Reconciling spectroscopy with dynamics in global potential energy surfaces: The case of the astrophysically relevant SiC2.

SiC2 is a fascinating molecule due to its unusual bonding and astrophysical importance. In this work, we report the first global potential energy surface (PES) for ground-state SiC2 using the combined-hyperbolic-inverse-power-representation method and accurate ab initio energies. The calibration grid data are obtained via a general dual-level protocol developed afresh herein that entails both coupled-cluster and multi-reference configuration interaction energies jointly extrapolated to the complete basis set limit. Such an approach is specially devised to recover much of the spectroscopy from the PES, while still permitting a proper fragmentation of the system to allow for reaction dynamics studies. Besides describing accurately the valence strongly bound region that includes both the cyclic global minimum and isomerization barriers, the final analytic PES form is shown to properly reproduce dissociation energies, diatomic potentials, and long-range interactions at all asymptotic channels, in addition to naturally reflect the correct permutational symmetry of the potential. Bound vibrational state calculations have been carried out, unveiling an excellent match of the available experimental data on c-SiC2(A11). To further exploit the global nature of the PES, exploratory quasi-classical trajectory calculations for the endothermic C2 + Si → SiC + C reaction are also performed, yielding thermalized rate coefficients for temperatures up to 5000 K. The results hint for the prominence of this reaction in the innermost layers of the circumstellar envelopes around carbon-rich stars, hence conceivably playing therein a key contribution to the gas-phase formation of SiC, and eventually, solid SiC dust.

High-level ab initio quartic force fields and spectroscopic characterization of C2N.

While it is now well established that large carbon chain species and radiative electron attachment (REA) are key ingredients triggering interstellar anion chemistry, the role played by smaller molecular anions, for which REA appears to be an unlikely formation pathway, is as yet elusive. Advancing this research undoubtedly requires the knowledge (and modeling) of their astronomical abundances which, for the case of C2N-, is largely hindered by a lack of accurate spectroscopic signatures. In this work, we provide such data for both ground -CCN-(3Σ-) and low-lying c-CNC-(1A1) isomers and their singly-substituted isotopologues by means of state-of-the-art rovibrational quantum chemical techniques. Their quartic force fields are herein calibrated using a high-level composite energy scheme that accounts for extrapolations to both one-particle and (approximate) -particle basis set limits, in addition to relativistic effects, with the final forms being subsequently subject to nuclear motion calculations. Besides standard spectroscopic attributes, the full set of computed properties includes fine and hyperfine interaction constants and can be readily introduced as guesses in conventional experimental data reduction analyses through effective Hamiltonians. On the basis of benchmark calculations performed anew for a minimal test set of prototypical triatomics and limited (low-resolution) experimental data for -CCN-(3Σ-), the target accuracies are determined to be better than 0.1% of experiment for rotational constants and 0.3% for vibrational fundamentals. Apart from laboratory investigations, the results here presented are expected to also prompt future astronomical surveys on C2N-. To this end and using the theoretically-predicted spectroscopic constants, the rotational spectra of both -CCN-(3Σ-) and c-CNC-(1A1) are derived and their likely detectability in the interstellar medium is further explored in connection with working frequency ranges of powerful astronomical facilities. Our best theoretical estimate places c-CNC-(1A1) at about 15.3 kcal mol-1 above the ground-state -CCN-(3Σ-) species.

Type I interferon receptors and interferon-τ-stimulated genes in peripheral blood mononuclear cells and polymorphonuclear leucocytes during early pregnancy in beef heifers.

This study characterised the expression of interferon (IFN)-τ-stimulated genes (ISGs) and Type I IFN receptors in circulating polymorphonuclear cells (PMNs) of beef heifers and compared it with expression in peripheral blood mononuclear cells (PBMCs) up to Day 20 of gestation. Nelore heifers (n=26) were subjected to fixed-time AI (FTAI) on Day 0. PMNs and PBMCs were isolated on Days 0, 10, 14, 16, 18 and 20 after FTAI. The abundance of target transcripts (ubiquitin-like protein (ISG15), 2'-5'-oligoadenylate synthetase 1 (OAS1), myxovirus resistance 1 (MX1), myxovirus resistance 2 (MX2), IFN receptor I (IFNAR1) and IFN receptor 2 (IFNAR2)) was determined using real-time quantitative polymerase chain reaction and compared between pregnant (n=8) and non-pregnant (n=9) females. In both PBMCs and PMNs, ISG15 and OAS1 expression was greater in pregnant than non-pregnant heifers on Days 18 and 20. There were no significant differences in the expression of ISGs between PBMCs and PMNs. A time effect on expression was found for IFNAR1 in PBMCs and IFNAR2 in PMNs, with decreased expression of both genes on Days 18 and 20. When the expression of these genes was compared between cell types only in pregnant heifers, IFNAR2 expression in PMNs had an earlier decrease when compared to its expression in PBMCs, starting from Day 18. In conclusion, PMNs do not respond earlier to the conceptus stimulus, and ISG15 and OAS1 expression in both PMNs and PBMCs can be used as a suitable marker for pregnancy diagnosis on Days 18 and 20. In addition, gestational status did not affect IFNAR1 and IFNAR2 expression, but IFNAR2 showed a distinct response between PMNs and PBMCs of pregnant heifers.

