Yellow fever virus infection in human hepatocyte cells triggers an imbalance in redox homeostasis with increased reactive oxygen species production, oxidative stress, and decreased antioxidant enzymes

Yellow fever (YF) presents a wide spectrum of severity, with clinical manifestations in humans ranging from febrile and self-limited to fatal cases. Although YF is an old disease for which an effective and safe vaccine exists, little is known about the viral- and host-specific mechanisms that contribute to liver pathology. Several studies have demonstrated that oxidative stress triggered by viral infections contributes to pathogenesis. We evaluated whether yellow fever virus (YFV), when infecting human hepatocytes cells, could trigger an imbalance in redox homeostasis, culminating in oxidative stress. YFV infection resulted in a significant increase in reactive oxygen species (ROS) levels from 2 to 4 days post infection (dpi). When measuring oxidative parameters at 4 dpi, YFV infection caused oxidative damage to lipids, proteins, and DNA, evidenced by an increase in lipid peroxidation/8-isoprostane, carbonyl protein, and 8-hydroxy-2'-deoxyguanosine, respectively. Furthermore, there was a significant reduction in the activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), in addition to a reduction in the ratio of reduced to oxidized glutathione (GSH/GSSG), indicating a pro-oxidant environment. However, no changes were observed in the enzymatic activity of the enzyme catalase (CAT) or in the gene expression of SOD isoforms (1/2/3), CAT, or GPx. Therefore, our results show that YFV infection generates an imbalance in redox homeostasis, with the overproduction of ROS and depletion of antioxidant enzymes, which induces oxidative damage to cellular constituents. Moreover, as it has been demonstrated that oxidative stress is a conspicuous event in YFV infection, therapeutic strategies based on antioxidant biopharmaceuticals may be new targets for the treatment of YF.

Exploring the antiviral potential of justicidin B and four glycosylated lignans from Phyllanthus brasiliensis against Zika virus: A promising pharmacological approach

BACKGROUND

Zika virus (ZIKV) is an emerging arbovirus that in recent years has been associated with cases of severe neurological disorders, such as microcephaly in newborns and Guillain-Barré syndrome in adults. As there is no vaccine or treatment, the search for new therapeutic targets is of great relevance. In this sense, plants are extremely rich sources for the discovery of new bioactive compounds and the species Phyllanthus brasiliensis (native to the Amazon region) remains unexplored.

PURPOSE

To investigate the potential antiviral activity of compounds isolated from P. brasiliensis leaves against ZIKV infection.

METHODS

In vitro antiviral assays were performed with justicidin B (a lignan) and four glycosylated lignans (tuberculatin, phyllanthostatin A, 5-O-β-d-glucopyranosyljusticidin B, and cleistanthin B) against ZIKV in Vero cells. MTT colorimetric assay was used to assess cell viability and plaque forming unit assay to quantify viral load. In addition, for justicidin B, tests were performed to investigate the mechanism of action (virucidal, adsorption, internalization, post-infection).

RESULTS

The isolated compounds showed potent anti-ZIKV activities and high selectivity indexes. Moreover, justicidin B, tuberculatin, and phyllanthostatin A completely reduced the viral load in at least one of the concentrations evaluated. Among them, justicidin B stood out as the main active, and further investigation revealed that justicidin B exerts its antiviral effect during post-infection stages, resulting in a remarkable 99.9 % reduction in viral load when treatment was initiated 24 h after infection.

CONCLUSION

Our findings suggest that justicidin B inhibits endosomal internalization and acidification, effectively interrupting the viral multiplication cycle. Therefore, the findings shed light on the promising potential of isolated compounds isolated from P. brasiliensis, especially justicidin B, which could contribute to the drug development and treatments for Zika virus infections.

Untargeted-based metabolomics analysis and in vitro/in silico antiviral activity of extracts from Phyllanthus brasiliensis (Aubl.) Poir

INTRODUCTION

This study describes the molecular profile and the potential antiviral activity of extracts from Phyllanthus brasiliensis, a plant widely found in the Brazilian Amazon. The research aims to shed light on the potential use of this species as a natural antiviral agent.

