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J Wu

Publications and source records attributed to J Wu.

At least 1,171 records · Page 65Linked to original sources
PubMed1995

The functional hepatic volume assessed by 99mTc-GSA hepatic scintigraphy.

The accuracy of measurement of the functional hepatic volume by single photon emission computed tomography (SPECT) with 99mTc-galactosyl serum albumin (99mTc-GAS) was evaluated. 99mTc-GSA planar scintigraphic images were obtained dynamically and the hepatic SPECT imaging was then performed in 25 patients with hepatobiliary tumors. The patients were divided into 4 groups with normal hepatic function, and mild, moderate and severe hepatic dysfunction. The functional hepatic volume determined by SPECT was compared with the morphological hepatic volume determined by compute tomography. The ratio of the hepatic volumes obtained by the two methods was calculated. The mean hepatic volume ratio was 96.6 +/- 2.3% in the normal hepatic function group and 95.9 +/- 2.2% in the mild dysfunction group (n.s.). In both the moderate and severe hepatic dysfunction groups, the hepatic volume ratio was smaller than that in the normal group (87.9 +/- 5.2%, p < 0.0001, and 71.9 +/- 7.6%, p < 0.0001, respectively). There was a linear correlation between the hepatic volume ration and various indices of reserve hepatic function, such as LHL15 (r = 0.83, p < 0.0001), HH15(r = 0.74, p < 0.0001), and ICG15 (r = 0.75, p < 0.0005). These results indicate that the hepatic volume ratio is proportional to the severity of hepatic dysfunction, and suggest that the functional hepatic volume measured with 99mTc-GSA faithfully reflects the functioning hepatocyte mass. 99mTc-GSA scintigraphy and hepatic SPECT therefore provide information regarding global and regional reserve hepatic function.

Adult↗
PubMed1995

Muramyl dipeptide mimicry in the regulation of murine macrophage activation by serotonin.

Muramyl peptides (MPs) are regulators of macrophage function. That the activities of MPs may be mediated by serotonin (5-HT) is supported by earlier work that demonstrated specific binding sites for MPs on macrophages that competitively bind 5-HT. Both mediators were also shown to enhance the production of superoxide anion (an antibacterial agent) by these cells. We now report on two additional macrophage activation phenomena affected by 5-HT: phagocytosis and induction of tumor necrosis factor alpha (TNF) mRNA. Serotonin acts as a muramyl peptide-like agonist by increasing phagocytosis of tubercle bacilli by murine peritoneal macrophages, and as a partial agonist/antagonist in the induction of mRNA for tumor necrosis factor. These observations provide further evidence for a serotonergic involvement in some of the physiological responses to MPs.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1995

Introduction of a murine p53 mutation corresponding to human codon 249 into a murine hepatocyte cell line results in growth advantage, but not in transformation.

The p53 gene is frequently mutated in human tumors; in hepatocellular carcinomas, there is a high frequency of a specific mutation at codon 249 in regions with significant aflatoxin exposure. To assess the role of this p53 mutation in the development of hepatocellular carcinoma, a mutant murine p53 gene, p53ser246, which corresponds to human codon 249, was transfected into a differentiated, nontransformed hepatocyte cell line AML12. Expression of p53ser246 in this line resulted in a growth advantage when compared with either a control vector (which contains a large p53 deletion) or with a different p53 mutant, val135, not found in hepatocellular carcinoma. Overall, there was a threefold increase in colony formation after transfection with p53ser246 as compared with the control or p53val135 vectors, and the p53ser246 plates developed consistently larger colonies. Whereas clones expressing the control or p53val135 constructs showed no significant morphological changes, clones expressing p53ser246 showed increased heterogeneity (large multinucleated cells and areas of small crowded cells) without focus formation. In addition, the ser246 mutation imparted a growth advantage in serum-free media, suggesting less dependence on specific factors present in serum. None of the mutant p53 or control lines were capable of growth in soft agar or tumor formation in nude mice. Thus in this model, in which endogenous wild-type p53 expression is retained, a high level of mutant p53 expression is not sufficient to transform hepatocytes. Our findings indicate that p53ser246 has effects on hepatocytes that may result in a clonal growth advantage and suggest that additional factors are required for the development of hepatocellular carcinoma.

