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Biomedical subjects

Y Yang

Publications and source records attributed to Y Yang.

At least 739 records · Page 41Linked to original sources
PubMed1998

Analysis of variant forms of porcine surfactant polypeptide-C by nano-electrospray mass spectrometry.

Electrospray (ES) mass spectrometry has been used to analyse preparations of porcine pulmonary surfactant polypeptide-C (SP-C). A number of variant forms of the native 35-residue dipalmitoylated peptide were detected including (a) C-terminally methylated SP-C, (b) C-terminally methylated and methionine oxidized SP-C, (c) N-terminally truncated, C-terminally methylated and methionine oxidized SP-c, (d) C-terminally elongated, C-terminally methylated and methionine oxidized SP-C, and (e) tripalmitoylated, C-terminally methylated and methionine oxidized SP-C. C-terminal methylation and methionine oxidation are probably a consequence of the sample handling procedure. The occurrence of the C-terminally elongated form of SP-C has implications for the in vivo processing of proSP-C and the Tandem mass spectrometry (MS/MS) was used to confirm the amino acid sequence of SP-C and the presence of palmitoyl groups covalently linked to the peptide. Some of the structures of the variant forms of SP-C were determined by MS/MS.

Amino Acid Sequence↗
PubMed1998

LPAM-1 (integrin alpha 4 beta 7)-ligand binding: overlapping binding sites recognizing VCAM-1, MAdCAM-1 and CS-1 are blocked by fibrinogen, a fibronectin-like polymer and RGD-like cyclic peptides.

The alpha 4 integrin LPAM-1 (alpha 4 beta 7) mediates lymphocyte attachment within the extracellular matrix (ECM) by adhering to the connecting segment (CS)-1 site of fibronectin (FN). Here we reveal that very late antigen (VLA)-4 LPAM-1+ T cell lymphoma TK-1 cells bind via LPAM-1 to multiple copies of the RGD sequence engineered within an FN-like polymer. Further, the small conformationally restrained RGD-like cyclic peptides 1-adamantaneacetyl-Cys-Gly-Arg-Gly-Asp-Ser-Pro-Cys and Arg-Cys-Asp-thioproline-Cys inhibit the adhesion of TK-1 cells to immobilized CS-1 peptide, and to endothelial counterreceptors for LPAM-1, namely mucosal addressin cell adhesion molecule (MAdCAM)-1 and vascular cell adhesion molecule (VCAM)-1. Spontaneous adhesion of the VLA-4- LPAM-1+ B lymphoma cell line RPMI 8866 to CS-1 was likewise inhibited, confirming a previously undocumented ability of LPAM-1 to recognize the RGD tripeptide. The RGD-binding site in LPAM-1 either overlaps or is identical to sites required for interaction with MAdCAM-1, VCAM-1, and the CS-1. The binding of LPAM-1 and VLA-4 to RGD-containing ligands may have relevance in vivo given that fibrinogen at physiological concentrations is able to partially block the binding of TK-1 cells to MAdCAM-1. Hence fibrinogen and other vascular RGD-containing proteins may have mild anti-inflammatory activity required for maintaining effective homeostasis, analogous to the anti-thrombogenic activity of the vascular endothelium.

Amino Acid Sequence↗
PubMed1998

MAdCAM-1 costimulates T cell proliferation exclusively through integrin alpha4beta7, whereas VCAM-1 and CS-1 peptide use alpha4beta1: evidence for "remote" costimulation and induction of hyperresponsiveness to B7 molecules.

We have analyzed the effects of the alpha4 integrin ligands mucosal addressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1), and the fibronectin CS-1 splice variant on T cell activation. Immobilized MAdCAM-1 and VCAM-1 IgG-Fc chimeras and a fibronectin CS-1 peptide efficiently costimulate T cell proliferation when antigen presentation is mimicked by anti-CD3 antibody. VCAM-1-Fc and fibronectin CS-1, which are adhesive ligands for both the alpha4beta1 and alpha4beta7 integrins, medicate T cell costimulation exclusively through integrin alpha4beta1, but not through alpha4beta7. The inability of VCAM-1-Fc to costimulate via alpha4beta7 suggests that cell adhesion per se is insufficient, and that exquisite recognition and activation events must be triggered. MAdCAM-1-Fc mediates costimulation exclusively via alpha4beta7, and can both synergize with and induce hyperresponsiveness to the classical costimulator B7-2. MAdCAM-1-Fc and VCAM-1-Fc, but not B7-2, effectively costimulate when immobilized on sites spatially distant from the anti-CD3 antibody ("remote" costimulation). In vitro, the relative potencies of the CAM were VCAM-1-Fc> ICAM-1-Fc> MAdCAM-1-Fc > B7-Fc, except at high concentrations where ICAM-1 was the most potent. Features of costimulatory CAM revealed by this study have important implications for the design of immunotherapeutic vaccine strategies to combat cancer and infection.

