In Vitro and In Vivo Antiplasmodial Activities of Risedronate and Its Interference with Protein Prenylation in Plasmodium falciparum

The increasing resistance of malarial parasites to almost all available drugs calls for the identification of new compounds and the detection of novel targets. Here, we establish the antimalarial activities of risedronate, one of the most potent bisphosphonates clinically used to treat bone resorption diseases, against blood stages of Plasmodium falciparum (50% inhibitory concentration [IC(50)] of 20.3 +/- 1.0 mu M). We also suggest a mechanism of action for risedronate against the intraerythrocytic stage of P. falciparum and show that protein prenylation seems to be modulated directly by this drug. Risedronate inhibits the transfer of the farnesyl pyrophosphate group to parasite proteins, an effect not observed for the transfer of geranylgeranyl pyrophosphate. Our in vivo experiments further demonstrate that risedronate leads to an 88.9% inhibition of the rodent parasite Plasmodium berghei in mice on the seventh day of treatment; however, risedronate treatment did not result in a general increase of survival rates.

Effects of elevated calcium on motor and exploratory activities of rats

The effects of serum and brain calcium concentration on rat behavior were tested by maintaining animals on either distilled water (N = 60) or water containing 1% calcium gluconate (N = 60) for 3 days. Animals that were maintained on high calcium drinking water presented increased serum calcium levels (control = 10.12 ± 0.46 vs calcium treated = 11.62 ± 0.51 µg/dl). Increase of brain calcium levels was not statistically significant. In the behavioral experiments each rat was used for only one test. Rats that were maintained on high calcium drinking water showed increased open-field behavior of ambulation (20.68%) and rearing (64.57%). on the hole-board, calcium-supplemented animals showed increased head-dip (67%) and head-dipping (126%), suggesting increased ambulatory and exploratory behavior. The time of social interaction was normal in animals maintained on drinking water containing added calcium. Rats supplemented with calcium and submitted to elevated plus-maze tests showed a normal status of anxiety and elevated locomotor activity. We conclude that elevated levels of calcium enhance motor and exploratory behavior of rats without inducing other behavioral alterations. These data suggest the need for a more detailed analysis of several current proposals for the use of calcium therapy in humans, for example in altered blood pressure states, bone mineral metabolism disorders in the elderly, hypocalcemic states, and athletic activities.

Anticholinesterasic, Nematostatic and Anthelmintic Activities of Pyridinic and Pyrazinic Compounds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

ANTINOCICEPTIVE EFFECT OF AMITRAZ IN MICE AND RATS

Amitraz, a formamidine insecticide and acaricide used in veterinary practice, presents side effects related to its pharmacological activity on az-adrenergic receptors. The present study was undertaken to investigate the antinociceptive effect of amitraz in rats and mice. The tail-flick test was used to determine the duration of the antinociceptive effect of the intraperitoneal tip) administration of amitraz (1 and 2 mg/kg, 10 animals per group) in male Wistar rats weighing 180-220 g. The writhing test (using 10 ml/kg of a 0.6% acetic acid solution as a painful stimulus). was performed in 140 male Swiss mice weighing 20-30 g, divided into 14 groups that received ip injections of saline, amitraz (0.5, 1.0, 1.5, 2.0 and 4.0 mg/kg), xylazine or detomidine (1.0, 1.5, 2.0 and 4.0 mg/ kg), in order to compare the effect of amitraz to that caused by xylazine and detomidine, and to investigate the participation of alpha(2)-adrenergic receptors which were blocked by idazoxan (1 mg/kg). Amitraz induced a significant antinociceptive effect in both rats and mice. This effect is blocked in mice by idazoxan.

Short-term sustained hypoxia induces changes in the coupling of sympathetic and respiratory activities in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Coupling of respiratory and sympathetic activities in rats submitted to chronic intermittent hypoxia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of acute intermittent hypoxia on sympathetic and expiratory activities in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Acute adenosine increases cardiac vagal and reduces sympathetic efferent nerve activities in rats

