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Biomedical subjects

X Hu

Publications and source records attributed to X Hu.

At least 307 records · Page 17Linked to original sources
PubMed1997

Morphologic pattern of tenascin as a diagnostic biomarker in colon cancer.

BACKGROUND: Immunohistochemical methods were used to study the pattern of expression of tenascin (TN) in invasive colon cancer and its relation to prognosis. METHODS: Sixty patients (29 males, 31 females) with a mean age of 77 years were studied. TN expression was evaluated by immunohistochemistry using paraffin-embedded tissue sections, TN expression levels were correlated with patient age, tumor stage, and survival. RESULTS: TN positivity varied from trace to 4+. Staining patterns were as follows: in well-differentiated cancer, TN fibers form thick bands around invading tumor glands. In poorly differentiated cancer, TN fibers had an interstitial pattern surrounding individual tumor cells. Using Cox's proportional hazard regression method, survival was significantly related to TN score (P < 0.0001) and stage of disease (P < 0.05). No significant relationship was found between survival and age (P = 0.375). CONCLUSION: Patients with more TN expression had better long-term survival than patients with no or weak TN expression. Pathologic and clinical entities in colon cancer have distinct immunohistochemical TN matrix patterns that may correlate with predictive value and long-term survival.

Adenocarcinoma↗
PubMed1997

The nature of spatiotemporal changes in cerebral hemodynamics as manifested in functional magnetic resonance imaging.

The nature of changes in rapidly acquired magnetic resonance images of the brain was studied by using a denoising method and spectral techniques optimally suited to short time series. It was found that the stimulus related changes have a complex spatiotemporal structure even for simple visual stimuli. Apart from a low frequency window, the non-stimulus-related changes were found to correspond in detail to either breathing or heartbeat, although these two sources show different patterns of spatial coherence in the image. At low frequencies, oscillations with frequencies around 0.1 Hz were observed, also with nontrivial space-time structure, which are likely to be vasomotor in origin.

Blood Vessels↗
PubMed1997

Evaluation of the early response in fMRI in individual subjects using short stimulus duration.

Optical imaging studies have provided evidence of an initial increase in deoxyhemoglobin following the onset of neuronal stimulation/activation and demonstrated that this initial increase could be spatially more specific to the site of neuronal activity. These studies also raised the possibility of improving the specificity of fMRI by selective mapping of this early response. Previous MR studies reported the observation of this early response but were limited in scope and not in full agreement. This paper presents a more extensive study that (a) demonstrates the initial signal decrease in individual subjects and (b) examines its dependence on stimulus duration and subject. Binocular visual stimulation experiments were performed on 14 subjects using echo-planar imaging (EPI) with high temporal resolution. An initial signal decrease was consistently observed in regions that were more localized than those displaying the delayed positive response. In agreement with previous fMRI and optical imaging findings, the maximum signal decrease was 1-2% and occurred at approximately 2 s after the onset of the stimulus, depending on the subject. For stimulus longer then 3.0 s, the temporal dynamics and the amount of signal change of the early response was essentially independent of the stimulus duration, while the delayed response and the post-stimulus undershoot increased both in terms of magnitude and rise time as the duration of the stimulus increased; this observation is concordant with the recent optical imaging study.

Brain↗
PubMed1997

Simulated phase evolution rewinding (SPHERE): a technique for reducing B0 inhomogeneity effects in MR images.

A novel method for reducing field inhomogeneity effects in magnetic resonance images is described in this paper. Observing that image degradation arises from B0 inhomogeneity-induced phase accrual during data acquisition, the present method numerically rewinds the accumulated phase in the k-space data based on an initial estimate of the image and a corresponding field map. The rewinding process generates a corrected k-space data set that is subsequently Fourier transformed to produce the final image. In this paper, a theoretical analysis of the method and applications of the technique to magnetic resonance imaging data are presented. The theoretical analysis of the method indicates that it is a general approach applicable to a variety of sequences. Results obtained by applying the method to experimental data acquired with single-shot echo-planar imaging, segmented echo-planar imaging with centric reordering, and spiral sequences demonstrate that it is robust in reducing image degradation induced by B0 inhomogeneity.

