Biomedical subjects

Q Yu

Publications and source records attributed to Q Yu.

At least 127 records · Page 7Linked to original sources

PubMed1999

Induction of antitumor immunity with dendritic cells transduced with adenovirus vector-encoding endogenous tumor-associated antigens.

Dendritic cells (DCs) are professional Ag-presenting cells that are being considered as potential immunotherapeutic agents to promote host immune responses against tumor Ags. In this study, recombinant adenovirus (Ad) vectors encoding melanoma-associated Ags were used to transduce murine DCs, which were then tested for their ability to activate CTL and induce protective immunity against B16 melanoma tumor cells. Immunization of C57BL/6 mice with DCs transduced with Ad vector encoding the hugp100 melanoma Ag (Ad2/hugp100) elicited the development of gp100-specific CTLs capable of lysing syngeneic fibroblasts transduced with Ad2/hugp100, as well as B16 cells expressing endogenous murine gp100. The induction of gp100-specific CTLs was associated with long term protection against lethal s.c. challenge with B16 cells. It was also possible to induce effective immunity against a murine melanoma self Ag, tyrosinase-related protein-2, using DCs transduced with Ad vector encoding the Ag. The level of antitumor protection achieved was dependent on the dose of DCs and required CD4+ T cell activity. Importantly, immunization with Ad vector-transduced DCs was not impaired in mice that had been preimmunized against Ad to mimic the immune status of the general human population. Finally, DC-based immunization also afforded partial protection against established B16 tumor cells, and the inhibition of tumor growth was improved by simultaneous immunization against two melanoma-associated Ags as opposed to either one alone. Taken together, these results support the concept of cancer immunotherapy using DCs transduced with Ad vectors encoding tumor-associated Ags.

Adenoviridae↗

PubMed1999

Identification of a defect in the intracellular trafficking of a Kell blood group variant.

Blood group polymorphisms have been used as tools to study the architecture of the red blood cell (RBC) membrane. Some blood group variants have reduced antigen expression at the cell surface. Understanding the underlying mechanism for this reduced expression can potentially provide structural information and help to elucidate protein trafficking pathways of membrane proteins. The Kp(a+) phenotype is a variant in the Kell blood group system that is associated with a single amino acid substitution (R281W) in the Kell glycoprotein and serologically associated with a weakened expression of other Kell system antigens by an unknown mechanism. We found by immunoblotting of RBCs that the weakening of Kell antigens in this variant is due to a reduced amount of total Kell glycoprotein at the cell surface rather than to the inaccessibility of the antigens to Kell antibodies. Using a heterologous expression system, we demonstrate that the Kpa mutation causes retention of most of the Kell glycoprotein in a pre-Golgi compartment due to differential processing, thereby suggesting aberrant transport of the Kell protein to the cell surface. Furthermore, we demonstrated that single nucleotide substitutions into the coding region of the common KEL allele, as predicted by the molecular genotyping studies, was sufficient to encode three clinically significant low incidence antigens. We found that two low incidence antigens can be expressed on a single Kell protein, thus showing that the historical failure to detect such a variant is not due to structural constraints in the Kell protein. These studies demonstrate the power of studying the molecular mechanisms of blood group variants for elucidating the intracellular transport pathways of membrane proteins and the requirements for cell surface expression.

Alleles↗

PubMed1999

Synthesis of novel phenserine-based-selective inhibitors of butyrylcholinesterase for Alzheimer's disease.

Four novel analogues (8-11) of cymserine (2) were synthesized by methods similar to those recently developed for the total syntheses of N8-norphenserine (Yu, Q. S.; et al. J. Med. Chem. 1997, 40, 2895-2901) and N1,N8-bisnorphenserine (Yu, Q. S.; et al. J. Med. Chem. 1998, 41, 2371-2379). As our structure-activity studies predicted, these compounds are highly potent and selective inhibitors of human butyrylcholinesterase (BChE) and will test the novel hypothesis that BChE inhibitors are useful in the treatment of Alzheimer's disease. In a similar manner, the same modifications that provided BChE selectivity were applied to the acetylcholinesterase (AChE)-selective inhibitor, tolserine (5), to provide the novel tolserine analogues 12-15. As predicted, these modifications altered the AChE-selective action of tolserine (5) to favor a lack of cholinesterase enzyme subtype selectivity.