Abatacept↗
PubMed1998

A comparison of fast MR scan techniques for cerebral activation studies at 1.5 tesla.

To evaluate the sensitivity of fast, gradient-echo MR scan techniques in their ability to detect blood oxygenation level dependent (BOLD) signal changes in task activation studies, three dedicated fast scan techniques, each with whole-brain coverage, were compared during a 3-min finger tapping paradigm on nine normal volunteers on a clinical 1.5 T scanner. Multislice (2D) single-shot spiral, 3D spiral, and multislice (2D) single-shot EPI scan techniques were done with similar temporal and spatial resolutions on each of the volunteers in random order. After image registration and statistical analysis, the sensitivity to detect activation was evaluated for the techniques by calculating t scores and number of activated voxels in predetermined regions of interest, including the contralateral primary sensorimotor cortex, the premotor region, the parietal region, the supplementary motor area, and the ipsilateral cerebellum. Baseline images acquired with the three techniques were qualitatively comparable and had a similar effective spatial resolution of around 5 x 5 x 5 mm3, as determined from autocorrelation analysis. The anatomical coverage was somewhat reduced (4 less slices per volume) with EPI at the identical temporal resolution of 1.76 s for all techniques. The use of multislice 2D spiral scan for motor cortex fMRI experiments provided for a superior overall temporal stability, and an increased sensitivity compared with multislice 2D EPI, and 3D spiral scan. The difference in sensitivity between multislice 2D spiral and EPI scans was small, in particular in the case of a ramp-sampled version of EPI. The difference in performance is attributed mainly to the difference in scan-to-scan stability.

Brain↗
PubMed1998

Multislice imaging of quantitative cerebral perfusion with pulsed arterial spin labeling.

A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.

Artifacts↗
PubMed1998

Trapping of intermediates during the refolding of recombinant human epidermal growth factor (hEGF) by cyanylation, and subsequent structural elucidation by mass spectrometry.

Human epidermal growth factor (hEGF) contains 53 amino acids and three disulfide bonds. The unfolded, reduced hEGF is allowed to refold under mildly alkaline conditions. The folding is quenched at different time points by adjusting the pH to 3.0 with an acetic acid solution of 1-cyano-4-dimethylamino-pyridinium (CDAP) which traps folding intermediates via cyanylation of free sulfhydryl groups. The mixture of cyanylated intermediates is separated by reversed-phase HPLC; the fractions collected are identified by mass spectrometry. The disulfide structures of the intermediates are then determined by specific chemical cleavage and mass-mapping by MALDI-MS, a novel approach developed in our laboratory. The procedure of quenching and trapping of disulfide intermediates in acidic solution minimizes sulfhydryl-disulfide exchange, and therefore provides a good measure of folding kinetics and preservation of intermediate species. Our cyanylation methodology for disulfide mapping is simpler, faster, and more sensitive than the more conventional approach. Among 18 folding intermediates isolated and identified at different time points, disulfide structures of seven well-populated intermediates, including two non-native isomers with scrambled disulfide structures, one 2-disulfide intermediate, and four 1-disulfide intermediates, have been characterized; most of them possess non-native disulfide structures.

Amino Acid Sequence↗
PubMed1998

Interleukins 4 and 13 upregulate expression of cd44 in human colonic epithelial cell lines.

Interleukin 4 (IL-4) inhibits carcinoma cell growth and promotes expression of differentiation-associated products by normal and malignant epithelial cells. The effects of IL-4 and IL-13 on expression of the CD44 transmembrane adhesion receptor were examined in human epithelial cell lines of colonic (HT-29, CaCo-2, DLD-1, T84), breast (MCF-7, ZR75-1) and liver (Hep-G2, PLC/PRF/5) origins as well as mitogen-activated and resting peripheral blood lymphocytes (PBL) and T cell lines (Jurkat, HUT78). Liver and Jurkat cells were negative for CD44. Colonic, breast and HUT78 cells expressed CD44 constitutively and all except DLD-1 and HUT78 also expressed CD44 splice variant (CD44v) epitopes. All cell lines expressed IL-4 receptors, but IL-4 and IL-13 induced upregulation of CD44 only in the colonic cell lines. CD44v was also upregulated, but there was no de novo induction of CD44v in variant-negative cells and no de novo expression of CD44 in the CD44(-) lines. CD44 upregulation in mitogen-activated PBL was not increased by IL-4 and IL-13 and was not inhibited by neutralizing antibodies. Other cytokines tested [interferon gamma (IFN-gamma, tumour necrosis factor alpha (TNF-alpha), transforming growth factor beta1 (TGF-beta1) and IL-6] did not affect CD44 core epitope expression in the cell lines tested.