METHODS

The extracts were analysed using liquid chromatography-mass spectrometry (LC-MS) system, a potent analytical technique to discover drug candidates. In the meantime, in vitro antiviral assays were performed against Mayaro, Oropouche, Chikungunya, and Zika viruses. In addition, the antiviral activity of annotated compounds was predicted by in silico methods.

RESULTS

Overall, 44 compounds were annotated in this study. The results revealed that P. brasiliensis has a high content of fatty acids, flavones, flavan-3-ols, and lignans. Furthermore, in vitro assays revealed potent antiviral activity against different arboviruses, especially lignan-rich extracts against Zika virus (ZIKV), as follows: methanolic extract from bark (MEB) [effective concentration for 50% of the cells (EC50 ) = 0.80 μg/mL, selectivity index (SI) = 377.59], methanolic extract from the leaf (MEL) (EC50  = 0.84 μg/mL, SI = 297.62), and hydroalcoholic extract from the leaf (HEL) (EC50  = 1.36 μg/mL, SI = 735.29). These results were supported by interesting in silico prediction, where tuberculatin (a lignan) showed a high antiviral activity score.

CONCLUSIONS

Phyllanthus brasiliensis extracts contain metabolites that could be a new kick-off point for the discovery of candidates for antiviral drug development, with lignans becoming a promising trend for further virology research.

Virucidal antiviral activity of Maytenus quadrangulata extract against Mayaro virus: Evidence for the presence of catechins

ETHNOPHARMACOLOGICAL RELEVANCE

Mayaro virus (MAYV) is an arbovirus endemic to the Amazon region, which comprises the states of the North and Midwest region of Brazil and encompasses the largest tropical forest in the world, the Amazon Forest. The confirmation of its potential transmission by Aedes aegypti and recent cases in Brazil, mainly in large centers in the northern region, led to the classification of Mayaro fever as an emerging disease. Traditional medicine is commonly used to treat various diseases, mainly by local riverside populations. Some species of the genus Maytenus, which have similar morphologies, are popularly used to treat infections and inflammations. In this context, our research group has studied and confirmed the antiviral activity of several plant-derived compounds. However, several species of this same genus have not been studied and therefore deserve attention.

AIM OF THE STUDY

This study aimed to demonstrate the effects of ethyl acetate extracts of leaves (LAE) and branches (TAE) of Maytenus quadrangulata against MAYV.

MATERIALS AND METHODS

Mammalian cells (Vero cells) were used to evaluate the cytotoxicity of the extracts. After cell infection by MAYV and the treatment with the extracts, we evaluated the selectivity index (SI), the virucidal effect, viral adsorption and internalization, and the effect on viral gene expression. The antiviral action was confirmed by quantifying the viral genome using RT-qPCR and by analyzing the effect on virus yield in infected cells. The treatment was performed based on the effective concentration protective for 50% of the infected cells (EC₅₀).

RESULTS

The leaves (LAE; EC₅₀ 12.0 μg/mL) and branches (TAE; EC₅₀ 101.0 μg/mL) extracts showed significative selectivity against the virus, with SI values of 79.21 and 9.91, respectively, which were considered safe. Phytochemical analysis revealed that the antiviral action was associated with the presence of catechins, mainly in LAE. This extract was chosen for the subsequent studies since it reduced the viral cytopathic effect and virus production, even at high viral loads [MOI (multiplicity of infection) 1 and 5]. The effects of LAE resulted in a marked reduction in viral gene expression. The viral title was drastically reduced when LAE was added to the virus before infection or during replication stages, reducing virus production up to 5-log units compared to infected and untreated cells.

CONCLUSION

Through kinetic replication, MAYV was not detected in Vero cells treated with LAE throughout the viral cycle. The virucidal effect of LAE inactivates the viral particle and can intercept the virus at the end of the cycle when it gains the extracellular environment. Therefore, LAE is a promising source of antiviral agents.

