Search PubMed⌕ Search

Biomedical subjects

P Wen

Publications and source records attributed to P Wen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Dehydroepiandrosterone-sulfate (DHEAS) reduces adipocyte hyperplasia associated with feeding rats a high-fat diet.

OBJECTIVE: To determine if chronic administration of a low level of dehydroepiandrosterone-sulfate (DHEAS) (10 micrograms/ml drinking water) attenuates adiposity in male Osborne-Mendel rats fed low-fat (11% of kcals) vs high fat (46% of kcals) diets. DESIGN: Rats were randomly assigned to one of four treatment groups for 6 wk in this 2 x 2 factorial study. The main effects tested were diet (low vs high fat) and DHEAS (- or +). SUBJECTS: Male Osborne-Mendel rats (initial body wt approximately 265 g). MEASUREMENTS: Adipocyte mass, size and number from two major fat depots (retroperitoneal, epididymal); mass of one subcutaneous adipose depot (inguinal); serum levels of triglycerides, insulin, glucose and DHEAS; brown adipose tissue (BAT) mass; body weight gain, food and water consumption, and residual carcass composition. RESULTS: DHEAS treatment had no effect on weight gain, food consumption or water intake. DHEAS-treated rats fed the high-fat diet had smaller fat pads containing fewer adipocytes and less carcass lipid than the non DHEAS-treated rats fed the high-fat diet. In contrast, DHEAS-treated rats fed the low-fat diet had similar levels of adipose tissue mass and cellularity compared to control animals fed the low-fat diet. CONCLUSION: Administration of a low dose of DHEAS (10 micrograms/ml or 0.8 mg/kg body wt/d) in the drinking water of young male Osborne-Mendel rats fed a high-fat diet for 6 wk reduced carcass lipid, fat depot mass and retroperitoneal and epididymal adipocyte number compared to their high-fat-fed cohorts. In this study, the antiobesity effects of DHEAS were specific to the level of dietary fat used.

Adipocytes↗
PubMed1997

Immunotoxin therapy of small-cell lung cancer: a phase I study of N901-blocked ricin.

PURPOSE: Immunotoxins could improve outcome in small-cell lung cancer (SCLC) by targeting tumor cells that are resistant to chemotherapy and radiation. N901 is a murine monoclonal antibody that binds to the CD56 (neural cell adhesion molecule [NCAM]) antigen found on cells of neuroendocrine origin, including SCLC. N901-bR is an immunoconjugate of N901 antibody with blocked ricin (bR) as the cytotoxic effector moiety. N901-bR has more than 700-fold greater selectivity in vitro for killing the CD56+ SCLC cell line SW-2 than for an antigen-negative lymphoma cell line. Preclinical studies suggested the potential for clinically significant cardiac and neurologic toxicity. We present a phase I study of N901-bR in relapsed SCLC. PATIENTS AND METHODS: Twenty-one patients (18 relapsed, three primary refractory) with SCLC were entered onto this study. Successive cohorts of at least three patients were treated at doses from 5 to 40 microg/kg/d for 7 days. The initial three cohorts received the first day's dose (one seventh of planned dose) as a bolus infusion before they began the continuous infusion on the second day to observe acute toxicity and determine bolus pharmacokinetics. Toxicity assessment included nerve-conduction studies (NCS) and radionuclide assessment of left ventricular ejection fraction (LVEF) before and after N901-bR administration to fully assess potential neurologic and cardiac toxicity. RESULTS: The dose-limiting toxicity (DLT) of N901-bR given by 7-day continuous infusion is capillary leak syndrome, which occurred in two of three patients at the dose of 40 microg/kg (lean body weight [LBW])/d. Detectable serum drug levels equivalent to effective in vitro drug levels were achieved at the 20-, 30-, and 40-microg/kg(LBW)/d dose levels. Specific binding of the immunotoxin to tumor cells in bone marrow, liver, and lung was observed. Cardiac function remained normal in 15 of 16 patients. No patient developed clinically significant neuropathy. However, a trend was noted for amplitude decline in serial NCS of both sensory and motor neurons. One patient with refractory SCLC achieved a partial response. CONCLUSION: N901-bR is an immunotoxin with potential clinical activity in SCLC. N901-bR is well tolerated when given by 7-day continuous infusion at the dose of 30 microg/kg(LBW)/d. Neurologic and cardiac toxicity were acceptable when given to patients with refractory SCLC. A second study to evaluate this agent after induction chemoradiotherapy in both limited- and extensive-stage disease was started following completion of this study.

