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Biomedical subjects

T Liu

Publications and source records attributed to T Liu.

At least 325 records · Page 18Linked to original sources
PubMed1997

Localization of iodine-125-mIP-Des-Met14-bombesin (7-13)NH2 in ovarian carcinoma induced to express the gastrin releasing peptide receptor by adenoviral vector-mediated gene transfer.

UNLABELLED: The gastrin releasing peptide receptor (GRPr) has a high affinity for the 14 amino acid bombesin peptide. For this analysis, [125I]-Tyr4-bombesin was compared with [125I]-mIP-bombesin (a seven amino acid bombesin analog) for in vitro binding and internalization into tumor cells and for tumor localization in vivo. Also, a recombinant adenoviral vector (AdCMVGRPr) was used for gene transfer to induce the expression of GRPr in human ovarian cancer cells for binding and tumor localization with these radiolabeled peptides. METHODS: [125I]-mIP-bombesin was synthesized and compared with [125I]-Tyr4-bombesin in internalization assays using BNR-11 cells (mouse fibroblast cells stably transfected with GRPr) over a 24-hr period. In vitro binding assays used BNR-11, and A427, HeLa and SKOV3.ip1 human cancer cells, which were either uninfected or infected with AdCMVGRPr. Biodistribution studies were performed in normal BALB/c mice and in athymic nude mice bearing orthotopic SKOV3.ip1 ovarian cancer tumors. The SKOV3.ip1 tumors were induced to express GRPr with the AdCMVGRPr adenoviral vector. RESULTS: Internalization assays showed that [125I]-Tyr4-bombesin was rapidly internalized and catabolized at 37 degrees C with approximately 10% of the radioactivity remaining intracellularly at 4 hr, compared with approximately 30% with [125I]-mIP-bombesin. HeLa, A427 and SKOV3.ip1 cells were all induced to express levels of GRPr that were higher than those seen with the positive control BNR-11 cells. Normal mice showed a lower level of radioactivity in both the blood and thyroid for [125I]-mIP-bombesin [0.26% +/- 0.10% injected dose per gram (ID/g) and 0.24% +/- 0.05% ID] than for [125I]-Tyr4-bombesin (3.5% +/- 1.6% ID/g and 5.2% +/- 4.4% ID) at 4 hr postinjection. Mice bearing intraperitoneal (i.p.) SKOV3.ip1 tumors and given AdCMVGRPr i.p. 5 days after tumor cell inoculation followed by [125I]-mIP-bombesin i.p. at day 7 showed 16.5% +/- 4.8% ID/g in tumor compared with 5.9% +/- 3.0% ID/g with [125I]-Tyr4-bombesin at 4 hr postinjection. Tumor bearing mice given saline or a control adenovirus expressing the beta-galactosidase (LacZ) gene showed significantly lower tumor uptake values of both bombesin peptides. CONCLUSION: Internalization assays showed that [125I]-mIP-bombesin has favorable characteristics compared with [125I]-Tyr4-bombesin with regards to cellular internalization and retention. The results demonstrate successful in vitro and in vivo transduction of human tumor cells with a recombinant adenoviral vector-expressing GRPr. Additionally, tumors transduced in vivo to express GRPr demonstrated significantly greater localization of [125I]-mIP-bombesin when compared with [125I]-Tyr4-bombesin.

Adenoviridae↗
PubMed1997

Hemofiltration or hemodiafiltration with on-line production of substitution fluid: clinical observation of safety and effectiveness.

