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At least 343 records · Page 19Linked to original sources
PubMed1992

DNA binding activity and inhibition of DNA-protein interactions. Differential effects of tetra-p-amidino-phenoxyneopentane and its 2'-bromo derivative.

In the present study are reported the differential DNA binding activity of the anti-tumor polyamidine tetra-p-amidinophenoxyneopentane (TAPP-H) and its 2'-halo derivative (TAPP-Br), and their effects on the binding of the recombinant Epstein-Barr virus (EBV) nuclear antigen to a synthetic oligonucleotide mimicking the target DNA sequence present in the EBV genome. In addition, the proliferation kinetics and cell cycle analysis of human leukemia K562 cells treated with TAPP-H and TAPP-Br are reported. The possible in vivo relationship between DNA binding affinity and cytotoxicity is also discussed.

Antigens, Viral↗
PubMed1992

Inhibition of enzymes of polyamine back-conversion by pentamidine and berenil.

Pentamidine and berenil, clinical antiparasitic amidines, have been found to be potent competitive inhibitors of human spermidine/spermine acetyltransferase (SSAT). Ki values were found to be 2.4 and 2 microM, respectively, with spermidine as substrate. A second enzyme of polyamine back-conversion, murine polyamine oxidase (PAO), was found to be competitively inhibited by pentamidine, with a Ki of 7.6 microM when N-acetylspermine was the substrate. Berenil, on the other hand, was an extremely weak inhibitor (Ki = 120 microM). The implication of the effect of inhibition of polyamine back-conversion on the growth of mammalian parasites is discussed.

Acetyltransferases↗
PubMed1993

Aromatic diamidines are reversible inhibitors of porcine kidney diamine oxidase.

The inhibitory ability of aromatic diamidines has been studied on porcine kidney diamine oxidase. The reversibility of drug-protein interactions has been tested by means of exhaustive dialysis experiments, showing in all cases a reversible binding pattern. Ki values obtained by means of Lineweaver-Burk plots were: stilbamidine 12 microM, 2-OH-stilbamide 8.5 microM, phenamidine 4 microM, propamidine 8 microM, dibromopropamidine 4.9 microM and amicarbalide 12 microM.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Putrescine uptake inhibition by aromatic diamidines in Leishmania infantum promastigotes.

The effect of a series of aromatic diamidines has been tested on Leishmania infantum promastigotes in both culture growth and putrescine uptake. The EC50 values calculated by means of dose-response curves were 45, 80, 165, 259 and 600 microM for 4', 6-diamidino-2-phenylindole (DAPI), dibromo propamidine, pentamidine 2-hydroxy stilbamidine and stilbamidine, respectively, although no inhibitory effects on cell growth were found at 1 mM propamidine, phenamidine and amicarbalide. When these compounds were kinetically analysed for putrescine uptake using Lineweaver-Burk plots, the Ki values reached were: DAPI, 15 microM; pentamidine, 3 microM; dibromo propamidine, 7 microM; 2-hydroxy stilbamidine, 21 microM; stilbamidine, 20 microM; propamidine, 25 microM; and phenamidine, 95 microM. Amicarbalide, however, was not able to reduce putrescine uptake to a significant extent, even at the highest concentration studied of 1 mM.

Amidines↗
PubMed1984

Lymphocyte function in experimental African trypanosomiasis. VII. Loss of antigen-nonspecific suppressor-T-cell activity.

The extent of immunosuppression occurring in mice infected with the pathogenic African trypanosomes was studied. Spleen cells from Trypanosoma rhodesiense-infected C57BL/6J mice were tested for antigen-nonspecific suppressor-T-cell (Ts) activity after concanavalin A (Con A) treatment in vitro. After exposure to Con A, control and infected mouse spleen cells were added to responder spleen cell cultures stimulated with sheep erythrocytes (SRBC). Assays for the resultant plaque-forming cell responses to SRBC revealed that antigen-nonspecific Ts activity was lost during the first week of infection. Changes in infected mouse T-cell subpopulations, including a terminal loss of Lyt 2.2+ cells, accompanied but did not precede the demonstrable loss of Ts function. Splenic suppressor macrophages which arise during infections with T. rhodesiense also did not seem to be associated with the loss of antigen-nonspecific Ts activity. It is concluded that the generalized immunosuppression associated with experimental African trypanosomiasis extends to the mitogen-induced Ts population.

Animals↗
PubMed1985

Trypanosoma brucei: five commonly used trypanocides assayed in vitro with a mammalian feeder layer system for cultivation of bloodstream forms.

The in vitro activity of five commonly used trypanocides on bloodstream forms of Trypanosoma brucei brucei TC 221 was examined in 24-well culture plates in the presence of bovine fibroblast feeder layer cells. The minimum effective concentrations determined were as follows: Berenil 1.0 microgram/ml; Samorin 10.0 micrograms/ml; Antrycide dimethylsulfate 0.1 microgram/ml; Arsobal 0.01 microgram/ml; Naganol 1.0 microgram/ml. Contrary to values obtained with other in vitro assays, minimum effective concentrations obtained here were within the range of drug levels reached in blood, plasma, or serum of humans and animals after treatment with curative doses. The trypanocidal activity of Naganol in this assay was of particular interest, since Naganol has been hitherto considered to be inactive in vitro.

Animals↗
PubMed1987

Trypanosoma congolense: host responses following tsetse transmitted infection of Kilifi isolates in goats.

