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Hamlin, Adam
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Given Name
Adam
Adam
Surname
Hamlin
UNE Researcher ID
une-id:ahamlin
Email
ahamlin@une.edu.au
Preferred Given Name
Adam
School/Department
School of Science and Technology
27 results
Now showing 1 - 10 of 27
- PublicationAnticipatory Behavior for a Mealworm Reward in Laying Hens Is Reduced by Opioid Receptor Antagonism but Not Standard Feed IntakeIt is widely accepted that the absence of suffering no longer defines animal welfare and that positive affective experiences are imperative. For example, laying hens may be housed in environments that do not cause chronic stress but may lack particular resources that promote positive affective experiences, such as conspecifics or effective enrichment. Despite a consensus of how important positive affect is for animal welfare, they are difficult to identify objectively. There is a need for valid and reliable indicators of positive affect. Pharmacological interventions can be an effective method to provide insight into affective states and can assist with the investigation of novel indicators such as associated biomarkers. We aimed to validate a pharmacological intervention that blocks the subjective hedonistic phase associated with reward in laying hens via the administration of the non-selective (μ, δ, and κ) opioid receptor antagonist, nalmafene. We hypothesized that nonfood deprived, hens that did not experience a positive affective state when presented with a mealworm food reward due to the administration of nalmefene, would show minimal anticipatory and consummatory behavior when the same food reward was later presented. Hens (n = 80) were allocated to treatment groups, receiving either nalmefene or vehicle (0.9% saline) once or twice daily, for four consecutive days. An anticipatory test (AT) was performed on all days 30 min post-drug administration. Behavioral responses during the appetitive and consummatory phase were assessed on days 1, 3 and 4. Anticipatory behavior did not differ between treatment groups the first time hens were provided with mealworm food rewards. However, antagonism of opioid receptors reduced anticipatory and consummatory behavior on days 3 and 4. Feed intake of standard layer mash was not impacted by treatment, thus nalmefene reduced non-homeostatic food consumption but not homeostatic consumption. Behavioral observations during the AT provided no evidence that nalmefene treated hens were fearful, sedated or nauseous. The results suggest that we successfully blocked the hedonistic subjective component of reward in laying hens and provide evidence that this method could be used to investigate how hens perceive their environment and identify associated novel indicators to assess hen welfare.
- PublicationDrying at high temperature for a short time maximizes the recovery of olive leaf biophenolsIn the current study, recovery of phenolic compounds from fresh, air-dried, freeze-dried and oven-dried (at 60°C and 105°C) olive leaves was investigated. The phenol content and antioxidant activity were assessed by gross quantitative methods such as total phenol content (Folin-Ciocalteu's method), total flavonoid content, total o-diphenol content and total antioxidant capacity using ABTS+° and DPPH° scavenging assays. In addition, the phenolic composition of extracts was determined by high performance liquid chromatography (HPLC) equipped with diode array detection (DAD) with tandem mass (MS/MS) and the contribution of individual phenolic components to the antioxidant activity of extracts were evaluted by online ABTS scavenging assay. Extracts obtained from oven-dried leaves at 105°C showed the highest phenol recoveries and antioxidant activities, whereas extracts obtained from oven-dried leaves at 60°C had the lowest values. Oven drying of olive leaves at 105°C for three hours increased oleuropein recovery up to 38 fold as compared with fresh olive leaves. Our results stress the paramount importance of sample pre-treatment in the preparation and analysis of herbal medicines. Furthermore, we highlight the limitations of sole dependence on gross assessment of total phenolic composition and total antioxidant activity in studying plant samples.
- PublicationGroup A streptococcal antigen exposed rat model to investigate neurobehavioral and cardiac complications associated with post-streptococcal autoimmune sequelae(John Wiley & Sons, Inc, 2021-06)
; ; Background: The neuropsychiatric disorders due to post-streptococcal autoimmune complications such as Sydenham's chorea (SC) are associated with acute rheumatic fever and rheumatic heart disease (ARF/RHD). An animal model that exhibits characteristics of both cardiac and neurobehavioral defects in ARF/RHD would be an important adjunct for future studies. Since age, gender, strain differences, and genotypes impact on the development of autoimmunity, we investigated the behavior of male and female Wistar and Lewis rat strains in two age cohorts (<6 weeks and >12 weeks) under normal husbandry conditions and following exposure to group A streptococcus (GAS).
