Brain Potentials of Conflict and Error-Likelihood Following Errorful and Errorless Learning in Obsessive-Compulsive Disorder

Background

The anterior cingulate cortex (ACC) is thought to be overacting in patients with Obsessive Compulsive Disorder (OCD) reflecting an enhanced action monitoring system. However, influences of conflict and error-likelihood have not been explored. Here, the error-related negativity (ERN) originating in ACC served as a measure of conflict and error-likelihood during memory recognition following different learning modes. Errorless learning prevents the generation of false memory candidates and has been shown to be superior to trial-and-error-learning. The latter, errorful learning, introduces false memory candidates which interfere with correct information in later recognition leading to enhanced conflict processing.

Methodology/Principal Findings

Sixteen OCD patients according to DSM-IV criteria and 16 closely matched healthy controls participated voluntarily in the event-related potential study. Both, OCD- and control group showed enhanced memory performance following errorless compared to errorful learning. Nevertheless, response-locked data showed clear modulations of the ERN amplitude. OCD patients compared to controls showed an increased error-likelihood effect after errorless learning. However, with increased conflict after errorful learning, OCD patients showed a reduced error-likelihood effect in contrast to controls who showed an increase.

Conclusion/Significance

The increase of the errorlikelihood effect for OCD patients within low conflict situations (recognition after errorless learning) might be conceptualized as a hyperactive monitoring system. However, within high conflict situations (recognition after EF-learning) the opposite effect was observed: whereas the control group showed an increased error-likelihood effect, the OCD group showed a reduction of the error-likelihood effect based on altered ACC learning rates in response to errors. These findings support theoretical frameworks explaining differences in ACC activity on the basis of conflict and perceived error-likelihood as influenced by individual error learning rate.     

Optical Mapping of Langendorff-perfused Rat Hearts

Optical mapping of the cardiac surface with voltage-sensitive fluorescent dyes has become an important tool to investigate electrical excitation in experimental models that range in scale from cell cultures to whole-organs^{[1, 2]}. Using state-of-the-art optical imaging systems, generation and propagation of action potentials during normal cardiac rhythm or throughout initiation and maintenance of arrhythmias can be visualized almost instantly^[1]. The latest commercially-available systems can provide information at exceedingly high spatiotemporal resolutions and were based on custom-built equipment initially developed to overcome the obstacles imposed by more conventional electrophysiological methods^[1]. Advancements in high-resolution and high-speed complementary metal-oxide-semiconductor (CMOS) cameras and intensely-bright, light-emitting diodes (LEDs) as well as voltage-sensitive dyes, optics, and filters have begun to make electrical signal acquisition practical for cardiovascular cell biologists who are more accustomed to working with microscopes. Although the newest generation of CMOS cameras can acquire 10,000 frames per second on a 16,384 pixel array, depending on the type of sample preparation, long-established fluorescence acquisition technologies such as photodiode arrays, laser scanning systems, and cooled charged-coupled device (CCD) cameras still have some distinct advantages with respect to dynamic range, signal-to-noise ratio, and quantum efficiency^{[1, 3]}. In the present study, Lewis rat hearts were perfused ex vivo with a crystalloid perfusate (Krebs-Henseleit solution) at 37°C on a modified Langendorff apparatus. After a 20 minute stabilization period, the hearts were intermittently perfused with 11 mMol/L 2,3-butanedione monoxime to eliminate contraction-associated motion during image acquisition. For optical mapping, we loaded hearts with the fast-response potentiometric probe di-8-ANEPPS^[4] (5 μMol/L) and briefly illuminated the preparation with 475±15 nm excitation light. During a typical 2 second period of illumination, >605 nm light emitted from the cardiac preparation was imaged with a high-speed CMOS camera connected to a horizontal macroscope. For this demonstration, hearts were paced at 300 beats per minute with a coaxial electrode connected to an isolated electrical stimulation unit. Simultaneous bipolar electrographic recordings were acquired and analyzed along with the voltage signals using readily-available software. In this manner, action potentials on the surface of Langendorff-perfused rat hearts can be visualized and registered with electrographic signals.Download video file.^{(136M, mp4)}     

