Lower Breakpoints Research Articles

High Recombination Activating Gene (RAG) Expression and RAG Mediated Recombination Is Associated with Oncogenic Rearrangement Observed with Tyrosine Kinase Inhibitor Resistant CML

BackgroundPatients with chronic myeloid leukemia (CML) who develop blast crisis are resistant to TKI therapy. A key focus in CML research is the identification of genetic factors that promote blast crisis and TKI resistance. By using an integrative genomic approach we recently reported frequent structural variation in CML patients, particularly at lymphoid blast crisis (LBC) (Blood, 2018). Developing lymphocytes are uniquely equipped with a molecular toolkit capable of programmed DNA damage and structural variant formation; the V(D)J recombination pathway. Recombination activating genes (RAG1 and RAG2) are involved in cleavage and recombination of immunoglobulin genes to provide diversity in antibodies and T cell receptors. Off target RAG activity is reported to occur in lymphoid malignancies and cause oncogenic structural rearrangements. However, RAG expression and the extent of RAG mediated structural variation in CML are largely uncharacterized.AimTo elucidate the role of RAG mediated recombination as a source of oncogenic structural rearrangement in CML.MethodsIn a study of samples of 49 patients at chronic phase (CP) diagnosis (Dx), 20 at LBC and 19 at myeloid blast crisis (MBC), we performed whole exome sequencing and/or RNAseq. Bioinformatic analyses included fusion detection (Manta & STAR), gene expression analysis (EdgeR), and copy number variation analysis (in house developed tool). Unsupervised motif detection of sequences surrounding breakpoints was performed with MEME, and fusions were visualized with Jcircos. To identify off target RAG mediated mutation we interrogated the breakpoints of structural variants, excluding those associated with the Philadelphia translocation and those solely involving antigen receptor gene rearrangement.Results33 structural variants were identified in 22 patients with samples at Dx and/or blast crisis involving genes regularly mutated in hematologic malignancy such as MLL, MECOM, RUNX1 and IKZF1. Differential expression analysis between patients at Dx, MBC and LBC revealed >1000 genes that were differentially expressed, P<0.001. Amongst the most upregulated genes at LBC were RAG1, RAG2 and DNTT, reflected in the most enriched gene ontology: V(D)J recombination. V(D)J recombination genes were sufficient alone in stratifying LBC samples from CP Dx and MBC [Figure 1A]. Furthermore, RAG expression was detectably elevated at Dx in most patients who subsequently developed LBC [Figure 1B].To identify off target RAG mediated structural variation, we interrogated the sequence surrounding breakpoints of the 33 identified structural variants (66 breakpoints) that were separated into groups of high (n=40) and low (n=26) RAG expression. The canonical heptamer CACAGTG recombination signal sequence (RSS) was enriched only at breakpoints in the high RAG group with sequences from 31/40 breakpoints making up the motif [Figure 1C]. The comparable group of low RAG breakpoints were not enriched for the motif. Another indicator of RAG involvement is the addition of non-template nucleotides at the breakpoint, consistent with DNTT nucleotidyl-transferase activity. This was detected almost exclusively at breakpoints in patients with high RAG, 16/20 structural variants, compared to 1/13 with low RAG.There was an association between high RAG expression and structural variants bearing the RAG RSS motif at breakpoints with nucleotide additions. The most frequently observed of these were intragenic deletions of IKZF1 in 7 patients, including 3 at Dx with subsequent LBC, 3 at LBC and 1 at MBC. A number of novel structural variants also had the RAG recombination signature: IKZF1-IGK fusion, RUNX1 deletion and recurrent HBS1L-MYB intergenic locus deletion.RAG mediated structural variation was further investigated on a genomic level using putative low level fusions identified from RNAseq. By assessing the immunoglobulin/T cell receptor genes, as known sites of RAG activity, we found enrichment of interchromosomal fusions involving these genes in samples with high RAG, compared to Dx and MBC with low RAG [Figure 1D]. An agnostic motif enrichment search at sequences surrounding putative fusions showed enrichment of a motif resembling the recombination signal sequence.ConclusionOur results implicate RAG as a driver of structural variation and the formation of novel oncogenic rearrangements in CML. [Display omitted] DisclosuresHughes:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Branford:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Qiagen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Cepheid: Honoraria.