Brain↗
PubMed1997

The effect of levobunolol hydrochloride on the calcium and potassium channels in isolated ventricular myocytes of guinea pig.

The effects of levobunolol hydrochlorid (Bun) on the type L calcium channel currents (ICA) and delayed rectifier potassium channel currents (IK) in isolated ventricular myocytes of guinea pig were studied by using patch clamp whole cell recording techniques. The results were showed that: 1) Bun caused a dose dependent decrease in ICA and a dose-dependent increase in IK of the ventricular myocytes. The threshold concentrations of Bun for ICA and IK were 10(-8) mol/L and 10(-7) mol/L respectively. The maximum effective concentration of Bun for bot ICA and IK was 3x10(-5) mol/L, and half-maximal concentration was 3x10(-6) mol/L; 2) IK was blocked by 2x100(-6) mol/L tetraethylammonium (TEA). A concentration of 3x10(-6) mol/L Bun showed a decreasing effect on the ICA as revealed by the current-voltage relationship curve, i.e., Bun caused an elevation of the curve;3) When ICA was blocked by 2x10(-6) mol/L Isoptin (Verapamil), at a concentration of 3x10(-6) mol/L Bun showed an increasing effect on IK and the effect could be blocked by TEA. The above-mentioned results indicated that Bun had an inhibitory effect on ICA and a fascilitatory effect on IK. The results suggested that the molecular mechanisms of antihypertensive, heart rate slowing the beta -receptor blocking effects of Bun might be due to decrease of ICA and increase of IK.

Adrenergic beta-Antagonists↗
PubMed1997

Thrombospondin-1 and transforming growth factor-beta l promote breast tumor cell invasion through up-regulation of the plasminogen/plasmin system.

BACKGROUND: Pericellular proteolysis is crucial in tumor cell invasion. The plasminogen/plasmin system is one of the main protease systems involved in cancer progression. Thrombospondin-1 (TSP-1), through activation of transforming growth factor-beta 1 (TGF-beta 1), up-regulates the main plasminogen activator, the urokinase-type plasminogen activator (uPA). The objectives of this study were to determine the role of TSP-1 and TGF-beta 1 in the localization of the plasminogen/plasmin system to the tumor cell surface by the uPA receptor (uPAR) and to determine its effect in breast tumor cell invasion. METHODS: The effect of TSP-1 and TGF-beta 1 in uPAR expression was determined in MDA-MB-231 human breast cancer cells by enzyme-linked immunosorbent assay and Western blot analysis. Their effect and the role of the plasminogen/plasmin system in breast tumor cell invasion were studied with a Boyden Chamber assay. RESULTS: uPAR expression was up-regulated more than twofold by both TSP-1 and TGF-beta 1. The effect of TSP-1 involved its receptor and the activation of TGF-beta 1 by TSP-1. Breast tumor cell invasion was up-regulated sevenfold to eightfold by both TSP-1 and TGF-beta 1 compared with the control group. Antibodies against uPA or uPAR neutralized the TSP-1- and TGF-beta 1-promoted breast tumor cell invasion. CONCLUSIONS: TSP-1, through the activation of endogenous TGF-beta 1, up-regulates the plasminogen/plasmin system and promotes tumor cell invasion in breast cancer cells.

Breast Neoplasms↗
PubMed1997

Three-dimensional vascular reconstruction with a clinical x-ray angiography system.

RATIONALE AND OBJECTIVES: The authors developed a technique to produce high-resolution, three-dimensional images of vasculature from a set of x-ray projections in an attempt to provide detailed anatomic representations of complex vasculature. MATERIALS AND METHODS: Projection images were acquired with a clinical angiographic system by using biplanar rotational digital subtraction angiography. The images were reconstructed with an additive algebraic reconstruction technique. RESULTS: The feasibility of the technique was tested by reconstructing three-dimensional images of several phantoms, including a wire phantom and an anatomic flow phantom. The anatomic phantom allowed replication of contrast material flow and image noise that are characteristic of patient examinations. The reconstruction procedure was then used to examine a carotid artery and a cerebral aneurysm in two patients. CONCLUSION: A method of reconstructing vasculature from x-ray angiograms has been developed and validated with geometric and anatomic phantoms. Preliminary patient applications indicate that this technique enables enhanced visualization of complex vascular relationships and structures.

