Rodent Studies Research Articles

Translational approaches to the neurobiological study of conditional discrimination and inhibition: Implications for psychiatric disease.

There is a growing number of studies investigating discriminatory fear conditioning and conditioned inhibition of fear to assess safety learning, in addition to extinction of cued fear. Despite all of these paradigms resulting in a reduction in fear expression, there are nuanced differences among them, which could be mediated through distinct behavioral and neural mechanisms. These differences could impact how we approach potential treatment options in clinical disorders with dysregulated fear responses. The objective of this review is to give an overview of the conditional discrimination and inhibition findings reported in both animal models and human neuropsychiatric disorders. Both behavioral and neural findings are reviewed among human and rodent studies that include conditional fear discrimination via conditional stimuli with and without reinforcement (CS+ vs. CS-, respectively) and/or conditional inhibition of fear through assessment of the fear response to a compound CS-/CS+ cue versus CS+. There are several parallels across species in behavioral fear expression as well as neural circuits promoting fear reduction in response to a CS- and/or CS-/CS+ compound cue. Continued and increased efforts to compare similar behavioral fear inhibition paradigms across species are needed to make breakthrough advances in our understanding and treatment approaches to individuals with fear disorders. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The use of the micronucleus test and comet assay in wild rodents: a historical review and future perspectives.

Rodents are considered good models for investigating genotoxic damage and mutagenic alterations caused by xenobiotic agents, due to their occupation of a wide variety of habitats. However, relatively few in situ studies have focused on DNA damage in wild rodents associated with environmental exposure. In this review, we investigate trends in the application of the micronucleus test and comet assay in in situ studies of wild rodents. A total of 33 papers were identified, distributed across 14 different countries. Brazil and Spain had the most published studies (six each), followed by Bulgaria (n = 5), Mexico (n = 4) and Italy (n = 3). Only 24 of the 2,652 recognized rodent species have been the subject of in situ studies, which have most frequently focus on species of the genus Mus. The protocols used for the micronucleus test and comet assay varied widely, although blood and bone marrow were the primary types of tissue used. Given the paucity of studies on wild rodents, we recommend further research, particularly focusing on the use of this group as bioindicators of environmental quality and the standardization of protocols.

Exercise-induced appetite suppression: An update on potential mechanisms.

The first systematic reviews of the effects of exercise on appetite-regulation and energy intake demonstrated changes in appetite-regulating hormones consistent with appetite suppression and decreases in subsequent relative energy intake over a decade ago. More recently, an intensity-dependent effect and several potential mechanisms were proposed, and this review aims to highlight advances in this field. While exercise-induced appetite suppression clearly involves acylated ghrelin, glucagon-like peptide-1 may also be involved, though recent evidence suggests peptide tyrosine tyrosine may not be relevant. Changes in subjective appetite perceptions and energy intake continue to be equivocal, though these results are likely due to small sample sizes and methodological inconsistencies. Of the proposed mechanisms responsible for exercise-induced appetite suppression, lactate has garnered the most support through invitro and invivo rodent studies as well as a growing amount of work in humans. Other potential modulators of exercise-induced appetite suppression may include sex hormones, growth-differentiation factor 15, Lac-Phe, brain-derived neurotrophic factor, and asprosin. Research should focus on the mechanisms responsible for the changes and consider these other modulators (i.e., myokines/exerkines) of appetite to improve our understanding of the role of exercise on appetite regulation.

Goal-directed learning is multidimensional and accompanied by diverse and widespread changes in neocortical signaling.

New tasks are often learned in stages with each stage reflecting a different learning challenge. Accordingly, each learning stage is likely mediated by distinct neuronal processes. And yet, most rodent studies of the neuronal correlates of goal-directed learning focus on individual outcome measures and individual brain regions. Here, we longitudinally studied mice from naïve to expert performance in a head-fixed, operant conditioning whisker discrimination task. In addition to tracking the primary behavioral outcome of stimulus discrimination, we tracked and compared an array of object-based and temporal-based behavioral measures. These behavioral analyses identify multiple, partially overlapping learning stages in this task, consistent with initial response implementation, early stimulus-response generalization, and late response inhibition. To begin to understand the neuronal foundations of these learning processes, we performed widefield Ca2+ imaging of dorsal neocortex throughout learning and correlated behavioral measures with neuronal activity. We found distinct and widespread correlations between neocortical activation patterns and various behavioral measures. For example, improvements in sensory discrimination correlated with target stimulus evoked activations of response-related cortices along with distractor stimulus evoked global cortical suppression. Our study reveals multidimensional learning for a simple goal-directed learning task and generates hypotheses for the neuronal modulations underlying these various learning processes.