Valorisation of olive mill wastewater by phenolic compounds adsorption: Development and application of a procedure for adsorbent selection

A procedure for the selection of the optimal adsorbent for phenolic compounds (PC) recovery from PC-rich wastes and wastewaters was innovatively proposed and applied to compare 4 neutral resins (Amberlite XAD16N, Optipore SD-2, Amberlite FPX66, Amberlite XAD761) and 1 ion-exchange resin (Amberlite IRA958 Cl) for PC recovery from a Tunisian olive mill wastewater (OMW). In the initial batch isotherm tests a neutral resin (XAD16N) performed best thanks to its high PC sorption capacity (81 mgPC/gdry resin) and PC content in the sorbed product (0.19 gPC/gvolatile solids). Also ion-exchange resin IRA958, used in OH form in this work, resulted interesting thanks to its satisfactory performances and very low cost (8 €/L). These two pre-selected resins were further compared by means of continuous-flow adsorption/desorption tests conducted in a 1-m packed column. The results indicate that if a low (20%) breakpoint is selected, XAD16N leads to a PC-richer sorbed product (0.14 gPC/gvolatile solids) and a higher operating capacity (0.30) than IRA958. Conversely, if a very high (90%) breakpoint is selected, the two resins produce similar desorbed products in terms of both PC content (0.19–0.21 gPC/gvolatile solids) and antioxidant capacity (4.6–4.9 gascorbic acid equivalent/gPC). Resin-specific dynamic desorption procedures led to very high PC desorption yields (87–95%). The identification of the actual PCs present in the final desorbed product indicated for XAD16N a higher capacity to preserve the integrity of the PC mixture of the studied OMW. OMW microfiltration (0.2 μm pore-size) led to a 99.8% suspended solid removal – thus protecting the packed column from potential clogging – with a very low PC loss.

Intravenous cocaine self-administration in a panel of inbred mouse strains differing in acute locomotor sensitivity to cocaine.

Initial sensitivity to drugs of abuse often predicts subsequent use and abuse, but this relationship is not always observed in human studies. Moreover, studies examining the relationship between initial locomotor sensitivity and the rewarding and reinforcing effects of drugs in animal models have also been equivocal. Understanding the relationship between initial drug effects and propensity to continue use, potentially resulting in the development of a substance use disorder, may help to identify key targets for prevention and treatment. We examined intravenous cocaine self-administration in a set of mouse strains that were previously identified to be at the phenotypic extremes for cocaine-induced locomotor activation to determine if initial locomotor sensitivity predicted acquisition, extinction, dose response, or progressive ratio (PR) breakpoint. We selected eight inbred mouse strains based on locomotor sensitivity to 20mg/kg cocaine. These strains, designated as low and high responders, were tested in an intravenous self-administration paradigm that included acquisition of 0.5mg/(kg*inf) under a FR1 schedule, extinction, re-acquisition, dose response to 0.125, 0.25, 0.5, 1, and 2mg/(kg*inf), and progressive ratio. We observed overall differences in self-administration behavior between high and low responders. Low responders self-administered less cocaine and had lower breakpoints under the PR schedule. However, we also observed strain differences within each group. Self-administration in the low responder, LG/J, more closely resembled the behavior of the high-responding group, and the high responder, P/J, had self-administration behavior that more closely resembled the low-responding group. We conclude that acute cocaine-induced locomotor activation does predict self-administration behavior, but in a strain-specific manner. These data support the idea that genetic background influences the relationship among addiction-related behaviors.