Animals↗
PubMed1995

Temperature rise generated by diagnostic ultrasound in a transcranial phantom.

Temperature rises generated by diagnostic ultrasound from a modified commercial system (Sonos 1000 Hewlett Packard) in a transcranial phantom that consists of human temporal bone and tissue-mimicking material are measured. Significant temperature rises were found at the external and internal temporal bone surfaces. The experimental results are compared with cranial thermal indices (TIC) developed by the American Institute of Ultrasound in Medicine and the National Electrical Manufacturers Association for various modes. For all the modes compared, TIC underestimated temperature rise at the external temporal bone surface. The differences between the data and temperature rises predicted by TIC can be attributed to transducer surface heating.

Algorithms↗
PubMed1995

Correction of intrinsic spectral broadening errors in Doppler peak velocity measurements made with phased sector and linear array transducers.

Commercial duplex ultrasound systems primarily measure peak velocity of blood flow to provide important information in diagnosing vascular disease. However, due to errors caused by intrinsic spectral broadening (ISB), the accuracy decreases as the Doppler angle increases. In general, vascular technologists and surgeons keep the Doppler angle under 60 degrees. Even at 60 degrees, ISB can produce an overestimation of peak velocity as high as 40%. This would indicate the necessity of reducing the Doppler angle even lower than 60 degrees. Since most vessels in the body run parallel with the skin surface any criteria requiring a Doppler angle of say 45 degrees or less would be difficult to achieve. Using the transverse Doppler equation as a correction for ISB, in conjunction with the classical Doppler equation, accurate peak velocity measurements were obtained at Doppler angles as high as 80 degrees. Corrections were made using both phased sector and linear array transducers for steered and unsteered beams. However, for beams steered at large angles, 20 degrees or more, corresponding to Doppler angles of < 70 degrees, the transverse Doppler equation failed to correct ISB errors in measurements made. This may be due to the experimental setup and not due to limitations in the transverse Doppler equation.

Artifacts↗
PubMed1995

An investigation into the mechanisms by which human dermis does not significantly contribute to the rejection of allo-skin grafts.

The dermis is an important element in skin substitutes and in allo- or xeno-skin grafts. However, the reason(s) why dermis does not significantly induce the immune rejection reaction in vivo remain(s) hitherto unknown. To clarify the mechanisms underlying this phenomenon, we undertook the evaluation of: (i) the response of the peripheral blood mononuclear cells (PBM) to isolated allo-dermal cells or to pieces of or to whole allo-dermis, (ii) the migration and homing of the PBM inside allo-dermis or split thickness allo-skin, (iii) the distribution of the ICAM-1 protein within skin, and (iv) the features expressed by the PBM that migrate into allo-skin. The results herein presented show that (1) the isolated allo-dermal cells had the highest and the whole allo-dermis the lowest capacity to initiate the reactive proliferation of the PBM in vitro; (2) in an allo-skin/PBM co-culture model, most of the PBM slowly, yet preferentially, migrated to and homed inside the allo-epidermal compartment, instead of staying in the allo-dermis; (3) under the conditions employed, rather little ICAM-1 could be immunohistochemically detected within the epidermis, conversely, both the dermal cells and the dermal matrix were ICAM-1 positive; and (4) most of the PBM migrating into the allo-skin pieces expressed either the CD18 or the CD19 or the CD8 molecule, yet very few of them exhibited the LFA-1-antigen, and none of them were found to be CD4 positive.2+Therefore, we conclude that because

Cell Adhesion↗
PubMed1995

Potentiation of N-methyl-D-aspartate-receptor-mediated currents detected using the excised patch technique in the hippocampal dentate gyrus.

The excised patch mode of the patch-clamp technique has been used to record isolated patch N-methyl-D-aspartate-receptor-mediated currents (patch NMDA-receptor-currents) evoked by electrical stimulation in the dentate gyrus of the hippocampal slice. The patch NMDA-receptor-currents were recorded by placing a patch of membrane isolated from the cell body in the inner molecular layer of the dentate gyrus and applying stimulation to the proximal commissural/associational pathway. The patch NMDA-receptor-currents, recorded at +40 mV in the presence of AMPA-receptor and GABAA-receptor antagonists, consisted of two to six summated unitary openings of NMDA-receptor channels, lasting several hundred milliseconds. Tetanic pathway stimulation evoked a rapid increase in the amplitude of the patch NMDA-receptor-currents which lasted for a period of at least 20 min following the tetanus. The study suggests that the potentiation of the patch NMDA-receptor-currents is due to either an increase in transmitter release, or alternatively, to the release of an extracellular messenger which directly enhances NMDA-receptor responsiveness.

