Biomedical subjects

T Madden

Publications and source records attributed to T Madden.

At least 19 recordsLinked to original sources

PubMed2006

A novel inhibitor of the STAT3 pathway induces apoptosis in malignant glioma cells both in vitro and in vivo.

Signal transducer and activator of transcription-3 (STAT3) is constitutively activated in a variety of cancer types, including malignant gliomas. STAT3 is activated by phosphorylation of a tyrosine residue, after which it dimerizes and translocates into the nucleus. There it regulates the expression of several genes responsible for proliferation and survival at the transcriptional level. A selective inhibitor of STAT3 phosphorylation, AG490, has been shown to inhibit growth and induce apoptosis in some cancer cell types. However, although AG490 routinely shows in vitro anticancer activity, it has not consistently demonstrated an in vivo anticancer effect in animal models. Here, we have tested WP1066, a novel inhibitor structurally related to AG490 but significantly more potent and active, against human malignant glioma U87-MG and U373-MG cells in vitro and in vivo. IC(50) values for WP1066 were 5.6 muM in U87-MG cells and 3.7 muM in U373-MG cells, which represents 18-fold and eightfold increases in potency, respectively, over that of AG490. WP1066 activated Bax, suppressed the expression of c-myc, Bcl-X(L) and Mcl-1, and induced apoptosis. Systemic intraperitoneal administration of WP1066 in mice significantly (P<0.001) inhibited the growth of subcutaneous malignant glioma xenografts during the 30-day follow-up period. Immunohistochemical analysis of the excised tumors revealed that phosphorylated STAT3 levels in the WP1066 treatment group remained inhibited at 3 weeks after the final WP1066 injection, whereas tumors from the control group expressed high levels of phosphorylated STAT3. We conclude that WP1066 holds promise as a therapeutic agent against malignant gliomas.

Antineoplastic Agents↗

PubMed2003

A population-based longitudinal study of cognitive functioning in the menopausal transition.

BACKGROUND: No longitudinal studies have tracked cognitive performance through the menopausal transition and thus the impact of the transition on cognition, independent of aging, is not known. The authors hypothesized that a decline in cognitive functioning occurs as women progress through the menopausal transition, independent of age, educational level, family income, ethnicity, and baseline self-perceived health. METHOD: The authors began a population-based, longitudinal study in January 1996 with yearly follow-up interviews. This report includes follow-up through November 2001. The authors randomly selected African American and white women from a census of two contiguous Chicago communities. After screening for eligibility (age 42 to 52 years, premenopausal or early perimenopausal, no exogenous hormone use in the past 3 months, and no hysterectomy), 868 agreed to participate. Women who became pregnant, had a hysterectomy, or began using hormones were censored from that time onward. This study reports on 803 women for whom cognitive assessments were available. The authors assessed working memory (Digit Span Backward) and perceptual speed (Symbol Digit Modalities Test). RESULTS: Contrary to the hypothesis, the authors found small but significant increases over time during the premenopausal and perimenopausal phases. This trend was not accounted for by chronological age, education, family income, ethnicity, or baseline self-perceived health. CONCLUSIONS: Transition through menopause is not accompanied by a decline in working memory and perceptual speed.

Adult↗

PubMed2001

Simultaneous quantification of arachidonic acid metabolites in cultured tumor cells using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry.

A validated method is described for the simultaneous analysis of PGE2, 11-, 12-, and 5-HETEs from cultured cells using HPLC negative electrospray ionization tandem mass spectrometry (LC/MS/MS). This method permits quantification of selected individual arachidonic acid metabolites from cell extracts without derivatization, multiple purification steps, or lengthy separation times required by traditional GC-MS- or HPLC-UV -based methods. Accuracy assessments of values calculated using this method showed deviations from nominal values were < or =15%. An average relative deviation of 7% of mean calculated values was observed for values taken on separate days. The lower limit of detection for all metabolites was 1.3 pg. The method was used to quantify arachidonic acid metabolites present in various cancer cell lines after incubation with arachidonic acid and the selective cyclooxygenase-2 inhibitor celecoxib. Results showed that the presence of celecoxib in lung cancer A549 cells reduced production of both PGE2 and 11-HETE in a concentration-dependent manner.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed2001

Inhibition of export of fibroblast growth factor-2 (FGF-2) from the prostate cancer cell lines PC3 and DU145 by Anvirzel and its cardiac glycoside component, oleandrin.

