Biology subjects

Valentim, A. M.

Publications and source records attributed to Valentim, A. M..

5 recordsLinked to original sources

bioRxiv2025

Embryonic Spinocerebellar Ataxia Type 37 AUUUC Repeat RNA Causes Neurodevelopmental Defects in Zebrafish

Onset of many neurodegenerative and neuromuscular diseases usually starts in adulthood; however, recent advances point toward neurodevelopmental changes as drivers of late neurodegeneration. How early neuropathological features occur in these conditions remains unclear, which is critical for timely therapeutic intervention. Here, we provide evidence that neurodevelopmental axonal defects initiate a motor phenotype in a zebrafish model of spinocerebellar ataxia type 37 (SCA37), a degenerative hereditary condition caused by an ATTTC repeat in the DAB1 gene. We investigated neuronal defects triggered by the embryonic AUUUC repeat RNA and their effects later in life by transiently expressing this RNA in embryos and analyzing innervation and motor function. We found abnormalities in motor neuron axonal outgrowth and muscle innervation. We also discovered disrupted embryonic motor activity and reduced locomotor distance and velocity in late adult zebrafish, demonstrating motor impairment. Moreover, we showed that NOVA2 expression rescues axonal defects, indicating dysfunction of NOVA2-regulated neurodevelopmental processes. Overall, our results establish embryonic expression of the AUUUC repeat RNA as a driver of axonal and synaptic abnormalities, interfering with neuronal circuits and culminating in adult motor dysfunction.

neuroscience↗

bioRxiv2023

Validation of the in-house designed one-trial inhibitory avoidance test for two strains of adult zebrafish

Open-source validated tools are important for affordable high-quality science. Zebrafish model is often used in behavioral sciences, thus validated tools must be developed for this species. We aimed to implement the memory task one-trial inhibitory avoidance test in our laboratory by creating a custom-built 3D printed apparatus and custom-made hardware and software using microcontrollers; this decreases the costs and increases methodological flexibility. In this task, a mild electric shock (3.3 {+/-} 0.3V and 2A for 5sec) is used as an aversive stimulus for the one-trial inhibitory avoidance task based on classical conditioning. For this study we used 72-adult zebrafish from the AB and TU strain. The aversive stimulus caused a robust and long-lasting memory that was learned in one session. The apparatus consisted in one aquarium with two compartments (white and black) where, during the conditioning session, the shock was delivered in the preferred side (black), followed by 30min of immersion in 20M MK-801, a compound known for inducing amnesia (amnesic group, n= 20 for AB and 17 for TU), or in clean water (control, n= 20 for AB and 15 for TU). Both the AB and TU strain animals from the control group took more time to enter in the black compartment after conditioning (p[≤]0.039), indicating avoidance for the black side, while the latency was not altered in the MK-801 group, demonstrating impaired memory. In summary, this open-source apparatus is an affordable and validated option for memory assessment for the two most used strains of zebrafish in research.

animal behavior and cognition↗

bioRxiv2023

Housing conditions affect adult zebrafish (Danio rerio) behavior but not their physiological status

Zebrafish is a valuable model for neuroscience research, but the housing conditions to which it is daily exposed may be impairing its welfare status. The use of environmental enrichment and the refinement of methodology for cortisol measurement could reduce stress, improving its welfare and its suitability as an animal model used in stress research. Thus, this study aimed to evaluate (I) the influence of different housing conditions on zebrafish physiology and behavior and (II) skin mucus potential for cortisol measurement in adult zebrafish. For this, AB zebrafish were raised under barren or enriched (PVC pipes and gravel image) environmental conditions. After 6 months, the behavior was assessed by different behavioral paradigms (shoaling, white-black box test, and novel tank). The physiological response was also evaluated through cortisol levels (whole-body homogenates and skin mucus) and brain oxidative stress markers. Results revealed that enriched-housed fish had an increased nearest neighbors distance and reduced activity. However, no effect on body length or stress biomarkers was observed; whole-body and skin mucus cortisol levels had the same profile between groups. In conclusion, this study highlights the skin mucus potential as a matrix for cortisol quantification and how environmental enrichment could influence the data in future studies. Simple SummaryThe delivery of proper housing conditions may translate into good fish welfare. As zebrafish housing is usually poorly enriched, the fish could be unable to express some natural behaviors, leading to distress and/ or stress mechanisms dysregulation. This work focused on the examination of zebrafish welfare raised under different housing conditions (barren or environmentally enriched) and the testing of a low-invasive technique (skin mucus collection) to measure the main stress hormone (cortisol). The data was processed to assess body length, behavior, and physiological status. Results revealed that enrichment induced minor alterations on zebrafish behavior. Thus, the influence of housing conditions should be considered in future research, depending on the purpose of the study. Also, skin mucus appears to be a promising matrix to replace whole-body to measure cortisol in zebrafish, since its collection is nonlethal and showed similar results to the traditional method.