Acetylcholinesterase↗

PubMed1999

Complementarity between 3' terminal nucleotides of tRNA and primer binding site is a major determinant for selection of the tRNA primer used for initiation of HIV-1 reverse transcription.

The initiation of reverse transcription of human immunodeficiency virus type 1 (HIV-1) exclusively utilizes tRNALys,3 as a primer. Previous studies have shown that HIV-1 could use alternative tRNAs, such as tRNAIle or tRNAHis, to initiate reverse transcription only if the primer binding site (PBS) was made complementary to the 3' terminal 18 nucleotides of the cognate tRNA. However, upon in vitro culture, the viruses with a PBS complementary to the alternative tRNAs rapidly reverted to generate a PBS complementary to tRNALys,3. To investigate the process of reversion, we have constructed defective proviral genomes that contain a PBS complementary to tRNAIle or tRNAHis. The genomes contain the gene for xanthine-guanosine phosphoribosyl transferase (gpt) in place of env. Cotransfection of these proviral genomes with a plasmid-encoding vesicular stomatitis virus G protein (VSV-G) results in viruses that undergo a single round of HIV-1 infection; successful infections are scored as cells resistant to the drug mycophenolic acid. Using this single-round infection system, we demonstrated that HIV-1 with a PBS complementary to tRNAIle or tRNAHis is three- to fivefold less efficient in replication as measured by production of drug-resistant cell colonies compared to the wild-type virus. These viruses predominantly used the cognate tRNA as primer in their initial round of replication, although we did obtain a single cell colony in which the PBS was complementary to tRNALys,3. Using an HIV-1 provirus with a PBS complementary to yeast tRNAPhe, we established a single-round infection system in which the infectivity of this mutant HIV-1 relies on transfected yeast tRNAPhe. The results of our studies suggest that the mechanism for selection of the tRNA primer for initiation of reverse transcription relies primarily on the complementarity between the tRNA primerthe PBS.

Binding Sites↗

PubMed1999

Localization of matrix metalloproteinase 9 to the cell surface provides a mechanism for CD44-mediated tumor invasion.

The cell surface hyaluronan receptor CD44 promotes tumor growth and metastasis by mechanisms that remain poorly understood. We show here that CD44 associates with a proteolytic form of the matrix metalloproteinase-9 (MMP-9) on the surface of mouse mammary carcinoma and human melanoma cells. CD44-associated cell surface MMP-9 promotes cell-mediated collagen IV degradation in vitro and mediates tumor cell invasion of G8 myoblast monolayers. Several distinct CD44 isoforms coprecipitate with MMP-9 and CD44/MMP-9 coclustering is observed to be dependent on the ability of CD44 to form hyaluronan-induced aggregates. Disruption of CD44/MMP-9 cluster formation, by overexpression of soluble or truncated cell surface CD44, is shown to inhibit tumor invasiveness in vivo. Our observations indicate that CD44 serves to anchor MMP-9 on the cell surface and define a mechanism for CD44-mediated tumor invasion.

Animals↗

PubMed1999

Validity of a performance-based test of function in essential tremor.

BACKGROUND: The central factor influencing therapeutic decisions in essential tremor (ET) is the functional impact of the tremor. Neither the neurological examination nor computerized tremor analysis measures function. Questionnaires may assess function, but data are highly subjective. Performance-based tests of functional impairment provide an alternative means with which to assess the functional impact of ET. OBJECTIVE: To determine the internal consistency and validity of a performance-based measure of functional impairment in ET. METHODS: Subjects with ET from a community in northern Manhattan, NY, and from a clinic and control subjects each underwent a 2 1/2-hour evaluation including 12 screening questions for ET, a 31-item Tremor Disability Questionnaire to assess the functional impact of tremor, a 26-item Videotaped Tremor Examination that was rated by a neurologist, a 15-item, 10-minute Performance-Based Test, and Quantitative Computerized Tremor Analysis. Internal consistency was assessed with Cronbach alpha. The correlation between the Performance-Based Test and these other measures of tremor was assessed by means of correlation coefficients (r). RESULTS: There were 50 ET cases and 51 normal control subjects. The Performance-Based Test was internally consistent (Cronbach alpha = .92). It also demonstrated validity among cases; the total score correlated with the total number of screening questions answered yes (r = 0.44; P = .001), the total score on the Tremor Disability Questionnaire (r=0.55; P<.001), the total score on the Videotaped Tremor Examination (r=0.71; P<.001), and multiple physiological measures recorded during Quantitative Computerized Tremor Analysis. CONCLUSIONS: A valid performance-based test was developed to objectively assess functional capacity in patients with ET. This test would be useful in therapeutic trials, where it would provide an objective means to quantify the functional impact of tremor.