Is the profile of transcripts altered in the eutopic endometrium of infertile women with endometriosis during the implantation window?

STUDY QUESTION: Compared to healthy women, is the profile of transcripts altered in the eutopic endometrium of infertile women with endometriosis during the implantation window (IW)? SUMMARY ANSWER: The eutopic endometrium of infertile women with endometriosis seems to be transcriptionally similar to the endometrium of infertile and fertile controls (FC) during the IW. WHAT IS KNOWN ALREADY: Endometriosis is a disease related to infertility; nevertheless, little is known regarding the ethiopathogenic mechanisms underlying this association. Some studies evaluating the eutopic endometrium of endometriosis patients suggest there is an endometrial factor involved in the disease-related infertility. However, no study to date has evaluated the endometrial transcriptome (mRNA and miRNA) by next generation sequencing (NGS), comparing patients with endometriosis as the exclusive infertility factor (END) to infertile controls (IC; male and/or tubal factor) and FC. STUDY DESIGN, SIZE, DURATION: From November 2011 to November 2015 we performed a case-control study, where 17 endometrial samples (six END, six IC, five FC) were collected during the IW. PARTICIPANTS/MATERIALS, SETTING, METHODS: All endometrial samples had the RNA extracted. Two libraries were prepared for each one (mRNA and miRNA), which were sequenced, respectively, at HISEQ 2500 (RNA-Seq) and MiSeq System (miRNA-Seq), Illumina. The normalization and differential expression were conducted in statistical R environment using DESeq2 package. qPCR was used for data validation, which were analyzed by Kruskal-Wallis test and Dunn posttest (P < 0.05). MAIN RESULTS AND THE ROLE OF CHANCE: RNA-Seq revealed no differentially expressed genes (DEG) among END, IC and FC groups. miRNA-Seq revealed three differentially expressed miRNAs (has-27a-5p, has-miR-150-5p, has-miR-504-5p) in END group compared to FC group. However, none of the miRNAs identified in the sequencing was validated by qPCR. LIMITATIONS, REASONS FOR CAUTION: The main limitation of this study was the small sample size evaluated as a result of the restrictive eligibility criteria adopted, limiting the generalization of the results obtained here. On the other hand, strict eligibility criteria, which eliminated factors potentially related to impaired endometrial receptivity, were required to increase the study's internal validity. WIDER IMPLICATIONS OF THE FINDINGS: This study brings new perspectives on the mechanisms involved in endometriosis-related infertility. The present findings suggest the eutopic endometrium of infertile women with endometriosis, without considering the disease's stage, is transcriptionally similar to controls during the IW, possibly not affecting receptivity. Further studies are needed to evaluate endometrial alterations related to endometriosis' stages. STUDY FUNDING/COMPETING INTEREST(S): This study received financial support from the Sao Paulo Research Foundation (FAPESP-Fundação de Amparo à Pesquisa do Estado de São Paulo; fellowship 2011/17614-6, MGB) and from the National Council for Scientific and Technological Development (CNPq-Conselho Nacional de Desenvolvimento Científico e Tecnológico; INCT-National Institutes of Hormones and Woman's Health, grant 471 943/2012-6, 309 397/2016-2, PAN; fellowship 140 137/2015-7, MGB). The authors have no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

Exposure of humans to the zoonotic nematode Dirofilaria immitis in Northern Portugal.

