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Biomedical subjects

Y Yang

Publications and source records attributed to Y Yang.

At least 415 records · Page 23Linked to original sources
PubMed2000

Biodistribution, metabolism, and in vivo gene expression of low molecular weight glycopeptide polyethylene glycol peptide DNA co-condensates.

The biodistribution, metabolism, cellular targeting, and gene expression of a nonviral peptide DNA gene delivery system was examined. (125)I-labeled plasmid DNA was condensed with low molecular weight peptide conjugates and dosed i.v. in mice to determine the influence of peptide DNA formulation parameters on specific gene targeting to hepatocytes. Optimal targeting to hepatocytes required the combined use of a triantennary glycopeptide (Tri-CWK(18)) and a polyethylene glycol-peptide (PEG-CWK(18)) to mediate specific recognition by the asialoglycoprotein receptor and to reduce nonspecific uptake by Kupffer cells. Tri-CWK(18)/PEG-CWK(18) DNA co-condensates were stabilized and protected from metabolism by glutaraldehyde crosslinking. An optimized formulation targeted 60% of the dose to the liver with 80% of the liver targeted DNA localized to hepatocytes. Glutaraldehyde crosslinking of DNA condensates reduced the liver elimination rate from a t((1/2)) of 0.8 to 3.6 h. An optimized gene delivery formulation produced detectable levels of human alpha1-antitrypsin in mouse serum which peaked at day 7 compared to no expression using control formulations. The results demonstrate the application of formulation optimization to improve the targeting selectivity and gene expression of a peptide DNA delivery system.

Animals↗
PubMed2000

A silent event-related functional MRI technique for brain activation studies without interference of scanner acoustic noise.

A new data acquisition method for silent, event-related functional MRI in which scanner acoustic noise does not interfere with brain activation is introduced and evaluated in an auditory tonotopic mapping experiment. This method takes into account the hemodynamic-response characteristics of the brain during activation, associated with both task performance and scanner noise. A data acquisition scheme was designed to collect task-induced brain activation signals without interference of scanner noise on stimulus delivery or on the measured response. The advantages of the technique were demonstrated in a tonotopic mapping experiment of human auditory cortex. Tonotopic maps obtained by the technique in normal subjects showed distinct spatial shifts of the activation foci in the lateral part of Heschl's gyrus with changing stimulus frequency, whereas no systematic shift was shown in a conventional event-related experiment using the same stimulation paradigm. Signal change in the activation foci with the new technique was 54% larger than with the conventional technique, suggesting an increased dynamic range of the signal change associated with task-induced brain activation under silent conditions.

Acoustic Stimulation↗
PubMed2000

H(2)(15)O PET validation of steady-state arterial spin tagging cerebral blood flow measurements in humans.

Steady-state arterial spin tagging approaches can provide quantitative images of CBF, but have not been validated in humans. The work presented here compared CBF values measured using steady-state arterial spin tagging with CBF values measured in the same group of human subjects using the H(2)(15)O IV bolus PET method. Blood flow values determined by H(2)(15)O PET were corrected for the known effects of incomplete extraction of water across the blood brain barrier. For a cortical strip ROI, blood flow values determined using arterial spin tagging (64+/-12 cc/100 g/min) were not statistically different from corrected blood flow values determined using H(2)(15)O PET (67+/-13 cc/100 g/min). However, for a central white matter ROI, blood flow values determined using arterial spin tagging were significantly underestimated compared to corrected blood flow values determined using H(2)(15)O PET. This underestimation could be caused by an underestimation of the arterial transit time for white matter regions.

Adult↗
PubMed2000

Transit time, trailing time, and cerebral blood flow during brain activation: measurement using multislice, pulsed spin-labeling perfusion imaging.

Transit time and trailing time in pulsed spin-labeling perfusion imaging are likely to be modulated by local blood flow changes, such as those accompanying brain activation. The majority of transit/trailing time is due to the passage of the tagged blood bolus through the arteriole/capillary regions, because of lower blood flow velocity in these regions. Changes of transit/trailing time during activation could affect the quantification of CBF in functional neuroimaging studies, and are therefore important to characterize. In this work, the measurement of transit and trailing times and CBF during sensorimotor activation using multislice perfusion imaging with pulsed arterial spin-labeling is described. While CBF elevated dramatically ( thick similar80.7%) during the sensorimotor activation, sizable reductions of transit time ( thick similar0.11 sec) and trailing time ( thick similar0.26 sec) were observed. Transit and trailing times were dependent on the distances from the leading and trailing edges of the tagged blood bolus to the location of the imaging slices. The effects of transit/trailing time changes on CBF quantification during brain activation were analyzed by simulation studies. Significant errors can be caused in the estimation of CBF if such changes of transit/trailing time are not taken into account.

