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Biomedical subjects

M Huang

Publications and source records attributed to M Huang.

At least 109 records · Page 6Linked to original sources
PubMed2000

Bond strength of plasma-sprayed hydroxyapatite/Ti composite coatings.

One of the most important clinical applications of hydroxyapatite (HA) is as a coating on metal implants, especially plasma-sprayed HA coating applied on Ti alloy substrate. However, the poor bonding strength between HA and Ti alloy has been of concern to orthopedists. In this paper, an attempt has been made to enhance the bonding strength of HA coating by forming a composite coating with Ti. The bioactivity of the coating has also been studied. HA/Ti composite coatings were prepared via atmospheric plasma spraying on Ti-6Al-4V alloy substrates. The bond strength evaluation of HA/Ti composite coatings was performed according to ASTM C-633 test method. X-ray diffractometer and scanning electron microscopy were applied to identify the phases and the morphologies of the coatings. The bioactivity of HA/Ti composite coating was qualified by immersion of coating in simulated body fluid (SBF). The obtained results revealed that the addition of Ti to HA improved the bonding strength of coating significantly. In the SBF test, the coating surface was covered by carbonate-apatite, which was testified by X-ray photoelectron spectroscope, indicating good bioactivity for HA/Ti composite coating. The bioactivity of the coating has not been reduced by the addition of Ti.

Alloys↗
PubMed2000

Interactions between Panax quinquefolium saponins and vitamin C are observed in vitro.

Inasmuch as the oxidation of low-density lipoprotein (Ox-LDL) may play a key role in the initiation and progression of atherosclerosis, it has become increasingly important to identify potential antioxidants. Panax quinquefolium saponins (PQS) are extracted from the stems and leaves of the North American form of ginseng, Panax quinquefolium. Our previous studies have indicated that PQS (0.25-1 mg/ml) can protect against oxidation of LDL in vitro. The purpose of the current work was to investigate the potential interaction of lower concentrations of PQS (1-100 microg/ml) with vitamin C on the reduction of LDL oxidation. LDL was isolated from the plasma of healthy human donors by sequential ultracentrifugation. Native LDL (0.05 or 0.2 mg/ml) was incubated with PQS and/or vitamin C for 30 min at 20 degrees C. Oxidative modification was initiated with 2 microM or 5 microM CuSO4 at 37 degrees C for (0-24 h. Pretreatment with PQS (100 microg/ml) reduced alterations in phospholipids, lipid peroxide levels and relative electrophoretic mobility of Ox-LDL. The presence of vitamin C (1-10 microM) significantly enhanced the protective effects of PQS. Pretreatment with PQS (1-100 microg/ml) resulted in concentration-dependent inhibition of LDL oxidation and prolongation of lag time as determined from measurements of conjugated lipid hydroperoxide content in Ox-LDL samples. Interestingly, the inhibitory actions of lower amounts of PQS (1 and 10 microg/ml) on the formation of conjugated dienes were significantly increased when vitamin C (0.1 or 1 microM) was present. In conclusion, our results suggest that PQS not only have direct antioxidant property but at low concentrations, their actions can be enhanced by vitamin C.

Ascorbic Acid↗
PubMed2000

Acetylcholine-mediated relaxation in rat thoracic aorta is enhanced following acute exposure to physiological concentrations of 17beta-estradiol.

We investigated the effects of short-term exposure to low concentrations of 17beta-estradiol on vasorelaxation using an in vitro rat thoracic aortic ring preparation. Supraphysiological levels of 17beta-estradiol directly relaxed phenylephrine-contracted rings. Although acute incubation (20 min) with 1-100 nM of the female sex hormone did not have any significant effect on phenylephrine-contracted rings, relaxation evoked by acetylcholine was significantly potentiated. In contrast, calcium ionophore A23187-elicited endothelium-dependent relaxation as well as cromakalim- and sodium nitroprusside-mediated endothelium-independent relaxation was unchanged following the same regime with 17beta-estradiol. These results demonstrate that short-term treatment with physiologically relevant levels of 17beta-estradiol, which on their own have no effect, enhances endothelium-dependent relaxation by acetylcholine. The vascular effects observed herein may partly account for some of the improved acute vasodilatory responses reported with 17beta-estradiol on blood flow in humans.

