Browsing by Author "Bennett, Monique"

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    CASA in invertebrates
    (CSIRO Publishing, 2018) van der Horst, Gerhard; Bennett, Monique; Bishop, John D. D.
    Sperm movement has been described in several phyla of invertebrates. Yet, sperm motility has only been quantified using computer-aided sperm analysis (CASA-Mot) in externally fertilising species (broadcast spawners) of two phyla, molluscs and echinoderms. In the present study we quantified in detail the nature of the sperm tracks, percentage motility groupings and detailed kinematics of rapid-, medium- and slow-swimming spermatozoa in the oyster Crassostrea gigas and four species never previously studied by CASA-Mot, namely the molluscs Choromytilus meridionalis, Donax serra and Haliotis midae and the echinoderm Parechinus angulosus. A feature common to all these species are the helical tracks, the diameter of which seems to be species specific. Using CASA-Mot, the behaviour of spermatozoa was also studied over time and in the presence of egg water and Ca2+ modulators such as caffeine and procaine hydrochloride. For the first time, we show that hyperactivation can be induced in all species in the presence of egg water (sea water that was mixed with mature eggs and then centrifuged) and/or caffeine, and these hyperactivated sperm tracks were characterised using CASA-Mot. We relate the different patterns of sperm motility and behaviour to reproductive strategies such as broadcast spawning and spermcasting, and briefly review studies using CASA-Mot on other invertebrates.
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    Human sperm as an in vitro toxicity model: a versatile tool for assessing the risk of environmental contaminants
    (Springer Science and Business Media Deutschland GmbH, 2025) Keyser, Shannen; Davidse, Morgan; Bennett, Monique; Maree, Liana; Petrik, Leslie
    Contaminants of emerging concern (CECs) pose a significant threat to human and ecosystem health due to their persistence, bioaccumulation in higher trophic levels, and potential toxicity. While in vivo models are commonly used for toxicity screening, developing alternative in vitro techniques for rapid environmental risk assessment is essential. Spermatozoa, with their compartmentalized structure, measurable characteristics and sensitivity to environmental changes, offer potential as an in vitro model for toxicity screening. We evaluated the impact of selected CECs, including pharmaceuticals and pesticides, on sperm function in highly motile sperm subpopulations selected from donor semen. Standardised protocols were applied to assess various sperm functional parameters after 1–4 h of exposure to either individual or a mixture of chemicals. Our findings revealed that total motility is insufficient to detect subtle toxic effect. More responsive measures, such as sperm kinematics, induced hyperactivation, viability, mitochondrial membrane potential (MMP) and presence of reactive oxygen species (ROS) should be assessed to elucidate the effect of a toxic environment on sperm function. Most chemicals exerted a dose–response effect on sperm parameters, with the higher concentrations resulting in the most negative effects. The inherent sensitivity of human spermatozoa to oxidative stress, mitochondrial damage and energy metabolism, makes them a robust model for assessing toxicity. These features highlight their utility as an alternative cellular model for evaluating CECs and advancing risk assessment methodologies.