Anvirzel is an extract of Nerium oleander currently undergoing Phase I clinical evaluation as a potential treatment for cancer. Two of the active components of Anvirzel are the cardiac glycosides oleandrin and oleandrigenin. Previous studies have demonstrated that, in vitro, cardiac glycosides may inhibit fibroblast growth factor-2 (FGF-2) export through membrane interaction with the Na(+),K(+)-ATPase pump. In continuing research on the antitumor activity of this novel plant extract, the relative abilities of oleandrin and oleandrigenin to inhibit FGF-2 export from two human prostate cancer cell lines, DU145 and PC3, were examined. An ELISA assay was utilized to determine the FGF-2 concentration in the cell culture medium before and after exposure to cardiac glycosides or the parent extract material Anvirzel. Both cell lines were exposed to non-cytotoxic concentrations of oleandrin (0.05 and 0.1 ng/mL) for up to 72 hr. Studies also were conducted with Anvirzel and ouabain. Oleandrin (0.1 ng/mL) produced a 45.7% inhibition of FGF-2 release from PC3 cells and a 49.9% inhibition from DU145 cells. Non-cytotoxic concentrations (100 ng/mL) of Anvirzel produced a 51.9 and 30.8% inhibition of FGF-2 release, respectively, in the two cell lines. The decrease in FGF-2 release from cells required continuous incubation for 48--72 hr; shorter incubation times were not effective. These results demonstrate that Anvirzel, like oleandrin, inhibited FGF-2 export in vitro from PC3 and DU145 prostate cancer cells in a concentration- and time-dependent fashion and may, therefore, contribute to the antitumor activity of this novel treatment for cancer.

Biological Transport↗

PubMed2000

Acute safety and pharmacokinetics of intravenous busulfan when used with oral busulfan and cyclophosphamide as pretransplantation conditioning therapy: a phase I study.

The unpredictable intestinal absorption and erratic bioavailability of oral busulfan (Bu) has limited the drug's use in high-dose pretransplantation conditioning therapy. To standardize drug delivery, we solubilized Bu for parenteral use. This new intravenous (i.v.) Bu formulation was combined with oral Bu and cyclophosphamide (Cy) to evaluate (1) the human acute toxicity of i.v. Bu and its solvent system and (2) the pharmacokinetics of Bu in patients undergoing hematopoietic progenitor cell transplantation (HPCT). One dose of i.v. Bu (escalating from 0.08 to 0.8 mg/kg) was given over 2 hours by pump; 6 hours later, an oral Bu regimen was begun, consisting of 1 mg/kg every 6 hours for 15 doses, followed by Cy, 60 mg/kg daily for 2 days. After 1 day of rest, HPCT was performed. The i.v. Bu dose was well tolerated and did not produce any acute toxicity reaction that could be attributed to the solvent system of dimethylacetamide and polyethylene glycol (PEG)-400. All observed treatment-related toxicity was as would be expected after high-dose oral Bu plus Cy. When the i.v. Bu was used as reference solution, the pharmacokinetic analysis indicated an average bioavailability of oral high-dose Bu of 69%, ranging from <10% to virtually 100%. Further, the 2-hour infusion of i.v. Bu gave a time to maximum plasma concentration following drug administration similar to that of oral Bu (2 hours and 1.8 hours, respectively), and i.v. Bu had a clearance similar to that of oral Bu. Based on the data in this study, we suggest that the optimal (starting) dose of i.v. Bu (in combination with Cy) in our forthcoming phase 2 trial should be on the order of 0.8 mg/kg to target an area under the curve (AUC) of 1100 to 1200 micromol/L per minute. This would secure myeloablation and engraftment but save the vast majority of patients from the increased risk of serious hepatic veno-occlusive disease that has been reported when the AUC level exceeds 1500 micromol/L per minute. Bu administration via the i.v. route will assure complete bioavailability and reliable systemic drug exposure with more predictable blood levels and, therefore, possibly lower the risks for serious/life-threatening toxicity, graft rejection, and recurrent leukemia.