Angiography, Digital Subtraction↗
PubMed1997

Cloning and expression of a PR5-like protein from Arabidopsis: inhibition of fungal growth by bacterially expressed protein.

Pathogenesis-related (PR)-5 proteins are a family of proteins that are induced by different phytopathogens in many plants and share significant sequence similarity with thaumatin. We isolated a complementary DNA (ATLP-3) encoding a PR5-like protein from Arabidopsis which is distinct from two other previously reported PR5 cDNAs from the same plant species. The predicted ATLP-3 protein with its amino-terminal signal sequence is 245 amino acids in length and is acidic with a pl of 4.8. The deduced amino acid sequence of ATLP-3 shows significant sequence similarity with PR5 and thaumatin-like proteins from Arabidopsis and other plants and contains a putative signal sequence at the amino-terminus. The expression of ATLP-3 and a related gene (ATLP-1) that we previously isolated from Arabidopsis was induced by pathogen infection and salicylic acid, a known inducer of pathogenesis-related genes. Southern blot analysis indicates that the ATLP-1 and ATLP-3 are coded by single-copy genes. To study the effect of ATLP-1 and ATLP-3 proteins on fungal growth, the cDNA regions corresponding to putative mature protein were expressed in Escherichia coli and the cDNA encoded proteins were purified. ATLP-1 and ATLP-3 proteins cross-reacted with anti-osmotin and anti-zeamatin antibodies. ATLP-3 protein showed antifungal activity against several fungal pathogens suggesting that ATLP-3 may be involved in plant defense against fungal pathogens.

Amino Acid Sequence↗
PubMed1997

Characterization of a BMS-181174-resistant human bladder cancer cell line.

This study was undertaken to elucidate the mechanism of cellular resistance to BMS-181174, a novel analogue of mitomycin C (MMC), in a human bladder cancer cell line. The BMS-181174-resistant variant (J82/BMS) was established by repeated continuous exposures of parental cells (J82) to increasing concentrations of BMS-181174 (9-40 nM) over a period of about 17 months. A 2.6-fold higher concentration of BMS-181174 was required to kill 50% of J82/BMS cell line compared with J82. The J82/BMS cell line exhibited collateral sensitivity to 5-fluorouracil (5-FU), but was significantly more cross-resistant to MMC, melphalan, taxol, doxorubicin and VP-16. NADPH cytochrome P450 reductase and DT-diaphorase activities, which have been implicated in bioreductive activation of MMC, were significantly lower in the J82/BMS cell line than in J82. The cytotoxicity of BMS-181174, however, was not affected in either cell line by pretreatment with dicoumarol, which is an inhibitor of DT-diaphorase activity. These results argue against a role of DT-diaphorase in cellular bioactivation of BMS-181174, a conclusion consistent with that of Rockwell et al (Biochem Pharmacol, 50: 1239-1243, 1995). BMS-181174-induced DNA interstrand cross-link (DNA-ISC) frequency was markedly lower in J82/BMS cell line than in J82 at every drug concentration tested. The results of the present study suggest that cellular resistance to BMS-181174 in J82/BMS cell line may be due to reduced DNA-ISC formation. However, the mechanism of relatively lower BMS-181174 induced DNA-ISC formation in J82/BMS cell line than in parental cells remains to be clarified.

Antineoplastic Agents, Alkylating↗
PubMed1997

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.

