Environmental Impoverishment, Aging, and Reduction in Mastication Affect Mouse Innate Repertoire to Explore Novel Environments and to Assess Risk

Studies indicate that inhibition of adequate masticatory function, due to soft diet, occlusal disharmony, or molar losses affects the cognitive behavior of rodents. However, no study has tested the effects on new environments exploration and risk assessment coupled with a combination of masticatory function rehabilitation and environmental enrichment. In the present report, we tested the hypothesis that age, environment, and masticatory changes may interact and alter exploratory patterns of locomotor activity and mice preferences in an open field (OF) arena. As OF arenas are widely used to measure anxiety-like behavior in rats and mice. We examined in an open arena, the exploratory and locomotor activities of mature (6-month-old; 6M), late mature (12-month-old; 12M), and aged (18-month-old; 18M) mice, subjected to distinct masticatory regimens and environments. Three different regimens of masticatory activity were used: continuous normal mastication with hard pellets (HD); normal mastication followed by reduced mastication with equal periods of pellets followed by soft powder – HD/SD; or rehabilitated masticatory activity with equal periods of HD, followed by powder, followed by pellets – HD/SD/HD). Under each diet regimen, half of the individuals were raised in standard cages [impoverished environment (IE)] and the other half in enriched cages [enriched environment (EE)]. Animals behavior on the open field (OF) task were recorded by webcam and analyzed with Any Maze software (Stöelting). The locomotor and exploratory activities in OF task declined with age, and this was particularly evident in 18M HD EE mice. Although all groups kept their preference by the peripheral zone, the outcomes were significantly influenced by interactions between environment, age, and diet. Independent of diet regime, 6M young mice maintained in an EE where voluntary exercise apparatus is available, revealed significant less body weight than all other groups. Although body weight differences were minimized as age progressed, 18M EE group revealed intragroup significant influence of diet regimens. We suggest that long life environmental enrichment reduces the tendency to avoid open/lit spaces (OF) and this is particularly influenced by masticatory activity. These measurements may be useful in discussions of anxiety-related tasks

Spatial memory decline after masticatory deprivation and aging is associated with altered laminar distribution of CA1 astrocytes

<p>Abstract</p> <p>Background</p> <p>Chewing imbalances are associated with neurodegeneration and are risk factors for senile dementia in humans and memory deficits in experimental animals. We investigated the impact of long-term reduced mastication on spatial memory in young, mature and aged female albino Swiss mice by stereological analysis of the laminar distribution of CA1 astrocytes. A soft diet (SD) was used to reduce mastication in the experimental group, whereas the control group was fed a hard diet (HD). Assays were performed in 3-, 6- and 18-month-old SD and HD mice.</p> <p>Results</p> <p>Eating a SD variably affected the number of astrocytes in the CA1 hippocampal field, and SD mice performed worse on water maze memory tests than HD mice. Three-month-old mice in both groups could remember/find a hidden platform in the water maze. However, 6-month-old SD mice, but not HD mice, exhibited significant spatial memory dysfunction. Both SD and HD 18-month-old mice showed spatial memory decline. Older SD mice had astrocyte hyperplasia in the strata pyramidale and oriens compared to 6-month-old mice. Aging induced astrocyte hypoplasia at 18 months in the lacunosum-moleculare layer of HD mice.</p> <p>Conclusions</p> <p>Taken together, these results suggest that the impaired spatial learning and memory induced by masticatory deprivation and aging may be associated with altered astrocyte laminar distribution and number in the CA1 hippocampal field. The underlying molecular mechanisms are unknown and merit further investigation.</p

Virus Infections on Prion Diseased Mice Exacerbate Inflammatory Microglial Response