Modified first world mortality scores can be used in a regional South African burn service with resource limitations

IntroductionSurvival following a major burn is highly dependent on the availability of scare and expensive resources such as critical care services, modern dressings and access to operating theatres. Scoring systems, which predict mortality have been developed and can be used to identify patients in whom the outlay of these resources is futile. The aim of this study was to analyse the mortality at a regional South African burn service and to see if these scoring models developed in a resource rich environment were applicable to our setting. MethodsConsecutive admissions to the Edendale burn service, South Africa were collected from patient records over a 2-year period from July 2013 to June 2015. Demographic, burn details and final outcome (lived or died) were captured for statistical analysis. Each patient was scored using the Modified Baux, Coste et al., Belgian Outcome of Burn Injury (BOBI) and Abbreviated Burn Severity Index (ABSI) scores. Validation of models and inferential statistics were done to determine new breakpoints more applicable to our sample. ResultsA total of 748 patients were included in the sample, with a mortality rate of 7.1%. The mean Modified Baux score was 27 (range 1–134), with the new breakpoint of 40 predicting 74% of the mortalities compared to the 42% predicted by the old breakpoint of 75. The mean ABSI score was 4 (range 2–15), with a lower break point of 6 predicting 75% of deaths compared to 42% with the old breakpoint of 8.The mean Coste score for the sample was 12 (range 0–100). With a suggested break point of 85 (predicting 50% mortality), only 6% of mortalities were predicted. The new break point of 17 predicted 91% of deaths. The original break point for the BOBI score was 6 (range 0–7). This included 42% of deaths. With a new breakpoint of 1, 74% of deaths were predicted. DiscussionOur data has shown that in our environment a significant number of fatalities occur in patients with potentially salvageable burns, and the breakpoints for the mortality prediction scores such as, the Modified Baux score, Coste et al. score, BOBI and ABSI scores are much lower than high-income countries.However these mortality predictive scores can be used in a resource scarce South African setting to triage patients into risk categories by lowering the breakpoints. This may facilitate early and more aggressive management of high-risk burn patients, improving survival rates, as well as efficient and judicious use of critical care and other resources.

TRH injected into the nucleus accumbens shell releases dopamine and reduces feeding motivation in rats

The thyrotropin-releasing hormone (TRH), an anorexigenic factor that reduces food intake in food-restricted animals, may be involved in motivation for food. Injected centrally, TRH impairs acquisition of food-rewarded behavior. Through the TRH-R1 receptors, TRH injected in the nucleus accumbens increases dopamine content—perhaps the mechanism by which the peptide modulates food motivation. This, however, is still to be demonstrated. We sought to evaluate dopamine release by microdialysis after a TRH injection into the nucleus accumbens shell in free-moving fasted rats. In addition, we assessed dopamine content and turnover by HPLC and the relationship with the motivation for food by analyzing the performance of rats during a progressive-ratio (PR) operant-conditioning test. Finally, we determined serum leptin and triiodothyronine (T3) levels in order to evaluate the animals’ metabolic response to food restriction and the impact of intra-accumbal TRH administration on circulating hormones. Intra-accumbal injections of TRH reduced food intake in food-restricted rats—compared to counterparts treated with saline—, without further decreasing T3 or leptin levels, which dropped due to their dietary regime. TRH-injected rats had lower breaking points on the PR schedule, which indicated lower motivation to eat. Accordingly, compared to saline-treated animals, dopamine release and turnover increased in the nucleus accumbens of TRH-injected rats, a finding that suggests a relationship between motivation for food and TRH-induced release of dopamine.

