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Biomedical subjects

E C Moore

Publications and source records attributed to E C Moore.

At least 37 records · Page 2Linked to original sources
PubMed1983

Studies of N-hydroxy-N'-aminoguanidine derivatives by nitrogen-15 nuclear magnetic resonance spectroscopy and as ribonucleotide reductase inhibitors.

Hydroxyguanidine, with the imino group of guanidine and the hydroxyamino group of hydroxyurea, has functional groups believed to be important for both anticancer and antiviral activities (Adamson, R.H. Nature (London) 1972, 236, 400-401). Three new N-hydroxy-N'-aminoguanidine derivatives have been synthesized and found to be 20-30 times more active than the hydroxyguanidine itself as inhibitors of ribonucleotide reductase from rat Novikoff tumors (Tai, W.A.; Lai, M.M.; Lien, E.J. "Novel N-Hydroxyguanidine Derivatives as Antiviral Agents", North American Medicinal Chemistry Symposium, University of Toronto, Toronto, Canada, June 20-24, 1982; Abstr, p 144). The character of the tautomeric equilibria, the pKa values, and the protonation sites of these hydroxyguanidine derivatives have been determined by 15N NMR spectroscopy.

Guanidines↗
PubMed1983

Pharmacological and biochemical interactions of N-(phosphonacetyl)-L-aspartate and 5-fluorouracil in beagles.

N-(Phosphonacetyl)-L-aspartate (PALA) and 5-fluorouracil (FUra) are both antimetabolites that affect the biosynthetic pathways of pyrimidines. To determine whether these two drugs exhibit synergistic pharmacological or biochemical interactions, we determined the pharmacological and biochemical parameters of PALA and [14C]FUra in 14 beagle dogs which received i.v. bolus administrations of either the single agents or the drug combination. The pharmacokinetic parameters of PALA (four dogs, 20 mg/kg) in plasma, cerebrospinal fluid, and urine were not changed by FUra (10 mg/kg, 30 min after PALA). The pharmacokinetics of [2-(14)C]FUra (six dogs, 10 mg/kg, 20 muCi/kg) was characterized by higher FUra plasma concentrations after pretreatment with PALA (20 mg/kg, 30 min before FUra); this led to a significantly larger area under the drug concentration-time curve, a decreased volume of distribution, and a reduced clearance rate and was associated with higher cerebrospinal fluid concentrations of FUra. The FUra plasma and cerebrospinal fluid half-lives, however, were not significantly altered by PALA. The biochemical determinants of PALA and FUra activity were studied in intestinal mucosa, liver, thymus, spleen, and bone marrow of four dogs. Although the activity of the target enzyme of PALA, L-aspartate carbamoyltransferase, in tissue extracts was decreased at least 50% at 18 to 24 hr after PALA administration (50 mg/kg), the uridine nucleotide pools remained remarkably stable. Intracellular FUra concentrations were not influenced by PALA. The incorporation of 5-fluorouridine triphosphate into RNA was enhanced in intestinal mucosa and liver. In other tissues, however, fluorouridine nucleotide concentrations were not affected by PALA. Free 5-fluorodeoxyuridine monophosphate had the highest concentration in liver and was detectable in all tissues, but it was not altered by PALA treatment. Our results show that the pharmacological and biochemical events after FUra exposure are marginally modulated by PALA in normal dogs. If sensitive tumors with a higher degree of interaction between the two drugs could be identified, limited toxicity to normal tissues can be expected.

Animals↗
PubMed1982

N-(Phosphonacetyl)-L-aspartate inhibition of the enzyme complex of pyrimidine biosynthesis.

The inhibition of aspartate carbamoyltransferase (ACTase) from rat Novikoff tumor by N-(phosphonacetyl)-L-aspartate (PALA) was studied in a substrate mixture permitting endogenous synthesis of carbamoyl phosphate. Among the components required for carbamoyl phosphate synthetase activity, ATP, Mg(C2H3O2)2 and KCl interfered with inhibition by PALA (with added carbamoyl phosphate). The inhibition was also decreased when the concentration of partially purified enzyme was increased. In the system dependent on carbamoyl phosphate synthetase, the 50% inhibitory concentration of PALA was lower than that in the same mixture plus 0.2 mM carbamoyl phosphate, but higher than in the usual simple assay mixture with 0.2 mM carbamoyl phosphate.

Adenosine Triphosphate↗
PubMed1982

Aspartate carbamoyltransferase activity, drug concentrations, and pyrimidine nucleotides in tissue from patients treated with N-(phosphonacetyl)-L-aspartate.

Biopsy specimens were obtained from patients treated with N-(phosphonacetyl)-L-aspartate (PALA) in a phase I clinical trial. Activities of aspartate carbamoyltransferase (ACTase), the target enzyme, in ten specimens before treatment varied from 0.4 to 1.7 units/mg. PALA was measured in protein-free extracts of thirteen specimens by inhibition of rat ACTase. At 1.5 to 145 hr after doses of 1 to 6 g/m2, PALA concentrations were 0.9 to 89 micrograms/g; at 4 hr or later the tissue concentrations were similar to those in plasma (five samples). The observed inhibition of ACTase (17-87%) correlated with the PALA concentrations. Pyrimidine nucleotides were decreased (relative to purine nucleotides) in nine to ten specimens, by 16-72%. ACTase partially purified from human spleen had a Km for carbamoyl phosphate of 20.6 microM and the Ki for PALA was 0.011 microM. The results suggest that inhibition of ACTase by PALA affects the concentration of pyrimidine nucleotides in human tumors in a dose-dependent manner.