We investigated possible interaction between an arbovirus infection and the ME7 induced mice prion disease. C57BL/6, females, 6-week-old, were submitted to a bilateral intrahippocampal injection of ME7 prion strain (ME7) or normal brain homogenate (NBH). After injections, animals were organized into two groups: NBH (n=26) and ME7 (n=29). At 15th week after injections (wpi), animals were challenged intranasally with a suspension of Piry arbovirus 0.001% or with NBH. Behavioral changes in ME7 animals appeared in burrowing activity at 14 wpi. Hyperactivity on open field test, errors on rod bridge, and time reduction in inverted screen were detected at 15th, 19th, and 20th wpi respectively. Burrowing was more sensitive to earlier hippocampus dysfunction. However, Piry-infection did not significantly affect the already ongoing burrowing decline in the ME7-treated mice. After behavioral tests, brains were processed for IBA1, protease-resistant form of PrP, and Piry virus antigens. Although virus infection in isolation did not change the number of microglia in CA1, virus infection in prion diseased mice (at 17th wpi) induced changes in number and morphology of microglia in a laminar-dependent way. We suggest that virus infection exacerbates microglial inflammatory response to a greater degree in prion-infected mice, and this is not necessarily correlated with hippocampal-dependent behavioral deficits

Sedentary life and reduced mastication impair spatial learning and memory and differentially affect dentate gyrus astrocyte subtypes in the aged mice

Brazilian Research Council CNPq (grant number 475677/2008-0) Fundação Amazônia Paraense de Amparo à Pesquisa (FAPESPA, grant number 136/08). Fundação de Amparo e Desenvolvimento da Pesquisa (FADESP) and the Pró-Reitoria de Pesquisa e Pós-Graduação (PROPESP/UFPA) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). Programa Nacional de Cooperação Acadêmica da Amazônia – DRI (Processo CAPES No. 88881.370785/2019-01). Fundação para a Ciência e a Tecnologia (PTDC/MED-NEU/31395/2017, LISBOA-01-0145-FEDER031395, and UID/DTP/04138/2018-2021), Santa Casa da Misericórdia (ALS Research Grant).Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil / Centro Universitário do Estado do Pará. Curso de Medicina. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil / Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Laboratório de Microscopia Eletrônica. Ananindeua, PA, Brasil.University of Oxford. Department of Pharmacology. Laboratory of Experimental Neuropathology. Oxford, United Kingdom.Universidade de Lisboa. Faculty of Pharmacy. Research Institute for Medicines. Lisbon, Portugal / Universidade de Lisboa. Faculty of Pharmacy. Department of Biochemistry and Human Biology. Lisbon, Portugal.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.To explore the impact of reduced mastication and a sedentary lifestyle on spatial learning and memory in the aged mice, as well as on the morphology of astrocytes in the molecular layer of dentate gyrus (MolDG), different masticatory regimens were imposed. Control mice received a pellet-type hard diet, while the reduced masticatory activity group received a pellet diet followed by a powdered diet, and the masticatory rehabilitation group received a pellet diet, followed by powder diet and then a pellet again. To mimic sedentary or active lifestyles, mice were housed in an impoverished environment of standard cages or in an enriched environment. The Morris Water Maze (MWM) test showed that masticatory-deprived group, regardless of environment, was not able to learn and remember the hidden platform location, but masticatory rehabilitation combined with enriched environment recovered such disabilities. Microscopic three-dimensional reconstructions of 1,800 glial fibrillary acidic protein (GFAP)-immunolabeled astrocytes from the external third of the MolDG were generated using a stereological systematic and random sampling approach. Hierarchical cluster analysis allowed the characterization into two main groups of astrocytes with greater and lower morphological complexities, respectively, AST1 and AST2. When compared to the hard diet group subjected to impoverished environment, deprived animals maintained in the same environment for 6 months showed remarkable shrinkage of astrocyte branches. However, the long-term environmental enrichment (18-monthold) applied to the deprived group reversed the shrinkage effect, with significant increase in the morphological complexity of AST1 and AST2, when in an impoverished or enriched environment. During housing under enriched environment, complexity of branches of AST1 and AST2 was reduced by the powder diet (pellet followed by powder regimes) in young but not in old mice, where it was reversed by pellet diet (pellet followed by powder and pellet regime again). The same was not true for mice housed under impoverished environment. Interestingly, we were unable to find any correlation between MWM data and astrocyte morphological changes. Our findings indicate that both young and aged mice subjected to environmental enrichment, and under normal or rehabilitated masticatory activity, preserve spatial learning and memory. Nonetheless, data suggest that an impoverished environment and reduced mastication synergize to aggravate age-related cognitive decline; however, the association with morphological diversity of AST1 and AST2 at the MolDG requires further investigation

