Perfusion alters free zinc levels in the rodent brain.

BACKGROUND: Fixation of brain tissue is a common practice which allows preservation of tissue and aids in preventing structural and chemical abnormalities. However, fixation procedures may disrupt the levels of biometals such as zinc when compared to tissue that is fresh-frozen. Thus, we sought to determine if any differences in free-zinc levels exist between perfused and fresh-frozen tissue. Zinc is an essential biometal critical for cellular communication and memory and exists in both bound and free forms; the latter playing critical roles in synaptic communication. New method: C57BL/6 J mice were divided into two water types: those given lab water and those given water supplemented with 10 ppm zinc carbonate. Perfusion was carried out with 4% paraformaldehyde on half of the animals in each water group to assess the impact on levels of free Zn as measured through Zinpyr-1 fluorescence. RESULTS: There were significant differences in Zn fluorescence values between Zn-supplemented and lab water groups as well as between perfused and fresh-frozen tissues in the dentate gyrus and CA3 regions of the hippocampus, regions critical in learning & memory. Comparison with existing methods: These results show that when determining a method for euthanasia, any future histological techniques involving assessment of metal content should first be considered. CONCLUSIONS: Researchers must be cautious with the way in which tissue is collected and treated since this can lead to misleading conclusions when linking changes in behavior and relative levels of trace metals.

Integrated stress response is critical for gemcitabine resistance in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with marked chemoresistance and a 5-year survival rate of 7%. The integrated stress response (ISR) is a cytoprotective pathway initiated in response to exposure to various environmental stimuli. We used pancreatic cancer cells (PCCs) that are highly resistant to gemcitabine (Gem) and an orthotopic mouse model to investigate the role of the ISR in Gem chemoresistance. Gem induced eIF2 phosphorylation and downstream transcription factors ATF4 and CHOP in PCCs, and these effects occurred in an eIF2α-S51 phosphorylation-dependent manner as determined using PANC-1 cells, and wild type and S51 mutant mouse embryo fibroblasts. Blocking the ISR pathway in PCCs with the ISR inhibitor ISRIB or siRNA-mediated depletion of ATF4 resulted in enhanced Gem-mediated apoptosis. Polyribosomal profiling revealed that Gem caused repression of global translation and this effect was reversed by ISRIB or by expressing GADD34 to facilitate eIF2 dephosphorylation. Moreover, Gem promoted preferential mRNA translation as determined in a TK-ATF4 5'UTR-Luciferase reporter assay, and this effect was also reversed by ISRIB. RNA-seq analysis revealed that Gem upregulated eIF2 and Nrf2 pathways, and that ISRIB significantly inhibited these pathways. Gem also induced the expression of the antiapoptotic factors Nupr1, BEX2, and Bcl2a1, whereas ISRIB reduced their expression. In an orthotopic tumor model using PANC-1 cells, ISRIB facilitated Gem-mediated increases in PARP cleavage, which occurred in conjunction with decreased tumor size. These findings indicate that Gem chemoresistance is enhanced by activating multiple ISR-dependent pathways, including eIF2, Nrf2, Nupr1, BEX2, and Bcl2A1. It is suggested that targeting the ISR pathway may be an efficient mechanism for enhancing therapeutic responsiveness to Gem in PDAC.

Population studies of native grass-endophyte symbioses provide clues for the roles of host jumps and hybridization in driving their evolution.