Brain↗
PubMed2000

Evaluating the efficacy of citicoline in embolic ischemic stroke in rats: neuroprotective effects when used alone or in combination with urokinase.

The combination of thrombolysis with neuroprotection, because of different mechanisms, would be expected to show better results when used after onset of focal ischemia. In this study we report our experience with the neuronal protective effects of citicoline alone and in combination with urokinase in a model of focal ischemia. Both medications were injected 2 h after onset of a focal occlusion of the middle cerebral artery (MCA) in rats. Focal ischemia was produced with embolization of a clot into the origin of the MCA. This produces a large infarction involving the cortex and the basal ganglia. Animals were observed for neuronal deficts at 2 and 24 h after surgery and were sacrificed 72 h after onset of ischemia. Saline-treated animals showed a large infarction involving the cerebral cortex and basal ganglion in most animals (volume 33.1 +/- 9.7%). Animals treated with citicoline alone were divided in two groups. The first group of animals were treated with a single injection (300 mg/kg, ip) of the medication 2 h after the arterial occlusion. The second group was treated with the active medication intermittently (3 x 300 mg/kg, ip) over a 72-h period. There was a significant decrease in the neuronal damage in the cortex in the animals treated with citicoline (single dose, 20.9 +/- 9.7%, P = 0.01; intermittent injection, 18.9 +/- 11.4%, P < 0.008). The last experiment evaluated the usefulness of the combination of citicoline with intraarterial urokinase. The combination showed significantly more protection than with urokinase or citicoline alone (volume 13.6 +/- 9.1%, P < 0.001). We conclude from our experiments that citicoline may offer significant neuronal protection that may be further enhanced with the addition of a thrombolytic agent.

Animals↗
PubMed2000

Neuroprotection by 2-h postischemia administration of two free radical scavengers, alpha-phenyl-n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), in rats subjected to focal embolic cerebral ischemia.

Oxygen free radical generation may have important secondary damaging effects after the onset of cerebral ischemia. Free radical scavengers have been used successfully in attenuating neuronal damage in the reperfusion period in transient forebrain ischemia. There are limited data on effectiveness in models of focal ischemia. Two free radical scavengers, alpha-phenyl-n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), have been shown to reduce oxidative-stress-induced neuronal injury. Whereas PBN has been demonstrated to reduce infarct volume in focal ischemia, neuroprotection has not been evaluated with S-PBN. The present study was designed to evaluate the neuroprotective effect of PBN and S-PBN compared to vehicle in a focal embolic middle cerebral artery (MCA) cerebral ischemia model in rats. Wistar rats were randomly divided into three groups (n = 10 each group). Animals in the control group received vehicle and those in the treatment groups were treated with PBN or S-PBN (both 100 mg/kg/day x 3 days, intraperitoneally) starting 2 h after the introduction of an autologous thrombus into the right-side MCA. The neurological outcome was observed and compared before and after treatment and between groups. The percentage of cerebral infarct volume was estimated from 2,3, 5-triphenyltetrazolium chloride stained coronal slices 72 h after the ischemic insult. Two-hour postischemia administration of PBN or S-PBN significantly improved neurobehavioral scores at 24 h following MCA embolization (both P < 0.01). The percentage of infarct volume for animals receiving vehicle was 32.8 +/- 9.4%. Two-hour delayed administration of PBN and S-PBN achieved a 35.4% reduction in infarct volume in treatment groups when compared with animals receiving vehicle (PBN vs control, 21.2 +/- 10.9% vs 32.8 +/- 9.4%; P < 0.05; S-PBN vs control, 21.2 +/- 13.1%, (P < 0.05). These data indicate that free radical generation may be involved in brain damage in this model and 2-h delayed postischemia treatment with PBN and S-PBN may have neuroprotective effects in focal cerebral ischemia. As S-PBN does not normally cross the blood-brain barrier, the neuroprotection evident in this study may be explained by entry into the brain via damaged vessels.

