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Showing papers by "University of Coimbra published in 2001"


Journal ArticleDOI
TL;DR: In this paper, the authors constructed a new set of isochrones, called the Y2 Isochrones, that represent an update of the Revised Yale IsoChrones (RYI), using improved opacities and equations of state.
Abstract: We have constructed a new set of isochrones, called the Y2 Isochrones, that represent an update of the Revised Yale Isochrones (RYI), using improved opacities and equations of state. Helium diffusion and convective core overshoot have also been taken into consideration. This first set of isochrones is for the scaled solar mixture. A subsequent paper will consider the effects of α-element enhancement, believed to be relevant in many stellar systems. Two additionally significant features of these isochrones are that (1) the stellar models start their evolution from the pre-main-sequence birthline instead of from the zero-age main sequence and (2) the color transformation has been performed using both the latest table of Lejeune et al., and the older, but now modified, Green et al. table. The isochrones have performed well under the tests conducted thus far. The reduction in the age of the Galactic globular clusters caused by this update in stellar models alone is approximately 15% relative to RYI-based studies. When the suggested modification for the α-element enhancement is made as well, the total age reduction becomes approximately 20%. When post-RGB evolutionary stages are included, we find that the ages of globular clusters derived from integrated colors are consistent with the isochrone fitting ages.

893 citations


Journal ArticleDOI
TL;DR: The type of riparian vegetation has the potential to control the diversity and abundance of shredders and changes in Riparian vegetation have the Potential to affect the assemblages of aquatic invertebrates.
Abstract: Leaves entering low order streams are subject to physical abrasion, microbial degradation and invertebrate fragmentation. Aquatic invertebrates feeding on leaves are known as shredders and their densities tend to be correlated with the spatial and temporal accumulation of organic matter in streams. Shredders discriminate among the variety of leaves normally found in the stream; this discrimination may be related to differences in leaf toughness, plant nutrient content of leaves and the presence of secondary compounds. Shredders also consume leaves preferentially after the establishment of a well-developed microbial community. This preference may be the result of changes in leaf matrix carried out by the microbial community or the presence of fungal hyphae with a higher nutrition value than the leaves themselves. The immediate consequence of invertebrate feeding on leaves is the incorporation of plant material into secondary production and the fragmentation of leaves. The relative importance of fungi and invertebrates in the decomposition process depends upon the density of shredders, which, in turn, may depend on litter accumulation in streams. Therefore, the type of riparian vegetation has the potential to control the diversity and abundance of shredders and changes in riparian vegetation have the potential to affect the assemblages of aquatic invertebrates.

738 citations


Journal ArticleDOI
TL;DR: In this paper, an updated version of the empirically and semi-empirically calibrated B aS eL library of synthetic stellar spectra was used to calculate synthetic photometry in the (UBV) J (RI) C JHKLL ′ M, HST-WFPC2, Geneva, and Washington systems for the entire set of non-rotating Geneva stellar evolution models covering masses from 0.4-0.8 to 120-150 and metallicities (1/50 ) to 0.1 (5 ).
Abstract: We have used an updated version of the empirically and semi-empirically calibrated B aS eL library of synthetic stellar spectra of Lejeune et al.([CITE], [CITE]) and Westera et al.([CITE]) to calculate synthetic photometry in the (UBV) J (RI) C JHKLL ′ M , HST-WFPC2, Geneva, and Washington systems for the entire set of non-rotating Geneva stellar evolution models covering masses from 0.4-0.8 to 120-150 and metallicities (1/50 ) to 0.1 (5 ). The results are provided in a database which includes all individual stellar tracks and the corresponding isochrones covering ages from 103 yr to 16-20 Gyr in time steps of 0.05 dex. The database also includes a new grid of stellar tracks of very metal-poor stars () from calculated with the Geneva stellar evolution code.

576 citations


Journal ArticleDOI
TL;DR: It is found that phosphatidylinositol 3-phosphate (PI[3]P) accumulates greatly but transiently on the phagosomal membrane, and the possibility that PI(3)P production by VPS34 may be targeted during the maturation arrest induced by some intracellular parasites is raised.
Abstract: Phagosomes acquire their microbicidal properties by fusion with lysosomes. Products of phosphatidylinositol 3-kinase (PI 3-kinase) are required for phagosome formation, but their role in maturation is unknown. Using chimeric fluorescent proteins encoding tandem FYVE domains, we found that phosphatidylinositol 3-phosphate (PI[3]P) accumulates greatly but transiently on the phagosomal membrane. Unlike the 3'-phosphoinositides generated by class I PI 3-kinases which are evident in the nascent phagosomal cup, PI(3)P is only detectable after the phagosome has sealed. The class III PI 3-kinase VPS34 was found to be responsible for PI(3)P synthesis and essential for phagolysosome formation. In contrast, selective ablation of class I PI 3-kinase revealed that optimal phagocytosis, but not maturation, requires this type of enzyme. These results highlight the differential functional role of the two families of kinases, and raise the possibility that PI(3)P production by VPS34 may be targeted during the maturation arrest induced by some intracellular parasites.

