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Biomedical subjects

R A Bender

Publications and source records attributed to R A Bender.

At least 91 records · Page 5Linked to original sources
PubMed1978

Phase I study of methanesulfonamide, N-[4-(9-acridinylamino)-3-methoxyphenyl]-(m-AMSA) using a single-dose schedule.

Methanesulfonamide, N-[4-(9-acridinylamino)-30methoxyphenyl]-(NSC-249992), an acridine derivative with significant antitumor activity in animal tumor systems, was administered to 29 patients in a phase I clinical trial. The dose ranged from 10 to 160 mg/m2 with a single dose given every 28 days. The toxic effects included moderate to severe leukopenia and mild thrombocytopenia. Myelosuppression was more severe in patients with prior whole abdominal or pelvic radiotherapy. Superficial phlebitis occurred when the drug was diluted in a volume of less than 500 ml of 5% dextrose in water. Antitumor activity was detected in one patient with ovarian carcinoma. Phase II studies are indicated with this compound since it has reproducible and reversible toxicity with some evidence of antitumor activity. The starting dose of the drug for phase II trials should be 120 mg/m2 as a single iv dose repeated at 4-week intervals.

Acridines↗
PubMed1978

Lack of therapeutic synergism between vincristine and methotrexate in L1210 murine leukemia in vivo.

In vivo studies were performed in mice bearing L1210 ascites tumor to examine the interaction of vincristine (VCR) at doses of 0.15 and 1.5 mg/kg with methotrexate (MTX) at doses of 0.5, 5, 50, and 350 mg/kg. The combination was administered on Days 2, 6, and 10 after tumor inoculation. VCR was given either concurrently with MTX or preceding it by 30, 60, or 120 minutes. VCR administered at a dose of 0.15 mg/kg achieved a peak peritoneal fluid concentration of 1.4 micron declining with a half-life (T1/2) of 33.5 minutes and produced no in vivo augmentation of MTX uptake. VCR administered at a dose of 1.5 mg/kg achieved a peak peritoneal fluid concentration of 16.5 micron declining with a T1/2 of 24.9 minutes and produced significant in vivo augmentation of MTX uptake when given concurrently with the MTX and 30 minutes prior to MTX at a dose of 350 mg/kg. No other interval was associated with augmented MTX uptake. When animal survival was evaluated, no therapeutic synergism was observed at any dose level of either drug in any schedule. In fact, VCR (0.15 and 1.5 mg/kg) and MTX at doses of greater than or equal to 50 mg/kg produced toxic synergism which adversely affected survival. Since the drug doses studied are comparable with those used in "high-dose" clinical protocols, individual tumor evaluation is indicated to support the use of these drugs in combination.

Animals↗
PubMed1978

Lymphography in surgically unresectable adenocarcinoma of the exocrine pancreas.

Bipedal lymphograms were performed on 28 consecutive previously untreated patients with biopsy proven and surgically unresectable carcinoma of the pancreas. Four of these patients had findings indicating lymph nodes metastases. In three of these 4 patients, the lymphogram provided the only evidence of metastatic disease. The information provided by bipedal lymphography may be useful in treatment planning.

Adenocarcinoma↗
PubMed1977

Eosinophilic meningitis complicating Hodgkin's disease. A report of a case and review of the literature.

A case of eosinophilic meningitis as a complication of Hodgkin's disease is reported. Intrathecal chemotherapy with methotrexate and whole brain radiation therapy were effective in clearing the cerebrospinal abnormalities, pathologic evidence of meningeal disease, and the clinical manifestations. The differential diagnosis of eosinophilic meningitis and therapy of lymphomatous meningitis are discussed.

Adult↗
PubMed1977

The pharmacokinetics of [3H]-vincristine in man.

The pharmacokinetics, metabolism, and excretion of aromatically labeled tritiated vincristine (VCR) was examined in 4 patients. Clearance of radioactivity from the blood was triphasic with half-life t1/2 values of 0.85, 7.4, and 164 min. The initial phases probably represent distribution and binding to formed blood elements which exceeded 50% of the administered dose by 20 min. Excretion of radioactivity was principally fecal, with 33% recovered in the feces by 24 hr and 69% by 72 hr. Considerably less radioactivity (12%) was excreted in the urine over the 72-hr period. Approximately 40% of fecally excreted and 46% of urinary excreted radiolabel represented metabolites, which suggests that at least 34% of the VCR dose was excreted as metabolies. Plasma metabolites represented from less than 1% to 30% or more of radioactivity in plasma. Ultraviolet spectral analysis of all metabolites revealed preservation of the intact VCR dimer, which suggests that metabolism involves alteration of side groups.

Adult↗
PubMed1977

Biochemical parameters of glutamine synthetase from Klebsiella aerogenes.