Oropouche virus infection induces ROS production and oxidative stress in liver and spleen of mice

Oropouche virus (OROV) is the aetiological agent of Oropouche fever, the symptoms of which are common to most arboviruses, such as fever, headache, malaise, nausea and vomiting. More than half a million people have been infected with OROV since its isolation in 1955. Although Oropouche fever is classified as a neglected and emerging disease, to date, there are no antiviral drugs or vaccines available against the infection and little is known about its pathogenicity. Therefore, it is essential to elucidate the possible mechanisms involved in its pathogenesis. Since oxidative stress plays a pivotal role in the progression of various viral diseases, in this study, redox homeostasis in the target organs of OROV infection was evaluated using an animal model. Infected BALB/c mice exhibited reduced weight gain, splenomegaly, leukopenia, thrombocytopenia, anaemia, development of anti-OROV neutralizing antibodies, increased liver transaminases, and serum levels of pro-inflammatory cytokines tumour necrosis factor (TNF-α) and interferon-γ (IFN-γ). The OROV genome and infectious particles were detected in the liver and spleen of infected animals, with liver inflammation and an increase in the number and total area of lymphoid nodules in the spleen. In relation to redox homeostasis in the liver and spleen, infection led to an increase in reactive oxygen species (ROS) levels, increased oxidative stress biomarkers malondialdehyde (MDA) and carbonyl protein, and decreased activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Taken together, these results help elucidate some important aspects of OROV infection that may contribute to the pathogenesis of Oropouche.

Netzahualcoyonol from Salacia multiflora (Lam.) DC. (Celastraceae) roots as a bioactive compound against gram-positive pathogens

The expression of virulence factors, such as biofilm formation, in association with the acquisition of resistance to multiple drugs, has evidenced the need for new and effective antimicrobial agents against Staphylococcus aureus. The evaluation of the pharmacological properties of plant-derived compounds is a promising alternative to the development of new antimicrobials. In this study, we aimed to evaluate the antibacterial, antibiofilm, and the synergistic and cytotoxic effects of netzahualcoyonol isolated from Salacia multiflora (Lam.) DC. roots. Netzahualcoyonol presented bacteriostatic (1.56-25.0 µg/mL) and bactericidal (25.0-400.0 µg/mL) effects against Gram-positive bacteria, disrupted the biofilm of S. aureus, and presented a synergistic effect after its combination with β-lactams and aminoglycosides. The low cytotoxicity of netzahualcoyonol (Selectivity Index (SI) for S. aureus (2.56), S. saprophyticus (20.56), and Bacillus subtilis (1.28)) suggests a good security profile. Taken together, these results show that netzahualcoyonol is promising for the development of a new effective antibacterial agent.

Antioxidant and antiviral activity of fullerol against Zika virus

Neglected for years, Zika virus (ZIKV) has become one of the most relevant arboviruses in current public health. The recent Zika fever epidemic in the Americas generated a worldwide alert due to the association with diseases such as Guillain-Barré syndrome and congenital syndromes. Among the pathogenesis of ZIKV, recent studies suggest that oxidative stress plays an important role during infection and that compounds capable of modulating oxidative stress are promising as therapeutics. Furthermore, so far there are no specific and efficient antiviral drug or vaccine available against ZIKV. Thus, fullerol was evaluated in the context of infection by ZIKV, since it is a carbon nanomaterial known for its potent antioxidant action. In this study, fullerol did not alter cell viability at the concentrations tested, proving to be inert, beyond to presenting high antioxidant power at low concentrations. ZIKV infection of human glioblastoma increased the production of reactive oxygen species by 60% and modulated the Nrf-2 pathway activity negatively. After treatment with fullerol, both conditions were restored to baseline levels. Additionally, fullerol was able to reduce viral production by up to 90%. Therefore, our results suggest that fullerol as a promising candidate in the control of ZIKV infections, presenting both antioxidant and antiviral action.