Dirofilariosis caused by Dirofilaria immitis (heartworm) is a zoonosis, considered an endemic disease of dogs and cats in several countries of Western Europe, including Portugal. This study assesses the levels of D. immitis exposure in humans from Northern Portugal, to which end, 668 inhabitants of several districts belonging to two different climate areas (Csa: Bragança, Vila Real and Csb: Aveiro, Braga, Porto, Viseu) were tested for anti-D. immitis and anti-Wolbachia surface proteins (WSP) antibodies. The overall prevalence of seropositivity to both anti-D. immitis and WSP antibodies was 6.1%, which demonstrated the risk of infection with D. immitis in humans living in Northern Portugal. This study, carried out in a Western European country, contributes to the characterisation of the risk of infection with D. immitis among human population in this region of the continent. From a One Health point of view, the results of the current work also support the close relationship between dogs and people as a risk factor for human infection.

A global CHIPR potential energy surface for ground-state C3H and exploratory dynamics studies of reaction C2 + CH → C3 + H.

A full-dimensional global potential-energy surface (PES) is first reported for ground-state doublet C3H using the combined-hyperbolic-inverse-power-representation (CHIPR) method and accurate ab initio energies extrapolated to the complete basis set limit. The PES is based on a many-body expansion-type development where the two-body and three-body energy terms are from our previously reported analytic potentials for C2H(2A') and C3(1A',3A'), while the effective four-body one is calibrated using an extension of the CHIPR formalism for tetratomics. The final form is shown to accurately reproduce all known stationary structures of the PES, some of which are unreported thus far, and their interconversion pathways. Moreover, it warrants by built-in construction the appropriate permutational symmetry and describes in a physically reasonable manner all long-range features and the correct asymptotic behavior at dissociation. Exploratory quasi-classical trajectory calculations for the reaction C2 + CH → C3 + H are also performed, yielding thermalized rate coefficients for temperatures up to 4000 K.

Difficulties and Virtues in Assessing the Potential Energy Surfaces of Carbon Clusters via DMBE Theory: Stationary Points of Cκ (κ = 2-10) at the Focal Point.

The previously reported potential energy surfaces (PESs) of ground-state singlet C3 and triplet C4 are here utilized as input for the construction of approximate cluster expansions for larger Cκ (κ = 5-10) species. Relying primarily on the double many-body expansion (DMBE) approach, global potentials are obtained by summing the total interaction energies of all atomic subclusters up to four-body terms. The notable capability of the final forms in predicting good estimates of the linear global minima and their thermochemical/structural properties may provide important insights into the structure-determining nature of the (2 + 3 + 4) terms. The main difficulties and virtues in assessing Cκ's via DMBE theory are analyzed and new prospects given for the construction of global reliable PESs for the target species.

Accurate CHIPR Potential Energy Surface for the Lowest Triplet State of C3.

We report the first global ab initio-based potential energy surface (PES) for ground-state triplet C3(3A') based on accurate energies extrapolated to the complete basis set (CBS) limit, and using the combined-hyperbolic-inverse-power-representation method for the analytical modeling. By relying on a cost-effective CBS(D,T) protocol, we ensure that the final form reproduces all topographical features of the PES, including its cyclic-linear isomerization barrier, with CBS(5,6)-quality. To partially account for the incompleteness of the N-electron basis and other minor effects, the available accurate experimental data on the relevant diatomics were used to obtain direct-fit curves that replace the theoretical ones in the many-body expansion. Besides describing properly long-range interactions at all asymptotic channels and permutational symmetry by built-in construction, the PES reported here reproduces the proper exothermicities at dissociation regions as well as the spectroscopy of the diatomic fragments. Bound vibrational state calculations in both linear and cyclic isomers have also been carried out, unveiling a good match of the available data on C3(ã 3Πu), while assisting with IR band positions for C3(3A2') that may serve as a guide for its laboratory and astronomical detection.

The resolution of acute inflammation induced by cyclic AMP is dependent on annexin A1.

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein known for its anti-inflammatory and pro-resolving effects. We have shown previously that the cAMP-enhancing compounds rolipram (ROL; a PDE4 inhibitor) and Bt2cAMP (a cAMP mimetic) drive caspase-dependent resolution of neutrophilic inflammation. In this follow-up study, we investigated whether AnxA1 could be involved in the pro-resolving properties of these compounds using a model of LPS-induced inflammation in BALB/c mice. The treatment with ROL or Bt2cAMP at the peak of inflammation shortened resolution intervals, improved resolution indices, and increased AnxA1 expression. In vitro studies showed that ROL and Bt2cAMP induced AnxA1 expression and phosphorylation, and this effect was prevented by PKA inhibitors, suggesting the involvement of PKA in ROL-induced AnxA1 expression. Akin to these in vitro findings, H89 prevented ROL- and Bt2cAMP-induced resolution of inflammation, and it was associated with decreased levels of intact AnxA1. Moreover, two different strategies to block the AnxA1 pathway (by using N-t-Boc-Met-Leu-Phe, a nonselective AnxA1 receptor antagonist, or by using an anti-AnxA1 neutralizing antiserum) prevented ROL- and Bt2cAMP-induced resolution and neutrophil apoptosis. Likewise, the ability of ROL or Bt2cAMP to induce neutrophil apoptosis was impaired in AnxA-knock-out mice. Finally, in in vitro settings, ROL and Bt2cAMP overrode the survival-inducing effect of LPS in human neutrophils in an AnxA1-dependent manner. Our results show that AnxA1 is at least one of the endogenous determinants mediating the pro-resolving properties of cAMP-elevating agents and cAMP-mimetic drugs.