Fungal endophytes in the genera Epichloë and Neotyphodium, collectively termed the epichloae, have fascinated biologists for decades. These intriguing fungi, also referred to as 'class 1 or clavicipitaceous endophytes', spend the large majority, or even their entire life cycle, within the tissues of their cool-season grass hosts without eliciting any symptoms of infection. While all epichloae reside within the intercellular spaces of aboveground vegetative grass tissues, the species at the symbiotic extreme are known as Neotyphodium, and the intimacy of their interaction extends to the reproductive (flowering) stage. At this point, fungal filaments (hyphae) nondestructively invade the developing ovaries of their host and are incorporated into perfectly viable, healthy seeds. Thus, these endophytes live solely within the tissues of their host plants and are transmitted maternally from generation to generation. A second life history characteristic of interest is that while all Epichloë and some Neotyphodium species are haploid, a great many of the strictly seed-transmitted Neotyphodium spp. are interspecific hybrids. This phenomenon may be critical for the success of these symbioses over longer spans of evolutionary time and will be discussed in greater detail below. A third characteristic, and one of the primary reasons these grass endophytes have received so much attention over the last three decades, is the strong mutualistic nature these relationships often exhibit. In exchange for photosynthetically derived carbon, the endophytes protect their cool-season grass hosts from grazing herbivores and a variety of abiotic stresses. It has been hypothesized that these three biological phenomena are related (Schardl & Craven 2003), perhaps with the former two driving the third, and it is here that the recent article in Molecular Ecology entitled 'Genetic diversity in epichloid endophytes of Hordelymus europaeus suggests repeated host jumps and interspecific hybridizations', by Oberhofer & Leuchtmann (2012), provides critical clues to linking these traits together. While the large majority of studies have focused on documenting the ever-increasing list of mutualistic qualities attributed to these fungi, very few have taken an exhaustive population-level approach to document plant and endophyte genotypes within a naturally occurring system (Faeth et al. 2010; Jani et al. 2010; Tintjer & Rudgers 2006). Such information is crucial to more fully elucidate the factors shaping grass-endophyte symbioses and those often driving these relationships to mutualistic extremes.

A novel test for host-symbiont codivergence indicates ancient origin of fungal endophytes in grasses.

Significant phylogenetic codivergence between plant or animal hosts (H) and their symbionts or parasites (P) indicates the importance of their interactions on evolutionary time scales. However, valid and realistic methods to test for codivergence are not fully developed. One of the systems where possible codivergence has been of interest involves the large subfamily of temperate grasses (Pooideae) and their endophytic fungi (epichloae). These widespread symbioses often help protect host plants from herbivory and stresses and affect species diversity and food web structures. Here we introduce the MRCALink (most-recent-common-ancestor link) method and use it to investigate the possibility of grass-epichloë codivergence. MRCALink applied to ultrametric H and P trees identifies all corresponding nodes for pairwise comparisons of MRCA ages. The result is compared to the space of random H and P tree pairs estimated by a Monte Carlo method. Compared to tree reconciliation, the method is less dependent on tree topologies (which often can be misleading), and it crucially improves on phylogeny-independent methods such as ParaFit or the Mantel test by eliminating an extreme (but previously unrecognized) distortion of node-pair sampling. Analysis of 26 grass species-epichloë species symbioses did not reject random association of H and P MRCA ages. However, when five obvious host jumps were removed, the analysis significantly rejected random association and supported grass-endophyte codivergence. Interestingly, early cladogenesis events in the Pooideae corresponded to early cladogenesis events in epichloae, suggesting concomitant origins of this grass subfamily and its remarkable group of symbionts. We also applied our method to the well-known gopher-louse data set.

Comparison of biochemical and molecular methods for the identification of bacterial isolates associated with failed loggerhead sea turtle eggs.

AIMS: Comparison of biochemical vs molecular methods for identification of microbial populations associated with failed loggerhead turtle eggs. METHODS AND RESULTS: Two biochemical (API and Microgen) and one molecular methods (16s rRNA analysis) were compared in the areas of cost, identification, corroboration of data with other methods, ease of use, resources and software. The molecular method was costly and identified only 66% of the isolates tested compared with 74% for API. A 74% discrepancy in identifications occurred between API and 16s rRNA analysis. The two biochemical methods were comparable in cost, but Microgen was easier to use and yielded the lowest discrepancy among identifications (29%) when compared with both API 20 enteric (API 20E) and API 20 nonenteric (API 20NE) combined. A comparison of API 20E and API 20NE indicated an 83% discrepancy between the two methods. CONCLUSIONS: The Microgen identification system appears to be better suited than API or 16s rRNA analysis for identification of environmental isolates associated with failed loggerhead eggs. SIGNIFICANCE AND IMPACT OF THE STUDY: Most identification methods are not intended for use with environmental isolates. A comparison of identification systems would provide better options for identifying environmental bacteria for ecological studies.