The glutamine synthetase (GS) from Klebsiella aerogenes is similar to that from Escherichia coli in several respects: (i) it is repressed by high levels of ammonia in the growth medium; (ii) its biosynthetic activity is greatly reduced by adenylylation; and (iii) adenylylation lowers the pH optimum and alters the response of the enzymes to various inhibitors in the gamma-glutamyl transferase (gammaGT) assay. There are, however, several important differences: (i) the isoactivity point for the adenylylated and non-adenylylated forms in the gammaGT assay occurs at pH 7.55 in K. aerogenes and at pH 7.15 in E. coli; (ii) the non-adenylylated form of the GS from K. aerogenes is stimulated by 60 mM MgCl2 in the gammaGT assay at pH 7.15. A biosynthetic reaction assay that correlates well with number of non-adenylylated enzyme subunits, as determined by the method of Mg2+ inhibition of the gammaGT assay, is described. Finally, we have found that it is necessary to use special methods to harvest growing cells to prevent changes in the adenylylation state of GS from occurring during harvesting.

Adenosine Monophosphate↗
PubMed1977

Regulatory mutations in the Klebsiella aerogenes structural gene for glutamine synthetase.

Glutamine synthetase could be repressed several hundredfold rather than 6- to 10-fold as previously reported. Ammonia was not the primary repression signal for glutamine synthetase. Repression appeared to be mediated by a high level of glutamine and probably by a high ratio of glutamine to alpha-ketoglutarate. Mutations in glnA (the structural gene for glutamine synthetase) were seen to fall into three phenotypic groups: glutamine auxotrophs that produced no detectable glnA product; glutamine auxotrophs that produced a glnA product lacking enzymatic activity (and hence repressibility by ammonia) but were repressible under appropriate conditions; and glutamine synthetase regulatory mutants, whose glnA product was enzymatically active and not repressible under any conditions.

Ammonia↗
PubMed1977

Autogenous regulation of the synthesis of glutamine synthetase in Klebsiella aerogenes.

We isolated an F' episome of Escherichia coli carrying the glnA+ gene from K. aerogenes and an F' episome of E. coli carrying the glnA4 allele from K. aerogenes responsible for the constitutive synthesis of glutamine synthetase. Complementation tests with these episomes showed that the glnA4 mutation (leading to the constitutive synthesis of active glutamine synthetase) was in the gene identified by mutations glnA20, glnA51, and glnA5 as the structural gene for glutamine synthetase. By using these merodiploid strains we were able to show that the glnA51 mutation lead to the synthesis of a glutamine synthetase that lacked enzymatic activity but fully retained its regulatory properties. Finally, we discuss a model that explains the several phenotypes associated with mutations such as glnA4 located within the structural gene for glutamine synthetase leading to constitutive synthesis of active glutamine synthetase.

Alleles↗
PubMed1977

Peritoneoscopy: a technique to evaluate therapeutic efficacy in non-Hodgkin's lymphoma patients.

Peritoneoscopy was performed in 22 patients with non-Hodgkin's lymphoma as a re-staging technique to rule out relapse or persistence of active disease after intensive chemotherapy and/or radiotherapy. Fifteen patients with previous hepatic involvement achieved a complete clinical remission; however, five patients (33%) had persistent disease proved by biopsy at peritoneoscopy. In seven patients suspected to have a clinical relapse, peritoneoscopy biopsies documented relapse in three patients (43%), including two patients with negative percutaneous liver biopsies. Because of its low morbidity rate (4%), peritoneoscopy can be utilized to re-stage hepatic involvement by non-Hodgkin's lymphoma patients more accurately than percutaneous liver biopsies and with less morbidity than laparotomy.

Humans↗
PubMed1976

In vitro correlates of clinical response to methotrexate in actue leukaemia and Burkitt's lymphoma.

The response of drug-resistant patients with acute leukaemia and Burkitt's lymphoma to treatment with a 24 h infusion of methotrexate (MTX) followed, in some cases,by cytosine arabinoside was correlated with in vitro measurements of total intracellular MTX, exchangeable intracellular MTX, and suppressibility of deoxyuridine (UdR) incorporation in isolated marrow blast cells at extracellular MTX concentrations of 10(-8)M, 10(-7)M, 10(-6)M and 10(-5)M. Total intracellular MTX levels and exchangeable intracellular MTX levels were not significantly different in responding or non-responding patients at any MTX concentration, but increased four-fold for every ten-fold concentration increment studied. Extracellular MTX levels in excess of 10(-7)M appeared necessary to allow accumulation of exchangeable intracellular MTX. UdR incorporation at 10(-6)M and 10(-5)M differed significantly between responding and non-responding patients, with responders having less than 20% of control values and non-responders having greater than 40% of control values. Further, increasing the extracellular MTX concentration from 10(-6)M to 10(-5)M produced no significant decrease in UdR incorporation in either group. The therapeutic implications of this apparent threshold are discussed.

Adolescent↗
PubMed1976

Glutamate dehydrogenase: genetic mapping and isolation of regulatory mutants of Klebsiella aerogenes.

The gene for glutamate dehydrogenase (gdhD) has been mapped in Klebsiella aerogenes by P1 transduction. It is linked to pyrF and trp with the order pyrF-trp-gdh. Complementation analysis using F' episomes from Escherichia coli suggests an analogous location in E. coli. Two mutants able to produce glutamate dehydrogenase in the presence of high levels of glutamine synthetase have been isolated. One, tightly linked to gdhD, shows normal repression control by glutamine synthetase but produces four times as much glutamate dehydrogenase activity as does the wild type under all conditions tested. The other revertant is not linked to gdhD or glnA.

Ammonia↗