Aged↗

PubMed1999

Orthogonal ligation strategies for peptide and protein.

This review focuses on the concept, criteria, and methods of an orthogonal amide ligating strategy suitable for syntheses of peptides, peptide mimetics, and proteins. Utilizing unprotected peptides or proteins derived from chemical or biosynthetic sources, this ligation strategy has been shown to be general and exceptionally mild. Its orthogonality in ligating two unprotected segments with free N-terminal (NT)-amines at a specific NT-amine is achieved through a chemoselective capture step and then an intramolecular acyl transfer reaction. Both coupling reagents for enthalpic activation and protection schemes therefore become unnecessary. More than a dozen orthogonal ligation methods based on either imine or thioester captures have been developed to afford native and unusual amino acids at ligation sites of linear, branched, or cyclic peptides. Because unprotected peptides and proteins of different sizes and forms can be obtained from either chemical or recombinant sources, orthogonal ligation removes the size limitation imposed on the chemical synthesis of a protein with a native or non-native structure. Furthermore, by using building blocks from biosynthetic sources, orthogonal ligation provides a unifying operational concept for both total and semisynthesis of peptides and proteins.

Amino Acids↗

PubMed1999

Stereotactic posteroventral pallidotomy: clinical methods and results at 1-year follow up.

Twenty consecutive patients with idiopathic Parkinson's disease underwent stereotactic posteroventral pallidotomy. Schwab and England ADL scores in the "off" state were improved by 18% and in the "on" state the scores declined by 2%. Three patients also reported marked improvement in "off" state dystonia. One-year data are available on 12 patients who underwent evaluations according to the Core Assessment Program for Intracerebral Transplantation protocol preoperatively and at 3, 6, and 12 months after surgery. Significant improvements in Unified Parkinson's Disease Rating Scale sections II and III scores in the "off" state, composite "off" state scores of bradykinesia and rigidity, contralateral tremor in the "off" state, and contralateral dyskinesias were observed. Although there was reduction in the daily levodopa dose, this did not reach statistical significance. Major complications (15%) included hemiparesis (one of 20) and visual field cuts (two of 20); minor complications (45%) included mild cognitive dysfunction (four of 20), reading difficulty not related to visual disturbance (one of 20), and 5-10 lb weight gain (four of 20).

Activities of Daily Living↗

PubMed1999

The internal critical level concept of nonspecific toxicity.

The internal lethal concentration (ILC) can be an effective approach in describing the toxicity of a chemical to aquatic organisms that can complement the use of the external toxic concentration characteristic of the LC50. The ILC is an estimate of the toxicant concentration close to the target site and can be estimated from bioconcentration relationships and acute toxicity data. The observed ILC values were found to be consistent for organic compounds exerting the same mode of toxic action. The nonspecific toxicants have the lowest toxicity and the highest ILC values, whereas the chemicals exhibiting specific modes of action have lower concentrations and higher toxicity. There are some reports that the ILC value decreases with increasing exposure periods for various organic chemicals with aquatic organisms. The nonspecific toxicants possibly exhibit their toxic action at the target site by at least two different mechanisms depending on the toxicant concentrations. First, the toxicants bind directly to membrane proteins at relatively low concentrations, resulting in reversible toxic effect. Second, the toxicants inhibit the membrane proteins, and alterations in the lipid bilayers occur at toxicant concentrations sufficient to produce mortality of the organisms. The nonspecific toxicity expressed as acute and chronic toxicity measures are found to correlate well with log Kow. However, the relationship between the ILC and log Kow is less satisfactory because the values of ILC are relatively consistent compared to those of LC50.

