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Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 163 records · Page 9Linked to original sources
PubMed2001

The bone morphogenic protein antagonist gremlin regulates proximal-distal patterning of the lung.

The proximal-distal patterning of lung epithelium involves a complex series of signaling and transcriptional events resulting in the programmed differentiation of highly specialized cells for gas exchange and surfactant protein expression essential for postnatal lung function. The BMP signaling pathway has been shown to regulate cellular differentiation in the lung as well as other tissues. In this report, we show that the can family of related BMP antagonists, including gremlin, cer-1, PRDC, and Dan are expressed in the lung during embryonic development with gremlin expression observed in the proximal airway epithelium. The role of gremlin in lung development was explored by overexpressing it in the distal lung epithelium of transgenic mice using the human SP-C promoter. SP-C/gremlin transgenic mice exhibited a disruption of the proximal-distal patterning found in the airways of the mammalian lung. Expanded expression of the proximal epithelial cell markers CC10 and HFH-4 (Foxj1) was observed in the distal regions of transgenic lungs. Furthermore, smooth muscle alpha-actin expression was observed surrounding the distal airways of SP-C/gremlin mice, indicating a proximalization of distal lung tubules. These data suggest that gremlin plays an important role in lung morphogenesis by regulating the proximal-distal patterning of the lung during development.

Animals↗
PubMed2001

Assessing the effect of sampling strategies on the power of linkage analysis to identify pathway-specific loci underlying a complex disease.

Using the simulated general population data sets, we first examined the effect of sampling strategies on the power of identifying linkage by selecting samples with (A) two affected sibs in a nuclear family and (B) one affected sib and one sib with an intermediate trait value in the upper quantiles. Second, we evaluated the improvement in power when analyzing correlated traits simultaneously. Under each selection criteria, 100 replicates of 300 nuclear families were sampled and analyzed with two-point linkage analysis for ten markers (1 cM apart) from each of the candidate regions. Different genes were identified under different sampling strategies. When a gene has a pleitropic effect, it is more powerful to analyze correlated traits simultaneously, either by using a linear combination or the larger value of standardized traits, than to analyze each trait separately.

Chromosome Mapping↗
PubMed2001

Embryonic-derived glial-restricted precursor cells (GRP cells) can differentiate into astrocytes and oligodendrocytes in vivo.

We have isolated and characterized a unique glial-restricted precursor cell (GRP) from the embryonic spinal cord. Clonal analysis demonstrated that these cells are able to generate oligodendrocytes and two distinct type of astrocytes (type 1 and type 2) when exposed to appropriate signals in vitro. We now show that many aspects of these cells are retained in vivo. GRP cells are restricted to the glial lineage in vivo as they seem to be unable to generate neuronal phenotypes in an in vivo neurogenic environment. GRP cells survive and migrate in the neonatal and adult brain. Transplanted GRP cells differentiate into myelin-forming oligodendrocytes in a myelin-deficient background and also generate immature oligodendrocytes in the normal neonatal brain. In addition, GRP cells also consistently generated glial fibrillary protein-expressing cells in the neonatal and adult brain, a property not consistently expressed by other glial precursor cells like the O-2A/OPC cells. We suggest that the lineage restriction of GRP cells and their ability to generate both oligodendrocytes and astrocytes in vivo together with their embryonic character that allows for extensive in vitro expansion of the population makes the cell useful for clinical application.

Animals↗
PubMed2001

Ionized magnesium in the homeostasis of cells: intracellular threshold for Mg(2+) in human platelets.

