Exploring the Factor Structure of Neurocognitive Measures in Older Individuals

Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals) was randomly divided into two groups: one for exploratory factor analysis (EFA) and principal component analysis (PCA), to investigate the number of factors underlying the neurocognitive variables; the second to test the “best fit” model via confirmatory factor analysis (CFA). For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components) and two rotation (orthogonal and oblique) methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate.     

Connecting Proline and γ-Aminobutyric Acid in Stressed Plants through Non-Enzymatic Reactions

The accumulation of proline (Pro) in plants exposed to biotic/abiotic stress is a well-documented and conserved response in most vegetal species. Stress conditions induce the overproduction of reactive oxygen species which can lead to cellular damage. In vitro assays have shown that enzyme inactivation by hydroxyl radicals (^·OH) can be avoided in presence of Pro, suggesting that this amino acid could act as an ^·OH scavenger. We applied Density Functional Theory coupled with a polarizable continuum model to elucidate how Pro reacts with ^·OH. In this work we suggest that Pro reacts favourably with ^·OH by H–abstraction on the amine group. This reaction produces the spontaneous decarboxylation of Pro leading to the formation of pyrrolidin-1-yl. In turn, pyrrolidin-1-yl can easily be converted to Δ¹-pyrroline, the substrate of the enzyme Δ¹-pyrroline dehydrogenase, which produces γ-aminobutyric acid (GABA). GABA and Pro are frequently accumulated in stressed plants and several protective roles have been assigned to these molecules. Thereby we present an alternative non-enzymatic way to synthetize GABA under oxidative stress. Finally this work sheds light on a new beneficial role of Pro accumulation in the maintenance of photosynthetic activity.     

In vitro induction of haploid,diploid and triploid plantlets by anther culture of Iochroma warscewiczii Regel

Pollen of Iochroma warscewiczii Regel (Solanaceae) produced embryogenic calli or embryos inside anthers cultured on Nitsch & Nitsch medium. Two distinct pathways could be recognized in this process, one involving mainly the vegetative cell, and the second starting with two equal cells in the pollen grains.In all media tested, androgenesis initiation was highest when anthers contained pollen at the first mitosis, or close to it, at inoculation. High sucrose (7%) and calcium (11.3 mM) concentrations were found to be highly desirable for the induction of androgenesis in this species. Addition of benzylaminopurine (0.5 mg l^–1) to the culture medium seems to slightly improve callus or embryo production. When all three factors were present at optimal concentrations as much as 13.9% of inoculated anthers were found to be embryogenic.Plantlet development from pollen embryos required lower sucrose (3%) and a combination of 0.1 mg l^–1 benzylaminopurine and 0.5 mg l^–1 gibberellic acid in the culture medium. Cytological analysis of 55 regenerated plantlets showed that about 49% were haploids, but diploid (ca. 49%) and triploid (ca. 2%) plants were also obtained.     

Deposition of BaSO4 in the tight junctions of amphibian epithelia causes their opening; apical Ca2+ reverses this effect

