Neural systems for choice and valuation with counterfactual learning signals.

The purpose of this experiment was to test a computational model of reinforcement learning with and without fictive prediction error (FPE) signals to investigate how counterfactual consequences contribute to acquired representations of action-specific expected value, and to determine the functional neuroanatomy and neuromodulator systems that are involved. 80 male participants underwent dietary depletion of either tryptophan or tyrosine/phenylalanine to manipulate serotonin (5HT) and dopamine (DA), respectively. They completed 80 rounds (240 trials) of a strategic sequential investment task that required accepting interim losses in order to access a lucrative state and maximize long-term gains, while being scanned. We extended the standard Q-learning model by incorporating both counterfactual gains and losses into separate error signals. The FPE model explained the participants' data significantly better than a model that did not include counterfactual learning signals. Expected value from the FPE model was significantly correlated with BOLD signal change in the ventromedial prefrontal cortex (vmPFC) and posterior orbitofrontal cortex (OFC), whereas expected value from the standard model did not predict changes in neural activity. The depletion procedure revealed significantly different neural responses to expected value in the vmPFC, caudate, and dopaminergic midbrain in the vicinity of the substantia nigra (SN). Differences in neural activity were not evident in the standard Q-learning computational model. These findings demonstrate that FPE signals are an important component of valuation for decision making, and that the neural representation of expected value incorporates cortical and subcortical structures via interactions among serotonergic and dopaminergic modulator systems.

A study orientation questionnaire in mathematics for use in a tertiary environment.

The Study Orientation Questionnaire in Mathematics Tertiary is being developed as a diagnostic measure for South African lecturers and counselors to help students improve their orientation toward the study of mathematics. In this pilot study subjects were freshman black students registered for the Five-year Study Programme in the School of Engineering at the University of Pretoria. During the first phase of the standardisation in 2000, 33 students (28 men; 5 women, M age=19.6, SD=.9) were assessed, and in 2001, 40 students (27 men, 13 women, M age=19.2, SD=.9). In 2002 the questionnaire was administered to 51 students (39 men, 12 women, M age= 19.1, SD= .9). Analysis showed satisfactory reliability coefficients and item-field correlations. Step-wise linear regression in 2001 indicated that a combination of two fields, namely, Information Processing and Problem-solving Behaviour in mathematics, contributed significantly (R2=46.9%) to predicting achievement in calculus. In 2002 one field, Mathematics Confidence, contributed significantly (R2= 25.2%) to that prediction.

Prueba de susceptibilidad antimicrobiana de un material de obturación endodóntica / Antimicrobial susceptibility test of an endodontic filling material

Los estudios y ensayos de laboratorio "in vitro" realizados en el presente trabajo con P.L.R.M. (pasta lentamente reabsorbible de Maisto) confirman un efecto bacteriostático con todas las cepas de microorganismos estudiados: Fusobacterium periodonticum ATCC 33693 Prevotella Melaninogénica ATCC 439822 Porphyromonas endodontalis ATCC 35406 Staphylococcus sp., Streptococcus viridans y Streptococcus Grupo A, en períodos de 0 a 56 días y valores de 1g. hasta 0,5mg/ml

Prueba de susceptibilidad antimicrobiana de un material de obturación endodóntica / Antimicrobial susceptibility test of an endodontic filling material

Los estudios y ensayos de laboratorio "in vitro" realizados en el presente trabajo con P.L.R.M. (pasta lentamente reabsorbible de Maisto) confirman un efecto bacteriostático con todas las cepas de microorganismos estudiados: Fusobacterium periodonticum ATCC 33693 Prevotella Melaninogénica ATCC 439822 Porphyromonas endodontalis ATCC 35406 Staphylococcus sp., Streptococcus viridans y Streptococcus Grupo A, en períodos de 0 a 56 días y valores de 1g. hasta 0,5mg/ml (AU)

The role of dietary zinc in modifying the onset and severity of spontaneous diabetes in the BB Wistar rat.

