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Y Liu

Publications and source records attributed to Y Liu.

At least 487 records · Page 27Linked to original sources
PubMed2001

Characterization of a cluster of late genes of guinea pig cytomegalovirus.

Human cytomegalovirus (HCMV) is the most common congenital infection, and is associated with a high rate of morbidity and mortality in the newborn infant. Guinea pig cytomegalovirus (GPCMV) is transmitted through the placenta with resulting fetal infection, and provides an excellent model for the study of fetal cytomegalovirus infection. We have characterized a cluster of late GPCMV genes, identifying GPCMV homologs of the HCMV G protein-coupled receptor gene, UL33; the transcriptional repressor gene, UL34 and two genes encoding tegument proteins, UL32 and UL35. We also identified the GPCMV homolog of UL37, an antiapoptotic gene. Surprisingly, no GPCMV homolog to HCMV UL36 was identified in the same genomic region. Furthermore, two of the predicted GPCMV proteins share greater identity with HHV-6 and/or HHV-7 homologs than with other cytomegalovirus homologs. The identification of GPCMV homologs of conserved viral genes, particularly genes involved in pathogenicity such as the G protein-coupled receptors, will facilitate future analysis of the role of these genes in infections.

Amino Acid Sequence↗
PubMed2001

Ultrasound-Induced hyperthermia increases cellular uptake and cytotoxicity of P-glycoprotein substrates in multi-drug resistant cells.

PURPOSE: Localized hyperthermia has been shown previously to augment the cytotoxicity of some lipophilic anticancer drugs. Because many of the substrates for the multi-drug resistance (MDR) transporter P-glycoprotein (P-gp) are lipophilic in nature, studies were conducted to test the hypothesis that hyperthermia induced by ultrasound could also increase cellular uptake and cytotoxicity of P-gp substrates by P-gp-expressing cells. METHODS: To test this hypothesis, we studied the effects of hyperthermia and ultrasound on cellular accumulation of putative P-gp substrates, rhodamine 123 (R123) and doxorubicin (DOX), and cytotoxicity of DOX in the parent and MDR variants of two human cancer cell lines. RESULTS: Treatment of cells with hyperthermia or ultrasound (20 min at 41 degrees C) both caused a significant increase over controls (no ultrasound treatment) in R123 and DOX accumulation in the parent and MDR lines of MV522 and KB cells. Ultrasound also substantially increased the antiproliferative effects of DOX in both the parent and MDR variants of MV522 and KB cell lines when compared with controls. Our results also indicated that ultrasound exerted a much greater effect on cellular accumulation of R123 and DOX and cytotoxicity enhancement of DOX in the MDR variants than putative P-gp antagonist such as verapamil. CONCLUSION: The present results point to the potential use of ultrasound-induced hyperthermia as a much safer alternative to P-gp antagonist for reversal of MDR.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Chemical carboxyl-terminal sequence analysis of peptides and proteins using tribenzylsilyl isothiocyanate.

A new derivatization reagent, tribenzylsilyl isothiocyanate (TBS-ITC), is applied to C-terminal peptide and protein sequencing. It has been successfully used to sequence six C-terminal residues of house apomyoglobin and a synthetic peptide at low nanomole levels. The chemistry involves activation with acetic anhydride, derivatization with TBS-ITC, and cleavage of derivatized C-terminal amino acid thiohydantoin with sodium hydroxide. The tribenzylsilyl is a bulky, electric donor group and is a good leaving group. It facilitates the nucleophilic attack of the NCS(-1) in the coupling reaction. The efficiency for C-terminal sequencing by TBS-ITC is about the same as that of acetyl isothiocyanate (AITC), which is a derivatizing reagent for C-terminal sequencing developed by our laboratory. TBS-ITC is much more stable than AITC and trimethylsilyl isothiocyanate (TMS-ITC). TBS-ITC is a solid with relatively long shelf life, whereas AITC and TMS-ITC are liquid and not stable at room temperature.

Amino Acid Sequence↗
PubMed2001

Environmental regulation of recA gene expression in Porphyromonas gingivalis.