Adult↗
PubMed1996

In vivo replication-deficient adenovirus vector-mediated transduction of the cytosine deaminase gene sensitizes glioma cells to 5-fluorocytosine.

Viral vector-mediated transfer of chemosensitization genes represents a promising new approach to the treatment of cancer. Previous reports have demonstrated that transfection of the bacterial cytosine deaminase (cd) gene into mammalian cells can sensitize them to the otherwise nontoxic nucleoside, 5-fluorocytosine (5-FC). We now report that a replication-deficient adenovirus vector that transduces the cd gene (Ad.CMV-cd) highly sensitizes 9L gliosarcoma cells to 5-FC, and that gene transduction is associated with a potent bystander effect that is not dependent on direct cell-to-cell contact. Stereotactic injection of Ad.CMV-cd into established rat gliomas, followed by systemic administration of 5-FC in vivo, results in prolongation of survival.

Adenoviruses, Human↗
PubMed1996

Noninvasive perfusion imaging of human brain tumors with EPISTAR.

A total of 17 patients with histologically proven diagnoses of low-grade astrocytoma (n = 4), high-grade astrocytoma (n = 8), lymphoma (n = 3), and meningioma (n = 2) were examined by using EPISTAR MR imaging. Meningiomas had the highest EPISTAR tumor/white matter contrast and low-grade astrocytomas and lymphomas the lowest. High-grade astrocytomas demonstrated elevated EPISTAR signal with marked regional heterogeneity. There was agreement between tumor vascularity by SPECT and EPISTAR in the five cases where both were done. Our results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection.

Adult↗
PubMed1995

Enhancer sharing in a plasmid model containing the alpha-fetoprotein and albumin promoters.

It has been proposed that the alpha-fetoprotein (AFP) enhancers also regulate the adjacent albumin gene, since the -10 kbp albumin enhancer is inactive in a number of cell lines that express albumin. In transfection experiments, the AFP enhancers strongly stimulate the albumin promoter in cells that silence the AFP promoter. These observations led us to develop a plasmid model of AFP-albumin gene switching, in which the albumin and AFP promoters would compete for the three AFP enhancers. However, when AFPCAT + ALBgal genes were combined with the AFP enhancers in one plasmid, both genes were driven at full activity. There was no change in the relative promoter expression over a wide range of transfected DNA concentrations, demonstrating that relative promoter activity was independent of DNA concentration and of promoter concentration, and that neither promoter was limiting the expression of the other. In contrast, a control plasmid containing two albumin promoters showed mutual inhibition, indicating the expected promoter competition. The albumin and AFP promoters noncompetitively shared the three enhancers on this plasmid, resulting in high levels of transcription from both promoters.

Albumins↗
PubMed1995

[8%-9% and 12%-13% hypoxic gas induced free radicals generation in rat's left and right myocardium].

Alpha-phenyl-tert-butylnitrone (PBN) was administered intravenously to capture free radicals of rat's myocardium. Rats were exposed to hypoxic gas (8%-9% O2 in N2) for 15 min. The ESR (electron spin resonance) signal intensity of PBN-spin adduct in the left myocardium increased significantly as compared with the normoxia group (n = 5, P < 0.05), but in the right myocardium there was no significant changes between hypoxia and normoxia. Rats exposed to hypoxic gas (12%-13% O2 in N2) were divided into four groups: I (hypoxia for 15 min), II (hypoxia for 60 min), III (hypoxia for 30 min/normoxia for 15 min/hypoxia for 30 min) and IV (injected MPEG- SOD intravenously before hypoxia for 60 min). The ESR signal intensity of PBN-spin adduct of left and right myocardium in group II increased significantly as compared with normoxia group (n = 5, P < 0.01), but the ESR signal intensity of group I didn't show obvious change as compared with normoxia group (n = 5, P > 0.05). In the right myocardium of group III the ESR signal intensity of PBN-spin adduct decreased significantly as compared with group II (n = 5, P < 0.05) and in the left myocardium did not decrease evidently. In the left myocardium of group IV the ESR signal intensity of PBN-spin adduct decreased evidently as compared with group II (n = 5, P < 0.05) and that in the right myocardium did not decrease evidently. When the rats were exposed to 8%-9% hypoxic gas for 15 min and 12%-13% hypoxic gas for 60 min, the SOD (superoxide dismutase, EC 1.11.1.9) activity of myocardium decreased and the content of MDA (malondialdehyde) increased significantly (n = 8, P < 0.05 or P < 0.01). The above results suggested that one way of myocardium free radical gereration may be relevant to decrease of SOD activity. The generation of free radicals pertained chiefly to superoxide free radical in the left myocardium and the membrane structure of myocardium cells might have been damaged largely during hypoxia.

