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Y Huang

Publications and source records attributed to Y Huang.

At least 865 records · Page 48Linked to original sources
PubMed1996

In-vitro metabolic interaction of bunitrolol enantiomers in rabbit liver microsomes.

We have examined the 4-hydroxylation of bunitrolol in rabbit and rat liver microsomes. Significant species differences (rabbit < rat of both sexes) and sex (male > female of both species) were observed in the formation of 4-hydroxybunitrolol from racemic bunitrolol (10 microM). The 4-hydroxylation of bunitrolol racemate and enantiomers showed biphasic kinetics, a low-Km system and a high-Km system, in liver microsomes from rabbits of both sexes. There were significant differences in Km and Vmax values [(+) > (-)] for 4-hydroxylations of (+)-bunitrolol and (-)-bunitrolol in the low-K(m) system. Furthermore, the rate of clearance (Vmax/Km) was 20- to 200-fold for the low-Km system compared with the high-Km system, indicating that enzymes in the low-Km system play a major part in the rabbit liver microsomal bunitrolol metabolism. Inhibition studies using cytochrome P450 inhibitors such as quinidine, quinine, and alpha-naphthoflavone or polyclonal antibodies raised against rat P450-2D and -1A enzymes did not make clear which P450 enzymes are involved in bunitrolol 4-hydroxylation in rabbit liver microsomes. The 4-hydroxylase activity of (+)-bunitrolol was slightly higher than that of (-)-bunitrolol in separated incubations containing male rabbit liver microsomes and an enantiomer concentration of 10 microM. However, the 4-hydroxylation of (+)-bunitrolol (10 microM) was markedly suppressed in the presence of its antipode (10 microM), whereas (-)-bunitrolol 4-hydroxylation was not affected by the presence of its antipode, resulting in a change of the stereoselectivity from (+) > (-) for enantiomer to (+) < (-) for racemate. The difference in the Michaelis constants in the low-Km system, where the Km value of (-)-bunitrolol is one-eighth that of (+)-bunitrolol, is thought to cause the change in the stereoselectivity in rabbit liver microsome-mediated bunitrolol 4-hydroxylation.

Adrenergic beta-Antagonists↗
PubMed1996

Herpes simplex virus type 2 inhibition of Fas ligand expression.

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) are common human pathogens. In this report we demonstrate the capacity of HSV-2, but not HSV-1, to inhibit the activity and cell surface expression of Fas ligand, an important molecule involved in T-cell apoptosis and cell-mediated cytotoxicity. Cells infected with HSV-2 retained Fas ligand intracellularly instead of expressing it on the cell surface. Addition of anti-Fas antibodies markedly inhibited HSV-2 viral production, suggesting that the capacity of the virus to regulate Fas ligand expression, and thereby programmed cell death, may represent a powerful mechanism for the virus to enhance viral replication.

Animals↗
PubMed1996

Effects of modifying the tRNA(3Lys) anticodon on the initiation of human immunodeficiency virus type 1 reverse transcription.

tRNA(3Lys) is a primer for reverse transcription in human immunodeficiency virus type 1 (HIV-1), and the anticodon of tRNA(3Lys) has been implicated in playing a role in both its placement onto the HIV-1 genome and its interaction with HIV-1 reverse transcriptase (RT). In this work, the anticodon in a tRNA(3Lys) gene was changed from UUU to CUA (tRNA(3Lys)Su+) or, in addition, G-73 was altered to A (tRNA(3Lys)Su+G73A). COS-7 cells were transfected with either wild-type or mutant tRNA(3Lys) genes, and both the wild-type and mutant tRNA(3Lys) produced were purified by using immobilized tRNA-specific hybridization probes. Each mutant tRNA(3Lys) was tested for its ability to prime reverse transcription in vitro, either alone or in competition with wild-type tRNA(3Lys). Short RT extensions of wild-type and mutant tRNALys could be distinguished from each other by their different mobilities in one-dimensional single-stranded conformation polymorphism polyacrylamide gel electrophoresis. These reverse transcription products show that heat-annealed tRNA(3Lys)Su+ has the same ability as heat-annealed wild-type tRNA(3Lys) to prime RT and competes equally well with wild-type tRNA(3Lys) for priming RT. tRNA(3Lys)Su+G73A has 60% of the wild-type ability to prime RT but competes poorly with wild-type tRNA(3Lys) for priming RT. However, the priming abilities of wild-type and mutant tRNA(3) are quite different when in vivo-placed tRNA is examined. HIV-1 produced in COS cells transfected with a plasmid containing both the HIV-1 proviral DNA and DNA coding for tRNA(3Lys)Su+ contains both endogenous, cellular wild-type tRNA(3Lys) and mutant tRNA(3Lys). When total viral RNA is used as the source of primer tRNA placed onto the genomic RNA in vivo, only wild-type tRNA(3Lys) is used as a primer. If the total viral RNA is first heated and exposed to hybridizing conditions, then both the wild-type and mutant tRNA(3Lys) act as primers for RT. These results indicate that the tRNA(3Lys)Su+ packaged into the virions is unable to act as a primer for RT, and a model is proposed to explain the disparate results between heat-annealed and in vivo-placed primer tRNA.