Acetylcholine↗
PubMed2000

High-throughput quantitative analysis of hepatitis B virus DNA in serum using the TaqMan fluorogenic detection system.

Reproducible quantitative assays to detect viral nucleic acids have proven useful in defining disease progression and following response to therapy in a wide variety of viral infections. We describe the development of a quantitative assay to detect hepatitis B virus (HBV) DNA using real-time fluorescent-probe polymerase chain reaction (PCR) (TaqMan). The assay is highly reproducible, highly automated, and much more sensitive than the currently used branched-chain DNA (bDNA) assay for HBV. The quantitative PCR assay accurately detected samples ranging from 10 to 10(9) copies of HBV DNA per milliliter. Of 157 serum samples submitted for HBV quantitation, 119 were positive by TaqMan PCR versus only 55 by bDNA (P <.001). All 55 bDNA-positives were positive by TaqMan. Of the 77 samples with detectable HBV-DNA titers below 3.75 x 10(5) copies by TaqMan, only 13 were detected by bDNA. We tested 119 patients negative for all HBV serologic markers, and all tested negative in the TaqMan assay. HBV DNA was detected by TaqMan in 164 of 195 (84%) of hepatitis B surface antigen (HBsAg)-positive samples. Among hepatitis B e antigen (HBeAg)-positive samples, median titers were 4. 3 x 10(6) copies/mL versus 322 copies/mL in HBeAg-negative samples (P =.012). The TaqMan assay for HBV DNA is highly sensitive and reproducible and thus appears useful in accurately defining levels of viral replication among persons with HBV infection.

Computer Systems↗
PubMed2000

Desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in piglets.

OBJECTIVE: Desmethyl tirilazad is a lipid-soluble free radical quencher. Deferoxamine reduces free radicals by chelating iron and reducing hydroxyl formation. Free radical inhibitors have shown promise in several hypoxic ischemic brain injury models, and we wished to see if this work could be extended to our newborn piglet model. DESIGN: Randomized controlled trial. SUBJECTS: Piglets (0 to 3 days old). INTERVENTION: Carotid snares and arterial and venous catheters were placed under 1.5% isoflurane anesthesia. In Experiment 1, piglets were randomly assigned to receive either 3 mg/kg desmethyl tirilazad or vehicle at -15 and 90 mins. In Experiment 2, piglets were randomly assigned to receive either 20 mg/kg desmethyl tirilazad at -15 mins followed by 8 mg/kg/hr for 90 mins or 100 mg/kg deferoxamine at -15 mins or vehicle. At time 0, both carotid arteries were clamped and blood was withdrawn to reduce the blood pressure to two-thirds normal. At 15 mins, inspired oxygen was reduced to 6%. At 30 mins, the carotid snares were released, the withdrawn blood was reinfused, and the oxygen was switched to 100%. On the third day after the hypoxic ischemic injury, the animals were killed by perfusing their brains with 10% formalin. We tested the timing of lipid peroxidation and inhibition of lipid peroxidation by these agents by freezing the brains of a subset of pigs in liquid nitrogen. MEASUREMENTS: Neurologic examination and brain pathology were scored by blinded observers. Thiobarbituric acid-reactive substance and oxidized and reduced glutathione were measured on frozen brains. MAIN RESULTS: Desmethyl tirilazad (20 mg/kg) and 100 mg/kg deferoxamine inhibit lipid peroxidation. Desmethyl tirilazad (20 mg/kg) improves neurologic exam, but 3 mg/kg Desmethyl tirilazad or 100 mg/kg deferoxamine does not. Neither desmethyl tirilazad nor deferoxamine improves pathologic results. CONCLUSIONS: High-dose desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in the newborn piglet.

Animals↗
PubMed2000

Magnetoencephalographic characterization of sleep spindles in humans.

