An investigation into the neuroprotective and neurotoxic properties of levodopa, dopamine and selegiline

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by a profound loss of dopaminergic neurons from the substantia nigra (SN). Among the many pathogenic mechanisms thought to be responsible for the demise of these cells, dopamine (DA)-dependent oxidative stress and oxidative damage has taken center stage due to extensive experimental evidence showing that DA-derived reactive oxygen species (ROS) and oxidized DA metabolites are toxic to SN neurons. Despite its being the most efficacious drug for symptom reversal in PD, there is concern that levodopa (LD) may contribute to the neuronal degeneration and progression of PD by enhancing DA concentrations and turnover in surviving dopaminergic neurons. The present study investigates the potential neurotoxic and neuroprotective effects of DA in vitro. These effects are compared to the toxicity and neuroprotective effects observed in the rat striatum after the administration of LD and selegiline (SEL), both of which increase striatal DA levels. The effects of exogenous LD and/or SEL administration on both the oxidative stress caused by increased striatal iron (II) levels and its consequences have also been investigated. 6-Hydroxydopamine (6-OHDA) is a potent neurotoxin used to mimic dopaminergic degeneration in animal models of PD. The formation of 6-OHDA in vivo could destroy central dopaminergic nerve terminals and enhance the progression of PD. Inorganic studies using high performance liquid chromatography with electrochemical detection (HPLC-ECD) show that hydroxyl radicals can react with DA to form 6-OHDA in vitro. SEL results in a significant decrease in the formation of 6-OHDA in vitro, probably as a result of its antioxidant properties. However, the exogenous administration of LD, with or without SEL, either does not lead to the formation of striatal 6-OHDA in vivo or produces concentrations below the detection limit of the assay. This is despite the fact that striatal DA levels in these rats are significantly elevated (two-fold) compared to the control group. The auto-oxidation and monoamine oxidase (MAO)-mediated metabolism of DA causes an increase in the production of superoxide anions in whole rat brain homogenate in vitro. In addition to this, DA is able to enhance the production of hydroxyl radicals by Fenton chemistry (Fe(III)-EDTA/H2O2) in a cell free environment. Treatment with systemic LD elevates the production of striatal superoxide anions, but does not lead to a detectable increase in striatal hydroxyl radical production in vivo. The co-adminstration of SEL with LD is able to prevent the LD induced rise in striatal superoxide levels. It has been found that the presence of DA or 6-OHDA is able to reduce lipid peroxidation in whole rat brain homogenate induced by Fe(II)-EDTA/H2O2 and ascorbate (Fenton system). However, DA and 6-OHDA increase protein oxidation in rat brain homogenate, which is further increased in the presence of the Fenton system. In addition to this, the incubation of rat brain homogenate with DA or 6-OHDA is also accompanied by a significant reduction in the total GSH content of the homogenate. The exogenous administration of LD and/or SEL was found to have no detrimental effects on striatal lipids, proteins or total GSH levels. Systemic LD administration actually had a neuroprotective effect in the striatum by inhibiting iron (II) induced lipid peroxidation. Inorganic studies, including electrochemistry and the ferrozine assay show that DA and 6-OHDA are able to release iron from ferritin, as iron (II), and that DA can bind iron (III), a fact that may easily impede the availability of this metal ion for participation in the Fenton reaction. The binding of iron (III) by DA appears to discard the involvement of the Fenton reaction in the increased production of hydroxyl radicals induced by the addition of DA to mixtures containing Fe(II)-EDTA and hydrogen peroxide. 6-OHDA did not form a metal-ligand complex with iron (II) or iron (III). In addition to the antioxidant activity and MAO-B inhibitory activity of SEL, the iron binding studies show that SEL has weak iron (II) chelating activity and that it can also form complexes with iron (III). This may therefore be another mechanism involved in the neuroprotective action of SEL. The results of the pineal indole metabolism study show that the systemic administration of SEL increases the production of N-acetylserotonin (NAS) by the pineal gland. NAS has been demonstrated to be a potent antioxidant in the brain and protects against 6-OHDA induced toxicity. The results of this study show that DA displays antioxidant properties in relation to lipid eroxidation and exhibits pro-oxidant properties by causing an increase in the production of hydroxyl radicals and superoxide anions, as well as protein oxidation and a loss of total GSH content. Despite the toxic effects of DA in vitro, the treatment of rats with exogenous LD does not cause oxidative stress or oxidative damage. The results also show that LD and SEL have some neuroprotective properties which make these agents useful in the treatment of PD

