Biology subjects

McGinnis, M.

Publications and source records attributed to McGinnis, M..

3 recordsLinked to original sources

bioRxiv2026

Kiss1 neurons in the medial amygdala of mice are sexually dimorphic and unique from hypothalamic anteroventral periventricular Kiss1 neurons in their action potential firing properties

Abstract The importance of hypothalamic kisspeptin (Kiss1) neurons in controlling the reproductive axis is well established, while a population of extra-hypothalamic Kiss1 neurons is found in the medial amygdala (MeA) of both males and females in rodents and is less well understood. The MeA is connected with the olfactory bulbs, the hypothalamus and cortical areas. MeA Kiss1 neurons have been implicated in sexual behaviour and modulation of the reproductive axis; however, little is known about their action potential firing properties, which would influence kisspeptin release in target brain regions, nor whether their physiological properties are sex- or estrous cycle-dependent. In this study, whole-cell patch-clamp recordings were made from Kiss1 neurons in brain slices containing the MeA of adult female (estrous and diestrous) and male mice. MeA Kiss1 (Kiss1MeA) neurons were sexually dimorphic, with greater numbers in male compared to female mice and a slower change in excitability in estrous females compared with males. However, combining a range of electrophysiological parameters using principal component analysis did not reveal a distinct sex- or estrous cycle-linked phenotype, suggesting that the properties of Kiss1MeA neurons- and therefore kisspeptin release- are broadly similar. Interestingly, Kiss1MeA neurons had unique electrophysiological properties compared with anteroventral periventricular (AVPV) hypothalamic Kiss1 (Kiss1AVPV) neurons in female mice; with their reduced excitability, achieving action potential firing frequencies greater than 10Hz required a larger current input, indicating that Kiss1MeA neurons require stronger synaptic input to achieve firing frequencies that drive kisspeptin release. These findings provide new information about the physiological properties of Kiss1MeA neurons, showing subtle sex differences and profound regional differences between the MeA and AVPV.

neuroscience↗

bioRxiv2026

A Cross-Trophic Amoebozoan Predator Consumes Trophozoites and Cysts of Naegleria and Acanthamoeba

Protistan predators are key regulators of microbial food webs, yet most are considered to occupy relatively narrow trophic niches. Here, we demonstrate that Mayorella spp. (Amoebozoa), isolated from marine and freshwater environments, exhibits exceptional trophic breadth spanning multiple trophic levels. Live-cell imaging revealed predation on bacteria, algae, dinoflagellates, diatoms, flagellates, ciliates, and multicellular prey including rotifers. Large or filamentous prey were engulfed whole or mechanically fragmented during ingestion. Notably, Mayorella consumed both trophozoites and cysts of free-living amoebae (Naegleria and Acanthamoeba), with clear digestion of cyst contents. Dense cultures showed aggregation around large prey and facultative cannibalism. Ingestion of microplastic-like particles occurred without evidence of digestion. Predator cell size and population density increased markedly when feeding on protist or mixed prey relative to bacterial diets, indicating pronounced trophic plasticity. These findings establish Mayorella as a broad-spectrum, cross-trophic predator with the capacity to exert top-down effects across microbial food webs and suggest a previously underappreciated role in the suppression of pathogenic free-living amoebae.

microbiology↗

bioRxiv2025

A new Paramoeba Isolate from Florida Exhibits a Microtubule-Bound Endosymbiont Closely Associated with the Host Nucleus

The genera Paramoeba and Neoparamoeba, within the family Paramoebidae (order Dactylopodida), are distinguished by their dactylopodial pseudopodia and the presence of an intracellular eukaryotic symbiont, the Perkinsela-like organism (PLO). Taxonomic classification within these genera has been challenging due to overlapping morphological traits and close phylogenetic relationships. Most species are marine, with some acting as significant parasites, contributing to sea urchin mass mortality and serving as causative agents of Amoebic Gill Disease (AGD). Despite their ecological and economic importance, many aspects of their diversity, biology, evolution, and host interactions remain poorly understood. In this study, we describe a novel amoeba species, Paramoeba daytoni n. sp., isolated from Daytona Beach, Florida. Morphological and molecular analyses confirm its placement within the Paramoeba clade, closely related to P. eilhardi, P. karteshi, and P. aparasomata. Phylogenetic assessments using 18S and COI markers demonstrate the limitations of 18S gene for species delineation, highlighting COI as a more reliable genetic marker for this group. Additionally, observations on PLO morphology, movement, and microtubule association provide insights into the endosymbiotic relationship, reinforcing the need for further research into this unique eukaryote-eukaryote symbiosis.

microbiology↗