Animals↗
PubMed1995

[Acute hypoxia induce free radicals generation in rat's cortex and hippocampus].

Anesthetized rats were ventilated artificially to 10.5%-11.0% O2 in N2 (equivalent to altitude about 5 000 m). PBN (alpha-phenyl-ter-butylnitrone) was injected intravenously 5 min before hypoxia. The experiment results showed that the ESR (electron spin resonance) signal intensity of PBN-spin adduct in cortex and hippocampus both increased significantly during hypoxia (15 min) as compared with normoxia group (n = 5, P < 0.01). In the third group of rats injected with MPEG-SOD (monomethoxy-polyethylene glycol-superoxide dismutase) intravenously 20 min before hypoxia, the ESR signal intensity of PBN-spin adduct in cortex and hippocampus did not decrease significantly under hypoxia for 15 min (compared with hypoxia group, n = 5, P > 0.05). This may be due to the fact that MPEG-SOD could not pass the blood-brain barrier owing to its large molecular weight. The enzyme activity of SOD (superoxide dismutase. EC 1.15.1.1), GSH-Px (Glutathione peroxidase, EC 1.11.1.9) and content of MDA (malondialdehyde) was also determined. The results showed that the hypoxia had no effect on the SOD, GSH-Px activity and MDA content (n = 7 or n = 8, P > 0.05). The above results suggested that ventilation to 10.5%-11.0% O2 in N2 15 min induced free radical generation in rat's cortex and hippocampus, but this generation was not due to decrease of SOD, GSH-Px activity in cortex and hippocampus.

Animals↗
PubMed1995

[Hypoxia induced increase of MDA and echinocytes from erythrocytes in rabbit's blood with special reference to inhibition of the increase by MPEG-SOD].

When rabbits acutely exposed to hypobaric hypoxia (at imitative altitude 5,000 m, PaO2 = 6.7 kPa), the percentage of the activity of superoxide dismutase (SOD in erythrocyte; EC 1.15.1.1) decreased respectively to 86%, 76%, 81%, 84%, 55%, 81%, 84% and 95% for a period of 0.25, 0.5, 1, 2, 3, 4, 5 and 24 h hypoxia while MDA (malondialdehyde) in erythrocyte and plasma increased significantly during hypoxia periods of 1, 2, 3, 5 and 24 h (n = 5, P < 0.05, P < 0.01 vs. normoxia group). The increase of MDA in plasma could be prevented by vitamin E (V. E, i.p, 1 mg daily for 3 consecative days before hypoxia), but that in erythrocyte did not show significant change probably because the injected V.E. without vehicle cannot penetrate through the erythrocyte membrane effectively. The echinocytes from erythrocytes increased significantly after hypoxia for 24 h (n = 5, P < 0.05 vs. normoxia group). However, by injecting MPEG-SOD (monomethoxypolythlene glycol-SOD) intravenously 30 min before hypoxia, the increase of MDA (both of erythrocyte and plasma) and echinocytes (from erythrocytes) were both inhibited obviously during hypoxia for 24 h (n = 5, P < 0.05, P < 0.01 vs. hypoxia group). It is inferred that the increase of MDA and echinocytes from erythrocytes may be due to lipid peroxidation by superoxide free radicals (O2-.) generated in erythrocytes through Fenton pattern Haber-Weiss reaction during hypobaric hypoxia.

