Resistance reversal action of ketoconazole against mefloquine resistance of Plasmodium yoelii nigeriensis

Ketoconazole at 200 mg/kg dose has been found to exert marginal antimalarial action against multidrug resistant (MDR) Plasmodium yoelii nigeriensis (P. yoelii nigeriensis) in Swiss mice with 25% protection (2/8 mice) while at lower Ketoconazole dose i.e., 75-100 mg/kg, 14.28% mice were protected. Mefloquine (MFQ) (at 8 and 16 mg/kg) exerted suppressive action against MDR P. yoelii nigeriensis resulting in 25 and 14.28% protection of mice respectively. Combined treatment with Ketoconazole and mefloquine resulted in protection of 5/6 mice (83.33%) at MFQ 4 mg/kg + Ketoconazole 100 mg/kg dose, 7/8 (87.5%) mice at MFQ 8 mg/kg + Ketoconazole 20 mg/kg dose and 5/7 (71.42%) mice at MFQ 16 mg/kg + Ketoconazole 25 mg/kg dose and 5/6 (83.33%) mice at MFQ 16 mg/kg + Ketoconazole 100 mg/kg dose. Ketoconazole has been found to enhance the protective effect of mefloquine against MFQ resistant P. yoelii nigeriensis resulting in 66-88% protection of the mice treated with the appropriate combinations. The combination also increased suppression of parasitaemia at different times. The Ketoconazole combination with MFQ significantly increased the mean survival time of the treated mice compared to individual drugs alone. The study shows that Ketoconazole when administered with MFQ exerts bio-enhancing action against mefloquine resistance of MDR P. yoelii nigeriensis.     

Azithromycin: antimalarial profile against blood- and sporozoite-induced infections in mice and monkeys

The spectrum of antimalarial activity of the new macrolide antibiotic azithromycin was evaluated against blood- and sporozoite-induced infections with a chloroquine-resistant strain of Plasmodium yoelii nigeriensis (N-67) in Swiss mice and with simian parasite Plasmodium cynomolgi B in rhesus monkeys. Against experimental rodent malaria, a 70 mg/kg/day dose showed curative blood-schizontocidal activity in a four-dose regimen administered orally from day 0 to day 3 or from day 2 to day 5 to mice harboring established infection. The curative response was also obtained with a 40 mg/kg/day dose administered in an extended seven-dose (days 0-6) regimen. Azithromycin was also effective in the causal prophylactic test, since a 50 mg/kg dose from day -1 to day +2 protected mice against P. y. nigeriensis (N-67) sporozoite challenge. In comparison, erythromycin did not show either of the above activities up to a 405 mg/kg/day dose in identical regimens. Comparison of the ED(90) values showed that azithromycin was 31-fold more effective than erythromycin as a blood schizontocide. In the simian model, trophozoite-induced infections of P. cynomolgi B were cured with 25 mg/kg/day azithromycin administered for 7 days. In the causal prophylactic test, the prepatent period was significantly extended in monkeys challenged with P. cynomolgi B sporozoites, presumably because of the growth inhibition of preerythrocytic schizonts in hepatocytes. Azithromycin did not exhibit any hypnozoitocidal (dormant exoerythrocytic stages) activity at 25 mg/kg/day in a seven-dose regimen.     

Plasmodium berghei: parasite clearance after treatment with dihydroartemisinin in an asplenic murine malaria model

Clinical reports indicate that malaria-infected asplenic patients have a reduced capacity for parasite clearance despite intensive antimalarial therapy. The aim of this study was to evaluate the efficacy of dihydroartemisinin in an asplenic murine malaria model. Mice were inoculated with Plasmodium berghei parasitised erythrocytes and received a single dose of dihydroartemisinin 56 h later, at 2-5% parasitaemia. Haematology, liver biochemistry and histopathology of key organs were performed to evaluate organ response to malaria infection. The nadir parasitaemia occurred 20 h after dihydroartemisinin administration, falling 2.8- to 6.0-fold and 2.7- to 6.9-fold in asplenic and intact mice, respectively, (10-100 mg/kg). Histopathology indicated increased stimulation of liver function/activity during malaria infection of asplenic mice (as compared to intact mice). Overall efficacy of single-dose dihydroartemisinin treatment in asplenic mice was similar to intact mice although the rate of recrudescence in asplenic mice was significantly greater than intact mice at 30 and 100 mg/kg. The asplenic murine malaria model could be used in pre-clinical studies of splenic function and clearance of malaria parasites, pathophysiological studies or antimalarial drug efficacy in asplenia.     