Animals↗
PubMed1995

Two-dimensional intravenous coronary arteriography using above-K-edge monochromatic synchrotron X-ray.

RATIONALE AND OBJECTIVES: For intravenous (i.v.) coronary arteriography, a real-time two-dimensional (2D) imaging system is being developed using above-K-edge monochromatic X-rays alone. The potential diagnostic value of this system was examined in the current study. METHODS: The angiographic system consisted of an asymmetric silicon (311) monocrystal, an image intensifier, and a charged-coupled device camera. It was constructed at the beam line of the Tristan Accumulation Ring. Monochromatic X-rays of 33.32 keV were used, and each image was recorded over 2 msec. RESULTS: Ventricular wall motion and the anatomy of the coronary arteries could be seen in dogs by sequential images obtained without subtraction. The left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery and the branches of these vessels were observed. The parts of the coronary arteries overlapping the aorta and left ventricle were revealed somewhat during washout of the contrast material. CONCLUSION: For a 2D imaging system, monochromatic i.v. coronary angiography using an energy above the iodine K-edge might be able to image the coronary arteries without subtraction. However, the image quality needs to be improved by increasing the X-ray flux, decreasing background radiation scatter from the object, and decreasing contamination with 99-keV X-rays.

Animals↗
PubMed1995

Phase-contrast imaging with synchrotron X-rays for detecting cancer lesions.

RATIONALE AND OBJECTIVES: We obtained image contrast in pathologic specimens without the use of contrast material by using phase-contrast imaging with synchrotron X-rays. METHODS: An experiment was performed at the three-pole superconducting vertical wiggler beam line BL-14B at the Photon Factory in Tsukuba, Japan. The X-ray phase-contrast imaging system consisted of a double crystal monochromator, an asymmetrically cut crystal monochromator, a triple Laue-case X-ray interferometer, and film. The pathologic specimen was a sample from human liver that had metastatic carcinoma. RESULTS: The X-ray phase-contrast images of the pathologic specimen clearly depicted the cancerous lesion without the use of contrast enhancement, and the image showed good correlation with the photograph of the specimen. The X-ray absorption image did not differentiate between the normal liver tissue and the tumor. CONCLUSION: The results of this preliminary experiment reveal that for materials such as biologic specimens with a low atomic number, X-ray phase-contrast imaging better differentiates tissues than does the absorption contrast imaging commonly used in radiology.

Humans↗
PubMed1995

Antibodies to a segment of tyrosine hydroxylase phosphorylated at serine 40.

A synthetic peptide corresponding to residues 32-47 of rat tyrosine hydroxylase (TH) was phosphorylated by protein kinase A at Ser40 and used to generate antibodies in rabbits. Reactivity of the anti-pTH32-47 antibodies with phospho- and dephospho-Ser40 forms of TH protein and peptide TH32-47 was compared with reactivity of antibodies to nonphosphorylated peptide and to native TH protein. In antibody-capture ELISAs, anti-pTH32-47 was more reactive with the phospho-TH than with the dephospho-TH forms. Conversely, antibodies against the nonphosphorylated peptide reacted preferentially with the dephospho-TH forms. In western blots, labeling of the approximately 60-kDa TH band by anti-pTH32-47 was readily detectable in lanes containing protein kinase A-phosphorylated native TH at 10-100 ng/lane. In blots of supernatants prepared from striatal synaptosomes, addition of a phosphatase inhibitor was necessary to discern labeling of the TH band with anti-pTH32-47. Similarly, anti-pTH32-47 failed to immunoprecipitate TH activity from supernatants prepared from untreated tissues, whereas prior treatment with either 8-bromoadenosine 3',5'-cyclic monophosphate or forskolin enabled removal of TH activity by anti-pTH32-47. Lastly, in immunohistochemical studies, anti-pTH32-47 selectively labeled catecholaminergic cells in tissue sections from perfusion-fixed rat brain.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Generation and reactions of the disulphide radical anion derived from metallothionein: a pulse radiolytic study.

