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Biomedical subjects

C Benz

Publications and source records attributed to C Benz.

126 records · Page 7Linked to original sources
PubMed1985

Inhibition of growth of leukemic cells by inhibitors of calmodulin: phenothiazines and melittin.

Calmodulin, a ubiquitous calcium-binding protein, has recently been shown to play an important role in cellular proliferation. The calmodulin inhibitors melittin, trifluoperazine, and chlorpromazine inhibited the growth and clonogenicity of human and murine leukemic cells, and their potency reflected their activity as inhibitors of calmodulin. Melittin, which is a far more potent inhibitor of calmodulin activity, was also a more potent inhibitor of cell growth and clonogenicity. The less active phenothiazine metabolite, chlorpromazine sulfoxide, had much less potent cytotoxic activity.

Animals↗
PubMed1985

Sequential infusions of methotrexate and 5-fluorouracil in advanced cancer: pharmacology, toxicity, and response.

Preclinical studies have suggested that synergistic antitumor toxicity occurs when methotrexate (MTX) is administered prior to 5-fluorouracil (FUra). A protocol of sequenced, overlapping infusions of MTX and FUra was designed to achieve 5 microM MTX serum levels lasting 36 h and 1 to 5 microM FUra levels lasting 24 h, with leucovorin started at the end of the MTX infusion. Thirty-nine patients with metastatic neoplasms received a total of 127 treatment courses; two-thirds of the patients had received prior treatment with radiation therapy or chemotherapy; most of the latter treatment regimens included MTX or FUra. In three patients, the duration of FUra infusion was prolonged up to 72 h to determine the toxic limits of therapy. Blood samples were collected during treatment courses to estimate the half-lives and total-body clearances of MTX and FUra. The initial serum half-lives and total-body clearances of both MTX and FUra appeared within the range of reported normal values. The terminal half-life of MTX appeared less than previously reported values, and there appeared to be a substantial delay in achieving a FUra steady-state concentration; these two differences may have resulted from either the prolonged intervals of drug infusion or from metabolic interaction between the two drugs. During the 127 courses of treatment, nearly one-half of the patients experienced mild toxicity occurring after at least one treatment, but this toxicity was predominantly Grade I mucositis and/or diarrhea. Of the three patients who received extended intervals of FUra infusion, none was able to tolerate more than 48 h of FUra without developing mucositis. Thirty-four patients were evaluable for response; no one experienced a complete response, but 11 (32%) patients had either a partial or minimal response. Adenocarcinomas as a group, arising from the lung, gut, breast, and unknown site, appeared to respond best. Sequenced MTX-FUra infusion by this schedule is a generally well-tolerated regimen that deserves further clinical assessment.

Adult↗
PubMed1984

Thymidine enhancement of methotrexate and 5-fluorouracil toxicity in cultured human colon carcinoma.

Cultures of human colon carcinoma, HCT-8, were treated with millimolar concentrations of thymidine by different schedules designed to cytokinetically and biochemically modulate methotrexate (MTX) and 5-fluorouracil (FUra) toxicity. Thymidine (dThd)-synchronized HCT-8 cells monitored by flow cytofluorometry showed increased sensitivity to MTX and synergistic cytotoxicity to the combination MTX-FUra. FUra toxicity in synchronized cells showed no significant phase specificity overall, but a pattern of relative G2/M resistance was correlated with decreased intracellular FUra accumulation, incorporation into RNA, and formation of FdUMP. In asynchronous cultures dThd reduced MTX toxicity when given within the first 12 h of a 24-h MTX exposure, and also appeared to reduce the MTX-induced synergistic enhancement of FUra toxicity. When dThd was administered with FUra alone in asynchronous cultures, progressive, and synergistic enhancement of FUra toxicity was observed only after 6 h dThd pretreatment. Unlike MTX-FUra synergy, this schedule-dependent synergism between dThd and FUra did not correlate with intracellular FUra accumulation or specific incorporation into total cellular RNA. These results suggest that less well studied mechanisms of dThd modulation, other than enhanced deoxynucleotide formation or total RNA incorporation, may biochemically enhance FUra toxicity in HCT-8 cells.