Synthesis, characterization and applications of maghemite beads functionalized with rabbit antibodies.

Magnetic nanoparticles (NPs) have attracted great attention owing to their applications in the biomedical field. In the present work, maghemite (γFe2O3) NPs of 6.5 nm were prepared using a sonochemical method and used to prepare magnetic beads through silanization with 3-aminopropyltrimethoxysilane (APTS). Subsequently, amino groups in the resulting APTS-γFe2O3 beads were converted to carboxylic acid (CARB-γFe2O3) through the succinic anhydride reaction, as confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and dynamic light scattering (DLS) measurements. The size of these beads was measured as 12 nm and their hydrodynamic diameter as 490 nm, using TEM analysis and DLS, respectively. The CARB-γFe2O3 beads were further functionalized by immobilizing rabbit antibodies on their surfaces; the immobilization was confirmed by flow cytometry and ionic strength. The samples were further characterized by Mössbauer spectroscopy and DC magnetization measurements. Studies on magnetic relaxivities showed that magnetic beads present great potential for application in MR imaging.

Human visceral leishmaniasis: factors associated with deaths in Belo Horizonte, Minas Gerais state, Brazil from 2006 to 2013.

The aim of this study was to evaluate the distribution of cases and the social determinants associated with death from human visceral leishmaniasis (HVL) and VL-HIV co-infection in Belo Horizonte, Minas Gerais state, Brazil, between 2006 and 2013. Descriptive statistics and analysis of associations were performed using chi-square of the raised variables, such as sex, age, skin colour and schooling of cases of HVL. During the study period, there were 866 cases of HVL with 111 deaths in Belo Horizonte. Morbidity and lethality rates (LR) of HVL in Belo Horizonte remained high over almost all the years evaluated, with an average incidence rate of 4.18 cases/100 000 inhabitants and a LR of 11.16%. With respect to skin colour, it was found that people characterised as black or mulatto had higher morbidity, followed by white. Regarding schooling, LR was more prevalent among individuals with lower education. One of the social risk factors was co-infection with HIV, which was present in many cases of HVL. Furthermore, it was found that older age and the male sex were also risk factors for death from HVL in Belo Horizonte.

Cn (n=2-4): current status.

The major aspects of the C2, C3 and C4 elemental carbon clusters are surveyed. For C2, a brief analysis of its current status is presented. Regarding C3, the most recent results obtained in our group are reviewed with emphasis on modelling its potential energy surface which is particularly complicated due to the presence of multiple conical intersections. As for C4, the most stable isomeric forms of both triplet and singlet spin states and their possible interconversion pathways are examined afresh by means of accurate ab initio calculations. The main strategies for modelling the ground triplet C4 potential are also discussed. Starting from a truncated cluster expansion and a previously reported DMBE form for C3, an approximate four-body term is calibrated from the ab initio energies. The final six-dimensional global DMBE form so obtained reproduces all known topographical aspects while providing an accurate description of the C4 linear-rhombic isomerization pathway. It is therefore commended for both spectroscopic and reaction dynamics studies.This article is part of the theme issue 'Modern theoretical chemistry'.

Multiple conical intersections in small linear parameter Jahn-Teller systems: the DMBE potential energy surface of ground-state C3 revisited.

