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J D Berman

Publications and source records attributed to J D Berman.

At least 73 records · Page 4Linked to original sources
PubMed1987

Uptake, distribution, and oxidation of fatty acids by Leishmania mexicana amastigotes.

Fatty acid uptake, distribution, and beta-oxidation were investigated in Leishmania mexicana amastigotes. The uptake of radiolabeled palmitic, stearic, and oleic acids was similar, reaching 3-6 nmol/10(8) cells in 2 min and 8-12 nmol/10(8) cells in 60 min. The percent of radiolabeled fatty acid that was esterified in the form of triglycerides or phospholipids increased from less than 25% at 2 min to 65-86% at 60 min. The dehydrogenase(s) in an amastigote granule fraction were unusual in that the Vmax for long-chain substrates (0.95-1.6 delta Abs units/min-mg protein) approximated the Vmax for short-chain substrates (0.82-2.0 delta Abs units/min-mg protein), and the Km for long-chain substrates was high (approximately 250 microM), in contrast to data for a mammalian liver mitochondrial fraction. The high Vmax and Km for long-chain substrates suggest a biochemical mechanism for the postulated high utilization of fatty acids as an energy source for amastigotes. Although the primary anti-leishmanial agent, Sb in the form of Pentostam, inhibited oxidation of palmitic acid to CO2 by intact organisms, Sb did not significantly inhibit fatty acid uptake or esterification by organisms, or beta-oxidation by the granule fraction, and the mechanism of action of Sb remains unclear.

Acyl-CoA Dehydrogenase↗
PubMed1986

Effects of ketoconazole on sterol biosynthesis by Leishmania mexicana mexicana amastigotes in murine macrophage tumor cells.

Murine macrophage tumor cells infected with Leishmania mexicana mexicana were exposed to the antimycotic drug ketoconazole and to [2-14C]mevalonate, then the amastigotes were isolated, collected, purified, and their free sterols were analyzed by chromatographic and mass spectrometric methods. Control amastigotes contained as products of de novo biosynthesis C28 4-desmethyl sterols (episterol, 5-dehydroepisterol), C29 4-desmethyl sterols (stigmasta-7,24 (28)-dien-3 beta-ol, stigmasta-5,7,24(28)-trien-3 beta-ol), 4-methyl sterols (4 alpha, 14 alpha-dimethylzymosterol, obtusifoliol) and a 4,4-dimethyl sterol (lanosterol). Present also were macrophage sterols (cholesterol, desmosterol) and a putative product of the C-24 alkylation of desmosterol by amastigotes (24-methylenecholesterol). Amastigotes from macrophages exposed to ketoconazole showed notable changes in the proportions, concentrations and specific activities of their free sterols; increased for 4 alpha, 14 alpha-dimethylzymosterol and decreased for the endogenous C28 and C29 4-desmethyl sterols. Such changes were observed at a ketoconazole concentration as low as 0.01 microgram ml-1. By contrast, uninfected macrophages accumulated only small amounts of lanosterol of high specific activity at a ketoconazole concentration of 10 micrograms ml-1. the ketoconazole-induced alterations in amastigote sterols parallel those previously reported in fungi and L. m. mexicana promastigotes, and suggest a biochemical mechanism for the anti-leishmanial activity of the drug in which changes in sterol composition are linked to disturbances of cell membrane structure and function, and hence to cytotoxicity.

Animals↗
PubMed1986

Antileishmanial activity of liposome-encapsulated amphotericin B in hamsters and monkeys.

Visceral leishmaniasis (kala-azar) results from parasitization of the macrophages of the liver, spleen, and the rest of the visceral reticuloendothelial system with Leishmania donovani. Pentavalent antimony is the drug of choice for leishmaniasis chemotherapy; amphotericin B (AmB) is active but is rarely used, because of drug toxicity. AmB encapsulated within macrophage-directed carriers (liposomes) has been used to treat humans with systemic mycoses complicating neoplastic diseases; dosages of up to 5 mg of encapsulated AmB per kg per day for greater than 14 days are without apparent kidney or liver toxicity. In the present work, greater than 99% of L. donovani parasites were eliminated from the liver and spleen of infected hamsters by one administration of 1.5 to 11 mg of liposome-encapsulated AmB (L-Amb) per kg. A total of 98 to 99% of hepatosplenic parasites were eliminated from squirrel monkeys by three administrations of 4 mg of L-AmB per kg. L-AmB was 170 to 750 times as active as antimony in hamsters, and approximately 60 times as active as antimony in monkeys. The demonstration that apparently nontoxic human dosages of L-AmB eliminate essentially all hepatosplenic parasites in hamster and primate models suggests that this preparation should be considered for clinical trial against kala-azar.