Cells, Cultured↗
PubMed1984

Cytotoxicity of several chemotherapeutic agents in a human pancreatic cancer cell line (Colo-357).

Seven commonly available chemotherapeutic drugs were used to determine the concentration and time of exposure necessary to kill the newly available human pancreatic cancer cell line, Colo-357. The exposure periods were 2, 6, 12, and 24 hours. The most active drugs were methotrexate, mitomycin, and doxorubicin, each with an ID50 less than 0.1 microM for both a 12- and a 24-hour exposure. Cisplatin was intermediate, with an ID50 of approximately 0.7 microM at 12 and 24 hours. 5-FU, carmustine, and streptozocin were the least effective agents, with ID50 values greater than 50 microM after a 12-hour exposure and greater than 25 microM after a 24-hour exposure.

Antineoplastic Agents↗
PubMed1983

Tamoxifen and 5-fluorouracil in breast cancer: cytotoxic synergism in vitro.

The cytokinetic and cytotoxic interactions involved in combining tamoxifen, methotrexate, and 5-fluorouracil were studied in two hormone-dependent human breast cancer cell lines, 47-DN and MCF-7. These cells had measurable cytosol and nuclear estrogen receptor and cytosol progesterone receptor. Growth of the MCF-7 cells in medium containing gelding serum was stimulated maximally by addition of 10 pM estradiol. Both MCF-7 and 47-DN cells showed dose-dependent in vitro growth inhibition on exposure to tamoxifen, and toxicity from tamoxifen at concentrations up to 10 microM could be prevented by 1 nM estradiol. After exposure of 47-DN cells to 10 microM tamoxifen, cytosol progesterone and nuclear estrogen receptor levels were still detectable at 30 and 60% of control values. With this same concentration of tamoxifen, 47-DN cells in S phase declined 50% in association with a buildup of G0-1 cells. By clonogenic assay, tamoxifen enhanced 47-DN and MCF-7 cytotoxicity to 5-fluorouracil and 5-fluorouridine, but not to methotrexate alone. When given either concurrently or using a pretreatment-synchronizing schedule, tamoxifen enhanced markedly the growth inhibition of sequentially combined methotrexate and 5-fluorouracil. Isobologram analysis was used to prove that the cytotoxic interaction between tamoxifen and 5-fluorouracil was synergistic.

Breast Neoplasms↗
PubMed1983

Tamoxifen and 5-fluorouracil in breast cancer: modulation of cellular RNA.

Biochemical studies were undertaken with the human breast carcinoma cell line, 47-DN, to explore the mechanisms underlying cytotoxic synergy between tamoxifen (TAM) and the fluoropyrimidines, 5-fluorouracil (FUra) and 5-fluorouridine (FUrd). The influence of TAM pretreatment was measured on intracellular FUra accumulation, FUra nucleotide formation, and incorporation of fluoropyrimidines into cellular RNA. Unlike other modulators of FUra metabolism and toxicity. TAM decreased intracellular FUra accumulation and total RNA incorporation by 20 to 60%. Cells treated with TAM contained 10 to 20% less cellular RNA and showed reduced transcription and altered RNA turnover, independent of fluoropyrimidine treatment. Newly synthesized RNA from control and TAM-treated cells was fractionated by sucrose gradient centrifugation. The specific incorporation of FUrd (2 hr) was compared to that of FUra (6 hr) and labeled uridine incorporation into controls. Compared to its effect on uridine incorporation, TAM produced nearly twice as much FUra incorporation and 3 times as much FUra incorporation into 32 to 45S RNA. Since accumulation of this high-molecular-weight RNA has been associated with fluoropyrimidine toxicity and impaired ribosomal RNA processing, it is believed that TAM enriched the RNA-mediated toxicity of FUra and FUrd in this breast carcinoma cell line.

Breast Neoplasms↗
PubMed1983

Use of high-dose oral methotrexate sequenced at 24 hours with 5-FU: a clinical toxicity study.