The decline of malaria in Finland – the impact of the vector and social variables

Background

Resistance to anti-malarial drugs hampers control efforts and increases the risk of morbidity and mortality from malaria. The efficacy of standard therapies for uncomplicated Plasmodium falciparum and Plasmodium vivax malaria was assessed in Chumkiri, Kampot Province, Cambodia.

Methods

One hundred fifty-one subjects with uncomplicated falciparum malaria received directly observed therapy with 12 mg/kg artesunate (over three days) and 25 mg/kg mefloquine, up to a maximum dose of 600 mg artesunate/1,000 mg mefloquine. One hundred nine subjects with uncomplicated vivax malaria received a total of 25 mg/kg chloroquine, up to a maximum dose of 1,500 mg, over three days. Subjects were followed for 42 days or until recurrent parasitaemia was observed. For P. falciparum infected subjects, PCR genotyping of msp1, msp2, and glurp was used to distinguish treatment failures from new infections. Treatment failure rates at days 28 and 42 were analyzed using both per protocol and Kaplan-Meier survival analysis. Real Time PCR was used to measure the copy number of the pfmdr1 gene and standard 48-hour isotopic hypoxanthine incorporation assays were used to measure IC₅₀ for anti-malarial drugs.

Results

Among P. falciparum infected subjects, 47.0% were still parasitemic on day 2 and 11.3% on day 3. The PCR corrected treatment failure rates determined by survival analysis at 28 and 42 days were 13.1% and 18.8%, respectively. Treatment failure was associated with increased pfmdr1 copy number, higher initial parasitaemia, higher mefloquine IC₅₀, and longer time to parasite clearance. One P. falciparum isolate, from a treatment failure, had markedly elevated IC₅₀ for both mefloquine (130 nM) and artesunate (6.7 nM). Among P. vivax infected subjects, 42.1% suffered recurrent P. vivax parasitaemia. None acquired new P. falciparum infection.

Conclusion

The results suggest that artesunate-mefloquine combination therapy is beginning to fail in southern Cambodia and that resistance is not confined to the provinces at the Thai-Cambodian border. It is unclear whether the treatment failures are due solely to mefloquine resistance or to artesunate resistance as well. The findings of delayed clearance times and elevated artesunate IC₅₀ suggest that artesunate resistance may be emerging on a background of mefloquine resistance.     

Orcadian Variation in Amikacin Clearance and Its Effects on Efficacy and Toxicity in Mice with and Without Immunosuppression