Hepatoprotective, antioxidant, anti-inflammatory, and antiviral activities of silymarin against mayaro virus infection

Infection caused by Mayaro virus (MAYV) is responsible for causing acute nonspecific fever, in which the majority of patients develop incapacitating and persistent arthritis/arthralgia. Mayaro fever is a neglected and underreported disease without treatment or vaccine, which has gained attention in recent years after the competence of Aedes aegypti to transmit MAYV was observed in the laboratory, coupled with the fact that cases are being increasingly reported outside of endemic forest areas, calling attention to the potential of an urban cycle arising in the near future. Thus, to mitigate the lack of information about the pathological aspects of MAYV, we previously described the involvement of oxidative stress in MAYV infection in cultured cells and in a non-lethal mouse model. Additionally, we showed that silymarin, a natural compound, attenuated MAYV-induced oxidative stress and inhibited MAYV replication in cells. The antioxidant and anti-MAYV effects prompted us to determine whether silymarin could also reduce oxidative stress and MAYV replication after infection in an immunocompetent animal model. We show that infected mice exhibited reduced weight gain, hepatomegaly, splenomegaly, anaemia, thrombocytopenia, leukopenia, increased liver transaminases, increased pro-inflammatory cytokines and liver inflammation, increased oxidative damage biomarkers, and reduced antioxidant enzyme activity. However, in animals infected and treated with silymarin, all these parameters were reversed or significantly improved, and the detection of viral load in the liver, spleen, brain, thigh muscle, and footpad was significantly reduced. This work reinforces the potent hepatoprotective, antioxidant, anti-inflammatory, and antiviral effects of silymarin against MAYV infection, demonstrating its potential against Mayaro fever disease.

Pristimerin isolated from Salacia crassifolia (Mart. Ex. Schult.) G. Don. (Celastraceae) roots as a potential antibacterial agent against Staphylococcus aureus

ETHNOPHARMACOLOGICAL RELEVANCE

Pristimerin is a triterpenoid considered the main component of Salacia crassifolia extracts. This terpene has shown promising antitumor, anti-inflammatory, and antimicrobial effects. Likewise, S. crassifolia has been used in traditional medicine to treat cancer and as an antimicrobial and anti-inflammatory agent.

AIM OF THE STUDY

This study aimed to evaluate the antibacterial activity of the hexane extract of Salacia crassifolia roots (HER) and its isolate, pristimerin, against pathogenic bacteria.

MATERIALS AND METHODS

First, we evaluated the spectrum of action of HER and pristimerin by the determination of the minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC). Subsequently, we analyzed the time-kill curve of these plant-derived compounds against Staphylococcus aureus. Then, we examined their mode of action by three different assays: the crystal violet methodology, the release of intracellular material, and transmission electron microscopy methods (TEM). Finally, we evaluated the effect of HER and pristimerin on the pre-formed biofilm of S. aureus by the crystal violet assay, the synergistic effect by the checkerboard method, the cytotoxicity against Vero cells, and the in silico activity using the online software PASS.

RESULTS

HER and pristimerin presented a narrow spectrum of action against Gram-positive bacteria (MIC 0.195-25 μg/mL), and their primary mode of action is the alteration of membrane permeability of S. aureus. Our results show that the compounds disrupted the pre-formed biofilm of S. aureus in a dose-dependent manner. Furthermore, HER and pristimerin presented a significant synergic effect after the combination with well-known antibiotics, which was associated with the ability of these phytomedicines to change membrane permeability. Regarding the cytotoxic effect, the selective index (SI) of HER ranged from 0.37 to 11.86, and the SI of pristimerin varied from 0.24 to 30.87, according to the bacteria tested.

CONCLUSIONS

Overall, HER and pristimerin showed a promising antibacterial effect in vitro through the alteration of membrane permeability of S. aureus.

Mayaro Virus Induction of Oxidative Stress is Associated With Liver Pathology in a Non-Lethal Mouse Model

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3-4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds.

