Biology subjects

O'Hara, K.

Publications and source records attributed to O'Hara, K..

3 recordsLinked to original sources

bioRxiv2024

Real-time activity of dynorphin-expressing neurons in mouse central amygdala during alcohol drinking

Alcohol use disorder (AUD) is a chronic disease that poses significant economic burden and health risks. It is pivotal to better understand brain mechanisms engaged by alcohol that promote misuse. The central amygdala (CeA) has emerged as a key mediator of excessive preclinical alcohol consumption. A dynorphin-expressing subpopulation within the CeA (CeADyn) has been implicated in excessive alcohol drinking, yet how cellular activity of CeADyn neurons relates to ongoing alcohol drinking is not well-understood. The current study interrogated the engagement of CeADyn neurons in male and female mice during voluntary alcohol consumption using fiber photometry and compared this cellular response with that of other solutions having similar motivational and/or taste characteristics. Activity of a calcium sensor, GCaMP7f, expressed in mouse CeADyn neurons was recorded and time-locked to bouts of drinking. Multilevel linear mixed modeling was applied to better resolve focal effects from complex data. These analyses revealed a relatively large increase in CeADyn neuron calcium transients after bouts of alcohol drinking compared to water or sucrose drinking, indicating these neurons are uniquely engaged during alcohol consumption. Drinking behavior unique to alcohol (i.e., longer bout durations) did not fully explain signal differences between alcohol and other solutions nor did the relatively increased alcohol response diminish over time. No other conditions or solutions tested reproduced the pronounced change in CeADyn activity associated with alcohol drinking. These findings, collectively, support the presence of a unique functional signature for alcohol in a cell population known to control excessive alcohol drinking. HighlightsO_LICentral amygdala dynorphin cells (CeADyn) are firmly implicated in alcohol misuse. C_LIO_LICeADyn neuron activity was higher when mice drank alcohol versus other solutions. C_LIO_LINeither how mice drank alcohol nor motivational states could explain this activity. C_LIO_LICeADyn neurons having uniquely high alcohol responses may underlie AUD development. C_LI

neuroscience↗

bioRxiv2022

A fluorescently labelled quaternary ammonium compound (NBD-DDA) to study mode-of-action and resistance mechanisms in bacteria

Quaternary ammonium compounds (QACs) are widely used as active agents in disinfectants, antiseptics, and preservatives. Despite being in use since the 1940s, there remain multiple open questions regarding their detailed mode-of-action and the mechanisms, including phenotypic heterogeneity, that can make bacteria less susceptible to QACs. To facilitate mode-of-action studies, we synthesized a fluorescent analogue of the quaternary ammonium compound benzalkonium chloride, namely N-dodecyl-N,N-dimethyl-[2-[(4-nitro-2,1,3-benzoxadiazol-7-yl)amino]ethyl]azanium-iodide (NBD-DDA). NBD-DDA is readily detected by flow cytometry and fluorescence microscopy with standard GFP/FITC-settings, making it suitable for molecular and single-cell studies. NBD-DDA was then used to investigate resistance mechanisms which can be heterogeneous among individual bacterial cells. Our results reveal that the antimicrobial activity of NBD-DDA against E. coli, S. aureus and P. aeruginosa is comparable to that of benzalkonium chloride (BAC), a widely used QAC. Characteristic time-kill kinetics and increased tolerance of a BAC tolerant E. coli strain against NBD-DDA suggest that the mode of action of NBD-DDA is similar to that of BAC. Leveraging these findings and NBD-DDAs fluorescent properties, we show that reduced cellular adsorption is responsible for the evolved BAC tolerance in the BAC tolerant E. coli strain. As revealed by confocal laser scanning microscopy (CLSM), NBD-DDA is preferentially localized in the cell envelope of E. coli, which is a primary target of BAC and other QACs. Overall, NBD-DDAs antimicrobial activity, its fluorescent properties, and its ease of detection render it a powerful tool to study the mode-of-action and the resistance mechanisms of QACs in bacteria.

microbiology↗

bioRxiv2022

Evolutionary relationships and range evolution of greenhood orchids (subtribe Pterostylidinae): insights from plastid phylogenomics

Australia harbours a rich and highly endemic orchid flora with over 90% of native species found nowhere else. However, little is known about the assembly and evolution of Australias orchid flora. Here, we used a phylogenomic approach to infer evolutionary relationships, divergence times, and range evolution in Pterostylidinae (Orchidoideae), the second largest subtribe in the Australian orchid flora, comprising the genera Pterostylis and Achlydosa. Phylogenetic analysis of 75 plastid genes provided well-resolved and supported phylogenies. Intrageneric relationships in Pterostylis were clarified and monophyly of eight of ten sections supported. Achlydosa was found to not form part of Pterostylidinae and instead merits recognition at subtribal level, as Achlydosinae. Pterostylidinae were inferred to have originated in temperate eastern Australia in the early Oligocene, coinciding with the complete separation of Australia from Antarctica and the onset of the Antarctic Circumpolar Current, which led to profound changes in the worlds climate. Divergence of all major lineages occurred during the Miocene, accompanied by increased aridification and seasonality of the Australian continent, resulting in strong vegetational changes from rainforest to more open sclerophyllous vegetation. The majority of extant species were inferred to have originated in the Quaternary, from the Pleistocene onwards. The rapid climatic oscillations during the Pleistocene may have acted as important driver of speciation in Pterostylidinae. The subtribe underwent lineage diversification mainly within its ancestral range, in temperate eastern Australia. Long-distance dispersals to southwest Australia commenced from the late Miocene onwards, after the establishment of the Nullarbor Plain, which constitutes a strong edaphic barrier to mesic plants. Range expansions from the mesic into the arid zone of eastern Australia (Eremaean region) commenced from the early Pleistocene onwards. Extant distributions of Pterostylidinae in other Australasian regions, such as New Zealand and New Caledonia, are of more recent origin, resulting from long-distance dispersals from the Pliocene onwards. Temperate eastern Australia was identified as key source area for dispersals to other Australasian regions.

evolutionary biology↗