Biomedical subjects

J J Marr

Publications and source records attributed to J J Marr.

At least 37 records · Page 2Linked to original sources

PubMed1988

A tissue culture system for the growth of several species of Leishmania: growth kinetics and drug sensitivities.

We have developed a simple in vitro method of infecting a continuous human macrophage cell line (U937) with promastigotes of several species of Leishmania. These include L. braziliensis braziliensis, L. b. panamensis, L. donovani, L. mexicana mexicana, L. m. pifanoi, L. tropica, and L. major. The growth kinetics of these species are presented as well as drug sensitivity data. The U937 cell system can be used to determine drug efficacy and eliminates the need to use amastigotes from animal tissues to infect the tissue culture.

Allopurinol↗

PubMed1988

The synergistic action of pyrazolopyrimidines and pentavalent antimony against Leishmania donovani and L. braziliensis.

Pyrazolopyrimidines, particularly allopurinol, allopurinol riboside, and other purine analogues, show promise as experimental therapeutic compounds for the treatment of leishmaniasis. The combination of these agents with pentostam may produce an improved therapeutic effect. We report here on strong synergistic activity between pyrazolopyrimidines and pentavalent antimonials in a human macrophage tissue culture system infected with Leishmania donovani and L. braziliensis.

Allopurinol↗

PubMed1988

A new method for cloning Giardia lamblia, with a discussion of the statistical considerations of limiting dilution.

This report describes a method of cloning Giardia lamblia by limiting dilution which is simpler than the previously described semisolid agar technique and which may also be applied as an assay of cell viability. A discussion of the basic statistics of limiting dilution, which is applicable to any cell type, and a method of statistically comparing colony-forming efficiencies from different cell populations are included. The colony-forming efficiency (CFE) of this method, when applied to late log-phase cultures, is 72.1 +/- 10.05%. When only cells adherent to the sides of culture vials are cloned, the CFE is 87.1 +/- 9.85%.

Animals↗

PubMed1987

Pneumocystis carinii pneumonia therapy with 9-deazainosine in rats.

An inosine analog, 9-deazainosine, has previously been demonstrated to inhibit Pneumocystis carinii in culture with WI-38 cells. The present study shows that it is also effective against Pneumocystis carinii in immunosuppressed Sprague-Dawley rats with Pneumocystis carinii pneumonia. After 8 wk of immunosuppression, rats that developed severe Pneumocystis carinii pneumonia were treated with either 9-deazainosine or served as controls. After 15 days of therapy, animals were sacrificed and severity of infection determined by morphologic examination of lungs for numbers of Pneumocystis carinii. Treated animals had greatly reduced numbers of Pneumocystis carinii trophozoites and cysts, compared with controls. This drug shows promise for therapy of Pneumocystis carinii pneumonia and should be studied further.

Animals↗

PubMed1987

Synergism between 9-deazainosine and DL-alpha-difluoromethylornithine in treatment of experimental African trypanosomiasis.

Kinetoplastid hemoflagellates are sensitive to growth inhibition by various purine analogs. In this study the activities of 9-deazainosine (9-DINO), formycin B, and sinefungin were compared in experimental murine Trypanosoma brucei subsp. brucei infections, both singly and in combination with the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine (DFMO, eflornithine). Used singly, all of the purine analogs were able to suppress an acute T. brucei subsp. brucei infection. 9-DINO and formycin B were the most active. None of the purine analogs was curative when used singly against a strain causing chronic central nervous system infection. 9-DINO was highly effective when used in combination with DFMO in curing this central nervous system infection and another more stringent experimental infection. Neither sinefungin nor formycin B was active in combination with DFMO in curing the central nervous system experimental infection. 9-DINO was metabolized to phosphorylated derivatives of 9-deazaadenosine and 9-deazaguanosine by bloodstream trypomastigotes, but not by murine erythrocyte suspensions or kidney or liver homogenates--a potential rationale for the selectivity of the analog. These studies indicate that 9-DINO is a potent, nontoxic purine analog which, in combination with DFMO, is capable of late-stage cures of African trypanosomiasis.

Animals↗

PubMed1986

Adenosine analog metabolism in Giardia lamblia. Implications for chemotherapy.

Certain adenosine analogs can inhibit the growth of Giardia lamblia. This biological action correlates with the ability of the organism to phosphorylate the nucleoside directly to the nucleotide. Four of these, 8-azaadenosine, 1-deazaadenosine, 7-deazaadenosine, and 9-deazaadenosine, were very effective. The respective bases of the first three were ineffective. The base of 9-deazaadenosine was not tested as this C-nucleoside is non-cleavable. Metabolic studies using radioactive 7- and 9-deazaadenosine showed that these compounds were phosphorylated by the organism. Enzymatic assay confirmed the presence of nucleoside phosphotransferase activity; no nucleoside kinase activity was found. Preliminary characterization of this phosphotransferase suggests that it has different substrate and phosphate donor specificities than the mammalian enzyme and, therefore, may be a potential site for chemotherapeutic attack.