Bauhinia holophylla (Bong.) Steud. leaves-derived extracts as potent anti-dengue serotype 2

Dengue virus (DENV) is the most prevalent mosquito-borne viral pathogen and made the disease a major health concern worldwide. However, specific antiviral drugs against this arbovirose or vaccines are not yet available for treatment or prevention. Thus, here we aimed to study the antiviral activity of hydroethanolic extract, fraction ethyl acetate and subfractions of the leaves of Bauhinia holophylla (Fabaceae:Cercideae), a native plant of the Brazilian Cerrado, against DENV-2 by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method in mammalian cells culture. As results, the hydroethanolic extract showed the most potent effect, with an inhibitory concentration (IC₅₀) of 3.2 μg mL^-1 and selectivity index (SI) of 27.6, approximately 16-times higher anti-DENV-2 activity than of the ribavirin (IC₅₀ 52.8 μg mL^-1). Our results showed in this study appointed that B. holophylla has a promising anti-dengue activity, which was associated mainly with the presence of flavonoids.

Virucidal activity of proanthocyanidin against Mayaro virus

Mayaro virus (MAYV) is a sublethal arbovirus transmitted by mosquitoes with possible installation of an urban cycle in the Americas. Its infection causes disabling arthralgia, and still, there is no vaccine or treatment to it. We recently investigated nearly 600 compounds by molecular docking and identified epicatechin as a potent antiviral against MAYV. The root extract of Maytenus imbricata showed anti-MAYV activity and two isolated compounds from this plant were also evaluated in vitro. Proanthocyanidin (PAC), a dimer containing epicatechin, showed an effective concentration for 50% of the cells infected by MAYV (EC₅₀) of 37.9 ± 2.4 μM and a selectivity index (SI) above 40. PAC showed significant virucidal activity, inhibiting 100% of the virus proliferation (7 log units), and caused moderate effect during adsorption and virus internalization stage. However, PAC was unable to block the infection when only the cells were pretreated. It was observed a reduction in virus yields when adding PAC at different moments after infection. The set of results indicates that PAC binds to viral and non-cellular elements and may inactivate the MAYV. The inactivation occurs before infection or when the virus reaches the extracellular environment from the 2nd cycle of infection that could block its progression cell-to-cell or to tissues not yet infected.

Antiviral activity of silymarin against Mayaro virus and protective effect in virus-induced oxidative stress

Mayaro virus (MAYV) is a neglected arbovirus belonging to the family Togaviridae. Its infection leads to Mayaro fever, with clinical manifestations such as fever, myalgia, headache, rash, arthralgia, vomiting, and diarrhea. The most prominent complaint from infected person is the long-lasting arthritis/arthralgia. The treatment for Mayaro fever is mainly symptom-based and there are no vaccines or antiviral drugs currently available, thus, natural products with anti-MAYV activity may provide a potential alternative. Recent evidences suggest that oxidative stress plays an important role in MAYV infection and compounds capable of modulating oxidative stress could represent a novel therapeutic approach in modulating MAYV-associated oxidative cellular damage. Silymarin is a complex extracted of Silybum marianum, or milk thistle, and its major active compound is silybin, which has a remarkable biological effect. Its antioxidant and antiviral effects, including its antiviral activity against the Chikungunya virus (CHIKV), prompted us to think whether silymarin could also reduce the replication of the MAYV and restore the pro-oxidant/antioxidant balance in the context of MAYV infection, leading to reduced cellular oxidative stress. We assessed the antiviral activity and protective effect of silymarin against oxidative stress in MAYV-infected HepG2 cells. Cytopathic effect inhibition, viral replication, and plaque reduction assays were used to determine the anti-MAYV activity of silymarin. Additionally, we determined whether silymarin could reduce MAYV-induced oxidative cell damage. Briefly, silymarin exhibited potent antiviral activity against MAYV and reduced MAYV-induced ROS formation and levels of malondialdehyde (MDA) and carbonyl protein, which are biomarkers of oxidative stress. In conclusion, the ability of silymarin to inhibit MAYV replication and attenuate MAYV-induce oxidative stress warrants further investigation of this compound as a novel therapeutic approach to Mayaro fever disease.

