P-078 The role of male factor accompanying PGT-A as possible complementary strategies to control miscarriage

Study question

Considering maternal influence or management of male factor, should only PGT-A be indicated to reduce miscarriage?

Summary answer

The finest cost-effective treatment for each patient to improve ART success, is a good, tailored, and individualized indication for choosing the best IVF technique.

What is known already

Advanced maternal age is related with fertility decline, oocyte quality and the increased risk of aneuploid embryos. Aneuploid embryos lead to a reduced implantation potential and higher miscarriage rate. PGT-A is a screening method to determine the chromosomal status of the embryos and it’s the most expanded technique used to reduce the miscarriage rates in most clinics.

Common sperm capacitation techniques used in IVF laboratories could cause sperm DNA damage, leading to a smaller number of blastocysts obtained per cycle and a higher miscarriage rate. Microfluidics devices or sperm selection centrifugation-free (Swim-up modified techniques) could reduce sperm DNA fragmentation.

Study design, size, duration

This is a retrospective study from 2018-2020 including patients using their own oocytes fertilized by ICSI. No major differences on male factor were found between male patients. In all cycles at least one good quality blastocyst was obtained to biopsy on blastocyst stage in cycles with PGT-A or to transfer without PGT-A. Live-Birth Rate (LBR) per cycle is compared and analyzed by the t-Student and X2 test between groups.

Participants/materials, setting, methods

A total of 308 cycles were included in this study. Three groups of patients were formed: Group 1: 76 cycles with PGT-A; Group 2: 191 cycles without PGT-A and sperm samples processed by Swim-Up technique; and Group 3: 41 cycles without PGT-A and a centrifugation free sperm selection (IO-Lix) used for ICSI. The main indication for PGT-A was maternal age. No differences between male or other female infertility factors were found between groups.

Main results and the role of chance

When we compare the 3 groups, no statistically significant differences were obtained in fertilization rate (79.8%; 73.5%; 72.6%; p = 0.28); development to the blastocyst stage (48.7%; 43.1%; 44.9%; p = 0.11) and pregnancy rate per transfer (48.8%; 45.6%; 52.8%; p = 0.55).

It seems that PGT-A doesn’t affect the viability, or the implantation potential of the biopsied embryos and a special sperm capacitation technique is useful for daily clinical use.

If we include only patients with ages >38 years old to avoid age differences, comparing Group 1 (PGT-A) and Group 3 (no-PGT-A and IO-lix) (LBR=19.7% vs 50%), we obtain statistically significant differences between both groups (p = 0.01). No differences were found between Group 2 (LBR=26.4%; p = 0.25) and the Group 1.

To summarize, the female age appears to be the most important factor for IVF success and the PGT-A can help to avoid a miscarriage, however when we compare women with advanced maternal age, the LBR is increased when PGT-A is non performed, and the sperm DNA is not damaged by the capacitation technique. Why not PGT-A to be complemented with efficient sperm selection?

Limitations, reasons for caution

Although sperm selection techniques to decrease sperm DNA damage could reduce miscarriage rates, PGT-A is the only used technique that allows us to ensure that euploid embryos are transferred.

Wider implications of the findings

A better understanding of male factor in IVF treatments can reduce miscarriage. Male factor assessment is a cost-effective technique to improve LBR in those patients without a clear indication for PGT-A, (advanced maternal age). Patient must be studied individually, and PGT-A shouldn’t be used indiscriminately to ensure a healthy new-born.

Trial registration number

Not Applicable

Molecular characterisation of KIR2DS2*005, a fusion gene associated with a shortened KIR haplotype

KIR2DS2 is an activating homologue of KIR2DL2, an inhibitory killer-cell immunoglobulin-like receptor (KIR) that surveys expression of major histocompatibility complex-C allotypes bearing a C1 epitope. We have studied here its allele KIR2DS2*005, which shows a hybrid structure-it is identical to other KIR2DS2 alleles in the ectodomain, but has transmembrane and cytoplasmic regions identical to those of KIR2DS3(*)001, a short-tailed KIR of uncertain expression and function. Our results reveal that KIR2DS2*005 is a fusion gene-the product of an unequal crossing over by which the genes KIR2DS2 and KIR2DS3 recombined within a 400 base pair region of complete identity in intron 6. Also resulting from that recombination was a shortened KIR haplotype of the B group, in which three genes commonly linked to KIR2DS2 (KIR2DL2, KIR2DL5B and KIR2DS3) are deleted. Population studies indicate that KIR2DS2*005 is still associated to such haplotype, and it can be found in approximately 1.2% of Caucasoids. Using a combination of two monoclonal antibodies, we also demonstrate that KIR2DS2*005 encodes a molecule expressed on the surface of natural killer- and T-lymphocytes.