Acetamides↗

PubMed2000

Individualizing high-dose oral busulfan: prospective dose adjustment in a pediatric population undergoing allogeneic stem cell transplantation for advanced hematologic malignancies.

We investigated whether adjusting the oral busulfan (BU) dosage on the basis of early pharmacokinetic data to achieve a targeted drug exposure could reduce transplant-related complications in children with advanced hematologic malignancies. Twenty-five children received a preparative regimen consisting of thiotepa (250 mg/m2 i.v. daily for 3 days), BU (40 mg/m2 per dose p.o. every 6 h for 12 doses), and cyclophosphamide (60 mg/kg i.v. daily for 2 days) and then underwent allogeneic stem cell transplantation. Busulfan clearance and area under concentration time-curve (AUC) were determined after the first dose using a one-compartment pharmacokinetic (PK) model with first-order absorption. The initial PK analysis was successfully completed after the first BU dose in 21 patients (84%). A final AUC of 1000-1500 microM x min/dose was targeted and subsequent doses were modified as necessary to achieve this value. Fourteen of the 25 patients (56%) required dose adjustment. Follow-up PK analysis was completed in 21 patients and 16 of these achieved the targeted BU exposure for the course of therapy. Interpatient variability in BU clearance was high (up to five-fold). The most frequent regimen-related toxicities were cutaneous and gastrointestinal (stomatitis and diarrhea). Only one patient developed hepatic veno-occlusive disease. Our study demonstrates the feasibility of adjusting the oral BU dose in individual pediatric patients. Although toxicity associated with BU seemed to be reduced, this conclusion is tempered by the fact that the overall regimen-related toxicity (RRT) remains substantial and reflected the effects of all agents used in the preparative regimen.

Administration, Oral↗

PubMed2000

Determination of glomerular filtration rate using a dual-detector gamma camera and the geometric mean of renal activity: correlation with the Tc-99m DTPA plasma clearance method.

PURPOSE: In this study, the authors studied the use of a dual-detector gamma camera to measure the glomerular filtration rate (GFR). METHODS: Thirty-three patients with a wide range of renal function participated in this study. The GFR was measured using a dual-detector gamma camera by calculating the geometric mean of activity from each kidney and using an outline background. These results were compared with the GFR estimates obtained from Tc-99m DTPA plasma clearance using a multiple blood sample method. RESULTS: Correlation was excellent between GFR estimated using the dual-detector gamma camera and GFR measured using the plasma clearance of Tc-99m DTPA with multiple blood samples (r = 0.89). The correlation was especially strong in children younger than 13 years (r = 0.94). CONCLUSION: Measuring the GFR using a dual-detector gamma camera and calculating the geometric mean of renal activity yields relatively accurate results.

Adult↗

PubMed2000

Novel marine-derived anticancer agents: a phase I clinical, pharmacological, and pharmacodynamic study of dolastatin 10 (NSC 376128) in patients with advanced solid tumors.