The recA gene product in Porphyromonas gingivalis is involved in DNA repair. Further, disruption of this gene can affect the proteolytic activity and expression of other virulence factors in this organism. Since several known environmental factors can influence virulence gene expression in P. gingivalis, we investigated the influence of these signals on the expression of the recA gene in this organism. A heterodiploid strain of P. gingivalis (designated FLL118) containing a transcriptional fusion of the recA promoter region and the promoterless tetracycline-resistant gene [tetA(Q)2] and xylosidase/arabinosidase (xa) gene cassette was constructed. The recA promoter activity was assessed by measurement of xylosidase activity in FLL118. The expression remained relatively constant during different growth phases, at different pH levels and in the presence of DNA-damaging agents. In response to hemin limitation and in the presence of calcium there was a moderate increase in recA promoter activity. Temperature also affected the expression. The highest level of xylosidase activity was observed in cultures at 32 degrees C with a decline of approximately 46% as growth temperature increased to 41 degrees C. Reverse transcriptase polymerase chain reaction analysis revealed that this regulation may be occurring at the transcriptional level. These results suggest that expression of the recA gene in P. gingivalis W83 is responsive to several environmental signals but is not regulated by a DNA damage-inducible SOS-like regulatory system.

Calcium↗
PubMed2001

The recA gene in Porphyromonas gingivalis is expressed during infection of the murine host.

The recA gene in Porphyromonas gingivalis is involved in DNA repair. To further elucidate the importance of the recA locus in the pathogenesis of P. gingivalis, we assessed its ability for expression in an animal host. The promoterless xa-tetA(Q)2 cassette was used in heterodiploid mutants to study recA promoter activity during infection. P. gingivalis FLL118.1 had the xa-tetA(Q)2 cassette under the control of recA promoter whereas P. gingivalis FLL119 had the cassette in the opposite orientation. xa encodes a bifunctional xylosidase/arabinosidase enzyme (XA) and the tetA(Q)2 gene product confers tetracycline resistance. Intramuscular infection in a mouse model allowed the recovery of the bacteria from inguinal lymph nodes. Infusion of tetracycline in the animals permitted the enrichment P. gingivalis FLL118.1 over the wild-type strain, during a mixed infection. The xylosidase activity of FLL118.1 could be detected on agar plates in the presence of 5-methylumbellifiry-beta-D-xyloside. No such enrichment for xylosidase activity was detected when the mixture of P. gingivalis W83 and P. gingivalis FLL119 was used to infect the mouse or cultured in vitro. These results indicated that recA promoter was transcriptionally active during the infection of the murine host and further support the importance of this locus during the P. gingivalis infection process.

Animals↗
PubMed2001

Vasopressin in the lateral septum regulates pair bond formation in male prairie voles (Microtus ochrogaster).

Male prairie voles (Microtus ochrogaster) form a pair bond with a female partner after mating, and this behavior is regulated by the neuropeptide vasopressin (AVP). The authors report that AVP in the lateral septum is important for pair bond formation. Administration of an AVP V1a receptor antagonist in the lateral septum blocked mating-induced pair bonding, whereas administration of AVP induced this behavior in the absence of mating. In addition, administration of an oxytocin (OT) receptor antagonist in the lateral septum also blocked pair bond formation induced by either mating or AVP administration, suggesting that the OT receptor blockade may have interfered with the AVP regulation of behavior. Together, these data provide evidence suggesting that AVP in the lateral septum regulates pair bond formation in male prairie voles and that this process requires access to both AVP and OT receptors.

Animals↗
PubMed2001

A domain-swapped RNase A dimer with implications for amyloid formation.

Bovine pancreatic ribonuclease (RNase A) forms two types of dimers (a major and a minor component) upon concentration in mild acid. These two dimers exhibit different biophysical and biochemical properties. Earlier we reported that the minor dimer forms by swapping its N-terminal alpha-helix with that of an identical molecule. Here we find that the major dimer forms by swapping its C-terminal beta-strand, thus revealing the first example of three-dimensional (3D) domain swapping taking place in different parts of the same protein. This feature permits RNase A to form tightly bonded higher oligomers. The hinge loop of the major dimer, connecting the swapped beta-strand to the protein core, resembles a short segment of the polar zipper proposed by Perutz and suggests a model for aggregate formation by 3D domain swapping with a polar zipper.

Animals↗
PubMed2001

Microtubule-associated protein-2: a new sensitive and specific marker for pulmonary carcinoid tumor and small cell carcinoma.