OH-radicals were generated by pulse radiolysis of aqueous solutions of rabbit (Zn,Cd)-metallothionein (MT). They react with MT mainly by forming a thiyl radical with a rate constant of 1.7 x 10(12) dm3 mol-1 s-1. The thiyl radical reacts rapidly but reversibly with a thiolate function to form RSSR.-: RS + RS- reversible RSSR.-. The kinetics of the formation and decay of this radical anion have been studied pulse radiolytically by monitoring the evolution of the optical absorption of RSSR.- at 450 nm. This process is mostly intermolecular, i.e. bimolecular in MT. In the absence of O2, RSSR.- decays bimolecularly: RSSR.(-)+RS.-->RSSR + RS-. In the presence of O2, RS. may be scavenged by O2 and thus the yield of RSSR.- decreases: RS.+O2 reversible RSOO.. Under these conditions RSSR.- decays by first-order kinetics: RSSR.(-)+O2-->RSSR + O2.-. The rate constants of these reactions have been determined at room temperature: k4 = 1.8 x 10(9) dm3 mol-1 s-1, k5 = 7 x 10(4) s-1, k10 = 9.2 x 10(8) dm3 mol-1 s-1, and k18 about 3 x 10(7) dm3 mol-1 s-1. From the dependence of the maximal absorbance at 450 nm on the thiolate concentration in the absence of oxygen, epsilon (RSSR.-) = 9 x 10(3) dm3 mol-1 cm-1 and the stability constant (K4/5) of 2.3 x 10(4) dm3 ml-1 was determined. K4/5 is in good agreement with that determined kinetically, k4/k5 = 2.6 x 10(4) dm3 mol-1. The stability constant K15/16 of the thiylperoxyl radical, RSOO., was determined to be 5.5 x 10(3) dm3 mol-1.

Animals↗
PubMed1995

Model complexes of tumor necrosis factor-alpha with receptors R1 and R2.

The biological activities of tumor necrosis factor-alpha (TNF-alpha) are mediated by two different receptors, TNFR1 and TNFR2. To analyze the receptor binding site(s) of TNF-alpha, molecular models have been built of the complexes of TNF-alpha with the extracellular regions of receptors R1 and R2, based on the known crystal structures of TNF-alpha and lymphotoxin bound to R1. The model structure of R2 from residues 18-160 was built by analogy to the crystal structure of R1 in complex with lymphotoxin. The amino acid sequences of R1 and R2 show 27.5% identity over this region and were aligned with five insertions and three deletions. There are 18 conserved cysteines that form disulfides. R2 has lost one pair of cysteines compared with R1, but two new cysteines were modeled as forming a new disulfide bond. Both symmetric and asymmetric trimers of TNF-alpha were used to model the complexes with TNFR1 and R2. An analysis of differences in the model complexes showed good agreement with data on the differential binding of TNF mutants to its two receptors.

Amino Acid Sequence↗
PubMed1995

Localized and lateralized cerebral glucose metabolism associated with eye movements during REM sleep and wakefulness: a positron emission tomography (PET) study.

In order to study the neural substrate for eye movements during rapid eye movement (REM) sleep, we analyzed the positron emission tomography (18Fluorodeoxyglucose positron emission tomography) scan data obtained from normal subjects. Eye movement data were available on nine subjects studied during nighttime REM sleep and six control subjects studied during waking as they periodically moved their eyes. The number of eye movements during REM sleep was positively correlated with glucose metabolic rate in the areas corresponding to (a) the saccadic eye movement system (frontal eye field and dorsolateral prefrontal cortex, statistically significant only on the right side), (b) the midline attentional system (cingulate and medial frontal cortex, precuneus) and (c) the parietal visual spatial attentional system (bilateral superior parietal lobules, right inferior parietal lobule); and negatively correlated with relative metabolic rate in the left inferior parietal lobule. Positive correlations between waking eye movements and metabolic rate were observed in the same areas except inferior parietal lobule. Our results show that the same cortical areas are involved in eye movements in both REM sleep and wakefulness and suggest that REM sleep eye movements are saccadic scans of targets in the dream scene. Our data also suggest right hemispheric specialization in saccadic eye movement control and reciprocal inhibition in the contralateral homologous area during higher cortical functioning.