Altitude↗
PubMed1994

A phase I study of etanidazole and radiotherapy in malignant glioma.

PURPOSE: To determine the maximum tolerable total dose (MTD) of etanidazole (ETA) when administered with external beam radiotherapy (XRT) and as a continuous infusion during stereotactic brachytherapy for patients with malignant glioma (anaplastic astrocytoma or glioblastoma multiforme or mixed cell tumors). METHODS AND MATERIALS: Seventy previously untreated patients were entered in a Phase I study. Prior to initiation of treatment, patients were stratified according to whether or not they were candidates for interstitial implantation. The implant patients (IMP, n = 17 pt) received accelerated fractionation XRT 20 Gy BID (6 h apart) to 40 Gy in 2 weeks with ETA 2 gm/m2 x 6 doses, a 2 week break and then interstitial implant to 50 Gy (4-7 days) with a continuous infusion of ETA over 90-96 h. The two sequentially conducted nonimplant arms started with accelerated fractionation XRT 2 Gy BID (6 h apart) to 40 Gy in 2 weeks with ETA 2 gm/m2 x 4-5 doses/week. NonIMP 1 arm (n = 38) received a 2-week break before standard fractionated boost XRT of 20 Gy/day for 2 weeks to a total dose of 60 Gy with ETA. NonIMP 2 arm (n = 14) did not have the 2-week break. All patients had plasma pharmacokinetic monitoring of ETA. RESULTS: The dose-limiting toxicity (DLT) in the IMP group was the cramping/arthralgia syndrome (4) and the cumulative MTD was 26 gm/m2. For both nonIMP 1 and 2 the DLTs were peripheral neuropathy and the cramping-arthralgia syndrome. The MTD for nonIMP 1 was 34 gm/m2 and nonIMP 2, 30 gm/m2. CONCLUSION: The clinical efficacy and radiation-related toxicity of these regimens are being evaluated. The doses of ETA that can be used with accelerated fractionation and with external beam irradiation plus brachytherapy have been established.

Adult↗
PubMed1994

Use of the immunotoxin N901-blocked ricin in patients with small-cell lung cancer.

In patients with small-cell lung cancer (SCLC), relapse with resistant disease often causes death. N901-blocked ricin (N901-bR), a murine monoclonal antibody (MAb)-blocked ricin immunotoxin, is a potential therapeutic for SCLC. N901-bR targets CD56, present on SCLC and cells of neuro-ectodermal origin. N901-bR kills up to 5 logs of CD56-positive cells at a concentration of 0.25 nM, while CD56-negative cells require 1000-fold more drug to achieve similar cell kill. We treated 21 patients with relapsed or refractory SCLC with a single 7-day course of N901-bR as a continuous infusion. We determined the MTD and toxicity profile, demonstrated drug binding to tumor cells in biopsies of lung, liver and bone marrow, and determined the time to development of human anti-mouse and anti-ricin antibodies. One patient had a documented PR and 6 patients demonstrated stable disease. Toxicity included transient elevation of liver enzymes, mild thrombocytopenia, hypoalbuminemia, fever, malaise, and evidence of capillary leak syndrome. Toxicities were controllable and reversible. No apparent drug-related central- or peripheral-nervous-system toxicity was noted by serial neurologic examinations, EMGs, and nerve conduction studies. Trials of N901-bR are planned in SCLC patients achieving CR and PR following chemoradiotherapy, and in relapsed/refractory patients. Anti-B4-bR will be added as an immunosuppressant in order to permit delivery of multiple courses of N901-bR. Additional trials will investigate synergy with conventional chemotherapeutics and the use of N901-bR as a sensitizing agent for chemotherapy-resistant tumors.

Animals↗
PubMed1994

A novel hepatocytic transcription factor that binds the alpha-fetoprotein promoter-linked coupling element.