A new single-sheeted DMBE potential energy surface for ground-state C3 is reported. The novel analytical form accurately describes the three symmetry-equivalent C2v disjoint seams, in addition to the symmetry-required D3h one, over the entire configuration space. The present formalism warrants by built-in construction the confluence of the above crossings, and the rotation-in-plane of the C2v seams when the perimeter of the molecule fluctuates. Up to 1050 ab initio energies have been employed in the calibration procedure, of which 421 map the loci of intersection. The calculated energies have been scaled to account for the incompleteness of the basis set and truncation of the MRCI expansion, and fitted analytically with chemical accuracy. The novel form is shown to accurately mimic the region defined by the 4 conical intersections, while exhibiting similar attributes to the previously reported one [J. Chem. Phys., 2015, 143, 074302] at the regions of configuration space away from the crossing seams. Despite being mainly addressed to C3, the present approach should be applicable to adiabatic PESs of any X3 system experiencing similar topological attributes, in particular the small-linear-parameter Jahn-Teller molecules.

Nematode assemblages associated with the parthenogenetic lizard Ameivula nativo in six restinga areas along the eastern coast of Brazil.

We surveyed the nematode assemblages associated with populations of the parthenogenetic whiptail lizard Ameivula nativo from six coastal restinga areas in eastern Brazil: Setiba, Comboios and Guriri (State of Espirito Santo) and Guaratiba, Prado and Maraú (State of Bahia). A total of five nematode species (Physaloptera retusa, Physalopteroides venancioi, Skrjabinelazia intermedia, Subulura lacertilia and Parapharyngodon sp.) were recorded from the six different populations of A. nativo. There was considerable variation in overall prevalence of infection (1-42%) among study sites, but geographical distance among areas did not influence similarity in the composition of nematode assemblages. Overall intensity of infection was not affected by lizard body size and did not seem to affect host body condition, based on pooled data of all populations. The studied populations of the unisexual A. nativo had relatively low prevalences and intensities of infection compared to some bisexual congeners and to sympatric lizards from other families for which such data are available. We believe that the low richness of the nematode fauna associated with A. nativo, both locally and regionally, may reflect its narrow geographic distribution and the low diversity of habitats it occupies.

Distinct right ventricle remodeling in response to pressure overload in the rat.

Pulmonary arterial hypertension (PAH), the most serious chronic disorder of the pulmonary circulation, is characterized by pulmonary vasoconstriction and remodeling, resulting in increased afterload on the right ventricle (RV). In fact, RV function is the main determinant of prognosis in PAH. The most frequently used experimental models of PAH include monocrotaline- and chronic hypoxia-induced PAH, which primarily affect the pulmonary circulation. Alternatively, pulmonary artery banding (PAB) can be performed to achieve RV overload without affecting the pulmonary vasculature, allowing researchers to determine the RV-specific effects of their drugs/interventions. In this work, using two different degrees of pulmonary artery constriction, we characterize, in full detail, PAB-induced adaptive and maladaptive remodeling of the RV at 3 wk after PAB surgery. Our results show that application of a mild constriction resulted in adaptive hypertrophy of the RV, with preserved systolic and diastolic function, while application of a severe constriction resulted in maladaptive hypertrophy, with chamber dilation and systolic and diastolic dysfunction up to the isolated cardiomyocyte level. By applying two different degrees of constriction, we describe, for the first time, a reliable and short-duration PAB model in which RV adaptation can be distinguished at 3 wk after surgery. We characterize, in full detail, structural and functional changes of the RV in its response to moderate and severe constriction, allowing researchers to better study RV physiology and transition to dysfunction and failure, as well as to determine the effects of new therapies.

The challenge of improving boiling: lessons learned from a randomized controlled trial of water pasteurization and safe storage in Peru.

Boiling is the most common method of household water treatment in developing countries; however, it is not always effectively practised. We conducted a randomized controlled trial among 210 households to assess the effectiveness of water pasteurization and safe-storage interventions in reducing Escherichia coli contamination of household drinking water in a water-boiling population in rural Peru. Households were randomized to receive either a safe-storage container or a safe-storage container plus water pasteurization indicator or to a control group. During a 13-week follow-up period, households that received a safe-storage container and water pasteurization indicator did not have a significantly different prevalence of stored drinking-water contamination relative to the control group [prevalence ratio (PR) 1·18, 95% confidence interval (CI) 0·92-1·52]. Similarly, receipt of a safe-storage container alone had no effect on prevalence of contamination (PR 1·02, 95% CI 0·79-1·31). Although use of water pasteurization indicators and locally available storage containers did not increase the safety of household drinking water in this study, future research could illuminate factors that facilitate the effective use of these interventions to improve water quality and reduce the risk of waterborne disease in populations that boil drinking water.

Predominance of Clostridium difficile ribotypes 012, 027 and 046 in a university hospital in Chile, 2012.