Attention↗
PubMed1995

Identification and characterization of a novel synthetic peptide substrate specific for Src-family protein tyrosine kinases.

Using a random combinatorial peptide library method [Wu, J., Ma, Q. N. & Lam, K. S. (1994) Biochemistry 33, 14825-14833] a novel peptide, YIYGSFK, was identified as a substrate for p60c-src protein tyrosine kinase. Mass spectrometric analysis showed that tyrosine-3 from the N-terminus was the phosphorylation site. Kinetic studies showed that the Km of YIYGSFK for p60c-src was 55 microM, about 6.4-fold lower than a peptide derived from p34cdc2 [cdc2(6-20), KVEKIGEGTYGVVYK], which had been reported to be a specific and efficient substrate for the Src-family protein tyrosine kinases. Comparison of the specificity of YIYGSFK and cdc2(6-20) as a substrate for various Src-family and non-Src-family protein tyrosine kinases suggests that YIYGSFK is a much more specific and efficient substrate for the Src-family protein tyrosine kinases.

Amino Acid Sequence↗
PubMed1995

Expression, purification, and characterization of a novel G protein, SGP, from Streptococcus mutans.

The sgp gene of Streptococcus mutans was recently detected immediately downstream from the dgk gene within the same operon. In this study, the sgp gene was subcloned into the pMAL-c2 vector and SGP (S. mutans G protein) was overexpressed in Escherichia coli as a fusion protein with the maltose-binding protein at a level of 40% of total cellular protein. One-step amylose affinity chromatography purification of this fusion protein yielded a product of approximately 95% purity. SGP was purified from this fusion protein following cleavage with protease factor Xa and DEAE-Sephacel chromatography. In nucleotide binding assays, recombinant SGP showed specific binding for GTP and GDP, but not ATP, CTP, and UTP, and also catalyzed efficient hydrolysis of GTP to GDP. Kinetic studies revealed that the SGP Km value for GTP in this reaction was approximately 5.9 microM. Mg2+ also served as a cofactor of SGP in this reaction. In vivo subcellular localization by immunogold labelling demonstrated that SGP was associated with both membrane and cytoplasmic fractions. SGP not only had structural similarities with other G proteins but also proved to have high-level intrinsic GTPase activity. Therefore, SGP appears to be a new member of the G protein superfamily and may participate in transmembrane signaling in the responses of S. mutans cells to environmental stimuli.

Bacterial Proteins↗
PubMed1995

Global regulation of a sigma 54-dependent flagellar gene family in Caulobacter crescentus by the transcriptional activator FlbD.

Biosynthesis of the Caulobacter crescentus polar flagellum requires the expression of a large number of flagellar (fla) genes that are organized in a regulatory hierarchy of four classes (I to IV). The timing of fla gene expression in the cell cycle is determined by specialized forms of RNA polymerase and the appearance and/or activation of regulatory proteins. Here we report an investigation of the role of the C. crescentus transcriptional regulatory protein FlbD in the activation of sigma 54-dependent class III and class IV fla genes of the hierarchy by reconstituting transcription from these promoters in vitro. Our results demonstrate that transcription from promoters of the class III genes flbG, flgF, and flgI and the class IV gene fliK by Escherichia coli E sigma 54 is activated by FlbD or the mutant protein FlbDS140F (where S140F denotes an S-to-F mutation at position 140), which we show here has a higher potential for transcriptional activation. In vitro studies of the flbG promoter have shown previously that transcriptional activation by the FlbD protein requires ftr (ftr for flagellar transcription regulation) sequence elements. We have now identified multiple ftr sequences that are conserved in both sequence and spatial architecture in all known class III and class IV promoters. These newly identified ftr elements are positioned ca. 100 bp from the transcription start sites of each sigma 54-dependent fla gene promoter, and our studies indicate that they play an important role in controlling the levels of transcription from different class III and class IV promoters. We have also used mutational analysis to show that the ftr sequences are required for full activation by the FlbD protein both in vitro and in vivo. Thus, our results suggest that FlbD, which is encoded by the class II flbD gene, is a global regulator that activates the cell cycle-regulated transcription from all identified sigma 54-dependent promoters in the C. crescentus fla gene hierarchy.

Bacterial Proteins↗