Twenty-three patients with advanced carcinoma were treated with 131 courses of high-dose oral methotrexate (MTX), sequenced at 24 hours with 5-FU iv and subsequent leucovorin rescue. The 30% incidence of toxicity was predominantly mild to moderate mucositis and myelosuppression. Trough and peak serum MTX levels demonstrated that micromolar concentrations were sustained greater than 24 hours. Toxicity correlated with shorter re-treatment intervals and not with serum MTX levels. This regimen can be safely and conveniently administered to an outpatient population and deserves further assessment in phase II trials.

Breast Neoplasms↗
PubMed1982

Optimal schedule of methotrexate and 5-fluorouracil in human breast cancer.

We have shown previously that methotrexate pretreatment of murine leukemia and human colon carcinoma cell cultures results in augmented intracellular accumulation of 5-fluorouracil metabolites. Both of these drugs are commonly used for the treatment of women with breast cancer; thus, sequencing of methotrexate before 5-fluorouracil was evaluated in vitro using a human mammary carcinoma cell line, 47-DN. Intracellular 5-fluorouracil accumulation was maximally increased 4-fold in cultures pretreated with 10 microM methotrexate for 24 hr. This enhancement of 5-fluorouracil metabolism was associated with increased intracellular levels of 5-phosphoribosyl 1-pyrophosphate, resulting from the antipurine effect of methotrexate. Brief exposure to exogenous hypoxanthine at physiological concentrations reversed the biochemical synergism between methotrexate and 5-fluorouracil. Other antimetabolites associated with elevations of 5-phosphoribosyl 1-pyrophosphate enhanced intracellular accumulation of 5-fluorouracil up to 2.5-fold. In cloning assays, 18 hr of methotrexate pretreatment followed by 5-fluorouracil resulted in optimal synergistic cytotoxicity, which could be prevented if high concentrations of leucovorin were given between methotrexate and 5-fluorouracil administration. Since these results indicated that optimal breast tumor toxicity in vitro was achieved by 18- to 24-hr sequencing of methotrexate and 5-fluorouracil, clinical toxicity study was carried out to assess whether this drug schedule could be tolerated. Seven patients with advanced cancer were treated with 21 courses of sequential therapy. No toxicity occurred with 38% of treatment courses; mild to moderate leukopenia and mucositis occurred with 29 and 38% of courses respectively. Toxicity was related to treatment interval and not cumulative drug dose or elevated serum methotrexate levels. These clinical results suggest that Phase II studies evaluating 24-hr-sequenced methotrexate and 5-fluorouracil in breast cancer are warranted.

Breast Neoplasms↗
PubMed1981

The influence of methotrexate pretreatment on 5-fluorouracil metabolism in L1210 cells.

Pretreatment of L1210 cells with methotrexate in concentrations which produced free intracellular methotrexate and near maximal inhibition of dihydrofolate reductase resulted in an enhancement of intracellular 5-fluorouracil (FUra) accumulation. This enhancement of FUra accumulation was maximum (5-fold increase) after a 6-h exposure to 100 microM methotrexate. The nucleotide derivatives of FUra, including a 5-fluoro-2'-deoxyuridylate, and 5-fluorouridine-5'-triphosphate were also increased nearly 5-fold following methotrexate treatment. In cells pretreated with methotrexate, there was an increase in intracellular 5-phosphoribosyl-1-pyrophosphate pools which ranged from 2 to 8 times control values following concentrations of methotrexate between 0.1 microM and 10 microM. Both the increase in 5-phosphoribosyl-1-pyrophosphate and FUra accumulation could be prevented by the addition of Leucovorin (N5-formyltetrahydrofolate) at concentrations which rescued cells from the inhibitory effects of methotrexate. Pretreatment with 6-methylmercaptopurine riboside, which inhibits amidophosphoribosyltransferase, the first committed step in de novo purine synthesis, also resulted in a similar elevation in 5-phosphoribosyl-1-pyrophosphate pools and enhancement of FUra accumulation. If the 5-phosphoribosyl-1-pyrophosphate pools were reduced following methotrexate pretreatment by the addition to the cultures of hypoxanthine, which utilizes 5-phosphoribosyl-1-pyrophosphate for the conversion to IMP, the intracellular accumulation of FUra was not enhanced. Also, if the inhibitor of 5-phosphoribosyl-1-pyrophosphate synthetase, 7-deazaadenosine, was given to cultures with methotrexate, there was no increase in 5-phosphoribosyl-1-pyrophosphate pools, nor enhancement of FUra accumulation. In addition, when 5-fluoro-2'-deoxyuridine was added with the methotrexate to cell cultures, there was no increase in 5-phosphoribosyl-1-pyrophosphate pools, nor enhancement of intracellular FUra accumulation. These results indicate that the ability of methotrexate to enhance FUra accumulation was probably the consequence of the antipurine effect of methotrexate which resulted in a reduction of the complex feedback inhibition on 5-phosphoribosyl-1-pyrophosphate synthesis and utilization. The resultant increased 5-phosphoribosyl-1-pyrophosphate pools were then capable of being utilized for the conversion of FUra to 5-fluorouridylate, the possible rate-limiting step in FUra intracellular metabolism and the major determinant of the rate of intracellular FUra accumulation. When methotrexate preceded FUra, there was synergistic cell killing as determined by soft agar cloning. The exact mechanism of this sequential synergistic antitumor activity may be the result of the enhanced incorporation of FUra into RNA, since the increased 5-fluoro-2'-deoxyuridylate which is formed is unlikely to increase substantially the inhibition of dTMP synthesis induced by methotrexate pretreatment.