Amphotericin B↗
PubMed1986

Activity of pentamidine-containing human red cell ghosts against visceral leishmaniasis in the hamster.

A recent approach to the chemotherapy of visceral leishmaniasis has been the encapsulation of clinical agents within macrophage directed carriers such as liposomes. Because in mammals Leishmania are obligate intramacrophage microorganisms, injection of an encapsulated drug should deliver large quantities of drug to the organisms, thus decreasing both the number of drug administrations needed for cure and drug toxicity. Drugs contained within red cell ghosts have been used clinically to treat other macrophage disorders. We encapsulated the clinical antileishmanial agent pentamidine within human red cell ghosts and administered it to hamsters infected with Leishmania donovani. The ED50 and ED90 of single injections of this preparation were 231-240 times lower than that of the positive control drug, sodium stibogluconate (Pentostam), and essentially all parasites could be eliminated by 2.5 mg encapsulated drugs/kg. Against splenic parasites, the ED50 was 195 times lower than that of antimony, although only 80% of parasites were eliminated by the highest doses of encapsulated drug (2.5-6.4 mg/kg). The difference in liver vs. splenic parasite killing is probably related to the greater uptake of encapsulated drug by the liver (11-14 micrograms/g tissue) vs. the spleen (2-3 micrograms/g). If activity in this model is comparable to activity in humans, these results suggest that a single injection of a preparation consisting of ghosts of a patient's own red cells and the amount of pentamidine in one standard dosage (4 mg/kg) would eliminate 80%-100% of L. donovani from the spleen and liver.

Amidines↗
PubMed1985

Antileishmanial activity of human red blood cells containing formycin A.

Formycin B is the most active antileishmanial agent in vitro because it is metabolized by the parasites to formycin A phosphates. The in vivo use of formycin B may be limited by its toxicity to humans due to the slight similar metabolism of the drug in human cells. The obligatory intramacrophage localization of Leishmania in man suggests that encapsulation of drugs within macrophage-directed carriers, such as human red blood cells (RBCs), might enhance the therapeutic-toxic ratio. Since uncharged formycin B would be poorly metabolized by the RBC and would diffuse from the carrier, RBCs were incubated with formycin A so that approximately 90% of the formycin A was taken up by the cells, phosphorylated by RBC enzymes to charged formycin A triphosphate, and retained in the cells. In vitro, 81% of Leishmania-infected macrophages phagocytized IgG-coated RBCs containing this active form of formycin B, and multiplication of organisms within macrophages could be suppressed by approximately 80%. The 50% effective dose of the formycin A-RBC formulation was 0.02 microM, whereas the 50% effective dose of unencapsulated drug was 0.84 microM. This report of in vitro activity of human RBCs containing formycin A and coated with IgG indicates that this formulation should be tested for antileishmanial activity in vivo.

Animals↗
PubMed1985

Biochemical mechanisms of the antileishmanial activity of sodium stibogluconate.

Pentavalent antimonial agents such as sodium stibogluconate (Pentostam; Burroughs Wellcome Co., London, United Kingdom) are the drugs of choice for the treatment of leishmaniasis, but their biochemical mechanisms of action are virtually unknown. The viability of Leishmania mexicana (WR 227) promastigotes and amastigotes was decreased 40 to 61% by a 4-h exposure to 500 micrograms of Sb (in the form of stibogluconate) per ml. Such exposure also resulted in a 51 to 65% decrease in incorporation of label into DNA, RNA, and protein; a 56 to 65% decrease in incorporation of label into purine nucleoside triphosphate; and a 34 to 60% increase in incorporation of label into purine nucleoside monophosphate and diphosphate. It is postulated that the apparent decrease in ATP and GTP synthesis from ADP and GDP contributes to decreased macromolecular synthesis and to decreased Leishmania viability. Further experiments suggested that inhibition of glycolysis and the citric acid cycle may partially explain the inability to phosphorylate ADP.

Adenine Nucleotides↗
PubMed1985

Semiautomated assessment of in vitro activity of potential antileishmanial drugs.