Microtubule-associated proteins (MAPs) are a major component of cytoskeleton family proteins associated with microtubule assembly. MAP-2 has been shown to be specifically expressed in neuronally differentiated cells. Pulmonary neuroendocrine carcinomas such as carcinoid tumors and small cell carcinomas are derived from neuroendocrine cells. We hypothesize that neuroendocrine cells may also express MAP-2, and therefore, MAP-2 may be used as a marker for pulmonary carcinomas of neuroendocrine differentiation. To investigate the utility of using MAP-2 expression to separate pulmonary neuroendocrine from non-neuroendocrine tumors, we examined the expression of MAP-2 immunohistochemically in 100 cases of pulmonary carcinomas. The immunoperoxidase method with antigen retrieval was used to characterize the expression of MAP-2, chromogranin, synaptophysin, and neuron-specific enolase in 25 small cell carcinomas, 25 carcinoid tumors, 25 adenocarcinomas, and 25 squamous cell carcinomas. All tumors were lung primaries. All 25 cases of carcinoid tumors (100%) as well as 23 of 25 cases (92%) of small cell carcinomas were positive for MAP-2. Four of 25 cases (16%) of adenocarcinomas were positive for MAP-2 and synaptophysin. Among the 25 squamous carcinomas, 4 cases (16%) were positive for MAP-2, 2 cases (8%) were positive for synaptophysin, 11 cases (44%) were positive for neuron-specific enolase, and none was positive for chromogranin. In conclusion, MAP-2 is a new sensitive and specific marker for the pulmonary tumors of neuroendocrine differentiation. We recommend that MAP-2 be added to immunohistochemical panels to separate non-neuroendocrine from neuroendocrine lung tumors.

Biomarkers, Tumor↗
PubMed2001

Timing of cyclin D1 expression within G1 phase is controlled by Rho.

The expression of cyclin D1 in mid-G1 phase is associated with sustained ERK activity, and we show here that Rho is required for the sustained ERK signal. However, we also report that Rho inhibits an alternative Rac/Cdc42-dependent pathway, which results in a strikingly early G1-phase expression of cyclin D1. Thus, cyclin D1 is induced in mid-G1 phase because a Rho switch couples its expression to sustained ERK activity rather than Rac and Cdc42. Our results show that Rho is crucial for maintaining the correct timing of cyclin D1 expression in G1 phase and describe a new role for cytoskeletal integrity in the regulation of cell cycle progression.

3T3 Cells↗
PubMed2001

A herpes simplex virus type 1 mutant deleted for gamma34.5 and LAT kills glioma cells in vitro and is inhibited for in vivo reactivation.

To create an oncolytic herpes simplex virus type 1 (HSV-1) that is inhibited for reactivation, we constructed a novel herpes recombinant virus with deletions in the gamma34.5 and LAT genes. The LAT gene was replaced by the gene for green fluorescent protein, thereby allowing viral infection to be followed. This virus, designated DM33, is effective in killing primary and established human glioma cell lines in culture. DM33 is considerably less virulent following intracerebral inoculation of HSV-susceptible BALB/c mice than the wild-type HSV-1 strain McKrae. The safety of this virus is further supported by the retention of its sensitivity to ganciclovir and its relatively limited toxicity against cultured human neuronal cells, astrocytes, and endothelial cells. The ability of DM33 to spontaneously reactivate was tested in a rabbit ocular infection model that accurately depicts human herpes infection and reactivation. Following ocular infection of rabbits, spontaneous reactivation was detected in 83% (15/18) of the eyes infected with wild-type McKrae. In contrast, none of the eyes infected with DM33 had detectable reactivation. The efficacy of this virus in cultured human glioma cell lines, its safety, confirmed by its inability to reactivate, and its attenuated neurovirulence make DM33 a promising oncolytic agent for tumor therapy.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Rapid induction of cytotoxic T-cell response against cervical cancer cells by human papillomavirus type 16 E6 antigen gene delivery into human dendritic cells by an adeno-associated virus vector.