We recently characterized a promoter-linked coupling element (PCE) in the rat alpha-fetoprotein (AFP) gene required for strong transcriptional stimulation by distant enhancers (P. Wen, N. Crawford, and J. Locker, Nucleic Acids Res. 21:1911-1918, 1993). In this study, oligonucleotide gel retardation and competition experiments defined the PCE as a 12-bp binding site, TGTCCTTGAACA, an imperfect inverted repeat from -166 to -155 near the AFP promoter. A factor that bound this site (PCF) was abundant in HepG2 nuclear extracts and detectable in extracts from several other AFP-producing hepatocarcinoma cell lines and fetal liver. Hepatocytic cell lines that did not express AFP, nonhepatocytic cell lines, adult liver, and fetal brain did not show the factor. Experiments excluded the possibility that PCF activity was due to binding of glucocorticoid receptor or an AP1-like factor that bound overlapping sites. Competition experiments with several mutant oligonucleotides determined that the optimum PCF binding site was TGTCCTTGAAC(A/T). Mutations decreased binding or totally abolished binding activity. In expression plasmids, PCE mutations strongly reduced gene expression. UV cross-linking to a PCE probe identified peptide bands near 34 kDa. PCF was purified by heparin-Sepharose chromatography followed by affinity binding to oligomerized PCE DNA. The product resolved as a complex of three peptides (PCF alpha 1, PCF alpha 2, and PCF beta, 32 to 34 kDa) on sodium dodecyl sulfate-acrylamide gels. The peptide sizes and gel patterns are unlike those of any of the well-described hepatic transcription factors, and the binding site has not been previously reported. PCF thus appears to be a novel transcription factor.

Animals↗
PubMed1993

Transactivation by hepatitis B virus X protein is promiscuous and dependent on mitogen-activated cellular serine/threonine kinases.

The X protein of hepatitis B virus (HBV-X) can act as a transactivator of transcription but its mechanism of action remains obscure. We have analyzed HBV-X transactivation in several cell types using 13 unrelated viral and cellular promoters and found that transactivation is more or less apparent in most cell types and is promiscuous and unrelated to specific sequence motifs within the target promoters. In general, though, HBV-X appears to act on enhancer elements since HBV-X had no effect on a minimal promoter, whereas HBV-X was able to transactivate after insertion of an AP-1 minienhancer. Several lines of evidence exclude the possibility that HBV-X interacts directly with the AP-1 enhancer or its binding proteins and suggest that the proximal target of HBV-X is peripheral to the transcription complex. This hypothesis is supported by the observation that inhibition of serine/threonine kinases, which regulate AP-1 activity (phorbol ester down-regulation or staurosporine inhibition of protein kinase C and a dominant negative mutant of Raf-1), blocked the ability of HBV-X to transactivate without affecting basal promoter activity. Furthermore, basal transcription from the AP-1-dependent promoter was increased by overexpression of protein kinase C and Raf-1 but HBV-X was unable to further stimulate, indicating that these kinases act subsequently to HBV-X. These data suggest that transactivation by HBV-X is an indirect result of the activation of cellular serine/threonine kinases including protein kinase C and Raf-1. This mode of action implies that HBV-X may affect other cellular processes, besides transcription, that are regulated by these kinases.

Animals↗
PubMed1993

A promoter-linked coupling region required for stimulation of alpha-fetoprotein transcription by distant enhancers.

We previously demonstrated that the rat alpha-fetoprotein (AFP) gene has three upstream enhancers that stimulate the AFP promoter additively in HepG2 cells (1). In this paper, deletion analysis demonstrated that a promoter-linked segment from -178 to -155 was required for full activity when the enhancers were distant from the promoter, even at less than their normal genomic distances, but dispensable when the enhancers were moved close to the promoter. This 'promoter-coupling element' appears to interact simultaneously with all three enhancers. Deletion analysis also localized a transcription stimulatory and a negative region in the promoter. Though these latter regions controlled the strength of the isolated promoter, they did not affect 'coupling' to the distant enhancers, and transcription stimulation by these distal promoter elements was small compared to the distant enhancers. Overall, the distant enhancers, acting through the promoter-coupling element, accounted for 70% of the activity of the transfected AFP gene. Footprint analysis with HepG2 nuclear extracts demonstrated protein binding at two sites near the promoter-coupling element. The data indicate a positive transcription control mechanism by which distant enhancers stimulate the AFP promoter through a specific promoter-linked element.

