Amphotericin B mediates killing in Cryptococcus neoformans through the induction of a strong oxidative burst

We studied the effects of Amphotericin B (AmB) on Cryptococcus neoformans using different viability methods (CFUs enumeration, XTT assay and propidium iodide permeability). After 1 h of incubation, there were no viable colonies when the cells were exposed to AmB concentrations >= 1 mg/L. In the same conditions, the cells did not become permeable to propidium iodide, a phenomenon that was not observed until 3 h of incubation. When viability was measured in parallel using XTT assay, a result consistent with the CFUs was obtained, although we also observed a paradoxical effect in which at high AmB concentrations, a higher XTT reduction was measured than at intermediate AmB concentrations. This paradoxical effect was not observed after 3 h of incubation with AmB, and lack of XTT reduction was observed at AmB concentrations higher than 1 mg/L. When stained with dihydrofluorescein, AmB induced a strong intracellular oxidative burst. Consistent with oxidative damage, AmB induced protein carbonylation. Our results indicate that in C. neoformans, Amphotericin B causes intracellular damage mediated through the production of free radicals before damage on the cell membrane, measured by propidium iodide uptake. (C) 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Efeito paradoxal do tratamento de manifestações convulsivas desencadeadas por exercício físico em uma potra - Relato de caso

Laskoski L.M., Doria R.G.S., Avila L.G., Rocha T.G., Freitas S.H. de & Lacerda Neto J.C. [Paradoxal effect of the seizures treatment caused by physical exercise in a foal - Case report]. Efeito paradoxal do tratamento de manifestacoes convulsivas desencadeadas por exercicio fisico em uma potra - Relato de caso. Revista Brasileira de Medicina Veterinaria, 33(2):95-98, 2011. Rua Presidende Wenceslau Braz, numero 670, apart. 1101. Morada do Sol, Cuiaba, 78043-508. MT, Brasil. Email: lucianelaskoski@hotmail.comNeurological disturbs, in special seizures, are rare in adult horses and are normally observed in young animals in consequence of several diseases. A foal was admitted with neurological signs characterized by seizures during exercise. A maintenance protocol with anticonvulsants was not possible to establish therefore all the drugs had aggravated the seizures even with low dosages. Restriction of physical activity was the option, leaving the animal in stall until it had reached the maturity and at this time the neurological signs had stopped.

Obstrução experimental de jejuno em eqüinos: efeito da hidrocortisona nos parâmetros clínicos e laboratoriais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Manipulation of antioxidant pathways in neonatal murine brain

To assess the role of brain antioxidant capacity in the pathogenesis of neonatal hypoxic-ischemic brain injury, we measured the activity of glutathione peroxidase (GPX) in both human-superoxide dismutase-1 (hSOD1) and human-GPX1 overexpressing transgenic (Tg) mice after neonatal hypoxia-ischemia (HI). We have previously shown that mice that overexpress the hSOD1 gene are more injured than their wild-type (WT) littermates after HI, and that H(2)O(2) accumulates in HI hSOD1-Tg hippocampus. We hypothesized that lower GPX activity is responsible for the accumulation of H(2)O(2). Therefore, increasing the activity of this enzyme through gene manipulation should be protective. We show that brains of hGPX1-Tg mice, in contrast to those of hSOD-Tg, have less injury after HI than WT littermates: hGPX1-Tg, median injury score = 8 (range, 0-24) versus WT, median injury score = 17 (range, 2-24), p < 0.01. GPX activity in hSOD1-Tg mice, 2 h and 24 h after HI, showed a delayed and bilateral decline in the cortex 24 h after HI (36.0 +/- 1.2 U/mg in naive hSOD1-Tg versus 29.1 +/- 1.7 U/mg in HI cortex and 29.2 +/- 2.0 for hypoxic cortex, p < 0.006). On the other hand, GPX activity in hGPX1-Tg after HI showed a significant increase by 24 h in the cortex ipsilateral to the injury (48.5 +/- 5.2 U/mg, compared with 37.2 +/- 1.5 U/mg in naive hGPX1-Tg cortex, p < 0.008). These findings support the hypothesis that the immature brain has limited GPX activity and is more susceptible to oxidative damage and may explain the paradoxical effect seen in ischemic neonatal brain when SOD1 is overexpressed.