Adenine↗

PubMed1986

Mechanisms of action of pyrazolopyrimidines in Leishmania donovani.

We investigated the antileishmanial actions of the pyrazolopyrimidines allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine), thiopurinol (4-thiopyrazolo[3,4-d]pyrimidine), and aminopurinol (4-aminopyrazolo[3,4-d]pyrimidine). These compounds affect several metabolic processes. The first is the inhibition of GMP reductase by the IMP analogues allopurinol ribonucleoside monophosphate and thipurinol ribonucleoside monophosphate which reduces the organism's ability to synthesize ATP from guanine. Second, interconversion of adenine nucleotides to guanine nucleotides, is curtailed by the inhibition of IMP dehydrogenase by these same IMP analogues. Third, the IMP analogues reduce intracellular UTP content. The fourth affect is increased catabolism of RNA and consequent reduction of protein synthesis. This latter effect is due to the adenine nucleotide analogues aminopurinol ribonucleoside mono-, di-, and/or triphosphates, metabolic products of both allopurinol and aminopurinol.

Adenine↗

PubMed1986

Growth of Leishmania donovani amastigotes in the continuous human macrophage cell line U937: studies of drug efficacy and metabolism.

We have developed a simple and reproducible system for infecting a human macrophage cell line (U937) with stationary-phase Leishmania donovani promastigotes. Four days after infection, greater than 90% of the promastigotes had transformed to amastigotes. The antileishmanial agents allopurinol riboside, formycin B, 9-deazainosine, and sodium stibogluconate effectively inhibited the growth of L. donovani amastigotes in this cell line. To study the capability of amastigotes in the U937 cell line to carry out biochemical reactions that could be monitored experimentally, we incubated the cells with radiolabeled 9-deazainosine. This purine analogue underwent metabolism in the amastigote phase similar to that occurring in the promastigote phase. This cell line should be useful for studies of parasite maturation and differentiation, parasite-human interactions, and antiparasitic drugs.

Allopurinol↗

PubMed1986

Activity of inosine analogs against Pneumocystis carinii in culture.

Three analogs of inosine, formycin B, allopurinol ribonucleoside, and 9-deazainosine, were tested for their ability to suppress proliferation of Pneumocystis carinii in culture with WI-38 cells. The organism was inhibited by 9-deazainosine at 10 micrograms/ml, and there was some inhibition at 1 microgram/ml. Formycin B was effective only at 40 micrograms/ml. Allopurinol ribonucleoside had little effect.

Allopurinol↗

PubMed1985

Inosine analogs. Their metabolism in mouse L cells and in Leishmania donovani.

The growth of Leishmania donovani promastigotes and mouse L cells is differentially inhibited by several inosine analogs with modifications in the imidazole ring. The protozoal and mammalian cells also demonstrate differential metabolism of these analogs. 7-Deazainosine, 7-thia-7,9-dideazainosine, and formycin B were converted to their respective ATP analogs by both cell types. 8-Azainosine was converted to a GTP analog by mouse L cells; L. donovani did not metabolize this nucleoside. 9-Deazainosine and allopurinol riboside were metabolized only to their respective IMP analogs by L cells. L. donovani metabolized 9-deazainosine and allopurinol riboside to their ATP analogs and also metabolized 9-deazainosine to its GTP analog. All nucleosides studied were resistant to cleavage by either organism. From metabolism studies in the presence of a specific enzyme inhibitor, it was deduced that allopurinol riboside, formycin B, and 9-deazainosine were phosphorylated by at least two different routes in the mouse L cells. The metabolism of formycin B was inhibited 65% by the adenosine kinase inhibitor, 5-iodotubercidin, whereas the metabolism of allopurinol riboside (14% inhibition) and 9-deazainosine (0% inhibition) was only slightly affected by this inhibitor. The metabolism of allopurinol riboside and 9-deazainosine by L. donovani was not affected by 5-iodotubercidin. In contrast to the results of L cells, the metabolism of formycin B by L. donovani was also not affected by 5-iodotubercidin. The abilities of mouse L cells and L. donovani to metabolize these inosine analogs to the corresponding nucleotide analogs of ATP or GTP may be considered to be an activating step and correlates well with the respective cytotoxic effects of these compounds.

Adenosine Kinase↗

PubMed1985

Anaerobic myocardial abscess following myocardial infarction.

An anaerobic myocardial abscess due to Bacteroides fragilis developed in a 60-year-old man when he had an acute myocardial infarction while recuperating from surgery for a paracolonic abscess. Anaerobic bacteremia is a common event and may lead to infection in areas of low oxygen tension far removed from the original portal of entry.