529 citations


Journal ArticleDOI
TL;DR: It is confirmed that interstitial protium may act as a shallow donor in zinc oxide, by direct spectroscopic observation of its muonium counterpart, and results for the cadmium chalcogenides suggest that such shallow donor states are generic to the II-VI compounds.
Abstract: We confirm the recent prediction that interstitial protium may act as a shallow donor in zinc oxide, by direct spectroscopic observation of its muonium counterpart. On implantation into ZnO, positive muons---chemically analogous to protons in this context---form paramagnetic centers below about 40 K. The muon-electron contact hyperfine interaction, as well as the temperature and activation energy for ionization, imply a shallow level. Similar results for the cadmium chalcogenides suggest that such shallow donor states are generic to the II-VI compounds. The donor level depths should serve as a guide for the electrical activity of interstitial hydrogen.

398 citations


Journal ArticleDOI
TL;DR: This review focuses on the various parameters that are considered to be crucial to optimize the use of cationic lipid-DNA complexes for gene therapy purposes, from the biophysical aspects underlying the formation of the complexes to the different biological barriers that need to be surpassed for gene expression to occur.

362 citations


Journal ArticleDOI
TL;DR: This paper is a review of recent information on litterfall, standing stock of benthic organic matter, breakdown rates, and fungal colonization of organic matter in streams, and the fate of detritus in streams.
Abstract: This paper is a review of recent (< or =10 years) information on litterfall, standing stock of benthic organic matter, breakdown rates, and fungal colonization of organic matter in streams. In some cases, recent research reinforces the findings of classic reference papers. In other cases, the additional knowledge provided by recent research introduces a higher variation in the processes analyzed. In many aspects, especially those concerning stream organic matter, the review is biased towards the temperate North American streams, reflecting the fact that most research was carried out there. However, during the 1990s European studies increased enormously, especially those related with instream processes, such as leaf litter decomposition. The first part of this review analyzes the origin of allochthonous organic matter to streams (litterfall, retention, and storage), and it provides data on the amounts estimated in different streams and on the methodology used in the studies. The second part analyzes the fate of detritus in streams: mechanisms of leaf breakdown, relative importance of fungi and bacteria, factors affecting the activity of microbial decomposers, and chemical changes of leaf litter during decomposition. A list of breakdown rates of several different leaf species is given, together with the methodology used, and the main characteristics of the incubation streams.

335 citations


Journal ArticleDOI
TL;DR: It is shown that tetramer dissociation and partial unfolding of the monomer precedes amyloid fibril formation, and that TTR variants with the least thermodynamically stable non-native monomer produce the largest amount of partially unfolded monomeric species and soluble aggregates under conditions that are close to physiological.

318 citations


Posted Content
TL;DR: In this article, the authors focus mainly on dismissals protection, distinguishing between the themes of employment and unemployment development and labor market dynamics proper, and formalize the link between analyses of levels and changes in variables.
Abstract: Empirical investigation of the labor market consequences of employment protection has mushroomed since Lazear's (1990) pioneering study. Having sketched the theoretical background, we chart the course of the modern empirical literature. We focus mainly on dismissals protection, distinguishing between the themes of employment and unemployment development and labor market dynamics proper. Our discussion of employment and unemployment largely deals with the effect of employment protection on levels of these outcome indicators. We distinguish between overall and compositional effects (e.g., by demographic group and type of contract), between developing and industrialized nations, and identify some key control variables. Our discussion of labor market dynamics focuses on the speed of adjustment issue and on gross flows. It also formalizes the link between analyses of levels and changes in variables. At all times potential offsets to the adverse effects of employment protection receive consideration.

289 citations


Journal ArticleDOI
TL;DR: Both in vivo and in vitro tests based on the alteration of LDH activity of D. magna indicate that LDH action may be used as an indicative parameter in aquatic toxicity tests.