Animals↗
PubMed1992

Disseminating tumor cells and their interactions with leukocytes visualized in the brain.

Brain tumors are increasingly prevalent. Recent advances focus attention on individual, disseminated tumor cells that cannot be imaged or eliminated. Cells of the immune system may be ideally suited to attack individual tumor cells, but more basic understanding is needed. We describe a rat model, using the lacZ reporter gene, that allows identification of individual tumor cells, and tumor-leukocyte interactions in vivo. The model demonstrates how widely tumor can disseminate, without secondary tumorigenesis or recruitment of nonneoplastic cells. It demonstrates that leukocytes have access to disseminating tumor. Among its many applications, this work lays a foundation for developing cell-mediated immunotherapy against individual brain tumor cells.

Animals↗
PubMed1992

Final report of the phase I trial of continuous infusion etanidazole (SR 2508): a Radiation Therapy Oncology Group study.

Seventy-eight patients have been treated on a Phase I trial using continuous infusion etanidazole while undergoing brachytherapy for locally advanced tumors. There were two sequential schemata, the first treated 63 patients with doses ranging from 8-23 g/m2 over 48 hr and the second treated 15 patients with doses ranging from 20-23 g/m2 over 96 hr. The tumor sites were: brain (n = 42), cervix (n = 22), and breast (n = 14). Patients received a loading dose of etanidazole of 2 g/m2 followed by a continuous infusion for a total of 48 or 96 hr while radioactive implants were in place. Of the 63 patients in the 48-hr study, 52 were entered at doses of less than or equal to 21 g/m2 and there were no definite neuropathies but two patients with the cramping/arthralgia syndrome. Of the 11 patients entered at 22-23 g/m2, 1 patient had symptoms of peripheral neuropathy (Grade II) and 6 had the cramping/arthralgia syndrome. This is a new syndrome, distinct from the peripheral neuropathy, characterized by transient alterations in sensations consisting of cramping, arthralgias, or tingling that resolved completely at intervals varying from a few hours to about 1 week post-treatment. The cramping/arthralgia syndrome limited dose escalation; therefore, the maximum tolerated dose over 48 hr was determined to be 20-21 g/m2. The 96-hr infusion was limited to patients with recurrent gliomas undergoing stereotactic implantation. To date, 15 patients have been treated with doses of 20-23 g/m2. No toxicity was encountered at doses less than or equal to 22 g/m2. At 23 g/m2, one patient developed Grade III neuropathy and three patients had mild cramping/arthralgia syndrome, for whom the drug was discontinued. Therefore, it appears the maximum tolerated dose at 96 hr will be approximately 23 g/m2, which is 10-15% higher than for the 48-hr infusion.

Brachytherapy↗
PubMed1991

Enhancer, repressor, and promoter specificities combine to regulate the rat alpha-fetoprotein gene.

The upstream transcription control region of the rat alpha-fetoprotein (AFP) gene was analyzed using transient expression of CAT genes in HepG2 cells which express the gene; H4C3 cells which repress the AFP gene but express the albumin gene; and four nonexpressing cell lines. Deletion analysis based on the DNA sequence resolved three upstream enhancers corresponding to the mouse AFP enhancers, but showed additional weak effects from flanking sequences. Quantitative experiments demonstrated that the three enhancers were additive when acting through a single promoter and did not confirm the presence of a distal upstream repressor. All three enhancers stimulated the AFP, albumin, or thymidine kinase (tk) promoter in HepG2, but only the tk and albumin promoters in H4C3. Deletion of a proximal repressor region near the AFP promoter allowed expression in H4C3 cells with the AFP promoter. Thus, the liver-specific developmental repressor is near the AFP promoter, and H4C3 cells provide an in vitro system for analysis of this repressor in transfection assays. The repressor region also blocked expression of the SV40 enhancer through the AFP promoter in hepatic and nonhepatic cell lines, but when this enhancer was combined with an AFP promoter from which the repressor region was deleted, the combination showed expression in all six cell lines studied. AFP expression results from a combination of enhancer, promoter, and repressor activities, and the repressor is functional with a heterologous enhancer in a variety of cells.

Animals↗