O PAPEL DO TIPO DE RESPOSTA NA FORMA DO CONTRASTE NEGATIVO OU DA INDUÇÃO POSITIVA EM RATOS

Rats may decrease (negative contrast) or increase (positive induction) their rate of responding for 1% sucrose reinforcement when 32% sucrose reinforcement is upcoming under different conditions. Previous research suggests that which effect occurs may depend on what motor response (i.e., licking vs. press a lever) isrequired to obtain the sucrose. The present study investigated this idea by having subjects make different responses in different halves of the session. Subjects either licked or pressed a lever for 1% sucrose reinforcement in the first half of the session. They then made the alternative response for 1% or 32% sucrose reinforcement, in different conditions, in the second half. In Experiment 1, both licking and lever pressing were operant responses. In Experiment 2, licking was strictly a consummatory response. Results showed that upcoming 32% sucrose tended to decrease responding for 1% sucrose in the first half of the session regardless of the response required in either half. Positive induction was never observed. The present results question whether type of motor response is a key factor in whether contrast or induction is observed. Instead, they suggest that the location that thesubstances are delivered and consumed is critical. Ultimately, understanding when one effect or the other will occur will enhance our understanding of eating-related behavior.Key words: negative contrast, positive induction, reinforcement, lever press, rat.Ratos podem diminuir (contraste negativo) ou aumentar (indução positiva) sua taxa de respostas reforçadas com solução de sacarose a 1% quando reforçamento com solução de sacarose a 32% é iminente, em diferentes condições. Pesquisa anterior sugere que o efeito que ocorrerá pode depender de qual resposta motora (lamber versus pressionar a barra, por exemplo) é requerida para obter a solução de sacarose. O presente estudo investigou esse problema fazendo os sujeitos emitirem respostas diferentes em cada uma das metades das sessões. Os sujeitos ou lambiam ou pressionavam uma barra e produziam reforçamento de solução de sacarose a 1% na primeira metade da sessão. Eles emitiam, então, a resposta alternativa, reforçada por solução de sacarose a 1% ou 32%, em condições diferentes, na segunda metade da sessão. No Experimento 1, ambos, lamber e pressionar a barra eram respostas operantes. No Experimento 2, lamber foi uma resposta estritamente consumatória. Os resultados mostraram que a solução de sacarose a 32% iminente tendeu a diminuir o responder por solução de sacarose a 1% na primeira metade da sessão, independentemente de qual era a resposta requerida na outra metade. Indução positiva nunca foi observada. Os resultados presentes questionam se o tipo de resposta motora seria um fator chave para a observação de contraste ou de indução, sugerindo, ao contrário, que o local em que as substâncias são liberadas e consumidas seja crítico. Compreender quando um efeito ou outro vai ocorrer aumentará nossa compreensão do comportamento relacionado com alimentar-se. Palavras-chave: Contraste negativo, indução positiva, reforçamento, pressão à barra, rato

Cerebral Glucose Metabolism: Differences in Wernicke's, Broca's, and Conduction Aphasia

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Left Prefrontal Glucose Hypometabolism in Aphasia

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Tumor-associated endothelial cells display GSTP1 and RARβ2 promoter methylation in human prostate cancer

BACKGROUND: A functional blood supply is essential for tumor growth and proliferation. However, the mechanism of blood vessel recruitment to the tumor is still poorly understood. Ideally, a thorough molecular assessment of blood vessel cells would be critical in our comprehension of this process. Yet, to date, there is little known about the molecular makeup of the endothelial cells of tumor-associated blood vessels, due in part to the difficulty of isolating a pure population of endothelial cells from the heterogeneous tissue environment. METHODS: Here we describe the use of a recently developed technique, Expression Microdissection, to isolate endothelial cells from the tumor microenvironment. The methylation status of the dissected samples was evaluated for GSTP1 and RARβ2 promoters via the QMS-PCR method. RESULTS: Comparing GSTP1 and RARβ2 promoter methylation data, we show that 100% and 88% methylation is detected, respectively, in the tumor areas, both in epithelium and endothelium. Little to no methylation is observed in non-tumor tissue areas. CONCLUSION: We applied an accurate microdissection technique to isolate endothelial cells from tissues, enabling DNA analysis such as promoter methylation status. The observations suggest that epigenetic alterations may play a role in determining the phenotype of tumor-associated vasculature

Synergistic use of plant-prokaryote comparative genomics for functional annotations