Dolastatin (DOLA)-10 is a pentapeptide isolated from the mollusc Dolabella auricularia with clinically promising antitumor activity documented in various in vitro and in vivo tumor models. The objectives of this Phase I study were to determine the maximum tolerated dose, evaluate toxic effects, and document any antitumor activity of this novel agent. Using an electrospray ionization mass spectroscopy system, we also characterized the clinical pharmacokinetics, pharmacodynamics, and metabolism of DOLA-10. The maximum tolerated dose was reached at 300 microg/m2. Granulocytopenia, the dose-limiting toxicity, was documented in 33% of the patients treated at that dose level. There were no episodes of thrombocytopenia or severe anemia (Hgb < 8), and no major nonhematological toxicity was observed. Stabilization of tumor growth was observed in four patients, but no objective responses were seen. Whereas a two-compartment model described the DOLA-10 plasma concentration-time data reasonably well, a three-compartment model consistently performed better. After a rapid distribution phase, DOLA-10 plasma levels declined with mean beta and gamma half-lives of 0.99 and 18.9 h, respectively. Significant interpatient and intrapatient variability in DOLA-10 plasma clearances was observed. The mean area under the concentration-time curve increased proportionally as the dose was escalated, but there was significant overlap between dose levels. The area under the concentration-time curve and the percentage of decline in neutrophils were correlated. A single DOLA-10 metabolite was detected in five patients. Unlike the in vitro studies of DOLA-10, the principal metabolite detected was an N-demethyl derivative, confirmed by mass spectroscopy. In all five subjects, the concentration of this metabolite never exceeded 2% of the simultaneously measured parent drug concentration. The available preclinical, pharmacological, and clinical data suggest that further study of escalated DOLA-10 dosing with cytokine support is warranted.

Adult↗

PubMed1999

Strategic plan.

Explore the source record for details and available documents.

Humans↗

PubMed1998

Intraocular concentrations of chemotherapeutic agents after systemic or local administration.

OBJECTIVES: To investigate the concentrations of carboplatin and etoposide achieved in the aqueous and vitreous humors after intravenous infusion in nonhuman primates, and to investigate whether local administration of carboplatin might result in higher concentrations in the vitreous humor. METHODS: Macaca fascicularis primates were treated with 1 of 3 regimens: (1) intravenous carboplatin (18.7 mg/kg), etoposide (5 mg/kg), and vincristine sulfate (0.05 mg/kg), (2) peribulbar carboplatin (10 mg/mL), or (3) episcleral balloon carboplatin (10 mg/mL). Concentrations of chemotherapeutic agents were measured in the plasma and in the aqueous and vitreous humors. RESULTS: No measurable amount of etoposide was detected in the aqueous or vitreous humor after intravenous administration. Mean measured peak vitreous concentration of carboplatin after intravenous administration was 0.31 microg/mL, which was 1% of the peak plasma value. Mean measured peak vitreous concentrations of carboplatin after peribulbar or episcleral balloon administration were 2.38 microg/mL and 2.95 microg/mL, respectively, which represent 7.68- and 9.52-fold increases over the concentration achieved after intravenous administration. No serious toxic effect was observed in any animal. CONCLUSIONS: Peribulbar and episcleral balloon administration of carboplatin seemed to be safe and resulted in higher vitreous concentrations than intravenous administration in this model. These results suggest that these alternate routes of delivery should be explored in children with vitreous seeding of retinoblastoma.

Absorption↗

PubMed1998

Quantitation of dolastatin-10 using HPLC/electrospray ionization mass spectrometry: application in a phase I clinical trial.

A highly sensitive and specific assay for the quantitation of the anticancer agent dolastatin-10 (DOL-10) in human plasma is described. The method was based on the use of electrospray ionization-high-performance liquid chromatography/mass spectrometry (ESP-LC/MS). The analytical procedure involved extraction of plasma samples containing DOL-10 and the internal standard (DOL-15) with n-butyl chloride, which was then evaporated under nitrogen. The residue was dissolved in 50 microl mobile phase and 10 microl was subjected to ESP-LC/MS analysis using a C18 microbore column. A linear gradient using water/acetonitrile was used to keep the retention times of the analytes of interest under 5 min. The method exhibited a linear range from 0.005 to 50 ng/ml with a lower limit of quantitation (LLQ) at 0.005 ng/ml. Absolute recoveries of extracted samples in the 85-90% range were obtained. The method's accuracy (< or =5% relative error) and precision (< or =10% CV) were well within industry standards. The analytical procedure was applied to extract DOL-10 metabolites from samples obtained following incubation of the drug with an activated S9 rat liver preparation. Two metabolic products were detected and were tentatively identified as a N-demethyl-DOL-10 and hydroxy-DOL-10. Structural assignments were made based on the fragmentation patterns obtained using the electrospray source to produce collision-induced dissociation (CID). The method was also applied to the measurement of DOL-10 in the plasma of patients treated with this drug. Preliminary investigation of the pharmacokinetics suggested that drug distribution and elimination may be best described by a three-compartment model with t1/2alpha = 0.087 h, t1/2beta = 0.69 h and t1/2gamma = 8.0 h. Plasma clearance was 3.7 l/h per m2.

