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T Yang

Publications and source records attributed to T Yang.

At least 37 records · Page 2Linked to original sources
PubMed2001

The leukocyte common antigen-related protein tyrosine phosphatase receptor regulates regenerative neurite outgrowth in vivo.

Drosophila and leech models of nervous system development demonstrate that protein tyrosine phosphatase (PTP) receptors regulate developmental neurite outgrowth. Whether PTP receptors regulate neurite outgrowth in adult systems or in regenerative states remains unknown. The leukocyte common antigen-related (LAR) receptor is known to be present in rodent dorsal root ganglion (DRG) neurons; therefore, the well established model of postcrush sciatic nerve regeneration was used to test the hypothesis that LAR is required for neurite outgrowth in the adult mammalian nervous system. In uninjured sciatic nerves, no differences in nerve morphology and sensory function were detected between wild-type and LAR-deficient littermate transgenic mice. Sciatic nerve crush resulted in increased LAR protein expression in DRG neurons. In addition, nerve injury led to an increase in the proportion of LAR protein isoforms known to have increased binding affinity to neurite-promoting laminin-nidogen complexes. Two weeks after nerve crush, morphological analysis of distal nerve segments in LAR-deficient transgenic mice demonstrated significantly decreased densities of myelinated fibers, decreased axonal areas, and increased myelin/axon area ratios compared with littermate controls. Electron microscopy analysis revealed a significant twofold reduction in the density of regenerating unmyelinated fibers in LAR-/- nerves distal to the crush site. Sensory testing at the 2 week time point revealed a corresponding 3 mm lag in the proximal-to-distal progression of functioning sensory fibers along the distal nerve segment. These studies introduce PTP receptors as a major new gene family regulating regenerative neurite outgrowth in vivo in the adult mammalian system.

Animals↗
PubMed2001

Human mdm2 mediates multiple mono-ubiquitination of p53 by a mechanism requiring enzyme isomerization.

The mdm2 gene product is an important regulator of p53 function and stability. mdm2 is an E3 ubiquitin ligase for p53 and the RING finger domain of mdm2 is critical for ligase activity. Ubiquitin (Ub) conjugation is a general targeting modification and poly-ubiquitin chains specifically target proteins to the proteasome for degradation. In this report, we show that the multistep cascade of mdm2-mediated p53 ubiquitination can be reduced to three purified recombinant proteins: ubiquitin-conjugated E2, mdm2, and p53. This simplification allows enzymatic analysis of the isolated ligase reaction. The simplified reaction recapitulates the ubiquitination of p53 observed with individual components and the p53-Ub((n)) is qualitatively similar to p53-Ub((n)) detected in lactacystin-treated cells. Surprisingly, we find that p53 is modified with multiple mono-ubiquitin moieties as opposed to a poly-ubiquitin chain. Finally, kinetic analysis indicates the transfer reaction proceeds either through a modified Ping Pong mechanism involving requisite enzyme isomerization steps, or through a Rapid Equilibrium Random Bi Bi mechanism involving very large anti-cooperative interactions between the two substrate binding pockets on the enzyme, mediated through allosteric changes in enzyme structure.

Ethylmaleimide↗
PubMed2001

Enhanced reporter gene expression in the rat brain from helper virus-free HSV-1 vectors packaged in the presence of specific mutated HSV-1 proteins that affect the virion.

Herpes simplex virus (HSV-1) gene expression is hypothesized to shut off promoters in HSV-1 vectors, but in a helper virus-free HSV-1 vector system, a number of promoters support only short-term expression. Thus, recombinant gene expression remains short-term in the absence of approximately 99% of the HSV-1 genome. To resolve this paradox, we hypothesized that specific HSV-1 proteins that affect the virion can shut off recombinant gene expression. This study evaluated expression from HSV-1 vectors, containing neuronal-specific promoters, that were packaged in the presence of specific mutated HSV-1 proteins that affect the virion. The mutated HSV-1 proteins that were examined included two protein kinases (U(L)13 and U(S)3), the virion host shut-off factor (vhs), the transactivator of immediate early promoters (VP16), and a virion protein that affects RNA metabolism (U(S)11). Helper virus-free packaging could occur in the presence of each mutated protein alone or specific combinations of two or three mutated proteins. In BHK and PC12 cells, vectors packaged in the presence of each mutated protein increased ( approximately 2-fold) the level of expression per cell, and vectors packaged in the presence of specific combinations of mutated proteins supported larger (4-7-fold) increases. In the rat striatum, vectors packaged in the presence of a mutated U(S)3 displayed enhanced gene transfer (13-18-fold increases in the number of cells at 4 days), and vectors packaged in the presence of mutated U(L)13 or VP16 enhanced long-term expression (2 months). Vectors packaged in the presence of mutated vhs or U(S)11 displayed minimal changes in expression.