Anticodon↗
PubMed1996

The role of interleukin-10 in the inhibition of T-cell proliferation and apoptosis mediated by parainfluenza virus type 3.

We have previously demonstrated that parainfluenza virus type 3 (PIV3), a significant respiratory pathogen, can markedly inhibit T-cell function in vitro. We now report that the virus potently induces interleukin-10 (IL-10) production by peripheral blood mononuclear cells. The IL-10 produced contributes to viral inhibition of T-cell proliferation and protects T cells from PIV3-mediated apoptosis. These findings suggest that IL-10 is likely to play an important immunoregulatory role in PIV3 infections.

Adult↗
PubMed1996

A suboptimal 5' splice site is a cis-acting determinant of nuclear export of polyomavirus late mRNAs.

Mouse polyomavirus has been used as a model system to study nucleocytoplasmic transport of mRNA. Three late mRNAs encoding the viral capsid proteins are generated by alternative splicing from common pre-mRNA molecules. mRNAs encoding the virion protein VP2 (mVP2) harbor an unused 5' splice site, and more than half of them remain fully unspliced yet are able to enter the cytoplasm for translation. Examination of the intracellular distribution of late viral mRNAs revealed, however, that mVP2 molecules are exported less efficiently than are mVP1 and mVP3, in which the 5' splice site has been removed by splicing. Point mutations and deletion analyses demonstrated that the efficiency of mVP2 export is inversely correlated with the strength of the 5' splice site and that unused 3' splice sites present in the mRNA have little or no effect on export. These results suggest that the unused 5' splice site is a key player in mVP2 export. Interestingly, mRNAs carrying large deletions but retaining the 5' splice site exhibited a wild-type mVP2 export phenotype, suggesting that there are no other constitutive cis-acting sequences involved in mVP2 export. RNA stability measurements confirmed that the subcellular distribution differences between these mRNAs were not due to differential half-lives between the two cellular compartments. We therefore conclude that the nuclear export of mVP2 is strongly influenced by a suboptimal 5' splice site. Furthermore, results comparing spliced and unspliced forms of mVP2 molecules indicated that the process of splicing does not enhance nuclear export. Since mVP2 and some of its mutant forms can accumulate in the cytoplasm in the absence of splicing, we propose that splicing is not a prerequisite for mRNA export in the polyomavirus system; rather, removal of splicing machinery from mRNAs may be required. The possibility that export of other viral mRNAs can be influenced by suboptimal splicing signals is also discussed.

3T3 Cells↗
PubMed1996

Role of polyadenylation in nucleocytoplasmic transport of mRNA.