The 5' intergenic, promoter, pseudoexon 3 and complete coding sequences of the hybrid gene KIR2DS3*002

Genomic and mRNA sequences support the KIR2DS3*002 gene being a hybrid of KIR2DS3*00103 and KIR2DS5.

Cytotoxic effects of two antimolting insecticides in mammalian CHO-K1 cells

Cytotoxicity of two insect growth regulators, diflubenzuron, a benzoylphenylurea derivative that inhibits the synthesis of new chitin in target organisms, and pyriproxyfen, an insect juvenile hormone analogue, were tested on CHO-K1 cultures, using the neutral red incorporation assay. Both compounds displayed cytotoxic effects that rise with time exposure. The presence of either fetal calf serum or bovine serum albumin diminished significantly the cytotoxicity of both compounds, thus pointing to a strong protein binding. In addition, extensive metabolization with rat liver submitochondrial fraction gave rise to metabolites less toxic than the parent compounds, implying the relative safety of both diflubenzuron and pyriproxyfen in mammals.

Changes in glutathione-redox balance induced by hexachlorocyclohexane and lindane in CHO-K1 cells

1. The basal cytotoxic effect of the organochlorine pesticides hexachlorocyclohexane and lindane on CHO-K1 cultures was assessed at fractions of their lethal doses as determined by the neutral red incorporation (NRI) assay (NRI(6.25), NRI(12.5) and NRI(25)). The sulphur-redox cycle enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase, and total and oxidized glutathione were evaluated at several points during the standard growth curve of the cultures. 2. After incubation with each compound for 24 h, both glutathione peroxidase and reductase showed a substantial increase at the lowest exposure doses (NRI(6.25))--more significantly for lindane than for 1,2,3,4,5,6-hexachlorocyclohexane (HCH)--and dropped at higher doses of both compounds. The reduced and oxidized glutathione content was greatly diminished at the lower exposures, whereas the total glutathione content was higher at NRI(12.5) values. 3. Changes in cell membrane integrity were assessed for a wide range of pesticide concentrations with the lactate dehydrogenase release assay and lipid peroxidation. Membrane leakage and peroxide production were significantly enhanced at concentrations of HCH 50 microg ml(-1), although this effect was not significant at lindane concentrations < 200 microg ml(-1). 4. Lipid peroxidation increased with exposure to HCH at concentrations as low as NRI(6.25), whereas in the case of lindane, this increase was only significant at doses of NRI(25) and above.

Alterations of the glutathione-redox balance induced by metals in CHO-K1 cells

The effects of cadmium (Cd(2+)), mercury (Hg(2+)), lead (Pb(2+)), copper (Cu(2+)) and nickel (Ni(2+)) on the glutathione (GSH)-redox cycle were assessed in CHO-K1 by the neutral red uptake inhibition (NR) assay (NR(6.25), NR(12.5) and NR(25)). Mercury proved to be the most and lead the least toxic of the metals tested. The effects on GSH content and intracellular specific activities of enzymes involved in the GSH-redox balance were measured after a 24-h exposure. Total GSH content increased significantly in cultures exposed to the lowest metal concentration assayed (NR(6.25)), but fell to below control values when exposed to concentrations equivalent to NR(25). Oxidised glutathione content dropped significantly at NR(6.25), while somewhat higher values were obtained for cultures exposed to higher doses. Glutathione peroxidase (Gpx) activities were 1.2-, 1.5-, 1.6-, 2.0- and 2.5-fold higher than untreated controls for cadmium, copper, mercury, nickel and lead, respectively, at concentrations equivalent to NR(6.25). Gpx activity declined at metal concentrations equivalent to NR(12.5) and NR(25). Glutathione reductase activity remained almost unchanged except at low doses of mercury, nickel and lead. Glutathione-S-transferase activity decreased at rising metal concentrations. The results suggest that a homeostatic defence mechanism was activated when cells were exposed to doses equivalent to NR(6.25) while the ability of the cells to respond weakened as the dose increased. A close relationship was also observed between metal cytotoxicity, total GSH content and the dissociation energy of the sulphur-metal bonds. These facts confirm the involvement of antioxidant defence mechanisms in the toxic action of these ions.