Animals↗

PubMed1999

A model for non-specific toxicity with aquatic organisms over relatively long periods of exposure time.

Experimental data have shown that the internal lethal concentrations of halobenzenes for aquatic organisms decreased with exposure time. In this paper, a model based on the concept of life expectancy reduction was developed to describe this relationship. The model was verified with experimental data for fish (Gambusia affinis) and juvenile crab (Porturius pelagicus(L)). It is proposed that long term non-specific toxicity can be measured as the reduction of the life expectancy of the exposed organism per unit internal concentration (or volume fraction) of the toxic compound. The model can be used to estimate internal lethal concentration at any given exposure period and vice versa. The model can also be used to estimate chronic values of the internal concentration, of the toxicants. It provides a useful tool for assessment of environmental risk of organic compounds in aquatic ecosystems.

Algorithms↗

PubMed1999

FGF-2 induces surfactant protein gene expression in foetal rat lung epithelial cells through a MAPK-independent pathway.

Fibroblast growth factors (FGFs) play important roles in diverse aspects of animal development including mammalian lung epithelial cell proliferation, differentiation, and branching morphogenesis. We developed an in vitro lung epithelial cell culture system to study functions and mechanisms of FGFs in regulating growth and differentiation of primary foetal rat lung epithelial cells. In comparison with other growth factors such as IGF-I, EGF, and HGF, FGFs were the most potent mitogens in stimulating lung epithelial cell proliferation. In the presence of FGF-1, 2, or 7, the primary lung epithelial cells could be propagated for generations and grown for more than two mo in vitro. Among the three FGFs tested, FGF-7 showed the strongest stimulation in cell growth. FGF-2, on the other hand, is the most effective inducer of lung epithelial cell-specific surfactant protein gene expression (SP-A, -B, and -C). FGF-2 upregulated SP-C expression in a dose-dependent manner. More interestingly, the induction of surfactant protein gene expression by FGF-2 appeared to be independent of MAPK pathway, since the SP-C expression was not inhibited but rather augmented by MEK1 inhibitor which inhibited MAPK activation and cell proliferation. Similar effects were observed for the expressions of surfactant protein genes SP-A and SP-B. In contrast to MAPK, FGF-2-induced SP-C expression was partially inhibited by PI 3-kinase inhibitor wortmannin. These data suggest dynamic roles and complex signalling mechanisms of FGFs in regulating lung epithelial cell proliferation and differentiation. While a MAPK-dependent pathway is essential for all three FGFs to stimulate cell proliferation, a MAPK-independent pathway may be responsible for the FGF-2-induced surfactant protein gene expression. PI 3-kinase may play an important role in mediating FGF-2-induced lung epithelial cell differentiation during development.

Animals↗

PubMed1999

Transmembrane tyrosine phosphatase LAR induces apoptosis by dephosphorylating and destabilizing p130Cas.

BACKGROUND: LAR is a transmembrane receptor-like protein tyrosine phosphatase (PTP). Genetic studies of Drosophila LAR suggest that LAR may function to regulate cell adhesions or adhesion-mediated signal transduction. The over-expression of LAR in mammalian tissue culture cells does not affect cell adhesion but induces caspase-dependent apoptosis. This study investigates molecular mechanisms of LAR-induced apoptosis by searching for in vivo substrates of LAR which are responsible for LAR-induced apoptosis. RESULTS: The over-expression of LAR in tissue culture cells specifically decreased the steady state protein level of p130Cas, a multifunctional signal assembly protein in signal transduction, by reducing the tyrosine phosphorylation and protein stability of p130Cas. The reduction of p130Cas protein level could be inhibited by tyrosine phosphatase inhibitors. Phosphatase domain-deleted mutant LARs had no effect on p130Cas. LAR also preferentially dephosphorylated p130Cas in vitro. Subcellularly, LAR and p130Cas were co-localized along stress fibres and at focal adhesions. LAR over-expression eliminated p130Cas from focal adhesions without affecting focal adhesion assembly. Restoring the level of p130Cas alleviated LAR-induced apoptosis. CONCLUSIONS: p130Cas is an in vivo substrate of LAR. LAR specifically dephosphorylates and destabilizes p130Cas and may play a role in regulating cell adhesion-mediated cell survival. The function of p130Cas in focal adhesions may not be to regulate focal adhesion assembly and cell adhesion but rather to transduce the cell adhesion-generated signals which are essential for cell survival.