An investigation into the neuroprotective and neurotoxic properties of levodopa, dopamine and selegiline

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by a profound loss of dopaminergic neurons from the substantia nigra (SN). Among the many pathogenic mechanisms thought to be responsible for the demise of these cells, dopamine (DA)-dependent oxidative stress and oxidative damage has taken center stage due to extensive experimental evidence showing that DA-derived reactive oxygen species (ROS) and oxidized DA metabolites are toxic to SN neurons. Despite its being the most efficacious drug for symptom reversal in PD, there is concern that levodopa (LD) may contribute to the neuronal degeneration and progression of PD by enhancing DA concentrations and turnover in surviving dopaminergic neurons. The present study investigates the potential neurotoxic and neuroprotective effects of DA in vitro. These effects are compared to the toxicity and neuroprotective effects observed in the rat striatum after the administration of LD and selegiline (SEL), both of which increase striatal DA levels. The effects of exogenous LD and/or SEL administration on both the oxidative stress caused by increased striatal iron (II) levels and its consequences have also been investigated. 6-Hydroxydopamine (6-OHDA) is a potent neurotoxin used to mimic dopaminergic degeneration in animal models of PD. The formation of 6-OHDA in vivo could destroy central dopaminergic nerve terminals and enhance the progression of PD. Inorganic studies using high performance liquid chromatography with electrochemical detection (HPLC-ECD) show that hydroxyl radicals can react with DA to form 6-OHDA in vitro. SEL results in a significant decrease in the formation of 6-OHDA in vitro, probably as a result of its antioxidant properties. However, the exogenous administration of LD, with or without SEL, either does not lead to the formation of striatal 6-OHDA in vivo or produces concentrations below the detection limit of the assay. This is despite the fact that striatal DA levels in these rats are significantly elevated (two-fold) compared to the control group. The auto-oxidation and monoamine oxidase (MAO)-mediated metabolism of DA causes an increase in the production of superoxide anions in whole rat brain homogenate in vitro. In addition to this, DA is able to enhance the production of hydroxyl radicals by Fenton chemistry (Fe(III)-EDTA/H2O2) in a cell free environment. Treatment with systemic LD elevates the production of striatal superoxide anions, but does not lead to a detectable increase in striatal hydroxyl radical production in vivo. The co-adminstration of SEL with LD is able to prevent the LD induced rise in striatal superoxide levels. It has been found that the presence of DA or 6-OHDA is able to reduce lipid peroxidation in whole rat brain homogenate induced by Fe(II)-EDTA/H2O2 and ascorbate (Fenton system). However, DA and 6-OHDA increase protein oxidation in rat brain homogenate, which is further increased in the presence of the Fenton system. In addition to this, the incubation of rat brain homogenate with DA or 6-OHDA is also accompanied by a significant reduction in the total GSH content of the homogenate. The exogenous administration of LD and/or SEL was found to have no detrimental effects on striatal lipids, proteins or total GSH levels. Systemic LD administration actually had a neuroprotective effect in the striatum by inhibiting iron (II) induced lipid peroxidation. Inorganic studies, including electrochemistry and the ferrozine assay show that DA and 6-OHDA are able to release iron from ferritin, as iron (II), and that DA can bind iron (III), a fact that may easily impede the availability of this metal ion for participation in the Fenton reaction. The binding of iron (III) by DA appears to discard the involvement of the Fenton reaction in the increased production of hydroxyl radicals induced by the addition of DA to mixtures containing Fe(II)-EDTA and hydrogen peroxide. 6-OHDA did not form a metal-ligand complex with iron (II) or iron (III). In addition to the antioxidant activity and MAO-B inhibitory activity of SEL, the iron binding studies show that SEL has weak iron (II) chelating activity and that it can also form complexes with iron (III). This may therefore be another mechanism involved in the neuroprotective action of SEL. The results of the pineal indole metabolism study show that the systemic administration of SEL increases the production of N-acetylserotonin (NAS) by the pineal gland. NAS has been demonstrated to be a potent antioxidant in the brain and protects against 6-OHDA induced toxicity. The results of this study show that DA displays antioxidant properties in relation to lipid eroxidation and exhibits pro-oxidant properties by causing an increase in the production of hydroxyl radicals and superoxide anions, as well as protein oxidation and a loss of total GSH content. Despite the toxic effects of DA in vitro, the treatment of rats with exogenous LD does not cause oxidative stress or oxidative damage. The results also show that LD and SEL have some neuroprotective properties which make these agents useful in the treatment of PD