Low-calcium-induced enhancement of chemical synaptic transmission from photoreceptors to horizontal cells in the vertebrate retina.

According to the classical calcium hypothesis of synaptic transmission, the release of neurotransmitter from presynaptic terminals occurs through an exocytotic process triggered by depolarization-induced presynaptic calcium influx. However, evidence has been accumulating in the last two decades indicating that, in many preparations, synaptic transmitter release can persist or even increase when calcium is omitted from the perfusing saline, leading to the notion of a "calcium-independent release" mechanism. Our study shows that the enhancement of synaptic transmission between photoreceptors and horizontal cells of the vertebrate retina induced by low-calcium media is caused by an increase of calcium influx into presynaptic terminals. This paradoxical effect is accounted for by modifications of surface potential on the photoreceptor membrane. Since lowering extracellular calcium concentration may likewise enhance calcium influx into other nerve cells, other experimental observations of "calcium-independent" release may be reaccommodated within the framework of the classical calcium hypothesis without invoking unconventional processes.

Effect of sildenafil (Viagra®) on the genital reflexes of paradoxical sleep-deprived male rats

Since there is evidence that paradoxical sleep deprivation (PSD) elicits penile erection (PE) and ejaculation (EJ), and that the erectile response of rats is mediated by nitric oxide, the present study sought to extend the latter finding by assessing the effects of sildenafil on the genital reflexes of male Wistar rats subjected to PSD. We also determined the influence of sildenafil on hormone concentrations. In the first experiment, sildenafil at doses ranging from 0.08 to 0.32 mg/kg was administered intraperitoneally to rats that had been deprived of sleep for 4 days and to home cage controls (N = 8-10/group). The frequency of PE and EJ was measured for 60 min. PSD alone induced PE in 50% of the animals; however, a single injection of sildenafil did not significantly increase the percentage of rats displaying PE compared to PSD-saline or to home cage groups. PSD alone also induced spontaneous EJ, but this response was not potentiated by sildenafil in the dose range tested. Testosterone concentrations were significantly lower in PSD rats (137 ± 22 ng/dL) than in controls (365 ± 38 ng/dL), whereas progesterone (0.9 ± 0.1 vs 5.4 ± 1 ng/mL) and plasma dopamine (103.4 ± 30 vs 262.6 ± 77 pg/mL) increased. These changes did not occur after sildenafil treatment. The data show that although sildenafil did not alter the frequency of genital reflexes, it antagonized hormonal (testosterone and progesterone) and plasma dopamine changes induced by PSD. The stimulation of the genital reflexes by sildenafil did not result in potentiating effects in PSD rats.

Late results after percutaneous closure of patent foramen ovale for secondary prevention of paradoxical embolism using the amplatzer PFO occluder without intraprocedural echocardiography: effect of device size

OBJECTIVES: We sought to assess the safety and clinical efficacy of patent foramen ovale (PFO) closure under fluoroscopic guidance only, without intraprocedural echocardiography. BACKGROUND: Percutaneous PFO closure has been shown to be safe and feasible using several devices. It is generally performed using simultaneously fluoroscopic and transesophageal or intracardiac echocardiographic guidance. Transesophageal echocardiography requires sedation or general anesthesia and intubation to avoid aspiration. Intracardiac echocardiography is costly and has inherent risks. Both lengthen the procedure. The Amplatzer PFO Occluder (AGA Medical Corporation, Golden Valley, Minnesota) can be safely implanted without echocardiographic guidance. METHODS: A total of 620 patients (51 +/- 12 years; 66% male) underwent PFO closure using the Amplatzer PFO Occluder for secondary prevention of presumed paradoxical embolism. Based on size and mobility of the PFO and the interatrial septum, an 18-mm device was used in 50 patients, a 25-mm device in 492, and a 35-mm device in 78. RESULTS: All procedures were successful, with 5 procedural complications (0.8%): 4 arteriovenous fistulae requiring elective surgical correction, and 1 transient ischemic attack. Contrast transesophageal echocardiography at 6 months showed complete closure in 91% of patients, whereas a minimal, moderate, or large residual shunt persisted in 6%, 2%, and 1%, respectively. During a mean follow-up period of 3.0 +/- 1.9 years (median: 2.6 years; total patient-years: 1,871), 5 ischemic strokes, 8 transient ischemic attacks, and no peripheral emboli were reported. Freedom from recurrent ischemic stroke, transient ischemic attack, or peripheral embolism was 99% at 1 year, 99% at 2 years, and 97% at 5 years. CONCLUSIONS: The Amplatzer PFO Occluder affords excellent safety and long-term clinical efficacy of percutaneous PFO closure without intraprocedural echocardiography.