Animals↗

PubMed1999

Total synthesis of (-)-incrustoporin.

(-)-Incrustoporin (1) has been synthesized using aldol condensation of ethyl p-tolyl-acetate (2) and (2R)-benzoyloxy-butanal (3), followed by acid-catalyzed deprotection of the benzoyl group, lactone ring-closure, and elimination of the beta-OH in a one-pot manner. The aldehyde 3 was prepared from the commercially available D-mannitol by a two-directional strategy.

4-Butyrolactone↗

PubMed1999

gamma-Glutamyl transferase (GGT) deficiency in the GGTenu1 mouse results from a single point mutation that leads to a stop codon in the first coding exon of GGT mRNA.

GGTenul, a recently described genetic murine model of gamma-glutamyl transferase (GGT) deficiency, was induced by the point mutagen N-ethyl-N-nitrosourea and is inherited as an autosomal recessive trait. The phenotype of systemic GGT deficiency suggested a mutation site within the cDNA coding region which is common in all GGT transcripts. To identify this site, total lung and kidney RNA was isolated from normal and mutant mice, amplified by RT-PCR using GGT-specific primers, cloned as two overlapping approximately 1 kb GGT cDNA fragments, sequenced and compared with that in the literature. A single base pair substitution was identified in the coding region at position 237, where thymidine became adenine, and this mutation replaced a leucine codon, TTG, with a termination codon, TAG. This mutation site was confirmed in mutant genomic DNA by PCR using primers that flanked the predicted site and spanned the intron between the common GGT non-coding exon and the first GGT coding exon. This PCR product was sequenced directly with the secondary 3' PCR primer, the mutation site identified and the protocol then utilized to genotype animals. In addition to this mutation, the steady-state level of GGT mRNA in mutant kidney is reduced 3-fold compared with the control. Heterodimeric GGT protein is not detectable by western blot in either whole kidney homogenate or a microsomal membrane fraction. The steady-state mRNA level of gamma-glutatmyl cysteinyl synthetase was unchanged in mutant mice compared with normal, but that of heme oxygenase-1 and Cu,Zn-SOD was induced 4- and 3-fold, respectively. Hence, the GGTenul mouse model of GGT deficiency results from a single point mutation in the first coding exon of GGT mRNA and the resulting impairment in glutathione turnover induces oxidative stress in the kidney.

Animals↗

PubMed1999

Combinatorial screening and intracellular antiviral activity of hairpin ribozymes directed against hepatitis B virus.

A combinatorial screening method has been used to identify hairpin ribozymes that inhibit hepatitis B virus (HBV) replication in transfected human hepatocellular carcinoma (HCC) cells. A hairpin ribozyme library (5 x 10(5) variants) containing a randomized substrate-binding domain was used to identify accessible target sites within 3.3 kb of full-length in vitro-transcribed HBV pregenomic RNA. Forty potential target sites were found within the HBV pregenomic RNA, and 17 sites conserved in all four subtypes of HBV were chosen for intracellular inhibition experiments. Polymerase II and III promoter expression constructs for corresponding hairpin ribozymes were generated and cotransfected into HCC cells together with a replication-competent dimer of HBV DNA. Four ribozymes inhibited HBV replication by 80, 69, 66, and 49%, respectively, while catalytically inactive mutant forms of these ribozymes affected HBV replication by 36, 28, 0, and 0%. These findings indicate that the inhibitory effects on HBV replication were largely mediated by the catalytic activity of the ribozymes. In conclusion, we have identified catalytically active RNAs by combinatorial screening that mediate intracellular antiviral effects on HBV.

Antiviral Agents↗

PubMed1999

Purging of contaminating breast cancer cells from hematopoietic stem cell grafts by adenoviral GAL-TEK gene therapy and magnetic antibody cell separation.