Animals↗
PubMed2001

Identification and cellular localization of human PFTAIRE1.

We isolated a novel member of putative Cdc2-related serine/threonine protein kinases from a Hela cell cDNA library. The cDNA encodes a protein of 469 amino acids, sharing 95% identities with the mouse PFTAIRE1 throughout the entire protein sequence. This gene was designated human PFTAIRE1. The gene was located at human chromosome 7q21.13 with radiation hybrid polyermase chain reaction (RH-PCR) analysis. By Northern blotting analysis, an approximately 6 kb transcript is detected with varied levels of expression of the hPFTAIRE1 in 16 human tissues. The hPFTAIRE1 was highly expressed in brain, pancreas, kidney, heart, testis and ovary. The transcript was also detected at lower level in other tissues, except in spleen and thymus where the transcript was hardly detected. The protein was fused to the C-terminus of a green fluorescent protein (GFP) and ectopically expressed in Hela cells. The florescence microscope results indicated that the hPFTAIRE1 exhibits cytoplasmic distribution.

Amino Acid Sequence↗
PubMed2001

Fabrication of phospholipid bilayer-coated microchannels for on-chip immunoassays.

Herein we describe a new class of microfluidic immunoassays based upon solid supported lipid bilayers. Two-dimensionally fluid bilayer material, which can accommodate multivalent binding between surface-bound ligands and aqueous receptors, was coated on the surface of poly(dimethylsiloxane) microchannels. The bilayers contained dinitrophenyl (DNP)-conjugated lipids for binding with bivalent anti-DNP antibodies. Twelve independent data points of surface coverage versus bulk protein concentration could be made simultaneously by forming a linear array of channels and flowing fluorescently labeled antibodies into them. This enabled an entire binding curve to be obtained in a single experiment. The measured apparent binding constant for the DNP/anti-DNP system was 1.8 microM. The methodology for performing heterogeneous assays developed here not only produces rapid results but also requires much less protein than traditional procedures and eliminates some standard sources of experimental error.

Immunoassay↗
PubMed2001

Differential subtyping of depression.

We studied a group of patients with depression divided into subtypes of non-chronic major depression, chronic major depression, and pure dysthymia. The purpose of this study was to determine if clinical and family history factors separated these types of depression. We reviewed records from semi-structured clinical interviews and abstracted data regarding factors that might differentiate these three depressive subtypes. In general we found what might be predicted from the definitions of dysthymia versus major depression, that is, ratings for severity of depression were lower for dysthymic patients as compared to patients with non-chronic or chronic major depression. We also found lower ratings for social functioning (GASF) for dysthymic patients as compared to the other depressive subtypes. Our study does not provide data to sufficiently separate these three subtypes. However, in the course of reviewing the literature on this topic, very few studies have separated patients into these distinct depressive subtypes. Further studies are needed to indicate if these subtypes can be meaningfully separated.

Acute Disease↗
PubMed2001

Characterization of ultrasound-detected cerebral microemboli in patients undergoing cardiac catheterization using an in vitro middle cerebral artery model.

Cerebral embolization has been documented as one of the complications of diagnostic heart catheterization by transcranial Doppler (TCD). This study aimed to evaluate our hypothesis that the nature of embolic signals involved in different stages of catheter manipulation may be distinct. TCD-detected cerebral emboli occurring at different phases of cardiac catheterization were registered and differentiated by comparing their acoustic signatures with the Doppler signals generated from clinically frequently encountered embolic materials in an in vitro middle cerebral artery model. We found that there was a significant difference in embolic signal intensity and duration between different phases of cardiac catheterization. Our data suggest that different types of emboli may be involved in different phases of the catheterization. Cathet Cardiovasc Intervent 2001;53:323-330.

Adult↗
PubMed2001

Neurotransmitter dopamine applied in electrochemical determination of aluminum in drinking waters and biological samples.