Statins withdrawal, vascular complications, rebound effect and similitude

Hahnemann considered the secondary action of medicines to be a law of nature and reviewed the conditions under which it occurs. It is closely related to the rebound effects observed with many modern drugs. I review the evidence of the rebound effect of statins that support the similitude principle. In view of their indications in primary and secondary prevention of cardiovascular diseases, statins are widely prescribed. Besides reducing cholesterol biosynthesis, they provide vasculoprotective effects (pleiotropic effects), including improvement of endothelial function, increased nitric oxide bioavailability, antioxidant properties, inhibition of inflammatory and thrombogenic responses, stabilisation of atherosclerotic plaques, and others. Recent studies suggest that suspension of statin treatment leads to a rebound imparing of vascular function, and increasing morbidity and mortality in patients with vascular diseases. Similarly to other classes of modern palliative drugs, this rebound effect is the same as a secondary action or vital reaction described by Samuel Hahnemann, and used in homeopathy in a therapeutic sense. Homeopathy (2010) 99, 255-262.

Antidepressants, suicidality and rebound effect: evidence of similitude?

Background: Samuel Hahnemann noticed that palliative treatments for the symptoms of chronic diseases, after an initial improvement, provoked symptoms similar but stronger symptoms to those initially suppressed. He regarded this as a consequence of the vital reaction of the organism: an automatic and instinctive capacity to return to the initial health condition altered by medicines. Using this homeostatic conception of the organism as a treatment rationale, Hahnemann proposed the therapy of similarity, administering to the patients medicines capable of causing, in healthy individuals, similar symptoms to the natural disease. Based on experimental observations, he proposed that the primary action of the drug was followed by the secondary and opposite action of the organism, inaugurating homeopathic pharmacology, and alerting to the harmful consequences of palliative medicines in susceptible individuals. Such liatrogenic events can be observed in contemporary medicine, after the withdrawal of modern enantiopathic medicines, according to the study of the rebound effect or paradoxical reaction of the organism. Method. This study reviews the recent studies which describe suicidallity after the suspension or discontinuation of second generation antidepressants according to the hypothesis of the paradoxical reaction of the organism. Conclusions: Rebound and withdrawal effects, including suicidality occur with antidepressant drugs. They are relatively rare but more intense than the primary action of the drug. The probability of such effects is influenced by patient factors including age and diagnosis, and drug factors including half-life. Homeopathy (2009) 98, 114-121.

Case fatality after an acute cardiac event: the effect of smoking and alcohol consumption

The objective of this study was to use a population-based register of acute cardiac events to investigate the association between survival after an acute event and history of smoking and alcohol consumption. The population was all residents of the Lower Hunter Region of Australia aged 25 to 69 years who suffered myocardial infarction or sudden cardiac death between 1986 and 1994. Among 10,170 events, 2504 resulted in death within 28 days. After adjusting for sex, age and medical history, current smokers had a similar risk of dying after an acute cardiac event to never-smokers [odds ratio (OR)=1.10, 95% confidence interval (CI) 0.94-1.29]. People who consumed more than 8 alcoholic drinks per day on more than 2 days per week (OR=1.93, 95% CI 1.39-2.69) and former moderate to heavy drinkers (OR=4.59, 95% CI 3.65-5.76) were more likely to die than people who were nondrinkers. The results of this large community study, suggesting no effect of smoking on case fatality and an increased risk of death after an acute cardiac event for heavy drinkers and former moderate to heavy drinkers, highlight the importance of a population view of case fatality. These results can also shed some light on reasons for the paradoxical results from clinical trials. (C) 2001 Elsevier Science Inc. All rights reserved.