The presence of contaminating tumor cells in autologous bone marrow or peripheral blood stem cell (PB-SC) preparations increase the likelihood of relapse in women receiving transplants for metastatic breast cancer. We describe a new technique for purging breast cancer cells (BCCs) that combines two independent strategies: (a) the specific enrichment of CD34+ progenitor stem cells by magnetic antibody cell separation (MACS), and then (b) infection of the contaminating BCCs with a recombinant adGAL-TEK marker/suicide gene adenovirus (ad-v), followed by the addition of ganciclovir (GCV). Infection with this ad-v results in three to four times greater expression of ad-v-delivered reporter gene in BCCs than in CD34+ cells. In addition -2 h, -low multiplicity of infection (50:1) adGAL-TEK infections of BCC lines (MCF-7 and BT474) eradicated >99% of BCCs after 72 h of exposure to 20 microM GCV. However, exposure to both adenovirus and GCV at the MOIs and doses used had little effect on hematopoietic stem cells to form colonies in colony-forming unit assays. adGAL-TEK infection in our model system (10(3)-10(5) BCCs added into 10(7) HSCs) also resulted in the 3 to 5 log eradication of clonogenic BCCs after the addition of GCV. MACS enrichment/purification of CD34+ cells from PB-SC contaminated with 2 x 10(6) to 5 x 10(7) BCCs followed by adGAL-TEK infection and GCV addition resulted in 5-7-log depletion of clonogenic BCCs as well as enrichment of CD34+ progenitor cells to >98%, with the recovery of >70% of hematopoietic stem cells. This adenoviral purging system is so robust that poor MACS purification, resulting in 1.5-log depletion of BCCs, still permits excellent ad-v infection and BCC killing.

Adenoviridae↗

PubMed1999

[The profile of low bone mass in amenorrhea with elevated follicle stimulating hormone].

OBJECTIVE: To observe the characteristics of low bone mass in amenorrhea with elevated follicle stimulating hormone(FSH). METHODS: Amenorrhea patients with elevated FSH: primary amenorrhea (PA) 18 cases, secondary amenorrhea (SA), 171 cases and age matched control with normal menstruation (Nor) 180 cases. The descriptive parameters were: estradiol (E2), alkaline phosphatase (ALP), urinary excretion of calcium to creatinine ratio (Ca/Cr), the cortical bone mineral density (CBMD) at right radius measured by single photon absorptimetry (SPA) and the trabecular bone mineral density (TBMD) at lumbar vertebra body measured by quantitative computerized tomography (QCT). RESULTS: The experiment had shown the average E2 level in amenorrhea patients to be < 150 pmol/L. Significantly higher ALP and Ca/Cr values than the Nor group. In the SA group, the CBMD value was (655 +/- 69) mg/cm2, which was significantly lower than the Nor group's value of (677 +/- 56) mg/cm2 (3.2% lower, P < 0.01). The TBMD value is (145 +/- 26) mg/cm3, which is significantly lower than the Nor group's value of (192 +/- 28) mg/cm3 (24.5%, P < 0.001). The disparity with the Nor group was even greater in the PA group (11.1% and 35.7% lower, respectively). The BMD of the amenorrhea patients were negatively linearly correlated with their amenorrhea age. CONCLUSIONS: The serum estradiol level in amenorrhea patients with high FSH was so low that their bone turnover was increased which led to the insufficient bone accumulation and dramatically dropping of TBMD. Its extent was related to the initial age and the duration of ovarian failure.

Absorptiometry, Photon↗

PubMed1999

[The medialis pedis flap based on the medial fasciocutaneous branches of the dorsal pedal artery].

OBJECTIVE: This is to report the design and application of the medialis pedis flap. METHODS: Based on the medial fasciocutaneous branches of the dorsal pedal artery, a medialis pedis flap can be raised. The flap had been used in 18 patients with soft tissue defects of the dorsum pedis, ankle region, lower leg or hand. RESULTS: The anatomic observation of the blood supply to the medial region of the foot showed that a constant distribution of fasciocutaneous branches issued from the dorsal pedal artery was an important blood supply to this area. All flaps used in the 18 patients survived completely with satisfactory results and minimal morbidity at the donor site. CONCLUSION: We believe that the medial fasciocutaneous branches of the dorsal pedal artery are the reliable pedicle of the medialis pedis flap. The flap is useful for reconstruction of the soft tissue defects around the foot, ankle, lower leg or hand.

Adolescent↗