Comparative analysis between Open Field and Elevated Plus Maze tests as a method for evaluating anxiety-like behavior in mice

Anxiety is being increasingly diagnosed in the elderly population. In this sense, epidemiologic data have linked late-life anxiety disorders to increased cognitive decline, morbidity, and even mortality. In addition, studies have already reported the influence of the environment on the association between aging and anxiety. Therefore, the present study aimed to conduct a comparative analysis between Elevated Plus Maze (EPM) and Open Field (OF) tests as methods for evaluating mice's anxiety-like behavior, considering environmental and age variables. For this, eighty Female albino Swiss mice aged 6, 12, and 18 months were housed in an impoverished environment (IE) and enriched environment (EE). Following this, the animals were tested in EPM and OF tests. The environment and age affect the anxiety-like behavior of the mice in the OF, with a difference between the animals of 6 and 18 months, only in the EE (p < 0.021). However, in the EPM, it does not occur. Despite that, the environment affected the distance traveled by the mice in the EPM, where the IE animals showed greater exploratory activity than the EE, only in the 18-month group (p < 0.001). No environmental influences were detected in the OF. Concerning age, in the EPM, animals in the 18-month-old group traveled shorter distances compared to the 6-month group (p < 0.001) and the 12-month group (p < 0.001), only in EE. In turn, in the OF there was a decrease in the distance traveled in the 18-month group compared to the 6-month group (p = 0.012), only in the IE. Thus, the divergences between the results of EPM and OF instigate a better evaluation of the parameters analyzed in each test

Morphometric, quantitative, and three-dimensional analysis of the heart muscle fibers of old rats: Transmission electron microscopy and high-resolution scanning electron microscopy methods

This research investigated the morphological, morphometric, and ultrastructural cardiomyocyte characteristics of male Wistar rats at 18 months of age. the animals were euthanized using an overdose of anesthesia (ketamine and xylazine, 150/10 mg/kg) and perfused transcardially, after which samples were collected for light microscopy, transmission electron microscopy, and high-resolution scanning electron microscopy. the results showed that cardiomyocyte arrangement was disposed parallel between the mitochondria and the A-, I-, and H-bands and their M- and Z-lines from the sarcomere. the sarcomere junction areas had intercalated disks, a specific structure of heart muscle. the ultrastructural analysis revealed several mitochondria of various sizes and shapes intermingled between the blood capillaries and their endothelial cells; some red cells inside vessels are noted. the muscle cell sarcolemma could be observed associated with the described structures. the cardiomyocytes of old rats presented an average sarcomere length of 2.071 +/- 0.09 mu m, a mitochondrial volume density (Vv) of 0.3383, a mitochondrial average area of 0.537 +/- 0.278 mu m2, a mitochondrial average length of 1.024 +/- 0.352 mu m, an average mitochondrial cristae thickness of 0.038 +/- 0.09 mu m and a ratio of mitochondrial greater length/lesser length of 1.929 +/- 0.965. of the observed mitochondrial shapes, 23.4% were rounded, 45.3% were elongated, and 31.1% had irregular profiles. in this study, we analyzed the morphology and morphometry of cardiomyocytes in old rats, focusing on mitochondria. These data are important for researchers who focus the changes in cardiac tissue, especially changes owing to pathologies and drug administration that may or may not be correlated with aging. Microsc. Res. Tech., 2013. (C) 2012 Wiley Periodicals, Inc.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The Faculty of Medicine, Fukuoka UniversityUniv São Paulo, Dept Surg, Fac Vet Med & Anim Sci, BR-05508900 São Paulo, BrazilUniv São Paulo, Dept Anat, Inst Biomed Sci, BR-05508900 São Paulo, BrazilFed Univ Para, Inst Biol Sci, Lab Invest Neurodegenerat & Infect, Univ Hosp Joao de Barros Barreto, BR-66059 Belem, Para, BrazilFukuoka Univ, Sch Med, Dept Anat, Fukuoka 81401, JapanUniversidade Federal de São Paulo, Dept Morphol & Genet, São Paulo, BrazilUniv São Paulo, Fac Dent, Dept Morphol Stomatol & Physiol, BR-14049 Ribeirao Preto, BrazilUniversidade Federal de São Paulo, Dept Morphol & Genet, São Paulo, BrazilWeb of Scienc