In a 1-year survey at a university hospital we found that 20·6% (81/392) of patients with antibiotic associated diarrohea where positive for C. difficile. The most common PCR ribotypes were 012 (14·8%), 027 (12·3%), 046 (12·3%) and 014/020 (9·9). The incidence rate was 2·6 cases of C. difficile infection for every 1000 outpatients.

Resveratrol treatment rescues hyperleptinemia and improves hypothalamic leptin signaling programmed by maternal high-fat diet in rats.

PURPOSE: Perinatal high-fat diet is associated with obesity and metabolic diseases in adult offspring. Resveratrol has been shown to exert antioxidant and anti-obesity actions. However, the effects of resveratrol on leptinemia and leptin signaling are still unknown as well as whether resveratrol treatment can improve metabolic outcomes programmed by maternal high-fat diet. We hypothesize that resveratrol treatment in male rats programmed by high-fat diet would decrease body weight and food intake, and leptinemia with changes in central leptin signaling. METHODS: Female Wistar rats were divided into two groups: control group (C), which received a standard diet containing 9 % of the calories as fat, and high-fat group (HF), which received a diet containing 28 % of the calories as fat. Dams were fed in C or HF diet during 8 weeks before mating and throughout gestation and lactation. C and HF male offspring received standard diet throughout life. From 150 until 180 days of age, offspring received resveratrol (30 mg/Kg body weight/day) or vehicle (carboxymethylcellulose). RESULTS: HF offspring had increased body weight, hyperphagia and increased subcutaneous and visceral fat mass compared to controls, and resveratrol treatment decreased adiposity. HF offspring had increased leptinemia as well as increased SOCS3 in the arcuate nucleus of the hypothalamus, which suggest central leptin resistance. Resveratrol treatment rescued leptinemia and increased p-STAT3 content in the hypothalamus with no changes in SOCS3, suggesting improvement in leptin signaling. CONCLUSIONS: Collectively, our data suggest that resveratrol could reverse hyperleptinemia and improve central leptin action in adult offspring from HF mothers attenuating obesity.

The Jahn-Teller plus pseudo-Jahn-Teller vibronic problem in the C3 radical and its topological implications.

The combined Jahn-Teller plus pseudo-Jahn-Teller [(E'+A1')⊗e'] problem is discussed for the tricarbon radical (C3) by means of ab initio calculations at the multireference configuration interaction level of theory. For the (1)E' electronic state arising from a e'(2) valence configuration, three additional symmetry-equivalent C2v seams are found to lie in close proximity to the D3h symmetry-required seam over the entire range of the breathing coordinate here considered. As the perimeter of the molecule increases, the C2v disjoint seams approach the D3h one almost linearly and ultimately coalesce with it at Q1 = 5.005 a0, thence forming an intersection node or confluence. By further increasing the size of the molecular triangle, the C2v seams get rotated by ±π in the g-h plane. A three-state vibronic Hamiltonian is also proposed to model locally the title system and shown to accurately mimic the calculated data over the region close to the minimum energy crossing point. No net geometric phase effect is observed when the associated electronic wave functions are adiabatically transported along closed paths encircling the four singularity points. For all paths enclosing the intersection node, the sign reversal criterion is shown to be not fulfilled, even for infinitesimal loops. The results so obtained are expected to be valid for other ring systems experiencing similar topological attributes.

Antimutagenicity and antigenotoxicity of Aloe arborescens Miller and Aloe barbadensis Miller in Aspergillus nidulans and Wistar rats.

Medicinal plants such as Aloe arborescens Miller and Aloe barbadensis Miller are used by the general population to treat various diseases. Therefore, the aim of this study was to evaluate the antimutagenicity of these two species using a methG1 system in Aspergillus nidulans and the comet assay in rats. The animals were treated with the plants at concentrations of 360 and 720 mg/kg body weight (1 and 2, respectively) by gavage for 14 days, followed by the administration of etoposide on treatment day 8. Blood samples were prepared for analysis of DNA damage. For the test in A. nidulans, the biA1methG1 lineage conidia were treated for 4 h with both plant species at concentrations of 4 and 8% (w/v). Then, they were washed and plated on a selective medium for frequency analysis of survival and mutation. The results of the comet assay showed that both plants were antigenotoxic compared to etoposide, which was not a typical response of methG1 systems, where only the highest concentration of plant extracts usually exhibit beneficial effects. This study demonstrates the potential antigenotoxicity and antimutagenicity of the Aloe plants tested and, therefore, supports their use as a form of preventive therapy and for health maintenance by the population.