Cyclodiene organochlorine insecticide-induced alterations in the sulfur-redox cycle in CHO-K1 cells

The effect of the cyclodiene organochlorine pesticides aldrin, dieldrin and endosulfan was assessed on CHO-K1 cultures at fractions of their lethal doses, determined by the neutral red (NRI) incorporation assay (NRI6.25, NRI12.5 and NRI25). Glutathione peroxidase, reductase and S-transferase, and total and oxidised glutathione were evaluated along the standard growth curve of the cultures. After a 24-h incubation with each insecticide, glutathione peroxidase incurred a large increase, while glutathione reductase and S-transferase activities were slightly higher than untreated controls. Unlike oxidised glutathione, the content of total glutathione declined significantly after exposure to cyclodiene insecticides. Changes in cell membrane integrity were assessed by the lactate dehydrogenase (LDH) release assay and lipid peroxidation for a wide range of pesticide concentrations. Membrane leakage and peroxide production were significantly enhanced at concentrations of aldrin and as low as 12.5 microg/ml, whereas dieldrin and endosulfan increased membrane fragility at much higher concentrations.

Alterations on polyamine content and glutathione metabolism induced by different concentrations of paraquat in CHO-K1 cells

The effect of herbicide paraquat has been assessed on CHO-K1 cultures at different concentrations. Glutathione peroxidase, reductase and S-transferase, as well as total and oxidized glutathione, were evaluated along the standard growth curve of the cultures. Paraquat was then administered during mid-log phase at concentrations that produced a calculated lethality of 6.25%, 12.5% and 25%, using the lysosomal dye assay, neutral red. After 24hr of incubation with paraquat, glutathione peroxidase suffered a large dose-response increase, unlike glutathione reductase and S-transferase, the activities of which were lower than untreated controls. The profile of total glutathione content was similar to that found for glutathione peroxidase, increasing with the administered doses of the herbicide. Polyamine content has been also studied at the same concentrations of paraquat, showing that intracellular spermidine and spermine pools were negatively affected with paraquat in a dose-response manner, unlike putrescine, which maintained elevated pools at the three concentrations assayed.

S-adenosylmethionine synthesis in Leishmania infantum promastigotes

Methionine adenosyltransferase (MAT), S -adenosylmethionine (AdoMet), and S -adenosylhomocysteine (AdoHcy), have been analysed at different time-points during the growth curve of Leishmania infantum. MAT activity and AdoMet content peaked in the lag and early log phases, whereas higher levels of AdoHcy were found in stationary phase cells. MAT activity of cell extracts displayed hyperbolic kinetics for both its substrates, l -methionine and ATP, with km values of 35 microm and 5 m m, respectively. MAT has an absolute requirement for divalent cations, and is dependent on sulfydryl protective agents. Unlike other sources, L. infantum MAT activity seems to be transcriptionally regulated, with an accumulation of MAT-mRNA during rapid growth periods of promastigotes.

Early alterations of polyamine metabolism induced after acute administration of clenbuterol in mouse heart

An acute treatment of mice with clenbuterol, a beta-adrenergic agonist, produced a marked increase of polyamines levels in heart, particularly during the early phase of administration of the drug. A single dose of 1.5 mg/kg caused as much as a 10 fold induction in activity of ornithine decarboxylase (ODC) and 3 to 4 fold increase in levels of putrescine, spermidine and spermine in mouse heart. Maximum changes were observed 3 to 4 hours post-administration of clenbuterol. This treatment did not produce any change in S-adenosylmethionine decarboxylase activity. The induction of cardiac ODC by clenbuterol was also dose dependent with a peak at about 5 micromol/kg. Co-administration of difluoromethylornithine, an irreversible inhibitor of ODC, or propranolol, a nonspecific beta-antagonist, with clenbuterol completely prevented the induction of ODC activity as well as the increase in polyamine levels in heart. However, pretreatment with alprenolol or metoprolol, the specific beta1 and beta2-antagonists, respectively, produced only partial prevention. The cardiac ODC from controls as well as clenbuterol treated mice exhibited similar affinity (Km) for its substrate, ornithine, while maximum enzyme activity (Vmax) was about 14 fold higher in clenbuterol treated mouse heart than in the control. Clenbuterol produced no change in the level of specific ODC mRNA or the protein, but the enzyme from the drug-treated mouse heart was considerably more stable than the control. Pretreatment of mice with either cycloheximide or actinomycin D followed by administration of clenbuterol could not prevent the induction in ODC activity suggesting that de novo biosynthesis of the enzyme protein or ODC mRNA was not responsible for induction of ODC activity. Post-translational changes in ODC may be responsible for an early increase of ODC activity due to clenbuterol treatment.