Turn off that night light! Light-at-night as a stressor for adolescents.

Light-at-night is known to produce a wide variety of behavioral outcomes including promoting anxiety, depression, hyperactivity, abnormal sociability, and learning and memory deficits. Unfortunately, we all live in a 24-h society where people are exposed to light-at-night or light pollution through night-shift work - the need for all-hours emergency services - as well as building and street-lights, making light-at-night exposure practically unavoidable. Additionally, the increase in screentime (tvs and smart devices) during the night also contributes to poorer sleep and behavioral impairments. Compounding these factors is the fact that adolescents tend to be "night owls" and prefer an evening chronotype compared to younger children and adults, so these teenagers will have a higher likelihood of being exposed to light-at-night. Making matters worse is the prevalence of high-school start times of 8 am or earlier - a combination of too early school start times, light exposure during the night, and preference for evening chronotypes is a recipe for reduced and poorer sleep, which can contribute to increased susceptibility for behavioral issues for this population. As such, this mini-review will show, using both human and rodent model studies, how light-at-night affects behavioral outcomes and stress responses, connecting photic signaling and the circadian timing system to the hypothalamic-pituitary adrenal axis. Additionally, this review will also demonstrate that adolescents are more likely to exhibit abnormal behavior in response to light-at-night due to changes in development and hormone regulation during this time period, as well as discuss potential interventions that can help mitigate these negative effects.

Dynamics of HSD17B3 expression in human fetal testis: implications for the role of Sertoli cells in fetal testosterone biosynthesis.

Introduction: Androgens play a pivotal role in shaping male sexual characteristics, with testosterone being an essential hormone in orchestrating various developmental processes. Testosterone biosynthesis involves a series of enzymatic reactions, among which the 17β-hydroxysteroid dehydrogenase type 3 (HSD17B3) holds significance. While its role in adult Leydig cells is well established, its localization and importance during the fetal period remain less known, especially in humans. This study aims to delineate the dynamics of HSD17B3 expression in human fetal testes to clarify the contribution of specific cell types to testosterone biosynthesis. Methods: Using immunofluorescence staining, we investigated the expression pattern of HSD17B3 in human fetal and adult testicular tissues. Results and discussion: The findings of this study revealed a distinct temporal and cellular expression pattern of HSD17B3 protein in the fetal period. We detected its expression exclusively in Sertoli cells, the highest during the second trimester. This unique localization suggests the inclusion of fetal Sertoli cells in testosterone production during the critical masculinization-programming window. Furthermore, we demonstrated a shift in HSD17B3 expression from Sertoli cells to Leydig cells in adulthood, corroborating findings from rodent studies. This study sheds light on the intricate, still underexplored regulation of steroidogenesis during fetal development, whose disturbance might lead to testicular dysgenesis. Further research is warranted to elucidate the regulatory pathways governing the expression of HSD17B3 and its transition between Sertoli and Leydig cells, potentially paving the way for novel therapeutic interventions in disorders of sexual development.

Efficacy of ginsenoside Rg1 on rodent models of depression: A systematic review and meta-analysis.

Depression is a prevalent psychiatric disease, and ginsenoside Rg1 is a bioactive compound extracted from the root of Panax ginseng C.A.Mey. To systematically investigate the effectiveness of Rg1 in rodent models of depression and provide evidence-based references for treating depression. Electronic searches for rodent studies were performed from inception to October 2022, e.g., PUBMED and EMBASE. Data extraction and quality evaluation were performed for the references, and meta-analysis was performed on the selected data using Review Manager 5.3.5. The outcomes were analyzed via a random-effect model and presented as mean difference (MD) with 95% confidence intervals (CIs). A total of 24 studies and 678 animals were included in this meta-analysis. Rg1 remarkably improved depressive-like symptoms of depressed rodents, including the sucrose preference test (25.08, 95% CI: 20.17-30.00, Z = 10.01, P < 0.00001), forced swimming test (MD = -37.69, 95% CI: (-45.18, -30.2); Z = 9.86, P < 0.00001), and the tail suspension test (MD = -22.93, seconds, 95% CI: (-38.49, -7.37); Z = 2.89, P = 0.004). The main antidepressant mechanism of Rg1 was concluded to be the neurotransmitter system, oxidant stress system, and inflammation. Conclusively, this study indicated the possible protective and therapeutic effects of Rg1 for treating depression via multiple mechanisms.