Methods: Standard behavioral assessments were performed to determine the impairments in fine motor control (food manipulation test), gait and balance (beam walking test), and obsessive-compulsive behavior (grooming and marble burying tests). Furthermore, electrocardiography, histology, and behavioral assessments were performed on male and female Lewis rats injected with GAS antigens.
Results: For control Lewis rats there were no significant age and gender dependent differences in marble burying, food manipulation, beam walking and grooming behaviors. In contrast significant age-dependent differences were observed in Wistar rats in all the behavioral tests except for food manipulation. Therefore, Lewis rats were selected for further experiments to determine the effect of GAS. After exposure to GAS, Lewis rats demonstrated neurobehavioral abnormalities and cardiac pathology akin to SC and ARF/RHD, respectively.
Conclusion: We have characterised a new model that provides longitudinal stability of age-dependent behavior, to simultaneously investigate both neurobehavioral and cardiac abnormalities associated with post-streptococcal complications.
- PublicationOlive (Olea europaea L.) Biophenols: A Nutriceutical against Oxidative Stress in SH-SY5Y Cells(MDPI AG, 2017)
; Obied, Hassan KPlant biophenols have been shown to be effective in the modulation of Alzheimer's disease (AD) pathology resulting from free radical-induced oxidative stress and imbalance of the redox chemistry of transition metal ions (e.g., iron and copper). On the basis of earlier reported pharmacological activities, olive biophenols would also be expected to have anti-Alzheimer's activity. In the present study, the antioxidant activity of individual olive biophenols (viz. caffeic acid, hydroxytyrosol, oleuropein, verbascoside, quercetin, rutin and luteolin) were evaluated using superoxide radical scavenging activity (SOR), hydrogen peroxide (H2O2) scavenging activity, and ferric reducing ability of plasma (FRAP) assays. The identification and antioxidant activities in four commercial olive extracts-Olive leaf extractTM (OLE), Olive fruit extractTM (OFE), Hydroxytyrosol ExtremeTM (HTE), and Olivenol plusTM (OLP)-were evaluated using an on-line HPLC-ABTS•+ assay, and HPLC-DAD-MS analysis. Oleuropein and hydroxytyrosol were the predominant biophenols in all the extracts. Among the single compounds examined, quercetin (EC50: 93.97 μM) and verbascoside (EC50: 0.66 mM) were the most potent SOR and H2O2 scavengers respectively. However, OLE and HTE were the highest SOR (EC50: 1.89 μg/mL) and H2O2 (EC50: 115.8 μg/mL) scavengers among the biophenol extracts. The neuroprotection of the biophenols was evaluated against H2O2-induced oxidative stress and copper (Cu)-induced toxicity in neuroblastoma (SH-SY5Y) cells. The highest neuroprotection values (98% and 92%) against H2O2-induced and Cu-induced toxicities were shown by the commercial extract HTETM. These were followed by the individual biophenols, caffeic acid (77% and 64%) and verbascoside (71% and 72%). Our results suggest that olive biophenols potentially serve as agents for the prevention of neurodegenerative diseases such as AD, and other neurodegenerative ailments that are caused by oxidative stress. - PublicationBasal forebrain atrophy contributes to allocentric navigation impairment in Alzheimer's disease patients(Frontiers Research Foundation, 2015)
; - PublicationPharmacological intervention of the reward system in the laying hen has an impact on anticipatory behaviour(Wageningen Academic Publishers, 2019)
; ; Valid reliable indicators of positive affective state are a critical component of welfare assessments, however, these are currently lacking for laying hens. Pharmacological interventions that disrupt specific neural pathways have shown to be a useful tool when validating indicators of affective states. As such, we utilised and validated the μ-opioid receptor antagonist nalmefene to block the reward pathway in laying hens. - PublicationQuantitative determination of neuronal size and density using flow cytometryBackground: Recent anthropomorphic disturbances are occurring at an increasing rate leading to organisms facing a variety of challenges. This change is testing the information processing capacity (IPC) of all animals. Brain function is widely accepted to be influenced by a variety of factors, including relative size, number of neurons and neuronal densities. Therefore, in order to understand what drives an animals IPC, a methodological approach to analyze these factors must be established.