Abscess↗

PubMed1985

Inosine analogs as chemotherapeutic agents for African trypanosomes: metabolism in trypanosomes and efficacy in tissue culture.

Certain purine analogs, the pyrazolopyrimidines, are effective chemotherapeutic agents against Leishmania spp. and Trypanosoma cruzi both in vitro and in some clinical models. Heretofore they have not been effective against the African trypanosomes; this suggested that these organisms were not comparable to the other pathogens with respect to their purine metabolism. We have studied the efficacy and metabolism of the pyrazolopyrimidine bases allopurinol and thiopurinol, their respective ribonucleosides, and the C-nucleosides formycin B and 9-deazainosine in Trypanosoma brucei subsp. gambiense and Trypanosoma brucei subsp. rhodesiense. The efficacy of these compounds was dependent on the purine content of the culture medium. The C-nucleosides were the most effective, with 90% effective doses for formycin B and 9-deazainosine of 0.01 and 2 micrograms/ml, respectively. Metabolism was the same in both the bloodstream and culture forms and identical to that reported for Leishmania spp. and T. cruzi. Both agents were phosphorylated to the ribonucleotide and then aminated to produce adenine nucleotide analogs. Growth inhibition studies were performed with three inosine analogs (allopurinol riboside, formycin B, and 9-deazainosine) on trypomastigotes grown in bone marrow tissue culture. Both C-nucleosides eradicated the infection at a concentration of 0.25 micrograms/ml. Unlike formycin B, 9-deazainosine is not known to be aminated by mammalian cells and appears to be relatively nontoxic in three different mammalian tissue culture systems. This nucleoside was very active against all pathogenic leishmaniae and trypanosomes investigated and is worthy of further study.

Animals↗

PubMed1984

Monophosphates of formycin B and allopurinol riboside. Interactions with leishmanial and mammalian succino-AMP synthetase and GMP reductase.

Formycin B 5'-monophosphate (Form B-MP) and allopurinol riboside 5'-monophosphate ( HPPR -MP) are isomers of IMP that are metabolically produced when Leishmania spp. are incubated with the antileishmanial agents formycin B and allopurinol or allopurinol riboside. The interactions of Form B-MP with succino -AMP synthetase and GMP reductase from both leishmanial and mammalian sources were compared with the data of earlier studies with HPPR -MP. Both analogs could substitute for IMP as a substrate for succino -AMP synthetase isolated from Leishmania donovani. The V'max values of Form B-MP and HPPR -MP were about 1% of the V'max of IMP. Only Form B-MP (and not HPPR -MP) could serve as an alternative substrate for mammalian succino -AMP synthetase. The V'max of Form B-MP was 40% that of IMP. The corresponding analogs of AMP, ADP and ATP were produced when Formycin B was incubated with mouse L cells. The Formycin A residue was incorporated into the cellular RNA. The amount of Formycin A-TP produced (relative to ATP) in mouse L cells was considerably less than that produced in Leishmania spp. Both Form B-MP and HPPR -MP were inhibitors of partially purified GMP reductase from L. donovani. The binding of Form B-MP and HPPR -MP to human GMP reductase was 40- and 100-fold weaker, respectively, than the binding to leishmanial GMP reductase. Pretreatment of promastigotes of L. donovani with either allopurinol or Formycin B resulted in greater than 95% reduction of the incorporation of the radiolabel from [14C]xanthine into ATP and greater than 80% reduction of the incorporation of the label into GTP. The HPPR -MP and Form B-MP present in these cells may have inhibited the leishmanial succino -AMP synthetase and GMP reductase. The analogs had little or no effect on the pool sizes of ATP and GTP of either mouse L cells or L. donovani.

Adenylosuccinate Synthase↗

PubMed1984

Nucleoside hydrolases from Trypanosoma cruzi.

Four distinct nucleoside cleaving enzymes were detected in extracts of Trypanosoma cruzi epimastigotes. Two of these were nucleoside phosphorylases: one was specific for pyrimidines and the other for purines. The other two enzymes were nucleoside hydrolases. These hydrolytic enzymes were partially purified and their substrate and inhibitor specificities were studied. One of the hydrolases was designated inosine/guanosine hydrolase. It required purine substrates containing a 9-beta-D-ribofuranosyl substituent. Neither 2'-deoxyinosine, 2'-deoxyguanosine, nor hypoxanthine arabinoside served as substrates. The kinetic patterns obtained from combined product analysis and the mutual competitive inhibition of this enzyme by inosine and guanosine suggested that these substrates were cleaved at a common catalytic site. Inhibitor studies with several deoxyinosines have demonstrated the importance of the 2'-, 3'-, and 5'-hydroxyl groups for efficient binding to the enzyme. Adenosine, which did not serve as a substrate, was a potent competitive inhibitor (Ki = 8 microM) with respect to both inosine and guanosine. This enzyme had a particle weight of 106,000 +/- 10,000 as determined by Sephadex chromatography. The other hydrolase was specific for 2'-deoxyinosine. It only accepted purine substrates with a 6-oxo- and a 9-beta-D-2'-deoxyribofuranosyl substituent. Inosine, hypoxanthine arabinoside and a variety of deoxyinosines were not substrates nor did they strongly inhibit this enzyme. This enzyme had a particle weight of 19,000 +/- 2,000 as determined by Sephadex chromatography.