A putative yeast sn-2 acyltransferase gene (SLC1-1), reportedly a variant acyltransferase that suppresses a genetic defect in sphingolipid long-chain base biosynthesis, has been expressed in a yeast SLC deletion strain. The SLC1-1 gene product was shown in vitro to encode an sn-2 acyltransferase capable of acylating sn-1 oleoyl-lysophosphatidic acid, using a range of acyl-CoA thioesters, including 18:1-, 22:1-, and 24:0-CoAs. The SLC1-1 gene was introduced into Arabidopsis and a high erucic acid-containing Brassica napus cv Hero under the control of a constitutive (tandem cauliflower mosaic virus 35S) promoter. The resulting transgenic plants showed substantial increases of 8 to 48% in seed oil content (expressed on the basis of seed dry weight) and increases in both overall proportions and amounts of very-long-chain fatty acids in seed triacylglycerols (TAGs). Furthermore, the proportion of very-long-chain fatty acids found at the sn-2 position of TAGs was increased, and homogenates prepared from developing seeds of transformed plants exhibited elevated lysophosphatidic acid acyltransferase (EC 2.3.1.51) activity. Thus, the yeast sn-2 acyltransferase has been shown to encode a protein that can exhibit lysophosphatidic acid acyltransferase activity and that can be used to change total fatty acid content and composition as well as to alter the stereospecific acyl distribution of fatty acids in seed TAGs.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1997

Pseudo-Fourier imaging (PFI): a technique for spatial encoding in MRI.

In magnetic resonance imaging (MRI), spatial discrimination is usually achieved with selective excitation and/or Fourier encoding. While these approaches are favorable in most situations, it is sometimes desirable to have an approach that takes advantage of both selective excitation and Fourier encoding. In this paper, we describe the theory and experimental results of a new technique, which we will call pseudo-Fourier imaging (PFI), that provides a flexible combination of both approaches. The technique is based on a windowed Fourier transform that expands the continuous object spatial distribution in terms of coherent states. A detailed description of the proposed technique is presented in this paper. The practical implementation of this technique is described and shown to be achieveable using a set of selective excitations combined with a number of Fourier encoding steps. Then, the signal-to-noise ratio of the new technique is derived to show that it can be varied at will anywhere in the range between the ratios for selective excitation and Fourier encoding. Finally, the experimental results of implementing the technique are presented and some potential applications of the technique such as volume imaging, dynamic imaging and magnetic resonance angiography are discussed.

Fourier Analysis↗
PubMed1997

Molecular typing of Staphylococcus epidermidis and other CNS with repetitive element sequence-based PCR.

The chromosomal distribution of the repetitive DNA sequence found in Mycoplasma pneumoniae (REP-MP2) provides an ideal target for detecting DNA fragment patterns specific to individual Staphylococcus epidermidis and S. haemolyticus strains. A REP-MP2 sequence-based PCR (rep-PCR) was developed and applied to CNS isolates. We identified a 450 bp genomic DNA fragment which was common and specific to S. epidermidis isolates and not found in other CNS. In addition, S. epidermidis isolates showed several bands that could be grouped into 14 different fragment patterns. Similarly, S. haemolyticus isolates were classified into 10 groups. Significant correlations between the typing patterns of S. epidermidis and resistance to oxacillin (P< 0.05), gentamicin (P< 0.01), erythromycin (P< 0.02), and sulfamethoxazole-trimethoprim (P< 0.001) were found. The rep-PCR method is a rapid and reproducible discriminatory means for molecular typing of S. epidermidis and other CNS.

Anti-Bacterial Agents↗
PubMed1997

Association of the parainfluenza virus fusion and hemagglutinin-neuraminidase glycoproteins on cell surfaces.

We previously observed that cell fusion caused by human parainfluenza virus type 2 or type 3 requires the expression of both the fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins from the same virus type, indicating that a type-specific interaction between F and HN is needed for the induction of cell fusion. In the present study we have further investigated the fusion properties of F and HN proteins of parainfluenza virus type 1 (PI1), type 2 (PI2), and type 3 (PI3), Sendai virus (SN), and simian virus 5 (SV5) by expression of their glycoprotein genes in HeLa T4 cells using the vaccinia virus-T7 transient expression system. Consistent with previous results, cell fusion was observed in cells transfected with homotypic F/HN proteins; with one exception, coexpression of any combination of F and HN proteins from different viruses did not result in cell fusion. The only exception was found with the closely related PI1 HN and SN HN glycoproteins, either of which could interact with SN F to induce cell fusion upon coexpression as previously reported. By specific labeling and coprecipitation of proteins expressed on the cell surface, we observed that anti-PI2 HN antiserum coprecipitated PI2 F when the homotypic PI2 F and PI2 HN were coexpressed, but not the F proteins of other paramyxoviruses when heterotypic F genes were coexpressed with PI2 HN, suggesting that the homotypic F and HN proteins are physically associated with each other on cell surfaces. Furthermore, we observed that PI3 F was found to cocap with PI3 HN but not with PI2 HN, also indicating a specific association between the homotypic proteins. These results indicate that the homotypic F and HN glycoproteins are physically associated with each other on the cell surface and suggest that such association is crucial to cell fusion induced by paramyxoviruses.