Animals↗
PubMed2000

L-type Ca2+ channel alpha 1c subunit isoform switching in failing human ventricular myocardium.

UNLABELLED: The objectives of this study were to determine the relative abundance of the L-type Ca channel alpha 1c IVS3 isoforms that result from alternative splicing in normal human ventricular myocytes and to measure the changes in isoform expression in end stage heart failure. METHODS: mRNA was isolated from left ventricular tissue and myocytes from non-failing and failing human hearts. RT-PCR with isoform-specific primers was used to obtain cDNAs that were then mutated for use in competitive PCR reactions. An RNase protection assay was also used to confirm the presence of one of the novel isoforms. RESULTS: Four different alpha 1c IVS3 isoforms were found in non-failing human ventricular myocytes using RT-PCR. Two isoforms contained exon 31 (termed IVS3A isoforms) and two isoforms contained exon 32 (termed IVS3B isoforms). One of these isoforms has not been observed previously and contains exon 31 and all but the last six base pairs of exon 32. In non-failing human ventricular myocytes the IVS3A isoform is 2.5 times more abundant than the IVS3B isoform. There were significant changes in the relative abundance of these isoforms in failing hearts, with the IVS3B isoform being twice as abundant as the IVS3A isoform. All isoforms were confirmed by RNase protection analysis. CONCLUSIONS: These experiments show that there are at least four L-type Ca channel mRNA isoforms in the normal human heart and that the relative abundance of these isoforms changes significantly in heart failure. These alpha 1c isoform changes in heart failure are associated with dysfunctional electromechanical disturbances, but the specific physiological role of each L-type Ca channel isoform in normal and failing hearts needs to be defined.

Adult↗
PubMed2000

A CBF-based event-related brain activation paradigm: characterization of impulse-response function and comparison to BOLD.

A perfusion-based event-related functional MRI method for the study of brain activation is presented. In this method, cerebral blood flow (CBF) was measured using a recently developed multislice arterial spin-labeling (ASL) perfusion imaging method with rapid spiral scanning. Temporal resolution of the perfusion measurement was substantially improved by employing intertrial subtraction and stimulus-shifting schemes. Perfusion and blood oxygenation level-dependent (BOLD) signals were obtained simultaneously by subtracting or adding the control and labeled images, respectively, in the same data sets. The impulse response function (IRF) of perfusion during brain activation was characterized for multiple stimulus durations and compared to the simultaneously acquired BOLD response. The CBF response curve preceded the BOLD curve by 0.21 s in the rising phase and 0.64 s in the falling phase. Linear additivity of the CBF and BOLD responses was assessed with rapidly repeated stimulations within single trials, and departure from linearity was found in both responses, characterized as attenuated amplitude and delayed rising time. Event-related visual and sensorimotor activation experiments were successfully performed with the new perfusion technique.

Brain↗
PubMed2000

Expression of functional soluble human alpha-globin chains of hemoglobin in bacteria.

Individual, soluble human alpha-globin chains were expressed in bacteria with exogenous heme and methionine aminopeptidase. The yields of soluble alpha chains in bacteria were comparable to those of recombinant non-alpha chains expressed under the same conditions. Molecular mass and gel-filtration properties of purified recombinant alpha chains were the same as those of authentic human alpha chains. Biochemical and biophysical properties of isolated alpha chains were identical to those of native human alpha chains as assessed by UV/vis, circular dichroism (CD), and nuclear magnetic resonance (NMR) spectroscopy which contrasts with previous results of refolded precipitated alpha chains made in the presence of heme in vitro (M. T. Sanna et al., J. Biol. Chem. 272, 3478-3486, 1997). Mixtures of purified, soluble recombinant alpha-globin and native beta-globin chains formed heterotetramers in vitro, and oxygen- and CO-binding properties as well as the heme environment of the assembled tetramers were experimentally indistinguishable from those of native human Hb A. UV/vis, CD, and NMR spectra of assembled Hb A were also the same as those of human Hb A. These results indicate that individual expressed alpha chains are stable in bacteria and fold properly in vivo and that they then can assemble with free beta chains to form hemoglobin heterotetramers in vivo as well as in vitro.

Globins↗
PubMed2000

Metabolism of dauricine and identification of its main metabolites.