Animals↗

PubMed1984

Pyrazolopyrimidine metabolism in Leishmania: an overview.

The demonstration of this unusual metabolic sequence in these organisms indicates that there are substantial differences between these protozoans and their mammalian hosts with respect to pyrazolopyrimidine metabolism. The intracellular forms of L. donovani, which are the pathogenic agents of the human disease, metabolize allopurinol identically. Trypanosoma cruzi, the causative agent of American trypanosomiasis, metabolizes allopurinol in the same manner as leishmania; in addition, the intracellular and bloodstream forms of this organism, the agents of the disease in man, carry out the same reaction sequence. The African trypanosomes, T. rhodesiense and T. brucei also convert allopurinol to the same metabolic products. These metabolic sequences appear to be common to most of the pathogenic hemoflagellate parasites that infect man and this opens a new avenue of research in purine metabolism.

Allopurinol↗

PubMed1984

Efficacy of pyrazolopyrimidine ribonucleosides against Trypanosoma cruzi: studies in vitro and in vivo with sensitive and resistant strains.

Strains of Trypanosoma cruzi differ in their susceptibilities to and metabolism of pyrazolopyrimidines. Allopurinol riboside can control but not eliminate infections with a sensitive strain in both tissue culture and mice. Formycin B, which proved to be greater than 10-fold more effective on a weight basis, showed a similar strain specificity but could eliminate an infection with a sensitive strain from tissue culture. However, this drug, unlike allopurinol riboside, was converted to toxic analogues of adenosine mono-, di-, and triphosphate by uninfected tissue culture cells. Thiopurinol and its riboside were effective against all strains unless culture was performed in purine-defined medium. Thus formycin B and allopurinol riboside appear to be good models for the design of antitrypanosomal agents. Suitable modification of the molecule may provide an effective chemotherapeutic agent.

Adenine↗

PubMed1984

Biological action of inosine analogs in Leishmania and Trypanosoma spp.

Previous investigations have suggested that inosine analogs would be good models for the development of chemotherapeutic agents active against pathogenic hemoflagellates. We have systematically modified the five-membered heterocyclic ring of six inosine analogs and tested them for their antiprotozoal activities and toxicity to a mammalian cell line. All six analogs were very active against the three protozoan pathogens Leishmania donovani, Trypanosoma cruzi, and Trypanosoma gambiense. Two of the six, 9-deazainosine and allopurinol ribonucleoside, had very little toxicity for mouse L cells and offer promise as potential chemotherapeutic agents.

Animals↗

PubMed1983

Pyrazolopyrimidine metabolism in Leishmania and trypanosomes: significant differences between host and parasite.

The pathogenic hemoflagellates of the genera Leishmania and Trypanosoma are major causes of human disease in the tropical and subtropical areas of the world. In general, the agents used to treat diseases caused by these organisms are toxic and not suitable for administration to the millions of people infected. Investigations over the past several years have shown that there are several major differences between man and these protozoans with respect to purine metabolism. The differences appear to offer promise for the development of effective chemotherapeutic compounds. These organisms do not synthesize purines de novo, as does man. They are able to concentrate pyrazolopyrimidines with the cell and metabolize them as purines through the salvage pathways, ultimately incorporating them into nucleic acids. This does not occur in mammals. The pyrazolopyrimidine base allopurinol, which has served as a prototype, is activated by a phosphoribosyltransferase to the ribonucleotide. The ribonucleotide is aminated to the 4-amino-pyrazolopyrimidine ribonucleotide and subsequently phosphorylated to the triphosphate form and incorporated into RNA. The pyrazolopyrimidine ribonucleosides formycin B and allopurinol ribonucleoside are activated through a nucleoside phosphotransferase. The resulting ribonucleotide is aminated and incorporated into RNA as described above. These metabolic peculiarities occur not only in the forms of these parasites which are found in the insect vectors but also in the intracellular forms which are pathogenic in man. The differences in the enzymology and metabolism of purines which exist in the genera Leishmania and Trypanosoma offer excellent opportunities for chemotherapeutic exploitation.

Adenine↗