Sleep spindles in EEG recordings of adults are most prominent over the central and frontal midline regions. Early magnetoencephalographic recordings agreed with conventional EEG findings. However, more recent small-array magnetoencephalography and quantitative EEG studies suggest that the source areas for spindles are more widespread. We used a whole-head 122-channel biomagnetometer to characterize the sources of sleep spindles in four normal volunteers. Parallel interactive and automated multiple dipole spatiotemporal source modeling was conducted on the data sets of 10 spindles from each subject. Principal component analysis was used to estimate the number of sources in interactive source modeling, and singular value decomposition was used in automated dipole modeling. Spectral analysis of the epochs containing sleep spindles was performed. Principal component analysis and singular value decomposition suggested that all sleep spindles were made up of activity from multiple sources. Similarly, interactive and automated multiple dipole source modeling showed that three or more sources were present in 75% of spindle bursts. The sources for sleep spindles localized to all four cerebral lobes. Parietal and frontal lobes were the areas most frequently involved. Interactive source modeling resulted in more frequent temporal lobe than occipital dipole localizations; automated source modeling showed more frequent occipital than temporal sources. Spindle source localizations varied across subjects and across different spindles within subjects. Our results indicate that individual sleep spindles are generated by multiple cortical sources that are widespread within and across individuals.

Adolescent↗
PubMed2000

Paired MEG data set source localization using recursively applied and projected (RAP) MUSIC.

An important class of experiments in functional brain mapping involves collecting pairs of data corresponding to separate "Task" and "Control" conditions. The data are then analyzed to determine what activity occurs during the Task experiment but not in the Control. Here we describe a new method for processing paired magnetoencephalographic (MEG) data sets using our recursively applied and projected multiple signal classification (RAP-MUSIC) algorithm. In this method the signal subspace of the Task data is projected against the orthogonal complement of the Control data signal subspace to obtain a subspace which describes spatial activity unique to the Task. A RAP-MUSIC localization search is then performed on this projected data to localize the sources which are active in the Task but not in the Control data. In addition to dipolar sources, effective blocking of more complex sources, e.g., multiple synchronously activated dipoles or synchronously activated distributed source activity, is possible since these topographies are well-described by the Control data signal subspace. Unlike previously published methods, the proposed method is shown to be effective in situations where the time series associated with Control and Task activity possess significant cross correlation. The method also allows for straightforward determination of the estimated time series of the localized target sources. A multiepoch MEG simulation and a phantom experiment are presented to demonstrate the ability of this method to successfully identify sources and their time series in the Task data.

Algorithms↗
PubMed2000

Complete nucleotide sequence and genome organization of hibiscus chlorotic ringspot virus, a new member of the genus Carmovirus: evidence for the presence and expression of two novel open reading frames.

The complete nucleotide sequence of hibiscus chlorotic ringspot virus (HCRSV) was determined. The genomic RNA (gRNA) is 3,911 nucleotides long and has the potential to encode seven viral proteins in the order of 28 (p28), 23 (p23), 81 (p81), 8 (p8), 9 (p9), 38 (p38), and 25 (p25) kDa. Excluding two unique open reading frames (ORFs) encoding p23 and p25, the ORFs encode proteins with high amino acid similarity to those of carmoviruses. In addition to gRNA, two 3'-coterminated subgenomic RNA (sgRNA) species were identified. Full-length cDNA clones derived from gRNA and sgRNA were constructed under the control of a T7 promoter. Both capped and uncapped transcripts derived from the full-length genomic cDNA clone were infectious. In vitro translation and mutagenesis assays confirmed that all the predicted ORFs except the ORF encoding p8 are translatable, and the two novel ORFs (those encoding p23 and p25) may be functionally indispensable for the viral infection cycle. Based on virion morphology and genome organization, we propose that HCRSV be classified as a new member of the genus Carmovirus in family Tombusviridae.

3' Untranslated Regions↗
PubMed2000

Elevated phosphorylation of AKT and Stat3 in prostate, breast, and cervical cancer cells.