We have compared the in vitro activity of six agents against macrophage-contained Leishmania tropica amastigotes determined by the conventional Giemsa staining procedure, with the activity determined by the semiautomated assessment of incorporation of radiolabeled uracil into the nucleic acid of the organisms. Although the mean 50% effective dose of Pentostam by Giemsa staining (4.1 micrograms/ml) was somewhat higher than that by uracil incorporation (2.8 micrograms/ml), the ED50S for the other two clinical agents (pentamidine, 0.035 versus 0.037 micrograms/ml; amphotericin B, 0.67 versus 0.70 micrograms/ml) and for three promising experimental agents (ketoconazole, 11.3 versus 11.3 micrograms/ml; the 8-aminoquinoline WR 6026, 1.6 versus 1.5 micrograms/ml formycin B, 0.018 versus 0.017 micrograms/ml) were virtually identical. The radiolabeling technique has several advantages over the Giemsa staining procedure. These include the need for relatively few macrophages, rapid and objective data generation, and viability of the test organism being measured. The successful application of the radiolabeling technique to at least six different chemical classes of compounds suggests that it would be useful for the routine assessment of antileishmanial activity in vitro.

Aminoquinolines↗
PubMed1985

American cutaneous leishmaniasis: a comparison of three sodium stibogluconate treatment schedules.

Thirty-six patients with American cutaneous leishmaniasis were randomized to receive intravenous sodium stibogluconate for 10 days at a dose of 600 mg antimony (Sb) per day by one of three schedules: once daily by rapid infusion (A), by continuous 24 hr infusion (B), or in divided doses every eight hours by rapid infusion (C). Patients not cured after initial treatment were rerandomized to one of the other treatment schedules. An additional 19 patients who were not part of the randomized study received standard (STD) sodium stibogluconate treatment (600 mg Sb once daily by rapid infusion for 10 days, identical with schedule A). In the randomized study, the overall cure rate after the first course of treatment was 64%, but was higher for schedule A (100%) than for B (50%) or C (42%) (P less than 0.01). Considering all courses of treatment, schedule A was more effective (94%) than B (53%) or C (43%) (P less than 0.01). Paradoxically, patients in group A had a higher cure rate than patients in group STD (42% after the first course of treatment and 51% when all courses of treatment were considered). Side effects were mild and well tolerated. Total side effects were more frequent in groups B + C (52%) than A + STD (23%) due to an increased incidence of subjective complaints (26% vs. 10%, P less than 0.05) in patients receiving other than once daily rapid infusion. We conclude that giving the same total amount of sodium stibogluconate in three divided doses or by continuous infusion offers no advantage over standard, once daily treatment of American cutaneous leishmaniasis.

Antimony Sodium Gluconate↗
PubMed1984

Effects of ketoconazole on growth and sterol biosynthesis of Leishmania mexicana promastigotes in culture.

Ketoconazole, a clinically effective antimycotic agent active in vitro against the amastigote stage of Leishmania mexicana Walter Reed 227 in human monocyte-derived macrophages, was found to inhibit growth and impair sterol biosynthesis of the cultured promastigote stage by approx. 50% at a concentration of approx. 10(-8)M. Sterol biosynthesis was interfered with at the level of the removal of the 14 alpha-methyl group of lanosterol, as judged by changes in the distribution of [2-14C]mevalonate radioactivity among desmethyl sterol and methyl sterol thin-layer chromatography fractions, by the loss of 4-desmethyl sterols (mainly 5-dehydroepisterol), and by the accumulation of 14 alpha-methyl sterols. The growth inhibition and sterol changes were evident in promastigotes cultured in a cholesterol-rich medium and in a cholesterol-poor medium, even though promastigotes incorporated cholesterol. The mechanism of action of ketoconazole against promastigotes may be that postulated for Candida albicans: interference with membrane permeability secondary to loss of desmethyl sterols and accumulation of 14 alpha-methyl sterols.

Animals↗
PubMed1984

Fine structural alterations in Trypanosoma rhodesiense grown in vitro, treated with WR 163577.

Fine-structural alterations in Trypanosoma rhodesiense trypomastigotes exposed to WR 163577, a prophylactic agent against animal African trypanosomiasis, were determined from cells grown in vitro. Exposure of trypomastigotes to a low concentration of drug resulted only in condensation of kinetoplast DNA fibrils. Exposure to higher drug concentrations caused clumping of nuclear chromatin and of cytoplasmic contents. Although alteration of kinetoplast DNA is the first detectable drug-induced change, the function of the kinetoplast in mammalian forms of African trypanosomes is unclear, and the secondary changes in the nucleus and cytoplasm may constitute the functionally significant alterations caused by WR 163577.

Aminoquinolines↗
PubMed1984

Activity of immunoglobulin G-coated red cell ghosts containing pentamidine against macrophage-contained Leishmania in vitro.