A once-daily dosage regimen has been recently recommended in the use of aminoglycoside antibiotics since they induce a postantibiotic effect. In choosing this regimen, one must determine the most appropriate time of day for administration of the drug. We investigated the effects of the timing of amikacin (AMK) administration on the kinetics, the efficacy against intraperitoneal infection with Pseudomonas aeruginosa, and the toxicity of AMK in mice with and without immijnosuppression. We found circadian variations in the kinetics, efficacy, and toxicity of the drug in mice. Male and female ICR mice, which were housed under a light-dark (12:12 h) cycle with free food and water intake, were injected subcutaneously with AMK sulfate 50 mg/kg body wt. There was a circadian variation in AMK clearance for both sexes with the maximum value in the dark phase and the minimum in the light phase after a single administration. When AMK 500 mg/kg/day was repeatedly administered once daily for 30 days, higher toxicity was demonstrated in mice injected with the drug at the time of day with lower AMK clearance, although no difference was demonstrated in the toxicity between the two time points with different AMK clearance when AMK 1,500 mg/kg was administered in a single dose. The ED₅₀ of AMK to cure the infected mice in the midlight phase (13:00 h) with lower clearance was significantly lower than that in the middark phase (01:00 h) with higher clearance. In contrast, the ED₅₀ in the early light phase (09:00 h) was significantly lower than that in the early dark phase (21:00 h), although AMK clearance was not different between these two different time points. In mice premedicated with cyclophosphamide to suppress immune functions, the difference in the ED₅₀ of AMK was still demonstrated between 13:00 and 01:00 h, but not between 09:00 and 21:00 h. The present study shows not only that there were circadian variations in both AMK clearance and toxicity after repeated administration, but also that there was a circadian variation in the efficacy of AMK in mice infected with P. aeruginosa. These results suggest that the timing of drug administration should be considered in pharmacotherapy with AMK and that the most appropriate time of administration in mice and nocturnal animals may be in the midlight (resting) phase. They also suggest that the ED₅₀ of AMK. against P. aeniginosa infection may be influenced not only by the circadian variation in pharmacokinetics but also by the variations in immune systems suppressed by cyclophosphamide.     

Inhibitory Effect of Silkworm-Extract(SE) on Monoamine Oxidase Activity in Vitro and in Vivo

In vitro.MAO‐A activity was inhibited 16‐25%, and MAO‐B activity was inhibited 20‐50% by SE treatment (12.5, 25 and 50 μg), In vivo.male C57BL/6 mice Received intraperitoneal injection of SE (20 mg/kg/day) for 14 days. The results showed that MAO‐A activity of pre‐SE‐treatment mice brain was inhibited in whole brain, cerebral cortex, substantia nigra. MAO‐B activity of pre‐SE‐treatment mice brain was inhibited in substantia nigra and cerebellum than saline‐treated control group. These results suggest that SE inhibits MAO activity in vivo.which would be expected to results in anti‐depressive and neuroprotective effects.     

Antimalarial activity of endoperoxide compound 6-(1,2,6,7-tetraoxaspiro[7.11]nonadec-4-yl)hexan-1-ol

Plasmodium falciparum, the major causative parasite for the disease, has acquired resistance to most of the antimalarial drugs used today, presenting an immediate need for new antimalarial drugs. Here, we report the in vitro and in vivo antimalarial activities of 6-(1,2,6,7-tetraoxaspiro[7.11]nonadec-4-yl)hexan-1-ol (N-251) against P. falciparum and Plasmodium berghei parasites. The N-251 showed high antimalarial potencies both in the in vitro and the in vivo tests (EC₅₀ 2.3 × 10⁻⁸ M; ED₅₀ 15 mg/kg (per oral)). The potencies were similar to that of artemisinin in vitro and greater than artemisinin's activity in vivo (p.o.). In addition, N-251 has little toxicity: a single oral administration at 2000 mg/kg to a rat gave no health problems to it. Administration of N-251 to mice bearing 1% of parasitemia (per oral 68 mg/kg, 3 times a day for 3 consecutive days) resulted in a dramatic decrease in the parasitemia: all the 5 mice given N-251 were cured without any recurrence, with no diarrhea or weight loss occurring in the 60 days of experiment. N-251 deserves more extensive clinical evaluation, desirably including future trials in the human.     

Oral artesunate prevents Plasmodium berghei Anka infection in mice

Artesunate, a semi-synthetic derivative of a naturally occurring anti-malarial artemisinin was compared with chloroquine in C57BL/6 mice infected with Plasmodium berghei Anka (PbA). A 7-day oral administration of artesunate prevented parasitaemia at 10 mg/kg/day. However, recrudescence of parasitaemia and cerebral malaria occurred upon cessation of treatment followed by death within 28 days. However, a 14-day course of artesunate (100 mg/kg/day) prevented completely the development of parasitaemia and cerebral malaria with a survival of more than 60-days as did 10 mg/kg/day chloroquine. These data demonstrate that oral artesunate inhibits PbA and prevents cerebral malaria, but needs to be administered at high dose and for prolonged time to eradicate PbA infection in mice.     