A critical period for omega-3 nutritional supplementation in the development of the rodent visual system

Retinocollicular connections form precise topographical maps that are normally completed through the selective elimination of misplaced axons and the stabilization of topographically ordered axon terminals during early development. Omega-3 fatty acids, acquired exclusively through the diet, and its main metabolite, docosahexaenoic acid (DHA), are involved in brain development and synaptic maturation. We have previously shown that the nutritional restriction of omega-3/DHA results in abnormal retinocollicular topographical fine-tuning. Therefore, we studied the role of omega-3 fatty acids nutritional supplementation and the developmental time windows during which this postnatal supplementation would restore normal topographical maps in the visual system. Female rats and their litters were chronically fed with either control (soy oil) or restricted omega-3 (coconut oil) diets. Fish oil supplementation was introduced between either postnatal day (PND) 7-13, PND7-28 or PND21-42. At PND13, PND28 or PND42, animals received an anterograde eye injection of a neuronal tracer to visualize retinocollicular axons. Confirming previous observations we found that an omega-3/DHA deficiency resulted in an abnormally high innervation density of retinal axons at the visual layers of the superior colliculus (SC). Although a short-term fish oil supplementation between PND7-13 could not restore normal retinocollicular topography, an extended treatment between PND7-28 completely recovered normal innervation densities of retinotectal axons. However, a late onset supplementation protocol, between PND28-42, was no longer effective in the restoration of the abnormal topographical pattern induced by an early omega-3 nutritional malnutrition. The results suggest a critical period for omega3/DHA dietary intake for the proper development of visual topographical maps.

Changes in a nanoparticle's spectroscopic signal mediated by the local environment

Using a first-principles theoretical model the adsorption of a methyl radical on different sized silver nanoparticles is compared to the adsorption of the same radical on model surfaces. Calculations of our structural, dynamical and electronic properties indicated that small changes in the local environment will lead to small changes in infrared (IR) wavenumbers, but in dramatic changes in the IR signal. Our calculations indicate the lower the adsorption site coordination, the higher is the signal strength, suggesting that small changes in the electronic charge distribution will result in bigger changes in the polarizability and hence in the spectroscopic signal intensity. This effect explains, among others, the signal magnification observed for nanoparticles in surface enhanced Raman spectroscopic (SERS) experiments.

Size effects on silver nanoparticles' properties

In this work a systematic study of the dependence of the structural, electronic, and vibrational properties on nanoparticle size is performed. Based on our total energy calculations we identified three characteristic regimes associated with the nanoparticle's dimensions: (i) below 1.5 nm (100 atoms) where remarkable molecular aspects are observed; (ii) between 1.5 and 2.0 nm (100 and 300 atoms) where the molecular behavior is influenced by the inner core crystal properties; and (iii) above 2.0 nm (more than 300 atoms) where the crystal properties are preponderant. In all considered regimes the nanoparticle's surface modulates its properties. This modulation decreases with the increasing of the nanoparticle's size.

Semiconductor nanoparticle modeling via density functional theory

In this work, a 2.0 nm nanoparticle (low limit synthesized system) is compared to possible simplified models: passivated clusters, small (1.3 nm) nanoparticles and sets of plane surfaces. Our density functional theory results suggest that even when geometric aspects are properly described by the simplifications considered, electronic properties might be very different, especially when edge atoms are not properly taken into account in the nanoparticle's modeling. In addition, we propose a protocol that might help future theoretical descriptions of nanoparticles.

Furan interaction with the Si(001)-(2 × 2) surface: structural, energetics, and vibrational spectra from first-principles

In this work we employ the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory, to investigate the adsorption process of furan on the silicon (001) surface. A direct comparison of different adsorption structures with x-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS), high resolution electron energy loss spectroscopy (HREELS), near edge x-ray absorption fine structure (NEXAFS), and high resolution spectroscopy experimental data allows us to identify the [4+2 ] cycloaddition reaction as the most probable adsorbate. In addition, theoretical scanning tunnelling microscopy (STM) images are presented, with a view to contributing to further experimental investigations.