Pentamidine is an antileishmanial agent that is often toxic at therapeutic dosages. The obligate intramacrophage localization of Leishmania indicates that encapsulation of pentamidine within a carrier phagocytized by macrophages (IgG-coated sheep red cell ghosts) might improve activity. In in vitro experiments, treatment of infected mouse macrophages for 1 hour with a mean of 1.4 micrograms of encapsulated drug resulted in a calculated drug concentration of 180 micrograms/ml macrophage, and in 73% suppression of organism multiplication within the macrophages after 4-5 days of further cultivation. In comparison, 27 micrograms unencapsulated drug/ml was needed for similar suppression. Electron microscopic examination 5 hours after phagocytosis of IgG-ghosts revealed that 95% of organisms were adjacent to ghosts in phagolysosomes. Fusion of drug carrier with phagolysosome containing drug target is therefore an important step in carrier-mediated parasite suppression in this model. These results suggest that IgG-coated erythrocyte ghosts containing pentamidine have potential as an antileishmanial formation.

Amidines↗
PubMed1984

Evaluation of the 4-pyridinemethanol WR 180,409 (enpiroline) in the treatment of induced Plasmodium falciparum infections in healthy, non-immune subjects.

WR 180,409 (enpiroline) was administered to 22 non-immune subjects infected with the multi-drug resistant Vietnam Smith isolate of Plasmodium falciparum. It was curative in single day treatment regimens with a minimum curative dose of approximately 10 mg/kg body weight. At this dose level it was well tolerated and produced rapid clearance of parasitemia in every case.

Adolescent↗
PubMed1984

Activity of antileishmanial agents against amastigotes in human monocyte-derived macrophages and in mouse peritoneal macrophages.

Leishmania multiplying within either human monocyte-derived macrophages (HM) or mouse peritoneal exudate cells (PEC) have recently been shown to be susceptible to pentavalent antimony (Sb) by several investigators. The Sb susceptibilities of 5 cutaneous strains of Leishmania were compared in the 2 model systems, with infection of the macrophages initiated with either amastigotes or promastigotes. The susceptibility to Sb of amastigote-induced infections was statistically the same as the susceptibility of promastigote-induced infections for 4 strains in the PEC model, and for 3 of 4 strains in the HM model. Promastigote-induced infections with the 5th strain were non-viable in both macrophage types. The susceptibility of Leishmania to Sb within PEC was the same statistically as that of organisms within HM for amastigote-induced infections for 4 of 5 strains and for promastigote-induced infections by 3 of 4 strains. These data suggested that the susceptibilities of organisms to Sb within PEC and HM were generally comparable and that either amastigotes or viable promastigotes could be used to initiate the infection. The several technical advantages of the PEC model may make it more useful than the HM model for testing susceptibility to Sb. The modest susceptibility of some strains in both models to the peak serum amounts of antimony which may be achieved by presently recommended treatment regimes may partially explain the high current failure rate in simple cutaneous disease. The susceptibility of one strain within peritoneal cells to primaquine and WR 6026 (8-aminoquinolines), ketoconazole (an imidazole) and formycin B (an inosine analogue) was similar to that previously reported in human macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoquinolines↗
PubMed1984

The effect of formycin B on mRNA translation and uptake of purine precursors in Leishmania mexicana.

Formycin B is a structural analog of inosine that is a potent inhibitor of Leishmania multiplication. Formycin B is reportedly converted to formycin A nucleotides and incorporated into RNA by the organisms, and it is unclear whether the active form of the drug is the nucleoside itself or its several metabolites. We confirmed that formycin A nucleotides are formed by formycin B-exposed L. mexicana promastigotes, and determined that the intraparasite concentration of Formycin B and its metabolites was 6 times the extracellular formycin B concentration. Formycin B did not significantly inhibit purine nucleoside transport by intact promastigotes or purine base phosphoribosylation by parasite lysates. Thus, the nucleoside does not appear to inhibit these initial steps of purine nucleoside metabolism. Since RNA and protein synthesis in formycin B-treated intact promastigotes was found to be inhibited within 30 minutes, the effect of formycin A metabolites on leishmanial protein synthesis was investigated in in vitro protein synthesis experiments. Messenger RNA from formycin B-treated promastigotes was translated only 40% as efficiently as control promastigote mRNA by rabbit reticulocyte lysates. In addition, when formycin A-5'-triphosphate was preincubated with the rabbit reticulocyte lysates, translation of control mRNA was 86% inhibited. Formycin B toxicity to Leishmania promastigotes appears to be at least partially due to inhibition of protein synthesis by formycin A nucleotides and formycin A containing mRNA.

Adenine↗