OBJECTIVE: To observe the safety and cardiovascular stability of on-line hemofiltration (HF) or hemodiafiltration (HDF) and evaluate the clinical effectiveness of one HF or HDF session in addition to two hemodialysis (HD) sessions weekly. METHODS: Forty patients were randomly divided into four groups: group predilutional (PRD) HF (filtration rate: 259-333 ml/min) group predilutional HDF (filtration rate: 167 ml/min) group postdilutional (POD) HDF (filtration rate: 83 ml/min) and group bicarbonate HD. The reduction rate of parathyroid hormone (PTH), beta 2-microglobulin (beta 2MG), alpha 1-microglobulin (alpha 1MG) and KT/V in the initial treatment of every month was observed, and the incidence of hypotension and pyretic reaction during each treatment was evaluated. RESULTS: After 4-month observation, the KT/V for Group POD HDF is better than that for the other three groups, and for Group PRD HDF is better than that for Group HF and HD. Serum level of PTH and beta 2MG was not decreased after every treatment in Group HD, and so was serum level of alpha 1MG in all groups. Significant removal of PTH and beta 2MG was observed in Group HF, PRD HDF and POD HDF. The monthly serum level of beta 2MG and KT/V were stable in all groups, but the monthly serum level of PTH tended to be decreased in Group HF, PRD, HDF, and POD HDF. The incidence of pyretic reaction in HF or HDF was the same as in HD. Although the ultrafiltration volume was significantly higher during HF or PRD HDF than during HD, the incidence of hypotension in HF or PRD HDF was similar to that in HD. CONCLUSIONS: On-line HF or HDF proved to be a safe and reliable method. POD HDF mode seems to have the best KT/V, HF or PRD HDF offers a better choice for preventing intradialytic hypotension. One HF or HDF session in addition to two HD sessions weekly is similarly effective to decrease the serum level of PTH and the proof of the clinical effectiveness of such a therapy awaits a long-term observation.

Adult↗
PubMed1996

Fidelity of translesional synthesis past benzo[a]pyrene diol epoxide-2'-deoxyguanosine DNA adducts: marked effects of host cell, sequence context, and chirality.

We have used a site-specific approach to investigate the mutagenic potential of (+)- and (-)-trans-anti-benzo[a]pyrene diol epoxide (BPDE) DNA adducts. Oligodeoxyribonucleotides (5'TCCTCCTG1G2-CCTCTC), modified at the exocyclic amino groups of G1 or G2, were incorporated into a single-stranded shuttle vector and introduced into Escherichia coli or simian kidney (COS) cells. This experimental system permits translesional synthesis to proceed in the absence of DNA repair. The presence of (+)- or (-)-BPDE-N2-dG adducts strongly inhibited translesional synthesis in E. coli; induction of cellular SOS functions reduced this blocking effect. Vectors containing (+)-BPDE adducts at G1 or G2 generated mutation frequencies of 19% and 3%, respectively; these values were not altered significantly by induction of SOS functions. In COS cells, (+)-BPDE-modified vectors generated mutation frequencies of 13% at G1 and 45% at G2. In E. coli, the (-)-BPDE adduct generated mutation frequencies of < or = 2% at G1 and G2 and, in COS cells, 13% at G1 and 21% at G2. The predominant mutations in E. coli and COS cells were G-->T transversions targeted to the site of the lesion; however, when G2 was modified, a significant number of targeted G-->A and G-->C mutations were observed in COS cells. We conclude from this study that (+)-and (-)-BPDE-N2-dG adducts pair preferentially to dCMP and dAMP during translesional synthesis in a process that is strongly influenced by the stereochemistry of the adduct, by the bases flanking the lesion, and by host cell factors.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

External glycopeptide binding to MHC class-I in relation to expression of TAP transporters, beta 2-microglobulin and to pH.

MHC class-I binding glycopeptides are easily visualized on the cell surface by carbohydrate specific monoclonal antibodies. By comparing the staining intensity between anti-carbohydrate and anti-MHC class-I specific monoclonal antibodies, an estimation of the fraction of peptide accessible 'empty' sites on the cell surface of MHC class-I molecules can be made. This system was used to analyze glycopeptide binding to MHC class-I molecules in relation to transporter associated with antigen processing (TAP) peptide transporters and beta 2-M expression, using gene targeted mice, and in relation to pH. Approximately 15, 40, and 95% 'empty' Db molecules were found on activated T cells from normal, beta 2-M-/- and TAP -/- mice, respectively. The ASN9-6h-Gal2 glycopeptide also bound to transfected 'empty' Db molecules on T1-Db, T2-Db and T3-Db cells with a preference for T2-Db cells, lacking TAP peptide transporters. The stability of glycopeptide binding to H-2Db is also highest on T2-Db cells. pH was found to influence binding either positively or negatively, using four different glycopeptides, binding either to Db or Kb. We conclude that external glycopeptide binding may reflect important functional properties in the MHC class-I system and that pH in different processing compartments might influence the expressed peptide repertoire.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Incorrect base insertion and prematurely terminated transcripts during T7 RNA polymerase transcription elongation past benzo[a]pyrenediol epoxide-modified DNA.