To examine the role of polyadenylation in the nuclear export of mRNA, we have replaced the poly(A) signal in a Rev-responsive human immunodeficiency virus type 1-based reporter gene with a cis-acting hammerhead ribozyme. Transcripts from this gene thus acquire a 3' terminus by cis-ribozyme cleavage rather than by polyadenylation. The nuclear and cytoplasmic distribution of transcripts was investigated using transient gene expression and quantitative RNase protection assays. In the absence of Rev, a basal level of polyadenylated unspliced mRNA transcribed from a poly(A) signal-containing control reporter gene was detected in the cytoplasm of transfected COS7 cells. However, cytoplasmic ribozyme-cleaved unspliced RNA was only barely detectable. The nuclear/cytoplasmic (n/c) ratio of polyadenylated RNAs was 3.8, while the n/c ratio for ribozyme cis-cleaved RNAs was 33. The cytoplasmic localization of the polyadenylated unspliced mRNA was enhanced about 10-fold in the presence of Rev and the Rev-responsive element. In marked contrast to this, ribozyme cleaved RNA accumulated almost exclusively (n/c ratio of 28) in the nucleus in the presence of Rev. Actinomycin D time course analysis suggested that the low levels of the cytoplasmic ribozyme-cleaved RNAs in both the presence and absence of Rev were due to serve export deficiency of ribozyme-cleaved RNA. Finally, by inserting a 90-nucleotide poly(A) stretch directly upstream of the ribozyme cassette, we have demonstrated that a long stretch of poly(A) near the 3' end of a ribozyme-cleaved transcript is not sufficient for directing mRNA export. Taken together, these results suggest that polyadenylation is required for the nucleocytoplasmic transport of mRNA and that Rev interaction with the Rev-responsive element cannot bypass this requirement.

Base Sequence↗
PubMed1996

Hematopoietic bone marrow hyperplasia: correlation of spinal MR findings, hematologic parameters, and bone mineral density in endurance athletes.

PURPOSE: To determine the frequency of hematopoietic hyperplasia on spinal magnetic resonance (MR) images in endurance athletes and to correlate MR alterations with clinical parameters. MATERIALS AND METHODS: In 15 endurance athletes, MR images of the lumbar spine were analyzed for hematopoietic hyperplasia; vertebral T1 and T2 were determined. Bone mineral density (BMD) was determined, blood tests were performed, and maximum oxygen consumption (VO2max) was measured. RESULTS: Nine subjects showed evidence of hematopoietic hyperplasia: Eight showed T1 prolongation, and six had patchy or diffuse T1 hypointensity. No definite correlation existed between hematopoietic hyperplasia and duration of training, hematologic results, or VO2max levels. Borderline significance existed between hematopoietic hyperplasia and anemia (P = .103) and intensity of training (P = .09). BMD had no statistically significant effect on T1. CONCLUSION: Changes in BMD do not appear to contribute to MR marrow changes that are consistent with hematopoietic hyperplasia. Depleted iron reserves or increased hematopoiesis probably contribute to hematopoietic hyperplasia in endurance athletes.

Adult↗
PubMed1996

Elevation of amino acids in the interstitial space of the rat brain following infusion of large neutral amino and keto acids by microdialysis: leucine infusion.

A microenvironment similar to that found in maple syrup urine disease was created in the brain of free-moving, awake rats by the infusion of leucine into the brain using microdialysis. To determine the effects on amino acid homeostasis the eluate of the probe was analyzed. Perfusion with leucine elevated the interstitial levels of large neutral amino acids suggesting hetero exchange of large neutral amino acids from neuronal cells into the interstitial space. The data also demonstrated the inter relationship of leucine and glutamine, both of which may be nitrogen sinks in the brain. Elevation of large neutral amino acids in the interstitial space suggests a decreased concentration in neurons which might have an effect on the synthesis of serotonin and catecholamines and suggests a mechanism by which elevated leucine may affect neuronal function in maple syrup urine disease.

Amino Acids↗
PubMed1996

Elevation of amino acids in the interstitial space of the rat brain following infusion of large neutral amino and keto acids by microdialysis: alpha-ketoisocaproate infusion.

alpha-Ketoisocaproate was infused into the brain of free-moving, awake rats by microdialysis to create a microenvironment similar to that found in maple syrup urine disease. The eluate of the probe was analyzed for amino acids to determine if alpha-ketoisocaproate was transaminated to leucine and if the amino acid homeostasis was altered. The interstitial levels of leucine were increased up to 11-fold and other large neutral amino acids were increased 2- to 3-fold indicating an active branched chain keto acid transaminase activity and enhanced hetero-exchange across cell membranes. The elevation of large neutral amino acids in the interstitial space is discussed in terms of the synthesis of leucine and neurotransmitters in maple syrup urine disease.