277 citations


Journal ArticleDOI
TL;DR: Tropical shredders may exhibit the same basic patterns of food exploitation as their temperate counterparts, and current concepts relating to the role of shredder in stream detritus dynamics may well be applicable to tropical streams, although essentially derived from temperate systems.
Abstract: 1. The importance of leaf quality to the nutritional ecology of lotic shredders is well established for temperate species but virtually unknown for tropical taxa. In the present study, we compared the feeding behaviour and performance of two tropical and two temperate shredders in a series of pair-wise experiments. 2. Specifically, we tested whether leaf conditioning status (stream-conditioned versus unconditioned leaves) and geographical origin (temperate Alnus glutinosa versus tropical Hura crepitans leaves) affect the food preference, survivorship, and growth of selected shredders from low and high latitudes in a consistent manner. The animals used in experiments were the caddis-flies Nectopsyche argentata and Phylloicus priapulus from Venezuela, Sericostoma vittatum from Central Portugal, and the amphipod Gammarus pulex from Northern Germany. 3. In general, all shredders exhibited the same high preference for conditioned over unconditioned leaves, irrespective of the geographical origin of the leaf or shredder species. 4. A corresponding tendency for higher growth was found for sets of animals offered conditioned leaves, with the differences in growth being clearer in the two tropical shredders. Survivorship of the two temperate species was consistently high (> 83%) regardless of the diet offered, whereas the tropical shredders survived better on conditioned (77–90%) as compared with unconditioned (54–87%) leaves, although not significantly so. 5. With the exception of the temperate S. vittatum, shredders did not select or perform better on leaves to which they had previously been exposed, indicating a potential adaptation to native leaf species is over-ridden by intrinsic leaf properties. 6. Taken together, the results of this study suggest that tropical shredders may exhibit the same basic patterns of food exploitation as their temperate counterparts. Consequently, current concepts relating to the role of shredders in stream detritus dynamics may well be applicable to tropical streams, although essentially derived from temperate systems.

Journal ArticleDOI
TL;DR: In this article, the authors extended the BaSeL standard stellar library to non-solar metallicities, down to [Fe/H] ~ -2.0 dex, which is consistent simultaneously with both colour-temperature relations and colour-absolute magnitude diagrams.
Abstract: We extend the colour calibration of the widely used BaSeL standard stellar library (Lejeune, Cuisinier, & Buser 1997, 1998) to non-solar metallicities, down to [Fe/H] ~ -2.0 dex. Surprisingly, we find that at the present epoch it is virtually impossible to establish a unique calibration of UBVRIJHKL colours in terms of stellar metallicity [Fe/H] which is consistent simultaneously with both colour-temperature relations and colour-absolute magnitude diagrams (CMDs) based on observed globular cluster photometry data and on published, currently popular standard stellar evolutionary tracks and isochrones. The problem appears to be related to the long-standing incompleteness in our understanding of convection in late-type stellar evolution, but is also due to a serious lack of relevant observational calibration data that would help resolve, or at least further significant progress towards resolving this issue. In view of the most important applications of the BaSeL library, we here propose two different metallicity calibration versions: (1) the "WLBC 99" library, which consistently matches empirical colour-temperature relations and which, therefore, should make an ideal tool for the study of individual stars; and (2), the "PADOVA 2000" library, which provides isochrones from the Padova 2000 grid (Girardi et al., 2000) that successfully reproduce Galactic globular-cluster colour-absolute magnitude diagrams and which thus should prove particularly useful for studies of collective phenomena in stellar populations in clusters and galaxies.

Journal ArticleDOI
TL;DR: Results showed that this tool is able to infer weights that restores in a stable way the assignment examples and that it was able to identify “inconsistencies” in the assignmentExamples.

Journal ArticleDOI
TL;DR: Using pulse radiolysis and triplet energy transfer has enabled to measure the triplet energies in a broad range of different pi-conjugated polymers and suggests that polymers with singlet gap <1.3 eV will have a triplet ground state.
Abstract: Using pulse radiolysis and triplet energy transfer has enabled us to measure the triplet energies in a broad range of different pi -conjugated polymers. In all eases we find that the 1(3)B(u) is Of order 0.6 to 1 eV below the 1 B-1(u), indicative of localized triplet states with strong electron-electron correlation. We also observe that the 1(1)A(g)-1(3)B(u), gap decreases linearly as the I(1)A(g)-1(1)B(u) gap decreases even though polymers with very different structure have been studied. This surprising result suggests that polymers with singlet gap <1.3 eV will have a triplet ground state.