Adenosine is the first drug of choice in the treatment of supraventricular arrhythmias. While the effects of adenosine on sympathetic nerve activity (SNA) have been investigated, no information is available on the effects on cardiac vagal nerve activity (VNA). We assessed in rats the responses of cardiac VNA, SNA and cardiovascular variables to intravenous bolus administration of adenosine. In 34 urethane-anaesthetized rats, cardiac VNA or cervical preganglionic sympathetic fibres were recorded together with ECG, arterial pressure and ventilation, before and after administration of three doses of adenosine (100, 500 and 1000 mu g kg-1). The effects of adenosine were also assessed in isolated perfused hearts (n= 5). Adenosine induced marked bradycardia and hypotension, associated with a significant dose-dependent increase in VNA (+204 +/- 56%, P < 0.01; +275 +/- 120%, P < 0.01; and +372 +/- 78%, P < 0.01, for the three doses, respectively; n= 7). Muscarinic blockade by atropine (5 mg kg-1, i.v.) significantly blunted the adenosine-induced bradycardia (-56.0 +/- 4.5%, P < 0.05; -86.2 +/- 10.5%, P < 0.01; and -34.3 +/- 9.7%, P < 0.01, respectively). Likewise, adenosine-induced bradycardia was markedly less in isolated heart preparations. Previous barodenervation did not modify the effects of adenosine on VNA. On the SNA side, adenosine administration was associated with a dose-dependent biphasic response, including overactivation in the first few seconds followed by a later profound SNA reduction. Earliest sympathetic activation was abolished by barodenervation, while subsequent sympathetic withdrawal was affected neither by baro- nor by chemodenervation. This is the first demonstration that acute adenosine is able to activate cardiac VNA, possibly through a central action. This increase in vagal outflow could make an important contribution to the antiarrhythmic action of this substance.

Alternative complement pathway and factor B activities in rats with altered blood levels of thyroid hormone

Evaluating the activity of the complement system under conditions of altered thyroid hormone levels might help elucidate the role of complement in triggering autoimmune processes. Here, we investigated alternative pathway (AP) activity in male Wistar rats (180 ± 10 g) after altering their thyroid hormone levels by treatment with triiodothyronine (T3), propylthiouracil (PTU) or thyroidectomy. T3 and thyroxine (T4) levels were determined by chemiluminescence assays. Hemolytic assays were performed to evaluate the lytic activity of the AP. Factor B activity was evaluated using factor B-deficient serum. An anti-human factor B antibody was used to measure factor B levels in serum by radial immunodiffusion. T3 measurements in thyroidectomized animals or animals treated with PTU demonstrated a significant reduction in hormone levels compared to control. The results showed a reduction in AP lytic activity in rats treated with increasing amounts of T3 (1, 10, or 50 µg). Factor B activity was also decreased in the sera of hyperthyroid rats treated with 1 to 50 µg T3. Additionally, treating rats with 25 µg T3 significantly increased factor B levels in their sera (P < 0.01). In contrast, increased factor B concentration and activity (32%) were observed in hypothyroid rats. We conclude that alterations in thyroid hormone levels affect the activity of the AP and factor B, which may in turn affect the roles of AP and factor B in antibody production.

Physiological time structure of the tibialis anterior motor activity during sleep in mice, rats and humans

The validation of rodent models for restless legs syndrome (Willis-Ekbom disease) and periodic limb movements during sleep requires knowledge of physiological limb motor activity during sleep in rodents. This study aimed to determine the physiological time structure of tibialis anterior activity during sleep in mice and rats, and compare it with that of healthy humans. Wild-type mice (n = 9) and rats (n = 8) were instrumented with electrodes for recording the electroencephalogram and electromyogram of neck muscles and both tibialis anterior muscles. Healthy human subjects (31 ± 1 years, n = 21) underwent overnight polysomnography. An algorithm for automatic scoring of tibialis anterior electromyogram events of mice and rats during non-rapid eye movement sleep was developed and validated. Visual scoring assisted by this algorithm had inter-rater sensitivity of 92-95% and false-positive rates of 13-19% in mice and rats. The distribution of the time intervals between consecutive tibialis anterior electromyogram events during non-rapid eye movement sleep had a single peak extending up to 10 s in mice, rats and human subjects. The tibialis anterior electromyogram events separated by intervals <10 s mainly occurred in series of two-three events, their occurrence rate in humans being lower than in mice and similar to that in rats. In conclusion, this study proposes reliable rules for scoring tibialis anterior electromyogram events during non-rapid eye movement sleep in mice and rats, demonstrating that their physiological time structure is similar to that of healthy young human subjects. These results strengthen the basis for translational rodent models of periodic limb movements during sleep and restless legs syndrome/Willis-Ekbom disease.