Amino Acids↗
PubMed1996

p53 nuclear protein overexpression in colorectal cancer: a dominant predictor of survival in patients with advanced hepatic metastases.

PURPOSE: To determine whether p53 protein expression is similar within primary colorectal cancer (CRC) and synchronous regional and distant metastases and to assess whether p53 nuclear protein expression could predict outcome in patients with synchronous unresectable liver metastases treated by hepatic artery infusional (HAI) chemotherapy. MATERIALS AND METHODS: Paraffin sections from tumor and corresponding normal mucosa representative of 50 consecutive advanced CRC cases were examined for p53 nuclear protein expression by immunohistochemistry using the monoclonal antibody PAb 1801. Patterns of p53 nuclear expression were correlated with standard clinicopathologic variables and outcome, including response to HAI and survival. In a subset analysis, the pattern of nuclear p53 immunoreactivity was compared between primary CRC and lymph node and liver metastases. RESULTS: Positive nuclear immunoreactivity for p53 protein was found in 72% of cases. The pattern of p53 protein expression in lymph node and liver metastases was identical to that of the primary tumor. The median survival time was 21.0 months in patients with p53-positive tumors and 53.2 months in patients with p53-negative tumors (Wilcoxon test P = .038). Two-year survival rates were 41.7% and 78.6%, respectively (P < .01). No significant difference was found in the response rates to HAI chemotherapy between the two groups. By multivariate analysis, p53 protein status was the single best predictor of survival, with a relative risk of 6.312. CONCLUSION: Our results indicate that nuclear p53 protein status in primary CRC is similar to that in metastatic sites and may be the dominant predictor of survival in patients with advanced hepatic metastases.

Adult↗
PubMed1996

Prediction of colorectal cancer relapse and survival via tissue RNA levels of matrix metalloproteinase-9.

PURPOSE: In this study, we investigated the association between matrix metalloproteinase (MMP)-9 RNA expression in primary colorectal cancer (CRC) and standard clinicopathologic variables and determined whether levels of MMP-9 RNA predict relapse and survival. PATIENTS AND METHODS: Tumor and paired normal mucosa specimens from 71 primary CRC patients following resections were assessed. RNA levels were determined via Northern blot hybridization and quantitated with laser densitometry. Results were expressed as tumor/normal mucosa (T/N) fold-increase calculated after normalizing for RNA loading using 28S expression. Statistical analysis was performed using the SAS statistical package procedure. Kaplan-Meier survival curves were compared with the two-sided log-rank test. RESULTS: The mean T/N MMP-9 RNA fold-increase was 9.4 +/- 1.0 (mean +/- SE) (P < .001). Overexpression of MMP-9 RNA correlated significantly with status of synchronous distant metastases (M stage) (P = .004) and Dukes' stage (P = .008). A T/N fold-increase of 5.0 was used to discriminate between high (> 5.0) and low (< or = 5.0) T/N MMP-9 expression. High T/N MMP-9 RNA expression was associated with a significantly shorter disease-free (P = .0001) and overall (P = .0002) survival duration. In univariate and multivariate analyses, T/N MMP-9 RNA level was found to be an independent prognostic factor for disease-free survival. CONCLUSION: This report provides the first evidence that increased MMP-9 RNA production in primary human CRC may be a powerful, independent predictor of recurrence and outcome.

Adult↗
PubMed1996

Irinotecan is an active agent in untreated patients with metastatic colorectal cancer.