Antineoplastic Agents↗

PubMed1998

Phase I study of suramin combined with doxorubicin in the treatment of androgen-independent prostate cancer.

In this study, we determined the maximum tolerated plasma concentration of suramin (within the predetermined study target range) when combined with doxorubicin in the treatment of androgen-independent prostate cancer. Twenty-four patients received suramin dosages based on proportional adjustment of the steady-state plasma suramin concentration to achieve the targeted plasma concentrations of 50-100, 101-150, 151-200, or 201-250 microg/ml. Doxorubicin (20 mg/m2) was administered i.v. over 24 h at weekly intervals. Suramin was given i.v. over 2 h twice weekly. Patients received treatment until dose-limiting toxicity or disease progression. Side effects similar to those reported for suramin and doxorubicin administered as individual agents were observed. Dose-limiting motor neuropathy developed in three patients (13%). Twelve of 24 evaluable patients (50%; 95% confidence interval, 28-71%) and 6 of 10 evaluable patients (60%; 95% confidence interval, 26-88%) had a >50% decrease of prostate-specific antigen and measurable lesions, respectively. The maximum tolerated plasma level of suramin when combined with doxorubicin was 151-200 microg/ml. Future studies on suramin combined with doxorubicin or other agents could be performed using a fixed dosing scheme with a targeted suramin steady-state plasma concentration of 200 microg/ml.

Adult↗

PubMed1997

High-performance capillary electrophoresis measurement of dolastatin-10.

A high-performance capillary electrophoresis (HPCE) assay was used to determine the concentration of a potent cytotoxic agent, dolastatin-10, in human plasma. Following extraction from plasma, using a solid-phase C18 cartridge, capillary zone electrophoresis was used to separate, detect and quantitate dolastatin-10 using the structurally related compound dolastatin-15 as the internal standard. Migration times for both dolastatins are less than 20 min. The recovery of the drug was approximately 90% and was quantified over the assay range of 39 to 5000 ng/ml with good precision and accuracy. The method is linear up to 5000 ng/ml with a lower limit of detection of 25 ng/ml. Data resulting from the use of the assay for the in vitro metabolism of the drug are presented. This is the first report of a validated HPCE assay for determining dolastatin-10 levels in human plasma.

Animals↗

PubMed1997

Isolation and characterization of a hemin-regulated gene, hemR, from Porphyromonas gingivalis.

An hemR (hemin-regulated) gene from Porphyromonas gingivalis ATCC 53977 has been isolated and characterized. This gene is present downstream from the prtT gene, previously cloned in this laboratory. In addition, another putative gene, ORF1, was identified between hemR and prtT. The complete nucleotide sequences of ORF1 and hemR were determined, and the deduced amino acid sequence of ORF1 and HemR proteins corresponded to 16- and 48-kDa proteins, respectively. The amino termini of the HemR protein exhibited significant homology with iron-regulated, TonB-dependent outer membrane receptor proteins from various bacteria, while the carboxyl terminus of the HemR protein displayed almost complete identity with a P. gingivalis PrtT protease domain. PCR analyses confirmed the existence of such extensive homology between the carboxyl termini of both the prtT and hemR genes on the P. gingivalis chromosome. Northern blots indicated that ORF1 was part of a 1.0-kb mRNA and was positively regulated by hemin levels. On the other hand, the hemR gene was apparently a part of a 3.0-kb polycistronic message and was negatively regulated at the transcriptional level by hemin. Primer extension analysis of the hemR gene revealed that the transcription start site was at a C residue located within ORF1. An examination of HemR::lacZ constructs in both Escherichia coli and P. gingivalis confirmed hemin repression of hemR expression in both organisms. Moreover, the HemR protein expressed in E. coli was detected by an antiserum from a periodontitis patient heavily colonized with P. gingivalis but not by serum from a periodontally healthy patient or by antisera against hemin-grown P. gingivalis cells. Therefore, it is likely that the 48-kDa HemR protein can be expressed only under hemin-restricted conditions. These results suggest that we have isolated a hemin-regulated gene, hemR, which encodes a 48-kDa protein that may be a TonB-dependent outer membrane protein.