Alternative Splicing↗
PubMed1998

The effect of photochemical stress upon the lenses of normal and glutathione peroxidase-1 knockout mice.

This communication investigates the effect of oxidative stress upon the lenses of young normal and glutathione peroxidase-1 (GSHPx-1) Knockout mice. Both normal and knockout lenses have similar biochemical and morpholigical characteristics and the elimination of GSHPx-1 only decreases slightly the ability of the lens to degrade H2O2. Examination of the effect of a 4 hr photochemical stress on morphological characteristics indicates that there is comparable damage in the normal and knockout lenses in the epithelial and bow regions while the posterior region remains normal. However, at 24 hrs post-insult, the normal lenses appear to recover somewhat in the bow region while the knockout bow and posterior regions have extensive damage. In contrast to the morphological data, the biochemical parameters (14C)choline transport and (3H)thymidine incorporation are affected to a somewhat greater extent in the knockout lenses than in normal lenses. While both of these parameters are further affected in the 24 hr post-insult period, there is no further change in the relative effects upon normal and knockout lenses. Non-protein thiol is affected in a similar manner in both lens types. The effect upon biochemical parameters of tertiary butyl hydroperoxide (TBHP) insult was similar to H2O2 and photochemical stress. The overall conclusion is that young GSHPx-1 knockout lenses handle oxidative stress somewhat less effectively than comparable normal lenses but non-stressed knockout lenses appear normal. These results differ from observations reported by Reddy et al. (1997) under somewhat different conditions.

Animals↗
PubMed1998

The effect of catalase amplification on immortal lens epithelial cell lines.

Utilizing a human beta-actin promoter, a catalase cDNA expression vector was constructed. This construct was used to transfect two immortal cell lines, mouse alpha TN4-1 and rabbit N/N 1003A. The catalase activity was increased about 3.4 fold in the alpha TN4-1 cells and 38 fold in the N/N 1003A cells. Some changes in other enzyme activities were also observed as a result of the transfections. Surprisingly, the ability to degrade H2O2 in the extracellular environment of the cells did not markedly change as a result of the catalase amplification. However, the ability to resist H2O2 stress was dramatically altered. Non-protein thiol (NP-SH) levels, choline uptake and glyceraldehyde phosphate dehydrogenase (GPD) activity were all markedly decreased in the non-transfected cells when they were subjected to 300 microM H2O2. However, in both transfected cell lines, these parameters remained in the normal range during H2O2 stress. The results obtained upon observing aspects of DNA metabolism were more complicated. While on H2O2 stress, non-transfected cell lines showed a marked decrease in thymidine incorporation, only the transfected alpha TN4-1 line remained in the normal range. Thymidine incorporation in transfected rabbit N/N 1003A cells was decreased compared to normal cells. In contrast, studies on single strand DNA breaks indicated that transfected rabbit cells had little damage compared to the significant DNA damage observed in the normal cells. The normal N/N 1003A cells were also much more susceptible to H2O2 induced damage than normal alpha TN4-1 cells, suggesting that the high GSH peroxidase activity observed in the rabbit cells may be detrimental since the low glutathione reductase activity in such cells results in an accelerated depletion of glutathione. The overall results suggest that augmenting lens catalase may prevent cataract development caused by H2O2 stress.

Animals↗
PubMed1998

Intraarterial urokinase produces significant attenuation of infarction volume in an embolic focal ischemia model.