Plasma and muscle polyamine levels in aerobically exercised rats treated with salbutamol

The induction of hypertrophy of cardiac and skeletal muscles has been studied after treatment with two different salbutamol dosages, therapeutic and doping. Treatment of rats subjected to a physical training schedule with repeated doses (16 microg kg(-1) per day or 3 mg kg(-1) per day) of salbutamol, a specific beta-adrenergic agonist, induced a marked increase in both skeletal and heart-muscle weight, whereas total body weight did not change significantly. Adrenergic involvement of salbutamol-linked muscle hypertrophy was demonstrated by co-administration of the non-specific beta-adrenergic antagonist, propranolol (20 mg kg(-1) per day). Salbutamol-induced muscle hypertrophy was associated with an increase in serum, skeletal-muscle and heart levels of the naturally occurring polyamines putrescine, spermidine and spermine. These observations suggest the involvement of polyamines in muscle hypertrophy and the possible role of blood polyamines as exposure biomarkers in beta-adrenergic-muscle hypertrophy.

Pharmacokinetics of intravenous luxabendazole in rabbits: influence of the enterohepatic circulation

Luxabendazole (LBZ) is a new benzimidazole carbamate chemotherapeutic agent, which has proved to be very effective against adult and immature stages of the major gastrointestinal nematodes, trematodes and cestodes. While information on the efficacy of LBZ in several animal species is available, there seems to be no published information describing the disposition kinetics in any of them. As a part of the clinical development of luxabendazole, the pharmacokinetics of a single intravenous dose was investigated in parasite-free rabbits. Serial blood samples were collected at timed intervals for 12 h following administration of the dose, and concentrations in plasma were determined by a sensitive and specific HPLC method. Published data on LBZ point to the possible existence of an enterohepatic cycle (EHC), and so, it seemed appropriate to carry out two different forms of test. In the first, the possibility of intestinal reabsorption of LBZ excreted via the bile was allowed for (Treatment 1), while in the second it was interrupted by the oral administration of activated charcoal (Treatment 2). In both cases the animals were given a single dose of 10 mg kg-1 of LBZ intravenously (i.v). Comparison of the areas under the curve (AUCs) of LBZ concentrations in plasma samples taken from the animals receiving each treatment showed significant difference (p < 0.05). The given dose (10 mg kg-1) was converted in Treatment 1 to an effective dose of 13.9 mg kg-1 through recycling of LBZ. With Treatment 2 a bicompartmental distribution model for this drug was confirmed, together with high apparent distribution volumes: Vc = 1.87 L kg-1, and V beta = 7.09 L kg-1.

Interaction of cationic diamidines with Leishmania infantum DNA

The interaction of a series of potent leishmanicidal aromatic diamidines resembling pentamidine, was studied with Leishmania infantum DNA and polynucleotides. The diamidines viz., CGP040215A, CGP033829A and CGP039937A, interacted with leishmania DNA as well as with the polynucleotides poly(dA)-poly(dT), poly(dA-dT) and poly(dG-dC). The thermodynamic analysis to determine the association constants and the binding enthalpy pointed toward binding of the diamidines at AT regions of the DNA. The results also indicate that the diamidines bind at the outside of the DNA double helix, probably to the minor groove regions, with hydrogen bonds connecting the amide nitrogen of the diamidine to carbonyl oxygen atoms of thymidine or adenosine bases. However, CGP040215A and CGP033829A, the bisaryl diamidines, showed higher affinity than CGP039937A, the monoaryl diamidine. The spectrophotometric analysis of the interaction of these diamidines to test their effects on the melting temperature of leishmanial DNA suggests non-intercalating binding. The diamidines also showed potent inhibition of DNA polymerase activity of L. infantum extracts in vitro.