Neural correlates of processing facial identity based on features versus their spacing.

Adults' expertise in recognizing facial identity involves encoding subtle differences among faces in the shape of individual facial features (featural processing) and in the spacing among features (a type of configural processing called sensitivity to second-order relations). We used fMRI to investigate the neural mechanisms that differentiate these two types of processing. Participants made same/different judgments about pairs of faces that differed only in the shape of the eyes and mouth, with minimal differences in spacing (featural blocks), or pairs of faces that had identical features but differed in the positions of those features (spacing blocks). From a localizer scan with faces, objects, and houses, we identified regions with comparatively more activity for faces, including the fusiform face area (FFA) in the right fusiform gyrus, other extrastriate regions, and prefrontal cortices. Contrasts between the featural and spacing conditions revealed distributed patterns of activity differentiating the two conditions. A region of the right fusiform gyrus (near but not overlapping the localized FFA) showed greater activity during the spacing task, along with multiple areas of right frontal cortex, whereas left prefrontal activity increased for featural processing. These patterns of activity were not related to differences in performance between the two tasks. The results indicate that the processing of facial features is distinct from the processing of second-order relations in faces, and that these functions are mediated by separate and lateralized networks involving the right fusiform gyrus, although the FFA as defined from a localizer scan is not differentially involved.

Molecular identification of the turf grass rapid blight pathogen.

Rapid blight is a newly described disease on turf grasses, primarily found on golf courses using suboptimal water for irrigation purposes. On the basis of shared morphological characteristics, it has been proposed that the rapid blight pathogen belongs to a genus of stramenopiles, Labyrinthula, which had been known to cause disease of marine plants only. We have collected 10 isolates from four species of turf grass in five states and sequenced portions of the SSU (18S) rDNA gene from each to provide a definitive taxonomic placement for rapid blight pathogens. We also included sequences from Labyrinthuloides yorkensis, Schizochytrium aggregatum, Aplanochytrium sp., Thraustochytrium striatum, Achlya bisexualis and several nonturf-grass isolates of Labyrinthula. We found that rapid blight isolates indeed are placed firmly within the genus Labyrinthula and that they lack detectable genetic diversity in the 18S rDNA region. We propose that the rapid blight pathogens share a recent common ancestor and might have originated from a single, infected population.

Prevalence of interspecific hybrids amongst asexual fungal endophytes of grasses.

Epichloë endophytes are fungal symbionts of grasses that span a continuum including asexual mutualists that are vertically transmitted, obligately sexual pathogens that are horizontally transmitted, and mixed-strategy symbionts with both mutualistic and pathogenic capabilities. Here we show that processes of genome evolution differ markedly for the different symbiont types. Genetic and phylogenetic analysis was conducted of a broad taxonomic, ecological and geographical sample of sexual and asexual isolates, in which were identified and sequenced alleles of genes for beta-tubulin (tub2) and translation elongation factor 1-alpha (tef1), and microsatellite alleles were identified by length polymorphisms. The majority of asexual isolates had two or three alleles of most loci, but every sexual isolate had only single alleles for each locus. Phylogenetic analysis of tub2 and tef1 indicated that in all instances of multiple alleles in an isolate, the alleles were derived from different sexual species. It is concluded that, whereas horizontally transmissible species had haploid genomes and speciation occurred cladistically, most of the strictly seedborne mutualists were interspecific hybrids with heteroploid (aneuploid or polyploid) genomes. Furthermore, the phylogenetic evidence indicated that, in at least some instances, hybridization followed rather than caused evolution of the strictly seedborne habit. Therefore, the abundance of hybrid species among grass endophytes, and their prevalence in many host populations suggests a selective advantage of hybridization for the mutualistic endophytes.