DNA replication and transcription are affected adversely by the presence of bulky adducts that are generated by the covalent binding of a variety of metabolically activated environmental pollutants to cellular DNA. When these lesions are not cleared by cellular repair enzymes prior to replication, mutations and ultimately tumor initiation can occur. Transcription and DNA repair appear to be intimately connected, since certain adducts are more efficiently removed from the transcribed strands of active loci than from non-transcribed strands and other quiescent domains in the genome. The mechanism by which RNA polymerases deal with bulky adducts during DNA transcription is therefore of great interest. The availability of site-specifically modified and stereochemically defined oligodeoxyribonucleotides derived from the covalent reaction of 7r, 8t-dihydroxy-9, 10t-epoxy- 7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) with guanine residues prompted us to study the efficiencies of transcription past these lesions using bacteriophage T7 RNA polymerase. We show here that T7 RNA polymerase can bypass such lesions in a DNA template, providing that a cytosine residue is incorporated opposite anti-BPDE-modified guanine. However, when an incorrect base (most frequently a purine) is inserted opposite the modified site, the RNA polymerase stalls, and the complex dissociates, resulting in a truncated transcript. The ability of the T7 RNA polymerase to discriminate between a correct and an incorrect inserted base and, accordingly, to continue or terminate transcription, might constitute an important mechanism that ensures the fidelity of transcription past a modified base present on the transcribed strand of the DNA template.

Bacteriophage T7↗
PubMed1996

A novel acidic allergen, Hev b 5, in latex. Purification, cloning and characterization.

Latex allergy is recognized as a serious health problem among health care workers and children with spina bifida. A number of IgE-reactive proteins have been identified in natural and processed latex products. One of the most acidic proteins in the cytoplasm of lacticifer cells of rubber trees (Hevea brasiliensis) is demonstrated to be a potent allergen in eliciting allergic reactions in humans. This protein, with pI = 3.5, has a molecular mass of 16 kDa with a blocked N terminus and an unusual amino acid composition. This acidic protein was found in extracts prepared from latex gloves, which were shown to be allergenic. The purified protein elicits histamine release from human basophils passively sensitized with serum from latex-allergic individuals in a dose-dependent manner. From a latex cDNA library, the cDNA coding for this protein was isolated and sequenced. The deduced amino acid sequence shows a high degree of homology to another acidic protein identified in kiwifruit (Actinidia deliciosa var. deliciosa). The sequence homology (47% sequence identity) between these two acidic proteins suggests a molecular explanation for the high frequency of fruit hypersensitivity in latex-allergic patients.

Adult↗
PubMed1996

Hepatotoxins and liver transplantation decrease pulmonary metastases in rats with hepatoma.

Results following liver transplantation for hepatocellular carcinoma have been dismal, attributed largely to recurrent disease locally or at distance sites. Undetected micrometastases or tumor that embolizes at the time of liver transplant from manipulation of the liver may account for these recurrences. A model and treatment protocol were developed to address this clinical problem. The protocol is modeled on the concept of bone marrow transplantation for leukemia. Hepatotoxins that are lethal to both normal hepatocytes and hepatoma cells are administered followed by liver transplantation to "rescue" the failing liver. The feasibility of this protocol was examined in a rat model. Male Buffalo rats were injected with 1 million Morris hepatoma MH-7777 cells intravenously at Day 0 as a model for micrometastatic disease. Three treatment groups were established. Group 1 received no treatment. Group 2 received 5% dextrose in water (D5W) followed by a syngeneic orthotopic liver transplant (OLTX). Group 3 received the hepatotoxin pyrazofuin (10 mg/kg) followed by OLTX. Animals were followed to Day 35, at which time they were sacrificed and examined for evidence of pulmonary metastases and quantitation of nodules with India ink insufflation. There was a significant decrease in the number with pulmonary nodules as well as the number of animals with pulmonary metastatic disease in the pyrazofurin-treated group compared with groups 1 and 2 (4.8 +/- 4.0 nodules/animal vs 45.2 +/- 11.2 nodules/animal--no treatment and 60.8 +/- 21.4 nodules animal--D5W/OLTX group) These data indicate that this model is reliable for examining metastatic hepatoma and that pyrazofurin is effective in preventing hematogenous micrometastases of hepatoma cells. Other hepatotoxins and the effect of allogeneic transplantation and immunosuppression could be examined in this model.