The role of extracellular magnesium ions in the homeostasis of intracellular ionized magnesium ([Mg(2+)](i)) in human platelets was studied. For media containing 0.00 to 0.60 mmol/l of extracellular ionized magnesium ([Mg(2+)](o)), the mean [Mg(2+)](i) fluctuated between 533 and 760 micromol/l. As the [Mg(2+)](o) was increased to 1.5 mmol/l, the [Mg(2+)](i) increased proportionately and peaked at 1470.1 micromol/l. Additional increase in the [Mg(2+)](o) from 1.50 to 6.00 mmol/l resulted in decreased [Mg(2+)](i) until it equilibrated between 739 and 776 micromol/l. The influx of Mg(2+) at [Mg(2+)](o) of 0.60 and 1.50 mmol/l was studied using verapamil, a calcium channel inhibitor, and ouabain, an inhibitor of the Na/K pump, respectively. The verapamil (25 mmol/l) blocking experiments resulted in a 92.4% inhibition of the Mg(2+) influx into the platelet at a [Mg(2+)](o) of 1.50 mmol/l. Ouabain (0.5 and 2.5 mmol/l) showed an enhancement effect on the influx of Mg(2+) at [Mg(2+)](o) of 0.60 mmol/l and no effect at 1.50 mmol/l. The effect of verapamil indicates that ion channels that are homologous to calcium ion channels may be involved in the influx of Mg(2+) into the platelets. The inhibition of Mg(2+) influx for [Mg(2+)](o) greater than 1.50 mmol/l may illustrate a protective mechanism that attempts to maintain the viability of platelets at abnormally high [Mg(2+)](o). These results suggest that there is an intracellular Mg(2+) threshold of 1500 micromol/l, above which an active mechanism prevents further influx of Mg(2+).

Blood Platelets↗
PubMed2001

Effect of acid and surfactant treatment on activated sludge dewatering and settling.

The effect of pretreating activated sludge with sulfuric acid and surfactant on its exocellular polymer(ECP), dewaterability and settleability was investigated. It was observed that the centrifugal dewatering efficiency was increased with the decrease of sludge pH value, and which was further improved if the surfactant was simultaneously applied. However, to the filtration dewatering, the water content reached the minimum in the case of pH 2.5, and the additional use of surfactant was also favorable. The water content of sludge dewatered with filtration reached 73.99% when a pH 2.5 and a 0.1 g surfactant were employed, which was reduced by around 2% as compared with surfactant unused. Experimental results indicated that the sludge sedimentation rate was significantly accelerated under pH 2.5 condition, and which was increased once more by the utilization of surfactant. Further studies revealed that treating activated sludge with sulfuric acid at pH 2.5 or combined with surfactant was an effective method to remove the polymers from sludge surface and induced the decrease of ECP, which resulted in the improvement of dewaterability and settleability. This study suggested the potentiality of improving activated sludge mechanical dewaterability by the use of sulfuric acid to control its pH at 2.5 or together with a surfactant.

Acids↗
PubMed2001

Effects of age and food restriction on oxidative DNA damage and antioxidant enzyme activities in the mouse aorta.

In this study, DNA damage in mouse aortic cells was measured using the comet assay. The tail moment of the comet assay in aortic cells obtained from 26-month-old mice fed ad libitum (O-AL) was significantly increased as compared to 6-month-old mice fed ad libitum (Y-AL) after the cells were incubated with formamidopyrimidine-DNA glycosylase (Fpg), which specifically recognizes oxidized purines, endonuclease III (Endo III), which specifically recognizes oxidized pyrimidines, or the combination of Endo III and Fpg. The tail moment in aortic cells obtained from 26-month-old mice fed a food-restricted diet (O-FR) was significantly reduced as compared to O-AL mice after the cells were incubated with the combination of Endo III and Fpg. These results indicate that oxidative DNA lesions, i.e. the Endo III- and Fpg-sensitive sites, increase with age in mouse aortic cells and that FR attenuates the age-related increase in oxidative DNA damage. To determine if the changes in oxidative DNA damage in mouse aortic cells are related to the antioxidant status in these cells, we measured the activities of Cu/Zn-superoxide dismutase (SOD), Mn-SOD, extracellular-SOD, catalase and glutathione peroxidase-1 in the mouse aorta. We observed that the activities of all antioxidant enzymes studied were significantly increased with age and that FR attenuated the age-related increase. These data indicate that the age-related increase and FR-induced decrease in oxidative DNA damage, i.e. the Endo III- and Fpg-sensitive sites, in mouse aortic cells is not due to alteration of the antioxidant defense system.

Aging↗
PubMed2001

Modeling and prediction for discharge lifetime of battery systems using hybrid evolutionary algorithms.