Journal ArticleDOI
TL;DR: The data suggest that Psoriasis patients must be considered as a group at risk for cardiovascular disease and that this risk seems to be higher in severe psoriasis.

Journal ArticleDOI
TL;DR: This paper considers Markovian models with sinusoidal arrival rates and proposes two simple modifications of SIPP that will produce reliable staffing levels in models whose parameters span a broad range of practical situations.
Abstract: This paper evaluates the practice of determining staffing requirements in service systems with random cyclic demands by using a series of stationary queueing models. We consider Markovian models with sinusoidal arrival rates and use numerical methods to show that the commonly used "stationary independent period by period" (SIPP) approach to setting staffing requirements is inaccurate for parameter values corresponding to many real situations. Specifically, using the SIPP approach can result in staffing levels that do not meet specified period by period probability of delay targets during a significant fraction of the cycle. We determine the manner in which the various system parameters affect SIPP reliability and identify domains for which SIPP will be accurate. After exploring several alternatives, we propose two simple modifications of SIPP that will produce reliable staffing levels in models whose parameters span a broad range of practical situations. Our conclusions from the sinusoidal model are tested against some empirical data.

Journal ArticleDOI
TL;DR: A general decline in health-related quality of life over time was observed in the pooled data; however, significant improvements were achieved in patients involved in the pharmaceutical care programme in some countries.
Abstract: Objective: This study aimed to measure the outcomes of a harmonised, structured pharmaceutical care programme provided to elderly patients: (greater than or equal to 65 years of age) by community pharmacists in a multicentre international study performed in 7 European countries. Design and setting: The study was a randomised, controlled. longitudinal, clinical trial with repeated measures performed over an Is-month period. A total of 104 intervention and 86 control pharmacy sites participated in the research and 1290 intervention patients and 1164 control patients were recruited into the study. Main outcome measures and results: A general decline in health-related quality of lift: over time was observed in the pooled data; however, significant improvements were achieved in patients involved in the pharmaceutical care programme in some countries. Intervention patients reported better control of their medical conditions as a result of the study and cost savings associated with pharmaceutical care provision were observed in most countries. The new structured service was well accepted by intervention patients and patient satisfaction with the services improved during the study. The pharmacists involved in providing pharmaceutical care had a positive opinion on the new approach, as did the majority of general practitioners surveyed. The positive effects appear to have been achieved via social and psychosocial aspects of the intervention, such as the increased support provided by community pharmacists, rather than via biomedical mechanisms. Conclusions: This study is the first large-scale, multicentre study to investigate the effects of pharmaceutical care provision by community pharmacists to elderly patients. Future research methodology and implementation will be informed by the experience gained from this challenging trial.

Journal ArticleDOI
TL;DR: The data suggest that the accumulation and persistence of oxidized mtDNA may be due, not to the stability of the adducts, but to some as yet undefined toxic lesion that causes long-lasting stimulation of ROS generation by doxorubicin.