Selective deposition of BaSO₄ in the tight junctions (TJs) of frog skins led to profound and reversible functional alterations of these structures, as revealed by changes of tissue conductance (G), clamping current (I), and fluxes of extracellular markers (sulfate (J^SO ₄) and sucrose (J^SUC)). Experiments were performed with nominally Ca²⁺ -free simple salt solutions on the apical side (usually KCl) and Na₂SO₄-Ringer on the inner side of skins. The deposition of BaSO₄ in the TJs was obtained by diffusion and/or migration through the paracellular path of Ba²⁺ from the apical solution and SO ₄ ^2– from the inner solution. A brief presence (2 to 6 min) of apical Ba²⁺ (Ba²⁺ pulse) is followed (i.e., when Ba²⁺ is removed from the apical fluid) by a large increase of G, I, J^SO ₄ and J^SUC, above pre-Ba²⁺ levels. These attain a steady state within 15 to 30 min (overshoot phase), characterizing a conspicuous increase of the paracellular permeability. During the overshoot phase, a second Ba²⁺ pulse blocks the paracellular route while apical Ba²⁺ is present, leading to a new and larger overshoot when the Ba²⁺ pulse is terminated. Addition of apical Ca²⁺ triggers the resealing of the TJs, resulting in a full recovery of G, I, J^SO ₄ and J^SUC. This Ca²⁺ -induced recovery persists when apical Ca²⁺ is removed. The presence of a normal Ca²⁺ concentration in the inner bathing Ringer does not induce the recovery process. Tissues remain viable after being submitted to the Ba²⁺ treatment and the subsequent overshoot. Experiments performed in the urinary bladder of Rana catesbeiana and skins and urinary bladders of Bufo marinus indicate that Ba²⁺ effect can also be elicited in these tissues. The above results seem to report general properties of the TJs. Incidentally, they warn about the use of Ba²⁺ as an ion channel blocker in epithelial membranes in association with SO ₄ ^2– -containing solutions on the contralateral side.This project was supported by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (91/0293-7 to F.L.V., and 90/1788-1 to A.S.), and Conselho Nacional de Desenvolvimento Científico e Tecnológico (410068/90-0 and 303633-85/BF to F.L.V.). J.A.C. received a doctoral fellowship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior/Fundação Universidade do Rio Grande. We thank Dr. Alice T. Ferreira for help in the measurements of free Ca²⁺ concentration.     

Conservation and alteration of HLA-B27-specific T cell epitopes on mouse cells. Implications for peptide-mediated alloreactivity.

Alloreactive CTL responses generate a great variety of clonal specificities. Such diversity may be related to recognition of multiple peptides constitutively bound to any given MHC alloantigen. Among human alloreactive CTL, only a fraction of the clones lyse mouse P815 cells expressing class I HLA proteins. In this study the fine specificity of HLA-B27 allorecognition on human or mouse cells by five human HLA-B27-specific CTL clones was comparatively analyzed. This was done to examine what degree of variation in epitope structure is compatible with recognition of HLA Ag on mouse cells. Nine site-specific HLA-B27 mutants were expressed on both human and mouse cells, after DNA-mediated gene transfer, to construct two analogous series of target cells. The reaction patterns of four of the five CTL clones with these cell panels were compatible with conservation of their corresponding epitopes upon expression of HLA-B27 on mouse cells. The reaction pattern of the fifth clone was different with either cell panel, indicating that its epitope was structurally altered on mouse cells. It also suggested a selectively increased expression of the determinant on these cells. The results suggest that most of the epitopes recognized by allospecific CTL clones reacting across species are either independent of any bound peptide or involve identical peptides from both cell types. However, some of these clones recognize alloantigen-bound peptides that are somewhat different in structure depending on the cell type, and may be expressed at the mouse cell surface in greater amounts. Such peptides could arise from related proteins in both species, and be polymorphic as a result of phylogenetic divergence.     

Gold Toning Improves the Visualization of Nucleolar Organizer Regions in Paraffin Embedded Tissues

A modification of the silver colloid technique for staining nucleolar organizer regions in paraffin embedded tissues is described. This modification involves the application of a gold toning step with subsequent gold reduction, if necessary, following incubation of sections in the standard silver colloid solution. Silver stained nucleolar organizer regions (AgNORs) in toned sections are more sharply delineated when compared to untoned controls. in high grade tumors the addition of the toning step results in significantly higher AgNOR counts due to the ability to discriminate more easily individual AgNORs in argyrophilic aggregates within the nucleus. It is recommended, because of enhanced visualization, that this modification of the silver colloid technique be used in studies involving quantification of AgNORs in tissue sections.     