Interspecific hybridization in plant-associated fungi and oomycetes: a review.

Fungi (kingdom Mycota) and oomycetes (kingdom Stramenopila, phylum Oomycota) are crucially important in the nutrient cycles of the world. Their interactions with plants sometimes benefit and sometimes act to the detriment of humans. Many fungi establish ecologically vital mutualisms, such as in mycorrhizal fungi that enhance nutrient acquisition, and endophytes that combat insects and other herbivores. Other fungi and many oomycetes are plant pathogens that devastate natural and agricultural populations of plant species. Studies of fungal and oomycete evolution were extraordinarily difficult until the advent of molecular phylogenetics. Over the past decade, researchers applying these new tools to fungi and oomycetes have made astounding new discoveries, among which is the potential for interspecific hybridization. Consequences of hybridization among pathogens include adaptation to new niches such as new host species, and increased or decreased virulence. Hybrid mutualists may also be better adapted to new hosts and can provide greater or more diverse benefits to host plants.

Multiple phosphorylation of rhodopsin and the in vivo chemistry underlying rod photoreceptor dark adaptation.

Dark adaptation requires timely deactivation of phototransduction and efficient regeneration of visual pigment. No previous study has directly compared the kinetics of dark adaptation with rates of the various chemical reactions that influence it. To accomplish this, we developed a novel rapid-quench/mass spectrometry-based method to establish the initial kinetics and site specificity of light-stimulated rhodopsin phosphorylation in mouse retinas. We also measured phosphorylation and dephosphorylation, regeneration of rhodopsin, and reduction of all-trans retinal all under identical in vivo conditions. Dark adaptation was monitored by electroretinography. We found that rhodopsin is multiply phosphorylated and then dephosphorylated in an ordered fashion following exposure to light. Initially during dark adaptation, transduction activity wanes as multiple phosphates accumulate. Thereafter, full recovery of photosensitivity coincides with regeneration and dephosphorylation of rhodopsin.

trans-1-[(2-Phenylcyclopropyl)methyl]-4-arylpiperazines: mixed dopamine D(2)/D(4) receptor antagonists as potential antipsychotic agents.

The dopaminergic receptor profile of a series of trans-1-[(2-phenylcyclopropyl)methyl]-4-arylpiperazines was examined. Aromatic substitution patterns were varied with the goal of identifying a compound having affinities for the D(2) and D(4) receptors in a ratio similar to that observed for the atypical neuroleptic clozapine. The compounds (1S, 2S)-trans-1-[(2-phenylcyclopropyl)methyl]-4-(2, 4-dichlorophenyl)piperazine (5m) and (1S, 2S)-trans-1-[(2-phenylcyclopropyl)methyl]-4-(2, 4-dimethylphenyl)piperazine (5t) were selected for functional antagonists at D(2) and D(4) receptors and had a D(2)/D(4) ratio approximating that of clozapine; they proved inactive in behavioral tests of antipsychotic activity.

Mental imagery of faces and places activates corresponding stiimulus-specific brain regions.

What happens in the brain when you conjure up a mental image in your mind's eye? We tested whether the particular regions of extrastriate cortex activated during mental imagery depend on the content of the image. Using functional magnetic resonance imaging (fMRRI), we demonstrated selective activation within a region of cortex specialized for face perception during mental imagery of faces, and selective activation within a place-selective cortical region during imagery of places. In a further study, we compared the activation for imagery and perception in these regions, and found greater response magnitudes for perception than for imagery of the same items. Finally, we found that it is possible to determine the content of single cognitive events from an inspection of the fMRI data from individual imagery trials. These findings strengthen evidence that imagery and perception share common processing mechanisms, and demonstrate that the specific brain regions activated during mental imagery depend on the content of the visual image.

