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Biomedical subjects

M Sasada

Publications and source records attributed to M Sasada.

At least 91 records · Page 5Linked to original sources
PubMed1983

Pharmacokinetics of N4-behenoyl-1-beta-D-arabinofuranosylcytosine in patients with acute leukemia.

N4-Behenoyl-1-beta-D-arabinofuranosylcytosine (BHAC), a lipophilic and deaminase-resistant derivative of 1-beta-D-arabinofuranosylcytosine (ara-C), was studied pharmacologically in patients with acute leukemia. The concentrations of BHAC, ara-C, and 1-beta-D-arabinofuranosyluracil were measured by high-performance liquid chromatography, bioassay, and gas chromatography-mass spectrometry-mass fragmentography, respectively. The data of plasma BHAC concentrations were analyzed by a MULTI computer program. In seven patients given BHAC (200 mg/body weight; 2.97 to 4.26 mg/kg) i.v. for 90 min, the plasma disappearance curve of BHAC was biphasic with a mean initial half-life of 0.37 hr and a mean second half-life of 5.27 hr. The apparent volume of the central compartment and the apparent volume of distribution were 0.047 and 0.316 liter/kg, respectively; the systemic clearance was 0.051 liter/hr/kg. BHAC concentrations in erythrocytes were significantly higher (p less than 0.01) than those in plasma at 4 to 22.5 hr after infusion, suggesting that the erythrocytes may act as a reservoir for the drug. The plasma 1-beta-D-arabinofuranosyluracil level increased to 603 ng/ml at 4 hr after infusion, and it was over 129 ng/ml for at least 22.5 hr after infusion. Plasma ara-C levels, which could be detected in only 2 of 11 patients examined, were maintained (over 0.08 micrograms/ml) for 8 hr after infusion. Urinary BHAC excretion was less than 0.2 micrograms/ml of the sensitivity limit in all samples. Prolonged urinary ara-C excretion was detected, but it was only 0.5% of the administered BHAC for 24 hr. At 12 hr after a 200-mg infusion of BHAC, BHAC level in bone marrow fluid was significantly higher (p less than 0.01) than that in plasma. In spite of the lipophilic nature of the agent, the BHAC concentration in cerebrospinal fluid was less than 0.2 micrograms/ml in 8 of 9 patients without meningeal involvement. These findings were thought to indicate a restricted and prolonged BHAC distribution including plasma, blood cells, and bone marrow fluids, which may be of importance in the administration of BHAC in the chemotherapy of hematological cancers.

Acute Disease↗
PubMed1983

Intracellular distribution of N4-behenoyl-1-beta-D-arabinofuranosylcytosine in blood cells.

In order to clarify differences in mode of action between N4-behenoyl-1-beta-D-arabinofuranosylcytosine (behenoyl-ara-C) and 1-beta-D-arabinofuranosylcytosine (ara-C), comparative studies on both agents were undertaken. When human erythrocytes incubated with behenoyl-ara-C[acyl-1-14C] were fractionated into stroma and stroma-free lysate, a marked accumulation of radioactivity in stroma was observed. In contrast, ara-C[cytosine-2-14C] was rapidly incorporated into the stroma-free lysate. Thin-layer chromatography of the extracts of L1210 cells incubated with behenoyl-ara-C[acyl-1-14C] or behenoyl-ara-C[cytosine-2-14C] at 37 degrees for 60 min revealed that most of the incorporated drug remained as unmetabolized behenoyl-ara-C. After incubation of 20 microM behenoyl-ara-C or ara-C with L1210 cells at 37 degrees for 60 min, subcellular fractionation of the cell suspension was performed; behenoyl-ara-C was accumulated markedly in the membrane, mitochondria and microsome fractions. In contrast, most of the ara-C was found in the 105,000g supernatant fraction. The accumulation of behenoyl-ara-C in membrane structures may result from the lipophilic nature of the agent, which may have a prolonged inhibitory action on leukemic cell proliferation.

Animals↗
PubMed1980

Macrophage variants in oxygen metabolism.