Circadian phase modulates the enhancing effect of the Egyptian Moringa peregrina extract on learning and memory in mice

One of the most important issues nowadays is memory disorders. The exact circadian modulation of learning and memory is still under investigation. The present study was carried out to evaluate the probable enhancing and neuroprotective effects of the Egyptian Moringa peregrina; administered at two different Zeitgeber times (ZT), on learning and memory in mice. M. peregrina dried leaves were aqueously extracted and intranasally (IN) administered at four doses (viz. 12.5, 25, 50, and 100 mg/kg). Twenty animal groups (n = 8/group) were treated with M. peregrina at ZT 3:00 vs. 15:00 representing the rest (day) vs. active (night) phases, respectively. Additionally, sub-chronic effect of daily IN administration of the 25 mg/kg dose for two weeks was examined at ZT 3:00 vs. 15:00. Memory performance was assessed after 1, 2 weeks of treatment and a 3rd recovery week. Memory test was performed at ZT 17:00 by measuring the percentage of time spent in novel arm of Y-maze. Dose-response curve revealed that both 25 and 50 mg/kg doses administered at ZT 3:00 significantly improved memory efficiency. Rest phase administration significantly enhanced memory functions after 1, 2 weeks as well as after the recovery week. Moreover, IN pretreatment with M. peregrina (25 mg/kg) revealed a protective effect against scopolamine-induced amnesia. In conclusion, these findings clearly indicated that M. peregrina possesses valuable enhancing and protective effects on learning and memory processes in mice which is circadian-phase dependent.     

Combination of zingerone and dihydroartemisinin presented synergistic antimalarial activity against Plasmodium berghei infection in BALB/c mice as in vivo model

Malaria is a global health problem leading to the death of 435,000 cases in tropical and sub-tropical zones. Spread and emergence of increasing resistance to the antimalarial drugs are the major challenges in the control of malaria. Therefore, searching for alternative antimalarial drugs is urgently needed, and combination treatment preferred as an approach to address this. This study aimed to evaluate in vivo antimalarial activity of zingerone (ZN), and its combination with dihydroartemisinin (DHA) against Plasmodium berghei infected mice. ZN was prepared and tested for acute oral toxicity according to the OECD guideline. In vivo antimalarial activity of different doses of ZN and combination with DHA were determined using the 4-day suppression test. The results showed that ZN was found to be safe and no mortality within the observation period, and the lethal dose might be greater than the limited dose of 1000 mg/kg. For in vivo antimalarial test, ZN exhibited significant (p < .05) parasitemia inhibition of 30.65% and 45.75% at the doses of 50 mg/kg and 100 mg/kg, respectively. Moreover, effective dose 50 (ED₅₀) of ZN was 29.76 mg/kg. The combination treatment of ZN and DHA at the doses of ED₅₀ values at the fixed ratio 1:1 was found to present significant (p < .001) antimalarial activity as compared to ZN and DHA treated alone with markedly prolonged mean survival time. Additionally, the combination index (0.83384) revealed the synergistic antimalarial effect. It can be concluded that ZN exerted potent antimalarial activity with no toxicity, and combination treatment with DHA produced the synergistic antimalarial effect.     