animal behavior and cognition↗

bioRxiv2021

Adult zebrafish anaesthesia: a study of efficacy and behavioural recovery of different anaesthetics

The use of proper anaesthesia in zebrafish research is essential to ensure fish welfare and data reliability. However, anaesthesia long-term side effects remain poorly understood. The purpose of this study was to assess anaesthesia quality and recovery in adult zebrafish using different anaesthetic protocols and to determine possible long-term effects on the fish activity and anxiety-like behaviours after anaesthesia. Mixed sex adult AB zebrafish were randomly assigned to 5 different groups (control, 175mg/L MS222, 45 mg/L clove oil, 2 mg/L etomidate and 5mg/L propofol combined with 150mg/L lidocaine) and placed in the respective anaesthetic bath. Time to lose the equilibrium, response to touch and to tail pinch stimuli, and recovery after anaesthesia administration were evaluated. In addition, after stopping anaesthesia, respiratory rate, activity and anxiety-like behaviours in the novel tank test were studied. Overall, all protocols proved to be adequate for zebrafish anaesthesia research as they showed full recovery at 1h, and only etomidate had minor effects on fish behaviour in the novel tank, a validated test for anxiety.

animal behavior and cognition↗

bioRxiv2019

Lighter compared to deeper isoflurane anaesthesia can affect recognition memory in male C57BL/6 mice

Concerns have been raised about how deeply patients are anaesthetized, and the effects that different depths of anaesthesia may have after recovery. In order to study the anaesthetic drugs per se, and to eliminate the effect of clinical variables, several animal studies have been published. Isoflurane induced transient deficits on spatial memory at low concentrations, affecting the hippocampus. However, the influence of different concentrations of isoflurane on non-spatial memory still needs clarification. Thus, our aim was to study the effects of different depths of anaesthesia (1% and 2% isoflurane) on a non-spatial memory task, the object recognition test, in C57BL/6 adult mice.\n\nTwenty-eight 2-month-old C57BL/6 male mice were habituated to the test arena of the object recognition test for 10 min each day over 2 days before anaesthesia. Mice were then randomly allocated in different treatment groups: 1% or 2%, anaesthetized with 1% or 2% of isoflurane, respectively, for 1 h or the control group, which was not anaesthetised. Twenty-four hours after anaesthesia, the animals were placed in an arena with two identical objects and allowed to explore for 10 min-Sample Trial. One hour later, mice were allowed to explore the arena for 10 min in the presence of one of the objects presented in the previous trial (familiar object) and a novel object - Choice Trial. The time spent exploring each object was evaluated by a blinded analysis. The recognition of one object as familiar was detected based on a higher level of exploration of the novel object.\n\nAnimals that were anaesthetized previously with 2% isoflurane performed at control levels, indicating the recognition of a familiar object in the object recognition task; this contrasted with the results of the group that was anaesthetized with 1% isoflurane.\n\nLighter (1%) rather than deeper (2%) isoflurane anaesthesia may affect non-spatial memory in C57BL/6 male mice. Our results raise awareness of the need for careful consideration of the depth of anaesthesia used, especially the use of light isoflurane anaesthesia, which is often chosen to provide animal immobilization during non-invasive procedures.

animal behavior and cognition↗