Maleic anhydride adsorption on silicon (001)

The adsorption of maleic anhydride on the Si(001) surface has been investigated using the first-principles pseudopotential formalism. Our total-energy calculations suggest that maleic anhydride (C2H2-C2O3) adsorbs preferentially through a [2+2] cycloaddition of the C=C bond ([2+2]) with an adsorption energy of around 42 kcal/mol. Besides the [2+2] configuration we have also considered other possible coverages and adsorption models, including the adsorption on inter-row and intrarow dimer sites. Based on the analysis of the relative stability of different adsorption models, we propose the formation of mixed domains, containing the [2+2] unit and an interdimer unit. The comparison of our calculated electronic band structure, vibrational modes, and scanning tunneling microscopy images for the [2+2] and the favored interdimer adsorbed structures corroborate our proposed mixed domain model.

Effects of fish oil on the central nervous system: a new potential antidepressant?

In the last 100 years major depression has increased worldwide. In this study we provided coconut fat (CF, rich in saturated fatty acids) or fish oil (FO, rich in n-3 polyunsaturated fatty acids) to female rats throughout pregnancy and lactation and then to their offspring post-weaning and examined lipid brain profile and the possible effect of FO as antidepressant agent in the offspring in adulthood (F1). Rats were submitted to forced swimming test, elevated plus maze, Morris water maze and open field. Peroxidation rate in the cerebral cortex and hippocampus were measured. Docosahexaenoic acid (DHA) concentration in dam's milk, eicosapentaenoic acid (EPA) and DHA concentration in hippocampus and cerebral cortex from F1 rats FO supplemented increased significantly when compared to control (C) and CF rats. Arachidonic acid/EPA ratio in the cerebral cortex and hippocampus decreased in rats submitted to forced swimming test. Peroxidation rate were not different between the groups. Immobility time in the forced swimming test in FO group was reduced (p < 0.01) when compared to C and CF rats. We conclude that lifelong intake of FO was able to induce an antidepressant effect with EPA and DHA concentration increased in the cerebral cortex and hippocampus.

[Cerebral vasculitis and Basedow-Graves disease: report of two cases]

OBJECTIVE

To report two cases of patients with cerebral vasculitis and Basedow-Graves disease.

CASE REPORT

Two young female patients presented at emergency with acute neurological picture of hemiparesis and speech distress. The first patient, 22 year-old, has been on clinical treatment for hyperthyroidism for one month. On clinical examination she had an elevated cardiac rate, bilateral exophthalmia and a diffuse goiter. On neurological examination we could observe a mild dysarthria and left hemiparesis. The second patient was a 15 year-old girl, who presented sudden conscious loss, aphasia and right hemiparesis.

RESULTS

CT scan and MRI showed areas of cerebral infarcts. Angiographic study showed multiple vascular stenosis similar to an arteritic angiographic pattern. Extensive medical and laboratorial workout disclosed no other risk factor for stroke or for nervous system vasculitis. The antimicrosomal and antithyreoglobulin antibodies were positive and thyroidian hormones confirmed hyperthyroidism.

CONCLUSION

The concurrence of cerebral arteritis and Basedow-Graves' disease suggest a possible pathogenic link between Graves' disease and specific cerebral vascular disorders, possibly through a common autoimmune mechanism.

[Cerebrovascular disease and neurocysticercosis]

We report three cases of stroke secondary to neurocysticercosis. The first one is a 36 years old man with bilateral middle cerebral artery occlusions who had presented acute right hemiparesia and aphasia. MRI demonstrated several enhancing subarachnoid cysts surrounding the occluded vessels, a right parietal racemose cyst and a left temporal large infarction area. Angiographic study showed total occlusion of left middle cerebral artery and a subtotal occlusion of right middle cerebral artery. The second one is a 42 years old man with vasculitis of small cortical vessels who presented with headache, seizures and focal neurological deficit. CT scan demonstrated several calcifications and a left temporal infarction area. Cerebral angiographic study was normal. The third case was a woman, 53 years old, with a past history of six stroke events and an actual behavior disturbance and seizures. MRI demonstrated several cortical and subcortical infarction areas and cisternal cysts. Angiographic study showed diffuse arteritis of basilar and carotid arterial system. In all three cases CSF study showed linfomonocitic pleocytosis and positive ELISA for cysticercosis.