Differential motivational profiles following adolescent sucrose access in male and female rats

Adolescents are the highest consumers of sugar sweetened drinks. Excessive consumption of such drinks is a likely contributor to the development of obesity and may be associated with enduring changes in the systems involved in reward and motivation. We examined the impact of daily sucrose consumption in young male and female rats (N=12 per group) across the adolescent period on the motivation to perform instrumental responses to gain food rewards as adults. Rats were or were not exposed to a sucrose solution for 2h each day for 28days across adolescence [postnatal days (P) 28–56]. They were then trained as adults (P70 onward) to lever press for a palatable 15% cherry flavored sucrose reward and tested on a progressive ratio (PR) schedule to assess motivation to respond for reinforcement. Female rats exposed to sucrose had higher breakpoints on the PR schedule than controls, whereas male rats exposed to sucrose had lower breakpoints than controls. These results show that consumption of sucrose during adolescence produced sex-specific behavioral changes in responding for sucrose as adults.

Avolition in schizophrenia is associated with reduced willingness to expend effort for reward on a Progressive Ratio task

The current study examined whether effort-cost computation was associated with negative symptoms of schizophrenia (SZ). Participants included outpatients diagnosed with SZ (n=27) and demographically matched healthy controls (n=32) who completed a Progressive Ratio task that required incrementally greater amounts of physical effort to obtain monetary reward. Breakpoint, the point at which participants was no longer willing to exert effort for a certain reward value, was examined as an index of effort-cost computation. There were no group differences in breakpoint for low, medium, or high value rewards on the Progressive Ratio task. However, lower breakpoint scores were associated with greater severity of avolition and anhedonia symptoms in SZ patients. Findings provide further evidence that impaired effort-cost computation is linked to motivational abnormalities in SZ.

Relaxin-3 receptor (Rxfp3) gene deletion reduces operant sucrose- but not alcohol-responding in mice.

The pervasive use of refined sugars in highly accessible, palatable foods and persistent exposure to reinforcing food-associated cues has contributed to overconsumption of sugar-rich diets and the current obesity epidemic in Western society. We have shown previously that brain relaxin-3 mRNA levels positively correlate with sucrose and alcohol intake, and that central antagonism of relaxin-3 receptors (RXFP3) attenuates alcohol self-administration and alcohol-seeking in rats, but food-seeking behaviour and palatable food consumption in mice. To further examine the relationship between motivated appetitive behaviours and relaxin-3/RXFP3 signalling, we investigated the effect of Rxfp3 gene deletion in C57BL/6J mice on sucrose and alcohol self-administration and cue-induced reinstatement (RNST) of sucrose- and alcohol-seeking. Acquisition and maintenance of sucrose and alcohol self-administration was assessed in male wild-type (WT) and Rxfp3 knockout (KO) (C57BL/6J(RXFP3TM1) (/) (DGen) ) littermate mice using fixed ratio (FR) schedules of reinforcement. Mice were subsequently challenged with a progressive ratio (PR) test to measure motivation and, following extinction training, re-exposed to reward-associated cues to evaluate RNST of active lever-responding. Wild-type and Rxfp3 KO mice displayed similar acquisition of FR1 sucrose self-administration, but Rxfp3 KO mice responded less when the instrumental requirement was increased to FR3. These mice also showed a lower breakpoint for sucrose and attenuated cue-induced RNST of sucrose-seeking. Notably, no marked genotype differences in alcohol-responding were observed. In mice, endogenous relaxin-3/RXFP3 signalling promotes self-administration of sucrose under high response requirements and cue-induced RNST of sucrose-seeking, but does not apparently regulate motivation to consume alcohol or alcohol-seeking behaviour.