The goal of this study was to determine whether zinc supplementation in the diet of diabetes-prone BB Wistar rats will delay or prevent the onset of overt diabetes. Male Wistar BB rats were fed diets containing either 1000 ppm (HZ), 50 ppm (NZ), or 1 ppm zinc (LZ) starting at 30 days of age. Non-diabetes-prone rats were fed NZ and designated as controls (NORM). Beginning at 60 days, the rats were checked for glycosuria and, if positive, were given an i.p. glucose tolerance test (IPGTT). All remaining animals underwent an IPGTT at 100 days and were sacrificed. At 90 days of age HZ rats had a lower incidence of diabetes (19%) than NZ (53%) or LZ (44%) animals (P < 0.015). By age 100 days, for the HZ group, there was a 60% reduction in the number of expected overt diabetic rats. HZ animals also had higher concentrations of both pancreatic and serum insulin and exhibited lower serum glucose and triglycerides. Immunohistochemistry of HZ rats was clearly different from NZ rats and showed evidence of nearly normal pancreatic endocrine activity. Data indicate that dietary treatment of diabetes-prone BB Wistar rats with zinc appears to be an effective approach for delaying or preventing the onset of diabetes in genetically predisposed rodents. This finding may suggest further experimental studies regarding dietary means for preservation of pancreatic function.

Listeria monocytogenes y Listeria sp en productos termoprocesados / Listeria monocytogenes and other Listeria spp in thermoprocessed products

Se investigó la presencia de Listeria monocytogenes y Listeria sp en embutidos termoprocesados, envasados al vacío, conservados refrigerados y que se consumen sin cocción o con un mínimo calentamiento. Se examinaron treinta muestras de embutidos que incluían: salchicha tipo viena, salchichón con jamón, salchichón primavera, leberwurst y mortadela, proveniente de distintos comercios de venta al público. Se utilizó el método recomendado por USDA-FSIS para productos cárneos. Simultáneamente se realizó el aislamiento selectivo en agar McBride. Se obtuvieron siete aislamientos de Listeria sp, de las cuales cinco fueron confirmadas microscópica, cultural y bioquímicamente como Listeria monocytogenes, por lo cual se lo puede considerar como potencialmente peligroso para un amplio grupo susceptible de la población. La presencia del microorganismo en estos productos sugiere una contaminación ambiental post-proceso o un proceso térmico insuficiente (AU)

Listeria monocytogenes y Listeria sp en productos termoprocesados / Listeria monocytogenes and other Listeria spp in thermoprocessed products

Se investigó la presencia de Listeria monocytogenes y Listeria sp en embutidos termoprocesados, envasados al vacío, conservados refrigerados y que se consumen sin cocción o con un mínimo calentamiento. Se examinaron treinta muestras de embutidos que incluían: salchicha tipo viena, salchichón con jamón, salchichón primavera, leberwurst y mortadela, proveniente de distintos comercios de venta al público. Se utilizó el método recomendado por USDA-FSIS para productos cárneos. Simultáneamente se realizó el aislamiento selectivo en agar McBride. Se obtuvieron siete aislamientos de Listeria sp, de las cuales cinco fueron confirmadas microscópica, cultural y bioquímicamente como Listeria monocytogenes, por lo cual se lo puede considerar como potencialmente peligroso para un amplio grupo susceptible de la población. La presencia del microorganismo en estos productos sugiere una contaminación ambiental post-proceso o un proceso térmico insuficiente

[Listeria monocytogenes and Listeria sp in heat-processed products]. / Listeria monocytogenes y Listeria sp en productos termoprocesados.

Presence of Listeria monocytogenes in thermoprocessed food which is vacuum packaged, refrigerated stored and eaten uncooked or minimally heated was investigated. Thirty samples including sausage, large sausage with ham, spring large sausage, liverwurst and bologna were examined. Listeria monocytogenes was isolated and identified according to USDA-FSIS method for meat products, simultaneously with McBride agar. Seven out of 30 samples were found to contain listeriae. Five isolates were identified as Listeria monocytogenes through Gram coloration, culture appearance, biochemical test and serotyping. This product results potentially risky for the susceptible population. The presence of this microorganism in this kind of product suggests environmental post-process contamination or insufficient thermal process.

Effects of pentachlorophenol on the development of estuarine communities.

Pentachlorophenol affected the composition of communities of estuarine organisms developed in sand from planktonic larvae in estuarine water that flowed through ten control aquaria and ten aquaria per exposure concentration averaging 7, 76, or 622 microgram/liter. Annelids, arthropods, and mollusks were the numerically dominant phyla when animals were collected in a 1-mm-mesh sieve after 9 wk of exposure. Mollusks were markedly fewer at 7 microgram/liter; annelids and arthropods at 76 microgram/liter. Almost no animals occurred at 622 microgram/liter. The total numbers of individuals and species were significantly less (alpha=0.01) in aquaria exposed to 76 microgram/liter than in those unexposed or exposed to 7 microgram/liter.