Using statistical process control to demonstrate the effect of operational interventions on quality indicators in the emergency department.

When our emergency department (ED) initiated a continuous quality improvement (CQI) program, we selected as a quality indicator the percentage of patients leaving without being seen (LWBS) by a physician. Because the primary reason for LWBS patients was determined to be dissatisfaction with waiting time, we devised four interventions in clinical operations to decrease delays in patient flow through the ED. Statistical process control (SPC) methodology was then used to assess the effect of these interventions. Because baseline data were available, we constructed control charts of the percentage of LWBS patients versus consecutive months beginning in January 1990 with the mean percentage of LWBS patients and upper and lower control limits. Postintervention data, plotted using control statistics from the baseline period, demonstrated sustained special-cause variation, indicating a fundamental change in the overall system. A new control chart was then constructed using postintervention data. A significantly lowered mean percentage LWBS and a narrowed control limit range were observed, leading to the conclusion that the interventions improved the quality of care as measured by a reduction in percentage LWBS.

fMRI evidence for objects as the units of attentional selection.

Contrasting theories of visual attention emphasize selection by spatial location, visual features (such as motion or colour) or whole objects. Here we used functional magnetic resonance imaging (fMRI) to test key predictions of the object-based theory, which proposes that pre-attentive mechanisms segment the visual array into discrete objects, groups, or surfaces, which serve as targets for visual attention. Subjects viewed stimuli consisting of a face transparently superimposed on a house, with one moving and the other stationary. In different conditions, subjects attended to the face, the house or the motion. The magnetic resonance signal from each subject's fusiform face area, parahippocampal place area and area MT/MST provided a measure of the processing of faces, houses and visual motion, respectively. Although all three attributes occupied the same location, attending to one attribute of an object (such as the motion of a moving face) enhanced the neural representation not only of that attribute but also of the other attribute of the same object (for example, the face), compared with attributes of the other object (for example, the house). These results cannot be explained by models in which attention selects locations or features, and provide physiological evidence that whole objects are selected even when only one visual attribute is relevant.

Structural and functional brain asymmetries in human situs inversus totalis.

OBJECTIVE: To determine whether individuals with situs inversus totalis (SI), a condition in which there is a mirror-image reversal of asymmetric visceral organs, have alterations in brain asymmetries. BACKGROUND: The human brain is asymmetric in structure and function. Although correlations between anatomic asymmetries and functional lateralization in human brain have been demonstrated, it has been difficult to further analyze them. Characterization of asymmetries of brain structure and function in SI might advance the understanding of these relationships. METHODS: Using anatomic and functional MRI techniques, we analyzed asymmetries in the brains of three individuals with SI. RESULTS: Two major anatomic asymmetries of the cerebral hemispheres, the frontal and occipital petalia, were reversed in individuals with SI. In contrast, SI subjects had left cerebral hemisphere language dominance on functional MRI analysis as well as strong right-handedness. CONCLUSION: These observations suggest that the developmental factors determining anatomic asymmetry of the cerebral petalia and viscera are distinct from those producing the functional lateralization of language.

Auditory and visual word processing studied with fMRI.

Brain activations associated with semantic processing of visual and auditory words were investigated using functional magnetic resonance imaging (fMRI). For each form of word presentation, subjects performed two tasks: one semantic, and one nonsemantic. The semantic task was identical for both auditory and visual presentation: single words were presented and subjects determined whether the word was concrete or abstract. In the nonsemantic task for auditory words, subjects determined whether the word had one syllable or multiple syllables. In the nonsemantic task for visual words, subjects determined whether the word was presented in lower case or upper case. There was considerable overlap in where auditory and visual word semantic processing occurred. Visual and auditory semantic tasks both activated the left inferior frontal (BA 45), bilateral anterior prefrontal (BA 10, 46), and left premotor regions (BA 6) and anterior SMA (BA 6, 8). Left posterior temporal (middle temporal and fusiform gyrus) and predominantly right-sided cerebellar activations were observed during the auditory semantic task but were not above threshold during visual word presentation. The data, when averaged across subjects, did not show obligatory activation of left inferior frontal and temporal language areas during nonsemantic word tasks. Individual subjects showed differences in the activation of the inferior frontal region while performing the same task, even though they showed similar response latency and accuracy.