A hybrid evolutionary modeling algorithm (HEMA) is proposed to build the discharge lifetime models with multiple impact factors for battery systems as well as make predictions. The main idea of the HEMA is to embed a genetic algorithm (GA) into genetic programming (GP), where GP is employed to optimize the structure of a model, while a GA is employed to optimize its parameters. The experimental results on lithium-ion batteries show that the HEMA works effectively, automatically and quickly in modeling the discharge lifetime of battery systems. The algorithm has some advantages compared with most existing modeling methods and can be applied widely to solving the automatic modeling problems in many fields.

Algorithms↗
PubMed2001

Characterization of interaction between C-domain on HIV-1 gp41 and the putative receptor protein p62.

Based on the fact that the binding of HIV-1 gp41 to the putative cellular receptor protein p62 could be inhibited by the C-domain peptide of gp41, we wanted to confirm the interaction of the C-domain with p62 and to characterize the receptor-binding site on the C-domain. We attempted to isolate the putative receptor protein p62 from cell lysates of the human B cell line Raji by affinity chromatography using sepharose-columns which were conjugated with three different peptides of the C-domain respectively. A protein of 62 kDa was isolated by peptide (NP2)-sepharose-column, while none of the proteins was identified in eluates of the other two overlapped peptides of C-domain, indicating that HIV-1 gp41 by the region aa635-664 of C-domain binds to the putative receptor protein p62. Besides, CD spectroscopy analysis revealed that only a NP2 peptide could induce significant conformational change of P62. In addition, the interaction between P62 and three peptides of the C-domain was characterized by the surface plasma resonance (SPR) measurement. It was indicated that only the NP2 peptide significantly inhibited the interaction between rsgp41 and the putative receptor P62, confirming that the protein p62 may serve as a potential receptor for gp41 binding, and the peptide NP2 contains an integrate binding site for gp41 binding to p62.

Amino Acid Sequence↗
PubMed2001

Storage and distribution of trace metals and spheroidal carbonaceous particles (SCPs) from atmospheric deposition in the catchment peats of Lochnagar, Scotland.

Lochnagar is a remote mountain lake to the south-east of the Cairngorm region in Scotland. Its catchment receives anthropogenic trace metals solely from atmospheric deposition. Ten peat cores were taken from the catchment and analysis confirmed that they have been contaminated by trace metals. The peats have an high affinity for trace metals and this results in metal accumulation in the surface peat layers. The formation of trace metal sulphides may also reduce remobilisation. In this way, trace metals derived from atmospheric deposition have been scavenged and accumulated. In contaminated peat layers, 77.4% Hg, 89.6% Pb, 93.4% Cu, 72.4% Zn and 86.5% Cd of the total stored are from anthropogenic sources. The accumulated trace metals in the peats can potentially influence the lake system through erosion. Spheroidal carbonaceous particle (SCP) profiles were used to date the peat cores. By referring to the SCP profiles in the peats and comparing these with the trace metal profiles in the lake sediments, the mobility of trace metals in the catchment peats is confirmed.

Air Pollutants↗
PubMed2001

Retroviral manipulation of the expression of bone morphogenetic protein receptor Ia by SVZa progenitor cells leads to changes in their p19(INK4d) expression but not in their neuronal commitment.

Bone morphogenetic proteins (BMPs), a group of cytokines in the TGF-beta superfamily, have complex regulatory roles in the control of neural proliferation and cell fate decision. In this study, we analyzed the potential role(s) of BMP signaling on the regulation of the proliferation and differentiation of the unique progenitor cells of the neonatal anterior subventricular zone (SVZa). Unlike other progenitor cells of the brain, SVZa progenitor cells have the capacity to divide even though they express a neuronal phenotype. In order to augment or inhibit endogenous BMP signaling, we injected into the neonatal rat SVZa replication-deficient retroviruses encoding for either the wild-type BMP receptor subtype Ia (wt-BMPR-Ia) or a mutated dominant-negative version of BMPR-Ia (dn-BMPR-Ia) in conjunction with a reporter gene, human alkaline phosphatase (AP) and perfused the pups 1, 4 and 7 days post injection. We analyzed whether changing the expression of BMPR-Ia has an effect on the spatial-temporal expression pattern of the cyclin dependent kinase inhibitor, p19(INK4d), or on the phenotype of SVZa derived cells. The results of our study confirmed and extended our previous findings that in control (non injected) animals, the rostral migratory stream (RMS), traversed by the SVZa-derived cells en route to the olfactory bulb, exhibits an anterior(high)-posterior(low) gradient of p19(INK4d) expression; p19(INK4d) expression is essentially absent in the SVZa and highest in the subependymal zone in the middle of the olfactory bulb. However, SVZa progenitor cells encoding the wt-BMPR-Ia gene express p19(INK4d) within the SVZa, suggesting that the BMPs induce SVZa cells to ectopically undergo cell cycle exit within the SVZa. Furthermore, unlike striatal SVZ progenitor cells, which acquire an astrocytic phenotype when exposed to BMPs, SVZa progenitor cells retain their neuronal commitment under augmented BMP signaling.