Temperate Drosophila preserve cardiac function at low temperature

Most insects are chill susceptible and will enter a coma if exposed to sufficiently low temperature. This chill coma has been associated with a failure of the neuromuscular system. Insect heart rate (HR) is determined by intrinsic regulation (muscle pacemaker) with extrinsic (nervous and humoral) input. By examining the continually active heart of five Drosophila species with markedly different cold tolerance, we investigated whether cardiac performance is related to the whole animal critical thermal minimum (CTmin). Further, to separate the effects of cold on extrinsic and intrinsic regulators of HR, we measured HR under similar conditions in decapitated flies as well as amputated abdomens of Drosophila montana. Cardiac performance was assessed from break points in HR–temperature relationship (Arrhenius break point, ABP) and from the HR cessation temperature. Among the five species, we found strong relationships for both the HR-ABP and HR cessation temperatures to whole animal CTmin, such that temperate Drosophila species maintained cardiac function at considerably lower temperatures than their tropical congeners. Hearts of amputated abdomens, with reduced extrinsic input, had a higher thermal sensitivity and a significantly lower break point temperature, suggesting that central neuronal input is important for stimulating HR at low temperatures.

Persistence of limited-transpiration-rate trait in sorghum at high temperature

A limited-transpiration (TRlim) trait has been identified in many crop species, including sorghum (Sorghum bicolor (L.) Moench), that results in restricted transpiration rate under high vapor pressure deficits (VPD). The benefit of TRlim is that under high midday-VPD conditions crop water loss is limited so that there is water conservation and positions the crop to better withstand later-season drought. Previous studies performed at 31°C found that TRlim was commonly expressed among sorghum genotypes. It was also found that those lines with low VPD breakpoints for expression of the TRlim trait exhibited insensitivity in transpiration rate to being fed silver ions. However, it is uncertain how applicable these previous results obtained at 31°C might be at higher temperature that may exist at midday in regions where sorghum is commonly grown. The current study tested for the expression of TRlim at 37°C in 16 sorghum genotypes previously found to express the trait at the lower temperature. Only three of the genotypes sustained expression of TRlim at 37°C. These results indicate that for environments where temperature may commonly reach or exceed 37°C, sorghum genotypes have been favored that acclimate to the high temperature by losing the TRlim trait. In conditions in which very high temperatures threaten crop heat stress, those genotypes that lose the TRlim trait at high temperature may be more desirable since increasing transpiration rates at these temperatures can result in leaf cooling. The silver test failed to discriminate genotypes for expression of the TRlim trait at high temperature.

Gastric bypass in rats does not decrease appetitive behavior towards sweet or fatty fluids despite blunting preferential intake of sugar and fat

After Roux-en-Y gastric bypass (RYGB) surgery, patients report consuming fewer fatty and dessert-like foods, and rats display blunted sugar and fat preferences. Here we used a progressive ratio (PR) task in our rat model to explicitly test whether RYGB decreases the willingness of rats to work for very small amounts of preferred sugar- and/or fat-containing fluids. In each of two studies, two groups of rats – one maintained on a high-fat diet (HFD) and standard chow (CHOW) and one given CHOW alone – were trained while water-deprived to work for water or either Ensure or 1.0M sucrose on increasingly difficult operant schedules. When tested before surgery while nondeprived, HFD rats had lower PR breakpoints (number of operant responses in the last reinforced ratio) for sucrose, but not for Ensure, than CHOW rats. After surgery, at no time did rats given RYGB show lower breakpoints than SHAM rats for Ensure, sucrose, or when 5% Intralipid served postoperatively as the reinforcer. Nevertheless, RYGB rats showed blunted preferences for these caloric fluids versus water in 2-bottle preference tests. Importantly, although the Intralipid and sucrose preferences of RYGB rats decreased further over time, subsequent breakpoints for them were not significantly impacted. Collectively, these data suggest that the observed lower preferences for normally palatable fluids after RYGB in rats may reflect a learned adjustment to altered postingestive feedback rather than a dampening of the reinforcing taste characteristics of such stimuli as measured by the PR task in which postingestive stimulation is negligible.