Ghrelin, Neuroinflammation, Oxidative Stress, and Mood Disorders: What Are the Connections?

Ghrelin is a gut peptide hormone associated with feeding behavior and energy homeostasis. Acylated ghrelin binds to the growth hormone secretagogue receptor 1a subtype (GHS-R1a) in the hippocampus, leading to GH release from the anterior pituitary. However, in recent years, ghrelin and its receptor have also been implicated in other processes, including the regulation of cardiomyocyte function, muscle trophism, and bone metabolism. Moreover, GHS-R1a is distributed throughout the brain and is expressed in brain areas that regulate the stress response and emotional behavior. Consistently, a growing body of evidence supports the role of ghrelin in regulating stress response and mood. Stress has consistently been shown to increase ghrelin levels, and despite some inconsistencies, both human and rodent studies suggested antidepressant effects of ghrelin. Nevertheless, the precise mechanism by which ghrelin influences stress response and mood remains largely unknown. Intriguingly, ghrelin and GHS-R1a were consistently reported to exert anti-inflammatory, antioxidant, and neurotrophic effects both in vivo and in vitro, although this has never been directly assessed in relation to psychopathology. In the present review we will discuss available literature linking ghrelin with the stress response and depressive-like behavior in animal models as well as evidence describing the interplay between ghrelin and neuroinflammation/oxidative stress. Although further studies are required to understand the mechanisms involved in the action of ghrelin on mood, we hypothesize that the antiinflammatory and anti-oxidative properties of ghrelin may give a key contribution.

Mitigating skeletal muscle wasting in unloading and augmenting subsequent recovery.

Skeletal muscle wasting is the hallmark pathophysiological adaptation to unloading or disuse that demonstrates the dependency on frequent mechanical stimulation (e.g. muscle activation and subsequent loading) for homeostasis of normally load-bearing muscles. In the absence of mitigation strategies, no mammalian organism is resistant to muscle atrophy driven by unloading. Given the profound impact of unloading-induced muscle wasting on physical capacity, metabolic health and immune function; mitigation strategies during unloading and/or augmentation approaches during recovery have broad healthcare implications in settings of bed-bound hospitalization, cast immobilization and spaceflight. This topical review aims to: (1) provide a succinct, state-of-the-field summary of seminal and recent findings regarding the mechanisms of unloading-induced skeletal muscle wasting; (2) discuss unsuccessful vs. promising mitigation and recovery augmentation strategies; and (3) identify knowledge gaps ripe for future research. We focus on the rapid muscle atrophy driven by relatively short-term mechanical unloading/disuse, which is in many ways mechanistically distinct from both hypermetabolic muscle wasting and denervation-induced muscle atrophy. By restricting this discussion to mechanical unloading during which all components of the nervous system remain intact (e.g. without denervation models), mechanical loading requiring motor and sensory neural circuits in muscle remain viable targets for both mitigation and recovery augmentation. We emphasize findings in humans with comparative discussions of studies in rodents which enable elaboration of key mechanisms. We also discuss what is currently known about the effects of age and sex as biological factors, and both are highlighted as knowledge gaps and novel future directions due to limited research.

Weighing in on the role of brown adipose tissue for treatment of obesity.

Brown adipose tissue (BAT) activation is an emerging target for obesity treatments due to its thermogenic properties stemming from its ability to shuttle energy through uncoupling protein 1 (Ucp1). Recent rodent studies show how BAT and white adipose tissue (WAT) activity can be modulated to increase the expression of thermogenic proteins. Consequently, these alterations enable organisms to endure cold-temperatures and elevate energy expenditure, thereby promoting weight loss. In humans, BAT is less abundant in obese subjects and impacts of thermogenesis are less pronounced, bringing into question whether energy expending properties of BAT seen in rodents can be translated to human models. Our review will discuss pharmacological, hormonal, bioactive, sex-specific and environmental activators and inhibitors of BAT to determine the potential for BAT to act as a therapeutic strategy. We aim to address the feasibility of utilizing BAT modulators for weight reduction in obese individuals, as recent studies suggest that BAT's contributions to energy expenditure along with Ucp1-dependent and -independent pathways may or may not rectify energy imbalance characteristic of obesity.