Local cerebral blood flow during the first hour following acute ligation of multiple arterioles in rat whisker barrel cortex.

The objectives are to measure the early time-course of the flows of blood, red cells, and plasma in brain tissue destined to infarct following arterial occlusion. The flux of fluorescent red blood cells (fRBCs) through venules and the arteriovenous transit times (AVTT) of fluorescein-labeled plasma albumin were periodically monitored in anesthetized adult Wistar rats before and up to 60 min after permanent ligations of several small branches of the middle cerebral artery. Of note, fRBC is a function of venular erythrocyte flow and volume, whereas AVTT is a function of plasma flow and volume in visible arteriole-capillary-venule units. In another group of anesthetized rats, local cerebral blood flow (ICBF) was measured 1 h after permanent arterial occlusion by [14C]iodoantipyrine (IAP) autoradiography. With this model of focal ischemia, the lesion is highly reproducible and involves part of the whisker barrel cortex. Infarction of this area was observed in 12 of 13 rats. From 10 to 60 min after arterial occlusion, AVTT was nearly four times longer in the ischemic barrel cortex than at the same site before ligations, and fRBC flux was 25%. Neither parameter changed appreciably over this time. After 60 min of ischemia, ICBF on the ipsilateral barrel cortex was 18% of that on the contralateral side and 15% of the sham control value for the same area of the barrel cortex. Since whole blood flow in the ischemic barrel cortex was < 20% of normal at 60 min and AVTT and fRBC flux were essentially constant from 10 to 60 min, the rates of plasma and red cell flows were similarly depressed during the first hour of arteriolar occlusion. In conclusion, such lowering of red cell, plasma, and blood flows produced consistent infarctions in the barrel cortex.

A functional magnetic resonance imaging study of auditory vigilance with low and high information processing demands.

This study identified the brain activations associated with auditory vigilance tasks, using functional magnetic resonance imaging. We created auditory continuous performance tests (CPTs) in which a demanding task (working memory task) was made more difficult than a simple vigilance task by increasing working memory and interference filtering demands. Two cohorts of normal male controls performed significantly worse on the working memory CPT than on the vigilance task. Compared to the vigilance task, performance of the working memory task produced significant signal change in lateral and medial prefrontal cortex, precentral cortex, temporal lobe, including insula and hippocampus, parietal-occipital cortex, cingulate, thalamus, and superior colliculus. Performance and degree of activation was associated with an estimate of IQ. Further research should clarify the contributions of working memory and interference filtering to the activated network.

Reproducibility of fMRI results across four institutions using a spatial working memory task.

Four U.S. sites formed a consortium to conduct a multisite study of fMRI methods. The primary purpose of this consortium was to examine the reliability and reproducibility of fMRI results. FMRI data were collected on healthy adults during performance of a spatial working memory task at four different institutions. Two sets of data from each institution were made available. First, data from two subjects were made available from each site and were processed and analyzed as a pooled data set. Second, statistical maps from five to eight subjects per site were made available. These images were aligned in stereotactic space and common regions of activation were examined to address the reproducibility of fMRI results when both image acquisition and analysis vary as a function of site. Our grouped and individual data analyses showed reliable patterns of activation in dorsolateral prefrontal cortex and posterior parietal cortex during performance of the working memory task across all four sites. This multisite study, the first of its kind using fMRI data, demonstrates highly consistent findings across sites.