New method: Here we created a protocol that allowed for high-throughput, non-biased quantification of neuronal density and size across six regions of the brain. We used the Isotropic Fractionator method in combination with flow cytometry to identify neuronal and non-neuronal cells in the brains of adult rats.
Comparison with existing methods: The results obtained were comparable to those identified using stereological counting methods.
Results: By employing this new method, the number of nuclei in a specific brain region can be compared between replicate animals within an experiment. By calibrating the forward scatter channel of the flow cytometer with size standard beads, neuronal and non-neuronal nuclear sizes can be estimated simultaneously with nuclei enumeration. These techniques for nuclear counting and size estimation are technically and biologically reproducible.
Conclusion: Use of flow cytometry provides a methodological approach that allows for consistency in research, so that information on brain morphology, and subsequent function, will become comparable across taxa. - PublicationRequirements for a Robust Animal Model to Investigate the Disease Mechanism of Autoimmune Complications Associated With ARF/RHD(Frontiers Research Foundation, 2021-05-05)
; ; - PublicationDevelopment and characterisation of a laboratory model of post streptococcal autoimmune cardiac and neurobehavioral complications - Dataset(University of New England, 2022-06-17)
; ; ; In this dataset we have provided data on behavioural assessment on rats before and after exposure to streptococcal antigens, histological changes and antibody responses against host tissue proteins. Behavioural tests such as food manipulation, beam walking, grooming, marble burying and light/dark box tests were performed to assess the changes in fine motor coordination, gait and balance, obsessive-compulsive behaviour and anxiety like behaviour respectively before and after exposure to streptococcal antigens. Heart tissues were dissected from rats and stained with haematoxylin and eosin stain and scored them for infiltration of mononuclear cells in the myocardium and valvular tissues. ELISAs were performed on serum collected from rats to assess the antibody response against host tissue proteins following exposure to streptococcal antigens.
- PublicationA review of the antimicrobial side of antidepressants and its putative implications on the gut microbiomeObjective: Serotonin reuptake inhibitors are the predominant treatment for major depressive disorder. In recent years, the diversity of the gut microbiota has emerged to play a significant role in the occurrence of major depressive disorder and other mood and anxiety disorders. Importantly, the role of the gut microbiota in the treatment of such disorders remains to be elucidated. Here, we provide a review of the literature regarding the effects of physiologically relevant concentrations of serotonin reuptake inhibitors on the gut microbiota and the implications this might have on their efficacy in the treatment of mood disorders.
Methods: First, an estimation of gut serotonin reuptake inhibitor concentrations was computed based on pharmacokinetic and gastrointestinal transit properties of serotonin reuptake inhibitors. Literature regarding the in vivo and in vitro antimicrobial properties of serotonin reuptake inhibitors was gathered, and the estimated gut concentrations were examined in the context of these data. Computer-based investigation revealed putative mechanisms for the antimicrobial effects of serotonin reuptake inhibitors.
Results: In vivo evidence using animal models shows an antimicrobial effect of serotonin reuptake inhibitors on the gut microbiota. Examination of the estimated physiological concentrations of serotonin reuptake inhibitors in the gastrointestinal tract collected from in vitro studies suggests that the microbial community of both the small intestine and the colon are exposed to serotonin reuptake inhibitors for at least 4 hours per day at concentrations that are likely to exert an antimicrobial effect. The potential mechanisms of the effect of serotonin reuptake inhibitors on the gut microbiota were postulated to include inhibition of efflux pumps and/or amino acid transporters.
Conclusion: This review raises important issues regarding the role that gut microbiota play in the treatment of moodrelated behaviours, which holds substantial potential clinical outcomes for patients suffering from major depressive disorder and other mood-related disorders.
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