Animals↗
PubMed1981

Biochemical alterations during unperturbed suspension growth of L1210 cells.

The following parameters were evaluated at several points throughout unperturbed suspension culture growth of L1210 cells: cell volume; DNA histograms; the mean content of cellular DNA, RNA, and protein; ribonucleoside and deoxyribonucleoside triphosphate pools; phosphoribosyl pyrophosphate; and the incorporation of glycine into purine bases. The cell volume, the incorporation of glycine into purine bases, and the intracellular pools of phosphoribosyl pyrophosphate and dexoyribunucleotides began to decrease significantly during the midportion of logarithmic cell growth. However, there was no significant change in the DNA content per cell during culture growth. The RNA, protein content, and ribonucleotides all demonstrated a biphasic pattern with the highest values obtained during the midportion of logarithmic growth followed by rapid decline as the culture approached plateau growth. These intracellular fluctuations in de novo synthesis and precursor pools were correlated with the variable intracellular accumulation of three fluoropyrimidines (5-fluorouracil, 5-fluorouridine, and 5-fluorodeoxyuridine) and their active metabolites (5-fluorouridine triphosphate and 5-fluorodeoxyuridylate). These studies were performed to demonstrate that multiple biochemical alterations occur during logarithmically growing suspension cell cultures and could result in misleading conclusions of experiments with antimetabolites unless these factors are considered in the context of the performed studies.

Animals↗
PubMed1981

Modulation of 5-fluorouracil metabolism and cytotoxicity by antimetabolite pretreatment in human colorectal adenocarcinoma HCT-8.

The modulation of 5-fluorouracil (FUra) metabolism by methotrexate (MTX) pretreatment in monolayer cultures of human colorectal adenocarcinoma. HCT-8, was examined and correlated to clonal growth of this cell line. There was a gradual and nearly linear total intracellular accumulation and incorporation into RNA of FUra for 30 hr in control cells. A 12-hr 10 microM MTX pretreatment before adding 100 microM FUra resulted in approximately a 3-fold increase in total FUra accumulation, 59% of which was fluorouridine triphosphate. Soluble fluorodeoxyuridine monophosphate was increased 5-fold following MTX pretreatment; however, [3H]deoxyuridine incorporation into the acid-precipitable fraction of cells pretreated with MTX was no more than that observed when FUra was given alone. There was also an increase in 5-phosphoribosyl 1-pyrophosphate pools following MTX which was associated with the enhanced FUra metabolism. The maximum synergistic inhibition of clonal growth occurred when FUra was given during the last 6 hr of a 24-hr MTX exposure period. Other antimetabolites associated with elevations of 5-phosphoribosyl 1-pyrophosphate also resulted in an enhanced total intracellular accumulation of FUra.

Adenocarcinoma↗
PubMed1980

Uridine and cytidine metabolism following inhibition of de novo pyrimidine synthesis by pyrazofurin.