Ricinine-elicited seizures. A novel chemical model of convulsive seizures

The present investigation introduces ricinine-elicited seizures as a novel chemical model of convulsive seizure. Ricinine, a neutral alkaloid obtained from the plant Ricinus communis, induces seizures when administered to mice at doses higher than 20 mg/kg. Animals presenting seizures showed a marked preconvulsive phase followed by short duration hind limb myoclonus, respiratory spasms, and death. The lethal nature of ricinine seizures is also pointed out as a good model to study the events causing death in clonic seizures, particularly those related to respiratory spasms, which are also observed in some types of human epilepsy. The behavioral signs of ricinine-elicited seizures are accompanied by electrographic alterations more evident during the preconvulsive phase in the cerebral cortex and more intense during the ictal phase both in the cortex and in the hippocampus. The ricinine-elicited seizures may be inhibited by diazepam but not by phenobarbital, phenytoin, or ethosuximide. Micromolar concentrations of ricinine cause a small decrease in the binding of [3H]-flunitrazepam to cerebral cortex membranes, but do not alter the binding of other radioligands to AMPA, 5-HT(1A), muscarinic, and alpha(1)-adrenergic receptors. Although ricinine presents a cyanide radical, only higher doses of ricinine (4 mM) caused a small impairment of mitochondrial respiration. These results suggest that the mechanism of action of ricinine probably involves the benzodiazepine site in the GABA(A) receptor. This may represent a new mechanism of drug-elicited seizures that may contribute to a better understanding of epilepsy and to new therapeutic approaches to this disease.

Pharmacological evaluation of ricinine, a central nervous system stimulant isolated from Ricinus communis

The extract of the pericarp of castor bean (Ricinus communis) showed some typical central nervous system stimulant effects when administered to mice. The animals became exophthalmic, presented tremors and clonic seizures and died a few minutes after receiving larger doses of the extract. At lower doses the extract improved memory consolidation and showed some neuroleptic-like properties, such as a decrease in exploratory behavior and catalepsy. The memory-improving effect and the seizure-eliciting properties of the extract were also observed with the administration of ricinine, a neutral alkaloid isolated from the extract. However, the neuroleptic-like properties of the extract were not observed with ricinine. As the therapeutic index of ricinine is of the order of 200, the compound may be considered as a promising cognition-enhancing drug that may be used for the treatment of human amnesias.

[Magnetic resonance in HTL-I associated myelopathy. Leukoencephalopathy and spinal cord atrophy]

Cerebral white matter lesions and spinal cord atrophy have been frequently reported in patients with HTLV-I associated myelopathy (HAM). The exact frequency and the clinical relevance of these findings still remain to be elucidated. Twenty-nine patients with HAM were studied by magnetic resonance imaging of the brain and spine. Cerebral white matter lesions equal or over 3 mm in diameter were considered abnormal. The spinal cord size was evaluated using an index we have called "spinal cord index". The radiological findings were correlated to the clinical features of the myelopathy. Cerebral white matter lesions occurred in 52% of the patients, and spinal cord atrophy in 74%. There was no significant correlation between these abnormalities and the clinical features studied. These findings suggest that the resonance imaging is a useful method for detection of cerebral and spinal cord abnormalities in HAM patients. The absence of correlation between cerebral white matter lesions and either patient age or risk factors for cardiovascular disease suggests a possible association between the leukoencephalopathy and the infection.

[Actinomycosis of the central nervous system: a rare complication of cervicofacial actinomycosis]

Central nervous system actinomycosis is a rare but treatable chronic suppurative bacterial infection. The case of a young immunocompetent male with actinomycosis of the CNS is presented. The abscess originated from a primary cervico-facial infection and was located in the left parasellar region. After excision of the mass, that showed Actinomyces colonies, the patient was treated with intravenous Penicillin for 42 days followed by oral administration of the drug for 30 days. After surgery the patient was left with mild sequelae that had improved by the last follow-up, 7 months later. A new CT scan at that time revealed no residual disease or recurrence. The early diagnosis of cerebral actinomycosis relies essentially on a clinical suspicion. Hence it is imperative to be aware of the natural history of this infection and its various modes of presentation.