Journal ArticleDOI
TL;DR: The purpose of this study was to describe the age‐specific distribution of midfemoral intracortical porosity throughout the cortical width in males and females, and there were significant age‐ and site‐related differences in porosity, pore number, and pore size.
Abstract: The purpose of this study was to describe the age-specific distribution of midfemoral intracortical porosity throughout the cortical width in males and females. Microradiography and an automated image analysis system were used to study midfemoral cortical bone specimens from 163 white people, including 77 males and 86 females, in a recent anthropological collection covering a broad age range. In each specimen, porosity (percentage of the cortical bone area occupied by pores), pore number, and pore size were measured throughout the entire cortex and in three cortical subregions of equal width labeled the periosteal, midcortical, and endosteal subregions. For each gender, relationships linking age to porosity, pore number, and mean pore size were assessed using regression analysis. In addition, age- and site-related changes in these three variables were tested for significance using two-way analysis of variance (ANOVA). Age explained 52% of the porosity variance in females and 13.5% in males. In each gender, there were significant age- and site-related differences in porosity, pore number, and pore size. In adults aged 60 years or younger, both pore size and pore number increased with increasing age, whereas in adults older than 60 years, pore size continued to increase but pore number decreased. In males, the age-related changes in pore size and pore number were proportionally similar in the three cortical subregions. In females, in contrast, the changes predominated in the endosteal subregion and resulted in significant cortical thinning.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the variation of physicochemical parameters, biomass and growth of green macroalgae collected between January 1993 and January 1997 in the Mondego Estuary (western coast of Portugal) with the aim to identify the factors that control opportunistic macroalgal abundance in the system.
Abstract: Data on the variation of physicochemical parameters, biomass and growth of green macroalgae (mostlyEnteromorpha ) collected between January 1993 and January 1997 in the Mondego Estuary (western coast of Portugal) was analysed with the aim to identify the factors that control opportunistic macroalgal abundance in the system. The annual biomass of Enteromorpha spp. is strongly dependent on the amount of fresh water that enters the system during winter and spring. In turn, the input of fresh water is regulated by precipitation and by river management practices. The optimization of the rice crops from the upstream valley depends on their water level, which determines the number of days and hours per day during which sluice gates remain open in winter and spring. River flow has significant impacts on salinity, N:P ratios, current velocities and light extinction coefficients within the system. The interaction of all these factors controls macroalgal growth and biomass loss processes. In winters and springs during which sluice gates are often closed due to water deficiency of the rice fields (dry winter and spring or dry winter followed by rainy spring), little fresh water enters the system and consequently, salinity remains high, N:P ratios around 20, light penetration increases, and current velocities fall. These conditions facilitate macroalgal fixation, enhance their growth and spring blooms occur. On the contrary, during winters and springs when fresh water is in excess of rice fields' needs (rainy winters and springs), sluice gates remain open for long periods of time. High input of fresh water to the system causes salinity and light penetration to decrease, while N:P ratios and current velocities increase. These conditions contribute both to reduced Enteromorpha growth and higher loss of macroalgal biomass from the system to the ocean. The present work shows that the inter-annual variation of macroalgal biomass in the Mondego Estuary is controlled by hydrodynamics, which in turn depends on precipitation and on river management, according with the water needs of the upstream rice crop.

Journal ArticleDOI
TL;DR: The results further establish that lentiviruses may represent an efficient gene delivery system for the screening of therapeutic molecules in Huntington's disease.

Proceedings ArticleDOI
01 Dec 2001
TL;DR: A general model for central catadioptric image formation made up of three functions: a linear function mapping the world into an oriented projective plane, a nonlinear transformation between twooriented projective planes, and a collineation in the plane is established.
Abstract: An imaging system with a single effective viewpoint is called a central projection system. The conventional perspective camera is an example of a central projection system. Systems using mirrors to enhance the field of view while keeping a unique center of projection are also examples of central projection systems. Perspective image formation can be described by a linear model with well known properties. In general central catadioptric imaging, the mapping between points in the world and in the image is highly nonlinear. The paper establishes a general model for central catadioptric image formation made up of three functions: a linear function mapping the world into an oriented projective plane, a nonlinear transformation between two oriented projective planes, and a collineation in the plane. The model is used to study issues in the projection of lines. The equations and geometric properties of general catadioptric imaging of lines are derived. The application of the results in auto-calibration of central catadioptric systems and reconstruction are discussed. A method to calibrate the system using three line images is presented.

Journal ArticleDOI
TL;DR: The results suggest that the isopod P. dilatatus is a suitable species for use in toxicity tests and that energy reserves could be used as effect criteria in both laboratory and field studies.

Journal ArticleDOI
TL;DR: The results with cells pretreated with metabolic inhibitors or lysosomotropic agents clearly indicate that DOPE-containing liposomes are internalized essentially by endocytosis and that acidification of the endosomes is not the only mechanism involved in the destabilization of the liposome inside the cell.

Journal ArticleDOI
TL;DR: In this paper, the acid-base equilibria for 4-hydroxycoumarin, 7-hydrox-4-methylcoumin, and their thione derivatives in different media for their ground and lowest energy singlet and triplet excited states were studied.

Journal ArticleDOI
TL;DR: Investigation of the processing of alder litter in 12 sites ranging from 2nd to 6th order in central Portugal during autumn/winter and spring/summer seasons found a pattern of shifting in processing vectors was observed, possibly because food was nonlimiting.
Abstract: Dissolved nutrients and temperature tend to increase in a downstream direction, whereas shredder density tends to decrease. As a result, the relative importance of microbes (bacteria and fungi) and invertebrates in leaf litter processing may gradually shift along a stream gradient. Therefore, we hypothesized that differences in litter decay between fine-mesh (invertebrates excluded) and coarse-mesh (accessible to invertebrates) bags will be high in low-order streams (i.e., 4). To test this hypothesis, we investigated the processing of alder (Alnus glutinosa) litter in 12 sites ranging from 2nd to 6th order in central Portugal during autumn/winter and spring/summer seasons. Mass loss rates (measured as % ash-free dry mass [AFDM]) were higher in spring/summer than in autumn/winter and higher in coarse- than in fine-mesh bags. No clear relationship was observed between river order and litter processing (% AFDM loss). In spring/summer, the difference in remain...