East African x Galla goats, when infected with Trypanosoma congolense isolates from the Kilifi area of Kenya by Glossina morsitans centralis, did not develop the characteristic chancre reaction at the bite sites, whereas bites of tsetse infected with the cloned T. congolense IL.1180 from Serengeti, Tanzania, resulted in chancres in the same goats. Histological changes could not be observed in skin biopsies collected 8 or 9 days after infection with Kilifi isolates. However, all goats became parasitemic about 10 days after challenge. It is concluded that the absence of chancre development is a characteristic feature of T. congolense parasites from Kilifi. The isoenzyme analysis of clones of two T. congolense Kilifi isolates and the T. congolense clone IL.1180 indicated that they belong to different zymodemes. Neutralizing antibodies to homologous metacyclic variable antigen types were detected in six out of seven (86%) of the sera from goats infected with a clone or stock of a T. congolense Kilifi isolate, 20 days after infection. Goats primed by tsetse transmitted infection with a stock or clone of T. congolense from Kilifi and treated with Berenil were, in three out of eight cases (37%), not immune to homologous challenge. It is suggested that the reduced immune response to metacyclic variable antigen types could be a result of the absence of cellular infiltration, i.e., chancre development in the skin at the tsetse bite site. It is concluded that the use of the chancre reaction as a marker for serodeme analysis of recently isolated stocks of T. congolense from Kilifi was not feasible.

Animals↗
PubMed1988

Ascaris suum and Onchocerca volvulus: S-adenosylmethionine decarboxylase.

Putrescine-dependent S-adenosylmethionine decarboxylase (EC 4.1.1.50) was demonstrated in Ascaris suum and Onchocerca volvulus; activation was found to be about fourfold by putrescine. Mg2+ did not affect the enzyme activity. A. suum was taken as a model nematode and its S-adenosylmethionine decarboxylase was partially purified and characterized. The molecular weight was estimated to be 220,000. The apparent Km-value for adenosylmethionine was determined to be 17 microM. Methylglyoxal bis(guanylhydrazone) and berenil competitively inhibited the enzyme activity; the apparent Ki-values were found to be 0.24 microM and 0.11 microM, respectively. The dependence of filarial worms on uptake and interconversion of putrescine and polyamines as well as properties of the S-adenosylmethionine decarboxylase, different from the host enzyme, points to the polyamine metabolisms as a useful target for chemotherapy.

Adenosylmethionine Decarboxylase↗
PubMed1992

Minor-groove width and accessibility in B-DNA drug and protein complexes.

A new definition is presented for minor-groove width in double-helical B-DNA structures. This uses interstrand H4' ... H5' rather than P ... P distances. It is shown by examination of various oligonucleotide crystal structures that these H4' ... H5' distances are a sensitive measure of minor-groove drug and protein binding, since these hydrogen atoms are in direct non-bonded contact with such bound ligands.

Base Composition↗
PubMed1994

Berenil acts as a poison of eukaryotic topoisomerase II.

The ability of the anti-trypanosomal drug berenil to interfere with the activities of eukaryotic type II topoisomerases is evaluated using two different types of reactions catalyzed by the enzyme: the relaxation of naturally supercoiled DNA and the decatenation of kinetoplast DNA (kDNA). The results indicate that berenil acts as an inhibitor of the catalytic activity, but the inhibiting ability appears to be smaller than for other minor-groove binding ligands.

Animals↗
PubMed1991

Leishmania infantum: polyamine biosynthesis and levels during the growth of promastigotes.

1. Decarboxylation of polyamine precursors: L-ornithine and L-methionine was determined along the growth curve of Leishmania infantum promastigotes in vivo, reaching maximum values on day 2 post-inoculum (mid-logarithmic phase). 2. Maximum values of L-ornithine and L-methionine decarboxylation were: 1.97 +/- 0.28 nmol CO2/hr/10(7) promastigotes and 3.18 +/- 0.34 nmol CO2/hr/10(7) promastigotes, respectively. 3. Total (free + conjugated) polyamine content was closely related with the proliferative stage of Leishmania infantum promastigotes. 4. D,L-alpha-difluoromethylornithine (DFMO) and Berenil depleted putrescine levels in a concentration-dependent manner. 5. Total and free putrescine/spermidine ratio varied significantly with the proliferative stage. Minimum values were found in late logarithmic phase (day 3 post-inoculum). 6. Small but detectable amounts of free spermine were detectable along the growth curve of Leishmania infantum promastigotes.

Animals↗
PubMed1993

In vivo effect of berenil on rat liver polyamine metabolism.

1. Berenil, administered to rats in vivo, promoted a decrease in liver SAMDC activity, but an increase in ODC and SAT activity. 2. Its effect on ODC was completely prevented by cycloheximide, that on SAT only partially. 3. Berenil had no effect on ODC activity in adrenalectomized rats. Adrenergic antagonists counteracted the effect of Berenil on ODC activity. 4. Polyamine content was increased. The maximum modification was observed for putrescine and N1-acetylspermidine.

Acetyltransferases↗
PubMed1993

Effect of Berenil on polyamine metabolism in primary cultured rat hepatocytes.

1. Putrescine and spermidine content increased in hepatocytes during culture. In the presence of 10 microM Berenil, putrescine content was further increased, while the increase of spermidine was prevented. 2. Ornithine decarboxylase activity was markedly reduced, and to a lesser extent also S-adenosylmethionine decarboxylase activity. 3. Berenil appears to promote an increase in the transformation of spermidine into putrescine, and to inhibit the polyamine efflux.

Adenosylmethionine Decarboxylase↗