Antimetabolites, Antineoplastic↗
PubMed1980

Pharmacological disposition of N-(phosphonacetyl)-L-aspartate in humans.

The pharmacological disposition of N-(phosphonacetyl)-L-aspartate (PALA), an antitumor transition state analog currently in clinical trial, has been studied in 19 patients after i.v. administration of the agent at doses ranging from 800 to 5000 mg/sq m; PALA in biological specimens was assayed enzymatically, advantage being taken of its inhibition of L-aspartate carbamoyltransferase (EC 2.1.3.2) PALA disappeared from plasma biexponentially, with an average terminal t 1/2 of 5.3 hr. It was excreted in the urine unchanged; the 24-hr cumulative excretion was 85% of the administered dose. The average total clearance was 1.60 ml/kg/min and was linearly related to creatinine clearance, suggesting that in humans PALA is essentially cleared by glomerular filtration. The apparent volume of distribution of PALA was 309 ml/kg, approximately the sulfate space in humans. PALA penetrated into the central nervous system only to a limited extent. Tumor L-aspartate carbamoyltransferase activity was also measured before and 1.5 hr to 6 days after PALA administration; in all eight studies, a notable decrease in enzyme activity was observed.

Aspartate Carbamoyltransferase↗
PubMed1980

Penetration of N-(phosphonacetyl)-L-aspartate into human central nervous system and intracerebral tumor.

Cerebrospinal fluid (CSF) was obtained from five patients by lumbar puncture and from two patients by Ommaya reservoir tap after the i.v. administration of the antitumor agent N-(phosphonacetyl)-L-aspartate (PALA). PALA was quantified enzymatically by inhibition of the target enzyme, aspartate carbamoyltransferase. After a 1-hr infusion of PALA, its CSF concentration steadily rose until the eighth hr, at which time it was 12 to 40% of concurrent plasma concentration. PALA concentration then declined more gradually in CSF than in plasma, and CSF concentrations exceeded plasma concentrations by 24 hr. PALA concentration X time product in CSF was 12 to 25% of that in plasma. PALA was infused i.v. for 30 to 60 min into eight patients undergoing surgical resection if intracerebral tumors. Its concentration in intracerebral tumor was greater than or comparable to concentration in temporalis muscle in four of six patients from whom muscle was obtained. The PALA concentration in edematous brain tissue was consistently lower than the concentration in tumor or muscle. In a patient undergoing occipital lobectomy, the PALA concentration in brain was inversely proportional to the distance from the tumor. PALA reached concentrations in intracerebral tumor that appeared to be similar to concentrations reported previously in s.c. tumors, although biopsy techniques and conditions differed.

Aspartic Acid↗
PubMed1979

Regional deficiency of secretory IgA in a patient with combined immunodeficiency of the ADA deficient type.

The IgA system in a patient with SCID and ADA deficiency showed heterogeneity. Serum IgA and stool secretory IgA (SIgA) levels were normal, but with altered kappa/lambda and A1/A2 subclass ratios; IgA in saliva and urine was deficient. Amounts of secretory component were normal. Jejunal and rectal biopsies showed prominent lymphonodular hyperplasia, but no cells containing IgA. A normal serum IgA level therefore does not always predict an intact secretory IgA system.

Adenosine Deaminase↗
PubMed1979

Enzymatic assay for the antitumor agent-N-(phosphonacetyl)-L-aspartic acid (PALA).

A method is described for the assay of N-(phosphonacetyl)-L-aspartic acid in plasma or urine, based on inhibition of partially purified aspartate carbamoyltransferase from rat liver. Concentrations of N-(phosphonacetyl)-L-aspartic acid as low as 0.1 microgram/ml can be detected. Plasma disappearance and urinary excretion curves from one patient are shown as examples of the application of the method.

Animals↗
PubMed1978

Comparison of thioredoxin reductases from Novikoff ascites hepatoma cells and normal liver of rats.

Adult rat liver contained variant forms of thioredoxin reductase with isoelectric points at pH 4.9 and at approximately pH 4.7 compared to pH 5.1 for the enzyme from Novikoff ascites hepatoma. Fetal and regenerating liver contained only the form with the isoelectric point at pH 4.9. All three enzymes precipitated with and were inhibited by a rabbit antibody to purified enzyme from Novikoff tumor.

Animals↗
PubMed1977

Solvent-dependent conformational system of hydroxyureas in octanol-water and in inhibition of ribonucleotide reductase.