PURPOSE: To determine the response rate, survival, and toxicity of the new anticancer agent, irinotecan (CPT-11), in the treatment of metastatic colorectal cancer. PATIENTS AND METHODS: Forty-one chemotherapy-naive patients with measurable metastatic colorectal cancer were treated with a 90-minute infusion of irinotecan 125 mg/m2 administered weekly for 4 weeks every 6 weeks. Pretreatment tumor biopsies to assess topoisomerase-I (Topo-I) activity were obtained from 11 patients. The pharmacokinetics for irinotecan and its active metabolite, SN-38, were determined in 18 patients. RESULTS: Thirteen of 41 patients (32%) had a partial response (PR; 95% confidence interval, 18% to 46%). The median response duration was 8.1 months (range, 4.0 to 16.0) and the median survival time was 12.1 months (range, 2.1 to 21.7) for all 41 patients. Grade 3 or 4 toxicities were diarrhea (29% of patients) and neutropenia (22% of patients). Grade 3 or 4 diarrhea was substantially more prevalent in the initial 18 patients on study, with an incidence rate of 56%; a significant reduction in the incidence of severe diarrhea to 9% was noted with strict adherence to an antidiarrheal regimen of loperamide and diphenyldramine. No correlations were seen between pharmacokinetics of irinotecan/SN-38 and the clinical parameters of response, survival, or incidence of diarrhea. CONCLUSIONS: Irinotecan has activity in the treatment of patients with metastatic colorectal cancer. Strict adherence to an antidiarrheal regimen of diphenhydramine/loperamide significantly reduced the incidence of diarrhea; the agent was thereafter well tolerated in the majority of patients.

Adult↗
PubMed1996

Neoadjuvant therapy of high-risk gastric cancer: a phase II trial of preoperative FAMTX and postoperative intraperitoneal fluorouracil-cisplatin plus intravenous fluorouracil.

PURPOSE AND METHODS: We identified patients with gastric cancer at high risk for recurrence before therapy using endoscopic ultrasonography (EUS). Neoadjuvant therapy using the fluorouracil, doxorubicin, and metrotrexate (FAMTX) regimen was given for three courses before planned laparotomy with the intention to perform curative resection. Postoperatively, intraperitoneal (IP) cisplatin and fluorouracil (FU) and intravenous (i.v.) FU were administered to patients undergoing resection. RESULTS: Fifty-six assessable patients were treated. Preoperative FAMTX therapy was tolerable, with the major toxicity being neutropenic fever. One treatment-related death was seen. Eighty-nine percent of patients underwent surgical exploration and 61% had potentially curative resections. There were two postoperative deaths. Comparison of pathologic tumor (pT) stage with EUS-predicted tumor stage showed apparent downstaging in 51% of patients. Postoperative IP chemotherapy was delivered to 75% of eligible patients. Toxicity was acceptable. There was no increase in operative morbidity or mortality compared with concurrent nonstudy patients undergoing a similar operative procedure and not receiving preoperative therapy. With a median follow-up time of 29 months, the median survival duration was 15.3 months. For patients who underwent potentially curative resections, the median survival duration was 31 months. Peritoneal failure was seen in 16% of patients. CONCLUSION: Chemotherapy with the FAMTX regimen is tolerable in patients with locally advanced gastric cancer, without an increase in operative morbidity or mortality. IP therapy can be successfully delivered to most resected patients. The intraabdominal failure pattern appears to be decreased compared with expected. This approach is an appropriate investigational arm to pursue in future studies.

Adenocarcinoma↗
PubMed1996

Differential effects of adrenocorticotropin in vivo on cytochromes P4502D16 and P450c17 in the guinea pig adrenal cortex.

Studies were performed to compare the effects of ACTH treatment in vivo on cytochromes P4502D16 and P450c17 in the guinea pig adrenal cortex. In untreated animals, CYP2D16 protein and messenger RNA (mRNA) expression as well as xenobiotic-metabolizing activities (bufuralol 1'-hydroxylase, benzphetamine N-demethylase, and benzo(a)pyrene hydroxylase) were far greater in the inner (zona reticularis) than the outer (zona fasciculata plus zona glomerulosa) zones of the cortex. ACTH treatment for 3 or 7 days significantly decreased the rates of xenobiotic metabolism in both the inner and outer adrenal zones. Western and Northern blot analyses revealed that adrenal CYP2D16 protein and mRNA concentrations were significantly decreased by ACTH. In contrast to its inhibitory effects on CYP2D16, ACTH treatment increased steroid 17 alpha-hydroxylase activity in the adrenal inner zone, but did not affect outer zone activity. Microsomal CYP17 protein concentrations were not affected by ACTH despite increases in CYP17 mRNA levels in both zones. The results indicate that ACTH causes down-regulation of adrenal CYP2D16, probably at the transcriptional level. Thus, modulation of CYP2D16 by ACTH is opposite that for the steroidogenic P450 isozymes, suggesting unique regulatory mechanisms. In addition, the data suggest that posttranscriptional mechanisms contribute to ACTH regulation of 17 alpha-hydroxylase activity in the guinea pig adrenal cortex.