Hormones and mammary carcinogenesis in mice, rats, and humans: a unifying hypothesis.

An attempt has been made to put forward a unifying hypothesis explaining the role hormones play in the genesis of mammary cancers of different phenotypes and genotypes in mice, rats, and humans. Most mammary cancers in these species originate in luminal mammary epithelial cells lining the mammary ducts and alveoli. These cancers are histopathologically diverse and are classified on the basis of growth requirements as hormone-dependent or hormone-independent tumors. In most strains of mice, mammary cancers at the time of detection are largely of the hormone-independent type; in rats, almost all mammary cancers are hormone-dependent, while humans have both phenotypes. In spite of these differences, in vivo studies show that hormones (ovarian and pituitary) are essential for luminal mammary epithelial cell proliferation and also for the development of mammary cancers of both hormone-independent and hormone-dependent types. This article, based on our extensive in vivo and in vivo studies and on current literature, proposes a model to explain the central role of hormones in the genesis of all types of mammary cancers. The model attempts to address the following questions: (i) how hormones regulate luminal mammary epithelial cell proliferation, (ii) why hormones are required for the genesis of mammary cancers of all phenotypes and genotypes, including those which are always classified as hormone-independent tumors, and (iii) why the three species (mouse, rat, and human) have consistently different ratios of hormone-dependent to hormone-independent tumors.

Effects of elevated calcium on motor and exploratory activities of rats

The effects of serum and brain calcium concentration on rat behavior were tested by maintaining animals on either distilled water (N = 60) or water containing 1% calcium gluconate (N = 60) for 3 days. Animals that were maintained on high calcium drinking water presented increased serum calcium levels (control = 10.12 ± 0.46 vs calcium treated = 11.62 ± 0.51 µg/dl). Increase of brain calcium levels was not statistically significant. In the behavioral experiments each rat was used for only one test. Rats that were maintained on high calcium drinking water showed increased open-field behavior of ambulation (20.68%) and rearing (64.57%). on the hole-board, calcium-supplemented animals showed increased head-dip (67%) and head-dipping (126%), suggesting increased ambulatory and exploratory behavior. The time of social interaction was normal in animals maintained on drinking water containing added calcium. Rats supplemented with calcium and submitted to elevated plus-maze tests showed a normal status of anxiety and elevated locomotor activity. We conclude that elevated levels of calcium enhance motor and exploratory behavior of rats without inducing other behavioral alterations. These data suggest the need for a more detailed analysis of several current proposals for the use of calcium therapy in humans, for example in altered blood pressure states, bone mineral metabolism disorders in the elderly, hypocalcemic states, and athletic activities.

In vitro antileishmanial, antiplasmodial and cytotoxic activities of phenolics and triterpenoids from Baccharis dracunculifolia D. C. (Asteraceae)

Baccharis dracunculifolia (Asteraceae), the most important plant source of the Brazilian green propolis (GPE), displayed in vitro activity against Leishmania donovani. with an IC(50) value of 45 mu g/mL. while GPE presented an IC(50) value of 49 mu g/mL Among the isolated compounds of B. dracunculifolia, ursolic acid, and hautriwaic acid lactone showed IC(50) values of 3.7 mu g/mL and 7.0 mu g/mL, respectively. Uvaol, acacetin, and ermanin displayed moderate antileishmanial activity. Regarding the antiplasmodial assay against Plasmodium falciparum, BdE and GPE gave similar IC(50) values (about 20 mu g/mL), while Hautriwaic acid lactone led to an IC(50) value of 0.8 mu g/mL (D6 clone). (C) 2009 Elsevier B.V. All rights reserved.

The antitumoral, trypanocidal and antileishmanial activities of extract and alkaloids isolated from Duguetia furfuracea

The alkaloid extract and five alkaloids isolated from subterranean stem bark of Duguetia furfuracea (Annonaceae) were investigated for the following activities: antitumoral, trypanocidal and leishmanicidal. Dicentrinone showed weak cytotoxicity, but it had the strongest leishmanicidal activity IC(50) 0.01 mu M). Duguetine and duguetine beta-N-oxide caused considerable antitumoral activity in every cell lines evaluated, although duguetine was more active against trypomastigote forms (IC(50) 9.32 mu M) than other alkaloids tested. (C) 2009 Elsevier GmbH. All rights reserved.