We examined whether the persistent activation of AKT or Stat3 oncogene product is present in prostate, breast, and cervical cancer cells. We found that some prostate and breast cancer cell lines express high levels of phosphorylated AKT. Interestingly, the cancer cells, which only express low levels of phosphorylated AKT express high levels of phosphorylated Stat3. AKT or Stat3 is also highly phosphorylated in human papilloma virus-negative cervical cancer cells. Therefore, these results indicate that AKT and Stat3 are highly phosphorylated in some breast, prostate and cervical cancer cells, which may play a role in tumorigenesis of these cancers.

Breast Neoplasms↗
PubMed2000

[Effect of rhTFAR19 protein on cell cycle and apoptosis of MCF-7 induced by gamma-ray].

OBJECTIVE: To investigate the effect of protein product of TFAR19, an apoptosis-related gene previously cloned from leukemia cell line TF-1 cultured in medium deprived of growth factor, on cell cycle and apoptosis of human breast cancer induced by gamma-ray. METHODS: Cell morphology, fluorescence microscopy, laser scanning confocal microscopy, single-cell gel electrophoresis (SCGE) and flow cytometry (FCM) were applied to study cell cycle and apoptosis of breast cancer cell line MCF-7. RESULTS: rhTFAR19 protein itself had no effect on cell cycle arrest and apoptosis of MCF-7 cell induced by gamma-ray. When MCF-7 cells were pretreated with 10 micrograms/ml rhTFAR19 and then irradiated with 12 Gy gamma-ray, cell apoptosis was observed. It was characterized morphologically by chromatin condensation, nucleoar disintegration, formation of apoptotic bodies, and typical "cornet" on SCGE. CONCLUSION: TFAR19 protein has no apparent effect on MCF-7 cell cycle induced by gamma-ray. However, it synergizes with gamma-radiation in the induction and enhancement of apoptosis.

Apoptosis↗
PubMed2000

[Factors influencing survival rate in adenoid cystic carcinoma of the salivary glands].

OBJECTIVE: To study factors influencing survival rate of adenoid cystic carcinoma (ACC) of the salivary glands. METHODS: One hundred and twelve cases were followed up for move than ten years and were studied to investigate factors influencing the survival rate of patients. Statistical analysis was performed using a computer program (Survcalc, John Wiley Co.). The data were statistically treated for survival curves according to the kaplan-meier method. The log rank tests were employed to assess the statistical significance of various groups. RESULTS: The age of the patients younger than 50 years old, early clinical stage, glandular/tubular histological type and tumor without nerve involvement had the best prognosis. Age of the patients older than 50 years old, ACC in the submandibular gland, advanced clinical stage (stage III and IV), solid histological type and tumor with nerve involvement had a poor prognosis. CONCLUSIONS: Age of the patients, tumour site, clinical stage, histological type and with or without nerve involvement are the important factors influencing the prognosis.

Adolescent↗
PubMed2000

[The effects of cyclin E on the growth and other cell cycle related genes of breast carcinoma cells MCF-7].

OBJECTIVE: To investigate the effects of cyclin E in high and low expression on the cell growth and other cell cycle associated genes of MCF-7 cells. METHODS: Eukaryotic expression vehicles of sense and antisense cyclin E were constructed and transferred into the MCF-7 cell line using lipofectAMINE. The integration and expression of cyclin E were conformed by Southern and Western blot. The cells growth was observed and the changes in cell cycle were analyzed by flow cytometry. The expression of other cell cycle associated genes was assayed using Western blot. RESULTS: A high expression of cyclin E enabled to promote the cell growth and DNA synthesis and accelerated the proceeding of G(1) phase to S phase, It also promoted the phosphorylatin of pRB and up-regulate the expression of p27 while a low expression of cyclin E showed an opposite effect. CONCLUSION: Different expression of cyclin E enables to affect growth of MCF-7 cell by the changes of cell cycle related genes.

Breast Neoplasms↗
PubMed2000

[Relation between myocardial cAMP and renin-angiotensin system activation after acute pressure overload].