It was demonstrated that the decrease of the differential pulse voltammetric (DPV) anodic peak current of dopamine (3,4-dihydroxyphenylethylamine, DA) was linear with the increase of aluminum (Al) concentration. Under optimum experimental conditions (pH 4.6, 1.2 x 10(-3) M DA, and 0.04 M NaAc-HAc buffer solution), the linear range is 4.0 x 10(-7)-8.0 x 10(-5) M, the detection limit is 1.4 x 10(-7) M, and the relative standard deviation for 4 x 10(-5) M Al(III) is 3.5% (n=8). Many foreign species, especially some low-molecule-weight biological molecules, were chosen for interference testing. The proposed method was applied to the determination of Al in biological samples such as synthetic renal dialysate, Ringer's solution, human blood, cerebrospinal fluid of a patient, and urine of a diabetic patient. The corresponding recoveries were generally between 95 and 105%. The basic principle of the method was determined by examining Al complexed with DA. This results in the blockage of the electroactive sites on DA, followed eventually by the reduction of the electrochemical response of DA. This result was verified by examining the behavior of DA, both in the presence and absence of Al, using electrochemical, UV-Vis, Raman, and (13)C NMR spectroscopic methods.

Aluminum↗
PubMed2001

A focal embolic model of cerebral ischemia in rats: introduction and evaluation.

Cerebral thromboembolism is the most common type of acute stroke in the clinical setting. In the present study, we have described a focal embolic model of cerebral ischemia in rat. Cerebral ischemic injury in two different sizes was induced by injection of two different volumes of pre-formed clots into the middle cerebral artery (MCA). Neurological deficits were assessed at 1 and 24 h, respectively, after the MCA embolization. The brain infarction was evaluated with 2,3,5-triphenyltetrazolium chloride (TTC) staining at 72 h following embolic stroke. The incidence of gross hemorrhage was also identified on the TTC-stained brain sections. This study consisted of two groups. In the first group 10 microl of pre-formed clot was injected into MCA (n=10), and in the second group 5 microl of clot was injected (n=10). Embolizing a pre-formed clot resulted in an infarction in the territory irrigated by the MCA. Embolization with the different volume of clots resulted in different sizes of brain infarction, 32.1+/-2.9% (mean+/-S.E.) in the 10-microl group versus 23+/-4.5% (mean+/-S.E.) in the 5-microl group (P<0.05). The infarction size as well as neurological deficits correlated well with the volume of the clot injected. These results thus show that with the procedure described here a reliable and reproducible ischemic injury is produced in the brain. The model is relevant to thromboembolic ischemia in patients, and may offer a useful tool to investigate mechanisms underlying ischemic brain injury. It may also be used to test thrombolytic agents in ischemic brain injury.

Animals↗
PubMed2001

Learning deficits, but normal development and tumor predisposition, in mice lacking exon 23a of Nf1.

Neurofibromatosis type 1 (NF1) is a commonly inherited autosomal dominant disorder. Previous studies indicated that mice homozygous for a null mutation in Nf1 exhibit mid-gestation lethality, whereas heterozygous mice have an increased predisposition to tumors and learning impairments. Here we show that mice lacking the alternatively spliced exon 23a, which modifies the GTPase-activating protein (GAP) domain of Nf1, are viable and physically normal, and do not have an increased tumor predisposition, but show specific learning impairments. Our findings have implications for the development of a treatment for the learning disabilities associated with NF1 and indicate that the GAP domain of NF1 modulates learning and memory.

Animals↗
PubMed2001

Osteopontin gene is expressed in the dermal papilla of pelage follicles in a hair-cycle-dependent manner.

Hair follicle formation and maintenance involve intimate interactions between follicular epithelial cells and a group of specialized mesenchymal cells known as the dermal papilla. Using the random primer polymerase chain reaction, we have identified an approximately 1.4 kb osteopontin mRNA that is present in large quantities in cultured rat vibrissa dermal papilla cells but undetectable in cultured rat skin fibroblasts. In situ hybridization showed that the osteopontin gene is expressed in dermal papilla cells of pelage follicles during catagen but not in anagen or telogen. As an acidic glycosylated RGD-containing extracellular matrix protein, osteopontin can function both as a cell attachment protein and as a soluble cytokine playing roles in signaling, cell migration, tissue survival, anti-inflammation, and T-cell-mediated cellular immunity. Our results indicate that the comparison of the mRNA of cultured dermal papilla cells and fibroblasts can lead to the identification of not only anagen-specific genes (e.g., nexin 1), but also a catagen-specific gene. We have thus provided evidence that specific genes are turned on during catagen, which is therefore not simply a passive "degenerative" phase. The functional role of osteopontin in catagen is unclear but it may promote the formation of a tightly aggregated dermal papilla, and/or protect the dermal papilla cells from apoptosis induced by cytokines or hypoxia during catagen.