An exploration of the perceived relationship between the level of power of stakeholder groups and their resistance to organisational change

The success of organisational change processes can be significantly enhanced by effectively addressing resistance to change among a range of stakeholders as well as the impact of their resistance. There is, however, limited research on the relationship between stakeholders’ level of power and their propensity to resist change in a certain manner. This study therefore explored the interrelationships between stakeholders’ perceived level of power and their type of resistance, via face-to-face, in-depth interviews with fifteen professional change agents from three sample groups comprising change consultants, internal human resource managers and internal senior managers, all of whom had led change interventions. The findings revealed surprising trends in that certain stakeholder groups showed resistance more actively and overtly than others in direct proportion to their levels of power. These results culminated in a conceptual framework on stakeholders, power and resistance. This article highlights important implications for managers and change practitioners.http://www.journals.co.za/content/journalam2016Gordon Institute of Business Science (GIBS

Quality improvement in the management of people with epilepsy and intellectual disability: the development of clinical guidance

Introduction: This clinical guidance looks at the specific concerns of delivery of medical treatment for people with epilepsy and intellectual disability (ID). People with ID have not been included in licensing drug trials of AEDs. However, this population has an over-representation of seizure comorbidity, treatment resistance, and polypharmacy while also being vulnerable to not having their views considered. Areas covered: This review summarizes the current most robust evidence available for the use of licensed AEDs in people with epilepsy and ID. The article provides practical evidence-based clinical information to help prescribers choose the most appropriate AED from the drugs discussed. The article highlights other important individualized factors to consider before initiating or changing antiepileptic medication. Expert opinion: A ‘traffic light’ coding system is applied to commonly used AEDs based on the level of evidence and expert clinical experience. Managing epilepsy in the ID population requires specialist care. Treatment plans need to be holistic and tailored to accommodate an individual’s comorbidities, concurrent medications, general health, social and environmental status. There is a need for large quality trial data to assess the most suitable AEDs on seizure control and quality of life in this population with complex needs

Interventions to reduce interpersonal stigma towards patients with a mental dysregulation for ambulance and emergency department healthcare professionals: review protocol for an integrative review

Introduction Worldwide, there is an increase in the extent and severity of mental illness. Exacerbation of somatic complaints in this group of people can result in recurring ambulance and emergency department care. The care of patients with a mental dysregulation (ie, experiencing a mental health problem and disproportionate feelings like fear, anger, sadness or confusion, possibly with associated behaviours) can be complex and challenging in the emergency care context, possibly evoking a wide variety of feelings, ranging from worry or pity to annoyance and frustration in emergency care staff members. This in return may lead to stigma towards patients with a mental dysregulation seeking emergency care. Interventions have been developed impacting attitude and behaviour and minimising stigma held by healthcare professionals. However, these interventions are not explicitly aimed at the emergency care context nor do these represent perspectives of healthcare professionals working within this context. Therefore, the aim of the proposed review is to gain insight into interventions targeting healthcare professionals, which minimise stigma including beliefs, attitudes and behaviour towards patients with a mental dysregulation within the emergency care context. Methods and analysis The protocol for a systematic integrative review is presented, using the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols recommendations. A systematic search was performed on 13 July 2023. Study selection and data extraction will be performed by two independent reviewers. In each step, an expert with lived experience will comment on process and results. Software applications RefWorks-ProQuest, Rayyan and ATLAS. ti will be used to enhance the quality of the review and transparency of process and results. Ethics and dissemination No ethical approval or safety considerations are required for this review. The proposed review will be submitted to a relevant international journal. Results will be presented at relevant medical scientific conferences

Examining the antecedents of challenge and threat states: The influence of perceived required effort and support availability