A number of models of focal ischemia have been created to mimic acute middle cerebral artery (MCA) occlusion. In the present series of experiments, we report our observations on the thrombin model of MCA occlusion and the neuroprotective effects of intraarterial thrombolysis with two doses of urokinase (2500 and 5000 units/kg). In all experiments male Wistar rats were used and the animals were allowed to recover for 48 h before assessment of neurobehavioral performance on a four-point scale. The extent of cerebral hemispheric damage was calculated as the percentage of brain infarction using TTC staining. Occlusion of the MCA was effected by the introduction of an autologous blood clot into the internal carotid artery (ICA) approximately 2 mm from the origin of the MCA. This clot was formed by the drawing of 10 microl of blood into a bovine thrombin (20 microg per animal) containing intraarterial catheter, which was inserted into the right ECA. After standing for 15 min to allow clot formation, the catheter was advanced gently through the ICA to the site of injection. MCA occlusion produced a consistent large infarction in all animals. Urokinase infusion (i.a. ) was started 2 h after arterial occlusion in the initial series. In animals treated with low dose urokinase infusion there was mild protection. Animals treated with high dose urokinase infusion showed a highly significant improvement in the motor recovery and a decrease in the extent of infarction compared to control animals. In the final group, the infusion of urokinase was delayed for 3 h. While producing protection in some animals, it also produced intracerebral hemorrhage in two of eight animals. Thus delay of infusion to 180 min increased the risk of hemorrhage. This model may in the future be used to test the protective effects of combination therapy with thrombolysis and neuroprotective medications.

Animals↗
PubMed1998

Simple correction method for k-space trajectory deviations in MRI.

A method is presented to correct for the imperfections of spatial encoding gradients in MRI. The approach is simple and fast, can be performed with standard scanner hardware, and does not require separate measurements with reference phantoms. The new method, using the MR signal to accurately measure the k-space trajectory of the imaging sequence, allows for correction of gradient hardware imperfections and eddy-current effects. Initial measurements are presented which demonstrate the efficacy of the method to correct images acquired with spiral and EPI scan techniques.

Algorithms↗
PubMed1998

Ischemia and reperfusion impair the gene expression of endogenous basic fibroblast growth factor (bFGF) in rat skeletal muscles.

Our previous studies showed that the amount of endogenous basic fibroblast growth factor (bFGF) was reduced after ischemia and reperfusion insult. One of the mechanisms involved in the decrease of endogenous bFGF is the increased destruction of this growth factor associated with oxygen free radical activation and inflammation. We hypothesized that the wounding also impairs the secretion of bFGF and examined the bFGF gene expression in skeletal muscles after ischemia and reperfusion insult. In this study, a rat leg ischemia (4 h) and reperfusion (24 h) injury model was prepared and the in situ hybridization method and reverse transcriptase polymerase chain reaction technique (RT-PCR) were used to evaluate the bFGF gene expression and its localization in control (normal) and injured rat skeletal muscles. The results showed that the bFGF mRNA expression was localized in the cytoplasm in control skeletal muscle, especially at the periphery inside the cells. According to the intensity of the stain, four main classes of fibers could be identified: strongly, moderately, weakly, and negatively stained fibers. Based on the positive stain, about 82% of the total fibers examined were positive for bFGF mRNA stain. In ischemic or ischemic and reperfused rat skeletal muscles, the localization of bFGF mRNA expression was similar to that in normal skeletal muscles, but only 52% in ischemic muscles and 22% in ischemic and reperfused muscles had positive bFGF mRNA staining. RT-PCR confirmed a significant decrease in bFGF mRNA expression in ischemic and reperfused rat skeletal muscles. These results suggest that the acute ischemia and reperfusion not only induce the destruction of endogenous bFGF molecule, which is stored at the extracellular matrix of the fibers, but also downregulate the bFGF gene expression. The simultaneous dysregulation of endogenous bFGF gene expression and decreased synthesis of bFGF protein suggest a possible role of this growth factor in delayed wound healing.

Animals↗
PubMed1998

Overproduction and purification of glutaryl 7-amino cephalosporanic acid acylase.

The gene encoding glutaryl 7-amino cephalosporanic acid acylase (GL-7ACA acylase) from Pseudomonas sp. 130 has been cloned and expressed in Escherichia coli using a high-level expression system. The specific activity of the acylase in the crude extract of cells in this system is approximately 10 times that in the previous one. The overproduced enzyme can be easily isolated within 3 days to a purity of over 90% by a simple and inexpensive two-step preparative chromatographic method with an overall yield of nearly 50%. The deletion of the signal peptide and mutation in the alpha-subunit of the acylase have little influence on its posttranslational processing and its kinetic parameters.

Amidohydrolases↗
PubMed1998

Human pancreatic triglyceride lipase expressed in yeast cells: purification and characterization.