Amides↗
PubMed1996

Liver transplantation improves survival of rats bearing hepatoma-3924A.

There was interest in developing a rat model of hepatocellular carcinoma with tumor dissemination that would respond to liver transplantation. Thus, a model of intrahepatic hepatoma implantation with micrometastases was developed by modifying a previously reported technique in the ACI rat. The pattern of tumor growth permits surgical resection with liver transplantation if done early in the course of disease. In addition, this model results in a reproducible rate of pulmonary metastatic disease. The pulmonary metastatic rate (number of rats developing pulmonary metastases) was 45.5% (n = 11) 2 weeks following intrahepatic tumor implantation and rose to 100% at the fifth week (n = 7). To examine the long-term outcome of animals with tumor, 46 animals were followed until death or 100 days after tumor implantation. Of these animals, 67.4% died from tumor within 100 days, all with pulmonary metastases. Several of the animals that were followed long term had advanced liver tumor as well, with intraperitoneal spread and ascites. To evaluate the effect of orthotopic liver transplantation (OLTX) in this model, syngeneic OLTX was performed 16 days after intrahepatic tumor implantation (n = 11). OLTX improved the 100-day survival of the recipients from 32.6% (control group) to 80.0% (P < 0.05). None of the long-term survivors had evidence of tumor on postmortem examination. The mechanisms responsible for decreased metastases following syngeneic liver transplantation are being investigated. The influence of immunosuppression, more advanced stage of tumor at the time of OLTX, and chemotherapeutic agents on this survival benefit could be be investigated with this model.

Animals↗
PubMed1996

Improvement of productivity of yeast cell with a novel airlift loop reactor.

Two different strains of baker's yeast are cultivated using a fed-batch process with a novel airlift loop reactor. The reactor can be operated not only under steady-state conditions as the traditional airlift loop reactor, but also under forced periodically operational conditions in which the direction of liquid circulating flow is alternatively changed. Compared with the traditional steady-state operation, both the growth rate and yield of cells are much higher in the forced periodic operation.

Biotechnology↗
PubMed1996

Epidemiology of malignant melanoma.

Descriptive epidemiology of melanoma indicates increases in both incidence and mortality over the past two to three decades. A moderation in both rates began to emerge in several regions after the 1980s, especially in younger age groups. Recent improvement in survival rates is more likely due to earlier diagnosis than to real improvement in treatment. This suggests the potential effectiveness of secondary prevention. Continued health education efforts to improve awareness about signs and symptoms of melanoma should lead to earlier diagnosis and may increase incidence for a certain period of time. However, reduction in mortality will eventually be achieved owing to thinner melanoma at time of diagnosis. Etiologic studies indicate that the most important environmental risk factor for melanoma is extensive exposure to the sun. Primary prevention efforts should target public education about the risk of sun exposure and the benefit of wearing hats and adequate clothing. Specific prevention and control programs should be implemented among high-risk groups, such as those with light complexions and those sensitive to sunburn. In view of the long latency of melanoma, as much as 10 years, past exposure to the risk factors continues to cause melanoma, and any benefits of preventive efforts do not appear for some time. Although a dramatic decline is not expected in melanoma rates immediately, continuous preventive efforts ultimately should lead to a reduction in incidence and mortality.

Adolescent↗
PubMed1996

Regional distribution of carcinogen-induced colonic neoplasia in the rat.

