Photoreactivity of biologically active compounds. XIX: Excited states and free radicals from the antimalarial drug primaquine

The formation and reactivity of excited states and free radicals from primaquine was studied in order to evaluate the primary photochemical reaction mechanisms. The excited primaquine triplet was not detected, but is likely to be formed with a short lifetime (< 50 ns) and with a triplet energy < 250 kJ/mol as the drug is an efficient quencher of the fenbufen triplet and the biphenyl triplet, and forms 1O2 by laser flash photolysis (PQΦΔ = 0.025). Primaquine photoionises by a biphotonic process and also forms the monoprotonated cation radical (PQH2+•) by one electron oxidation by OH• (kq = 6.6•109 M-1s-1) and Br2•- (kq = 4.7•109 M-1s-1) at physiological pH, detected as a long-lived transient decaying essentially by a second order process (k2 = 7.4•108 M-1s-1). PQH2+• is scavenged by O2, although at a limited rate (kq = 1.0•106 M-1s-1). The reduction potential (E°) of PQH2+• / PQH+ is < +1015 mV. Primaquine also forms PQH2+• at pH 2.4, by one electron oxidation by Br2•- and proton loss (kq = 2.7•109 M-1s-1). The non-protonated cation radical (PQ+•) is formed during one electron oxidation with Br2•- at alkaline conditions (kq = 4.2•109 M-1s-1 at pH 10.8). The estimated pKa-value of PQH2+•/ PQ+• is pKa ~ 7-8. Primaquine is not a scavenger of O2•- at physiological pH. Thus self-sensitization by O2•- is eliminated as a degradation pathway in the photochemical reactions. Impurities in the raw material and photochemical degradation products initiate photosensitized degradation of primaquine in deuterium oxide, prevented by addition of the 1O2 quencher sodium azide. Photosensitized degradation by formation of 1O2 is thus important for the initial photochemical decomposition of primaquine, which also proceeds by free radical reactions. Formation of PQH2+• is expected to play an essential part in the photochemical degradation process in a neutral, aqueous medium

Selective 5HT3 antagonists and sensory processing: A systematic review

Ondansetron is a selective serotonin (5HT3) receptor antagonist that is under evaluation as an adjunctive treatment for schizophrenia, and a novel treatment for hallucinations in Parkinson’s disease. Ondansetron reverses sensory gating deficits and improves visuoperceptual processing in animal models of psychosis, but it is unclear to what extent preclinical findings have been replicated in humans. We systematically reviewed human studies that evaluated the effects of ondansetron and other 5HT3 receptor antagonists on sensory gating deficits or sensory processing. Of 11 eligible studies, eight included patients with schizophrenia who were chronically stable on antipsychotic medication; five measured sensory gating using the P50 suppression response to a repeated auditory stimulus; others included tests of visuoperceptual function. Three studies in healthy participants included tests of visuoperceptual and sensorimotor function. A consistent and robust finding (five studies) was that ondansetron and tropisetron (5HT3 antagonist and α7-nicotinic receptor partial agonist) improved sensory gating in patients with schizophrenia. Tropisetron also improved sustained visual attention in non-smoking patients. There was inconsistent evidence of the effects of 5HT3 antagonists on other measures of sensory processing, but interpretation was limited by the small number of studies, methodological heterogeneity and the potential confounding effects of concomitant medication in patients. Despite these limitations, we found strong evidence that selective 5HT3 antagonists (with or without direct α7-nicotinic partial agonist effects) improved sensory gating. Future studies should investigate how this relates to potential improvement in neurocognitive symptoms in antipsychotic naive patients with prodromal or milder symptoms, in order to understand the clinical implications

Improve the potato crop

8 pages; includes photographs. This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Microstructural and mechanical characterisation of post-tentioning strands following elevated temperature exposure

Prestressing strands lose strength and become more susceptible to creep deformation when they are heated during a fire. The consequent loss in prestressing force could under certain conditions result in structural collapse, potentially outwith the heated region of the structure. This paper describes a test programme characterising the changes in microstructure of steel prestressing tendons exposed to elevated temperatures. The residual strength tests, hardness testing, and elevated temperature mechanical test were performed to demonstrate how recovery and recrystallisation of the initially work-hardened steel produce changes in its mechanical properties at elevated temperatures. The research results of this paper are beneficial not only in the fire design of post-tensioned structures using modern prestressing steel, but also in the assessment of the tendons’ residual strength after being affected by fire

Allocentric spatial memory performance predicts intrusive memory severity in posttraumatic stress disorder

BACKGROUND: Posttraumatic stress disorder (PTSD) is characterised by distressing trauma-related memories. According to the dual representation theory, intrusive memories arise from strengthened egocentric encoding and a poor contextual encoding, with spatial context requiring allocentric processing. Contextualization of mental imagery is proposed to be formed hierarchically through the ventral visual stream (VVS) to the hippocampal formation. Here, we tested this notion by investigating whether neuronal aberrations in structures of the VVS or in the hippocampus, as well as allocentric memory performance are associated with intrusive memory severity. METHODS: The sample comprised 33 women with PTSD due to childhood trauma. Allocentric memory performance was measured with the virtual Town Square Task and T1-weighted images acquired on a 3T Siemens Scanner. Intrusive memories were evoked by presenting an audio script describing parts of their trauma (script-driven imagery). RESULTS: Using hierarchical linear regression analysis, we found a significant association between lower intrusive memory severity and higher allocentric spatial memory, controlling for age, working memory, and general visuospatial ability. No significant association was found between cortical thickness of VVS structures, hippocampal volume and intrusive memory severity. Post hoc exploratory analyses revealed a negative correlation between years since index trauma and left hippocampal volume. LIMITATIONS: Our results are based on correlational analyses, causality cannot be inferred. CONCLUSION: This study supports the dual representation theory, which emphasizes the role of allocentric spatial memory for the contextualization of mental imagery in PTSD. Clinical implications are discussed

Repetitive negative thinking in the perinatal period and its relationship with anxiety and depression

Background: Rumination and worry represent two types of repetitive negative thinking (RNT), and their predictive and maintaining roles are well-established in depression and anxiety, respectively. Furthermore, there is an emerging literature on the link between RNT and psychological wellbeing in the perinatal period. Methods: We conducted a scoping review of studies that have investigated the relationship between RNT and perinatal depression and anxiety. We identified 87 papers eligible for inclusion in the review; they included cross-sectional and longitudinal studies, as well as treatment evaluations (pilot trials and randomised controlled trials). Results: Cross-sectional studies provided evidence of an association between RNT (i.e., rumination and worry) and depression and anxiety, in both pregnancy and postpartum. Longitudinal findings were mixed. Whilst antenatal worry consistently predicted subsequent depression and anxiety (both later in pregnancy and postpartum), rumination did not consistently predict depression. However, there was some evidence that RNT interacted with other processes to predict later psychopathology. Three randomised controlled trials evaluated whether psychological treatments reduce RNT in the perinatal period, only one of which included a clinical sample. Limitations: No experimental investigations were eligible for inclusion in the review. Conclusions: Further studies are needed to further our understanding of the nature and role of RNT in pregnancy and postpartum, and its consequences for maternal mental health. These include (but are not limited to) experimental investigations, studies with large clinical samples, and RCTs evaluating the effectiveness of psychological interventions targeting RNT to prevent and treat perinatal depression and anxiety