Physiographic and climatic events in the Chihuahuan Desert lead to the speciation and distinct demographic patterns of two sister Sceloporus lizards

The biogeographic history of the Chihuahuan Desert is known to be complex, and there is evidence of the effects of physiographic and climatic events in species diversification and demographic population changes in many taxa. Here, using DNA sequence data, we studied the influence of the physiographic and climatic events that occurred in the Chihuahuan Desert during the Pliocene–Pleistocene transition on the speciation and evolutionary history of the sister lizard species Sceloporus cyanostictus and S. gadsdeni. First, based on mtDNA and nDNA sequences, we estimated the divergence times of the sister species. Then, based on mtDNA sequences, we investigated the demographic history of both species within a phylogeographic framework. The divergence time was inferred to be 1.48 Mya, date that corresponds to the existence of a large lake in the Mapimian subprovince, between the current geographic locations of S. cyanostictus and S. gadsdeni. This lake could have acted as a barrier, leading to the speciation of both species. For the demographic history of the two species, we identified two distinct patterns: the population expansion of S. gadsdeni within the Last Glacial Maximum and the potential population decline of S. cyanostictus. Our results can be used as a guide for the study of other aspects that could be critical to developing conservation actions that ensure the survival of not only S. gadsdeni and S. cyanostictus, but also other co‐occurring lizard species.     

Multilocus and morphological analysis of south-eastern Iberian Wall lizards (Squamata,Podarcis)

The phylogenetic relationships among the wall lizards of the Podarcis hispanicus complex that inhabit the south-east (SE) of the Iberian Peninsula and other lineages of the complex remain unclear. In this study, four mitochondrial and two nuclear markers were used to study genetic relationships within this complex. The phylogenetic analyses based on mtDNA gene trees constructed with ML and BI, and a species tree using *BEAST support three divergent clades in this region: the Valencia, Galera and Albacete/Murcia lineages. These three lineages were also corroborated in species delimitation analyses based on mtDNA using bPTP, mPTP, GMYC, ABGD and BAPS. Bayesian inference species delimitation method (BPP) based on both nuclear data and a combined data set (mtDNA + nuclear) showed high posterior probabilities for these three SE lineages (≥0.94) and another Bayesian analysis (STACEY) based on combined data set recovered the same three groups in this region. Divergence time dating of the species tree provided an estimated divergence of the Galera lineage from the other SE group (Podarcis vaucheri, (Albacete/Murcia, Valencia)) at 12.48 Ma. During this period, the Betic–Rifian arc was isolated, which could have caused the isolation of the Galera form distributed to the south of the Betic Corridor. Although lizards from the Albacete/Murcia and Galera lineage are morphologically similar, they clearly represent distinct genetic lineages. The noteworthy separation of the Galera lineage enables us to conclude that this lineage must be considered as a new full species.     

High T cell epitope sharing between two HLA-B27 subtypes (B*2705 and B*2709) differentially associated to ankylosing spondylitis.

HLA-B*2705 is strongly associated with ankylosing spondylitis (AS) and reactive arthritis. In contrast, B*2709 has been reported to be more weakly or not associated to AS. These two molecules differ by a single amino acid change: aspartic acid in B*2705 or histidine in B*2709 at position 116. In this study, we analyzed the degree of T cell epitope sharing between the two subtypes. Ten allospecific T cell clones raised against B*2705, 10 clones raised against B*2703 but cross-reactive with B*2705, and 10 clones raised against B*2709 were examined for their capacity to lyse B*2705 and B*2709 target cells. The anti-B*2705 and anti-B*2703 CTL were peptide dependent as demonstrated by their failure to lyse TAP-deficient B*2705-T2 transfectant cells. Eight of the anti-B*2705 and five of the anti-B*2703 CTL clones lysed B*2709 targets. The degree of cross-reaction between B*2705 and B*2709 was donor dependent. In addition, the effect of the B*2709 mutation (D116H) on allorecognition was smaller than the effect of the other naturally occurring subtype change at this position, D116Y. These results demonstrate that B*2705 and B*2709 are the antigenically closest HLA-B27 subtypes. Because allospecific T cell recognition is peptide dependent, our results imply that the B*2705- and B*2709-bound peptide repertoires are largely overlapping. Thus, to the extent to which linkage of HLA-B27 with AS is related to the peptide-presenting properties of this molecule, our results would imply that peptides within a relatively small fraction of the HLA-B27-bound peptide repertoire influence susceptibility to this disease.