<p>Abstract</p> <p>Background</p> <p>Identifying functions for all gene products in all sequenced organisms is a central challenge of the post-genomic era. However, at least 30-50% of the proteins encoded by any given genome are of unknown or vaguely known function, and a large number are wrongly annotated. Many of these ‘unknown’ proteins are common to prokaryotes and plants. We set out to predict and experimentally test the functions of such proteins. Our approach to functional prediction integrates comparative genomics based mainly on microbial genomes with functional genomic data from model microorganisms and post-genomic data from plants. This approach bridges the gap between automated homology-based annotations and the classical gene discovery efforts of experimentalists, and is more powerful than purely computational approaches to identifying gene-function associations.</p> <p>Results</p> <p>Among Arabidopsis genes, we focused on those (2,325 in total) that (i) are unique or belong to families with no more than three members, (ii) occur in prokaryotes, and (iii) have unknown or poorly known functions. Computer-assisted selection of promising targets for deeper analysis was based on homology-independent characteristics associated in the SEED database with the prokaryotic members of each family. In-depth comparative genomic analysis was performed for 360 top candidate families. From this pool, 78 families were connected to general areas of metabolism and, of these families, specific functional predictions were made for 41. Twenty-one predicted functions have been experimentally tested or are currently under investigation by our group in at least one prokaryotic organism (nine of them have been validated, four invalidated, and eight are in progress). Ten additional predictions have been independently validated by other groups. Discovering the function of very widespread but hitherto enigmatic proteins such as the YrdC or YgfZ families illustrates the power of our approach.</p> <p>Conclusions</p> <p>Our approach correctly predicted functions for 19 uncharacterized protein families from plants and prokaryotes; none of these functions had previously been correctly predicted by computational methods. The resulting annotations could be propagated with confidence to over six thousand homologous proteins encoded in over 900 bacterial, archaeal, and eukaryotic genomes currently available in public databases.</p

Mitochondrial and plastidial COG0354 proteins have folate-dependent functions in iron–sulphur cluster metabolism

COG0354 proteins have been implicated in synthesis or repair of iron/sulfur (Fe/S) clusters in all domains of life, and those of bacteria, animals, and protists have been shown to require a tetrahydrofolate to function. Two COG0354 proteins were identified in Arabidopsis and many other plants, one (At4g12130) related to those of α-proteobacteria and predicted to be mitochondrial, the other (At1g60990) related to those of cyanobacteria and predicted to be plastidial. Grasses and poplar appear to lack the latter. The predicted subcellular locations of the Arabidopsis proteins were validated by in vitro import assays with purified pea organelles and by targeting assays in Arabidopsis and tobacco protoplasts using green fluorescent protein fusions. The At4g12130 protein was shown to be expressed mainly in flowers, siliques, and seeds, whereas the At1g60990 protein was expressed mainly in young leaves. The folate dependence of both Arabidopsis proteins was established by functional complementation of an Escherichia coli COG0354 (ygfZ) deletant; both plant genes restored in vivo activity of the Fe/S enzyme MiaB but restoration was abrogated when folates were eliminated by deleting folP. Insertional inactivation of At4g12130 was embryo lethal; this phenotype was reversed by genetic complementation of the mutant. These data establish that COG0354 proteins have a folate-dependent function in mitochondria and plastids, and that the mitochondrial protein is essential. That plants retain mitochondrial and plastidial COG0354 proteins with distinct phylogenetic origins emphasizes how deeply the extant Fe/S cluster assembly machinery still reflects the ancient endosymbioses that gave rise to plants

Radiocarbon Analyses Quantify Peat Carbon Losses With Increasing Temperature in a Whole Ecosystem Warming Experiment

Climate warming is expected to accelerate peatland degradation and release rates of carbon dioxide (CO2) and methane (CH4). Spruce and Peatlands Responses Under Changing Environments is an ecosystem-scale climate manipulation experiment, designed to examine peatland ecosystem response to climate forcings. We examined whether heating up to +9 °C to 3 m-deep in a peat bog over a 7-year period led to higher C turnover and CO2 and CH4 emissions, by measuring 14C of solid peat, dissolved organic carbon (DOC), CH4, and dissolved CO2 (DIC). DOC, a major substrate for heterotrophic respiration, increased significantly with warming. There was no 7-year trend in the DI14 C of the ambient plots which remained similar to their DO14 C. At +6.75 °C and +9 °C, the 14C of DIC, a product of microbial respiration, initially resembled ambient plots but became more depleted over 7 years of warming. We attributed the shifts in DI14 C to the increasing importance of solid phase peat as a substrate for microbial respiration and quantified this shift via the radiocarbon mass balance. The mass-balance model revealed increases in peat-supported respiration of the catotelm depths in heated plots over time and relative to ambient enclosures, from a baseline of 20%–25% in ambient enclosures, to 35%–40% in the heated plots. We find that warming stimulates microorganisms to respire ancient peat C, deposited under prior climate (cooler) conditions. This apparent destabilization of the large peat C reservoir has implications for peatland-climate feedbacks especially if the balance of the peatland is tipped from net C sink to C source. Plain Language Summary Since the end of the last glacial period, about 20 thousand years ago, peatlands have taken up carbon and now store an amount nearly equivalent to the quantity in the atmosphere. Microorganisms consume and respire that peat C releasing it back to the atmosphere as CO2 and CH4. Until now, many studies have shown that microorganisms prefer to consume the most recently fixed carbon and that the deeply buried ancient peat carbon reservoir is relatively stable. However, climate warming is expected to upset that balance. The Spruce and Peatlands Responses Under Changing Environments is large-scale experimental warming of a Minnesota peatland designed to study these effects. We conducted radiocarbon analysis of the peat and the microbially produced CO2 and dissolved organic carbon in ambient and heated areas of the peatland and show that at warmer temperatures more of the ancient peat carbon is being mobilized and respired to CO2. This is troubling as it signifies a positive feedback loop wherein warming stimulates peat to produce more CO2 which further exacerbates climate change