Standard diet and animal source influence hippocampal spatial reference learning and memory in congenic C57BL/6J mice.

Assessing learning and memory has become critical to evaluate brain function in health, aging or neurological disease. The hippocampus is crucially involved in these processes as illustrated by H.M.'s remarkable case and by the well-established early symptoms of Alzheimer's disease. Numerous studies have reported the impact of gut microbiota on hippocampal structure and function using pro-, pre- and antibiotics, diet manipulations, germ-free conditions or fecal transfer. However, most diet manipulations have relied on Western diet paradigms (high fat, high energy, high carbohydrates). Here, we compared the impact of two standard diets, 5K52 and 2918 (6% fat, 18% protein, 3.1kcal/g), and how they influenced hippocampal learning and memory in adult 6-month-old congenic C57BL/6J mice from two sources. Using a hippocampal-dependent task, we found that 5K52-fed mice performed consistently better than 2918-fed animals in the Barnes circular maze. These behavioral differences were accompanied with marked changes in microbiota, which correlated with spatial memory retention performance. We next tested whether 2918-induced alterations in behavior and microbiome could be rescued by 5K52 diet for 3 months. Changing the 2918 diet to 5K52 diet mid-life improved spatial learning and memory in mice. Shotgun sequencing and principal component analyses revealed significant differences at both phylum and species levels. Multivariate analyses identified Akkermansia muciniphila or Bacteroidales bacterium M11 and Faecalibaculum rodentium as the strongest correlates to spatial memory retention in mice depending on the animal source. In both settings, the observed behavioral differences only affected hippocampal-dependent performance as mice fed with either diet did similarly well on the non-spatial variant of the Y-maze. In summary, these findings demonstrate the diverging effects of seemingly equivalent standard diets on hippocampal memory. Based on these results, we strongly recommend the mandatory inclusion of the diet and source of animals used in rodent behavioral studies.

Co-coding of head and whisker movements by both VPM and POm thalamic neurons

Rodents continuously move their heads and whiskers in a coordinated manner while perceiving objects through whisker-touch. Studies in head-fixed rodents showed that the ventroposterior medial (VPM) and posterior medial (POm) thalamic nuclei code for whisker kinematics, with POm involvement reduced in awake animals. To examine VPM and POm involvement in coding head and whisker kinematics in awake, head-free conditions, we recorded thalamic neuronal activity and tracked head and whisker movements in male mice exploring an open arena. Using optogenetic tagging, we found that in freely moving mice, both nuclei equally coded whisker kinematics and robustly coded head kinematics. The fraction of neurons coding head kinematics increased after whisker trimming, ruling out whisker-mediated coding. Optogenetic activation of thalamic neurons evoked overt kinematic changes and increased the fraction of neurons leading changes in head kinematics. Our data suggest that VPM and POm integrate head and whisker information and can influence head kinematics during tactile perception.

Transcriptome signatures of the medial prefrontal cortex underlying GABAergic control of resilience to chronic stress exposure.

Analyses of postmortem human brains and preclinical studies of rodents have identified somatostatin (SST)-positive interneurons as key elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, genetically induced disinhibition of SST neurons or brain region-specific chemogenetic activation of SST neurons in mice results in stress resilience. Here, we used RNA sequencing of mice with disinhibited SST neurons to characterize the transcriptome changes underlying GABAergic control of stress resilience. We found that stress resilience of male but not female mice with disinhibited SST neurons is characterized by resilience to chronic stress-induced transcriptome changes in the medial prefrontal cortex. Interestingly, the transcriptome of non-stressed stress-resilient male mice resembled the transcriptome of chronic stress-exposed stress-vulnerable mice. However, the behavior and the serum corticosterone levels of non-stressed stress-resilient mice showed no signs of physiological stress. Most strikingly, chronic stress exposure of stress-resilient mice was associated with an almost complete reversal of their chronic stress-like transcriptome signature, along with pathway changes indicating stress-induced enhancement of mRNA translation. Behaviorally, the mice with disinhibited SST neurons were not only resilient to chronic stress-induced anhedonia - they also showed an inversed anxiolytic-like response to chronic stress exposure that mirrored the chronic stress-induced reversal of the chronic stress-like transcriptome signature. We conclude that GABAergic dendritic inhibition by SST neurons exerts bidirectional control over behavioral vulnerability and resilience to chronic stress exposure that is mirrored in bidirectional changes in expression of putative stress resilience genes, through a sex-specific brain substrate.