Amino Acid Sequence↗

PubMed1997

Phase I pharmacokinetic study of multicycle high-dose carboplatin followed by peripheral-blood stem-cell infusion in patients with cancer.

PURPOSE: To examine the feasibility of escalating carboplatin area under the concentration-time curve (AUC), using dose predictions based on individual estimates of drug clearance, in a phase I trial of multicycle carboplatin, paclitaxel, and cyclophosphamide chemotherapy with peripheral-blood stem-cell (PBSC) replacement. PATIENTS AND METHODS: Forty-four patients (37 breast, seven ovarian) received 165 courses. Initial target carboplatin AUC was 10 mg/ml x min, with interpatient escalation in increments of 25%. Initial carboplatin dose estimates used creatinine clearance (CrCl) to estimate carboplatin clearance. Subsequent clearance and dose estimates were determined using a model incorporating Bayesian estimation and two measured carboplatin plasma ultrafiltrate concentrations. RESULTS: Median clearance was 80.5 mL/min/m2 (range, 41.6 to 131.8). Carboplatin doses up to 2,440 mg/m2 per course were administered without major extramedullary toxicity. Doses varied 2.6-fold at each exposure level. Using the Bayesian model, AUC was predicted with a mean accuracy of 101.2% (83% using CrCl). Ninety-six of 117 courses were within 25% of the target AUC. This model was less biased (0.15 v -2.35 mg/mL x min) and more precise (2.76 v 3.52) in predicting AUC compared with one using CrCl. Hematologic recovery was not prolonged with increasing exposure. The carboplatin maximum-tolerated systemic exposure (MTSE) was 13.3 mg/mL x min (level five). The dose-limiting toxicity was cardiac toxicity, which occurred at dose levels six and seven. CONCLUSION: Results demonstrate that (1) CrCl is a poor estimator of carboplatin clearance in this population, and (2) the use of a model incorporating limited sampling and Bayesian estimation improves the precision of carboplatin clearance estimation and is suitable for targeting carboplatin exposure in an ambulatory setting.

Ambulatory Care↗

PubMed1997

Phase I study of mitoxantrone plus etoposide with multidrug blockade by SDZ PSC-833 in relapsed or refractory acute myelogenous leukemia.

