telomeric sequence d(T(2)AG(3))(4). The fluorescence intensity of the BMVC molecule increases from 1 to almost 2 orders of magnitude upon interacting with various DNAs. At a concentration of BMVC of 10 microM, fluorescence bands with different colors of BMVC in electrophoresis gels of various DNAs can be observed. The fluorescence of BMVC can be used to discriminate between duplex and quadruplex DNAs. At the low concentration of 0.1 microM BMVC in prestained gels, the fluorescence is observed in the presence of quadruplexes with anti-anti-anti-anti and anti-anti-syn-syn arrangements. However, no fluorescence band is detected upon interacting with duplexes and quadruplexes with anti-syn-anti-syn arrangement. Moreover, the sensitivity assays show that as little as 0.2 pmol of quadruplex of d(T(2)AG(3))(4) can be revealed by BMVC.

Absorption↗

PubMed2003

Molecular characterization of Trimeresurus stejnegeri venom L-amino acid oxidase with potential anti-HIV activity.

A novel L-amino acid oxidase, named TSV-LAO, has been purified and cloned from the snake Trimeresurus stejnegeri. Fifty percentage cytotoxic concentrations (CC50) of TSV-LAO on C8166 cells were 24 and 390 nM in the absence or presence of catalase (400 nM), respectively. However, at concentrations that showed little effect on cell viability, TSV-LAO displayed dose dependent inhibition on HIV-1 infection and replication. The antiviral selectivity indexes (CC50/EC50) were 16 and 6, respectively, corresponding to the measurements of syncytium formation and HIV-1 p24 antigen expression. Interestingly, the presence of catalase resulted in an increase of its antiviral selectivity to 52 and 38. Under the same conditions, no anti-HIV-1 activity was observed by exogenous addition of H2O2. The complete amino acid sequence of TSV-LAO, as deduced from its cDNA, exhibits a high degree of sequence identity with other snake venom LAOs.

Amino Acid Oxidoreductases↗

PubMedDate not supplied

Effect of erythromycin on contractile response of uterine smooth muscle strips in non-pregnant rats.

OBJECTIVE: Erythromycin stimulates stomach smooth muscle contraction via action on motilin receptors, but the effects of erythromycin on non-pregnant uterine smooth muscle are unknown. The purpose of this study was to assess the effect of erythromycin on non-pregnant uterine smooth muscle and to examine the possible mechanism of its action. STUDY DESIGN: Uterine smooth muscle strips from rats were suspended in organ baths containing Krebs solution, and then isometric tension was measured. The response to erythromycin and the effect of hexamethonium, indomethacin, phentolamine, diphenhydramine, atropine, metoclopramide and verapamil on erythromycin-induced contraction were also assessed. RESULTS: The present study showed for the first time that erythromycin dose-dependently increased contractile frequency, and at a dose of 1.55 x 10(-3) mol/l it also increased contractile tension in non-pregnant uterine smooth muscle strips in rats. These actions were not affected by pretreatment with hexamethonium, indomethacin, phentolamine, atropine and metoclopramide, but histamine H1 receptor blocker diphenhydramine and calcium channel blocker verapamil inhibited both responses induced by erythromycin. CONCLUSION: Our results suggest that erythromycin could increase contractile frequency and tension of non-pregnant uterine smooth muscle via histamine H1 receptor and calcium channel.

Animals↗