Alkaline Phosphatase↗
PubMed2001

Myc requires distinct E2F activities to induce S phase and apoptosis.

Previous work has shown that the Myc transcription factor induces transcription of the E2F1, E2F2, and E2F3 genes. Using primary mouse embryo fibroblasts deleted for individual E2F genes, we now show that Myc-induced S phase and apoptosis requires distinct E2F activities. The ability of Myc to induce S phase is impaired in the absence of either E2F2 or E2F3 but not E2F1 or E2F4. In contrast, the ability of Myc to induce apoptosis is markedly reduced in cells deleted for E2F1 but not E2F2 or E2F3. From this data, we propose that the induction of specific E2F activities is an essential component in the Myc pathways that control cell proliferation and cell fate decisions.

Adenoviridae↗
PubMed2001

Peptide signals and their receptors in higher plants.

At least four peptides play a vital role in plant cell-cell communication by means of their specific receptors. Two of these receptors have been identified as receptor kinases, which form a large family of receptor molecules in plants. These findings highlight the significance of receptor-mediated peptide signaling in various physiological events in plants, and predict the existence of further peptide-signal-interacting receptor kinases. Some candidates have been found in plant genomes. Here, we outline recent progress and future challenges in the signaling peptide analysis, which began with systemin, phytosulfokine, CLAVATA3 and S-locus cysteine-rich protein (also called S-locus protein 11).

Arabidopsis↗
PubMed2001

Development of an enzyme-linked immunosorbent assay for the determination of maduramicin in broiler chicken tissues.

Maduramicin is one of the most widely used coccidiostats in the world. A rapid and accurate analytical method for this drug should provide producers and users with an effective management tool. The current chromatographic methods are sensitive but labor-intensive. This paper reports the development of an enzyme-linked immunosorbent assay (ELISA) based on an immunoaffinity chromatography cleanup procedure for the analysis of maduramicin in broiler chicken tissues (including muscle, liver, and fat). Recoveries from fortified tissue homogenates at levels of 30.0-120.0 microg kg(-)(1) ranged from 76.4 to 107.5% with coefficients of variation of 3.8-16.4%. The limits of detection were 1.0 ng g(-)(1) in muscle, 2.8 ng g(-)(1) in liver, and 1.5 ng g(-)(1) in fat. The ELISA results from the analysis of incurred residue in tissue samples showed the cleanup procedure is viable.

Adipose Tissue↗
PubMed2001

High-efficiency volume reduction of cord blood using pentastarch.

Human umbilical cord blood (UCB) has been used successfully to treat a variety of genetic, hematological, and oncologic disorders. However, the low number of hematopoietic progenitor cells available in donated cord blood samples limits transplantation of cord blood to children and small adults. Reduction of the volume of umbilical cord blood is widely used in cord blood banking to reduce the storage requirements in large-scale UCB banks. Unfortunately, during the volume reduction process, up to 40% or more of the progenitor cells are lost using current reduction methods. This study describes a highly reproducible, double collection technique using Pentaspan to reduce UCB volume by red cell depletion. This results in the preservation of critical hematopoietic progenitor cells. The final volume of the leukocyte concentrates (LC) was 19.8 +/- 0.4 ml with 95% red cell depletion. The recovery of nucleated cells (NC), mononuclear cells (MNC), CD34(+) cells and colony-forming units (CFU) following double collection was 89%, 94%, 96%, and 106%, respectively. This is significantly higher than the recovery from single collections, where recovery was 74%, 77%, 84%, and 91% for NC, MNC, CD34(+) and CFU, respectively. The double collection technique provides an efficient and highly reproducible method for the preparation of UCB for long-term storage and transplantation.

Blood Banks↗