Cochleates: New Lipid-Based Drug Delivery System

Abstract

Cochleates are a lipid-based tailored drug delivery system formed by the precipitation of a negatively charged lipid and a cation, for example phosphatidylserine and calcium. Hydrophobic, amphiphilic, negatively or positively charged moieties are suitable candidates to be delivered via cochleates. Various procedures have been developed allowing the control of cochleate particle size, including the trapping and hydrogel methods, which use either a direct addition or a slow diffusion of calcium into the negatively charged liposome/drug suspension. The efficacy of cochleates to encapsulate and deliver drugs was evaluated using amphotericin B as a model. Amphotericin B cochleates (CAMB) were compared to Fungizone® and AmBisome®, two commercially available AmB products. Parenterally, CAMB was given IP to ICR mice infected with Candida albicans. 100% survival was observed with low doses of CAMB (0.5 mg/kg/day, 10 days) compared to 60% for Fungizone, at the same dose. Tissue burden studies were conducted in parallel. Mice were treated daily from day 1 to day 7 post challenge and tissue burden assessed at day 8. In the kidneys, all three formulations were comparable in reducing colony counts. In the spleen, CAMB at 10 mg/kg/day was comparable to AmBisome given IV at the same dose. At 1 mg/kg/day, CAMB was more potent than Fungizone and AmBisome. Oral administration of CAMB in C57BL/6 mice, at 10 mg/kg results in high levels of AmB in target tissues. Multiple daily doses (10) showed accumulation of AmB in key tissues (liver, lungs, spleen, and kidneys) and AmB tissue concentrations are raised to therapeutic levels. Orally administered CAMB are highly effective against fungal infections in mice at very low doses. Balb/C mice were infected with Candida albicans and were given oral CAMB as a daily dose for 15 days. Comparison was done to AmBisome given orally at 10 mg/kg and Fungizone IP. 100% survival was obtained with CAMB at doses as low as 0.5 mg/kg/day (15 days). CAMB eradicate Candida from lungs when given at 2.5 mg/kg/day and was comparable to Fungizone given IP at almost the same dose (2 mg/kg/day). The comparison between CAMB and AmBisome shows that oral CAMB is 10 times more effective than oral AmBisome in reducing colony counts in both kidneys and lungs. Orally administered CAMB were non-toxic even at the highest dose of 50 mg/kg/day (14 days). This was demontrated by 100% survival of the animals and normal histopathology analysis. No lesions in the kidneys, GI tract, lungs, liver and spleen was observed despite the substantial amount of AmB in these organs. AmB cochleate promise to be a safe, broad spectrum, effective and orally available, antifungal formulation.     

Hepatoprotective effect of bis(4‐methylbenzoyl) diselenide against CCl4‐induced oxidative damage in mice

From a pharmacological point of view, organoseleniums are compounds with important and interesting antioxidant and biological activities. The aim of this study was to evaluate the hepatoprotective effect of bis(4‐methylbenzoyl) diselenide (BMD) against carbon tetrachloride (CCl₄)–induced oxidative damage in mice. The animals received BMD (25 mg/kg p.o., for 3 days), and after 1 day, CCl₄ (1 mg/kg body weight) was administered by intraperitoneal route. One day after the CCl₄ exposure, the animals were euthanized for biochemical and histological analysis. Treatment with BMD (25 mg/kg p.o.) protected against aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma‐glutamyl transferase and lactate dehydrogenase activity increases induced by CCl₄ plasma exposure. Treatment with BMD (25 mg/kg) protected against increases in thiobarbituric reactive species and decreasing non‐protein thiols and ascorbic acid levels in liver of mice. Catalase and superoxide dismutase activity inhibition in the liver caused by CCl₄ were protected by treatment with BMD (25 mg/kg). Glutathione S‐transferase activity was inhibited by CCl₄ and remained unaltered even after treatment with BMD. Sections of liver from CCl₄‐exposed mice presented an intense infiltration of inflammatory cells and loss of the cellular architecture. BMD (25 mg/kg) attenuated CCl₄‐induced hepatic histological alterations. The results demonstrated the hepatoprotective effects of BMD in the mouse liver, possibly by modulating the antioxidant status. Copyright © 2012 John Wiley & Sons, Ltd.     