A cDNA clone encoding human pancreatic triglyceride lipase was cloned into a yeast expression vector so that the yeast PHO1 signal peptide replaced the native signal peptide. Pichia pastoris cells were transfected with the vector, and clones expressing human pancreatic triglyceride lipase were isolated. Recombinant human pancreatic lipase was expressed in broth cultures and was purified from the medium by DEAE blue Sepharose and hydroxyapatite chromatography. The highly purified lipase had specific activities for various triglyceride substrates identical to those of tissue-purified human pancreatic triglyceride lipase; it was inhibited by bile salts, required colipase for activity, and demonstrated interfacial activation. This expression system is suitable for the rapid, efficient production of human pancreatic triglyceride lipase in amounts adequate for biophysical studies.

Amino Acid Sequence↗
PubMed1998

Effect of low HDL combined with hypertriglyceridemia in coronary artery disease patients on PGI2 biological activity in relation to lipid regulating treatment.

The purpose of this study was to investigate the effect of low high-density-lipoprotein (HDL) combined with hypertriglyceridemia in coronary artery disease (CAD) patients on prostaglandin I2 (PGI2) biological activity in relation to lipid regulating treatment. The inhibitory rate of PGI2 on ADP-induced platelet aggregation was used as the index for PGI2 biological activity. Twenty health individuals served as normal controls. CAD group consisted of 20 patients with low HDL combined with hypertriglyceridemia. The results showed that, before the treatment, the stabilizing effect on PGI2 activity decreased significantly in CAD group when compared with the control group (P < 0.01). One month after the treatment, HDL level in CAD group increased significantly and TG level significantly decreased (P < 0.001). The different effect on PGI2 activity was no longer found between CAD group and control group (P > 0.05), further confirming the protecting effect of HDL on PGI2 biological activity. Low HDL is considered as an important risk factor of CAD, therefore, impaired PGI2 biological activity and increased platelet aggregation might be responsible mechanisms. Furthermore, raising HDL level by lipid regulating treatment could restore the protective effect of HDL on PGI2 and might be helpful in the prevention of the acute coronary syndrome.

Coronary Disease↗
PubMed1998

Linkage of a commoner form of recessive amyotrophic lateral sclerosis to chromosome 15q15-q22 markers.

Autosomal recessive familial amyotrophic lateral sclerosis (RFALS) is a rare form of ALS that usually presents at an early age with slow progression of symptoms. RFALS is clinically and genetically heterogeneous and the locus of RFALS type 3 was mapped to 2q33 (ALS2) in a single family. We now report linkage of a more-common form of RFALS to chromosome 15q15-q22 markers (ALS5) and show further genetic locus heterogeneity in RFALS. ALS5 is the locus for most families with RFALS and appears to be present in both North African and European populations.

Age of Onset↗
PubMed1998

Cutaneous and subcutaneous granulomata formation in mice immunized and challenged with third-stage infective hookworm (Ancylostoma caninum) larvae.

To determine the inflammatory and immunological mechanisms associated with live third-stage (L3) hookworm larval vaccines, mice were immunized either subcutaneously or orally with three doses of 500 L3 of Ancylostoma caninum at 2-week intervals, and then challenged percutaneously (via abdominal skin) with 500 L3. Non-immunized mice served as negative controls. Skin was excised from post-challenge mice at intervals between 6 h and 28 days, and then examined by light microscopy. In non-immunized mice the L3 exhibited no structural damage and infiltrating inflammatory cells were absent from the surrounding tissues. There were no changes in the cutaneous architecture. In contrast, skin recovered from the immunized mice was edematous and exhibited marked inflammatory changes with resultant destruction of the challenge L3. At 6 h post-challenge the L3 exhibited cuticular swelling and damage; the surrounding tissue was infiltrated by polymorphonuclear inflammatory cells. By 24 h granulomata in the dermis, subcutaneous tissues and underlying abdominal muscles were first observed surrounding dead L3. The number of granulomata peaked at 72 h, with the majority distributed in the subcutaneous tissues. Plasma cells predominated in the early granulomata, but by 3-7 days post-challenge foreign body giant cells began to appear. In some cases, intact and presumably living L3 were noted in the abdominal muscles 14-28 days post-challenge, which suggested that protection against larval challenge was not absolute. Granuloma formation appears to be a major component of the post-vaccination murine host immune response against challenge larvae. The observation generates several hypotheses to investigate the mechanisms of protection afforded by living helminth vaccines.

Abdominal Muscles↗