Extended Spectrum Beta- Lactamases: A Minireview of Clinical Relevant Groups

Extended spectrum beta-lactamases are enzymes that hydrolyze the beta-lactam ring of Beta-lactam antibiotics rendering the organism resistant. ESBL prevalence is still increasing across the globe and have been implicated in hospital acquired infections and complicated urinary tract infections in Canada. TEM, SHV and CTX-M are becoming more common with CTX-M becoming more of importance as it is associated with complicated urinary tract infections. A variety of detection methods can be used including phenotypical methods, molecular methods and automated methods. Several automated instruments are commercially available to detect phenotypic resistance, recently the Clinical Laboratory Standards Institute has altered their breakpoints negating the necessity to perform confirmatory tests. Unfortunately not all of the commercial panels have the ability to detect lower breakpoints. Due to the importance of ESBL producing organisms in both hospital and community acquired infections, the associated increase in cost treating this infections and expanding spread across the globe, there is a need for further research into these enzymes.

Cocaine withdrawal in rats selectively bred for low (LoS) versus high (HiS) saccharin intake

Cocaine use results in anhedonia during withdrawal, but it is not clear how this emotional state interacts with an individual's vulnerability for addiction. Rats selectively bred for high (HiS) or low (LoS) saccharin intake are a well-established model of drug abuse vulnerability, with HiS rats being more likely to consume sweets and drugs of abuse such as cocaine and heroin (Carroll et al., 2002) than LoS rats. This study examined whether the motivational consequences of cocaine withdrawal are differentially expressed in HiS and LoS rats. HiS and LoS rats were trained to respond for a sucrose reward on a progressive ratio (PR) schedule of reinforcement and breakpoints were measured during and after chronic, continuous exposure to cocaine (30mg/kg/day). Cocaine, but not saline, treatment resulted in lower breakpoints for sucrose during withdrawal in LoS rats only. These results suggest anhedonia during withdrawal is more pronounced in the less vulnerable LoS rats. Fewer motivational deficits during withdrawal may contribute to greater drug vulnerability in the HiS line.

Validation of operant social motivation paradigms using BTBR T+tf/J and C57BL/6J inbred mouse strains.

BackgroundAs purported causal factors are identified for autism spectrum disorder (ASD), new assays are needed to better phenotype animal models designed to explore these factors. With recent evidence suggesting that deficits in social motivation are at the core of ASD behavior, the development of quantitative measures of social motivation is particularly important. The goal of our study was to develop and validate novel assays to quantitatively measure social motivation in mice.MethodsIn order to test the validity of our paradigms, we compared the BTBR strain, with documented social deficits, to the prosocial C57BL/6J strain. Two novel conditioning paradigms were developed that allowed the test mouse to control access to a social partner. In the social motivation task, the test mice lever pressed for a social reward. The reward contingency was set on a progressive ratio of reinforcement and the number of lever presses achieved in the final trial of a testing session (breakpoint) was used as an index of social motivation. In the valence comparison task, motivation for a food reward was compared to a social reward. We also explored activity, social affiliation, and preference for social novelty through a series of tasks using an ANY-Maze video-tracking system in an open-field arena.ResultsBTBR mice had significantly lower breakpoints in the social motivation paradigm than C57BL/6J mice. However, the valence comparison task revealed that BTBR mice also made significantly fewer lever presses for a food reward.ConclusionsThe results of the conditioning paradigms suggest that the BTBR strain has an overall deficit in motivated behavior. Furthermore, the results of the open-field observations may suggest that social differences in the BTBR strain are anxiety induced.

Comparison of phenotypic methods for the detection of carbapenem non-susceptible Enterobacteriaceae.