Developmental Toxicity of the HMG‐CoA Reductase Inhibitor (PPD10558) in Rats and Rabbits

PPD10558 is an orally active, lipid‐lowering 3–hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase inhibitor (statin) being developed as a treatment for hypercholesterolemia in patients who have not been able to tolerate statins because of statin‐associated myalgia. We have studied the potential developmental toxicity effects of PPD10558 in pregnant rats and rabbits given daily oral doses during the period of organogenesis. Rats were dosed with 0, 20, 80, or 320 mg/kg/day from Gestation Day (GD) 6 to 17 and rabbits received dose levels of 0, 12.5, 25, or 50 mg/kg/day from GD 6 to 18. Additional groups in both studies served as toxicokinetic animals and received the PPD10558 in the same manner as the main study groups at the same dose levels. Blood samples were collected from toxicokinetic animals at designated time points on GD 6 and 17 in rats and GD 6 and 18 in rabbits. Fetal exposure in rats was assessed on GD 20. Maternal and developmental parameters were evaluated in rats and rabbits on GD 20 and GD 29, respectively. No maternal and developmental toxicity was observed at any of the dose levels used in the rat study. Evidence of fetal exposure was determined in fetal plasma with mean fetal concentrations of PPD10558 and the metabolite (PPD11901) found to be between 1 and 6% of the mean maternal concentrations. In rabbits, marked maternal toxicity including mortality (eight deaths; 1 dose at 25 and 7 at 50 mg/kg/day), abortions (2 at 25 mg/kg/day and 6 at 50 mg/kg/day) and reduction in gestation body weight, gestation body weight changes and decreased food consumption were observed. In addition, fetal body weights of the combined sexes were significantly reduced at 50 mg/kg/day in comparison with the controls. Mean peak exposure (Cmax) and total exposure (AUC(0–24)) of PPD11901 in both rats and rabbits were higher than that of PPD10558 on GD 6 and GD 17 at each of the three dose levels.. Based on the results of these studies, the no observed adverse effect level (NOAEL) for maternal and developmental toxicity in rats was considered to be ≥320 mg/kg/day, the highest dose level used in the study. The NOAEL for maternal and developmental toxicity in rabbits was 12.5 mg/kg/day and 25 mg/kg/day, respectively.     

Anti-influenza A virus effect of Hypericum perforatum L. extract

To study the antiviral effect of Hypericum perforatum L. extract (HPE) on influenza A virus (IAV) (H₁N₁) in vitro and in vivo. Cytopathic effect (CPE) and neutral red (NR) dye uptake were used to examine the antiviral effect of HPE on Madin Darby Canine Kidney (MDCK) cells which were infected with IAV in vitro. HPE was effective against influenza A virus (IAV) in vitro, with a 50% effective concentration (EC₅₀) of 40 μg/mL. The mean 50% cytotoxic concentration (CC₅₀) in the MDCK used in these experiments was 1.5 mg/mL. Ribavirin was run in parallel with EC₅₀ values of 5.0 μg/mL; the mean CC₅₀ for ribavirin was 520 μg/mL. Oral gavage administrations of HPE or ribavirin to mice infected with the IAV were highly effective in preventing death, slowing the decline of arterial oxygen saturation, inhibiting lung consolidation and reducing lung virus titers. The minimum effective dose of HPE in these studies was 31.25 mg/kg/day, which was administered twice daily for 5 d beginning 4 h prior to virus exposure. Below a dosage of 2000 mg/kg/day, almost all treated mice survived, which suggests that HPE is of low toxicity. Ribavirin’s minimum effective dose was 40 mg/kg/day with the LD50 determined to be 200 mg/kg/day. Delay of the initiation of either HPE or ribavirin therapy, using approximately 1/3 LD₅₀ dose each time, could still be protective as late as 48 h after exposure to the IAV. While both agents appeared to have similar efficacy against IAV infections, HPE was considered to be less toxic and may warrant further evaluation as a possible therapy for influenza. Foundation items: One Hundred Person Project of The Chinese Academy of Sciences (2008-287); The Project of Basic Scientific Research Fund for Central Public-Welfare of Institute of Sciences (BRF070402).     