The pharmacology of leishmaniasis

The development of new strategies on chemotherapy of parasitic protozoan diseases is one of the most exciting research fields of recent years. World Health Organization (WHO) reports have recognized that the physiology and biochemistry of protozoan parasites and the host-parasite relation are the main targets for the design of new drugs that can be used in the future against these diseases.

Polyamine-mediated heart hypertrophy induced by clenbuterol in the mouse

The use of beta-agonists as growth-promoting agents in cattle could lead to toxic side-effects in man. One such effect is the accumulation of polyamines which seem to be implicated in muscle and heart hypertrophy. We have studied the induction of cardiac hypertrophy after treatment with clenbuterol and the role of polyamines in this effect. Treatment of mice with repeated doses of clenbuterol, a specific beta-adrenergic agonist, resulted in a marked increase in heart muscle weight whereas total body weight did not change significantly. Clenbuterol-linked cardiac hypertrophy could be prevented by co-administration of either the non-specific beta-adrenergic antagonist, propranolol, or the irreversible inhibitor of ornithine decarboxylase, alpha-difluoromethylornithine. The clenbuterol-induced cardiac hypertrophy was associated with a corresponding increase in the level of the polyamines putrescine, spermidine and spermine. These observations are indicative of the role of polyamines in cardiac hypertrophy induced by clenbuterol.

Pharmacokinetics of luxabendazole after oral and intravenous administration to sheep

OBJECTIVE

To determine pharmacokinetics of luxabendazole after oral and i.v. administration to healthy sheep.

ANIMALS

7 clinically normal female Merino sheep between 9 and 12 months old.

PROCEDURE

Pharmacokinetics were determined after oral and i.v. administration of luxabendazole at a dose of 10 mg/kg of body weight. Serial blood samples were collected for 56 hours after administration. Plasma concentrations of luxabendazole were determined by high-pressure liquid chromatography.

RESULTS

After i.v. administration, elimination of luxabendazole was slow, with a mean half-life of 8.72 hours. Mean steady-state volume of distribution and mean distribution volume during the elimination phase were 3.18 and 3.10 L/kg, respectively. Mean clearance was 0.24 L/kg.h, and mean area under the concentration-time curve was 41.89 mg.h/L. After oral administration, luxabendazole was slowly absorbed from the gastrointestinal tract. Mean absorption half-life was 2.26 hours. Peak plasma concentration was 0.50 microgram/ml and was detected 14 to 16 hours after drug administration. Mean area under the concentration-time curve was 12.03 mg.h/L. Mean bioavailability was 29%.

CONCLUSIONS

Results suggest that luxabendazole is moderately absorbed from the gastrointestinal tract in sheep, is widely distributed into extravascular compartments, and is cleared slowly.

CLINICAL RELEVANCE

Determination of pharmacokinetic parameters is the first step in determining a safe and efficacious dosage regimen for luxabendazole in sheep.

Structural determinants of putrescine uptake inhibition produced by cationic diamidines in the model of trypanosomatid Crithidia fasciculata

The effect of a heterologous series of cationic diamidines has been tested on cell growth and polyamine uptake on the model of insect Trypanosomatid Crithidia fasciculata. The maximum inhibitory effect on both parameters was found for pentamidine and dibromopropamidine, which exhibit a longer distance between amino and imino substituents. A minimum inhibitory effect was found with amicarbalide. A good relationship was obtained when the distance between amino moieties was plotted versus the inhibitory effect on putrescine uptake, suggesting a role of this structural property on polyamine transport in Crithidia fasciculata. In addition, a similar correlation was obtained for another Trypanosomatid parasite, Leishmania infantum.

Effects of cationic diamidines on polyamine content and uptake on Leishmania infantum in in vitro cultures

The effect of a series of cationic diamidines recently synthesized by Ciba Geigy, bearing diarylic (CGP040215A and CGP039937A) or monoarylic moieties (CGP033829A, CGP035537A and CGP036958A), was analyzed on some metabolic targets and cell proliferation of in vitro cultures of Leishmania infantum promastigotes (insect form). The action of these compounds on intracellular polyamine pools and putrescine transport suggests that diarylic structures were more effective than their monoarylic counterparts in depleting polyamine levels and inhibiting putrescine transport, although these processes correlate poorly with the antiproliferative rate of these compounds. Finally, the displacement of cationic diamidines to kDNA observed in the presence of several concentrations of spermidine suggests a possible combined mode of action of these molecules, first depleting intracellular polyamine pools and, then, displacing spermidine from its site of interaction to kDNA.