Journal ArticleDOI
TL;DR: Examination of evidence for tuberculosis (TB) in juvenile individuals from early 20th century documented skeletons in Coimbra, Portugal, based on data arising before antibiotics became available for treatment can contribute to the future diagnosis of TB in non-documented skeletal material, and will facilitate a more reliable diagnosis in juvenileindividuals.
Abstract: The aim of this study was to examine the evidence, and consider the differential diagnosis, for tuberculosis (TB) in juvenile individuals from early 20th century documented skeletons. There are 66 male and female juvenile individuals in the Coimbra Identified Skeletal Collection (CISC) with an age at death ranging from 7-21 years. The individuals died between 1904-1936 in different areas of Coimbra, Portugal. Eighteen of these individuals died from TB affecting different parts of the body. Thirteen (72.2%) showed skeletal lesions that may be related to this infection. Of the 48 individuals with a non-tuberculous cause of death, only 2 (4.2%) had skeletal changes that could be attributed to TB. The distribution of skeletal manifestations caused by the types of TB under study, based on macroscopic and radiological findings, is described and discussed. In addition, the medical records from 6 tuberculous individuals who died in Coimbra University Hospital (CUH) were analysed, and the information, including their diet and access to treatment, is presented. This work, based on data arising before antibiotics became available for treatment, can contribute to the future diagnosis of TB in non-documented skeletal material, and will facilitate a more reliable diagnosis of TB in juvenile individuals.

Journal ArticleDOI
TL;DR: In this article, a simple metal with exponentially overlapped ion cores is used as the paradigm for an augmented version of the stabilized jellium equation of state (SJEOS).
Abstract: Explicit functions are widely used to interpolate, extrapolate, and differentiate theoretical or experimental data on the equation of state (EOS) of a solid. We present two EOS functions which are theoretically motivated. The simplest realistic model for a simple metal, the stabilized jellium (SJ) or structureless pseudopotential model, is the paradigm for our SJEOS. A simple metal with exponentially overlapped ion cores is the paradigm for an augmented version (ASJEOS) of the SJEOS. For the three solids tested (Al, Li, Mo), the ASJEOS matches all-electron calculations better than prior equations of state. Like most of the prior EOS's, the ASJEOS predicts pressure P as a function of compressed volume $v$ from only a few equilibrium inputs: the volume ${v}_{0},$ the bulk modulus ${B}_{0},$ and its pressure derivative ${B}_{1}.$ Under expansion, the cohesive energy serves as another input. A further advantage of the new equation of state is that these equilibrium properties other than ${v}_{0}$ may be found by linear fitting methods. The SJEOS can be used to correct ${B}_{0}$ and the EOS found from an approximate density functional, if the corresponding error in ${v}_{0}$ is known. We also (a) estimate the typically small contribution of phonon zero-point vibration to the EOS, (b) find that the physical hardness $\mathrm{Bv}$ does not maximize at equilibrium, and (c) show that the ``ideal metal'' of Shore and Rose is the zero-valence limit of stabilized jellium.

Journal ArticleDOI
TL;DR: Results suggest that Aβ25–35 can promote the PTP induced by Ca2+, and could be reversed when Ca2+ was removed by EGTA or when ADP plus oligomycin were present
Abstract: In this work the effect of the neurotoxic amino acid sequence, Aβ25–35, on brain mitochondrial permeability transition pore (PTP) was studied. For the purpose, the mitochondrial transmembrane potential (ΔΨm), mitochondrial respiration and the calcium fluxes were examined. It was observed that Aβ25–35, in the presence of Ca2+, decreased the ΔΨm, the capacity of brain mitochondria to accumulate calcium and led to a complete uncoupling of the respiration. However, the reverse sequence of the peptide Aβ25–35 (Aβ35–25) did not promote the PTP. The alterations promoted by Aβ35–25 and/or Ca2+ could be reversed when Ca2+ was removed by EGTA or when ADP plus oligomycin were present. The pre-treatment with CsA or ADP plus oligomycin prevented the ΔΨm drop and preserved the capacity of mitochondria to accumulate Ca2+. These results suggest that Aβ25–35 can promote the PTP induced by Ca2+.