Alopecia↗
PubMed2001

Different dynamic patterns of extracellular glutamate release in rat hippocampus after permanent or 30-min transient cerebral ischemia and histological correlation.

The extent and severity of neuronal damage is different in ischemia with reperfusion compared to ischemia and no reperfusion. To investigate the role of glutamate in cerebral ischemia-reperfusion injury, in vivo microdialysis was performed to examine the dynamic profile of glutamate in the hippocampus in a transient (30 min) or permanent middle cerebral artery occlusion (MCAo) in Wistar rats. The extracellular concentration of glutamate in the cornu ammonis (CA)1 sector of the ipsilateral hippocampus showed a significant but transient elevation of glutamate for both groups immediately following ischemic insult. The initial high peak in glutamate levels in the transient MCAo group was followed by two secondary elevations in glutamate at 50 min and 90 min after initialization of reperfusion. The histopathological outcome was also different in the two groups. The observation that glutamate releases occurred in the early reperfusion phase provided an evidence of additional excitotoxicity of glutamate and thereby a therapeutic base for extended use of glutamate antagonist in the ischemia-reperfusion injury.

Animals↗
PubMed2001

Helper virus-free HSV-1 vectors packaged both in the presence of VSV G protein and in the absence of HSV-1 glycoprotein B support gene transfer into neurons in the rat striatum.

Herpes simplex virus (HSV-1) vectors have potential for gene transfer into quiescent cells, but the gene transfer process could be more efficient. In other vector systems, both the titers and the efficiency of gene transfer have been enhanced by pseudotyping the vector particles with vesicular stomatitis virus (VSV) G protein. In this report, we pseudotyped helper virus-free HSV-1 plasmid vectors with VSV G protein. Packaging was performed in the presence of both VSV G protein and a deletion in an essential HSV-1 glycoprotein, gB. The resulting vector stocks supported gene transfer into both fibroblast and neuronal cell lines. VSV G protein was required for gene transfer because preincubation of these vector stocks with antibodies directed against either VSV G protein or VSV reduced the titer to undetectable levels. Although the titers were lower than those obtained using the unmodified vector system, the titers were not increased by use of chimeric proteins that contain the extracellular domain of VSV G protein and the transmembrane and/or cytoplasmic domains of specific HSV-1 glycoproteins. Also, the titers were not increased by performing the packaging in the presence of deletions in multiple HSV-1 glycoproteins. Nonetheless, pHSVlac pseudotyped with VSV G protein supported gene transfer into striatal neurons in the rat brain. Thus, HSV-1 vectors pseudotyped with VSV G protein may be useful for specific gene transfer studies.

Animals↗
PubMed2001

Interpolymer complexation. II. Entrapment of ibuprofen by in-situ complexation between polyvinyl acetate phthalate (PVAP) and polyvinylpyrrolidone (PVP) and development of a chewable tablet formulation.

A new method involving in situ complexation between polyvinyl acetate phthalate (PVAP) and polyvinylpyrrolidone (PVP) has been developed for the entrapment of ibuprofen, a bitter tasting anti-inflammatory drug. The procedure involved dissolving ibuprofen in a thoroughly mixed aqueous alkaline solution of PVAP and PVP, and subsequently slowly adjusting the pH of the solution to 1 with dilute HCl. The yield of the entrapped product, and the percent entrapment of ibuprofen, were 85-90%, and 90-98%, respectively. The PVAP-PVP entrapped granules showed no bitter taste due to ibuprofen. The chewable tablets, prepared by mixing the granules with a cherry-flavored directly compressible tableting excipient, exhibited a release of less than 2% of ibuprofen in pH 1.2 buffer over a period of three hours. In pH 7.4, 100% of ibuprofen was released in six hours. The results presented show that in situ complexation between PVAP and PVP may be useful to produce palatable ibuprofen granules suitable for use in the development of chewable tablets.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Glass vials for small volume parenterals: influence of drug and manufacturing processes on glass delamination.