In order to investigate the relationship between cAMP and myocardial renin-angiotensin system activation after acute pressure overload, an animal model of acute pressure overload was established by constriction of abdominal aorta. It was found that angiotensin converting enzyme (ACE) mRNA and protein expression were increased markedly, ACE activity and angiotensin II content were also elevated significantly in rat heart 1 h after acute pressure overload, and the increases were kept at high level. Meanwhile the myocardial cAMP concentration was increased significantly at 0.5 h, reached the peak at day 5, and returned to normal at day 30 after operation. Then cardiomyocytes were cultured to observe whether ACE gene expression can be induced by cAMP. The results showed that elevation of cAMP content in cultured cardiomyocytes stimulated by isoproterenol (ISO, 0.01 micromol/L) increased ACE mRNA and protein expression, and also increased ACE activity and Ang II content in cultural medium. These results suggest that cAMP plays a role in the mechanism of activation of myocardial renin-angiotensin system induced by pressure overload.

Animals↗
PubMed2000

[The effect of adrenalectomy on morphine dependence behavior of rats with forced-swimming].

In this study, the possible action of stress and glucocorticoids on the drug-seeking behavior was explored in the rats with morphine dependence. Forty rats were assigned into four groups randomly and received different treatments as follows: adrenalectomy; adrenalectomy + hydrocortisone 20 mg/kg S.C.; adrenalectomy + hydrocortisone 40 mg/kg S.C.; saline S.C.; The effect of adrenalectomy and hydrocortisone on morphine conditioned place preference (CPP) in rats with forced-swimming was observed. The results showed: 1. there was no significant difference for the adrenalectomized rats' spending time between the morphine and saline-paired side during the test session (t = 1.84, P > 0.05), but obvious differences of time spent between the morphine and saline-paired side were observed among the other three groups (P < 0.05 or P < 0.01); 2. the time spent in the morphine-paired side of the adrenalectomized group significantly decreased, compared with those of the other three groups, and there was no difference for the time spent in the morphine-paired side among the groups of adrenalectomy + hydrocortisone 20 mg/kg S.C., adrenalectomy + hydrocortisone 40 mg/kg S.C., and saline S.C.. These data suggested that adrenalectomy could decrease the facilitation action of morphine CPP induced by forced swimming in rats, whereas administration with glucocorticoids should reverse this effect.

Adrenalectomy↗
PubMed2000

[Species and distribution of medicinal plant Hypericum in Guizhou].

OBJECTIVE: To gain a clear idea on the resources of medicinal plant Hypericum in Guizhou. METHOD: Conducting field investigation and consulting related specimens and data. RESULT: The distribution, growing environment and medicinal parts of 18 species of Hypericun have been clarified, and a key for their identification is given. CONCLUSION: A scientific basis for further study of the medicinal plant Hypericum in Guizhou Province has been provided.

Antiviral Agents↗
PubMed2000

[Effects of sulpiride on morphine-induced reward and its relation to cyclic AMP levels in mice].

This study examined the effects of sulpiride, a dopamine D2 receptor antagonist, on morphine rewarding properties and its relation to cyclic AMP levels in brain. The morphine-induced reward in mice was observed in a conditioned place preference test. Cyclic AMP was estimated by radioimmunoassay. The time of staying in morphine pairing compartment and the cAMP levels in brain of mice in the morphine group increased as compared with those in other groups (P < 0.05), but there was no significant difference in the time of staying in morphine pairing compartment and the cAMP levels in brain between the saline group and the sulpiride plus morphine groups (P > 0.05). These suggest that the inhibition of morphine-induced reward by sulpiride be due to the prevention of an increase in cyclic AMP levels in brain.

Animals↗
PubMed2000

[Comparison of total saponin content in three wild species of Gynostemma on Mount Emei].

Analysed by TLC and spectrometry, the content of the total saponin in three wild species of Gynostemma on Mount Emei is found to be the highest in July and to be the lowest in the seedling stage. Among the three, the content of the total saponin in Gynostemma pentaphyllum is the highest, that in Gynostemma pubescens lower and that in Gynostemma longipes the lowest.

Altitude↗