Assessment of female and male fertility in Sprague-Dawley rats administered vorinostat, a histone deacetylase inhibitor

BACKGROUND: Histone deacetylase (HDAC) inhibitors have been shown to mediate the regulation of gene expression, induce cell growth, cell differentiation, and apoptosis of tumor cells. These compounds are now marketed or are in clinical development. One such HDAC inhibitor, vorinostat (suberoylanilide hydroxamic acid [SAHA], Zolinza), was assessed for its potential effects on fertility in Sprague–Dawley rats. METHODS: Female rats were administered oral dose levels of 0 (vehicle only), 15, 50, or 150 mg/kg/day of vorinostat for 14 days before cohabitation, during cohabitation, and through Gestation Day (GD) 7. In a separate study, male rats were administered oral dose levels of 0 (vehicle only), 20, 50, or 150 mg/kg/day for 10 weeks before cohabitation, during cohabitation, and until the day before scheduled sacrifice (approximately 14 weeks total). In both studies, % peri‐implantation loss and % postimplantation loss were evaluated on GD 15–17. Testicular weight and histomorphology, cauda epididymal sperm count, and sperm motility were evaluated in the male rat study at termination. RESULTS: There were treatment‐related decreases in body weight gain at 150 mg/kg/day in both studies. There were no effects on mating or fertility indices in either study. In the female study there were increased numbers of corpora lutea in all drug‐treated groups (only 1 or 2 affected dams in low and mid‐dose groups), and a marked increase in percent postimplantation loss only in the high‐dose group. No treatment‐related effects were observed on litter or sperm parameters of the male study. CONCLUSIONS: Vorinostat had no effects on mating or fertility in rats up to 150 mg/kg/day. There were no indications of reproductive toxicity in drug‐treated male rats. Increases in corpora lutea or resorptions were observed in treated female rats. Birth Defects Res (Part B) 80:1–8, 2007. © 2007 Wiley‐Liss, Inc.     

Effects of Melamine and Cyanuric Acid on Embryo‐Fetal Development in Rats

After the outbreak of acute renal failure associated with melamine‐contaminated pet food, melamine and melamine‐related compounds have become of great interest from a toxicologic perspective. We investigated the potential effects of melamine in combination with cyanuric acid (M + CA, 1:1) on pregnant dams and embryo‐fetal development in rats. M + CA was orally administered to pregnant rats from gestational days 6 through 19 at doses of 0, 3, 10, and 30 mg/kg/day of both melamine and cyanuric acid. Maternal toxicity of rats administered 30 mg/kg/day M + CA was manifested as increased incidences of clinical signs and death; gross pathologic findings; higher blood urea nitrogen and creatinine levels; lower body weight gain and food intake; decreased thymus weight; and increased heart, lung, and kidney weights. Histopathological examinations revealed an increase in the incidence of congestion, tubular necrosis/degeneration, crystals, casts, mineralization, inflammatory cells in tubules, tubular dilation, and atrophy of glomeruli in maternal kidneys, whereas fetal kidneys did not show any histopathological changes. Developmental toxicity included a decrease in fetal (28%) and placental weights and a delay in fetal ossification (n = 7). Increased incidence of gross and histopathological changes in the maternal kidney was also found in the middle dose group (n = 12). No treatment‐related maternal or developmental effects were observed in the low dose group (n = 12). Under these experimental conditions, M + CA is embryotoxic at an overt maternotoxic dose in rats and the no‐observed‐adverse‐effect level of M + CA is considered to be 3 mg/kg/day for pregnant dams and 10 mg/kg/day for embryo‐fetal development.     

Occurrence and fate of fetal lumbar rib induced by Scutellariae radix in rats

BACKGROUND: This study was conducted to evaluate the occurrence and fate of fetal lumbar rib induced by Scutellariae radix (SR) in rats. METHODS: Water extracts of SR were orally administered to pregnant rats from day 7 to day 17 of gestation at a dose of 186 mg/kg/day, equivalent to 25 g/kg of starting material, representing a 100‐fold increase over typical human intake level. RESULTS: The incidence of fetal lumbar rib in the SR‐treated group was increased on gestational day 20 and then decreased on postnatal day 50. The weight of fetuses in the SR‐treated group tended to be less than that in the control group. Alkaline phosphatase in SR‐treated dams was increased on gestational day 20, but was decreased on postnatal day 50. There were no significant differences between the vehicle control and SR‐treated groups in maternal body weight, embryological, histopathological, hematological, and serum biochemical changes. CONCLUSIONS: The present data suggest that the appearance of lumbar rib induced by SR is a transient fetal variation rather than teratogenicity or maternal toxicity. Birth Defects Res (Part B) 89:201–206, 2010. © 2010 Wiley‐Liss, Inc.     

