Allopurinol Resistance in Leishmania infantum from Dogs with Disease Relapse

Background

Visceral leishmaniasis caused by the protozoan Leishmania infantum is a zoonotic, life threatening parasitic disease. Domestic dogs are the main peridomestic reservoir, and allopurinol is the most frequently used drug for the control of infection, alone or in combination with other drugs. Resistance of Leishmania strains from dogs to allopurinol has not been described before in clinical studies.

Methodology/Principal Findings

Following our observation of clinical disease relapse in dogs under allopurinol treatment, we tested susceptibility to allopurinol of L. infantum isolated from groups of dogs pre-treatment, treated in remission, and with disease relapse during treatment. Promastigote isolates obtained from four treated relapsed dogs (TR group) showed an average half maximal inhibitory concentration (IC50) of 996 μg/mL. A significantly lower IC50 (P = 0.01) was found for isolates from ten dogs before treatment (NT group, 200 μg/mL), as well as for five isolates obtained from treated dogs in remission (TA group, 268 μg/mL). Axenic amastigotes produced from isolates of the TR group also showed significantly higher (P = 0.002) IC50 compared to the NT group (1678 and 671 μg/mL, respectively). The lower sensitivity of intracellular amastigotes from the TR group relative to those from the NT group (P = 0.002) was confirmed using an infected macrophage model (6.3% and 20% growth inhibition, respectively at 300 μg/mL allopurinol).

Conclusions

This is the first study to demonstrate allopurinol resistance in L. infantum and to associate it with disease relapse in the canine host. These findings are of concern as allopurinol is the main drug used for long term control of the disease in dogs, and resistant L. infantum strains may enhance uncontrolled transmission to humans and to other dogs.     

Polarity of sperm entry in the ascidian egg

We have investigated the point of sperm entry in denuded eggs of the ascidian Phallusia mammillata. In contrast to what is generally believed, the sperm show a strong tendency to enter the animal hemisphere rather than the vegetal hemisphere. After entry, the sperm nucleus is carried toward the vegetal pole of the egg during the cortical contraction which occurs within a few minutes after fertilization. This polarity of sperm entry is abolished and the entry point is randomized by pretreating the eggs with cytochalasin D. We suggest that cytochalasin may act by randomizing components needed for sperm attachment or fusion, or structures needed for sperm entry.     

Low aromatase activity and gene expression in human fetal testes

Because of previous indications that estradiol (E2) plays a role in the regulation of testicular testosterone (T) production in some species, the production of E2 and aromatase gene expression in human fetal testes were investigated. Testicular minces from 14 fetuses (fetal age 15-23 weeks) were incubated with and without 200 ng/ml highly purified hCG, and the production of E2 and T was measured by RIA. Basal T production was high at 15-18 weeks of gestation and decreased thereafter. Estradiol production was low in all testes. Aromatase mRNA (P-450 arom messenger ribonucleic acid) was not detectable in fetal testicular tissues when studied by Northern and dot blot techniques. Placenta and fetal liver expressed aromatase mRNA, but fetal ovary contained only miniscule amounts. HCG significantly stimulated the production of both T and E2 in the testes of older fetuses (19-23 weeks), but the testicular E2 production of the youngest fetuses (15-18 weeks) did not increase significantly after hCG stimulation. These results indicate that aromatase activity and gene expression are very low in human fetal testes. These findings suggest that E2 may not play a major role in testicular T production in the human fetus.     

Metabolism of lignin related aromatic compounds by Aspergillus japonicus

Archives of Microbiology - Aspergillus japonicus metabolizes a wide variety of aromatic compounds, some of them resulting from lignin degradation. The efficient conversion of such compounds is...     

Beneficial actions of nalorphine during hemorrhagic shock in cats

Endogenous opiates have been reported to have detrimental effects on the circulatory system during hemorrhagic shock. However, the specific opiate receptor subtype which mediates these actions has not been defined. In the present study, we have utilized the mixed agonist/antagonist, nalorphine (N-allylnormorphine), which exhibits kappa (kappa) and sigma (sigma) receptor agonism as well as mu (mu) receptor antagonism, to investigate the role of the mu receptor in hemorrhagic shock. Nalorphine (2 mg/kg) produced no significant changes in any observed experimental variable in sham-shocked animals. Shocked animals treated with nalorphine (2 mg/kg) maintained significantly higher final mean arterial blood pressures (MABP) than animals which received only vehicle (102 +/- 3.8 vs 61 +/- 6.6 mm Hg, respectively, p less than 0.001). In addition, nalorphine significantly reduced the rise in plasma MDF activity observed in untreated hemorrhaged animals (42 +/- 3.0 vs 59 +/- 4 U/ml, p less than 0.02). Our results support a significant role for the mu receptor in the deleterious actions of endogenous opioids during hemorrhagic shock.     

A radioimmunoassay for dehydroepiandrosterone sulfate in the circulation of rhesus monkeys

A radioimmunoassay for dehydroepiandrosterone sulfate (DHAS) was established and validated for use in the rhesus monkey. The validation demonstrated the co-migration of immunoreactive material with tritiated dehydroepiandrosterone after hydrolysis and indicated the absence of other interfering steroids in the measurement. The application of this assay to perinatal samples verified that there are microgram quantities of DHAS present in the circulation. The measurement of circulating concentrations of DHAS in male and female rhesus monkeys at different stages of development demonstrated the absence of increases associated with puberty in this macaque species. Concentrations of DHAS were similar in adult males and females, but were elevated in pregnant females (p less than 0.05). Adult males had increased DHAS concentrations after GnRH administration (p less than 0.05), but no change was detected in infant male monkeys. Cortisol and DHAS responses of both infant and adult males occurred at a similar dose of ACTH (0.05 mU per kg versus 0.015 mU per kg, infant and adult, respectively). These data demonstrate the validity of the DHAS measurement in the rhesus monkey and suggest that the secretion of DHAS from infant and adult adrenals is generated by a similar stimulus. Since there was no evidence of gonadal secretion of DHAS in the infant, changes in either adrenal secretion and/or metabolic clearance of DHAS probably account for the microgram concentrations found during the perinatal period.     

Metabolism of phosphoenolpyruvate in the C4 cycle during photosynthesis in the phosphoenolpyruvate-carboxykinase C4 grass Spartina anglica Hubb.

The aim of this work was to investigate the fate of phosphoenolpyruvate (PEP) produced by decarboxylation of oxaloacetate during photosynthesis in the bundle sheaths of leaves of the PEP-carboxykinase C₄ grass Spartina anglica Hubb. Mesophyll protoplasts and bundle sheath cells were separated enzymically and used to investigate activities and distributions of putative enzymes of the C₄ cycle and the photosynthetic carbon metabolism of bundle sheath cells. The results indicate that neither conversion of PEP to pyruvate nor its conversion to 3-phosphoglycerate can account for all of the carbon flux through the C₄ cycle during photosynthesis. It is likely, therefore, either that PEP moves directly from bundle sheath to mesophyll or that more than one pathway of regeneration of PEP is involved in the C₄ cycle in this plant.Abbreviations Chl chlorophyll - PEP phosphoenolpyruvate - Pi phosphate - RuBP ribulose-1,5-bisphosphate