To date, limited research has explicitly examined the antecedents of challenge and threat states proposed by the biopsychosocial model. Thus, the aim of the present study was to examine the influence of perceived required effort and support availability on demand/resource evaluations, challenge and threat states, and motor performance. A 2 (required effort; high, low) � 2 (support availability; available, not available) between-subjects design was used with one hundred and twenty participants randomly assigned to one of four experimental conditions. Participants received instructions designed to manipulate perceptions of required effort and support availability before demand/resource evaluations and cardiovascular responses were assessed. Participants then performed the novel motor task (laparoscopic surgery) while performance was recorded. Participants in the low perceived required effort condition evaluated the task as more of a challenge (i.e., resources outweighed demands), exhibited a cardiovascular response more indicative of a challenge state (i.e., higher cardiac output and lower total peripheral resistance), and performed the task better (i.e., quicker completion time) than those in the high perceived required effort condition. However, perceptions of support availability had no significant impact on participants' demand/resource evaluations, cardiovascular responses, or performance. Furthermore, there was no significant interaction effect between perceptions of required effort and support availability. The findings suggest that interventions aimed at promoting a challenge state should include instructions that help individuals perceive that the task is not difficult and requires little physical and mental effort to perform effectively

Defining the concept of mental dysregulation in patients requiring ambulance and/or emergency department care: protocol for a Delphi consensus study

Introduction From the patient and staff perspective, care delivery for patients experiencing a mental health problem in ambulance and emergency department (ED) settings is challenging. There is no uniform and internationally accepted concept to reflect people with a mental health problem who require emergency care, be it for, or as a result of, a mental health or physical health problem. On initial presentation to the emergency service provider (ambulance or ED), the cause of their healthcare condition/s (mental health and/or physical health) is often initially unknown. Due to this (1) the prevalence and range of underlying causes (mental and/or physical) of the patients presenting condition is unknown; (2) misattribution of physical symptoms to a mental health problem can occur and (3) diagnosis and treatment of the initial somatic complaint and cause(s) of the mental/physical health problem may be hindered. This study will name and define a new concept: 'mental dysregulation' in the context of ambulance and ED settings. Methods and analysis A Delphi study, informed by a rapid literature review, will be undertaken. For the literature review, a steering group (ie, persons with lived experience, ED and mental health clinicians, academics) will systematically search the literature to provide a working definition of the concept: mental dysregulation. Based on this review, statements will be generated regarding (1) the definition of the concept; (2) possible causes of mental dysregulation and (3) observable behaviours associated with mental dysregulation. These statements will be rated in three Delphi rounds to achieve consensus by an international expert panel (comprising persons with lived experience, clinicians and academics). Ethics and dissemination This study has been approved by the Medical Ethical Committee of the University of Applied Sciences Utrecht (reference number: 258-000-2023_Geurt van der Glind). Results will be disseminated via peer-reviewed journal publication(s), scientific conference(s) and to key stakeholders

The joint influence of marital status, interpregnancy interval, and neighborhood on small for gestational age birth: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>Interpregnancy interval (IPI), marital status, and neighborhood are independently associated with birth outcomes. The joint contribution of these exposures has not been evaluated. We tested for effect modification between IPI and marriage, controlling for neighborhood.</p> <p>Methods</p> <p>We analyzed a cohort of 98,330 live births in Montréal, Canada from 1997–2001 to assess IPI and marital status in relation to small for gestational age (SGA) birth. Births were categorized as subsequent-born with <it>short </it>(<12 months), <it>intermediate </it>(12–35 months), or <it>long </it>(36+ months) IPI, or as firstborn. The data had a 2-level hierarchical structure, with births nested in 49 neighborhoods. We used multilevel logistic regression to obtain adjusted effect estimates.</p> <p>Results</p> <p>Marital status modified the association between IPI and SGA birth. Being unmarried relative to married was associated with SGA birth for all IPI categories, particularly for subsequent births with <it>short </it>(odds ratio [OR] 1.60, 95% confidence interval [CI] 1.31–1.95) and <it>intermediate </it>(OR 1.48, 95% CI 1.26–1.74) IPIs. Subsequent births had a lower likelihood of SGA birth than firstborns. <it>Intermediate </it>IPIs were more protective for married (OR 0.50, 95% CI 0.47–0.54) than unmarried mothers (OR 0.65, 95% CI 0.56–0.76).</p> <p>Conclusion</p> <p>Being unmarried increases the likelihood of SGA birth as the IPI shortens, and the protective effect of <it>intermediate </it>IPIs is reduced in unmarried mothers. Marital status should be considered in recommending particular IPIs as an intervention to improve birth outcomes.</p

Ability to develop broadly neutralizing HIV-1 antibodies is not restricted by the germline Ig gene repertoire.

CAPRISA, 2015.Abstract available in pdf