Carcinogen induction of neoplasms in rodent colon has been used as a model for human colon cancer development and for evaluating chemopreventive regimens. We studied the regional distribution of small and large intestinal tumors in 229 rats given azoxymethane (AOM) once weekly for two weeks (15 mg/kg sc). The AOM regimen induced 63% more tumors in distal (DC) than in proximal colon (PC), although tumor volume was greater in PC. A high-fat (23% corn oil) diet increased tumors in PC and DC (p < 0.01). Caloric restriction of 10-30% of the ad libitum diet progressively reduced DC tumor formation but did not alter PC tumors. Tumor volume was unaffected by either regimen. Small intestinal tumors were concentrated in the proximal 15 cm of the intestine and were unaffected by dietary manipulation. This AOM model of colon tumor formation approximates human colon cancer distribution and is an appropriate model for rodent chemopreventive studies.

Animals↗
PubMed1996

Effects of erythorbic acid on vitamin C metabolism in young women.

Erythorbic acid, an epimer of L-ascorbic acid, is used in the United States as a food additive. Studies were conducted to determine whether the ingestion of erythorbic acid in the diet had any beneficial or adverse effects on the human requirement for vitamin C. Young women were fed diets that contained controlled amounts of erythorbic acid and ascorbic acid. In pharmacokinetic evaluations, erythorbic acid and ascorbic acid were rapidly absorbed with little interaction. Erythorbic acid cleared from the body more rapidly than ascorbic acid. Some subjects received diets deficient in vitamin C for periods < or = 30 d. Increasing intakes of erythorbic acid or prolonged intakes of < or = 1 g erythorbic acid/d did not indicate any interactions with ascorbic acid. Consumption of erythorbic acid resulted in the presence of erythorbic acid in mononuclear leukocytes. Ascorbic acid concentrations in these cells were not affected by the presence of erythorbic acid. Erythorbic acid disappeared quickly from these cells with cessation of erythorbic acid supplements. Prolonged ingestion of erythrobic acid by young women neither antagonized nor spared their vitamin C status.

Absorption↗
PubMed1996

Enhanced CD34 expression of sinusoid-like vascular endothelial cells in hepatocellular carcinoma.

The immunohistochemical expression of CD34 (human hematopoietic stem cell and endothelial cell marker) and laminin were studied in chronic liver diseases and hepatocellular carcinoma (HCC) to elucidate whether their expression reflected phenotypic differences between non-cancerous sinusoids and sinusoid-like tumor vessels. In normal liver, hepatic sinusoids were always negative for CD34 and laminin. In chronic hepatitis and cirrhosis, the two antigens were sparsely expressed in capillarized sinusoids at periportal and perinodular area. In advanced HCC, CD34 was strongly and diffusely expressed by the endothelial lining of sinusoid-like tumor vessels. However, early-stage HCC showed a wide spectrum of CD34 expression from negative to focal and diffuse, strongly positive staining in sinusoid-like vessels. Laminin was strongly expressed in advanced HCC but not in early-stage HCC. The results indicate that the enhanced expression of CD34 by sinusoidal endothelial cells may reflect the phenotypic change of endothelial cells in chronic liver diseases and HCC, and that the expression may correlate with the processes of angiogenesis induced by hepatocarcinogenesis.

Antigens, CD34↗
PubMed1996

Association between Alzheimer's disease and bound autochthonous IgM on T cells.

OBJECTIVE: To determine whether there is an association between the number of peripheral T cells binding IgM per total T cell population (%IgM+ T cells) and dementia. DESIGN: Cross-sectional study. SETTING: Two inpatient and two outpatient sites at a university medical center. PARTICIPANTS: Fifty-three adults. MEASUREMENTS: Peripheral blood was collected from each individual, and the %IgM+ T cells was determined by flow cytometry. The data obtained by medical record chart review were analyzed to determine whether the %IgM+ T cells correlated with cognitive diagnoses, demographic variables, medical diagnoses, or prescribed medications. RESULTS: The %IgM+ T cells was negatively correlated with MMSE scores (r = -.33, P = .016). There was a significant difference in the mean %IgM+ T cells between Alzheimer's disease (AD) and non-AD patients (35.6% +/- 30.2% vs 14.6% +/- 23.9%, P < .001) but no statistically significant association between the mean %IgM+ T cells and age, sex, race, prescribed medications (except gastrointestinal (GI) medications), or medical diagnoses (except stroke). After statistically controlling for GI medications and stroke, AD remained independently associated with the %IgM+ T cells (P = .008). CONCLUSIONS: Patients with AD had significantly more of their T cells coated with IgM than did non-AD patients.