The carbonyl nitrogen IR absorption region of selected hydroxyureas was examined in octanol. The spectra indicated appreciably different absorptions prior to and after equilibration with water. Stability studies on the hydroxyureas indicated that the absorption differences were not due to chemical decomposition in the equilibration process but were due to solvent conformation and/or tautomeric dependency of the system. Preliminary in vitro inhibition of the enzyme ribonucleoside diphosphate reductase by selected hydroxyureas also indicated an apparent solvent dependency, which may involve the conformational and/or tautomeric properties of these agents. The implications of the solvent-dependent conformation-tautomeric system observed are discussed in relation to this property in the biological action of these agents.

Chemical Phenomena↗
PubMed1977

Effect of the solvent-dependent conformational system of hydroxyureas on predicted vs. observed log P.

Calculated and observed log P values are reported and compared with in vivo and in vitro biological action (L1210 leukemia ILS % and ribonucleotide reductase ID50) for hydroxyurea, the 1-N methyl and ethyl, and the 3-N ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, phenyl, and p-chlorophenyl analogues. The log P values were calculated via the method of Hansch and Leo from literature f values and the observed log P values were obtained by direct determination after equilibration between octanol and water. Calculations of log P for hydroxyurea were found to be appreciably more hydrophilic than the values obtained experimentally. Differences in calculated and observed log P (delta log P) for the substituted analogues were lowest with the 1-N and the bulky 3-N substituents and greatest with the 3-N-substituted straight-chain analogues (delta log P = 0.70). Different structural species were observed by infrared spectroscopy in dry octanol vs. octanol after water equilibration and drying, and this is proposed as due to changes in conformational equilibrium in the hydroxyurea systems. Differences between calculated and observed log P are explained via the stabilization of internally hydrogen-bonded conformers in the case of 1-N or bulky 3-N analogues or destabilization of various conformers allowing maximal interactions with solvent or water which is the case with straight chain 3-N analogues.

Chemical Phenomena↗
PubMed1977

Purification of thioredoxin reductase from the Novikoff rat tumor.

Thioredoxin reductase (E.C.1.6.4.5.) has been purified to about 95% homogeneity from the Novikoff ascites rat tumor. The enzyme contained two subunits of approximately 58,000 daltons, with one FAD per subunit. The amino acid analysis is reported. An immunoadsorbent was prepared and used for affinity chromatography in order to improve the yield of the enzyme.

Amino Acids↗
PubMed1977

4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone, a second-generation antineoplastic agent of the alpha-(N)-heterocyclic carboxaldehyde thiosemicarbazone series.

4-Methyl-5-amino-1-formylisoquinoline thiosemicarbazone (MAIQ-1) was studied to determine its potential for clinical trail as a second-generation antineoplastic agent of the alpha-(N)-heterocyclic carboxaldehyde thiosemicarbazone class. MAIQ-1 was shown to be among the most potent known inhibitors of the major target for the expression of antineoplastic activity by this class of agents, the enzyme ribonucleoside diphosphate reductase, requiring only 0.06 micronM for 50% inhibition. This potency at the enzymatic level was consistent with its antineoplastic activity against the murine neoplasms Sarcoma 180, Leukemia L1210, Leukemia P388, and the B16 melanoma. The acetylation of the 5-amino group of the model substrate 5-amino-1,4-dimethylisoquinoline was lower than that of 5-amino-1-methylisoquinoline when incubated with acetyl-coenzyme A and rat liver homogenate. This finding suggests that the presence of the 4-methyl function offers steric hinderance to enzymatic substitution of the adjacent 5-amino group. In vivo metabolism of MAIQ-1 in mice, studied with [3'-14C]MAIQ-1 showed that relatively slow excretion of this agent occurred, since the cumulative urinary excretion of radioactivity was only 35% in 48 HR. About 51% of excreted urinary radioactivity was present in chromatograms in an area corresponding to the iron chelate of MAIQ-1, and only a minor quantity of material migrating like acetylated MAIQ-1 was present in urine, a finding consistent with enzymatic data with liver homogenates. The results indicate that MAIQ-1 has the antineoplastic activity, enzyme inhibitory potency, and relative resistance to metabolic inactivation required of an agent of this class for clinical trials.

Animals↗
PubMed1976

Independent fluctuations of cytidine and adenosine diphosphate reductase activities in cultured Chinese hamster fibroblasts.

The activities of CDP and ADP reductases were determined throughout the cell cycle of Chinese hamster fibroblasts synchronized by partial deprivation of isoleucine. Both enzyme activities were increased in S phase as compared to G1 phase. CDP reductase increased about 8-fold while ADP reductase increased about 2.5-fold. The ratio of CDP to ADP reductase was 0.26 at the G1 and early S phases of the cell cycle; the ratio was increased to 0.83 by late S phase. Addition of actinomycin D or cycloheximide to cell cultures in G1 phase prevented the increase of both CDP and ADP reductases activities in the latter part of the cell cycle, but the ratio of the two activities was not affected. The ratio of CDP to ADP reductase activities varied from 0.8 to 3 in different populations of exponentially growing DON cells. These results show that CDP and ADP reductase activities vary independently in growing cells. The independent variation with cell growth of CDP and ADP reductases suggests important individual functions of the deoxynucleotides during the cell cycle apart from their common role as precursors of DNA synthesis.

Adenosine Diphosphate↗