The therapeutic potential of irisin to mitigate the risk of metabolic syndrome in postmenopausal women.

Oestradiol withdrawal at menopause predisposes women to metabolic syndrome, a cluster of interrelated conditions including obesity, insulin resistance, dyslipidaemia and hypertension that together confer an increased risk of developing type 2 diabetes mellitus and cardiovascular disease. Hormone replacement therapies are commonly used to treat acute symptoms of the perimenopausal period, and whilst they have been associated with metabolic improvements in many studies, long-term use is considered unviable. Novel approaches are required to mitigate the risk of postmenopausal metabolic syndrome. In 2012, the exercise-inducible myokine irisin was isolated from the skeletal muscle of mice and identified to have anti-obesity and antidiabetic effects in vivo. Irisin is now recognised to exert pleiotropic action on cognitive, bone and metabolic health. There is accumulating evidence from in vitro and in vivo rodent studies that irisin can mitigate each component condition of metabolic syndrome. In postmenopausal women, independent associations have been observed between (a) exercise and plasma irisin concentration and (b) plasma irisin concentration and reduced incidence of metabolic syndrome. To date, however, no study has considered the mechanistic basis by which irisin, whether exercise-induced or exogenously administered, could reduce the incidence or severity of metabolic syndrome in postmenopausal women. This review aims to analyse the literature concerning the metabolic actions of irisin, with a focus on its therapeutic potential for metabolic syndrome driven by a state of oestradiol depletion. It evaluates the practicality of exercise as a therapy and discusses other irisin-based therapeutic strategies that may alleviate postmenopausal metabolic syndrome. Finally, it highlights areas where future research is required to advance knowledge of irisin's biological action such that it could be considered a viable candidate for clinical application.

Anesthetic neurotoxicity in the developing brain: an update on theinsights and implications for fetal surgery.

This review describes an in-depth analysis of the neurotoxicity associated with the anesthetic agents used during fetal surgery, intending to highlight the importance of understanding the effects of general anesthetics on the developing brain, particularly in the context of open fetal surgery, where high doses are applied to facilitate surgical access and augment uterine relaxation. We examined evidence from preclinical studies in rodents and primates, along with studies in human subjects, with the results collectively suggesting that general anesthetics can disrupt brain development and lead to long-lasting neurological deficits. Our review underscores the clinical implications of these findings, indicating an association between extensive anesthetic exposure in early life and subsequent cognitive deficits. The current standard of anesthetic care for fetal surgical procedures was scrutinized, and recommendations have been proposed to mitigate the risk of anesthetic neurotoxicity. These recommendations emphasize the need for careful selection of anesthetic techniques to minimize fetal exposure to potentially harmful agents. In conclusion, while the benefits of fetal surgery in addressing immediate risks often outweigh the potential neurotoxic effects of anesthesia, the long-term developmental impacts nevertheless warrant consideration. Our analysis suggests that the use of general anesthetics in fetal surgery, especially at high doses, poses a significant risk of developmental neurotoxicity. As such, it is imperative to explore safer alternatives, such as employing different methods of uterine relaxation and minimizing the use of general anesthetics, to achieve the necessary surgical conditions. Further research, particularly in clinical settings, is essential to fully understand the risks and benefits of anesthetic techniques in fetal surgery.

P-133 Impaired blastocyst viability induced by vitrification during re-expansion after trophectoderm biopsy can be prevented by artificial shrinkage before vitrification