To study the metabolism of dauricine in vivo and in vitro and identify the structure of its main metabolites, urine of rats after drug administration as the samples of dauricine metabolism in vivo was studied. Rat liver S9 fraction was prepared and the oxygenation metabolism system reconstituted to perform phase I reaction of dauricine in vitro. TLC, HPLC-DAD and MS were used to analyze and identify dauricine and its main phase I metabolites in the samples. The results showed that besides the untransformed dauricine, in the urine samples there was little product of X' which had the same features of TLC, HPLC-DAD and MS as those of N-desmethyl dauricine (N-ddau). Part of dauricine could be transformed to a main metabolite X after incubating with S9 fraction in appropriate conditions. The molecular ion peak of X was m/z 611. The full scan MS2 spectrum of m/z 611 peak from S9 sample were m/z 580, m/z 566, m/z 552, m/z 206, which were same as those of N-ddau. Liver is the major organ for dauricine metabolism and part of dauricine is biotransformed by liver. The major metabolite is considered to be N-ddau.

Alkaloids↗
PubMed2000

Platelet fibrinogen in the patients with idiopathic bleeding platelet disorder.

The changes of platelet fibrinogen in patients with obscure cutaneous mucosal bleeding and their relation with disease were evaluated. By using flow cytometry and Western blot, the platelet binding site of fibrinogen and the expression of platelet fibrinogen in 8 cases of obscure bleeding were detected. The results showed that platelet surface binding sites of fibrinogen were 65.38 +/- 3.62 in the resting state and 65.25 +/- 5.78 after activated by adenosine diphosphate, showing no significant difference as compared with control group (P > 0.05). The expression of platelet fibrinogen was obviously decreased in 4 patients and increased in one case as compared with control group. It was concluded that the binding sites of fibrinogen on the platelet surface were normal in the patients with idiopathic bleeding platelet disorder. The abnormal of platelet fibrinogen might be one of hemorrhagic reasons in partial patients.

Adult↗
PubMed2000

Relationship between the expression of alpha 1-antitrypsinase in bronchioalveolar carcinoma and clinical pathology.

By using immunohistochemistry LSAB method and imaging analysis technique, the expression of alpha 1-antitrypsinase (alpha 1-AT) in 41 cases of bronchioalveolar carcinoma (BAC) was quantitatively detected to explore the relationship between alpha 1-AT expression in BAC tissues and clinical pathology. The results showed that the total positive rate for alpha 1-AT expression was 85.4%. The positive rate for alpha 1-AT expression in alveolar BAC was 100%, with the immunity reactive staining intensity being significantly higher than in papillary BAC, mucinous BAC or sclerosing BAC (P < 0.05). The positive rate in papillary BAC was 93.3%, with the intensity higher mucinous BAC or sclerosing BAC (P < 0.01); The positive rate in both mucinous BAC and sclerosing BAC was 66.7% (P > 0.05); The expression intensity in lymph node metastatic group was obviously lower than that in the group without metastasis (P < 0.01); The patients with mucinous BAC were diagnosed at a younger age than those with other histologic types of BAC (P < 0.05). It was suggested that BAC cells could also produce alpha 1-AT. Detection of alpha 1-AT could be used as a new method to diagnose BAC and might play a role in assessing BAC metastasis.

Adenocarcinoma↗
PubMed2000

A sensitive HPLC technique for the quantitation of dauricine.

To establish the determination method of dauricine (Dau) concentration in rats' blood and other biological samples, a reverse-phase HPLC method was adopted. Under the given condition, dauricine could be well separated. The retention time (tR) of Dau and its internal standard, daurisoline were 9.2 and 6.1 respectively. The detection limit was 10(-2) mg/ml. The absolute recoveries of all kinds of samples were above 70%, and the relative ones were over 85%. A good liner relationship has been obtained over the entire range of 0.030 to 3.000 mg/L in blood samples and 0.050 to 5.000 mg/L in other tissue samples. The intraday and interday coefficients of variation were below 10%. The results showed that the method can be used for detecting Dau in all kinds of biological samples.

Alkaloids↗
PubMed2000

Effects of Agricultural Chemicals on DNA Sequence Diversity of Soil Microbial Community: A Study with RAPD Marker.