Effects of cocaine, methamphetamine and modafinil challenge on sleep rebound after paradoxical sleep deprivation in rats

Sleep loss is both common and critically relevant to our society and might lead to the abuse of psychostimulants such as amphetamines, cocaine and modafinil. Since psychoactive substance abuse often occurs within a scenario of sleep deficit, the purpose of this investigation was to compare the sleep patterns of rats challenged with cocaine (7 mg/kg, ip), methamphetamine (7 mg/kg, ip), or modafinil (100 mg/kg, ip) subsequent to paradoxical sleep deprivation (PSD) for 96 h. Our results show that, immediately after 96 h of PSD, rats (10 per group) that were injected with a psychostimulant presented lower percentages of paradoxical sleep compared to those injected with saline (P < 0.01). Regarding slow wave sleep (SWS), rats injected with psychostimulants after PSD presented a late rebound (on the second night subsequent to the injection) in the percentage of this phase of sleep when compared to PSD rats injected with saline (P < 0.05). In addition, the current study has produced evidence of the characteristic effect of each drug on sleep architecture. Home cage control rats injected with modafinil and methamphetamine showed a reduction in SWS compared with the saline group. Methamphetamine affected sleep patterns most, since it significantly reduced paradoxical sleep, SWS and sleep efficiency before and after PSD compared to control (P < 0.05). Cocaine was the psychostimulant causing the least changes in sleep pattern in relation to those observed after saline injection. Therefore, our results suggest that abuse of these psychostimulants in a PSD paradigm aggravates their impact on sleep patterns.

Participation of the cholinergic system in the ethanol-induced suppression of paradoxical sleep in rats

Sleep disturbance is among the many consequences of ethanol abuse in both humans and rodents. Ethanol consumption can reduce REM or paradoxical sleep (PS) in humans and rats, respectively. The first aim of this study was to develop an animal model of ethanol-induced PS suppression. This model administered intragastrically (by gavage) to male Wistar rats (3 months old, 200-250 g) 0.5 to 3.5 g/kg ethanol. The 3.5 g/kg dose of ethanol suppressed the PS stage compared with the vehicle group (distilled water) during the first 2-h interval (0-2 h; 1.3 vs 10.2; P < 0.001). The second aim of this study was to investigate the mechanisms by which ethanol suppresses PS. We examined the effects of cholinergic drug pretreatment. The cholinergic system was chosen because of the involvement of cholinergic neurotransmitters in regulating the sleep-wake cycle. A second set of animals was pretreated with 2.5, 5.0, and 10 mg/kg pilocarpine (cholinergic agonist) or atropine (cholinergic antagonist). These drugs were administered 1 h prior to ethanol (3.5 g/kg) or vehicle. Treatment with atropine prior to vehicle or ethanol produced a statistically significant decrease in PS, whereas pilocarpine had no effect on minutes of PS. Although the mechanism by which ethanol induces PS suppression is not fully understood, these data suggest that the cholinergic system is not the only system involved in this interaction.

Paradoxical effects of bovine somatotropin treatment on the ovarian follicular population and in vitro embryo production of lactating buffalo donors submitted to ovum pick-up