Abstract Study question Does the duration between trophectoderm biopsy and vitrification or blastocyst re-expansion affect blastocyst adhesion and outgrowth competence? Summary answer Outgrowth was impacted when blastocysts were vitrified during re-expansion, especially at 2 h post-biopsy; however, this can be mitigated using artificial shrinkage pre-vitrification. What is known already Biopsied blastocysts are usually vitrified until the results of preimplantation genetic testing for aneuploidy are available. The viability of biopsied blastocysts after vitrification is affected by various factors; in fact, a rodent study reported that the duration from biopsy to vitrification and re-expansion at vitrification affected subsequent developmental competence. The vitrification of biopsied blastocysts immediately post-biopsy is recommended in the clinical setting. However, in some cases, embryologists cannot perform vitrification immediately after a biopsy because of other procedures. In this case, blastocysts start re-expanding, which requires embryologists to wait for the completion of the blastocyst re-expansion. Study design, size, duration Human blastocysts donated for research by consenting couples were randomly allocated into biopsied (n = 175) and non-biopsied (control; n = 50) groups. The re-expansion degree (%) at vitrification was calculated using the following formula: [1- (distance of perivitelline cavity at vitrification)/(distance of perivitelline cavity post-biopsy)] × 100. The blastocysts were categorized according to expansion degree: I, ≤0%; II, 1–49%; III, 50–99%; and IV, ≥100%. Participants/materials, setting, methods Biopsied and control blastocysts were vitrified 0–3 h post-biopsy. Some blastocysts were artificially shrunken in hypertonic solution before the vitrification. The blastocysts were warmed and plated on fibronectin-coated dishes and cultured for 96 h to assess the competence for blastocyst adhesion and outgrowth. The correlations of outgrowth outcomes with vitrification timing, re-expansion degree, and artificial shrinkage were retrospectively analysed. Main results and the role of chance No significant intergroup difference was observed in blastocyst adhesion rate. The multivariate linear regression analysis showed that the blastocyst outgrowth area was significantly smaller when the blastocysts were vitrified at 2 h post-biopsy (P = 0.0103). Re-expansion degree was positively correlated with duration after biopsy (Spearman’s rank correlation coefficient, 0.6921; P &amp;lt; 0.0001). The proportion of expansion in group III was significantly higher at 2 h post-biopsy (P &amp;lt; 0.0001). On multivariate linear regression analysis, the blastocyst outgrowth area was significantly smaller in group III (P = 0.0134). The outgrowth area of blastocysts vitrified at 2 h post-biopsy was significantly increased by artificial shrinkage before vitrification (P = 0.0025) and comparable with those of blastocysts vitrified at 0, 1, and 3 h post-biopsy. Multivariate linear regression analysis also demonstrated the effectiveness of artificial shrinkage for blastocysts vitrified at 2 h post-biopsy and for blastocysts for which re-expansion was initiated at vitrification. Limitations, reasons for caution Since this study used discarded vitrified blastocysts, double vitrification was performed. This was an experimental study; therefore, clinical studies are required to validate our findings. Wider implications of the findings The blastocysts are recommended to be vitrified before the initiation of re-expansion, which complicates the laboratory workflow. Our data demonstrate that blastocysts that expand post-biopsy can be vitrified after artificial shrinkage without decreasing their implantation competence. Our findings may contribute to improving the day-to-day practice in embryology laboratories. Trial registration number Not Applicable

Discovery of BI-9508, a Brain-Penetrant GPR88-Receptor-Agonist Tool Compound for In Vivo Mouse Studies.

Decreased activity and expression of the G-protein coupled receptor GPR88 is linked to many behavior-linked neurological disorders. Published preclinical GPR88 allosteric agonists all have in vivo pharmacokinetic properties that preclude their progression to the clinic, including high lipophilicity and poor brain penetration. Here, we describe our attempts to improve GPR88 agonists' drug-like properties and our analysis of the trade-offs required to successfully target GPR88's allosteric pocket. We discovered two new GPR88 agonists: One that reduced morphine-induced locomotor activity in a murine proof-of-concept study, and the atropoisomeric BI-9508, which is a brain penetrant and has improved pharmacokinetic properties and dosing that recommend it for future in vivo studies in rodents. BI-9508 still suffers from high lipophilicity, and research on this series was halted. Because of its utility as a tool compound, we now offer researchers access to BI-9508 and a negative control free of charge via Boehringer Ingelheim's open innovation portal opnMe.com.

Update of the scientific opinion on tetrabromobisphenol A (TBBPA) and its derivatives in food.