The DNA sequence diversities for microbial communities in four soils affected by agricultural chemicals (mainly triadimefon and ammonium bicarbonate and their intermediates) were evaluated by Random Amplified Polymorphic DNA (RAPD) analysis. Fourteen random primers were used to amplify RAPDs from four soil microbial community DNAs. The products of 12 primers were separated in gel and generated 155 reliable fragments, of which 134 were polymorphic. The richness, modified richness, Shannon-Weaver index, and a similarity coefficient of DNA were calculated to quantify the diversity to access DNA sequence diversities for four soil microbial communities. The results showed that agricultural chemicals affected soil microbial community diversity at the DNA level. The four soil microbial communities were distinguishable in terms of DNA sequence richness, modified richness, Shannon-Weaver index, and coefficient of DNA similarity. Analysis also showed that the amounts of organic C and microbial biomass C were low in the soil polluted by pesticide (mainly triadimefon and its intermediates), but high in the soil polluted by chemical fertilizer (mainly ammonium bicarbonate and its intermediates). The above results combined may indicate that pesticide pollution caused a decrease in the soil microbial biomass but kept high diversity at DNA level, compared with the control without chemical pollution. In contrast, chemical fertilizer pollution caused an increase in the soil biomass but decrease in the DNA diversity. The RAPD marker technique combined with analysis of soil microbial biomass appears to be an effective approach for studying the diversity of soil microbial communities, although the effects of PCR bias on community composition, such as dominating and rare populations in soils, on the diversity needed to be addressed further. </hea

Journal Article↗
PubMed2000

Enhanced vulnerability to oxidative stress by alpha-synuclein mutations and C-terminal truncation.

alpha-Synuclein is a key component of Lewy bodies found in the brains of patients with Parkinson's disease and two point mutations in this protein, Ala53Thr and Ala30Pro, are associated with rare familial forms of the disease. Several lines of evidence suggest the involvement of oxidative stress in the pathogenesis of nigral neuronal death in Parkinson's disease. In the present work we studied the effects of changes in the alpha-synuclein sequence on the susceptibility of cells to reactive oxygen species. Human dopaminergic neuroblastoma SH-SY5Y cells were stably transduced with various isoforms of alpha-synuclein and their survival following exposure to hydrogen peroxide or to the dopaminergic neurotoxin MPP(+) was assessed. Cells expressing the two point mutant isoforms of alpha-synuclein were significantly more vulnerable to oxidative stress, with the Ala53Thr engineered cells faring the worst. In addition, cells expressing C-terminally truncated alpha-synuclein, particularly the 1-120 residue protein, were more susceptible than control beta-galactosidase engineered cells. The present experiments indicate that point mutations and C-terminal truncation of alpha-synuclein exaggerate the susceptibility of dopaminergic cells to oxidative damage. Thus, these observations provide a pathogenetic link between alpha-synuclein aberrations and a putative cell death mechanism in Parkinson's disease.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Effect of ethanol on thromboxane and prostacyclin production in the human placenta.

Fetal alcohol syndrome (FAS) is frequently associated with intrauterine growth retardation (IUGR). One cause of ethanol-induced IUGR is thought to be related to increased pressor activity in the human placenta, resulting in decreased oxygenation and nutrient transport to the fetus. Thus, we have investigated the effect of ethanol on paracrine substances, such as thromboxane and prostacyclin, that act as vasoregulators within the intrauterine tissues. In these studies we have utilized the perfused single human cotyledon system to study the effect of ethanol on placental prostanoid production. We assessed the effect of longer (240 min) and more acute (60 min) exposure to ethanol on release of thromboxane B(2) (TxB(2)) and 6-keto-prostaglandin F(1 alpha) (6-keto-PGF(1 alpha)) at the maternal and fetal sides of the placenta. Thromboxane was increased by both longer and shorter ethanol exposure, especially on the fetal side of the placenta. Prostacyclin was essentially unchanged with exposure to ethanol. The thromboxane:prostacyclin ratio also tended to increase with both 60- and 240-min ethanol exposure, but a statistically significant increase was seen only at a few time points. In the 60-min ethanol exposure, an increase in thromboxane was observed both during and following exposure to ethanol. The increase in the thromboxane milieu observed with ethanol exposure may lead, at least in part, to the IUGR which is frequently associated with FAS. Prevention of this effect of ethanol on thromboxane production might be a beneficial intervention for FAS.

6-Ketoprostaglandin F1 alpha↗