We have shown that the pulsing of dendritic cells (DCs) with human papillomavirus type 16 (HPV-16) antigen proteins by lipofection stimulates class I-restricted cytotoxic T lymphocyte (CTL) response against primary cervical cancer cells. Also, we have shown that adeno-associated virus (AAV) was able to effectively deliver a cytokine gene into DCs. It has been our hypothesis that the delivery of antigen genes into DCs, resulting in endogenous and continuous antigen protein expression, may result in an improvement in T-cell priming by DCs. Here, DCs are pulsed (infected) with an AAV vector containing the HPV-16 E6 gene. After infection, transduced E6 gene mRNA expression and vector chromosomal integration could be identified in infected DCs. Furthermore, priming rosettes formed at early times when the AAV/E6 vector was used. Most importantly, AAV/E6 vector pulsing of DCs induced, after only 7 days of priming, a strong CTL response against primary cervical cancer cell lines, compared to bacterial E6 protein lipofection. Killing was significantly blocked by the addition of anti-MHC class I antibodies. Fluorescence-activated cell sorter (FACS) analysis of resulting primed cell populations revealed higher levels of CD8+ T cells by AAV-based pulsing, with little evidence of CD56 (NK). FACS analysis of the DC populations revealed that AAV/E6 vector-pulsed DCs had higher levels of CD80 and lower levels of CD86 than protein-pulsed DCs. These data suggest that rAAV may be appropriate for antigen pulsing of DCs for immunotherapy protocols. Finally, our protocol represents an advance in regards to the time needed for generating a CTL response compared to other techniques.

Cytotoxicity, Immunologic↗
PubMed2001

Systemic administration of naked plasmid encoding hepatocyte growth factor ameliorates chronic renal fibrosis in mice.

The progression of chronic renal diseases is considered as an irreversible process that eventually leads to end-stage renal failure characterized by extensive tissue fibrosis. At present, chronic renal fibrosis is incurable and the incidence of affected patients is on the rise worldwide. In this study, we demonstrate that delivery of hepatocyte growth factor (HGF) gene via systemic administration of naked plasmid vector markedly ameliorated renal fibrosis in an animal model of chronic renal disease induced by unilateral ureteral obstruction. A high level of exogenous HGF protein was detected in the obstructed kidneys following intravenous injection of naked plasmid encoding human HGF. Delivery of human HGF gene induced a sustained activation of extracellular signal-regulated kinases-1 and -2 in the obstructed kidneys. Exogenous HGF expression dramatically inhibited alpha-smooth muscle actin expression, attenuated renal interstitial accumulation and deposition of collagen I and fibronectin. In addition, exogenous HGF suppressed renal expression of pro-fibrogenic cytokine TGF-beta1 and its type I receptor in vivo. These results suggest that systemic administration of naked plasmid vector introduces a high level of exogenous HGF to the diseased kidneys, and that HGF gene transfer may provide a novel therapeutic strategy for amelioration of chronic renal fibrosis in vivo.

Actins↗
PubMed2001

Obesity, body fat distribution and coronary atherosclerosis among Japanese men and women.

OBJECTIVE: To investigate the relation of the obesity and body-fat distribution with angiographically defined coronary atherosclerosis. DESIGN: Cross-sectional study in a clinical setting. SUBJECTS: Three hundred and twenty men (median age, 59 y) and 212 women (median age, 67 y) who underwent coronary angiography for suspected or known coronary heart disease at 5 cardiology departments between September 1996 and August 1997. Patients with disease duration >1 y were excluded. MEASUREMENTS: The body mass index (BMI) and the waist to hip circumference ratio (WHR) were used as main exposure variables, and either the presence of significant coronary stenosis or the Gensini's score (> or =10 vs<10) as an outcome variable, in a sex-specific multiple logistic regression analysis controlling for age, hospital, and other coronary risk factors. RESULTS: Among male patients, BMI was progressively higher with an increasing number of vessels involved (P trend=0.05); the adjusted odds ratios for the presence of significant stenosis across quartiles of BMI were 1.0 (reference), 1.1, 1.9 and 2.5 (P trend=0.02), and the positive association was more pronounced for younger patients. Among females, however, such associations were not evident. Employing the Gensini's score as an outcome gave similar results. WHR was not significantly associated with either outcome regardless of sex. CONCLUSION: These results suggested that BMI was predictive of coronary stenosis among male patients, but not among female patients. Unlike most previous studies, this study failed to detect a positive association with WHR.

Adipose Tissue↗
PubMed2001

Construction and application of phenytoin anion-selective electrode based on bulk acoustic wave (BAW) sensing technique.