The European Commission asked EFSA to update its 2011 risk assessment on tetrabromobisphenol A (TBBPA) and five derivatives in food. Neurotoxicity and carcinogenicity were considered as the critical effects of TBBPA in rodent studies. The available evidence indicates that the carcinogenicity of TBBPA occurs via non-genotoxic mechanisms. Taking into account the new data, the CONTAM Panel considered it appropriate to set a tolerable daily intake (TDI). Based on decreased interest in social interaction in male mice, a lowest observed adverse effect level (LOAEL) of 0.2 mg/kg body weight (bw) per day was identified and selected as the reference point for the risk characterisation. Applying the default uncertainty factor of 100 for inter- and intraspecies variability, and a factor of 3 to extrapolate from the LOAEL to NOAEL, a TDI for TBBPA of 0.7 μg/kg bw per day was established. Around 2100 analytical results for TBBPA in food were used to estimate dietary exposure for the European population. The most important contributors to the chronic dietary LB exposure to TBBPA were fish and seafood, meat and meat products and milk and dairy products. The exposure estimates to TBBPA were all below the TDI, including those estimated for breastfed and formula-fed infants. Accounting for the uncertainties affecting the assessment, the CONTAM Panel concluded with 90%-95% certainty that the current dietary exposure to TBBPA does not raise a health concern for any of the population groups considered. There were insufficient data on the toxicity of any of the TBBPA derivatives to derive reference points, or to allow a comparison with TBBPA that would support assignment to an assessment group for the purposes of combined risk assessment.

Altered desensitization and internalization patterns of rodent versus human glucose-dependent insulinotropic polypeptide (GIP) receptors. An important drug discovery challenge.

The gut hormone glucose-dependent insulinotropic polypeptide (GIP) signals via the GIP receptor (GIPR), resulting in postprandial potentiation of glucose-stimulated insulin secretion. The translation of results from rodent studies to human studies has been challenged by the unexpected effects of GIPR-targeting compounds. We, therefore, investigated the variation between species, focusing on GIPR desensitization and the role of the receptor C-terminus. The GIPR from humans, mice, rats, pigs, dogs and cats was studied in vitro for cognate ligand affinity, G protein activation (cAMP accumulation), recruitment of beta-arrestin and internalization. Variants of the mouse, rat and human GIPRs with swapped C-terminal tails were studied in parallel. The human GIPR is more prone to internalization than rodent GIPRs. Despite similar agonist affinities and potencies for Gαs activation, especially, the mouse GIPR shows reduced receptor desensitization, internalization and beta-arrestin recruitment. Using an enzyme-stabilized, long-acting GIP analogue, the species differences were even more pronounced. 'Tail-swapped' human, rat and mouse GIPRs were all fully functional in their Gαs coupling, and the mouse GIPR regained internalization and beta-arrestin 2 recruitment properties with the human tail. The human GIPR lost the ability to recruit beta-arrestin 2 when its own C-terminus was replaced by the rat or mouse tail. Desensitization of the human GIPR is dependent on the C-terminal tail. The species-dependent functionality of the C-terminal tail and the different species-dependent internalization patterns, especially between human and mouse GIPRs, are important factors influencing the preclinical evaluation of GIPR-targeting therapeutic compounds.

Is it the people or the place? The remarkable 30-year period of integrative physiology research in the Carlson Gymnasium at the University of Colorado Boulder.

Historically, programs of physical education and sport were housed in gymnasium buildings on academic campuses. As physical education evolved to the more scientifically focused successor departments of exercise science and kinesiology, faculty specialization developed in the physiology of exercise. With time, some faculty broadened their research to study the integrative physiology of other biological states and stressors. Through this series of events, a small group of integrative physiologists was formed in the Carlson Gymnasium at the University of Colorado Boulder during the 1990s with the goal of conducting novel biomedical research. The challenges were daunting: no contemporary core laboratory facilities, lack of temperature control, piercing external noise, pests, regular flooding, electrical power outages, and lack of funds for renovation. Despite these obstacles, the group established an innovative program of translational physiological research ranging from high-throughput molecular analyses to cell models to rodent studies to clinical trials in humans. These investigators supported their work with grant awards from the National Institutes of Health (NIH), Department of Defense, National Aeronautics and Space Administration (NASA), American Heart Association, and private research foundations totaling ∼$80 M in direct costs from the late 1980s to 2020. Collectively, the faculty and their laboratory personnel published ∼950 articles in peer-reviewed scientific journals. Over that period, 379 undergraduate students, 340 graduate students, 84 postdoctoral fellows, and dozens of junior research faculty received scientific training in Carlson, supported by >$21 M in extramural funding. What was accomplished by this handful of integrative physiologists speaks to the importance of the qualities of the investigators rather than their research facilities in determining scientific success.