Effects of cationic diamidines on polyamine metabolism in the trypanosomatid Crithidia fasciculata

The effect of a series of five recently synthesized cationic diamidines on cell proliferation and polyamine metabolism was studied on cultures of the model Trypanosomatid Crithidia fasciculata. Compounds displaying two arylic moieties (CGP039937A and CGP040215A) were ten fold more cytostatic than those displaying only one arylic residue (CGP033829A, CGP035753A and CGP036958A). The depletion of intracellular polyamine, putrescine and spermidine, pools and the effect of these compounds on S-adenosylmethionine decarboxylase and putrescine uptake suggest the requirement of two arylic groups in their chemical structure to obtain measurable effects on both polyamine metabolism and cell growth.

Putrescine active uptake system in the Trypanosomatid Crithidia fasciculata

Using the insect Trypanosomatid Crithidia fasciculata as a model parasite of mammalian pathogenic flagellates, i.e. Leishmania and Trypanosoma spp., we have studied the kinetic and regulatory characteristics of the polyamine uptake system. Putrescine transport was age-dependent with maximum expression values at the proliferative logarithmic phase. Putrescine transport in Crithidia fasciculata was energy-dependent and against a putrescine concentration gradient. The integrity of the membrane sulfhydryl groups was absolutely required for optimum transport rates. The specificity of this mechanism was studied in the presence of a series of different chain length aliphatic diamines, showing the high specificity for putrescine and the poor effect of this series at the highest concentration analyzed as well as the higher polyamines spermidine and spermine. Finally, the well-known inhibitor of polyamine biosynthesis, DFMO, led to an upward regulation of putrescine uptake correlating with the depletion of intracellular polyamine pool. In addition, the presence of high concentrations of putrescine in the culture medium produced a downward regulation of this system.

Bacterial mutagenic evaluation of Luxabendazole, a new broad spectrum anthelmintic, with the Salmonella typhimurium His- and the Escherichia coli Tryp- reversion tests

Luxabendazole is a new benzimidazole carbamate chemotherapeutic agent, which has proved to be effective against adult and immature stages of the major gastrointestinal nematodes, trematodes and cestodes. The mutagenic properties of Luxabendazole were investigated in the in vitro Ames Salmonella and E. coli tests. The product was tested at concentrations of 0.5, 5, 50, 500, 1250 and 2500 micrograms/plate in the TA1535, TA1538, TA98 and TA100 strains of Salmonella typhimurium, and 0.5, 5, 50 and 500 micrograms/plate in the WP2, WP2uvrA- and its pKM 101-containing derivative CM891 (WP2 uvrA- pKM101) strains of Escherichia coli, with and without S9 microsomal activation (post-mitochondrial liver fraction from Wistar rats pretreated with Aroclor(R)). Positive and negative controls were included in each experiment. From the present study it can be concluded that Luxabendazole, over a dose range of 0.5-2500 micrograms/plate, is unlikely to present a mutagenic hazard, as demonstrated by the Ames test.

Fluorinated analogues of L-ornithine are powerful inhibitors of ornithine decarboxylase and cell growth of Leishmania infantum promastigotes

Fluorinated analogues of L-ornithine have been tested on growth and ornithine decarboxylase arising from L.infantum cytosolic extracts. EC50 values estimated from dose/response curves were 38 microM, 2.62 microM and 4.64 microM for alpha-DFMO, delta-MFMO and delta-MFMOme respectively. Also the inhibition produced by all three compounds was effectively reverted by exogenous putrescine, pointing towards the inhibition of L.infantum ODC. ODC from logarithmic phase cytosolic extracts was physicochemically and kinetically characterized, showing a long half-life (more than 24 h) and a km value for L-ornithine of 98 microM. Finally, the inhibitory effect of fluorinated analogues of L-ornithine was analysed on L.infantum ODC showing a time-dependent irreversible behavior, with Ki values estimated on 125 microM, T1/2 3.5 min for alpha-DFMO; 13.3 microM, T1/2 1.8 min for delta-MFMO and 4.3 microM, T1/2 4 min for delta-MFMOme.