PURPOSE: Studies were initiated to examine the effect of formulation and process variables on the delamination process and also the influence of the glass manufacturing process, supplier, and glass surface treatment. METHODS: Stress testing was performed by exposing filled vials to multiple sterilization cycles followed by accelerated stability testing. Delamination incidence was determined by visual examination, light obscuration (HIAC), and microscopical methods. The inner surface of vials from each supplier and lot were also examined by scanning electron microscopy. RESULTS: Vials sourced from Supplier A had smooth surfaces as demonstrated by SEM examination, whereas vials sourced from Suppliers B and C displayed extensive surface imperfections such as pitting and/or deposits. These imperfections were localized to the vial wall, adjacent to the vial bottom, and increased with sulfate treatment. Delamination incidence increased in those vial lots with increased surface imperfections. Thus, vials sourced from Supplier A had the lowest frequency of delamination. Sulfate treatment and high pH increased delamination incidence to as high as 100%. CONCLUSION: These results demonstrate the importance of the surface morphology created during the vial forming process. Given the diferences observed, final vial selection should include extensive microscopical and product stress testing studies on multiple vial lots.

Antineoplastic Agents↗
PubMed2001

Preparation and characterization of spray-dried oxidized cellulose microparticles.

The goal of this study was to investigate the feasibility of spray drying to produce microparticles of oxidized cellulose (OC), a biocompatible and bioresorbable polymer. OCs containing 7, 13, and 20 wt% carboxylic groups were converted into stable aqueous dispersions and then spray dried using a Yamoto G-32 spray dryer equipped with a standard fluid nozzle with an orifice of 406 microm. The following operating conditions were investigated: inlet temperature 140, 170, and 190 degrees C; feed rate 3, 6, and 9 mL/min; and atomization airpressure 0.5, 1, and 1.5 kg f/cm2. The amounts of OC used in feed were 1, 2.5, and 5%. OC microparticles produced under these conditions were shrunken spheres, ranging in size between 0.98+/-0.47 and 2.05+/-0.98 microm. The different operating conditions used had no significant effect on the size and shape of particles. The use of a water-soluble plasticizer (glycerin, polyethylene glycol 400, or polyethylene glycol 6000) in the dispersion yielded microparticles with a good sphericity and a smooth surface morphology, whereas no change in the shape or size of microparticles was noted with water-insoluble plasticizers, Triacetin and dibutyl phthalate. Powder X-ray diffraction and Fourier transform infrared spectral analyses of spray-dried microparticles showed no change in the solid-state structure of OC. In conclusion, results show that OC can be converted into stable aqueous dispersions and used to produce microparticles by spray drying.

Capsules↗
PubMed2001

Drug block of I(kr): model systems and relevance to human arrhythmias.

The long QT-related arrhythmia torsades de pointes (TdP) can arise with mutations in HERG and during treatment with drugs that block cardiac I Kr, the current encoded by HERG. Multiple test systems have been used to assess drug block of I Kr. This study evaluated the I Kr blocking potency of a series of antiarrhythmics associated with a range of clinical risks of TdP in two such systems: mouse AT-1 cells (in which I Kr is the major repolarizing current) and Ltk cells transiently transfected with HERG (n = 4-10 cells per drug). For each compound, the concentration required to produce 50% block of I Kr or HERG tail currents (IC 50 ) was determined. There was an excellent correlation ( r = 0.98, p < 10 -5 ) between values obtained in the two systems. However, the relation between the liability of a drug to cause TdP appeared dissociated from I Kr blocking potency. Quinidine, dofetilide, ibutilide, procainamide, and disopyramide are all associated with TdP, but only the first three were potent blockers (IC 50 < or = 1 microM ), whereas procainamide and disopyramide were not (IC 50 > 50 microM ). Conversely, verapamil and amiodarone, drugs not associated with TdP, were also blockers (IC 50 < or = 1 microM ). We conclude that I Kr blocking potency can be readily assessed in either AT-1 cells or systems in which HERG is heterologously expressed. However, not all drugs causing TdP are potent I Kr blockers, and I Kr block is not necessarily associated with TdP. Other properties of these drugs, therefore, contribute to their propensity to cause TdP.

Animals↗