Pyrazofurin, an inhibitor of orotidylate decarboxylase, imposes an absolute nutritional requirement for exogenous uridine to maintain normal growth of L5178Y, P388, L1210, W256 and S180 cells in vitro. The amount of uridine necessary for cell division when de novo uridine nucleotide synthesis is inhibited by pyrazofurin is: L5178Y, 30.5; P388, 39.7; L1210, 53.3: W256, 70.6; and S180, 886 fmol/cell. Cytidine, which can be deaminated to uridine, will substitute for uridine to maintain normal cell growth in the presence of growth-inhibitory concentrations of pyrazofurin (5 microM). The requirements for cytidine and uridine are identical. If cytidine deamination is prevented by tetrahydrouridine (100 microM), cytidine can no longer support growth in the presence of pyrazofurin. Cytidine and uridine, as expected, are additive in their effect to permit normal growth of pyrazofurin treated cells. Tetrahydrouridine does not alter this additive effect, indicating that when both nucleotides are added to pyrazofurin treated cells each nucleotide replenishes their respective nucleotide pools and cytidine deamination is unnecessary to allow cell growth. Incorporation of [14C]uridine into the acid insoluble cell fraction of L5178Y cells was 25 fmol/cell at 48 h and remained constant during the remaining growth of the pyrazofurin treated cell suspension. The [14C]uridine acid soluble pool of 4 fmol/cell also was maximum at 48 h but declined during the subsequent growth of the suspension culture to approx. 2 fmol/cell at 96 h. This decline in the acid soluble pool is correlated with a 42% decrease in modal cell volume during this phase of cell growth which would maintain a constant specific activity of uridine in this pool. This may explain the decline in the acid soluble pool while the acid insoluble pool remains constant during growth of suspension cultures of L51878Y cells. The block in pyrimidine synthesis de novo induced by pyrazofurin provides a useful and quick method for the evaluation of uridine and cytidine metabolism of tumor cell specimens.

Amides↗
PubMed1980

Schedule-dependent cytotoxicity of methotrexate and 5-fluorouracil in human colon and breast tumor cell lines.

The effect of sequential methotrexate and 5-fluorouracil on the clonal growth of the human colon adenocarcinoma cell, HCT-8, and the hormone-dependent human breast carcinoma cell, 47-DN, was examined. In both cell lines, when 5-fluorouracil was given during the last 6 h of a 24 h methotrexate exposure period, there was marked synergistic inhibition of clonal growth. Shorter intervals or the reverse sequence of drugs were either additive or antagonistic. These results indicate the importance of the drug sequence and time interval between drug administration for optimal cytotoxicity in these human cell lines. This information suggests that the administration of methotrexate 18 h before 5-fluorouracil may have potential application in the design of clinical trials for these malignancies.

Adenocarcinoma↗
PubMedDate not supplied

The role of serum liver enzymes in the diagnosis of choledocholithiasis.

BACKGROUND/AIMS: The introduction of laparoscopic cholecystectomy has increased the need for preoperative diagnosis of common bile duct stones. The purpose of this study is to verify the sensitivity of the liver function tests in the detection of duct stones. METHODOLOGY: We evaluated 438 patients (223 retrospectively and 215 prospectively) who underwent endoscopic papillotomy for bile duct stones in two different services. In every case, blood samples for liver function tests levels were collected prior to endoscopic retrograde cholangiopancreatography. RESULTS: The most sensitive test was gamma-glutamyl transpeptidase, that was abnormal in 92.2% of the cases. Alkaline phosphatase was elevated in 74.7% of the patients with choledocholithiasis. The least sensitive parameter was AST, altered in only 50.8% of times. The sensitivity of all liver tests for the diagnosis of choledochal stones taken together was 94.3%. CONCLUSIONS: Liver function tests are very sensitive in the detection of common bile duct stones, however these blood tests are in the normal range of about 5% of endoscopically treated patients.

Adolescent↗
PubMedDate not supplied

Expression of apoptosis and apoptosis-related peptides in various stages of rejection in the human transplanted liver.