Aged↗
PubMed1996

Inflammatory infiltration of the trigeminal ganglion after herpes simplex virus type 1 corneal infection.

Following herpes simplex virus type 1 (HSV-1) infection of the cornea, the virus is transmitted to the trigeminal ganglion, where a brief period of virus replication is followed by establishment of a latent infection in neurons. A possible role of the immune system in regulating virus replication and maintaining latency in the sensory neurons has been suggested. We have investigated the phenotype and cytokine pattern of cells that infiltrate the A/J mouse trigeminal ganglion at various times after HSV-1 corneal infection. HSV antigen expression in the trigeminal ganglion (indicative of the viral lytic cycle) increased until day 3 postinfection (p.i.) and then diminished to undetectable levels by day 7 p.i. The period of declining HSV antigen expression. was associated with a marked increase in Mac-1+ cells. These cells did not appear to coexpress the F4/80+ (macrophage) or the CD8+ (T cell) markers, and none showed polymorphonuclear leukocyte morphology, suggesting a possible early infiltration of natural killer cells. There was also a significant increase in the trigeminal ganglion of cells expressing the gamma delta T-cell receptor, and these cells were found almost exclusively in very close association with neurons. This period was also characterized by a rapid and equivalent increase in cells expressing gamma interferon and interleukin-4. The density of the inflammatory infiltrate in the trigeminal ganglion increased until days 12 to 21 p.i., when it was predominated by CD8+, Mac-1+, and tumor necrosis factor-expressing cells, which surrounded many neurons. By day 92 p.i., the inflammatory infiltrate diminished but was heaviest in mice with active periocular skin disease. Our data are consistent with the notion that gamma interferon produced by natural killer cells and/or gamma delta T cells may play an important role in limiting HSV-1 replication in the trigeminal ganglion during the acute stage of infection. In addition, tumor necrosis factor produced by CD8+ T cells and macrophages may function to maintain the virus in a latent state.

Animals↗
PubMed1996

Evidence for activation of endothelium and monocytes in hypertensive rats.

We have proposed that an interaction between perivascular macrophages and endothelium via cytokines could underlie the increased risk of stroke in hypertension. Therefore, the activation of monocytes, the endothelial expression of intercellular adhesion molecule-1 (ICAM-1), and the numbers of monocytes/macrophages in carotid arteries, as well as the cytokine production in carotid tissue, of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto and Sprague-Dawley rats were studied. The total number of blood monocytes (890 +/- 153 cells/mm3, n = 10) and the number of activated (nitro blue tetrazolium-positive) monocytes (220 +/- 51 cells/mm3, n = 10) were significantly greater (P < 0.05) in SHR than in WKY rats (440 +/- 81 and 40 +/- 16 cells/mm3, respectively, n = 10). Patchy endothelial expression of ICAM-1 was found in 77 +/- 9% of carotid sections from stroke-prone SHR (SHR-SP, n = 5) and in 75 +/- 7% of the sections from SHR (n = 7) but in none of the sections from the two normotensive rat strains (n = 7). The number of endothelium-attached monocytes/macrophages per millimeter of internal elastic lamina was significantly greater in SHR-SP than in SHR [5.1 +/- 0.7 (n = 4) and 3.3 +/- 0.3 (n = 6), P < 0.05], whereas no monocytes were found around the endothelium in either of the normotensive rat strains (n = 7 in each group). Incubation of the carotid arteries with lipopolysaccharide (30-300 ng/ml) induced a concentration-dependent expression of mRNAs for interleukin-1 beta and release of tumor necrosis factor-alpha to a significantly greater degree in the SHR than in the Wistar-Kyoto rats. The results demonstrate that hypertension is associated with activation of monocytes and endothelium and an increased endothelial adhesion and subendothelial accumulation of monocytes/macrophages and with an increased vascular capacity to produce cytokines.

Animals↗