Resveratrol induces cell‐cycle disruption and apoptosis in chemoresistant B16 melanoma

Resveratrol, a naturally occurring polyphenol, has been shown to possess chemopreventive activities. In this study, we show that resveratrol (0–500 µM) inhibits the growth of a doxorubicin‐resistant B16 melanoma cell subline (B16/DOX) (IC₅₀ = 25 µM after 72 h, P < 0.05). This was accomplished by imposing an artificial checkpoint at the G₁–S phase transition, as demonstrated by cell‐cycle analysis and down‐regulation of cyclin D1/cdk4 and increased of p53 expression level. The G₁‐phase arrest of cell cycle in resveratrol‐treated (10–100 µM) B16/DOX cells was followed by the induction of apoptosis, which was revealed by pyknotic nuclei and fragmented DNA. Resveratrol also potentiated at subtoxic dose (25 µM for 24 h) doxorubicin cytotoxicity in the chemoresistant B16 melanoma (P < 0.01). When administered to mice, resveratrol (12.5 mg/kg) reduced the growth of an established B16/DOX melanoma and prolonged survival (32% compared to untreated mice). All these data support a potential use of resveratrol alone or in combination with other chemotherapeutic agents in the management of chemoresistant tumors. J. Cell. Biochem. 110: 893–902, 2010. © 2010 Wiley‐Liss, Inc.     

Effect of Age,Duration of Exposure,and Dose of Atrazine on Sexual Maturation and the Luteinizing Hormone Surge in the Female Sprague–Dawley Rat

Atrazine (ATZ) was administered daily by gavage to pregnant female Sprague Dawley rats at doses of 0, 6.25, 25 or 50 mg/kg/day, either during gestation, lactation and post‐weaning (G/L/PW cohort) to F₁ generation female offspring or only from postnatal day (PND 21) until five days after sexual maturation (vaginal opening) when the estrogen‐primed, luteinizing hormone (LH) surge was evaluated (PW cohort). Additional subgroups of F₁ females received the vehicle or ATZ from PND 21–133 or from PND 120–133. Slight reductions in fertility and the percentage of F₁ generation pups surviving to PND 21 in the gestationally exposed 50 mg/kg dose group were accompanied by decreased food intake and body weight of dams and F₁ generation offspring. The onset of puberty was delayed in of the F₁ generation G/L/PW females at doses of 25 and 50 mg/kg/day. F₁ generation females in the PW high‐dose ATZ group also experienced a delay in the onset of puberty. ATZ had no effect on peak LH or LH AUC in ovariectomized rats 5 days after sexual maturation, irrespective of whether the F₁ generation females were treated from gestation onward or only peripubertally. There was no effect of ATZ treatment on the estrous cycle, peak LH or LH AUC of F₁ generation females exposed from gestation through to PND 133 or only for two weeks from PND 120–133. These results indicate that developing females exposed to ATZ are not more sensitive compared to animals exposed to ATZ as young adults     

Dimeric cyclohexane-1,3-dione oximes inhibit wheat acetyl-CoA carboxylase and show anti-malarial activity

A series of dimeric 1,3-cyclohexanedione oxime ethers were synthesized and found to have significant antiplasmodial activity with IC₅₀’s in the range 3–12 μM. The most active dimer was tested in the Plasmodium berghei mouse model of malaria and at a dose of 48 mg/kg gave a 45% reduction in parasitaemia. Several commercial herbicides, all known to be inhibitors of maize acetyl-CoA carboxylase, were also tested for antimalarial activity, but were essentially inactive with the exception of butroxydim which gave an IC₅₀ of 10 μM.