Whereas phagocytic cells from normal individuals have the capacity to kill ingested bacteria and parasites, those from patients with several uncommon genetic deficiency diseases are known to be defective in bactericidal activity. Studies on neutrophils of these patients have revealed fundamental defects in their ability to reduce molecular oxygen and metabolize it to superoxide anion, hydrogen peroxide, and oxygen radicals. In the present experiments, we describe a clone of a continuous murine macrophage-like cell line, J774.16, that, upon appropriate stimulation, activates the hexose monophosphate shunt, and produces superoxide anion and hydrogen peroxide. With nitroblue tetrazolium to select against cells capable of being stimulated by phorbol myristate acetate to reduce the dye to polymer--formazan--which is toxic fot cells, we have selected for variants that are defective in oxygen metabolism. Four of these subclones have been characterized and found to be lacking in the ability (a) to generate superoxide anion, as measured by cytochrome c reduction; (b) to produce hydrogen peroxide, as measured by the ability to form complex I with cytochrome c peroxidase; and (c) to be stimulated to oxidize glucose via the hexose monophosphate shunt. These variants appear to represent a useful model for studying the molecular basis for macrophage cytocidal activity.

Animals↗
PubMed1980

Macrophage microbicidal activity. Correlation between phagocytosis-associated oxidative metabolism and the killing of Candida by macrophages.

The mechanisms by which macrophages kill ingested microorganisms were explored using Candida albicans and Candida parapsilosis. The results indicate that efficient macrophage candidacidal activity depends upon the generation of oxygen metabolites by the phagocytic cell: (a) peritoneal macrophages from mice infected with bacillus Calmette-Guerin (BCG) or injected intraperitoneally with lipopolysaccharide (LPS) released more superoxide anion (0(2)(-)) during phagocytosis of candida and killed candida better than did resident macrophages; (b) cells of the macrophage-like line J774.1, which released negligible amounts of O(2)(-), could ingest the candida normally but not kill them; (c) killing of candida by resident, LPS- elicited, and BCG-activated macrophages was inhibited by agents that scavenge O(2)(-), hydrogen peroxide (H(2)0(2)), hydroxyl radical (x OH), and singlet oxygen; and (d) all three macrophage types killed C. parapsilosis more effectively than C. albicans, and (7. parapsilosis stimulated a more prompt and vigorous burst of macrophage oxygen consumption and 0(2)(-) release than did C. albicans. Macrophages ingested C. parapsilosis slightly more quickly than C. albicans, but phagocytosis of both strains was equivalent by 60 min of incubation. Although C. albicans contained higher concentrations of the oxygen-metabolite scavengers superoxide dismutase and catalase, neither fungal species scavenged 0(2)(-) or H(2)0(2) effectively; and C. albicans was killed more easily than C. parapsilosis by a xanthine oxidase system that generates primarily H(2)O(2) at pH 7, or 0(2)(-) and x OH at pH 10. Thus, the decreased killing of C. albicans appears to result primarily from the capability of this species to elicit less vigorous stimulation of macrophage oxidative metabolism. This capability may have general relevance to the pathogenicity of microorganisms.

Animals↗
PubMed1978

DNA repair in human leukemic leucocytes treated with neocarzinostatin.

Neocarzinostatin, an antineoplastic agent which is effective against human leukemia, induced unscheduled DNA synthesis in human leukemic leucocytes. This indicated the existence of repair process against at least a part of DNA damage caused by the agent. The extent of unscheduled DNA synthesis increased in parallel with the concentration of Neocarzinostatin up to 5 microgram/ml, followed by a decline at more than 5 microgram/ml. Leucocytes from patients with chronic myelogenous leukemia had higher repair synthesis after Neocarzinostatin treatment compared to those from patients with acute leukemia. The amount of repair synthesis correlated well with the proportion of immature leucocytes among chronic myelogenous leukemia samples, but such correlation was not found among acute leukemia samples.

Adolescent↗
PubMed1976

Caffeine potentiation on lethality of L-1210 cells treated with neocarzinostatin.

The caffeine potentiation on lethality of L-1210 cells treated with Neocarzinostatin was studied. Colony formation of L-1210 cells treated with Neocarzinostatin was significantly decreased by incubation of the cells for 48 hr with 0.5 mM of caffeine which alone did not affect the growth rate and colony-forming ability of the cells. These results indicate that Neocarzinostatin may induce repairable damage in DNA of L-1210 cells.

Animals↗