BackgroundMultidrug resistance and, in particular, carbapenem resistance is spreading worldwide at an alarming rate, comprehending a variety of bacterial species and causing both nosocomial and community acquired outbursts. Early and efficient detection of infected patients or colonized carriers are mandatory steps in infection control and prevention of multidrug resistance diffusion. The latest EUCAST guidelines for detection of carbapenemase-producing Enterobacteriaceae have set low clinical breakpoints to ensure the maximum detection sensitivity of positive samples. Current workflows involve an initial screening step for species and resistance pattern detection, followed by phenotypic and/or genotypic confirmation. The aim of the present study was to assess the efficiency of six widely used and validated phenotypic assays for the detection of carbapenemases/AmpC in Enterobacteriaceae, to estimate the best workflow in the routine characterization of Enterobacteriaceae isolates.MethodsA panel of 108 non-repetitive Enterobacteriaceae isolates with reduced susceptibility to carbapenems was analyzed by means of 1) Modified Hodge Test, 2) Metallo Beta Lactamase Etest, 3) Double disk test with EDTA, 4) Rosco Diagnostica KPC and MBL confirm kit (RDCK™), 5) AmpC Etest and 6) Cloxacillin inhibition test. Confirmation and validation of results was achieved by genotypic analysis.ResultsThe most accurate identification of resistance determinants was obtained with the combined disc test (Rosco Diagnostica KPC and MBL confirm kit) which had to be coupled with the cloxacillin inhibition test for correct detection of AmpC enzymes. However, in general, phenotypic tests failed to characterize isolates harboring multiple carbapenem resistance determinants, which were successfully assessed only by PCR-based analysis.ConclusionsTo detect and control the spread of pathogens with complicated resistance patterns, both optimized phenotypic analysis (i.e. Rosco Diagnostica KPC and MBL confirm kit coupled with the cloxacillin inhibition test) and genotypic assays are recommended in the routine diagnostic of clinical laboratories.

Hydraulic Conductance of Maize Hybrids Differing in Transpiration Response to Vapor Pressure Deficit

ABSTRACTLimited transpiration rate (TR) under high vapor pressure deficit (VPD) conditions has been proposed as a desirable trait for crop yield improvement. The limited‐TR trait has been identified in several single‐cross maize hybrids, and among these hybrids, a range in the VPD breakpoint for limited TR was identified. It was hypothesized that the variation in the VPD breakpoint was due to differences in hydraulic conductance in their roots or leaves, or both. Therefore, the objective of this study was to compare relative hydraulic conductance in the roots and leaves across the maize hybrids expressing the VPD breakpoint. It was found that the VPD of the breakpoint was correlated with each of three indices of hydraulic conductance. That is, low VPD breakpoint was associated with low hydraulic conductance in both leaves and roots indicating a common, underlying limiting mechanism in these two tissues. It was hypothesized that expression of similar aquaporin populations influencing hydraulic flow across membranes in the roots and leaves may account for the consistency in results across the indices of hydraulic conductance.

Food quality and motivation: A refined low-fat diet induces obesity and impairs performance on a progressive ratio schedule of instrumental lever pressing in rats

IntroductionPurified high-fat diet (HFD) feeding causes deleterious metabolic and cognitive effects when compared with unrefined low-fat diets in rodent models. These effects are often attributed to the diet's high content of fat, while less attention has been paid to other mechanisms associated with the diet's highly refined state. Although the effects of HFD feeding on cognition have been explored, little is known about the impact of refined vs. unrefined food on cognition. We tested the hypothesis that a refined low-fat diet (LFD) increases body weight and adversely affects cognition relative to an unrefined diet. Materials and methodsRats were allowed ad libitum access to unrefined rodent chow (CON, Lab Diets 5001) or a purified low-fat diet (REF, Research Diets D12450B) for 6months, and body weight and performance on an instrumental lever pressing task were recorded. ResultsAfter six months on their respective diets, group REF gained significantly more weight than group CON. REF rats made significantly fewer lever presses and exhibited dramatically lower breaking points than CON rats for sucrose and water reinforcement, indicating a chronic reduction of motivation for instrumental performance. Switching the rats' diet for 9days had no effect on these measures. ConclusionsDiet-induced obesity produces a substantial deficit in motivated behavior in rats, independent of dietary fat content. This holds implications for an association between obesity and motivation. Specifically, behavioral traits comorbid with obesity, such as depression and fatigue [1], may be effects of obesity rather than contributing causes. To the degree that refined foods contribute to obesity, as demonstrated in our study, they may play a significant contributing role to other behavioral and cognitive disorders.