This paper describes the construction of an anion-selective bulk acoustic wave (BAW) sensor for the direct determination of phenytoin sodium for the first time. Based on the sensitive mass response of a piezoelectric quartz crystal (PQC) and selective adsorption-desorption across the modified film, the BAW sensor was fabricated by coating a polyvinylchloride (PVC) film containing activator on one side of a PQC. The method was found to be sensitive, rapid and easy to handle without pretreatment of the sample. The logarithm of the frequency shift of the PQC shows a linear relationship to the logarithm of the concentration of phenytoin over the range 6.7 x 10(-8)-8.0 x 10(-4) M with a detection limit of 1.0 x 10(-8) M at pH 10.0. Recoveries were in the range 98.5-102.0%. Influencing factors were examined and optimized. Also discussed is the preliminary application of the phenytoin BAW sensor in serum and injection. The results for real samples obtained by the proposed method agreed with those obtained by conventional methods.

Anions↗
PubMed2001

Conductivity detection for monitoring mixing reactions in microfluidic devices.

A conductivity detector was coupled to poly(dimethylsiloxane)-glass capillary electrophoresis microchips to monitor microfluidic flow. Electroosmotic flow was investigated with both conductivity detection (CD) and the current monitoring method. No significant variation was observed between these methods, but CD showed a lower relative standard deviation. Gradient mixing experiments were employed to investigate the relationship between the electrolyte conductivity and the electrolyte concentration. A good linear response of conductivity to concentration was obtained for solutions whose difference in concentrations were less than 27 mM. The new system holds great promise for precision mixing in microfluidic devices using electrically driven flows.

Journal Article↗
PubMed2001

Cyclodextrin derivative-coated quartz crystal microbalances for alcohol sensing and application as methanol sensors.

Three novel cyclodextrin derivatives, mono(6-benzylimino-6-deoxy)-beta-cyclodextrin (2), mono-(6-cyclohexylamino-6-deoxy)-beta-cyclodextrin (3) and mono(6-benzylamino-6-deoxy)-beta-cyclodextrin (4), together with mono(6-phenylamino-6-deoxy)-beta-cyclodextrin (1), were synthesized and employed as sensing materials coated on quartz crystal microbalances (QCMs). Comparison of the responses to some alcohol and solvent vapours such as methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, acetone, chloroform and benzene indicated that these beta-cyclodextrin derivatives show considerable sensitivity and selectivity towards methanol. It shows a good linear relationship between the frequency shift and the methanol concentration in the range 3-160 mg L(-1) for 2-4 and 3-140 mg L(-1) for 1. The correlation coefficients are 0.9971, 0.9983, 0.9973 and 0.9977, respectively. The limit of detection (LOD) is 0.2 mg L(-1). When small amounts of other vapours co-exist, e.g., ethanol, propan-1-ol and acetone, the responses differ from that of pure methanol vapour, and a deduction method could eliminate this cross-sensitivity. The water cross-sensitivity was very low. These QCMs coated with cyclodextrin derivatives are employed as methanol sensors in the real atmosphere to detect on-line the concentration of methanol vapour.

Air Pollutants, Occupational↗
PubMed2001

Atrichia caused by mutations in the vitamin D receptor gene is a phenocopy of generalized atrichia caused by mutations in the hairless gene.

Generalized atrichia with papules is a rare disorder characterized by loss of hair shortly after birth and development of cutaneous cysts. Mutations in the hairless gene (HR) cause this phenotype in both mouse and human. Here we present a case of atrichia with papules in a patient with a normal HAIRLESS gene but with mutations in both alleles of the VITAMIN D RECEPTOR. The patient exhibited vitamin D resistant rickets, which was confirmed by an absent response of her fibroblasts to 1,25-dihydroxyvitamin D3 in vitro. Similar to individuals with HAIRLESS mutations, her skin showed an absence of normal hair follicles and the presence of follicular remnants and cysts. The cyst epithelium contained keratin-15- and keratin-17-positive cells suggesting derivation from the hair follicle bulge and the presence of epithelial stem cells. Although hair loss has been reported in association with hereditary vitamin D resistant rickets, we now characterize this alopecia as clinically and pathologically indistinguishable from generalized atrichia with papules, which was previously thought to be caused only by mutations in HAIRLESS. These findings suggest that VDR and HR, which are both zinc finger proteins, may be in the same genetic pathway that controls postnatal cycling of the hair follicle.

Alopecia↗