From the cradle of agriculture a handful of lentils: History of domestication

Literature on lentil domestication is reviewed, particularly considering archeobotanical, phylogenetic, and molecular evidence. Lentils are one of the oldest crops cultivated and domesticated by man. Carbonized small lentil seeds have been found in several archaeological remains starting from the Neolithic. It is probable, however, that the most ancient remains refer to wild lentils; this is difficult to ascertain since seed size was probably selected after the establishment of a domesticated lentil. It is general opinion that cultivation occurred before domestication, but for how long is still an open question. It is now well accepted that the domestication of lentils was accomplished in the Near East, in an area called “the cradle of agriculture”. The genus Lens is very small, containing only 6 taxa. A wide range of morphological and molecular evidence supports the idea that the lentil wild progenitor is Lens culinaris ssp. orientalis. On the other hand, the most distantly related species within the genus appears to be L. nigricans, whose domestication was also attempted without success. The first characters involved in lentil domestication were pod dehiscence and seed dormancy. These traits are under a simple genetic control, and therefore mutants must have been fixed in a relatively short time. These and other morphological traits possibly involved in lentil domestication have been mapped in several linkage maps. However, generally these maps are not easily integrated since they are based on a limited number of markers. Newer maps, mainly built on different kinds of molecular markers, have been more recently produced. A consensus map is needed to fill the gap in lentil breeding and, at the same time, endow with deeper information on the genetics of lentil domestication, giving new insight into the origins of this crop, which present fragmented knowledge is unable.      

Genetic Dissection of the Amyloid Precursor Protein in Developmental Function and Amyloid Pathogenesis

Proteolytic processing of the amyloid precursor protein (APP) generates large soluble APP derivatives, β-amyloid (Aβ) peptides, and APP intracellular domain. Expression of the extracellular sequences of APP or its Caenorhabditis elegans counterpart has been shown to be sufficient in partially rescuing the CNS phenotypes of the APP-deficient mice and the lethality of the apl-1 null C. elegans, respectively, leaving open the question as what is the role of the highly conserved APP intracellular domain? To address this question, we created an APP knock-in allele in which the mouse Aβ sequence was replaced by the human Aβ. A frameshift mutation was introduced that replaced the last 39 residues of the APP sequence. We demonstrate that the C-terminal mutation does not overtly affect APP processing and amyloid pathology. In contrast, crossing the mutant allele with APP-like protein 2 (APLP2)-null mice results in similar neuromuscular synapse defects and early postnatal lethality as compared with mice doubly deficient in APP and APLP2, demonstrating an indispensable role of the APP C-terminal domain in these development activities. Our results establish an essential function of the conserved APP intracellular domain in developmental regulation, and this activity can be genetically uncoupled from APP processing and Aβ pathogenesis.     

CARMIL is a potent capping protein antagonist: identification of a conserved CARMIL domain that inhibits the activity of capping protein and uncaps capped actin filaments