Adrenal Cortex↗
PubMed1996

Undifferentiated cells in the developing Drosophila eye influence facet assembly and require the Fat facets ubiquitin-specific protease.

The Drosophila compound eye develops by a complex series of cell interactions where multiple positive and inhibitory cues guide cells in each facet into their positions and fates. The results of many genetic and molecular experiments have led to the view that facet assembly is directed by cells within developing ommatidial preclusters. Here fat facets mutants and the cloned fat facets gene were used to show that, in order to limit the number of photoreceptors in a facet to eight, undifferentiated cells surrounding assembling facets send an inhibitory signal to extraneous cells within the facet preclusters. Generation of the inhibitory signal requires the ubiquitin-specific protease encoded by the fat facets gene and is thus regulated by ubiquitin-dependent proteolysis.

Animals↗
PubMed1996

Antenatal assessment using the FECG obtained via abdominal electrodes.

During the past decade a variety of intrapartum fetal monitors have been constructed that process the entire fetal electrocardiogram (FECG), obtained via a scalp electrode. They therefore differ from conventional monitors in aiming to extract relevant timing and magnitude information from the morphology of the FECG rather than simply the RR interval and hence heart rate. An intrapartum monitor such as this has been successfully developed by ourselves. This paper describes the early results obtained whilst attempting to extend this form of monitoring forward into the antenatal period. In order to achieve this the FECG must be acquired via surface electrodes placed on the maternal abdomen, which yields a signal containing the FECG amidst a number of noise sources. Our investigations into the feasibility of "antenatal abdominal FECG analysis" have been on two fronts. The first has been to produce a bedside monitor similar in function to our intrapartum device, whilst the second has been to address the possibility of performing such monitoring in ambulant subjects. At present the antenatal bedside monitor has successfully extracted and processed the FECG in approximately 75% of the cases studied, with subjects ranging from 20 weeks through to term having been monitored. We also have demonstrated the feasibility of the long term monitoring of maternal and fetal heart rate using a portable instrument.

Abdomen↗
PubMed1996

Synthesis and hypolipidemic evaluation of beta-alkylaminopropiophenone and beta-alkylaminopropio-2'-naphthone derivatives in rodents.

A series of beta-alkylamino-(4'-alkyl)-propiophenone or beta-alkylamino(7'-methyl)-propio-2'-naphthone derivatives were prepared and found to have hypolipidemic activity by lowering both serum cholesterol and triglyceride levels in rodents. The electron donating substituent at the para position of the phenyl ring seems to decrease the hypolipidemic activity when compared to non-substituted or electron withdrawing group substituted analogs as investigated previously in this laboratory. In comparison with lovastatin or clofibrate, most of these analogs showed similar or higher activity in lowering both serum cholesterol or triglyceride levels. beta-Pyrrolidino-(4'-methyl)-propiophenone (1) demonstrated the best activity after 16 d, i.p. administration in mice at 8 mg/kg/d. Further detailed studies in rats indicated that beta-pyrrolidino-(4'-methyl)-propiophenone also showed decreased serum cholesterol and triglyceride levels with increased HDL-cholesterol and triglyceride levels after 14 d. In hyperlipidemic mice and rats, this compound was observed to be effective in lowering serum lipid levels as well as tissue lipid levels. The activities of hepatic acetyl CoA synthetase, phosphatidylate phosphohydrolase, and hepatic lipoprotein lipase were moderately inhibited by beta-pyrrolidino-(4'-methyl)-propiophenone.

Animals↗