Reduced expression of nogo-a leads to motivational deficits in rats.

Nogo-A is an important neurite growth-regulatory protein in the adult and developing nervous system. Mice lacking Nogo-A, or rats with neuronal Nogo-A deficiency, exhibit behavioral abnormalities such as impaired short-term memory, decreased pre-pulse inhibition, and behavioral inflexibility. In the current study, we extended the behavioral profile of the Nogo-A deficient rat line with respect to reward sensitivity and motivation, and determined the concentrations of the monoamines dopamine and serotonin in the prefrontal cortex (PFC), dorsal striatum (dSTR), and nucleus accumbens (NAcc). Using a limited access consumption task, we found similar intake of a sweet condensed milk solution following ad libitum or restricted feeding in wild-type and Nogo-A deficient rats, indicating normal reward sensitivity and translation of hunger into feeding behavior. When tested for motivation in a spontaneous progressive ratio task, Nogo-A deficient rats exhibited lower break points and tended to have lower “highest completed ratios.” Further, under extinction conditions responding ceased substantially earlier in these rats. Finally, in the PFC we found increased tissue levels of serotonin, while dopamine was unaltered. Dopamine and serotonin levels were also unaltered in the dSTR and the NAcc. In summary, these results suggest a role for Nogo-A regulated processes in motivated behavior and related neurochemistry. The behavioral pattern observed resembles aspects of the negative symptomatology of schizophrenia.

Analysis of Competition between Multicomponent BTX Compounds for the Active Site of Adsorption in a Fixed-Bed Column

An experimental and numerical study of the individual and competitive adsorption of BTX compounds (benzene, toluene, and o-xylene) in aqueous solution was carried out in a fixed-bed column filled with activated carbon. The equations of transport were discretized using the finite volumes method and an algorithm was implemented in the Fortran programming language. The results obtained in all cases showed that o-xylene is the contaminant which is most competitive for the active site of the adsorbent, and over time it is able to desorb the compounds which have a lower affinity and adsorb to the free active sites. The result is that the local concentration of the weakly adsorbed component in the fluid phase is higher and surpasses the dimensionless concentration. This finding appeared to be related to the Biot number. As the Biot number increased the rate of competitive adsorption decreased, and the form of the breakthrough curves is flat with a lower breakpoint. This is due to the low intraparticle resistance and also the reduced contact time required to reach saturation.

Ethanol self‐administration in serotonin transporter knockout mice: unconstrained demand and elasticity

Low serotonin function is associated with alcoholism, leading to speculation that increasing serotonin function could decrease ethanol consumption. Mice with one or two deletions of the serotonin transporter (SERT) gene have increased extracellular serotonin. To examine the relationship between SERT genotype and motivation for alcohol, we compared ethanol self-administration in mice with zero (knockout, KO), one (HET) or two copies (WT) of the SERT gene. All three genotypes learned to self-administer ethanol. The SSRI, fluvoxamine, decreased responding for ethanol in the HET and WT, but not the KO mice. When tested under a progressive ratio schedule, KO mice had lower breakpoints than HET or WT. As work requirements were increased across sessions, behavioral economic analysis of ethanol self-administration indicated that the decreased breakpoint in KO as compared to HET or WT mice was a result of lower levels of unconstrained demand, rather than differences in elasticity, i.e. the proportional decreases in ethanol earned with increasing work requirements were similar across genotypes. The difference in unconstrained demand was unlikely to result from motor or general motivational factors, as both WT and KO mice responded at high levels for a 50% condensed milk solution. As elasticity is hypothesized to measure essential value, these results indicate that KO value ethanol similarly to WT or HET mice despite having lower break points for ethanol.