Acanthamoeba CARMIL was previously shown to co-purify with capping protein (CP) and to bind pure CP. Here we show that this interaction inhibits the barbed end-capping activity of CP. Even more strikingly, this interaction drives the uncapping of actin filaments previously capped with CP. These activities are CP-specific; CARMIL does not inhibit the capping activities of either gelsolin or CapG and does not uncap gelsolin-capped filaments. Although full-length (FL) CARMIL (residues 1-1121) possesses both anti-CP activities, C-terminal fragments like glutathione S-transferase (GST)-P (940-1121) that contain the CARMIL CP binding site are at least 10 times more active. We localized the full activities of GST-P to its C-terminal 51 residues (1071-1121). This sequence contains a stretch of 25 residues that is highly conserved in CARMIL proteins from protozoa, flies, worms, and vertebrates (CARMIL Homology domain 3; CAH3). Point mutations showed that the majority of the most highly conserved residues within CAH3 are critical for the anti-CP activity of GST-AP (862-1121). Finally, we found that GST-AP binds CP approximately 20-fold more tightly than does FL-CARMIL. This observation together with the elevated activities of C-terminal fragments relative to FL-CARMIL suggests that FL-CARMIL might exist primarily in an autoinhibited state. Consistent with this idea, proteolytic cleavage of FL-CARMIL with thrombin generated an approximately 14-kDa C-terminal fragment that expresses full anti-CP activities. We propose that, after some type of physiological activation event, FL-CARMIL could function in vivo as a potent CP antagonist. Given the pivotal role that CP plays in determining the global actin phenotype of cells, our results suggest that CARMIL may play an important role in the physiological regulation of actin assembly.     

DUSP meet immunology: dual specificity MAPK phosphatases in control of the inflammatory response

The MAPK family members p38, JNK, and ERK are all activated downstream of innate immunity's TLR to induce the production of cytokines and inflammatory mediators. However, the relative intensity and duration of the activation of different MAPK appears to determine the type of immune response. The mammalian genome encodes a large number of dual specificity phosphatases (DUSP), many of which act as MAPK phosphatases. In this study, we review the emergence of several DUSP as genes that are differentially expressed and regulated in immune cells. Recently, a series of investigations in mice deficient in DUSP1, DUSP2, or DUSP10 revealed specificity in the regulation of the different MAPK proteins, and defined essential roles in models of local and systemic inflammation. The DUSP family is proposed as a set of molecular control devices specifying and modulating MAPK signaling, which may be targeted to unleash or attenuate innate and adaptive immune effector functions.     

Chromatofocusing: a new method for purification of staphylococcal enterotoxins B and C1

A new chromatographic procedure was developed which obtained highly purified preparations of staphylococcal enterotoxins B and C1 in yields of 60% from cultures of Staphylococcus aureus and which is faster than any of the separation methods used previously. The procedure involves chromatography on carboxymethylcellulose, removal of alpha-toxin by adsorption to rabbit erythrocyte membranes, and finally, chromatofocusing as the fundamental new step. Enterotoxins were obtained in highly purified form and behaved in a homogeneous manner as determined by ultracentrifugation and electrophoresis on polyacrylamide gel in the presence of sodium dodecyl sulfate, with molecular weights of 34,000 for staphylococcal enterotoxin B and 30,000 for staphylococcal enterotoxin C1. Using chromatofocusing as the final purification step, we isolated three B and six C1 distinct but immunologically identical enterotoxin fractions, which were found to be devoid of any impurities and to possess a marked degree of toxicity in monkeys.     

Production of cytotoxin by clinical strains of Pseudomonas aeruginosa

Presence of cytotoxin was studied in extracts of 57 strains of Pseudomonas aeruginosa (46 bacteremia, 4 environmental, and 7 Fisher immunotype), 10 Pseudomonas species, and 7 nonpseudomonas isolates. Cytotoxin was identified by Western immunoblot in extracts of all P. aeruginosa isolates. None of the Pseudomonas species or nonpseudomonas isolates were shown to produce this protein. No immunologic cross-reactivity was observed between cytotoxin antibody and P. aeruginosa alkaline protease, toxin A, or elastase. In partially purified extracts of two bacteremia strains and PA 158 (parent strain for cytotoxin production), detection of cytotoxin by Western immunoblot was correlated with biological activity, as measured by the cell swelling assay. Cytotoxin appears to be produced by all strains of P. aeruginosa and biological activity can be demonstrated in extracts of the strains tested. This biological activity is neutralized by specific antibody. Because of its known marked cytotoxic effect on most eukaryotic cells, P. aeruginosa cytotoxin might be an important factor in the pathogenesis of P. aeruginosa infections.