PURPOSE: Expression of the multidrug resistance gene (MDR1) p170 protein is frequent in leukemic blasts from patients with relapsed acute myelogenous leukemia (AML). A phase I study using the nonimmunosuppressive MDR1 blocker SDZ PSC-833 (PSC) in combination with mitoxantrone (MITO) and etoposide (VP) was performed. PATIENTS AND METHODS: Starting doses (LVL0) of MITO (3.25 mg/m2/d on days 1 and 3 to 6) and VP (210 mg/m2/d on days 1 and 3 to 5) were 40% of the maximal-tolerated dose (MTD) from a prior study. A 1.5-mg/kg loading dose of PSC was followed by a 120-hour continuous infusion of 10 mg/kg/d on days 2 to 6. Blood samples for PSC, MITO, and VP pharmacokinetics (PK) were taken on days 1 and 3, and samples for MDR1 expression were taken on day 0. RESULTS: Severe mucositis developed in all patients at LVL0; therefore, MITO and VP doses were reduced to 2.5 and 170 mg/m2 (LVL-1) for the next seven patients, and this dose proved to be MTD. All LVL0 and three LVL-1 patients had transient elevations in the serum bilirubin level to > or = 4 mg/dL. Serum creatinine level increased to greater than 2 mg/dL in one case. There were no other grade 3 or 4 nonhematologic toxicities observed. The peripheral blood was cleared of leukemia in three LVL0 and four LVL-1 patients. The marrow was cleared of leukemic cells in one LVL0 and five LVL-1 patients, and a significant reduction in marrow leukemic infiltrate was observed in eight of 10. No patient achieved complete remission (CR), and all died of progressive disease (n = 8) or infection (n = 2). MDR1 expression was detected by fluorescent-activated cell sorter (FACS) analysis in five of seven cases. An elevated MDR1 mRNA level was detected by quantitative polymerase chain reaction (Q-PCR) in six of eight cases studied. Clearing of leukemia cells from the marrow occurred in four of six MDR1-positive and one of three MDR1-negative patients. Despite the fact that LVL0 doses had to be reduced due to toxicity, coadministration of PSC did not produce a consistent effect on MITO PK; however, it did repeatedly lead to increased levels of VP in the serum. CONCLUSION: We conclude that PSC-MITO-VP is a tolerable regimen with antileukemic activity. Addition of PSC necessitated a 66% reduction in MITO and VP doses from a prior study without PSC.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1996

Effective clearance of methotrexate using high-flux hemodialysis membranes.

We report the first series demonstrating effective clearance of methotrexate using acute intermittent hemodialysis with a high-flux dialyzer. The study was performed on six patients, two females and four males aged 13 to 72 years. All were patients at M.D. Anderson Cancer Center. Patients were dialyzed for 4 to 6 hours daily using a Fresenius F-80 membrane (Fresenius Inc, Walnut Creek, CA). Following the initiation of dialysis, there was a reduction in arterial and venous serum concentration of methotrexate with time. Mean plasma clearance of methotrexate during dialysis in these six patients was 92.1 +/- 10.3 mL/min. One patient who was nearly functionally anephric was studied in detail. In this patient, following a high dose of methotrexate (7.2 g/m2), approximately 63% of this dose was cleared with 6 hours of hemodialysis. With subsequent dialysis performed daily for 6 hours, the drug was cleared completely in 5.6 +/- 0.3 days (n = 7 separate methotrexate treatments). A reduction in plasma methotrexate concentration from 1,733 +/- 40 micromol/L 1 hour postinfusion to less than 0.3 micromol/L in 5 to 6 days was observed for these seven separate treatments. We conclude that significant clearance of methotrexate can be achieved with high-flux dialyzers, making methotrexate therapy a viable treatment option in patients with responsive malignancies despite the presence of renal failure.

Adolescent↗

PubMed1996

Organic acid excretion by Streptomyces lividans TK24 during growth on defined carbon and nitrogen sources.

Cultures of Streptomyces lividans TK24 grown in defined media containing certain rapidly used carbon and nitrogen sources excreted high levels of organic acids. These were identified by HPLC and enzymic assays as pyruvic acid and 2-oxoglutaric acid. Acidification occurred only with glucose as the principal carbon source, and depended on the nitrogen source used. With nitrate as the sole nitrogen source, high levels of pyruvate and small amounts of 2-oxoglutarate were produced. Carbon from D[U-14C]glucose was converted into both organic acids. Combining glucose with a selection of amino acids as primary nitrogen/secondary carbon sources yielded less pyruvate and more 2-oxoglutarate. Carbon from both 14C-labelled glucose and amino acids was metabolized to both organic acids. Adding nitrate to this combination caused a reversion of the acid production pattern to that of the glucose-nitrate combination, as if the amino acids were absent. Addition of ammonium salts to any combination of carbon and nitrogen sources completely prevented organic acid formation.

Biotechnology↗