Idade, meio ambiente, reconhecimento de objetos e diversidade morfológica de astrocitos marcados com GFAP

Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil. / University of Oxford. Department of Pharmacology. Laboratory of Experimental Neuropathology. Oxford, England, UK.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil.Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil.University of Oxford. Department of Pharmacology. Laboratory of Experimental Neuropathology. Oxford, England, UK.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brasil. / University of Oxford. Department of Pharmacology. Laboratory of Experimental Neuropathology. Oxford, England, UK.Background: Few studies have explored the glial response to a standard environment and how the response may be associated with age-related cognitive decline in learning and memory. Here we investigated aging and environ mental influences on hippocampal-dependent tasks and on the morphology of an unbiased selected population of astrocytes from the molecular layer of dentate gyrus, which is the main target of perforant pathway. Results: Six and twenty-month-old female, albino Swiss mice were housed, from weaning, in a standard or enriched environment, including running wheels for exercise and tested for object recognition and contextual memories. Young adult and aged subjects, independent of environment, were able to distinguish familiar from novel objects. All experimental groups, except aged mice from standard environment, distinguish stationary from displaced objects. Young adult but not aged mice, independent of environment, were able to distinguish older from recent objects. Only young mice from an enriched environment were able to distinguish novel from familiar contexts. Unbiased selected astrocytes from the molecular layer of the dentate gyrus were reconstructed in three-dimensions and classified using hierarchical cluster analysis of bimodal or multimodal morphological features. We found two morphologi cal phenotypes of astrocytes and we designated type I the astrocytes that exhibited significantly higher values of morphological complexity as compared with type II. Complexity = [Sum of the terminal orders + Number of termi nals] × [Total branch length/Number of primary branches]. On average, type I morphological complexity seems to be much more sensitive to age and environmental influences than that of type II. Indeed, aging and environmental impoverishment interact and reduce the morphological complexity of type I astrocytes at a point that they could not be distinguished anymore from type II. Conclusions: We suggest these two types of astrocytes may have different physiological roles and that the det rimental effects of aging on memory in mice from a standard environment may be associated with a reduction of astrocytes morphological diversity

Lateral septum microglial changes and behavioral abnormalities of mice exposed to valproic acid during the prenatal period

Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil / Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Laboratório de Microscopia Eletrônica. Ananindeua, PA, Brasil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Universidade Federal do Pará. Instituto de Ciências Biológicas. Hospital Universitário João de Barros Barreto. Laboratório de Investigações em Neurodegeneração e Infecção. Belém, PA, Brazil.Most animal model studies of autism spectrum disorder (ASD) have been performed in males, which may be a reflex of the 3-times higher prevalence in boys than in girls. For this reason, little is known about the mechanisms underlying disease progression in females, and nothing is known about potential associations between microglial changes in the lateral septum (LS) and adult female cognition. Prenatal exposure to valproic acid (VPA) in mice has been widely used as an experimental model of autism-like behaviors associated with cellular changes. However, no study has reported the influence of VPA exposure in utero and its consequences on limbic system-dependent tasks or the microglial response in the LS in adult female mice. We compared the exploratory activity and risk assessment in novel environments of BALB/c control mice to mice exposed in utero to VPA and estimated the total number of microglia in the LS using an optical fractionator. On day 12.5 of pregnancy, females received diluted VPA or saline by gavage. After weaning, VPA exposed or control pups were separately housed in standard laboratory cages. At 5 months of age, all mice underwent behavioral testing and their brain sections were immunolabelled using IBA-1 antibody. In the open field test, VPA group showed a greater distance traveled, which was accompanied by less immobility, less time spent on the periphery and a greater number, crossed lines. Similar findings were found in the elevated plus maze test, where VPA mice traveled greater distances, immobility was significantly higher than that of control and VPA group spent less time on the closed arms of apparatus. Stereological analysis demonstrated higher microglial total number and density in the LS of VPA mice, as the cell count was greater, but the volume was similar. Therefore, we suggest that an increase in microglia in the LS may be part of the cellular changes associated with behavioral dysfunction in the VPA model of ASD