Pharmacokinetics of triclabendazole in rabbits

1. Pharmacokinetic profiles of triclabendazole (TCBZ) following intravenous (i.v.) and oral administration of the drug in rabbits were carried out. 2. In normal rabbits, TCBZ was metabolized rapidly to its sulphoxide (TCBZ-SO) and sulphone (TCBZ-SO2) derivatives following administration, with undetectable concentrations of unchanged TCBZ in the plasma of the treated animals at any time (detection limit, 10 ng/ml). 3. The disposition kinetics of this drug in rabbits can be described by a two-compartment open model. 4. Mean peak concentrations in plasma of TCBZ-SO and TCBZ-SO2 of 12.41 micrograms/ml and 9.5 micrograms/ml occurred 7.5 and 9.5 hr after oral administration, respectively. 5. Both metabolites were eliminated slowly from plasma with elimination half-lives of 16.86 hr for the sulphoxide and 13 hr for the sulphone. 6. The area under the plasma concentration versus time curve (AUC) was 240 mg hr/l for the sulphoxide, higher than that found for the sulphone, 185 g hr/l.

4',6-Diamidino 2-phenylindole is a new reversible inhibitor of diamine oxidase and S-adenosyl-L-methionine decarboxylase from mammalian tissues

1. 4',6-Diamidino-2-phenylindole is a powerful reversible inhibitor of porcine kidney diamine oxidase and partially purified rabbit liver S-adenosyl-L-methionine decarboxylase. 2. This diamidine has shown to be a competitive inhibitor of porcine kidney diamine oxidase with a Ki value of 13 microM. 3. A similar inhibitory pattern has been found on rat liver S-adenosyl-L-methionine decarboxylase with an estimated Ki of 21 microM.

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.

Reversed-phase ion-pair high-performance liquid chromatographic determination of triclabendazole metabolites in serum and urine

An ion-pair high-performance liquid chromatographic method was developed for measuring the concentrations of triclabendazole metabolites (sulphoxide and sulphone) in plasma and urine samples. The diluted biological fluids are ultrafiltered before chromatography through a 30,000 relative molecular mass cut-off filter and then injected into a C18 column. They are then isocratically eluted with a mobile phase consisting of 0.05 M phosphate buffer (pH 7.0)-acetonitrile (55:45, v/v) with addition of 1.0 mmol/l sodium decanesulphonate and monitored by ultraviolet-visible spectrophotometry at 312 nm. Recoveries over the range 0.01-9.0 micrograms/ml for triclabendazole sulphoxide and sulphone are, respectively, 91.7% and 91.6% in serum and 90.3% and 90.2% in urine. For both metabolites, the limit of detection is 10 ng/ml in both urine and serum.

Inhibition of diamine oxidase from porcine kidney by pentamidine and other aminoguanidine compounds

1. Three bisguanidine compounds (those of pentamidine, streptidine and phenformin) were compared for their in vitro inhibitory capacity on diamine oxidase activity (EC 1.4.3.6), the first enzyme of putrescine degradation. 2. Pentamidine was the most potent inhibitor, and phenformine the weaker. Two and a half micromoles of pentamidine was enough to reduce the enzyme activity by 50%, while streptidine and phenformin produced the same effect at concentrations greater than 0.90 and 4 mM, respectively. 3. Pentamidine, streptidine and phenformin appeared to be non-competitive inhibitors, and the Ki values calculated by a Dixon plot were 3 microM, 0.95 mM and 4 mM, respectively.

Putrescine transport system in Leishmania infantum promastigotes

A transport system for putrescine in Leishmania infantum (= L. donovani infantum) promastigotes has been identified and characterized by measuring the uptake of radioactively labelled putrescine. Putrescine uptake was time- and temperature-dependent without any accumulation taking place at 0 degrees C. Uptake of putrescine was maximal at pH values near neutrality. Putrescine uptake showed an apparent Km = 1.08 +/- 0.12 microM and a Vmax = 1.74 + 0.62 pmol min-1 (10(6) cells)-1. The effect of metabolic poisons and uncoupling agents suggests that the putrescine uptake was energy-dependent. The transport system seemed to be highly specific for putrescine as neither aminoacids nor related compounds tested showed any competition with putrescine uptake. The trypanocide Berenil inhibited almost completely the putrescine uptake with non-competitive kinetics and a value of Ki = 43 microM.