BACKGROUND/AIMS: In the transplanted liver, the role of apoptosis and apoptosis-related proteins are largely unknown. This study addresses the question whether hepatocyte or leukocyte apoptosis plays an important role in acute rejection of the transplanted human liver and which pathways are involved. METHODOLOGY: Cryosections from liver biopsies with acute rejection were stained with the TUNEL technique for detection of apoptosis and labeled immunohistochemically with antibodies against CD95, bcl-2, TGF-beta and iNOS. A double-labeling protocol was developed for simultaneous detection of iNOS and apoptosis. Liver tissue with chronic viral hepatitis, with hepatitis reinfection and tissue without pathological findings served as a control. RESULTS: Leukocyte apoptosis was markedly reduced in severe compared to mild or moderate acute rejection. Hepatocyte apoptosis is detected rarely in acute rejection with a slight increase from mild to severe despite a strong expression of CD95 and TGF-beta on hepatocytes. The hepatocyte expression of iNOS is weak in acute rejection but strong in control slides with hepatitis B/C reinfection. In acute rejection, simultaneous expression of iNOS and apoptosis could be demonstrated in Kupffer-cells. CONCLUSIONS: Severe acute rejection in the human transplanted liver is characterized by a lack of apoptosis of infiltrating portal lymphocytes probably caused by a reduced downregulation of lymphocyte function. Secondly, in spite of the strong expression of CD95 and TGF-alpha, hepatocyte apoptosis plays a limited role for liver damage in acute rejection. Finally, Kupffer cell apoptosis is increased in acute rejection and seems to be induced by nitric oxide.

Apoptosis↗
PubMedDate not supplied

Endoscopic stenting in obstructive jaundice due to liver metastases: does it have a benefit for the patient?

BACKGROUND/AIMS: The goal of this report is to describe our experience with the palliative endoscopic treatment of jaundice occurring in the setting of liver and hilar metastases of a distant primary malignancy. MATERIAL AND METHODS: We retrospectively analyzed the clinical course of 29 consecutive patients with metastatic tumors not originating in the hepatobiliopancreatic area, who were treated by endoscopic retrograde cholangiopancreatography with endoprostheses insertion. RESULTS: We achieved a complete follow-up in 24 out of the 29 patients (11 women, median age 69 years). The primary tumor site was the colorectum in 15 patients, stomach in 4, lung in 2, breast and prostate in 1 and one patient had a lymphoma. The median bilirubinemia before therapy was 16 (1.8-31) mg/dl and the median minimum serum bilirubin reached after stenting was 2.6 (0.3-11.5) mg/dl. Stent dysfunction was observed in 33.5% of the patients and stent change was necessary 13 times. The median survival after therapy was 4 (2.5-19) months for patients with colon tumors and 3 (0.5-12) months in patients with other cancers. An improvement in the quality of life was obtained in 75% of the patients after endoscopic treatment. CONCLUSIONS: Endoscopic stenting should be attempted even on patients with obstructive jaundice due to liver metastases.

Aged↗
PubMedDate not supplied

[Endoscopic laser lithotripsy for difficult calculi after unsuccessful extracorporeal shock wave lithotripsy].

INTRODUCTION: More than 97% of common bile duct stones can be successfully managed by endoscopic papillotomy, mechanical lithotripsy and extracorporeal shock-wave lithotripsy. In this study, we evaluate the role of laser lithotripsy after failure of the above mentioned endoscopic methods. PATIENTS AND METHODS: Eighteen patients (15F, 3M; median age = 69 (28-83) years) were treated by endoscopic laser lithotripsy after ESWL failure. We employed a Rhodamine-6 G laser with a stone-tissue recognizing system. The laser fibers were cholangioscopically (direct vision) or blindly (under plain fluoroscopic control) placed. RESULTS: Seventeen patients were treated endoscopically and one was successfully managed percutaneously after failure of the transpapillary approach. Fourteen (78%) were stone-free after a mean of 1.56 laser therapy sessions alone. Two additional patients were successfully managed after partial fragmentation with combined treatment (mechanical lithotripsy: n = 1, electrohydraulic lithotripsy: n = 1). Overall, 89% of the patients were freed from their calculi. Cholangitis occurred once and the mortality was zero. CONCLUSIONS: We conclude that laser lithotripsy is an effective and safe treatment alternative in a highly selected patient population with difficult bile duct stones and considerable surgical risk.

Adult↗