18 research outputs found
Multiple Phytophthora
The diversity of Phytophthora spp. in rivers
and riparian ecosystems has received considerable
international attention, although little such research
has been conducted in South Africa. This study
determined the diversity of Phytophthora spp. within
a single river in Gauteng province of South Africa.
Samples were collected over 1 y including biweekly
river baiting with Rhododendron indicum leaves.
Phytophthora isolates were identified with phylogenetic
analyses of sequences for the internal transcribed
spacer (ITS) region of the ribosomal DNA and the
mitochondrial cytochrome oxidase c subunit I (coxI)
gene. Eight Phytophthora spp. were identified, including
a new taxon, P. taxon Sisulu-river, and two
hybrid species from Cooke’s ITS clade 6. Of these,
species from Clade 6 were the most abundant,
including P. chlamydospora and P. lacustris. Species
residing in Clade 2 also were encountered, including
P. multivora, P. plurivora and P. citrophthora. The
detection of eight species in this investigation of
Phytophthora diversity in a single riparian river
ecosystem in northern South Africa adds to the
known diversity of this genus in South Africa and
globally.We further acknowledge financial support
from the National Research Foundation (NRF), the
Department of Science and Technology/National Research
Foundation (DST/NRF) Centre of Excellence in Tree
Health Biotechnology (CTHB) and the University of
Pretoria, South Africa.http://www.mycologia.orgam2016Forestry and Agricultural Biotechnology Institute (FABI)Genetic
Oxytocin attenuates neural response to emotional faces in social drinkers: an fMRI study
Introduction: Oxytocin is a key mediator of emotional and social behavior that seems to be of relevance for the development and maintenance of addictive behaviors. We thus investigated the effect of oxytocin on neural response and behavior during a face-matching task in a sample of social drinkers. Methods: Thirteen social drinkers underwent a randomized double-blind placebo-controlled cross-over functional magnetic resonance imaging face-matching task with and without prior intranasal application of 24 international units oxytocin. Effects of oxytocin and task condition (faces, shapes) on brain activation and individual task performance were assessed. Results: Face-matching compared to shape-matching trials resulted in higher brain activation in the bilateral amygdala, hippocampus and parts of the occipital gyri. Oxytocin application vs. placebo reduced activation in bilateral amygdala, parts of the frontal gyri, and the parietal lobe. Region of interest analyses indicated that the oxytocin-induced attenuation of amygdala response was specific to face-stimuli and associated with lower subjective alcohol craving, and a lower percentage of heavy-drinking days (defined as >= 5 standard drinks/day). Conclusion: For the first time, we could show that a larger oxytocin-induced attenuation of amygdala response to fearful faces is associated with lower subjective craving for alcohol and percentage of heavy drinking days in social drinkers. Modulation of amygdala activation, induced by emotional stimuli, might represent a neurobiological substrate of oxytocin's protective effects on drug seeking behavior
The NMDA antagonist ketamine and the 5-HT agonist psilocybin produce dissociable effects on structural encoding of emotional face expressions
RATIONALE: Both glutamate and serotonin (5-HT) play a key role in the pathophysiology of emotional biases. Recent studies indicate that the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist ketamine and the 5-HT receptor agonist psilocybin are implicated in emotion processing. However, as yet, no study has systematically compared their contribution to emotional biases. OBJECTIVES: This study used event-related potentials (ERPs) and signal detection theory to compare the effects of the NMDA (via S-ketamine) and 5-HT (via psilocybin) receptor system on non-conscious or conscious emotional face processing biases. METHODS: S-ketamine or psilocybin was administrated to two groups of healthy subjects in a double-blind within-subject placebo-controlled design. We behaviorally assessed objective thresholds for non-conscious discrimination in all drug conditions. Electrophysiological responses to fearful, happy, and neutral faces were subsequently recorded with the face-specific P100 and N170 ERP. RESULTS: Both S-ketamine and psilocybin impaired the encoding of fearful faces as expressed by a reduced N170 over parieto-occipital brain regions. In contrast, while S-ketamine also impaired the encoding of happy facial expressions, psilocybin had no effect on the N170 in response to happy faces. CONCLUSION: This study demonstrates that the NMDA and 5-HT receptor systems differentially contribute to the structural encoding of emotional face expressions as expressed by the N170. These findings suggest that the assessment of early visual evoked responses might allow detecting pharmacologically induced changes in emotional processing biases and thus provides a framework to study the pathophysiology of dysfunctional emotional biases