Animals↗
PubMed1997

A 120 kilobase resolution contig map of the rice genome.

92% of the rice genome (4.3 x 10(8) bp, 2n = 24) was covered by 631 contigs of various length, which were generated by fingerprinting from a representative and genetically stable bacterial artificial chromosome (BAC) library of the Guang Lu Ai 4 (a O. Sativa variety) genome with the average insert of 120 kb in length. To form the contig map, 565 molecular markers of RFLP, STS, cDNA and anchor set derived from two O. Sativa varieties were by colony hybridization mapped to the contigs, which were then assigned to and ordered along the particular chromosomes according to the marker colinearity. Being highly conserved DNA sequences shared among the genomes of rice, barley, wheat, oat, maize, sorghum and sugar cane, 89 anchor markers mapped help to identify the rice genes through the information provided by the maps of relative genomes, and vice versa. Numerous repeated DNA sequences of various length were identified and mapped to the chromosomes. Physical distances have been determined for hundreds pairs of adjacent markers, which would facilitate the identification by map-based cloning the rice genes of interest. The accuracy of clone overlaps in contigs was further confirmed by the existence in contigs of well fit stacks of marker-lodged clones independently identified by hybridization. Large scale DNA sequencing of individual chromosomes could now be initiated simply by selecting and sequencing the minimally overlapped BAC clones of the contigs.

Alkyl and Aryl Transferases↗
PubMed1997

[Studies on aging enzyme activities of the human dental pulp blood vessels].

Histochemical distribution and age changes of alkaline phosphatase (AKPase E. C. 3. 1. 3. 1) and adenosine triphosphatase (ATPase E. C. 3. 6. 1. 3) in normal human dental pulp blood were investigated qualitatively and quantitatively. 42 dental pulp samples from patients aged 10 to 70 years old were divided into three groups. Results showed that accompanying aging, activities of AKPase and ATPase of dental pulp blood vessels decreased. AKPase staining quantities for group one (10-30 years), group two (31-50 years) and group three (51-70 years) were 40.62 +/- 13.79, 36.75 +/- 9.78 and 19.20 +/- 5.35 and ATPase staining quantities were 33.00 +/- 10.09, 27.53 +/- 16.60 and 23.27 +/- 5.04 respectively. The endothelial cells of capillaries in dental pulp changed greatly. With aging, metabolic ability of dental pulp decreased gradually. In addition, it was observed that the capillaries in sub-odontoblasts decreased and odontoblast layer became thin with aging. The close association of the capillaries of the pulp to the odontoblasts had been demonstrated.

Adenosine Triphosphatases↗
PubMed1997

[Electron spin resonance studies of the oxidative denaturation of hemoglobin of blood preserved at 35 degrees C].

Studying the denaturation of oxidative hemoglobin of blood preserved at room temperature, it is helpful to overall understand erythrocyte injurious during blood preserved at room temperature. Using electron spin resonance technique, we have researched the denaturation of oxidative hemoglobin of blood preserved at 35 degrees C. We discovered that blood preserved at 35 degrees C, appears ESR absorption of high spin methemoglobin (g = 6) after preservation time is 36 hours. The high spin methemoglobin ESF absorption will increase when preservation time increases. When blood is preserved at 4 degrees C, it dose not emerge ESR absorption during 60 hours preservation. SOD activity will gradually decline in erythrocyte of blood preserved at 35 degrees C when preservation time increases. Oxidative denaturation of hemoglobin is probably caused with gradual declining of antioxidation system effect in erythrocyte.

Adult↗