The aim of the present study was to evaluate the effect of bovine somatotropin (bST; 500 mg) administration on lactating buffalo donors submitted to two different ovum pick-up (OPU) and in vitro embryo production schemes with a 7 or 14 d intersession OPU interval. A total of 16 lactating buffalo cows were randomly assigned into one of four experimental groups according to the bST treatment (bST or No-bST) and the OPU intersession interval (7 or 14 d) in a 2 x 2 factorial design (16 weeks of OPU sessions). The females submitted to OPU every 14d had a larger (P < 0.001) number of ovarian follicles suitable for puncture (15.6 +/- 0.7 vs. 12.8 +/- 0.4) and an increased (P = 0.004) number of cumulus-oocyte complexes (COCs) recovered (10.0 +/- 0.5 vs. 8.5 +/- 0.3) compared to the 7 d interval group. However, a 7 or 14 d interval between OPU sessions had no effect (P = 0.34) on the number of blastocysts produced per OPU (1.0 +/- 0.1 vs. 13 +/- 0.2, respectively). In addition, bST treatment increased (P < 0.001) the number of ovarian follicles suitable for puncture (15.3 +/- 0.5 vs. 12.1 +/- 0.4) but reduced the percentage (18.9% vs. 10.9%; P = 0.009) and the number (1.4 +/- 0.2 vs. 0.8 +/- 0.1; P = 0.003) of blastocysts produced per OPU session compared with the non-bST-treated buffaloes. In conclusion, the 14d interval between OPU sessions and bST treatment efficiently increased the number of ovarian follicles suitable for puncture. However, the OPU session interval had no effect on embryo production, and bST treatment reduced the in vitro blastocyst outcomes in lactating buffalo donors.

Antiresorptive drugs (bisphosphonates), atypical fractures and rebound effect: new evidence of similitude

Background: Homeopathy is based on treatment by similitude ('like cures like') administering to sick individuals substances that cause similar symptoms in healthy individuals, employing the secondary and paradoxical action of the organism as therapeutic response. This vital or homeostatic reaction of the organism can be scientifically explained by the rebound effect of drugs, resulting in worsening of symptoms after suspension of treatment. Bisphosphonates (BPs) reduce 'typical' fractures in patients with osteoporosis, but recent studies report 'atypical' fractures of the femur after stopping the BPs, a rebound effect may be the causal mechanism. Method: Review of the literature concerning the relationship between atypical femoral fractures and antiresorptive drugs (bisphosphonates), identifying the pathogenesis of this adverse event. Results: Several studies have described multiple cases of 'atypical' low-impact subtrochanteric stress fractures or complete fractures of the femur. These fractures are often bilateral, preceded by pain in the affected thigh, may have a typical X-ray appearance, and may delayed healing. Rebound of osteoclastic activity after suspension of antiresorptive drugs is a plausible mechanism to explain this phenomenon. Conclusion: As for other classes of drugs, the rebound effect of antiresorptive drugs supports Hahnemann's similitude principle (primary action of the drugs followed by secondary and opposite action of the organism), and clarifies this 'unresolved' issue. Unfortunately, the rebound effect is little discussed among health professionals, depriving them of important knowledge ensure safe management of drugs. Homeopathy (2012) 101, 231-242.

The importance of phrenic nerve preservation and its effect on long-term postoperative lung function after pneumonectomy

OBJECTIVES The importance of phrenic nerve preservation during pneumonectomy remains controversial. We previously demonstrated that preservation of the phrenic nerve in the immediate postoperative period preserved lung function by 3-5% but little is known about its long-term effects. We, therefore, decided to investigate the effect of temporary ipsilateral cervical phrenic nerve block on dynamic lung volumes in mid- to long-term pneumonectomy patients. METHODS We investigated 14 patients after a median of 9 years post pneumonectomy (range: 1-15 years). Lung function testing (spirometry) and fluoroscopic and/or sonographic assessment of diaphragmatic motion on the pneumonectomy side were performed before and after ultrasonographic-guided ipsilateral cervical phrenic nerve block by infiltration with lidocaine. RESULTS Ipsilateral phrenic nerve block was successfully achieved in 12 patients (86%). In the remaining 2 patients, diaphragmatic motion was already paradoxical before the nerve block. We found no significant difference on dynamic lung function values (FEV1 'before' 1.39 ± 0.44 vs FEV1 'after' 1.38 ± 0.40; P = 0.81). CONCLUSIONS Induction of a temporary diaphragmatic palsy did not significantly influence dynamic lung volumes in mid- to long-term pneumonectomy patients, suggesting that preservation of the phrenic nerve is of greater importance in the immediate postoperative period after pneumonectomy.